Down-integrate from internal code base.

255 files changed, 25099 insertions, 4893 deletions

diff --git a/Makefile.am b/Makefile.am
index 24e5e55c..4a29e1cf 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -79,6 +79,7 @@ EXTRA_DIST =                                                                 \
   java/src/main/java/com/google/protobuf/Descriptors.java                    \
   java/src/main/java/com/google/protobuf/DynamicMessage.java                 \
   java/src/main/java/com/google/protobuf/Extension.java                      \
+  java/src/main/java/com/google/protobuf/ExtensionLite.java                  \
   java/src/main/java/com/google/protobuf/ExtensionRegistry.java              \
   java/src/main/java/com/google/protobuf/ExtensionRegistryLite.java          \
   java/src/main/java/com/google/protobuf/FieldSet.java                       \
@@ -91,6 +92,10 @@ EXTRA_DIST =                                                                 \
   java/src/main/java/com/google/protobuf/LazyStringArrayList.java            \
   java/src/main/java/com/google/protobuf/LazyStringList.java                 \
   java/src/main/java/com/google/protobuf/LiteralByteString.java              \
+  java/src/main/java/com/google/protobuf/MapEntry.java                       \
+  java/src/main/java/com/google/protobuf/MapEntryLite.java                   \
+  java/src/main/java/com/google/protobuf/MapField.java                       \
+  java/src/main/java/com/google/protobuf/MapFieldLite.java                   \
   java/src/main/java/com/google/protobuf/Message.java                        \
   java/src/main/java/com/google/protobuf/MessageLite.java                    \
   java/src/main/java/com/google/protobuf/MessageLiteOrBuilder.java           \
@@ -112,6 +117,7 @@ EXTRA_DIST =                                                                 \
   java/src/main/java/com/google/protobuf/TextFormat.java                     \
   java/src/main/java/com/google/protobuf/UninitializedMessageException.java  \
   java/src/main/java/com/google/protobuf/UnknownFieldSet.java                \
+  java/src/main/java/com/google/protobuf/UnknownFieldSetLite.java            \
   java/src/main/java/com/google/protobuf/UnmodifiableLazyStringList.java     \
   java/src/main/java/com/google/protobuf/Utf8.java                           \
   java/src/main/java/com/google/protobuf/WireFormat.java                     \
@@ -124,18 +130,22 @@ EXTRA_DIST =                                                                 \
   java/src/test/java/com/google/protobuf/DeprecatedFieldTest.java            \
   java/src/test/java/com/google/protobuf/DescriptorsTest.java                \
   java/src/test/java/com/google/protobuf/DynamicMessageTest.java             \
+  java/src/test/java/com/google/protobuf/FieldPresenceTest.java              \
   java/src/test/java/com/google/protobuf/ForceFieldBuildersPreRun.java       \
   java/src/test/java/com/google/protobuf/GeneratedMessageTest.java           \
   java/src/test/java/com/google/protobuf/IsValidUtf8Test.java                \
   java/src/test/java/com/google/protobuf/IsValidUtf8TestUtil.java            \
-  java/src/test/java/com/google/protobuf/LazyFieldTest.java                  \
   java/src/test/java/com/google/protobuf/LazyFieldLiteTest.java              \
+  java/src/test/java/com/google/protobuf/LazyFieldTest.java                  \
   java/src/test/java/com/google/protobuf/LazyMessageLiteTest.java            \
   java/src/test/java/com/google/protobuf/LazyStringArrayListTest.java        \
   java/src/test/java/com/google/protobuf/LazyStringEndToEndTest.java         \
   java/src/test/java/com/google/protobuf/LiteEqualsAndHashTest.java          \
   java/src/test/java/com/google/protobuf/LiteralByteStringTest.java          \
   java/src/test/java/com/google/protobuf/LiteTest.java                       \
+  java/src/test/java/com/google/protobuf/MapForProto2LiteTest.java           \
+  java/src/test/java/com/google/protobuf/MapForProto2Test.java               \
+  java/src/test/java/com/google/protobuf/MapTest.java                        \
   java/src/test/java/com/google/protobuf/MessageTest.java                    \
   java/src/test/java/com/google/protobuf/NestedBuildersTest.java             \
   java/src/test/java/com/google/protobuf/ParserTest.java                     \
@@ -148,20 +158,25 @@ EXTRA_DIST =                                                                 \
   java/src/test/java/com/google/protobuf/TestBadIdentifiers.java             \
   java/src/test/java/com/google/protobuf/TestUtil.java                       \
   java/src/test/java/com/google/protobuf/TextFormatTest.java                 \
+  java/src/test/java/com/google/protobuf/UnknownEnumValueTest.java           \
+  java/src/test/java/com/google/protobuf/UnknownFieldSetLiteTest.java        \
   java/src/test/java/com/google/protobuf/UnknownFieldSetTest.java            \
   java/src/test/java/com/google/protobuf/UnmodifiableLazyStringListTest.java \
   java/src/test/java/com/google/protobuf/WireFormatTest.java                 \
+  java/src/test/java/com/google/protobuf/field_presence_test.proto           \
   java/src/test/java/com/google/protobuf/lazy_fields_lite.proto              \
   java/src/test/java/com/google/protobuf/lite_equals_and_hash.proto          \
+  java/src/test/java/com/google/protobuf/map_for_proto2_test.proto           \
+  java/src/test/java/com/google/protobuf/map_test.proto                      \
   java/src/test/java/com/google/protobuf/multiple_files_test.proto           \
   java/src/test/java/com/google/protobuf/nested_builders_test.proto          \
   java/src/test/java/com/google/protobuf/nested_extension_lite.proto         \
   java/src/test/java/com/google/protobuf/nested_extension.proto              \
   java/src/test/java/com/google/protobuf/non_nested_extension_lite.proto     \
   java/src/test/java/com/google/protobuf/non_nested_extension.proto          \
-  java/src/test/java/com/google/protobuf/outer_class_name_test.proto         \
   java/src/test/java/com/google/protobuf/outer_class_name_test2.proto        \
   java/src/test/java/com/google/protobuf/outer_class_name_test3.proto        \
+  java/src/test/java/com/google/protobuf/outer_class_name_test.proto         \
   java/src/test/java/com/google/protobuf/test_bad_identifiers.proto          \
   java/src/test/java/com/google/protobuf/test_check_utf8.proto               \
   java/src/test/java/com/google/protobuf/test_check_utf8_size.proto          \
@@ -194,6 +209,7 @@ EXTRA_DIST =                                                                 \
   python/google/protobuf/internal/more_extensions.proto                      \
   python/google/protobuf/internal/more_extensions_dynamic.proto              \
   python/google/protobuf/internal/more_messages.proto                        \
+  python/google/protobuf/internal/proto_builder_test.py                      \
   python/google/protobuf/internal/python_message.py                          \
   python/google/protobuf/internal/reflection_test.py                         \
   python/google/protobuf/internal/service_reflection_test.py                 \
@@ -207,6 +223,10 @@ EXTRA_DIST =                                                                 \
   python/google/protobuf/internal/wire_format.py                             \
   python/google/protobuf/internal/wire_format_test.py                        \
   python/google/protobuf/internal/__init__.py                                \
+  python/google/protobuf/internal/import_test_package/BUILD                  \
+  python/google/protobuf/internal/import_test_package/__init__.py            \
+  python/google/protobuf/internal/import_test_package/inner.proto            \
+  python/google/protobuf/internal/import_test_package/outer.proto            \
   python/google/protobuf/pyext/README                                        \
   python/google/protobuf/pyext/cpp_message.py                                \
   python/google/protobuf/pyext/descriptor.h                                  \
@@ -232,6 +252,7 @@ EXTRA_DIST =                                                                 \
   python/google/protobuf/descriptor_pool.py                                  \
   python/google/protobuf/message.py                                          \
   python/google/protobuf/message_factory.py                                  \
+  python/google/protobuf/proto_builder.py                                    \
   python/google/protobuf/reflection.py                                       \
   python/google/protobuf/service.py                                          \
   python/google/protobuf/service_reflection.py                               \
diff --git a/java/pom.xml b/java/pom.xml
index 1e3baa3c..a2bd1d1e 100644
--- a/java/pom.xml
+++ b/java/pom.xml
@@ -130,6 +130,10 @@
                   <arg value="../src/google/protobuf/unittest_lite_imports_nonlite.proto" />
                   <arg value="../src/google/protobuf/unittest_enormous_descriptor.proto" />
                   <arg value="../src/google/protobuf/unittest_no_generic_services.proto" />
+                  <arg value="src/test/java/com/google/protobuf/field_presence_test.proto" />
+                  <arg value="src/test/java/com/google/protobuf/map_for_proto2_lite_test.proto" />
+                  <arg value="src/test/java/com/google/protobuf/map_for_proto2_test.proto" />
+                  <arg value="src/test/java/com/google/protobuf/map_test.proto" />
                 </exec>
               </tasks>
               <testSourceRoot>target/generated-test-sources</testSourceRoot>
@@ -164,34 +168,37 @@
             <configuration>
               <includes>
                 <include>**/AbstractMessageLite.java</include>
+                <include>**/AbstractParser.java</include>
+                <include>**/BoundedByteString.java</include>
                 <include>**/ByteString.java</include>
                 <include>**/CodedInputStream.java</include>
                 <include>**/CodedOutputStream.java</include>
+                <include>**/ExtensionLite.java</include>
                 <include>**/ExtensionRegistryLite.java</include>
                 <include>**/FieldSet.java</include>
                 <include>**/GeneratedMessageLite.java</include>
                 <include>**/Internal.java</include>
                 <include>**/InvalidProtocolBufferException.java</include>
+                <include>**/LazyFieldLite.java</include>
                 <include>**/LazyStringArrayList.java</include>
                 <include>**/LazyStringList.java</include>
+                <include>**/LiteralByteString.java</include>
+                <include>**/MapEntryLite.java</include>
+                <include>**/MapFieldLite.java</include>
                 <include>**/MessageLite.java</include>
                 <include>**/MessageLiteOrBuilder.java</include>
+                <include>**/Parser.java</include>
+                <include>**/ProtocolStringList.java</include>
+                <include>**/RopeByteString.java</include>
                 <include>**/SmallSortedMap.java</include>
                 <include>**/UninitializedMessageException.java</include>
+                <include>**/UnknownFieldSetLite.java</include>
                 <include>**/UnmodifiableLazyStringList.java</include>
-                <include>**/WireFormat.java</include>
-                <include>**/Parser.java</include>
-                <include>**/AbstractParser.java</include>
-                <include>**/BoundedByteString.java</include>
-                <include>**/LiteralByteString.java</include>
-                <include>**/RopeByteString.java</include>
                 <include>**/Utf8.java</include>
-                <include>**/LazyField.java</include>
-                <include>**/LazyFieldLite.java</include>
-                <include>**/ProtocolStringList.java</include>
+                <include>**/WireFormat.java</include>
               </includes>
               <testIncludes>
-                <testInclude>**/LiteTest.java</testInclude>
+                <testInclude>**/**LiteTest.java</testInclude>
                 <testInclude>**/*Lite.java</testInclude>
               </testIncludes>
             </configuration>
@@ -200,7 +207,7 @@
             <artifactId>maven-surefire-plugin</artifactId>
             <configuration>
               <includes>
-                <include>**/LiteTest.java</include>
+                <include>**/**LiteTest.java</include>
               </includes>
             </configuration>
           </plugin>
diff --git a/java/src/main/java/com/google/protobuf/AbstractMessage.java b/java/src/main/java/com/google/protobuf/AbstractMessage.java
index ae9d5e39..6de4cae3 100644
--- a/java/src/main/java/com/google/protobuf/AbstractMessage.java
+++ b/java/src/main/java/com/google/protobuf/AbstractMessage.java
@@ -37,6 +37,9 @@ import com.google.protobuf.Internal.EnumLite;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 
@@ -144,6 +147,40 @@ public abstract class AbstractMessage extends AbstractMessageLite
   }
   
   /**
+   * Converts a list of MapEntry messages into a Map used for equals() and
+   * hashCode().
+   */
+  @SuppressWarnings({"rawtypes", "unchecked"})
+  private static Map convertMapEntryListToMap(List list) {
+    if (list.isEmpty()) {
+      return Collections.emptyMap();
+    }
+    Map result = new HashMap();
+    Iterator iterator = list.iterator();
+    Message entry = (Message) iterator.next();
+    Descriptors.Descriptor descriptor = entry.getDescriptorForType();
+    Descriptors.FieldDescriptor key = descriptor.findFieldByName("key");
+    Descriptors.FieldDescriptor value = descriptor.findFieldByName("value");
+    result.put(entry.getField(key), entry.getField(value));
+    while (iterator.hasNext()) {
+      entry = (Message) iterator.next();
+      result.put(entry.getField(key), entry.getField(value));
+    }
+    return result;
+  }
+  
+  /**
+   * Compares two map fields. The parameters must be a list of MapEntry
+   * messages.
+   */
+  @SuppressWarnings({"rawtypes", "unchecked"})
+  private static boolean compareMapField(Object a, Object b) {
+    Map ma = convertMapEntryListToMap((List) a);
+    Map mb = convertMapEntryListToMap((List) b);
+    return MapFieldLite.equals(ma, mb);
+  }
+  
+  /**
    * Compares two set of fields.
    * This method is used to implement {@link AbstractMessage#equals(Object)}
    * and {@link AbstractMutableMessage#equals(Object)}. It takes special care
@@ -181,6 +218,10 @@ public abstract class AbstractMessage extends AbstractMessageLite
             return false;
           }
         }
+      } else if (descriptor.isMapField()) {
+        if (!compareMapField(value1, value2)) {
+          return false;
+        }
       } else {
         // Compare non-bytes fields.
         if (!value1.equals(value2)) {
@@ -190,6 +231,15 @@ public abstract class AbstractMessage extends AbstractMessageLite
     }
     return true;
   }
+  
+  /**
+   * Calculates the hash code of a map field. {@code value} must be a list of
+   * MapEntry messages.
+   */
+  @SuppressWarnings("unchecked")
+  private static int hashMapField(Object value) {
+    return MapFieldLite.calculateHashCodeForMap(convertMapEntryListToMap((List) value));
+  }
 
   /** Get a hash code for given fields and values, using the given seed. */
   @SuppressWarnings("unchecked")
@@ -198,7 +248,9 @@ public abstract class AbstractMessage extends AbstractMessageLite
       FieldDescriptor field = entry.getKey();
       Object value = entry.getValue();
       hash = (37 * hash) + field.getNumber();
-      if (field.getType() != FieldDescriptor.Type.ENUM){
+      if (field.isMapField()) {
+        hash = (53 * hash) + hashMapField(value);
+      } else if (field.getType() != FieldDescriptor.Type.ENUM){
         hash = (53 * hash) + value.hashCode();
       } else if (field.isRepeated()) {
         List<? extends EnumLite> list = (List<? extends EnumLite>) value;
@@ -359,6 +411,12 @@ public abstract class AbstractMessage extends AbstractMessageLite
           "getFieldBuilder() called on an unsupported message type.");
     }
 
+    public Message.Builder getRepeatedFieldBuilder(final FieldDescriptor field,
+        int index) {
+      throw new UnsupportedOperationException(
+          "getRepeatedFieldBuilder() called on an unsupported message type.");
+    }
+
     public String toString() {
       return TextFormat.printToString(this);
     }
diff --git a/java/src/main/java/com/google/protobuf/CodedInputStream.java b/java/src/main/java/com/google/protobuf/CodedInputStream.java
index a00ae86f..0ca00bab 100644
--- a/java/src/main/java/com/google/protobuf/CodedInputStream.java
+++ b/java/src/main/java/com/google/protobuf/CodedInputStream.java
@@ -612,16 +612,16 @@ public final class CodedInputStream {
         return x;
       } else if (bufferSize - pos < 9) {
         break fastpath;
-      } else if ((x ^= (buffer[pos++] << 7)) < 0L) {
-        x ^= (~0L << 7);
-      } else if ((x ^= (buffer[pos++] << 14)) >= 0L) {
-        x ^= (~0L << 7) ^ (~0L << 14);
-      } else if ((x ^= (buffer[pos++] << 21)) < 0L) {
-        x ^= (~0L << 7) ^ (~0L << 14) ^ (~0L << 21);
+      } else if ((x ^= (buffer[pos++] << 7)) < 0) {
+        x ^= (~0 << 7);
+      } else if ((x ^= (buffer[pos++] << 14)) >= 0) {
+        x ^= (~0 << 7) ^ (~0 << 14);
+      } else if ((x ^= (buffer[pos++] << 21)) < 0) {
+        x ^= (~0 << 7) ^ (~0 << 14) ^ (~0 << 21);
       } else {
         int y = buffer[pos++];
         x ^= y << 28;
-        x ^= (~0L << 7) ^ (~0L << 14) ^ (~0L << 21) ^ (~0L << 28);
+        x ^= (~0 << 7) ^ (~0 << 14) ^ (~0 << 21) ^ (~0 << 28);
         if (y < 0 &&
             buffer[pos++] < 0 &&
             buffer[pos++] < 0 &&
@@ -739,13 +739,13 @@ public final class CodedInputStream {
         return y;
       } else if (bufferSize - pos < 9) {
         break fastpath;
-      } else if ((x = y ^ (buffer[pos++] << 7)) < 0L) {
-        x ^= (~0L << 7);
-      } else if ((x ^= (buffer[pos++] << 14)) >= 0L) {
-        x ^= (~0L << 7) ^ (~0L << 14);
-      } else if ((x ^= (buffer[pos++] << 21)) < 0L) {
-        x ^= (~0L << 7) ^ (~0L << 14) ^ (~0L << 21);
-      } else if ((x ^= ((long) buffer[pos++] << 28)) >= 0L) {
+      } else if ((y ^= (buffer[pos++] << 7)) < 0) {
+        x = y ^ (~0 << 7);
+      } else if ((y ^= (buffer[pos++] << 14)) >= 0) {
+        x = y ^ ((~0 << 7) ^ (~0 << 14));
+      } else if ((y ^= (buffer[pos++] << 21)) < 0) {
+        x = y ^ ((~0 << 7) ^ (~0 << 14) ^ (~0 << 21));
+      } else if ((x = ((long) y) ^ ((long) buffer[pos++] << 28)) >= 0L) {
         x ^= (~0L << 7) ^ (~0L << 14) ^ (~0L << 21) ^ (~0L << 28);
       } else if ((x ^= ((long) buffer[pos++] << 35)) < 0L) {
         x ^= (~0L << 7) ^ (~0L << 14) ^ (~0L << 21) ^ (~0L << 28) ^ (~0L << 35);
@@ -882,7 +882,7 @@ public final class CodedInputStream {
   /** See setSizeLimit() */
   private int sizeLimit = DEFAULT_SIZE_LIMIT;
 
-  private static final int DEFAULT_RECURSION_LIMIT = 64;
+  private static final int DEFAULT_RECURSION_LIMIT = 100;
   private static final int DEFAULT_SIZE_LIMIT = 64 << 20;  // 64MB
   private static final int BUFFER_SIZE = 4096;
 
diff --git a/java/src/main/java/com/google/protobuf/Descriptors.java b/java/src/main/java/com/google/protobuf/Descriptors.java
index caae0f77..d65e8b49 100644
--- a/java/src/main/java/com/google/protobuf/Descriptors.java
+++ b/java/src/main/java/com/google/protobuf/Descriptors.java
@@ -32,6 +32,7 @@ package com.google.protobuf;
 
 import com.google.protobuf.DescriptorProtos.*;
 
+import java.lang.ref.WeakReference;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -40,6 +41,7 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.WeakHashMap;
 import java.util.logging.Logger;
 import java.io.UnsupportedEncodingException;
 
@@ -123,6 +125,26 @@ public final class Descriptors {
       return Collections.unmodifiableList(Arrays.asList(publicDependencies));
     }
 
+    /** The syntax of the .proto file. */
+    public enum Syntax {
+      UNKNOWN("unknown"),
+      PROTO2("proto2"),
+      PROTO3("proto3");
+
+      Syntax(String name) {
+        this.name = name;
+      }
+      private final String name;
+    }
+
+    /** Get the syntax of the .proto file. */
+    public Syntax getSyntax() {
+      if (Syntax.PROTO3.name.equals(proto.getSyntax())) {
+        return Syntax.PROTO3;
+      }
+      return Syntax.PROTO2;
+    }
+
     /**
      * Find a message type in the file by name.  Does not find nested types.
      *
@@ -539,6 +561,10 @@ public final class Descriptors {
         extensions[i].setProto(proto.getExtension(i));
       }
     }
+    
+    boolean supportsUnknownEnumValue() {
+      return getSyntax() == Syntax.PROTO3;
+    }
   }
 
   // =================================================================
@@ -871,6 +897,11 @@ public final class Descriptors {
       return (type == Type.STRING) && (getFile().getOptions().getJavaStringCheckUtf8());
     }
 
+    boolean isMapField() {
+      return getType() == Type.MESSAGE && isRepeated()
+          && getMessageType().getOptions().getMapEntry();
+    }
+
     // I'm pretty sure values() constructs a new array every time, since there
     // is nothing stopping the caller from mutating the array.  Therefore we
     // make a static copy here.
@@ -1001,6 +1032,11 @@ public final class Descriptors {
       return getNumber() - other.getNumber();
     }
 
+    @Override
+    public String toString() {
+      return getFullName();
+    }
+
     private final int index;
 
     private FieldDescriptorProto proto;
@@ -1420,6 +1456,64 @@ public final class Descriptors {
       return file.pool.enumValuesByNumber.get(
         new DescriptorPool.DescriptorIntPair(this, number));
     }
+    
+    /**
+     * Get the enum value for a number. If no enum value has this number,
+     * construct an EnumValueDescriptor for it.
+     */
+    public EnumValueDescriptor findValueByNumberCreatingIfUnknown(final int number) {
+      EnumValueDescriptor result = findValueByNumber(number);
+      if (result != null) {
+        return result;
+      }
+      // The number represents an unknown enum value.
+      synchronized (this) {
+        // Descriptors are compared by object identity so for the same number
+        // we need to return the same EnumValueDescriptor object. This means
+        // we have to store created EnumValueDescriptors. However, as there
+        // are potentially 2G unknown enum values, storing all of these
+        // objects persistently will consume lots of memory for long-running
+        // services and it's also unnecessary as not many EnumValueDescriptors
+        // will be used at the same time.
+        //
+        // To solve the problem we take advantage of Java's weak references and
+        // rely on gc to release unused descriptors.
+        //
+        // Here is how it works:
+        //   * We store unknown EnumValueDescriptors in a WeakHashMap with the
+        //     value being a weak reference to the descriptor.
+        //   * The descriptor holds a strong reference to the key so as long
+        //     as the EnumValueDescriptor is in use, the key will be there
+        //     and the corresponding map entry will be there. Following-up
+        //     queries with the same number will return the same descriptor.
+        //   * If the user no longer uses an unknown EnumValueDescriptor,
+        //     it will be gc-ed since we only hold a weak reference to it in
+        //     the map. The key in the corresponding map entry will also be
+        //     gc-ed as the only strong reference to it is in the descriptor
+        //     which is just gc-ed. With the key being gone WeakHashMap will
+        //     then remove the whole entry. This way unknown descriptors will
+        //     be freed automatically and we don't need to do anything to
+        //     clean-up unused map entries.
+        
+        // Note: We must use "new Integer(number)" here because we don't want
+        // these Integer objects to be cached.
+        Integer key = new Integer(number);
+        WeakReference<EnumValueDescriptor> reference = unknownValues.get(key);
+        if (reference != null) {
+          result = reference.get();
+        }
+        if (result == null) {
+          result = new EnumValueDescriptor(file, this, key);
+          unknownValues.put(key, new WeakReference<EnumValueDescriptor>(result));
+        }
+      }
+      return result;
+    }
+    
+    // Used in tests only.
+    int getUnknownEnumValueDescriptorCount() {
+      return unknownValues.size();
+    }
 
     private final int index;
     private EnumDescriptorProto proto;
@@ -1427,6 +1521,8 @@ public final class Descriptors {
     private final FileDescriptor file;
     private final Descriptor containingType;
     private EnumValueDescriptor[] values;
+    private final WeakHashMap<Integer, WeakReference<EnumValueDescriptor>> unknownValues =
+        new WeakHashMap<Integer, WeakReference<EnumValueDescriptor>>();
 
     private EnumDescriptor(final EnumDescriptorProto proto,
                            final FileDescriptor file,
@@ -1531,6 +1627,25 @@ public final class Descriptors {
       file.pool.addSymbol(this);
       file.pool.addEnumValueByNumber(this);
     }
+    
+    private Integer number;
+    // Create an unknown enum value.
+    private EnumValueDescriptor(
+        final FileDescriptor file,
+        final EnumDescriptor parent,
+        final Integer number) {
+      String name = "UNKNOWN_ENUM_VALUE_" + parent.getName() + "_" + number;
+      EnumValueDescriptorProto proto = EnumValueDescriptorProto
+          .newBuilder().setName(name).setNumber(number).build();
+      this.index = -1;
+      this.proto = proto;
+      this.file = file;
+      this.type = parent;
+      this.fullName = parent.getFullName() + '.' + proto.getName();
+      this.number = number;
+      
+      // Don't add this descriptor into pool.
+    }
 
     /** See {@link FileDescriptor#setProto}. */
     private void setProto(final EnumValueDescriptorProto proto) {
diff --git a/java/src/main/java/com/google/protobuf/DynamicMessage.java b/java/src/main/java/com/google/protobuf/DynamicMessage.java
index c9ce667b..06b30fff 100644
--- a/java/src/main/java/com/google/protobuf/DynamicMessage.java
+++ b/java/src/main/java/com/google/protobuf/DynamicMessage.java
@@ -549,12 +549,22 @@ public final class DynamicMessage extends AbstractMessage {
     }
 
     public Builder setUnknownFields(UnknownFieldSet unknownFields) {
+      if (getDescriptorForType().getFile().getSyntax()
+          == Descriptors.FileDescriptor.Syntax.PROTO3) {
+        // Proto3 discards unknown fields.
+        return this;
+      }
       this.unknownFields = unknownFields;
       return this;
     }
 
     @Override
     public Builder mergeUnknownFields(UnknownFieldSet unknownFields) {
+      if (getDescriptorForType().getFile().getSyntax()
+          == Descriptors.FileDescriptor.Syntax.PROTO3) {
+        // Proto3 discards unknown fields.
+        return this;
+      }
       this.unknownFields =
         UnknownFieldSet.newBuilder(this.unknownFields)
                        .mergeFrom(unknownFields)
@@ -588,10 +598,12 @@ public final class DynamicMessage extends AbstractMessage {
         throw new IllegalArgumentException(
           "DynamicMessage should use EnumValueDescriptor to set Enum Value.");
       }
-      if (field.getEnumType() != ((EnumValueDescriptor) value).getType()) {
-        throw new IllegalArgumentException(
-          "EnumValueDescriptor doesn't much Enum Field.");
-      }
+      // TODO(xiaofeng): Re-enable this check after Orgstore is fixed to not
+      // set incorrect EnumValueDescriptors.
+      // if (field.getEnumType() != ((EnumValueDescriptor) value).getType()) {
+      //   throw new IllegalArgumentException(
+      //     "EnumValueDescriptor doesn't match Enum Field.");
+      // }
     }
 
     /** Verifies the value for an enum field. */
@@ -618,5 +630,12 @@ public final class DynamicMessage extends AbstractMessage {
       throw new UnsupportedOperationException(
         "getFieldBuilder() called on a dynamic message type.");
     }
+
+    @Override
+    public com.google.protobuf.Message.Builder getRepeatedFieldBuilder(FieldDescriptor field,
+        int index) {
+      throw new UnsupportedOperationException(
+        "getRepeatedFieldBuilder() called on a dynamic message type.");
+    }
   }
 }
diff --git a/java/src/main/java/com/google/protobuf/Extension.java b/java/src/main/java/com/google/protobuf/Extension.java
index 0baa22b3..68d29f33 100644
--- a/java/src/main/java/com/google/protobuf/Extension.java
+++ b/java/src/main/java/com/google/protobuf/Extension.java
@@ -35,27 +35,16 @@ package com.google.protobuf;
  *
  * @author liujisi@google.com (Jisi Liu)
  */
-public abstract class Extension<ContainingType extends MessageLite, Type> {
-  /** Returns the field number of the extension. */
-  public abstract int getNumber();
-
-  /** Returns the type of the field. */
-  public abstract WireFormat.FieldType getLiteType();
-
-  /** Returns whether it is a repeated field. */
-  public abstract boolean isRepeated();
+public abstract class Extension<ContainingType extends MessageLite, Type>
+    extends ExtensionLite<ContainingType, Type> {
 
   /** Returns the descriptor of the extension. */
   public abstract Descriptors.FieldDescriptor getDescriptor();
 
-  /** Returns the default value of the extension field. */
-  public abstract Type getDefaultValue();
-
-  /**
-   * Returns the default instance of the extension field, if it's a message
-   * extension.
-   */
-  public abstract MessageLite getMessageDefaultInstance();
+  /** Returns whether or not this extension is a Lite Extension. */
+  final boolean isLite() {
+    return false;
+  }
 
   // All the methods below are extension implementation details.
 
diff --git a/java/src/main/java/com/google/protobuf/ExtensionLite.java b/java/src/main/java/com/google/protobuf/ExtensionLite.java
new file mode 100644
index 00000000..f8f5bd2c
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/ExtensionLite.java
@@ -0,0 +1,63 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+/**
+ * Lite interface that generated extensions implement.
+ * <p>
+ * Methods are for use by generated code only. You can hold a reference to
+ * extensions using this type name.
+ */
+public abstract class ExtensionLite<ContainingType extends MessageLite, Type> {
+
+  /** Returns the field number of the extension. */
+  public abstract int getNumber();
+
+  /** Returns the type of the field. */
+  public abstract WireFormat.FieldType getLiteType();
+
+  /** Returns whether it is a repeated field. */
+  public abstract boolean isRepeated();
+
+  /** Returns the default value of the extension field. */
+  public abstract Type getDefaultValue();
+
+  /**
+   * Returns the default instance of the extension field, if it's a message
+   * extension.
+   */
+  public abstract MessageLite getMessageDefaultInstance();
+  
+  /** Returns whether or not this extension is a Lite Extension. */
+  boolean isLite() {
+    return true;
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/FieldSet.java b/java/src/main/java/com/google/protobuf/FieldSet.java
index 392f4efc..ff9b5bc0 100644
--- a/java/src/main/java/com/google/protobuf/FieldSet.java
+++ b/java/src/main/java/com/google/protobuf/FieldSet.java
@@ -672,7 +672,7 @@ final class FieldSet<FieldDescriptorType extends
    *               {@link Message#getField(Descriptors.FieldDescriptor)} for
    *               this field.
    */
-  private static void writeElementNoTag(
+  static void writeElementNoTag(
       final CodedOutputStream output,
       final WireFormat.FieldType type,
       final Object value) throws IOException {
@@ -830,7 +830,7 @@ final class FieldSet<FieldDescriptorType extends
    *               {@link Message#getField(Descriptors.FieldDescriptor)} for
    *               this field.
    */
-  private static int computeElementSizeNoTag(
+  static int computeElementSizeNoTag(
       final WireFormat.FieldType type, final Object value) {
     switch (type) {
       // Note:  Minor violation of 80-char limit rule here because this would
diff --git a/java/src/main/java/com/google/protobuf/GeneratedMessage.java b/java/src/main/java/com/google/protobuf/GeneratedMessage.java
index a6101cb0..156d1633 100644
--- a/java/src/main/java/com/google/protobuf/GeneratedMessage.java
+++ b/java/src/main/java/com/google/protobuf/GeneratedMessage.java
@@ -31,16 +31,20 @@
 package com.google.protobuf;
 
 import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.EnumDescriptor;
 import com.google.protobuf.Descriptors.EnumValueDescriptor;
 import com.google.protobuf.Descriptors.FieldDescriptor;
 import com.google.protobuf.Descriptors.FileDescriptor;
 import com.google.protobuf.Descriptors.OneofDescriptor;
+import com.google.protobuf.GeneratedMessageLite.ExtendableMessage;
+import com.google.protobuf.GeneratedMessageLite.GeneratedExtension;
 
 import java.io.IOException;
 import java.io.ObjectStreamException;
 import java.io.Serializable;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
+import java.lang.reflect.Type;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Iterator;
@@ -67,10 +71,15 @@ public abstract class GeneratedMessage extends AbstractMessage
    */
   protected static boolean alwaysUseFieldBuilders = false;
 
+  /** For use by generated code only.  */
+  protected UnknownFieldSet unknownFields;
+  
   protected GeneratedMessage() {
+    unknownFields = UnknownFieldSet.getDefaultInstance();
   }
 
   protected GeneratedMessage(Builder<?> builder) {
+    unknownFields = builder.getUnknownFields();
   }
 
   public Parser<? extends GeneratedMessage> getParserForType() {
@@ -291,13 +300,12 @@ public abstract class GeneratedMessage extends AbstractMessage
       return isClean;
     }
 
-    // This is implemented here only to work around an apparent bug in the
-    // Java compiler and/or build system.  See bug #1898463.  The mere presence
-    // of this dummy clone() implementation makes it go away.
     @Override
     public BuilderType clone() {
-      throw new UnsupportedOperationException(
-          "This is supposed to be overridden by subclasses.");
+      BuilderType builder =
+          (BuilderType) getDefaultInstanceForType().newBuilderForType();
+      builder.mergeFrom(buildPartial());
+      return builder;
     }
 
     /**
@@ -358,6 +366,13 @@ public abstract class GeneratedMessage extends AbstractMessage
     }
 
     //@Override (Java 1.6 override semantics, but we must support 1.5)
+    public Message.Builder getRepeatedFieldBuilder(final FieldDescriptor field,
+        int index) {
+      return internalGetFieldAccessorTable().getField(field).getRepeatedBuilder(
+          this, index);
+    }
+
+    //@Override (Java 1.6 override semantics, but we must support 1.5)
     public boolean hasOneof(final OneofDescriptor oneof) {
       return internalGetFieldAccessorTable().getOneof(oneof).has(this);
     }
@@ -428,7 +443,7 @@ public abstract class GeneratedMessage extends AbstractMessage
       return (BuilderType) this;
     }
 
-    public final BuilderType setUnknownFields(
+    public BuilderType setUnknownFields(
         final UnknownFieldSet unknownFields) {
       this.unknownFields = unknownFields;
       onChanged();
@@ -436,7 +451,7 @@ public abstract class GeneratedMessage extends AbstractMessage
     }
 
     @Override
-    public final BuilderType mergeUnknownFields(
+    public BuilderType mergeUnknownFields(
         final UnknownFieldSet unknownFields) {
       this.unknownFields =
         UnknownFieldSet.newBuilder(this.unknownFields)
@@ -529,6 +544,25 @@ public abstract class GeneratedMessage extends AbstractMessage
         isClean = false;
       }
     }
+
+    /**
+     * Gets the map field with the given field number. This method should be
+     * overridden in the generated message class if the message contains map
+     * fields.
+     * 
+     * Unlike other field types, reflection support for map fields can't be
+     * implemented based on generated public API because we need to access a
+     * map field as a list in reflection API but the generated API only allows
+     * us to access it as a map. This method returns the underlying map field
+     * directly and thus enables us to access the map field as a list. 
+     */
+    @SuppressWarnings({"unused", "rawtypes"})
+    protected MapField internalGetMapField(int fieldNumber) {
+      // Note that we can't use descriptor names here because this method will
+      // be called when descriptor is being initialized.
+      throw new RuntimeException(
+          "No map fields found in " + getClass().getName());
+    }
   }
 
   // =================================================================
@@ -541,19 +575,19 @@ public abstract class GeneratedMessage extends AbstractMessage
 
     /** Check if a singular extension is present. */
     <Type> boolean hasExtension(
-        Extension<MessageType, Type> extension);
+        ExtensionLite<MessageType, Type> extension);
 
     /** Get the number of elements in a repeated extension. */
     <Type> int getExtensionCount(
-        Extension<MessageType, List<Type>> extension);
+        ExtensionLite<MessageType, List<Type>> extension);
 
     /** Get the value of an extension. */
     <Type> Type getExtension(
-        Extension<MessageType, Type> extension);
+        ExtensionLite<MessageType, Type> extension);
 
     /** Get one element of a repeated extension. */
     <Type> Type getExtension(
-        Extension<MessageType, List<Type>> extension,
+        ExtensionLite<MessageType, List<Type>> extension,
         int index);
   }
 
@@ -625,7 +659,9 @@ public abstract class GeneratedMessage extends AbstractMessage
     /** Check if a singular extension is present. */
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     public final <Type> boolean hasExtension(
-        final Extension<MessageType, Type> extension) {
+        final ExtensionLite<MessageType, Type> extensionLite) {
+      Extension<MessageType, Type> extension = checkNotLite(extensionLite);
+
       verifyExtensionContainingType(extension);
       return extensions.hasField(extension.getDescriptor());
     }
@@ -633,7 +669,9 @@ public abstract class GeneratedMessage extends AbstractMessage
     /** Get the number of elements in a repeated extension. */
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     public final <Type> int getExtensionCount(
-        final Extension<MessageType, List<Type>> extension) {
+        final ExtensionLite<MessageType, List<Type>> extensionLite) {
+      Extension<MessageType, List<Type>> extension = checkNotLite(extensionLite);
+
       verifyExtensionContainingType(extension);
       final FieldDescriptor descriptor = extension.getDescriptor();
       return extensions.getRepeatedFieldCount(descriptor);
@@ -643,7 +681,9 @@ public abstract class GeneratedMessage extends AbstractMessage
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     @SuppressWarnings("unchecked")
     public final <Type> Type getExtension(
-        final Extension<MessageType, Type> extension) {
+        final ExtensionLite<MessageType, Type> extensionLite) {
+      Extension<MessageType, Type> extension = checkNotLite(extensionLite);
+      
       verifyExtensionContainingType(extension);
       FieldDescriptor descriptor = extension.getDescriptor();
       final Object value = extensions.getField(descriptor);
@@ -666,8 +706,10 @@ public abstract class GeneratedMessage extends AbstractMessage
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     @SuppressWarnings("unchecked")
     public final <Type> Type getExtension(
-        final Extension<MessageType, List<Type>> extension,
+        final ExtensionLite<MessageType, List<Type>> extensionLite,
         final int index) {
+      Extension<MessageType, List<Type>> extension = checkNotLite(extensionLite);
+
       verifyExtensionContainingType(extension);
       FieldDescriptor descriptor = extension.getDescriptor();
       return (Type) extension.singularFromReflectionType(
@@ -914,11 +956,10 @@ public abstract class GeneratedMessage extends AbstractMessage
 
     // This is implemented here only to work around an apparent bug in the
     // Java compiler and/or build system.  See bug #1898463.  The mere presence
-    // of this dummy clone() implementation makes it go away.
+    // of this clone() implementation makes it go away.
     @Override
     public BuilderType clone() {
-      throw new UnsupportedOperationException(
-          "This is supposed to be overridden by subclasses.");
+      return super.clone();
     }
 
     private void ensureExtensionsIsMutable() {
@@ -943,7 +984,9 @@ public abstract class GeneratedMessage extends AbstractMessage
     /** Check if a singular extension is present. */
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     public final <Type> boolean hasExtension(
-        final Extension<MessageType, Type> extension) {
+        final ExtensionLite<MessageType, Type> extensionLite) {
+      Extension<MessageType, Type> extension = checkNotLite(extensionLite);
+
       verifyExtensionContainingType(extension);
       return extensions.hasField(extension.getDescriptor());
     }
@@ -951,7 +994,9 @@ public abstract class GeneratedMessage extends AbstractMessage
     /** Get the number of elements in a repeated extension. */
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     public final <Type> int getExtensionCount(
-        final Extension<MessageType, List<Type>> extension) {
+        final ExtensionLite<MessageType, List<Type>> extensionLite) {
+      Extension<MessageType, List<Type>> extension = checkNotLite(extensionLite);
+
       verifyExtensionContainingType(extension);
       final FieldDescriptor descriptor = extension.getDescriptor();
       return extensions.getRepeatedFieldCount(descriptor);
@@ -960,7 +1005,9 @@ public abstract class GeneratedMessage extends AbstractMessage
     /** Get the value of an extension. */
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     public final <Type> Type getExtension(
-        final Extension<MessageType, Type> extension) {
+        final ExtensionLite<MessageType, Type> extensionLite) {
+      Extension<MessageType, Type> extension = checkNotLite(extensionLite);
+
       verifyExtensionContainingType(extension);
       FieldDescriptor descriptor = extension.getDescriptor();
       final Object value = extensions.getField(descriptor);
@@ -982,8 +1029,10 @@ public abstract class GeneratedMessage extends AbstractMessage
     /** Get one element of a repeated extension. */
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     public final <Type> Type getExtension(
-        final Extension<MessageType, List<Type>> extension,
+        final ExtensionLite<MessageType, List<Type>> extensionLite,
         final int index) {
+      Extension<MessageType, List<Type>> extension = checkNotLite(extensionLite);
+
       verifyExtensionContainingType(extension);
       FieldDescriptor descriptor = extension.getDescriptor();
       return (Type) extension.singularFromReflectionType(
@@ -992,8 +1041,10 @@ public abstract class GeneratedMessage extends AbstractMessage
 
     /** Set the value of an extension. */
     public final <Type> BuilderType setExtension(
-        final Extension<MessageType, Type> extension,
+        final ExtensionLite<MessageType, Type> extensionLite,
         final Type value) {
+      Extension<MessageType, Type> extension = checkNotLite(extensionLite);
+
       verifyExtensionContainingType(extension);
       ensureExtensionsIsMutable();
       final FieldDescriptor descriptor = extension.getDescriptor();
@@ -1004,8 +1055,10 @@ public abstract class GeneratedMessage extends AbstractMessage
 
     /** Set the value of one element of a repeated extension. */
     public final <Type> BuilderType setExtension(
-        final Extension<MessageType, List<Type>> extension,
+        final ExtensionLite<MessageType, List<Type>> extensionLite,
         final int index, final Type value) {
+      Extension<MessageType, List<Type>> extension = checkNotLite(extensionLite);
+
       verifyExtensionContainingType(extension);
       ensureExtensionsIsMutable();
       final FieldDescriptor descriptor = extension.getDescriptor();
@@ -1018,8 +1071,10 @@ public abstract class GeneratedMessage extends AbstractMessage
 
     /** Append a value to a repeated extension. */
     public final <Type> BuilderType addExtension(
-        final Extension<MessageType, List<Type>> extension,
+        final ExtensionLite<MessageType, List<Type>> extensionLite,
         final Type value) {
+      Extension<MessageType, List<Type>> extension = checkNotLite(extensionLite);
+
       verifyExtensionContainingType(extension);
       ensureExtensionsIsMutable();
       final FieldDescriptor descriptor = extension.getDescriptor();
@@ -1031,7 +1086,9 @@ public abstract class GeneratedMessage extends AbstractMessage
 
     /** Clear an extension. */
     public final <Type> BuilderType clearExtension(
-        final Extension<MessageType, ?> extension) {
+        final ExtensionLite<MessageType, ?> extensionLite) {
+      Extension<MessageType, ?> extension = checkNotLite(extensionLite);
+
       verifyExtensionContainingType(extension);
       ensureExtensionsIsMutable();
       extensions.clearField(extension.getDescriptor());
@@ -1594,6 +1651,25 @@ public abstract class GeneratedMessage extends AbstractMessage
       }
     }
   }
+  
+  /**
+   * Gets the map field with the given field number. This method should be
+   * overridden in the generated message class if the message contains map
+   * fields.
+   * 
+   * Unlike other field types, reflection support for map fields can't be
+   * implemented based on generated public API because we need to access a
+   * map field as a list in reflection API but the generated API only allows
+   * us to access it as a map. This method returns the underlying map field
+   * directly and thus enables us to access the map field as a list. 
+   */
+  @SuppressWarnings({"rawtypes", "unused"})
+  protected MapField internalGetMapField(int fieldNumber) {
+    // Note that we can't use descriptor names here because this method will
+    // be called when descriptor is being initialized.
+    throw new RuntimeException(
+        "No map fields found in " + getClass().getName());
+  }
 
   /**
    * Users should ignore this class.  This class provides the implementation
@@ -1633,6 +1709,11 @@ public abstract class GeneratedMessage extends AbstractMessage
       oneofs = new OneofAccessor[descriptor.getOneofs().size()];
       initialized = false;
     }
+    
+    private boolean isMapFieldEnabled(FieldDescriptor field) {
+      boolean result = true;
+      return result;
+    }
 
     /**
      * Ensures the field accessors are initialized. This method is thread-safe.
@@ -1657,8 +1738,13 @@ public abstract class GeneratedMessage extends AbstractMessage
           }
           if (field.isRepeated()) {
             if (field.getJavaType() == FieldDescriptor.JavaType.MESSAGE) {
-              fields[i] = new RepeatedMessageFieldAccessor(
-                  field, camelCaseNames[i], messageClass, builderClass);
+              if (field.isMapField() && isMapFieldEnabled(field)) {
+                fields[i] = new MapFieldAccessor(
+                    field, camelCaseNames[i], messageClass, builderClass);
+              } else {
+                fields[i] = new RepeatedMessageFieldAccessor(
+                    field, camelCaseNames[i], messageClass, builderClass);
+              }
             } else if (field.getJavaType() == FieldDescriptor.JavaType.ENUM) {
               fields[i] = new RepeatedEnumFieldAccessor(
                   field, camelCaseNames[i], messageClass, builderClass);
@@ -1744,6 +1830,8 @@ public abstract class GeneratedMessage extends AbstractMessage
       void clear(Builder builder);
       Message.Builder newBuilder();
       Message.Builder getBuilder(GeneratedMessage.Builder builder);
+      Message.Builder getRepeatedBuilder(GeneratedMessage.Builder builder,
+                                         int index);
     }
 
     /** OneofAccessor provides access to a single oneof. */
@@ -1799,9 +1887,9 @@ public abstract class GeneratedMessage extends AbstractMessage
         invokeOrDie(clearMethod, builder);
       }
     }
-    
+
     private static boolean supportFieldPresence(FileDescriptor file) {
-      return true;
+      return file.getSyntax() == FileDescriptor.Syntax.PROTO2;
     }
 
     // ---------------------------------------------------------------
@@ -1919,6 +2007,11 @@ public abstract class GeneratedMessage extends AbstractMessage
         throw new UnsupportedOperationException(
           "getFieldBuilder() called on a non-Message type.");
       }
+      public Message.Builder getRepeatedBuilder(GeneratedMessage.Builder builder,
+          int index) {
+        throw new UnsupportedOperationException(
+          "getRepeatedFieldBuilder() called on a non-Message type.");
+      }
     }
 
     private static class RepeatedFieldAccessor implements FieldAccessor {
@@ -2014,6 +2107,113 @@ public abstract class GeneratedMessage extends AbstractMessage
         throw new UnsupportedOperationException(
           "getFieldBuilder() called on a non-Message type.");
       }
+      public Message.Builder getRepeatedBuilder(GeneratedMessage.Builder builder,
+          int index) {
+        throw new UnsupportedOperationException(
+          "getRepeatedFieldBuilder() called on a non-Message type.");
+      }
+    }
+
+    private static class MapFieldAccessor implements FieldAccessor {
+      MapFieldAccessor(
+          final FieldDescriptor descriptor, final String camelCaseName,
+          final Class<? extends GeneratedMessage> messageClass,
+          final Class<? extends Builder> builderClass) {
+        field = descriptor;
+        Method getDefaultInstanceMethod =
+            getMethodOrDie(messageClass, "getDefaultInstance");
+        MapField defaultMapField = getMapField(
+            (GeneratedMessage) invokeOrDie(getDefaultInstanceMethod, null));
+        mapEntryMessageDefaultInstance =
+            defaultMapField.getMapEntryMessageDefaultInstance();
+      }
+
+      private final FieldDescriptor field;
+      private final Message mapEntryMessageDefaultInstance;
+      
+      private MapField<?, ?> getMapField(GeneratedMessage message) {
+        return (MapField<?, ?>) message.internalGetMapField(field.getNumber());
+      }
+      
+      private MapField<?, ?> getMapField(GeneratedMessage.Builder builder) {
+        return (MapField<?, ?>) builder.internalGetMapField(field.getNumber());
+      }
+      
+      public Object get(GeneratedMessage message) {
+        List result = new ArrayList();
+        for (int i = 0; i < getRepeatedCount(message); i++) {
+          result.add(getRepeated(message, i));
+        }
+        return Collections.unmodifiableList(result);
+      }
+
+      public Object get(Builder builder) {
+        List result = new ArrayList();
+        for (int i = 0; i < getRepeatedCount(builder); i++) {
+          result.add(getRepeated(builder, i));
+        }
+        return Collections.unmodifiableList(result);
+      }
+
+      public void set(Builder builder, Object value) {
+        clear(builder);
+        for (Object entry : (List) value) {
+          addRepeated(builder, entry);
+        }
+      }
+
+      public Object getRepeated(GeneratedMessage message, int index) {
+        return getMapField(message).getList().get(index);
+      }
+
+      public Object getRepeated(Builder builder, int index) {
+        return getMapField(builder).getList().get(index);
+      }
+
+      public void setRepeated(Builder builder, int index, Object value) {
+        getMapField(builder).getMutableList().set(index, (Message) value);
+      }
+
+      public void addRepeated(Builder builder, Object value) {
+        getMapField(builder).getMutableList().add((Message) value);
+      }
+
+      public boolean has(GeneratedMessage message) {
+        throw new UnsupportedOperationException(
+            "hasField() is not supported for repeated fields.");
+      }
+
+      public boolean has(Builder builder) {
+        throw new UnsupportedOperationException(
+            "hasField() is not supported for repeated fields.");
+      }
+
+      public int getRepeatedCount(GeneratedMessage message) {
+        return getMapField(message).getList().size();
+      }
+
+      public int getRepeatedCount(Builder builder) {
+        return getMapField(builder).getList().size();
+      }
+
+      public void clear(Builder builder) {
+        getMapField(builder).getMutableList().clear();
+      }
+
+      public com.google.protobuf.Message.Builder newBuilder() {
+        return mapEntryMessageDefaultInstance.newBuilderForType();
+      }
+
+      public com.google.protobuf.Message.Builder getBuilder(Builder builder) {
+        throw new UnsupportedOperationException(
+            "Nested builder not supported for map fields.");
+      }
+      
+      public com.google.protobuf.Message.Builder getRepeatedBuilder(
+          Builder builder, int index) {
+        throw new UnsupportedOperationException(
+            "Nested builder not supported for map fields.");
+      }
     }
 
     // ---------------------------------------------------------------
@@ -2026,28 +2226,60 @@ public abstract class GeneratedMessage extends AbstractMessage
           final Class<? extends Builder> builderClass,
           final String containingOneofCamelCaseName) {
         super(descriptor, camelCaseName, messageClass, builderClass, containingOneofCamelCaseName);
+        
+        enumDescriptor = descriptor.getEnumType();
 
         valueOfMethod = getMethodOrDie(type, "valueOf",
                                        EnumValueDescriptor.class);
         getValueDescriptorMethod =
           getMethodOrDie(type, "getValueDescriptor");
+
+        supportUnknownEnumValue = descriptor.getFile().supportsUnknownEnumValue();
+        if (supportUnknownEnumValue) {
+          getValueMethod =
+              getMethodOrDie(messageClass, "get" + camelCaseName + "Value");
+          getValueMethodBuilder =
+              getMethodOrDie(builderClass, "get" + camelCaseName + "Value");
+          setValueMethod =
+              getMethodOrDie(builderClass, "set" + camelCaseName + "Value", int.class);
+        }
       }
+      
+      private EnumDescriptor enumDescriptor;
 
       private Method valueOfMethod;
       private Method getValueDescriptorMethod;
+      
+      private boolean supportUnknownEnumValue;
+      private Method getValueMethod;
+      private Method getValueMethodBuilder;
+      private Method setValueMethod;
 
       @Override
       public Object get(final GeneratedMessage message) {
+        if (supportUnknownEnumValue) {
+          int value = (Integer) invokeOrDie(getValueMethod, message);
+          return enumDescriptor.findValueByNumberCreatingIfUnknown(value);
+        }
         return invokeOrDie(getValueDescriptorMethod, super.get(message));
       }
 
       @Override
       public Object get(final GeneratedMessage.Builder builder) {
+        if (supportUnknownEnumValue) {
+          int value = (Integer) invokeOrDie(getValueMethodBuilder, builder);
+          return enumDescriptor.findValueByNumberCreatingIfUnknown(value);
+        }
         return invokeOrDie(getValueDescriptorMethod, super.get(builder));
       }
 
       @Override
       public void set(final Builder builder, final Object value) {
+        if (supportUnknownEnumValue) {
+          invokeOrDie(setValueMethod, builder,
+              ((EnumValueDescriptor) value).getNumber());
+          return;
+        }
         super.set(builder, invokeOrDie(valueOfMethod, null, value));
       }
     }
@@ -2059,22 +2291,44 @@ public abstract class GeneratedMessage extends AbstractMessage
           final Class<? extends GeneratedMessage> messageClass,
           final Class<? extends Builder> builderClass) {
         super(descriptor, camelCaseName, messageClass, builderClass);
+        
+        enumDescriptor = descriptor.getEnumType();
 
         valueOfMethod = getMethodOrDie(type, "valueOf",
                                        EnumValueDescriptor.class);
         getValueDescriptorMethod =
           getMethodOrDie(type, "getValueDescriptor");
+
+        supportUnknownEnumValue = descriptor.getFile().supportsUnknownEnumValue();
+        if (supportUnknownEnumValue) {
+          getRepeatedValueMethod =
+              getMethodOrDie(messageClass, "get" + camelCaseName + "Value", int.class);
+          getRepeatedValueMethodBuilder =
+              getMethodOrDie(builderClass, "get" + camelCaseName + "Value", int.class);
+          setRepeatedValueMethod =
+              getMethodOrDie(builderClass, "set" + camelCaseName + "Value", int.class, int.class);
+          addRepeatedValueMethod =
+              getMethodOrDie(builderClass, "add" + camelCaseName + "Value", int.class);
+        }
       }
+      private EnumDescriptor enumDescriptor;
 
       private final Method valueOfMethod;
       private final Method getValueDescriptorMethod;
+      
+      private boolean supportUnknownEnumValue;
+      private Method getRepeatedValueMethod;
+      private Method getRepeatedValueMethodBuilder;
+      private Method setRepeatedValueMethod;
+      private Method addRepeatedValueMethod;
 
       @Override
       @SuppressWarnings("unchecked")
       public Object get(final GeneratedMessage message) {
         final List newList = new ArrayList();
-        for (final Object element : (List) super.get(message)) {
-          newList.add(invokeOrDie(getValueDescriptorMethod, element));
+        final int size = getRepeatedCount(message);
+        for (int i = 0; i < size; i++) {
+          newList.add(getRepeated(message, i));
         }
         return Collections.unmodifiableList(newList);
       }
@@ -2083,8 +2337,9 @@ public abstract class GeneratedMessage extends AbstractMessage
       @SuppressWarnings("unchecked")
       public Object get(final GeneratedMessage.Builder builder) {
         final List newList = new ArrayList();
-        for (final Object element : (List) super.get(builder)) {
-          newList.add(invokeOrDie(getValueDescriptorMethod, element));
+        final int size = getRepeatedCount(builder);
+        for (int i = 0; i < size; i++) {
+          newList.add(getRepeated(builder, i));
         }
         return Collections.unmodifiableList(newList);
       }
@@ -2092,23 +2347,41 @@ public abstract class GeneratedMessage extends AbstractMessage
       @Override
       public Object getRepeated(final GeneratedMessage message,
                                 final int index) {
+        if (supportUnknownEnumValue) {
+          int value = (Integer) invokeOrDie(getRepeatedValueMethod, message, index);
+          return enumDescriptor.findValueByNumberCreatingIfUnknown(value);
+        }
         return invokeOrDie(getValueDescriptorMethod,
           super.getRepeated(message, index));
       }
       @Override
       public Object getRepeated(final GeneratedMessage.Builder builder,
                                 final int index) {
+        if (supportUnknownEnumValue) {
+          int value = (Integer) invokeOrDie(getRepeatedValueMethodBuilder, builder, index);
+          return enumDescriptor.findValueByNumberCreatingIfUnknown(value);
+        }
         return invokeOrDie(getValueDescriptorMethod,
           super.getRepeated(builder, index));
       }
       @Override
       public void setRepeated(final Builder builder,
                               final int index, final Object value) {
+        if (supportUnknownEnumValue) {
+          invokeOrDie(setRepeatedValueMethod, builder, index,
+              ((EnumValueDescriptor) value).getNumber());
+          return;
+        }
         super.setRepeated(builder, index, invokeOrDie(valueOfMethod, null,
                           value));
       }
       @Override
       public void addRepeated(final Builder builder, final Object value) {
+        if (supportUnknownEnumValue) {
+          invokeOrDie(addRepeatedValueMethod, builder,
+              ((EnumValueDescriptor) value).getNumber());
+          return;
+        }
         super.addRepeated(builder, invokeOrDie(valueOfMethod, null, value));
       }
     }
@@ -2168,9 +2441,12 @@ public abstract class GeneratedMessage extends AbstractMessage
         super(descriptor, camelCaseName, messageClass, builderClass);
 
         newBuilderMethod = getMethodOrDie(type, "newBuilder");
+        getBuilderMethodBuilder = getMethodOrDie(builderClass,
+            "get" + camelCaseName + "Builder", Integer.TYPE);
       }
 
       private final Method newBuilderMethod;
+      private final Method getBuilderMethodBuilder;
 
       private Object coerceType(final Object value) {
         if (type.isInstance(value)) {
@@ -2198,6 +2474,12 @@ public abstract class GeneratedMessage extends AbstractMessage
       public Message.Builder newBuilder() {
         return (Message.Builder) invokeOrDie(newBuilderMethod, null);
       }
+      @Override
+      public Message.Builder getRepeatedBuilder(
+          final GeneratedMessage.Builder builder, final int index) {
+        return (Message.Builder) invokeOrDie(
+            getBuilderMethodBuilder, builder, index);
+      }
     }
   }
 
@@ -2210,4 +2492,18 @@ public abstract class GeneratedMessage extends AbstractMessage
   protected Object writeReplace() throws ObjectStreamException {
     return new GeneratedMessageLite.SerializedForm(this);
   }
+  
+  /**
+   * Checks that the {@link Extension} is non-Lite and returns it as a
+   * {@link GeneratedExtension}.
+   */
+  private static <MessageType extends ExtendableMessage<MessageType>, T>
+    Extension<MessageType, T> checkNotLite(
+        ExtensionLite<MessageType, T> extension) {
+    if (extension.isLite()) {
+      throw new IllegalArgumentException("Expected non-lite extension.");
+    }
+    
+    return (Extension<MessageType, T>) extension;
+  }
 }
diff --git a/java/src/main/java/com/google/protobuf/GeneratedMessageLite.java b/java/src/main/java/com/google/protobuf/GeneratedMessageLite.java
index 6c5136fd..8fe33bc6 100644
--- a/java/src/main/java/com/google/protobuf/GeneratedMessageLite.java
+++ b/java/src/main/java/com/google/protobuf/GeneratedMessageLite.java
@@ -30,6 +30,8 @@
 
 package com.google.protobuf;
 
+import com.google.protobuf.WireFormat.FieldType;
+
 import java.io.IOException;
 import java.io.ObjectStreamException;
 import java.io.Serializable;
@@ -50,10 +52,15 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
     implements Serializable {
   private static final long serialVersionUID = 1L;
 
+  /** For use by generated code only.  */
+  protected UnknownFieldSetLite unknownFields;
+  
   protected GeneratedMessageLite() {
+    unknownFields = UnknownFieldSetLite.getDefaultInstance();
   }
 
   protected GeneratedMessageLite(Builder builder) {
+    unknownFields = builder.unknownFields;
   }
 
   public Parser<? extends MessageLite> getParserForType() {
@@ -62,15 +69,16 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
   }
 
   /**
-   * Called by subclasses to parse an unknown field.
+   * Called by subclasses to parse an unknown field. For use by generated code
+   * only.
    * @return {@code true} unless the tag is an end-group tag.
    */
-  protected boolean parseUnknownField(
+  protected static boolean parseUnknownField(
       CodedInputStream input,
-      CodedOutputStream unknownFieldsCodedOutput,
+      UnknownFieldSetLite.Builder unknownFields,
       ExtensionRegistryLite extensionRegistry,
       int tag) throws IOException {
-    return input.skipField(tag, unknownFieldsCodedOutput);
+    return unknownFields.mergeFieldFrom(tag, input);
   }
 
   /**
@@ -84,22 +92,28 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
   public abstract static class Builder<MessageType extends GeneratedMessageLite,
                                        BuilderType extends Builder>
       extends AbstractMessageLite.Builder<BuilderType> {
+
+    private UnknownFieldSetLite unknownFields =
+        UnknownFieldSetLite.getDefaultInstance();
+
     protected Builder() {}
 
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     public BuilderType clear() {
-      unknownFields = ByteString.EMPTY;
+      unknownFields = UnknownFieldSetLite.getDefaultInstance();
       return (BuilderType) this;
     }
 
-    // This is implemented here only to work around an apparent bug in the
-    // Java compiler and/or build system.  See bug #1898463.  The mere presence
-    // of this dummy clone() implementation makes it go away.
-    @Override
+    //@Override (Java 1.6 override semantics, but we must support 1.5)
     public BuilderType clone() {
-      throw new UnsupportedOperationException(
-          "This is supposed to be overridden by subclasses.");
+      BuilderType builder =
+          (BuilderType) getDefaultInstanceForType().newBuilderForType();
+      builder.mergeFrom(buildPartial());
+      return builder;
     }
+    
+    /** All subclasses implement this. */
+    public abstract MessageType buildPartial();
 
     /** All subclasses implement this. */
     public abstract BuilderType mergeFrom(MessageType message);
@@ -113,22 +127,43 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
      */
     protected boolean parseUnknownField(
         CodedInputStream input,
-        CodedOutputStream unknownFieldsCodedOutput,
+        UnknownFieldSetLite.Builder unknownFields,
         ExtensionRegistryLite extensionRegistry,
         int tag) throws IOException {
-      return input.skipField(tag, unknownFieldsCodedOutput);
+      return unknownFields.mergeFieldFrom(tag, input);
     }
 
-    public final ByteString getUnknownFields() {
-      return unknownFields;
+    /**
+     * Merge some unknown fields into the {@link UnknownFieldSetLite} for this
+     * message.
+     *
+     * <p>For use by generated code only.
+     */
+    protected final BuilderType mergeUnknownFields(
+        final UnknownFieldSetLite unknownFields) {
+      this.unknownFields = UnknownFieldSetLite.concat(this.unknownFields, unknownFields);
+      return (BuilderType) this;
     }
-
-    public final BuilderType setUnknownFields(final ByteString unknownFields) {
-      this.unknownFields = unknownFields;
+    
+    public BuilderType mergeFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      MessageType parsedMessage = null;
+      try {
+        parsedMessage =
+            (MessageType) getDefaultInstanceForType().getParserForType().parsePartialFrom(
+                input, extensionRegistry);
+      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+        parsedMessage = (MessageType) e.getUnfinishedMessage();
+        throw e;
+      } finally {
+        if (parsedMessage != null) {
+          mergeFrom(parsedMessage);
+        }
+      }
       return (BuilderType) this;
     }
-
-    private ByteString unknownFields = ByteString.EMPTY;
   }
 
 
@@ -143,18 +178,18 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
 
     /** Check if a singular extension is present. */
     <Type> boolean hasExtension(
-        GeneratedExtension<MessageType, Type> extension);
+        ExtensionLite<MessageType, Type> extension);
 
     /** Get the number of elements in a repeated extension. */
     <Type> int getExtensionCount(
-        GeneratedExtension<MessageType, List<Type>> extension);
+        ExtensionLite<MessageType, List<Type>> extension);
 
     /** Get the value of an extension. */
-    <Type> Type getExtension(GeneratedExtension<MessageType, Type> extension);
+    <Type> Type getExtension(ExtensionLite<MessageType, Type> extension);
 
     /** Get one element of a repeated extension. */
     <Type> Type getExtension(
-        GeneratedExtension<MessageType, List<Type>> extension,
+        ExtensionLite<MessageType, List<Type>> extension,
         int index);
   }
 
@@ -166,7 +201,11 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
       extends GeneratedMessageLite
       implements ExtendableMessageOrBuilder<MessageType> {
 
-    private final FieldSet<ExtensionDescriptor> extensions;
+    /**
+     * Represents the set of extensions on this message. For use by generated
+     * code only.
+     */
+    protected final FieldSet<ExtensionDescriptor> extensions;
 
     protected ExtendableMessage() {
       this.extensions = FieldSet.newFieldSet();
@@ -190,30 +229,39 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
     /** Check if a singular extension is present. */
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     public final <Type> boolean hasExtension(
-        final GeneratedExtension<MessageType, Type> extension) {
-      verifyExtensionContainingType(extension);
-      return extensions.hasField(extension.descriptor);
+        final ExtensionLite<MessageType, Type> extension) {
+      GeneratedExtension<MessageType, Type> extensionLite =
+          checkIsLite(extension);
+      
+      verifyExtensionContainingType(extensionLite);
+      return extensions.hasField(extensionLite.descriptor);
     }
 
     /** Get the number of elements in a repeated extension. */
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     public final <Type> int getExtensionCount(
-        final GeneratedExtension<MessageType, List<Type>> extension) {
-      verifyExtensionContainingType(extension);
-      return extensions.getRepeatedFieldCount(extension.descriptor);
+        final ExtensionLite<MessageType, List<Type>> extension) {
+      GeneratedExtension<MessageType, List<Type>> extensionLite =
+          checkIsLite(extension);
+      
+      verifyExtensionContainingType(extensionLite);
+      return extensions.getRepeatedFieldCount(extensionLite.descriptor);
     }
 
     /** Get the value of an extension. */
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     @SuppressWarnings("unchecked")
     public final <Type> Type getExtension(
-        final GeneratedExtension<MessageType, Type> extension) {
-      verifyExtensionContainingType(extension);
-      final Object value = extensions.getField(extension.descriptor);
+        final ExtensionLite<MessageType, Type> extension) {
+      GeneratedExtension<MessageType, Type> extensionLite =
+          checkIsLite(extension);
+      
+      verifyExtensionContainingType(extensionLite);
+      final Object value = extensions.getField(extensionLite.descriptor);
       if (value == null) {
-        return extension.defaultValue;
+        return extensionLite.defaultValue;
       } else {
-        return (Type) extension.fromFieldSetType(value);
+        return (Type) extensionLite.fromFieldSetType(value);
       }
     }
 
@@ -221,11 +269,14 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     @SuppressWarnings("unchecked")
     public final <Type> Type getExtension(
-        final GeneratedExtension<MessageType, List<Type>> extension,
+        final ExtensionLite<MessageType, List<Type>> extension,
         final int index) {
-      verifyExtensionContainingType(extension);
-      return (Type) extension.singularFromFieldSetType(
-          extensions.getRepeatedField(extension.descriptor, index));
+      GeneratedExtension<MessageType, List<Type>> extensionLite =
+          checkIsLite(extension);
+
+      verifyExtensionContainingType(extensionLite);
+      return (Type) extensionLite.singularFromFieldSetType(
+          extensions.getRepeatedField(extensionLite.descriptor, index));
     }
 
     /** Called by subclasses to check if all extensions are initialized. */
@@ -233,25 +284,6 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
       return extensions.isInitialized();
     }
 
-    /**
-     * Called by subclasses to parse an unknown field or an extension.
-     * @return {@code true} unless the tag is an end-group tag.
-     */
-    @Override
-    protected boolean parseUnknownField(
-        CodedInputStream input,
-        CodedOutputStream unknownFieldsCodedOutput,
-        ExtensionRegistryLite extensionRegistry,
-        int tag) throws IOException {
-      return GeneratedMessageLite.parseUnknownField(
-          extensions,
-          getDefaultInstanceForType(),
-          input,
-          unknownFieldsCodedOutput,
-          extensionRegistry,
-          tag);
-    }
-
 
     /**
      * Used by parsing constructors in generated classes.
@@ -377,30 +409,39 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
     /** Check if a singular extension is present. */
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     public final <Type> boolean hasExtension(
-        final GeneratedExtension<MessageType, Type> extension) {
-      verifyExtensionContainingType(extension);
-      return extensions.hasField(extension.descriptor);
+        final ExtensionLite<MessageType, Type> extension) {
+      GeneratedExtension<MessageType, Type> extensionLite =
+          checkIsLite(extension);
+      
+      verifyExtensionContainingType(extensionLite);
+      return extensions.hasField(extensionLite.descriptor);
     }
 
     /** Get the number of elements in a repeated extension. */
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     public final <Type> int getExtensionCount(
-        final GeneratedExtension<MessageType, List<Type>> extension) {
-      verifyExtensionContainingType(extension);
-      return extensions.getRepeatedFieldCount(extension.descriptor);
+        final ExtensionLite<MessageType, List<Type>> extension) {
+      GeneratedExtension<MessageType, List<Type>> extensionLite =
+          checkIsLite(extension);
+      
+      verifyExtensionContainingType(extensionLite);
+      return extensions.getRepeatedFieldCount(extensionLite.descriptor);
     }
 
     /** Get the value of an extension. */
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     @SuppressWarnings("unchecked")
     public final <Type> Type getExtension(
-        final GeneratedExtension<MessageType, Type> extension) {
-      verifyExtensionContainingType(extension);
-      final Object value = extensions.getField(extension.descriptor);
+        final ExtensionLite<MessageType, Type> extension) {
+      GeneratedExtension<MessageType, Type> extensionLite =
+          checkIsLite(extension);
+      
+      verifyExtensionContainingType(extensionLite);
+      final Object value = extensions.getField(extensionLite.descriptor);
       if (value == null) {
-        return extension.defaultValue;
+        return extensionLite.defaultValue;
       } else {
-        return (Type) extension.fromFieldSetType(value);
+        return (Type) extensionLite.fromFieldSetType(value);
       }
     }
 
@@ -408,11 +449,14 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
     @SuppressWarnings("unchecked")
     //@Override (Java 1.6 override semantics, but we must support 1.5)
     public final <Type> Type getExtension(
-        final GeneratedExtension<MessageType, List<Type>> extension,
+        final ExtensionLite<MessageType, List<Type>> extension,
         final int index) {
-      verifyExtensionContainingType(extension);
-      return (Type) extension.singularFromFieldSetType(
-          extensions.getRepeatedField(extension.descriptor, index));
+      GeneratedExtension<MessageType, List<Type>> extensionLite =
+          checkIsLite(extension);
+      
+      verifyExtensionContainingType(extensionLite);
+      return (Type) extensionLite.singularFromFieldSetType(
+          extensions.getRepeatedField(extensionLite.descriptor, index));
     }
 
     // This is implemented here only to work around an apparent bug in the
@@ -423,46 +467,57 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
       throw new UnsupportedOperationException(
           "This is supposed to be overridden by subclasses.");
     }
-
+    
     /** Set the value of an extension. */
     public final <Type> BuilderType setExtension(
-        final GeneratedExtension<MessageType, Type> extension,
+        final ExtensionLite<MessageType, Type> extension,
         final Type value) {
-      verifyExtensionContainingType(extension);
+      GeneratedExtension<MessageType, Type> extensionLite =
+          checkIsLite(extension);
+      
+      verifyExtensionContainingType(extensionLite);
       ensureExtensionsIsMutable();
-      extensions.setField(extension.descriptor,
-                          extension.toFieldSetType(value));
+      extensions.setField(extensionLite.descriptor,
+                          extensionLite.toFieldSetType(value));
       return (BuilderType) this;
     }
 
     /** Set the value of one element of a repeated extension. */
     public final <Type> BuilderType setExtension(
-        final GeneratedExtension<MessageType, List<Type>> extension,
+        final ExtensionLite<MessageType, List<Type>> extension,
         final int index, final Type value) {
-      verifyExtensionContainingType(extension);
+      GeneratedExtension<MessageType, List<Type>> extensionLite =
+          checkIsLite(extension);
+      
+      verifyExtensionContainingType(extensionLite);
       ensureExtensionsIsMutable();
-      extensions.setRepeatedField(extension.descriptor, index,
-                                  extension.singularToFieldSetType(value));
+      extensions.setRepeatedField(extensionLite.descriptor, index,
+                                  extensionLite.singularToFieldSetType(value));
       return (BuilderType) this;
     }
 
     /** Append a value to a repeated extension. */
     public final <Type> BuilderType addExtension(
-        final GeneratedExtension<MessageType, List<Type>> extension,
+        final ExtensionLite<MessageType, List<Type>> extension,
         final Type value) {
-      verifyExtensionContainingType(extension);
+      GeneratedExtension<MessageType, List<Type>> extensionLite =
+          checkIsLite(extension);
+      
+      verifyExtensionContainingType(extensionLite);
       ensureExtensionsIsMutable();
-      extensions.addRepeatedField(extension.descriptor,
-                                  extension.singularToFieldSetType(value));
+      extensions.addRepeatedField(extensionLite.descriptor,
+                                  extensionLite.singularToFieldSetType(value));
       return (BuilderType) this;
     }
 
     /** Clear an extension. */
     public final <Type> BuilderType clearExtension(
-        final GeneratedExtension<MessageType, ?> extension) {
-      verifyExtensionContainingType(extension);
+        final ExtensionLite<MessageType, ?> extension) {
+      GeneratedExtension<MessageType, ?> extensionLite = checkIsLite(extension);
+      
+      verifyExtensionContainingType(extensionLite);
       ensureExtensionsIsMutable();
-      extensions.clearField(extension.descriptor);
+      extensions.clearField(extensionLite.descriptor);
       return (BuilderType) this;
     }
 
@@ -471,44 +526,24 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
       return extensions.isInitialized();
     }
 
-    /**
-     * Called by subclasses to parse an unknown field or an extension.
-     * @return {@code true} unless the tag is an end-group tag.
-     */
-    @Override
-    protected boolean parseUnknownField(
-        CodedInputStream input,
-        CodedOutputStream unknownFieldsCodedOutput,
-        ExtensionRegistryLite extensionRegistry,
-        int tag) throws IOException {
-      ensureExtensionsIsMutable();
-      return GeneratedMessageLite.parseUnknownField(
-          extensions,
-          getDefaultInstanceForType(),
-          input,
-          unknownFieldsCodedOutput,
-          extensionRegistry,
-          tag);
-    }
-
     protected final void mergeExtensionFields(final MessageType other) {
       ensureExtensionsIsMutable();
       extensions.mergeFrom(((ExtendableMessage) other).extensions);
     }
   }
 
-  // -----------------------------------------------------------------
+  //-----------------------------------------------------------------
 
   /**
-   * Parse an unknown field or an extension.
+   * Parse an unknown field or an extension. For use by generated code only.
    * @return {@code true} unless the tag is an end-group tag.
    */
-  private static <MessageType extends MessageLite>
+  protected static <MessageType extends MessageLite>
       boolean parseUnknownField(
           FieldSet<ExtensionDescriptor> extensions,
           MessageType defaultInstance,
           CodedInputStream input,
-          CodedOutputStream unknownFieldsCodedOutput,
+          UnknownFieldSetLite.Builder unknownFields,
           ExtensionRegistryLite extensionRegistry,
           int tag) throws IOException {
     int wireType = WireFormat.getTagWireType(tag);
@@ -537,7 +572,7 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
     }
 
     if (unknown) {  // Unknown field or wrong wire type.  Skip.
-      return input.skipField(tag, unknownFieldsCodedOutput);
+      return unknownFields.mergeFieldFrom(tag, input);
     }
 
     if (packed) {
@@ -599,8 +634,7 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
           // If the number isn't recognized as a valid value for this enum,
           // write it to unknown fields object.
           if (value == null) {
-            unknownFieldsCodedOutput.writeRawVarint32(tag);
-            unknownFieldsCodedOutput.writeUInt32NoTag(rawValue);
+            unknownFields.mergeVarintField(fieldNumber, rawValue);
             return true;
           }
           break;
@@ -768,7 +802,8 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
    * this type as parameters to extension accessors and ExtensionRegistry.add().
    */
   public static class GeneratedExtension<
-      ContainingType extends MessageLite, Type> {
+      ContainingType extends MessageLite, Type>
+          extends ExtensionLite<ContainingType, Type> {
 
     /**
      * Create a new isntance with the given parameters.
@@ -888,6 +923,18 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
         return value;
       }
     }
+
+    public FieldType getLiteType() {
+      return descriptor.getLiteType();
+    }
+
+    public boolean isRepeated() {
+      return descriptor.isRepeated;
+    }
+
+    public Type getDefaultValue() {
+      return defaultValue;
+    }
   }
 
   /**
@@ -897,8 +944,8 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
   static final class SerializedForm implements Serializable {
     private static final long serialVersionUID = 0L;
 
-    private String messageClassName;
-    private byte[] asBytes;
+    private final String messageClassName;
+    private final byte[] asBytes;
 
     /**
      * Creates the serialized form by calling {@link com.google.protobuf.MessageLite#toByteArray}.
@@ -918,19 +965,17 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
     protected Object readResolve() throws ObjectStreamException {
       try {
         Class messageClass = Class.forName(messageClassName);
-        Method newBuilder = messageClass.getMethod("newBuilder");
-        MessageLite.Builder builder =
-            (MessageLite.Builder) newBuilder.invoke(null);
-        builder.mergeFrom(asBytes);
-        return builder.buildPartial();
+        Parser<?> parser =
+            (Parser<?>) messageClass.getField("PARSER").get(null);
+        return parser.parsePartialFrom(asBytes);
       } catch (ClassNotFoundException e) {
         throw new RuntimeException("Unable to find proto buffer class", e);
-      } catch (NoSuchMethodException e) {
-        throw new RuntimeException("Unable to find newBuilder method", e);
+      } catch (NoSuchFieldException e) {
+        throw new RuntimeException("Unable to find PARSER", e);
+      } catch (SecurityException e) {
+        throw new RuntimeException("Unable to call PARSER", e);
       } catch (IllegalAccessException e) {
-        throw new RuntimeException("Unable to call newBuilder method", e);
-      } catch (InvocationTargetException e) {
-        throw new RuntimeException("Error calling newBuilder", e.getCause());
+        throw new RuntimeException("Unable to call parseFrom method", e);
       } catch (InvalidProtocolBufferException e) {
         throw new RuntimeException("Unable to understand proto buffer", e);
       }
@@ -946,4 +991,18 @@ public abstract class GeneratedMessageLite extends AbstractMessageLite
   protected Object writeReplace() throws ObjectStreamException {
     return new SerializedForm(this);
   }
+  
+  /**
+   * Checks that the {@link Extension} is Lite and returns it as a
+   * {@link GeneratedExtension}.
+   */
+  private static <MessageType extends ExtendableMessage<MessageType>, T>
+    GeneratedExtension<MessageType, T> checkIsLite(
+        ExtensionLite<MessageType, T> extension) {
+    if (!extension.isLite()) {
+      throw new IllegalArgumentException("Expected a lite extension.");
+    }
+    
+    return (GeneratedExtension<MessageType, T>) extension;
+  }
 }
diff --git a/java/src/main/java/com/google/protobuf/Internal.java b/java/src/main/java/com/google/protobuf/Internal.java
index 48d29e69..ba0f526b 100644
--- a/java/src/main/java/com/google/protobuf/Internal.java
+++ b/java/src/main/java/com/google/protobuf/Internal.java
@@ -33,8 +33,14 @@ package com.google.protobuf;
 import java.io.IOException;
 import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
+import java.util.AbstractList;
+import java.util.AbstractMap;
+import java.util.AbstractSet;
 import java.util.Arrays;
+import java.util.Iterator;
 import java.util.List;
+import java.util.Map;
+import java.util.Set;
 
 /**
  * The classes contained within are used internally by the Protocol Buffer
@@ -388,4 +394,164 @@ public class Internal {
   public static final ByteBuffer EMPTY_BYTE_BUFFER =
       ByteBuffer.wrap(EMPTY_BYTE_ARRAY);
 
+
+  /**
+   * Provides an immutable view of List<T> around a List<F>.
+   *
+   * Protobuf internal. Used in protobuf generated code only.
+   */
+  public static class ListAdapter<F, T> extends AbstractList<T> {
+    /**
+     * Convert individual elements of the List from F to T.
+     */
+    public interface Converter<F, T> {
+      T convert(F from);
+    }
+
+    private final List<F> fromList;
+    private final Converter<F, T> converter;
+
+    public ListAdapter(List<F> fromList, Converter<F, T> converter) {
+      this.fromList = fromList;
+      this.converter = converter;
+    }
+
+    @Override
+    public T get(int index) {
+      return converter.convert(fromList.get(index));
+    }
+
+    @Override
+    public int size() {
+      return fromList.size();
+    }
+  }
+
+  /**
+   * Wrap around a Map<K, RealValue> and provide a Map<K, V> interface.
+   */
+  public static class MapAdapter<K, V, RealValue> extends AbstractMap<K, V> {
+    /**
+     * An interface used to convert between two types.
+     */
+    public interface Converter<A, B> {
+      B doForward(A object);
+      A doBackward(B object);
+    }
+
+    public static <T extends EnumLite> Converter<Integer, T> newEnumConverter(
+        final EnumLiteMap<T> enumMap, final T unrecognizedValue) {
+      return new Converter<Integer, T>() {
+        public T doForward(Integer value) {
+          T result = enumMap.findValueByNumber(value);
+          return result == null ? unrecognizedValue : result;
+        }
+        public Integer doBackward(T value) {
+          return value.getNumber();
+        }
+      };
+    }
+
+    private final Map<K, RealValue> realMap;
+    private final Converter<RealValue, V> valueConverter;
+    
+    public MapAdapter(Map<K, RealValue> realMap,
+        Converter<RealValue, V> valueConverter) {
+      this.realMap = realMap;
+      this.valueConverter = valueConverter;
+    }
+    
+    @SuppressWarnings("unchecked")
+    @Override
+    public V get(Object key) {
+      RealValue result = realMap.get(key);
+      if (result == null) {
+        return null;
+      }
+      return valueConverter.doForward(result);
+    }
+    
+    @Override
+    public V put(K key, V value) {
+      RealValue oldValue = realMap.put(key, valueConverter.doBackward(value));
+      if (oldValue == null) {
+        return null;
+      }
+      return valueConverter.doForward(oldValue);
+    }
+
+    @Override
+    public Set<java.util.Map.Entry<K, V>> entrySet() {
+      return new SetAdapter(realMap.entrySet());
+    }
+    
+    private class SetAdapter extends AbstractSet<Map.Entry<K, V>> {
+      private final Set<Map.Entry<K, RealValue>> realSet;
+      public SetAdapter(Set<Map.Entry<K, RealValue>> realSet) {
+        this.realSet = realSet;
+      }
+      
+      @Override
+      public Iterator<java.util.Map.Entry<K, V>> iterator() {
+        return new IteratorAdapter(realSet.iterator());
+      }
+
+      @Override
+      public int size() {
+        return realSet.size();
+      } 
+    }
+    
+    private class IteratorAdapter implements Iterator<Map.Entry<K, V>> {
+      private final Iterator<Map.Entry<K, RealValue>> realIterator;
+      
+      public IteratorAdapter(
+          Iterator<Map.Entry<K, RealValue>> realIterator) {
+        this.realIterator = realIterator;
+      }
+      
+      @Override
+      public boolean hasNext() {
+        return realIterator.hasNext();
+      }
+
+      @Override
+      public java.util.Map.Entry<K, V> next() {
+        return new EntryAdapter(realIterator.next());
+      }
+
+      @Override
+      public void remove() {
+        realIterator.remove();
+      }
+    }
+    
+    private class EntryAdapter implements Map.Entry<K, V> {
+      private final Map.Entry<K, RealValue> realEntry;
+      
+      public EntryAdapter(Map.Entry<K, RealValue> realEntry) {
+        this.realEntry = realEntry;
+      }
+      
+      @Override
+      public K getKey() {
+        return realEntry.getKey();
+      }
+
+      @Override
+      public V getValue() {
+        return valueConverter.doForward(realEntry.getValue());
+      }
+
+      @Override
+      public V setValue(V value) {
+        RealValue oldValue = realEntry.setValue(
+            valueConverter.doBackward(value));
+        if (oldValue == null) {
+          return null;
+        }
+        return valueConverter.doForward(oldValue);
+      }
+    }
+  }
 }
diff --git a/java/src/main/java/com/google/protobuf/LazyStringArrayList.java b/java/src/main/java/com/google/protobuf/LazyStringArrayList.java
index 61c7e1ea..2d40a51f 100644
--- a/java/src/main/java/com/google/protobuf/LazyStringArrayList.java
+++ b/java/src/main/java/com/google/protobuf/LazyStringArrayList.java
@@ -74,6 +74,10 @@ public class LazyStringArrayList extends AbstractList<String>
     list = new ArrayList<Object>();
   }
 
+  public LazyStringArrayList(int intialCapacity) {
+    list = new ArrayList<Object>(intialCapacity);
+  }
+
   public LazyStringArrayList(LazyStringList from) {
     list = new ArrayList<Object>(from.size());
     addAll(from);
diff --git a/java/src/main/java/com/google/protobuf/LiteralByteString.java b/java/src/main/java/com/google/protobuf/LiteralByteString.java
index 83e71e93..127c574d 100644
--- a/java/src/main/java/com/google/protobuf/LiteralByteString.java
+++ b/java/src/main/java/com/google/protobuf/LiteralByteString.java
@@ -190,6 +190,15 @@ class LiteralByteString extends ByteString {
     }
 
     if (other instanceof LiteralByteString) {
+      LiteralByteString otherAsLiteral = (LiteralByteString) other;
+      // If we know the hash codes and they are not equal, we know the byte
+      // strings are not equal.
+      if (hash != 0 
+          && otherAsLiteral.hash != 0 
+          && hash != otherAsLiteral.hash) {
+        return false;
+      }
+      
       return equalsRange((LiteralByteString) other, 0, size());
     } else if (other instanceof RopeByteString) {
       return other.equals(this);
diff --git a/java/src/main/java/com/google/protobuf/MapEntry.java b/java/src/main/java/com/google/protobuf/MapEntry.java
new file mode 100644
index 00000000..8e3551b6
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/MapEntry.java
@@ -0,0 +1,433 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.EnumValueDescriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+
+import java.io.IOException;
+import java.util.Collections;
+import java.util.Map;
+import java.util.TreeMap;
+
+/**
+ * Implements MapEntry messages.
+ * 
+ * In reflection API, map fields will be treated as repeated message fields and
+ * each map entry is accessed as a message. This MapEntry class is used to
+ * represent these map entry messages in reflection API.
+ * 
+ * Protobuf internal. Users shouldn't use this class.
+ */
+public final class MapEntry<K, V> extends AbstractMessage {
+  private static class Metadata<K, V> {
+    public final Descriptor descriptor;  
+    public final MapEntry<K, V> defaultInstance;
+    public final AbstractParser<MapEntry<K, V>> parser;
+    
+    public Metadata(
+        final Descriptor descriptor, final MapEntry<K, V> defaultInstance) {
+      this.descriptor = descriptor;
+      this.defaultInstance = defaultInstance;
+      final Metadata<K, V> thisMetadata = this;
+      this.parser = new AbstractParser<MapEntry<K, V>>() {
+        private final Parser<MapEntryLite<K, V>> dataParser =
+            defaultInstance.data.getParserForType();
+        @Override
+        public MapEntry<K, V> parsePartialFrom(
+            CodedInputStream input, ExtensionRegistryLite extensionRegistry)
+            throws InvalidProtocolBufferException {
+          MapEntryLite<K, V> data =
+              dataParser.parsePartialFrom(input, extensionRegistry);
+          return new MapEntry<K, V>(thisMetadata, data);
+        }
+        
+      };
+    }
+  }
+  
+  private final Metadata<K, V> metadata;
+  private final MapEntryLite<K, V> data;
+  
+  /** Create a default MapEntry instance. */
+  private MapEntry(Descriptor descriptor,
+      WireFormat.FieldType keyType, K defaultKey,
+      WireFormat.FieldType valueType, V defaultValue) {
+    this.data = MapEntryLite.newDefaultInstance(
+        keyType, defaultKey, valueType, defaultValue);
+    this.metadata = new Metadata<K, V>(descriptor, this); 
+  }
+  
+  /** Create a new MapEntry message. */
+  private MapEntry(Metadata<K, V> metadata, MapEntryLite<K, V> data) {
+    this.metadata = metadata;
+    this.data = data;
+  }
+  
+  /**
+   * Create a default MapEntry instance. A default MapEntry instance should be
+   * created only once for each map entry message type. Generated code should
+   * store the created default instance and use it later to create new MapEntry
+   * messages of the same type. 
+   */
+  public static <K, V> MapEntry<K, V> newDefaultInstance(
+      Descriptor descriptor,
+      WireFormat.FieldType keyType, K defaultKey,
+      WireFormat.FieldType valueType, V defaultValue) {
+    return new MapEntry<K, V>(
+        descriptor, keyType, defaultKey, valueType, defaultValue);
+  }
+  
+  public K getKey() {
+    return data.getKey();
+  }
+  
+  public V getValue() {
+    return data.getValue();
+  }
+  
+  @Override
+  public int getSerializedSize() {
+    return data.getSerializedSize();
+  }
+  
+  @Override
+  public void writeTo(CodedOutputStream output) throws IOException {
+    data.writeTo(output);
+  }
+  
+  @Override
+  public boolean isInitialized() {
+    return data.isInitialized();
+  }
+  
+  @Override
+  public Parser<MapEntry<K, V>> getParserForType() {
+    return metadata.parser;
+  }
+
+  @Override
+  public Builder<K, V> newBuilderForType() {
+    return new Builder<K, V>(metadata);
+  }
+  
+  @Override
+  public Builder<K, V> toBuilder() {
+    return new Builder<K, V>(metadata, data);
+  }
+
+  @Override
+  public MapEntry<K, V> getDefaultInstanceForType() {
+    return metadata.defaultInstance;
+  }
+
+  @Override
+  public Descriptor getDescriptorForType() {
+    return metadata.descriptor;
+  }
+
+  @Override
+  public Map<FieldDescriptor, Object> getAllFields() {
+    final TreeMap<FieldDescriptor, Object> result =
+        new TreeMap<FieldDescriptor, Object>();
+    for (final FieldDescriptor field : metadata.descriptor.getFields()) {
+      if (hasField(field)) {
+        result.put(field, getField(field));
+      }
+    }
+    return Collections.unmodifiableMap(result);
+  }
+  
+  private void checkFieldDescriptor(FieldDescriptor field) {
+    if (field.getContainingType() != metadata.descriptor) {
+      throw new RuntimeException(
+          "Wrong FieldDescriptor \"" + field.getFullName()
+          + "\" used in message \"" + metadata.descriptor.getFullName()); 
+    }
+  }
+
+  @Override
+  public boolean hasField(FieldDescriptor field) {
+    checkFieldDescriptor(field);;
+    // A MapEntry always contains two fields.
+    return true;
+  }
+
+  @Override
+  public Object getField(FieldDescriptor field) {
+    checkFieldDescriptor(field);
+    Object result = field.getNumber() == 1 ? getKey() : getValue();
+    // Convert enums to EnumValueDescriptor.
+    if (field.getType() == FieldDescriptor.Type.ENUM) {
+      result = field.getEnumType().findValueByNumberCreatingIfUnknown(
+          (java.lang.Integer) result);
+    }
+    return result;
+  }
+
+  @Override
+  public int getRepeatedFieldCount(FieldDescriptor field) {
+    throw new RuntimeException(
+        "There is no repeated field in a map entry message.");
+  }
+
+  @Override
+  public Object getRepeatedField(FieldDescriptor field, int index) {
+    throw new RuntimeException(
+        "There is no repeated field in a map entry message.");
+  }
+
+  @Override
+  public UnknownFieldSet getUnknownFields() {
+    return UnknownFieldSet.getDefaultInstance();
+  }
+
+  /**
+   * Builder to create {@link MapEntry} messages.
+   */
+  public static class Builder<K, V>
+      extends AbstractMessage.Builder<Builder<K, V>> {
+    private final Metadata<K, V> metadata;
+    private MapEntryLite<K, V> data;
+    private MapEntryLite.Builder<K, V> dataBuilder;
+    
+    private Builder(Metadata<K, V> metadata) {
+      this.metadata = metadata;
+      this.data = metadata.defaultInstance.data;
+      this.dataBuilder = null;
+    }
+    
+    private Builder(Metadata<K, V> metadata, MapEntryLite<K, V> data) {
+      this.metadata = metadata;
+      this.data = data;
+      this.dataBuilder = null;
+    }
+    
+    public K getKey() {
+      return dataBuilder == null ? data.getKey() : dataBuilder.getKey();
+    }
+    
+    public V getValue() {
+      return dataBuilder == null ? data.getValue() : dataBuilder.getValue();
+    }
+    
+    private void ensureMutable() {
+      if (dataBuilder == null) {
+        dataBuilder = data.toBuilder();
+      }
+    }
+    
+    public Builder<K, V> setKey(K key) {
+      ensureMutable();
+      dataBuilder.setKey(key);
+      return this;
+    }
+    
+    public Builder<K, V> clearKey() {
+      ensureMutable();
+      dataBuilder.clearKey();
+      return this;
+    }
+    
+    public Builder<K, V> setValue(V value) {
+      ensureMutable();
+      dataBuilder.setValue(value);
+      return this;
+    }
+    
+    public Builder<K, V> clearValue() {
+      ensureMutable();
+      dataBuilder.clearValue();
+      return this;
+    }
+
+    @Override
+    public MapEntry<K, V> build() {
+      MapEntry<K, V> result = buildPartial();
+      if (!result.isInitialized()) {
+        throw newUninitializedMessageException(result);
+      }
+      return result;
+    }
+
+    @Override
+    public MapEntry<K, V> buildPartial() {
+      if (dataBuilder != null) {
+        data = dataBuilder.build();
+        dataBuilder = null;
+      }
+      return new MapEntry<K, V>(metadata, data);
+    }
+
+    @Override
+    public Descriptor getDescriptorForType() {
+      return metadata.descriptor;
+    }
+    
+    private void checkFieldDescriptor(FieldDescriptor field) {
+      if (field.getContainingType() != metadata.descriptor) {
+        throw new RuntimeException(
+            "Wrong FieldDescriptor \"" + field.getFullName()
+            + "\" used in message \"" + metadata.descriptor.getFullName()); 
+      }
+    }
+
+    @Override
+    public com.google.protobuf.Message.Builder newBuilderForField(
+        FieldDescriptor field) {
+      checkFieldDescriptor(field);;
+      // This method should be called for message fields and in a MapEntry
+      // message only the value field can possibly be a message field.
+      if (field.getNumber() != 2
+          || field.getJavaType() != FieldDescriptor.JavaType.MESSAGE) {
+        throw new RuntimeException(
+            "\"" + field.getFullName() + "\" is not a message value field.");
+      }
+      return ((Message) data.getValue()).newBuilderForType();
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public Builder<K, V> setField(FieldDescriptor field, Object value) {
+      checkFieldDescriptor(field);
+      if (field.getNumber() == 1) {
+        setKey((K) value);
+      } else {
+        if (field.getType() == FieldDescriptor.Type.ENUM) {
+          value = ((EnumValueDescriptor) value).getNumber();
+        }
+        setValue((V) value);
+      }
+      return this;
+    }
+
+    @Override
+    public Builder<K, V> clearField(FieldDescriptor field) {
+      checkFieldDescriptor(field);
+      if (field.getNumber() == 1) {
+        clearKey();
+      } else {
+        clearValue();
+      }
+      return this;
+    }
+
+    @Override
+    public Builder<K, V> setRepeatedField(FieldDescriptor field, int index,
+        Object value) {
+      throw new RuntimeException(
+          "There is no repeated field in a map entry message.");
+    }
+
+    @Override
+    public Builder<K, V> addRepeatedField(FieldDescriptor field, Object value) {
+      throw new RuntimeException(
+          "There is no repeated field in a map entry message.");
+    }
+
+    @Override
+    public Builder<K, V> setUnknownFields(UnknownFieldSet unknownFields) {
+      // Unknown fields are discarded for MapEntry message.
+      return this;
+    }
+
+    @Override
+    public MapEntry<K, V> getDefaultInstanceForType() {
+      return metadata.defaultInstance;
+    }
+
+    @Override
+    public boolean isInitialized() {
+      if (dataBuilder != null) {
+        return dataBuilder.isInitialized();
+      } else {
+        return data.isInitialized();
+      }
+    }
+
+    @Override
+    public Map<FieldDescriptor, Object> getAllFields() {
+      final TreeMap<FieldDescriptor, Object> result =
+          new TreeMap<FieldDescriptor, Object>();
+      for (final FieldDescriptor field : metadata.descriptor.getFields()) {
+        if (hasField(field)) {
+          result.put(field, getField(field));
+        }
+      }
+      return Collections.unmodifiableMap(result);
+    }
+
+    @Override
+    public boolean hasField(FieldDescriptor field) {
+      checkFieldDescriptor(field);
+      return true;
+    }
+
+    @Override
+    public Object getField(FieldDescriptor field) {
+      checkFieldDescriptor(field);
+      Object result = field.getNumber() == 1 ? getKey() : getValue();
+      // Convert enums to EnumValueDescriptor.
+      if (field.getType() == FieldDescriptor.Type.ENUM) {
+        result = field.getEnumType().findValueByNumberCreatingIfUnknown(
+            (java.lang.Integer) result);
+      }
+      return result;
+    }
+
+    @Override
+    public int getRepeatedFieldCount(FieldDescriptor field) {
+      throw new RuntimeException(
+          "There is no repeated field in a map entry message.");
+    }
+    
+    @Override
+    public Object getRepeatedField(FieldDescriptor field, int index) {
+      throw new RuntimeException(
+          "There is no repeated field in a map entry message.");
+    }
+    
+    @Override
+    public UnknownFieldSet getUnknownFields() {
+      return UnknownFieldSet.getDefaultInstance();
+    }
+
+    @Override
+    public Builder<K, V> clone() {
+      if (dataBuilder == null) {
+        return new Builder<K, V>(metadata, data);
+      } else {
+        return new Builder<K, V>(metadata, dataBuilder.build());
+      }
+    }
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/MapEntryLite.java b/java/src/main/java/com/google/protobuf/MapEntryLite.java
new file mode 100644
index 00000000..bcffa946
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/MapEntryLite.java
@@ -0,0 +1,331 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.io.IOException;
+
+/**
+ * Implements the lite version of map entry messages.
+ * 
+ * This class serves as an utility class to help do serialization/parsing of
+ * map entries. It's used in generated code and also in the full version
+ * MapEntry message.
+ * 
+ * Protobuf internal. Users shouldn't use.
+ */
+public class MapEntryLite<K, V> extends AbstractMessageLite {
+  private static class Metadata<K, V> {
+    public final MapEntryLite<K, V> defaultInstance;
+    public final WireFormat.FieldType keyType;
+    public final WireFormat.FieldType valueType;
+    public final Parser<MapEntryLite<K, V>> parser;
+    public Metadata(
+        MapEntryLite<K, V> defaultInstance,
+        WireFormat.FieldType keyType,
+        WireFormat.FieldType valueType) {
+      this.defaultInstance = defaultInstance; 
+      this.keyType = keyType;
+      this.valueType = valueType;
+      final Metadata<K, V> finalThis = this;
+      this.parser = new AbstractParser<MapEntryLite<K, V>>() {
+        @Override
+        public MapEntryLite<K, V> parsePartialFrom(
+            CodedInputStream input, ExtensionRegistryLite extensionRegistry)
+            throws InvalidProtocolBufferException {
+          return new MapEntryLite<K, V>(finalThis, input, extensionRegistry);
+        }
+      };
+    }
+  }
+  
+  private static final int KEY_FIELD_NUMBER = 1;
+  private static final int VALUE_FIELD_NUMBER = 2;
+  
+  private final Metadata<K, V> metadata;
+  private final K key;
+  private final V value;
+  
+  /** Creates a default MapEntryLite message instance. */
+  private MapEntryLite(
+      WireFormat.FieldType keyType, K defaultKey,
+      WireFormat.FieldType valueType, V defaultValue) {
+    this.metadata = new Metadata<K, V>(this, keyType, valueType);
+    this.key = defaultKey;
+    this.value = defaultValue;
+  }
+  
+  /** Creates a new MapEntryLite message. */
+  private MapEntryLite(Metadata<K, V> metadata, K key, V value) {
+    this.metadata = metadata;
+    this.key = key;
+    this.value = value;
+  }
+  
+  public K getKey() {
+    return key;
+  }
+  
+  public V getValue() {
+    return value;
+  }
+
+  /**
+   * Creates a default MapEntryLite message instance.
+   * 
+   * This method is used by generated code to create the default instance for
+   * a map entry message. The created default instance should be used to create
+   * new map entry messages of the same type. For each map entry message, only
+   * one default instance should be created. 
+   */
+  public static <K, V> MapEntryLite<K, V> newDefaultInstance(
+      WireFormat.FieldType keyType, K defaultKey,
+      WireFormat.FieldType valueType, V defaultValue) {
+    return new MapEntryLite<K, V>(
+        keyType, defaultKey, valueType, defaultValue);
+  }
+  
+  @Override
+  public void writeTo(CodedOutputStream output) throws IOException {
+    writeField(KEY_FIELD_NUMBER, metadata.keyType, key, output);
+    writeField(VALUE_FIELD_NUMBER, metadata.valueType, value, output);
+  }
+
+  private void writeField(
+      int number, WireFormat.FieldType type, Object value,
+      CodedOutputStream output) throws IOException {
+    output.writeTag(number, type.getWireType());
+    FieldSet.writeElementNoTag(output, type, value);
+  }
+
+  private volatile int cachedSerializedSize = -1;
+  @Override
+  public int getSerializedSize() {
+    if (cachedSerializedSize != -1) {
+      return cachedSerializedSize;
+    }
+    int size = 0;
+    size += getFieldSize(KEY_FIELD_NUMBER, metadata.keyType, key);
+    size += getFieldSize(VALUE_FIELD_NUMBER, metadata.valueType, value);
+    cachedSerializedSize = size;
+    return size;
+  }
+
+  private int getFieldSize(
+      int number, WireFormat.FieldType type, Object value) {
+    return CodedOutputStream.computeTagSize(number)
+        + FieldSet.computeElementSizeNoTag(type, value);
+  }
+  
+  /** Parsing constructor. */
+  private MapEntryLite(
+      Metadata<K, V> metadata,
+      CodedInputStream input,
+      ExtensionRegistryLite extensionRegistry)
+      throws InvalidProtocolBufferException {
+    try {
+      K key = metadata.defaultInstance.key;
+      V value = metadata.defaultInstance.value;
+      while (true) {
+        int tag = input.readTag();
+        if (tag == 0) {
+          break;
+        }
+        if (tag == WireFormat.makeTag(
+                KEY_FIELD_NUMBER, metadata.keyType.getWireType())) {
+          key = mergeField(
+              input, extensionRegistry, metadata.keyType, key);
+        } else if (tag == WireFormat.makeTag(
+                       VALUE_FIELD_NUMBER, metadata.valueType.getWireType())) {
+          value = mergeField(
+              input, extensionRegistry, metadata.valueType, value);
+        } else {
+          if (!input.skipField(tag)) {
+            break;
+          }
+        }
+      }
+      this.metadata = metadata;
+      this.key = key;
+      this.value = value;
+    } catch (InvalidProtocolBufferException e) {
+      throw e.setUnfinishedMessage(this);
+    } catch (IOException e) {
+      throw new InvalidProtocolBufferException(e.getMessage())
+          .setUnfinishedMessage(this);
+    }
+  }
+  
+  @SuppressWarnings("unchecked")
+  private <T> T mergeField(
+      CodedInputStream input, ExtensionRegistryLite extensionRegistry,
+      WireFormat.FieldType type, T value) throws IOException {
+    switch (type) {
+      case MESSAGE:
+        MessageLite.Builder subBuilder = ((MessageLite) value).toBuilder();
+        input.readMessage(subBuilder, extensionRegistry);
+        return (T) subBuilder.buildPartial();
+      case ENUM:
+        return (T) (java.lang.Integer) input.readEnum();
+      case GROUP:
+        throw new RuntimeException("Groups are not allowed in maps.");
+      default:
+        return (T) FieldSet.readPrimitiveField(input, type, true);
+    }
+  }
+
+  @Override
+  public Parser<MapEntryLite<K, V>> getParserForType() {
+    return metadata.parser;
+  }
+
+  @Override
+  public Builder<K, V> newBuilderForType() {
+    return new Builder<K, V>(metadata);
+  }
+
+  @Override
+  public Builder<K, V> toBuilder() {
+    return new Builder<K, V>(metadata, key, value);
+  }
+
+  @Override
+  public MapEntryLite<K, V> getDefaultInstanceForType() {
+    return metadata.defaultInstance;
+  }
+
+  @Override
+  public boolean isInitialized() {
+    if (metadata.valueType.getJavaType() == WireFormat.JavaType.MESSAGE) {
+      return ((MessageLite) value).isInitialized();
+    }
+    return true;
+  }
+
+  /**
+   * Builder used to create {@link MapEntryLite} messages.
+   */
+  public static class Builder<K, V>
+      extends AbstractMessageLite.Builder<Builder<K, V>> {
+    private final Metadata<K, V> metadata;
+    private K key;
+    private V value;
+    
+    private Builder(Metadata<K, V> metadata) {
+      this.metadata = metadata;
+      this.key = metadata.defaultInstance.key;
+      this.value = metadata.defaultInstance.value;
+    }
+    
+    public K getKey() {
+      return key;
+    }
+    
+    public V getValue() {
+      return value;
+    }
+    
+    public Builder<K, V> setKey(K key) {
+      this.key = key;
+      return this;
+    }
+    
+    public Builder<K, V> setValue(V value) {
+      this.value = value;
+      return this;
+    }
+    
+    public Builder<K, V> clearKey() {
+      this.key = metadata.defaultInstance.key;
+      return this;
+    }
+    
+    public Builder<K, V> clearValue() {
+      this.value = metadata.defaultInstance.value;
+      return this;
+    }
+
+    @Override
+    public Builder<K, V> clear() {
+      this.key = metadata.defaultInstance.key;
+      this.value = metadata.defaultInstance.value;
+      return this;
+    }
+
+    @Override
+    public MapEntryLite<K, V> build() {
+      MapEntryLite<K, V> result = buildPartial();
+      if (!result.isInitialized()) {
+        throw newUninitializedMessageException(result);
+      }
+      return result;
+    }
+
+    @Override
+    public MapEntryLite<K, V> buildPartial() {
+      return new MapEntryLite<K, V>(metadata, key, value);
+    }
+
+    @Override
+    public MessageLite getDefaultInstanceForType() {
+      return metadata.defaultInstance;
+    }
+
+    @Override
+    public boolean isInitialized() {
+      if (metadata.valueType.getJavaType() == WireFormat.JavaType.MESSAGE) {
+        return ((MessageLite) value).isInitialized();
+      }
+      return true;
+    }
+
+    private Builder(Metadata<K, V> metadata, K key, V value) {
+      this.metadata = metadata;
+      this.key = key;
+      this.value = value;
+    }
+    
+    @Override
+    public Builder<K, V> clone() {
+      return new Builder<K, V>(metadata, key, value);
+    }
+
+    @Override
+    public Builder<K, V> mergeFrom(
+        CodedInputStream input, ExtensionRegistryLite extensionRegistry)
+        throws IOException {
+      MapEntryLite<K, V> entry =
+          new MapEntryLite<K, V>(metadata, input, extensionRegistry);
+      this.key = entry.key;
+      this.value = entry.value;
+      return this;
+    }
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/MapField.java b/java/src/main/java/com/google/protobuf/MapField.java
new file mode 100644
index 00000000..5bd70dbb
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/MapField.java
@@ -0,0 +1,259 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Internal representation of map fields in generated messages.
+ * 
+ * This class supports accessing the map field as a {@link Map} to be used in
+ * generated API and also supports accessing the field as a {@link List} to be
+ * used in reflection API. It keeps track of where the data is currently stored
+ * and do necessary conversions between map and list.  
+ * 
+ * This class is a protobuf implementation detail. Users shouldn't use this
+ * class directly.
+ * 
+ * THREAD-SAFETY NOTE: Read-only access is thread-safe. Users can call getMap()
+ * and getList() concurrently in multiple threads. If write-access is needed,
+ * all access must be synchronized.
+ */
+public class MapField<K, V> {
+  /**
+   * Indicates where the data of this map field is currently stored.
+   * 
+   * MAP: Data is stored in mapData.
+   * LIST: Data is stored in listData.
+   * BOTH: mapData and listData have the same data.
+   *
+   * When the map field is accessed (through generated API or reflection API),
+   * it will shift between these 3 modes:
+   * 
+   *          getMap()   getList()   getMutableMap()   getMutableList()
+   *   MAP      MAP        BOTH          MAP               LIST
+   *   LIST     BOTH       LIST          MAP               LIST
+   *   BOTH     BOTH       BOTH          MAP               LIST
+   *   
+   * As the map field changes its mode, the list/map reference returned in a
+   * previous method call may be invalidated. 
+   */
+  private enum StorageMode {MAP, LIST, BOTH}
+
+  private volatile StorageMode mode;
+  private Map<K, V> mapData;
+  private List<Message> listData;
+  
+  // Convert between a map entry Message and a key-value pair.
+  private static interface Converter<K, V> {
+    Message convertKeyAndValueToMessage(K key, V value);
+    void convertMessageToKeyAndValue(Message message, Map<K, V> map);
+    
+    Message getMessageDefaultInstance();
+  }
+  
+  private static class ImmutableMessageConverter<K, V> implements Converter<K, V> {
+    private final MapEntry<K, V> defaultEntry;
+    public ImmutableMessageConverter(MapEntry<K, V> defaultEntry) {
+      this.defaultEntry = defaultEntry;
+    }
+    
+    public Message convertKeyAndValueToMessage(K key, V value) {
+      return defaultEntry.newBuilderForType().setKey(key).setValue(value).build();
+    }
+    
+    public void convertMessageToKeyAndValue(Message message, Map<K, V> map) {
+      MapEntry<K, V> entry = (MapEntry<K, V>) message;
+      map.put(entry.getKey(), entry.getValue());
+    }
+
+    public Message getMessageDefaultInstance() {
+      return defaultEntry;
+    }
+  }
+  
+
+  private final Converter<K, V> converter;
+  
+  private MapField(
+      Converter<K, V> converter,
+      StorageMode mode,
+      Map<K, V> mapData,
+      List<Message> listData) {
+    this.converter = converter;
+    this.mode = mode;
+    this.mapData = mapData;
+    this.listData = listData;
+  }
+    
+  private MapField(
+      MapEntry<K, V> defaultEntry,
+      StorageMode mode,
+      Map<K, V> mapData,
+      List<Message> listData) {
+    this(new ImmutableMessageConverter<K, V>(defaultEntry), mode, mapData, listData);
+  }
+  
+  
+  /** Returns an immutable empty MapField. */
+  public static <K, V> MapField<K, V> emptyMapField(
+      MapEntry<K, V> defaultEntry) {
+    return new MapField<K, V>(
+        defaultEntry, StorageMode.MAP, Collections.<K, V>emptyMap(), null);
+  }
+  
+  
+  /** Creates a new mutable empty MapField. */
+  public static <K, V> MapField<K, V> newMapField(MapEntry<K, V> defaultEntry) {
+    return new MapField<K, V>(
+        defaultEntry, StorageMode.MAP, new HashMap<K, V>(), null);
+  }
+  
+  
+  private Message convertKeyAndValueToMessage(K key, V value) {
+    return converter.convertKeyAndValueToMessage(key, value);
+  }
+  
+  @SuppressWarnings("unchecked")
+  private void convertMessageToKeyAndValue(Message message, Map<K, V> map) {
+    converter.convertMessageToKeyAndValue(message, map);
+  }
+
+  private List<Message> convertMapToList(Map<K, V> mapData) {
+    List<Message> listData = new ArrayList<Message>();
+    for (Map.Entry<K, V> entry : mapData.entrySet()) {
+      listData.add(
+          convertKeyAndValueToMessage(
+              entry.getKey(), entry.getValue()));
+    }
+    return listData;
+  }
+
+  private Map<K, V> convertListToMap(List<Message> listData) {
+    Map<K, V> mapData = new HashMap<K, V>();
+    for (Message item : listData) {
+      convertMessageToKeyAndValue(item, mapData);
+    }
+    return mapData;
+  }
+  
+  /** Returns the content of this MapField as a read-only Map. */
+  public Map<K, V> getMap() {
+    if (mode == StorageMode.LIST) {
+      synchronized (this) {
+        if (mode == StorageMode.LIST) {
+          mapData = convertListToMap(listData);
+          mode = StorageMode.BOTH;
+        }
+      }
+    }
+    return Collections.unmodifiableMap(mapData);
+  }
+  
+  /** Gets a mutable Map view of this MapField. */
+  public Map<K, V> getMutableMap() {
+    if (mode != StorageMode.MAP) {
+      if (mode == StorageMode.LIST) {
+        mapData = convertListToMap(listData);
+      }
+      listData = null;
+      mode = StorageMode.MAP; 
+    }
+    return mapData;
+  }
+  
+  public void mergeFrom(MapField<K, V> other) {
+    getMutableMap().putAll(MapFieldLite.copy(other.getMap()));
+  }
+  
+  public void clear() {
+    mapData = new HashMap<K, V>();
+    mode = StorageMode.MAP;
+  }
+  
+  @SuppressWarnings("unchecked")
+  @Override
+  public boolean equals(Object object) {
+    if (!(object instanceof MapField)) {
+      return false;
+    }
+    MapField<K, V> other = (MapField<K, V>) object;
+    return MapFieldLite.<K, V>equals(getMap(), other.getMap());
+  }
+  
+  @Override
+  public int hashCode() {
+    return MapFieldLite.<K, V>calculateHashCodeForMap(getMap());
+  }
+  
+  /** Returns a deep copy of this MapField. */
+  public MapField<K, V> copy() {
+    return new MapField<K, V>(
+        converter, StorageMode.MAP, MapFieldLite.copy(getMap()), null);
+  }
+  
+  /** Gets the content of this MapField as a read-only List. */
+  List<Message> getList() {
+    if (mode == StorageMode.MAP) {
+      synchronized (this) {
+        if (mode == StorageMode.MAP) {
+          listData = convertMapToList(mapData);
+          mode = StorageMode.BOTH;
+        }
+      }
+    }
+    return Collections.unmodifiableList(listData);
+  }
+  
+  /** Gets a mutable List view of this MapField. */
+  List<Message> getMutableList() {
+    if (mode != StorageMode.LIST) {
+      if (mode == StorageMode.MAP) {
+        listData = convertMapToList(mapData);
+      }
+      mapData = null;
+      mode = StorageMode.LIST;
+    }
+    return listData;
+  }
+  
+  /**
+   * Gets the default instance of the message stored in the list view of this
+   * map field.
+   */
+  Message getMapEntryMessageDefaultInstance() {
+    return converter.getMessageDefaultInstance();
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/MapFieldLite.java b/java/src/main/java/com/google/protobuf/MapFieldLite.java
new file mode 100644
index 00000000..eea36d9e
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/MapFieldLite.java
@@ -0,0 +1,182 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Internal representation of map fields in generated lite-runtime messages.
+ * 
+ * This class is a protobuf implementation detail. Users shouldn't use this
+ * class directly.
+ */
+public class MapFieldLite<K, V> {
+  private Map<K, V> mapData;
+  
+  private MapFieldLite(Map<K, V> mapData) {
+    this.mapData = mapData;
+  }
+  
+  @SuppressWarnings({"rawtypes", "unchecked"})
+  private static final MapFieldLite EMPTY_MAP_FIELD =
+      new MapFieldLite(Collections.emptyMap());
+  
+  /** Returns an singleton immutable empty MapFieldLite instance. */
+  @SuppressWarnings({"unchecked", "cast"})
+  public static <K, V> MapFieldLite<K, V> emptyMapField() {
+    return (MapFieldLite<K, V>) EMPTY_MAP_FIELD;
+  }
+  
+  /** Creates a new MapFieldLite instance. */
+  public static <K, V> MapFieldLite<K, V> newMapField() {
+    return new MapFieldLite<K, V>(new HashMap<K, V>());
+  }
+  
+  /** Gets the content of this MapField as a read-only Map. */
+  public Map<K, V> getMap() {
+    return Collections.unmodifiableMap(mapData);
+  }
+  
+  /** Gets a mutable Map view of this MapField. */
+  public Map<K, V> getMutableMap() {
+    return mapData;
+  }
+  
+  public void mergeFrom(MapFieldLite<K, V> other) {
+    mapData.putAll(copy(other.mapData));
+  }
+  
+  public void clear() {
+    mapData.clear();
+  }
+  
+  private static boolean equals(Object a, Object b) {
+    if (a instanceof byte[] && b instanceof byte[]) {
+      return Arrays.equals((byte[]) a, (byte[]) b);
+    }
+    return a.equals(b);
+  }
+  
+  /**
+   * Checks whether two {@link Map}s are equal. We don't use the default equals
+   * method of {@link Map} because it compares by identity not by content for
+   * byte arrays.
+   */
+  static <K, V> boolean equals(Map<K, V> a, Map<K, V> b) {
+    if (a == b) {
+      return true;
+    }
+    if (a.size() != a.size()) {
+      return false;
+    }
+    for (Map.Entry<K, V> entry : a.entrySet()) {
+      if (!b.containsKey(entry.getKey())) {
+        return false;
+      }
+      if (!equals(entry.getValue(), b.get(entry.getKey()))) {
+        return false;
+      }
+    }
+    return true;
+  }
+  
+  /**
+   * Checks whether two map fields are equal.
+   */
+  @SuppressWarnings("unchecked")
+  @Override
+  public boolean equals(Object object) {
+    if (!(object instanceof MapFieldLite)) {
+      return false;
+    }
+    MapFieldLite<K, V> other = (MapFieldLite<K, V>) object;
+    return equals(mapData, other.mapData);
+  }
+  
+  private static int calculateHashCodeForObject(Object a) {
+    if (a instanceof byte[]) {
+      return LiteralByteString.hashCode((byte[]) a);
+    }
+    if (a instanceof Internal.EnumLite) {
+      return Internal.hashEnum((Internal.EnumLite) a);
+    }
+    return a.hashCode();
+  }
+
+  /**
+   * Calculates the hash code for a {@link Map}. We don't use the default hash
+   * code method of {@link Map} because for byte arrays and protobuf enums it
+   * use {@link Object#hashCode()}.
+   */
+  static <K, V> int calculateHashCodeForMap(Map<K, V> a) {
+    int result = 0;
+    for (Map.Entry<K, V> entry : a.entrySet()) {
+      result += calculateHashCodeForObject(entry.getKey())
+          ^ calculateHashCodeForObject(entry.getValue());
+    }
+    return result;    
+  }
+  
+  @Override
+  public int hashCode() {
+    return calculateHashCodeForMap(mapData);
+  }
+  
+  private static Object copy(Object object) {
+    if (object instanceof byte[]) {
+      byte[] data = (byte[]) object;
+      return Arrays.copyOf(data, data.length);
+    }
+    return object;
+  }
+  
+  /**
+   * Makes a deep copy of a {@link Map}. Immutable objects in the map will be
+   * shared (e.g., integers, strings, immutable messages) and mutable ones will
+   * have a copy (e.g., byte arrays, mutable messages).
+   */
+  @SuppressWarnings("unchecked")
+  static <K, V> Map<K, V> copy(Map<K, V> map) {
+    Map<K, V> result = new HashMap<K, V>();
+    for (Map.Entry<K, V> entry : map.entrySet()) {
+      result.put(entry.getKey(), (V) copy(entry.getValue()));
+    }
+    return result;
+  }
+  
+  /** Returns a deep copy of this map field. */
+  public MapFieldLite<K, V> copy() {
+    return new MapFieldLite<K, V>(copy(mapData));
+  }
+}
diff --git a/java/src/main/java/com/google/protobuf/Message.java b/java/src/main/java/com/google/protobuf/Message.java
index 5673d3bb..5c75b58b 100644
--- a/java/src/main/java/com/google/protobuf/Message.java
+++ b/java/src/main/java/com/google/protobuf/Message.java
@@ -168,6 +168,25 @@ public interface Message extends MessageLite, MessageOrBuilder {
     Builder getFieldBuilder(Descriptors.FieldDescriptor field);
 
     /**
+     * Get a nested builder instance for the given repeated field instance.
+     * <p>
+     * Normally, we hold a reference to the immutable message object for the
+     * message type field. Some implementations(the generated message builders),
+     * however, can also hold a reference to the builder object (a nested
+     * builder) for the field.
+     * <p>
+     * If the field is already backed up by a nested builder, the nested builder
+     * will be returned. Otherwise, a new field builder will be created and
+     * returned. The original message field (if exist) will be merged into the
+     * field builder, which will then be nested into its parent builder.
+     * <p>
+     * NOTE: implementations that do not support nested builders will throw
+     * <code>UnsupportedException</code>.
+     */
+    Builder getRepeatedFieldBuilder(Descriptors.FieldDescriptor field,
+                                    int index);
+
+    /**
      * Sets a field to the given value.  The value must be of the correct type
      * for this field, i.e. the same type that
      * {@link Message#getField(Descriptors.FieldDescriptor)} would return.
diff --git a/java/src/main/java/com/google/protobuf/MessageReflection.java b/java/src/main/java/com/google/protobuf/MessageReflection.java
index edb5b5c2..06e3c99b 100644
--- a/java/src/main/java/com/google/protobuf/MessageReflection.java
+++ b/java/src/main/java/com/google/protobuf/MessageReflection.java
@@ -752,13 +752,18 @@ class MessageReflection {
       if (field.getLiteType() == WireFormat.FieldType.ENUM) {
         while (input.getBytesUntilLimit() > 0) {
           final int rawValue = input.readEnum();
-          final Object value = field.getEnumType().findValueByNumber(rawValue);
-          if (value == null) {
-            // If the number isn't recognized as a valid value for this
-            // enum, drop it (don't even add it to unknownFields).
-            return true;
+          if (field.getFile().supportsUnknownEnumValue()) {
+            target.addRepeatedField(field,
+                field.getEnumType().findValueByNumberCreatingIfUnknown(rawValue));
+          } else {
+            final Object value = field.getEnumType().findValueByNumber(rawValue);
+            if (value == null) {
+              // If the number isn't recognized as a valid value for this
+              // enum, drop it (don't even add it to unknownFields).
+              return true;
+            }
+            target.addRepeatedField(field, value);
           }
-          target.addRepeatedField(field, value);
         }
       } else {
         while (input.getBytesUntilLimit() > 0) {
@@ -783,12 +788,16 @@ class MessageReflection {
         }
         case ENUM:
           final int rawValue = input.readEnum();
-          value = field.getEnumType().findValueByNumber(rawValue);
-          // If the number isn't recognized as a valid value for this enum,
-          // drop it.
-          if (value == null) {
-            unknownFields.mergeVarintField(fieldNumber, rawValue);
-            return true;
+          if (field.getFile().supportsUnknownEnumValue()) {
+            value = field.getEnumType().findValueByNumberCreatingIfUnknown(rawValue);
+          } else {
+            value = field.getEnumType().findValueByNumber(rawValue);
+            // If the number isn't recognized as a valid value for this enum,
+            // drop it.
+            if (value == null) {
+              unknownFields.mergeVarintField(fieldNumber, rawValue);
+              return true;
+            }
           }
           break;
         default:
diff --git a/java/src/main/java/com/google/protobuf/RepeatedFieldBuilder.java b/java/src/main/java/com/google/protobuf/RepeatedFieldBuilder.java
index 22760d3a..63535ac8 100644
--- a/java/src/main/java/com/google/protobuf/RepeatedFieldBuilder.java
+++ b/java/src/main/java/com/google/protobuf/RepeatedFieldBuilder.java
@@ -367,22 +367,28 @@ public class RepeatedFieldBuilder
         throw new NullPointerException();
       }
     }
+
+    // If we can inspect the size, we can more efficiently add messages.
+    int size = -1;
     if (values instanceof Collection) {
       @SuppressWarnings("unchecked") final
       Collection<MType> collection = (Collection<MType>) values;
       if (collection.size() == 0) {
         return this;
       }
-      ensureMutableMessageList();
-      for (MType value : values) {
-        addMessage(value);
-      }
-    } else {
-      ensureMutableMessageList();
-      for (MType value : values) {
-        addMessage(value);
-      }
+      size = collection.size();
+    }
+    ensureMutableMessageList();
+
+    if (size >= 0 && messages instanceof ArrayList) {
+      ((ArrayList<MType>) messages)
+          .ensureCapacity(messages.size() + size);
     }
+
+    for (MType value : values) {
+      addMessage(value);
+    }
+
     onChanged();
     incrementModCounts();
     return this;
diff --git a/java/src/main/java/com/google/protobuf/TextFormat.java b/java/src/main/java/com/google/protobuf/TextFormat.java
index 57d0ca68..44674811 100644
--- a/java/src/main/java/com/google/protobuf/TextFormat.java
+++ b/java/src/main/java/com/google/protobuf/TextFormat.java
@@ -1211,6 +1211,7 @@ public final class TextFormat {
       private SingularOverwritePolicy singularOverwritePolicy =
           SingularOverwritePolicy.ALLOW_SINGULAR_OVERWRITES;
 
+
       /**
        * Sets parser behavior when a non-repeated field appears more than once.
        */
@@ -1418,6 +1419,12 @@ public final class TextFormat {
       } else {
         consumeFieldValue(tokenizer, extensionRegistry, target, field, extension);
       }
+
+      // For historical reasons, fields may optionally be separated by commas or
+      // semicolons.
+      if (!tokenizer.tryConsume(";")) {
+        tokenizer.tryConsume(",");
+      }
     }
 
     /**
@@ -1656,10 +1663,9 @@ public final class TextFormat {
         case '\'': builder.append("\\\'"); break;
         case '"' : builder.append("\\\""); break;
         default:
-          // Note:  Bytes with the high-order bit set should be escaped.  Since
-          //   bytes are signed, such bytes will compare less than 0x20, hence
-          //   the following line is correct.
-          if (b >= 0x20) {
+          // Only ASCII characters between 0x20 (space) and 0x7e (tilde) are
+          // printable.  Other byte values must be escaped.
+          if (b >= 0x20 && b <= 0x7e) {
             builder.append((char) b);
           } else {
             builder.append('\\');
diff --git a/java/src/main/java/com/google/protobuf/UnknownFieldSet.java b/java/src/main/java/com/google/protobuf/UnknownFieldSet.java
index 99de3732..7cd2250e 100644
--- a/java/src/main/java/com/google/protobuf/UnknownFieldSet.java
+++ b/java/src/main/java/com/google/protobuf/UnknownFieldSet.java
@@ -431,6 +431,21 @@ public final class UnknownFieldSet implements MessageLite {
       return this;
     }
 
+
+    /**
+     * Convenience method for merging a length-delimited field.
+     *
+     * <p>For use by generated code only.
+     */
+    public Builder mergeLengthDelimitedField(
+        final int number, final ByteString value) {  
+      if (number == 0) {
+        throw new IllegalArgumentException("Zero is not a valid field number.");
+      }
+      getFieldBuilder(number).addLengthDelimited(value);
+      return this;
+    }
+
     /** Check if the given field number is present in the set. */
     public boolean hasField(final int number) {
       if (number == 0) {
diff --git a/java/src/main/java/com/google/protobuf/UnknownFieldSetLite.java b/java/src/main/java/com/google/protobuf/UnknownFieldSetLite.java
new file mode 100644
index 00000000..7ea84022
--- /dev/null
+++ b/java/src/main/java/com/google/protobuf/UnknownFieldSetLite.java
@@ -0,0 +1,297 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import java.io.IOException;
+
+/**
+ * {@code UnknownFieldSetLite} is used to keep track of fields which were seen
+ * when parsing a protocol message but whose field numbers or types are
+ * unrecognized. This most frequently occurs when new fields are added to a
+ * message type and then messages containing those fields are read by old
+ * software that was compiled before the new types were added.
+ *
+ * <p>For use by generated code only.
+ *
+ * @author dweis@google.com (Daniel Weis)
+ */
+public final class UnknownFieldSetLite {
+
+  private static final UnknownFieldSetLite DEFAULT_INSTANCE =
+      new UnknownFieldSetLite(ByteString.EMPTY);
+
+  /**
+   * Get an empty {@code UnknownFieldSetLite}.
+   *
+   * <p>For use by generated code only.
+   */
+  public static UnknownFieldSetLite getDefaultInstance() {
+    return DEFAULT_INSTANCE;
+  }
+
+  /**
+   * Create a new {@link Builder}.
+   *
+   * <p>For use by generated code only.
+   */
+  public static Builder newBuilder() {
+    return new Builder();
+  }
+
+  /**
+   * Returns an {@code UnknownFieldSetLite} that is the composite of {@code first} and
+   * {@code second}.
+   */
+  static UnknownFieldSetLite concat(UnknownFieldSetLite first, UnknownFieldSetLite second) {
+    return new UnknownFieldSetLite(first.byteString.concat(second.byteString));
+  }
+
+  /**
+   * The internal representation of the unknown fields.
+   */
+  private final ByteString byteString;
+
+  /**
+   * Constructs the {@code UnknownFieldSetLite} as a thin wrapper around {@link ByteString}.
+   */
+  private UnknownFieldSetLite(ByteString byteString) {
+    this.byteString = byteString;
+  }
+
+  /**
+   * Serializes the set and writes it to {@code output}.
+   *
+   * <p>For use by generated code only.
+   */
+  public void writeTo(CodedOutputStream output) throws IOException {
+    output.writeRawBytes(byteString);
+  }
+
+
+  /**
+   * Get the number of bytes required to encode this set.
+   *
+   * <p>For use by generated code only.
+   */
+  public int getSerializedSize() {
+    return byteString.size();
+  }
+
+  @Override
+  public boolean equals(Object obj) {
+    if (this == obj) {
+      return true;
+    }
+
+    if (obj instanceof UnknownFieldSetLite) {
+      return byteString.equals(((UnknownFieldSetLite) obj).byteString);
+    }
+
+    return false;
+  }
+
+  @Override
+  public int hashCode() {
+    return byteString.hashCode();
+  }
+
+  /**
+   * Builder for {@link UnknownFieldSetLite}s.
+   *
+   * <p>Use {@link UnknownFieldSet#newBuilder()} to construct a {@code Builder}.
+   *
+   * <p>For use by generated code only.
+   */
+  public static final class Builder {
+
+    private ByteString.Output byteStringOutput;
+    private CodedOutputStream output;
+    private boolean built;
+
+    /**
+     * Constructs a {@code Builder}. Lazily initialized by
+     * {@link #ensureInitializedButNotBuilt()}.
+     */
+    private Builder() {}
+
+    /**
+     * Ensures internal state is initialized for use.
+     */
+    private void ensureInitializedButNotBuilt() {
+      if (built) {
+        throw new IllegalStateException("Do not reuse UnknownFieldSetLite Builders.");
+      }
+
+      if (output == null && byteStringOutput == null) {
+          byteStringOutput = ByteString.newOutput(100 /* initialCapacity */);
+          output = CodedOutputStream.newInstance(byteStringOutput);
+      }
+    }
+
+    /**
+     * Parse a single field from {@code input} and merge it into this set.
+     *
+     * <p>For use by generated code only.
+     *
+     * @param tag The field's tag number, which was already parsed.
+     * @return {@code false} if the tag is an end group tag.
+     */
+    public boolean mergeFieldFrom(final int tag, final CodedInputStream input)
+                                  throws IOException {
+      ensureInitializedButNotBuilt();
+
+      final int fieldNumber = WireFormat.getTagFieldNumber(tag);
+      switch (WireFormat.getTagWireType(tag)) {
+        case WireFormat.WIRETYPE_VARINT:
+          output.writeUInt64(fieldNumber, input.readInt64());
+          return true;
+        case WireFormat.WIRETYPE_FIXED32:
+          output.writeFixed32(fieldNumber, input.readFixed32());
+          return true;
+        case WireFormat.WIRETYPE_FIXED64:
+          output.writeFixed64(fieldNumber, input.readFixed64());
+          return true;
+        case WireFormat.WIRETYPE_LENGTH_DELIMITED:
+          output.writeBytes(fieldNumber, input.readBytes());
+          return true;
+        case WireFormat.WIRETYPE_START_GROUP:
+          final Builder subBuilder = newBuilder();
+          subBuilder.mergeFrom(input);
+          input.checkLastTagWas(
+              WireFormat.makeTag(fieldNumber, WireFormat.WIRETYPE_END_GROUP));
+
+          output.writeTag(fieldNumber, WireFormat.WIRETYPE_START_GROUP);
+          subBuilder.build().writeTo(output);
+          output.writeTag(fieldNumber, WireFormat.WIRETYPE_END_GROUP);
+          return true;
+        case WireFormat.WIRETYPE_END_GROUP:
+          return false;
+        default:
+          throw InvalidProtocolBufferException.invalidWireType();
+      }
+    }
+
+    /**
+     * Convenience method for merging a new field containing a single varint
+     * value. This is used in particular when an unknown enum value is
+     * encountered.
+     *
+     * <p>For use by generated code only.
+     */
+    public Builder mergeVarintField(int fieldNumber, int value) {
+      if (fieldNumber == 0) {
+        throw new IllegalArgumentException("Zero is not a valid field number.");
+      }
+      ensureInitializedButNotBuilt();
+      try {
+        output.writeUInt64(fieldNumber, value);
+      } catch (IOException e) {
+        // Should never happen.
+      }
+      return this;
+    }
+
+    /**
+     * Convenience method for merging a length-delimited field.
+     *
+     * <p>For use by generated code only.
+     */
+    public Builder mergeLengthDelimitedField(
+        final int fieldNumber, final ByteString value) {  
+      if (fieldNumber == 0) {
+        throw new IllegalArgumentException("Zero is not a valid field number.");
+      }
+      ensureInitializedButNotBuilt();
+      try {
+        output.writeBytes(fieldNumber, value);
+      } catch (IOException e) {
+        // Should never happen.
+      }
+      return this;
+    }
+
+    /**
+     * Build the {@link UnknownFieldSetLite} and return it.
+     *
+     * <p>Once {@code build()} has been called, the {@code Builder} will no
+     * longer be usable.  Calling any method after {@code build()} will result
+     * in undefined behavior and can cause a {@code IllegalStateException} to be
+     * thrown.
+     *
+     * <p>For use by generated code only.
+     */
+    public UnknownFieldSetLite build() {
+      if (built) {
+        throw new IllegalStateException("Do not reuse UnknownFieldSetLite Builders.");
+      }
+
+      built = true;
+
+      final UnknownFieldSetLite result;
+      // If we were never initialized, no data was written.
+      if (output == null) {
+        result = getDefaultInstance();
+      } else {
+        try {
+          output.flush();
+        } catch (IOException e) {
+          // Should never happen.
+        }
+        ByteString byteString = byteStringOutput.toByteString();
+        if (byteString.isEmpty()) {
+          result = getDefaultInstance();
+        } else {
+          result = new UnknownFieldSetLite(byteString);
+        }
+      }
+
+      // Allow for garbage collection.
+      output = null;
+      byteStringOutput = null;
+      return result;
+    }
+
+    /**
+     * Parse an entire message from {@code input} and merge its fields into
+     * this set.
+     */
+    private Builder mergeFrom(final CodedInputStream input) throws IOException {
+      // Ensures initialization in mergeFieldFrom.
+      while (true) {
+        final int tag = input.readTag();
+        if (tag == 0 || !mergeFieldFrom(tag, input)) {
+          break;
+        }
+      }
+      return this;
+    }
+  }
+}
diff --git a/java/src/test/java/com/google/protobuf/CodedInputStreamTest.java b/java/src/test/java/com/google/protobuf/CodedInputStreamTest.java
index 3f656e25..18d8142c 100644
--- a/java/src/test/java/com/google/protobuf/CodedInputStreamTest.java
+++ b/java/src/test/java/com/google/protobuf/CodedInputStreamTest.java
@@ -455,19 +455,19 @@ public class CodedInputStreamTest extends TestCase {
   }
 
   public void testMaliciousRecursion() throws Exception {
-    ByteString data64 = makeRecursiveMessage(64).toByteString();
-    ByteString data65 = makeRecursiveMessage(65).toByteString();
+    ByteString data100 = makeRecursiveMessage(100).toByteString();
+    ByteString data101 = makeRecursiveMessage(101).toByteString();
 
-    assertMessageDepth(TestRecursiveMessage.parseFrom(data64), 64);
+    assertMessageDepth(TestRecursiveMessage.parseFrom(data100), 100);
 
     try {
-      TestRecursiveMessage.parseFrom(data65);
+      TestRecursiveMessage.parseFrom(data101);
       fail("Should have thrown an exception!");
     } catch (InvalidProtocolBufferException e) {
       // success.
     }
 
-    CodedInputStream input = data64.newCodedInput();
+    CodedInputStream input = data100.newCodedInput();
     input.setRecursionLimit(8);
     try {
       TestRecursiveMessage.parseFrom(input);
diff --git a/java/src/test/java/com/google/protobuf/DescriptorsTest.java b/java/src/test/java/com/google/protobuf/DescriptorsTest.java
index 0092771b..05832a12 100644
--- a/java/src/test/java/com/google/protobuf/DescriptorsTest.java
+++ b/java/src/test/java/com/google/protobuf/DescriptorsTest.java
@@ -706,6 +706,12 @@ public class DescriptorsTest extends TestCase {
     assertTrue(TestMultipleExtensionRanges.getDescriptor().isExtensionNumber(4143));
   }
 
+  public void testToString() {
+    assertEquals("protobuf_unittest.TestAllTypes.optional_uint64",
+        UnittestProto.TestAllTypes.getDescriptor().findFieldByNumber(
+            UnittestProto.TestAllTypes.OPTIONAL_UINT64_FIELD_NUMBER).toString());
+  }
+
   public void testPackedEnumField() throws Exception {
     FileDescriptorProto fileDescriptorProto = FileDescriptorProto.newBuilder()
         .setName("foo.proto")
diff --git a/java/src/test/java/com/google/protobuf/FieldPresenceTest.java b/java/src/test/java/com/google/protobuf/FieldPresenceTest.java
new file mode 100644
index 00000000..acf2b023
--- /dev/null
+++ b/java/src/test/java/com/google/protobuf/FieldPresenceTest.java
@@ -0,0 +1,363 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+import com.google.protobuf.FieldPresenceTestProto.TestAllTypes;
+import com.google.protobuf.FieldPresenceTestProto.TestOptionalFieldsOnly;
+import com.google.protobuf.FieldPresenceTestProto.TestRepeatedFieldsOnly;
+import protobuf_unittest.UnittestProto;
+
+import junit.framework.TestCase;
+
+/**
+ * Unit tests for protos that doesn't support field presence test for optional
+ * non-message fields.
+ */
+public class FieldPresenceTest extends TestCase {
+  private static boolean hasMethod(Class clazz, String name) {
+    try {
+      if (clazz.getMethod(name, new Class[]{}) != null) {
+        return true;
+      } else {
+        return false;
+      }
+    } catch (NoSuchMethodException e) {
+      return false;
+    }
+  }
+
+  private static boolean isHasMethodRemoved(
+      Class classWithFieldPresence,
+      Class classWithoutFieldPresence,
+      String camelName) {
+    return hasMethod(classWithFieldPresence, "get" + camelName)
+        && hasMethod(classWithFieldPresence, "has" + camelName)
+        && hasMethod(classWithoutFieldPresence, "get" + camelName)
+        && !hasMethod(classWithoutFieldPresence, "has" + camelName);
+  }
+
+  public void testHasMethod() {
+    // Optional non-message fields don't have a hasFoo() method generated.
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.class,
+        TestAllTypes.class,
+        "OptionalInt32"));
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.class,
+        TestAllTypes.class,
+        "OptionalString"));
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.class,
+        TestAllTypes.class,
+        "OptionalBytes"));
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.class,
+        TestAllTypes.class,
+        "OptionalNestedEnum"));
+
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.Builder.class,
+        TestAllTypes.Builder.class,
+        "OptionalInt32"));
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.Builder.class,
+        TestAllTypes.Builder.class,
+        "OptionalString"));
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.Builder.class,
+        TestAllTypes.Builder.class,
+        "OptionalBytes"));
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.Builder.class,
+        TestAllTypes.Builder.class,
+        "OptionalNestedEnum"));
+
+    // message fields still have the hasFoo() method generated.
+    assertFalse(TestAllTypes.newBuilder().build().hasOptionalNestedMessage());
+    assertFalse(TestAllTypes.newBuilder().hasOptionalNestedMessage());
+
+    // oneof fields don't have hasFoo() methods (even for message types).
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.class,
+        TestAllTypes.class,
+        "OneofUint32"));
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.class,
+        TestAllTypes.class,
+        "OneofString"));
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.class,
+        TestAllTypes.class,
+        "OneofBytes"));
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.class,
+        TestAllTypes.class,
+        "OneofNestedMessage"));
+
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.Builder.class,
+        TestAllTypes.Builder.class,
+        "OneofUint32"));
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.Builder.class,
+        TestAllTypes.Builder.class,
+        "OneofString"));
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.Builder.class,
+        TestAllTypes.Builder.class,
+        "OneofBytes"));
+    assertTrue(isHasMethodRemoved(
+        UnittestProto.TestAllTypes.Builder.class,
+        TestAllTypes.Builder.class,
+        "OneofNestedMessage"));
+  }
+
+  public void testFieldPresence() {
+    // Optional non-message fields set to their default value are treated the
+    // same way as not set.
+
+    // Serialization will ignore such fields.
+    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
+    builder.setOptionalInt32(0);
+    builder.setOptionalString("");
+    builder.setOptionalBytes(ByteString.EMPTY);
+    builder.setOptionalNestedEnum(TestAllTypes.NestedEnum.FOO);
+    TestAllTypes message = builder.build();
+    assertEquals(0, message.getSerializedSize());
+
+    // mergeFrom() will ignore such fields.
+    TestAllTypes.Builder a = TestAllTypes.newBuilder();
+    a.setOptionalInt32(1);
+    a.setOptionalString("x");
+    a.setOptionalBytes(ByteString.copyFromUtf8("y"));
+    a.setOptionalNestedEnum(TestAllTypes.NestedEnum.BAR);
+    TestAllTypes.Builder b = TestAllTypes.newBuilder();
+    b.setOptionalInt32(0);
+    b.setOptionalString("");
+    b.setOptionalBytes(ByteString.EMPTY);
+    b.setOptionalNestedEnum(TestAllTypes.NestedEnum.FOO);
+    a.mergeFrom(b.build());
+    message = a.build();
+    assertEquals(1, message.getOptionalInt32());
+    assertEquals("x", message.getOptionalString());
+    assertEquals(ByteString.copyFromUtf8("y"), message.getOptionalBytes());
+    assertEquals(TestAllTypes.NestedEnum.BAR, message.getOptionalNestedEnum());
+
+    // equals()/hashCode() should produce the same results.
+    TestAllTypes empty = TestAllTypes.newBuilder().build();
+    message = builder.build();
+    assertTrue(empty.equals(message));
+    assertTrue(message.equals(empty));
+    assertEquals(empty.hashCode(), message.hashCode());
+  }
+
+  public void testFieldPresenceByReflection() {
+    Descriptor descriptor = TestAllTypes.getDescriptor();
+    FieldDescriptor optionalInt32Field = descriptor.findFieldByName("optional_int32");
+    FieldDescriptor optionalStringField = descriptor.findFieldByName("optional_string");
+    FieldDescriptor optionalBytesField = descriptor.findFieldByName("optional_bytes");
+    FieldDescriptor optionalNestedEnumField = descriptor.findFieldByName("optional_nested_enum");
+
+    // Field not present.
+    TestAllTypes message = TestAllTypes.newBuilder().build();
+    assertFalse(message.hasField(optionalInt32Field));
+    assertFalse(message.hasField(optionalStringField));
+    assertFalse(message.hasField(optionalBytesField));
+    assertFalse(message.hasField(optionalNestedEnumField));
+    assertEquals(0, message.getAllFields().size());
+
+    // Field set to default value is seen as not present.
+    message = TestAllTypes.newBuilder()
+        .setOptionalInt32(0)
+        .setOptionalString("")
+        .setOptionalBytes(ByteString.EMPTY)
+        .setOptionalNestedEnum(TestAllTypes.NestedEnum.FOO)
+        .build();
+    assertFalse(message.hasField(optionalInt32Field));
+    assertFalse(message.hasField(optionalStringField));
+    assertFalse(message.hasField(optionalBytesField));
+    assertFalse(message.hasField(optionalNestedEnumField));
+    assertEquals(0, message.getAllFields().size());
+
+    // Field set to non-default value is seen as present.
+    message = TestAllTypes.newBuilder()
+        .setOptionalInt32(1)
+        .setOptionalString("x")
+        .setOptionalBytes(ByteString.copyFromUtf8("y"))
+        .setOptionalNestedEnum(TestAllTypes.NestedEnum.BAR)
+        .build();
+    assertTrue(message.hasField(optionalInt32Field));
+    assertTrue(message.hasField(optionalStringField));
+    assertTrue(message.hasField(optionalBytesField));
+    assertTrue(message.hasField(optionalNestedEnumField));
+    assertEquals(4, message.getAllFields().size());
+  }
+  
+  public void testMessageField() {
+    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
+    assertFalse(builder.hasOptionalNestedMessage());
+    assertFalse(builder.build().hasOptionalNestedMessage());
+    
+    TestAllTypes.NestedMessage.Builder nestedBuilder =
+        builder.getOptionalNestedMessageBuilder();
+    assertTrue(builder.hasOptionalNestedMessage());
+    assertTrue(builder.build().hasOptionalNestedMessage());
+    
+    nestedBuilder.setValue(1);
+    assertEquals(1, builder.build().getOptionalNestedMessage().getValue());
+    
+    builder.clearOptionalNestedMessage();
+    assertFalse(builder.hasOptionalNestedMessage());
+    assertFalse(builder.build().hasOptionalNestedMessage());
+    
+    // Unlike non-message fields, if we set a message field to its default value (i.e.,
+    // default instance), the field should be seen as present.
+    builder.setOptionalNestedMessage(TestAllTypes.NestedMessage.getDefaultInstance());
+    assertTrue(builder.hasOptionalNestedMessage());
+    assertTrue(builder.build().hasOptionalNestedMessage());
+  }
+
+  public void testSerializeAndParse() throws Exception {
+    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
+    builder.setOptionalInt32(1234);
+    builder.setOptionalString("hello");
+    builder.setOptionalNestedMessage(TestAllTypes.NestedMessage.getDefaultInstance());
+    // Set an oneof field to its default value and expect it to be serialized (i.e.,
+    // an oneof field set to the default value should be treated as present).
+    builder.setOneofInt32(0);
+    ByteString data = builder.build().toByteString();
+
+    TestAllTypes message = TestAllTypes.parseFrom(data);
+    assertEquals(1234, message.getOptionalInt32());
+    assertEquals("hello", message.getOptionalString());
+    // Fields not set will have the default value.
+    assertEquals(ByteString.EMPTY, message.getOptionalBytes());
+    assertEquals(TestAllTypes.NestedEnum.FOO, message.getOptionalNestedEnum());
+    // The message field is set despite that it's set with a default instance.
+    assertTrue(message.hasOptionalNestedMessage());
+    assertEquals(0, message.getOptionalNestedMessage().getValue());
+    // The oneof field set to its default value is also present.
+    assertEquals(
+        TestAllTypes.OneofFieldCase.ONEOF_INT32, message.getOneofFieldCase());
+  }
+
+  // Regression test for b/16173397
+  // Make sure we haven't screwed up the code generation for repeated fields.
+  public void testRepeatedFields() throws Exception {
+    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
+    builder.setOptionalInt32(1234);
+    builder.setOptionalString("hello");
+    builder.setOptionalNestedMessage(TestAllTypes.NestedMessage.getDefaultInstance());
+    builder.addRepeatedInt32(4321);
+    builder.addRepeatedString("world");
+    builder.addRepeatedNestedMessage(TestAllTypes.NestedMessage.getDefaultInstance());
+    ByteString data = builder.build().toByteString();
+
+    TestOptionalFieldsOnly optionalOnlyMessage = TestOptionalFieldsOnly.parseFrom(data);
+    assertEquals(1234, optionalOnlyMessage.getOptionalInt32());
+    assertEquals("hello", optionalOnlyMessage.getOptionalString());
+    assertTrue(optionalOnlyMessage.hasOptionalNestedMessage());
+    assertEquals(0, optionalOnlyMessage.getOptionalNestedMessage().getValue());
+
+    TestRepeatedFieldsOnly repeatedOnlyMessage = TestRepeatedFieldsOnly.parseFrom(data);
+    assertEquals(1, repeatedOnlyMessage.getRepeatedInt32Count());
+    assertEquals(4321, repeatedOnlyMessage.getRepeatedInt32(0));
+    assertEquals(1, repeatedOnlyMessage.getRepeatedStringCount());
+    assertEquals("world", repeatedOnlyMessage.getRepeatedString(0));
+    assertEquals(1, repeatedOnlyMessage.getRepeatedNestedMessageCount());
+    assertEquals(0, repeatedOnlyMessage.getRepeatedNestedMessage(0).getValue());
+  }
+
+  public void testIsInitialized() throws Exception {
+    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
+
+    // Test optional proto2 message fields.
+    UnittestProto.TestRequired.Builder proto2Builder =
+        builder.getOptionalProto2MessageBuilder();
+    assertFalse(builder.isInitialized());
+    assertFalse(builder.buildPartial().isInitialized());
+
+    proto2Builder.setA(1).setB(2).setC(3);
+    assertTrue(builder.isInitialized());
+    assertTrue(builder.buildPartial().isInitialized());
+
+    // Test oneof proto2 message fields.
+    proto2Builder = builder.getOneofProto2MessageBuilder();
+    assertFalse(builder.isInitialized());
+    assertFalse(builder.buildPartial().isInitialized());
+
+    proto2Builder.setA(1).setB(2).setC(3);
+    assertTrue(builder.isInitialized());
+    assertTrue(builder.buildPartial().isInitialized());
+
+    // Test repeated proto2 message fields.
+    proto2Builder = builder.addRepeatedProto2MessageBuilder();
+    assertFalse(builder.isInitialized());
+    assertFalse(builder.buildPartial().isInitialized());
+
+    proto2Builder.setA(1).setB(2).setC(3);
+    assertTrue(builder.isInitialized());
+    assertTrue(builder.buildPartial().isInitialized());
+  }
+
+  
+  // Test that unknown fields are dropped.
+  public void testUnknownFields() throws Exception {
+    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
+    builder.setOptionalInt32(1234);
+    builder.addRepeatedInt32(5678);
+    TestAllTypes message = builder.build();
+    ByteString data = message.toByteString();
+    
+    TestOptionalFieldsOnly optionalOnlyMessage =
+        TestOptionalFieldsOnly.parseFrom(data);
+    // UnknownFieldSet should be empty.
+    assertEquals(
+        0, optionalOnlyMessage.getUnknownFields().toByteString().size());
+    assertEquals(1234, optionalOnlyMessage.getOptionalInt32());
+    message = TestAllTypes.parseFrom(optionalOnlyMessage.toByteString());
+    assertEquals(1234, message.getOptionalInt32());
+    // The repeated field is discarded because it's unknown to the optional-only
+    // message.
+    assertEquals(0, message.getRepeatedInt32Count());
+    
+    DynamicMessage dynamicOptionalOnlyMessage =
+        DynamicMessage.getDefaultInstance(
+            TestOptionalFieldsOnly.getDescriptor())
+        .getParserForType().parseFrom(data);
+    assertEquals(
+        0, dynamicOptionalOnlyMessage.getUnknownFields().toByteString().size());
+    assertEquals(optionalOnlyMessage.toByteString(),
+        dynamicOptionalOnlyMessage.toByteString());
+  }
+}
diff --git a/java/src/test/java/com/google/protobuf/GeneratedMessageTest.java b/java/src/test/java/com/google/protobuf/GeneratedMessageTest.java
index 0b3482c3..41ed7bd0 100644
--- a/java/src/test/java/com/google/protobuf/GeneratedMessageTest.java
+++ b/java/src/test/java/com/google/protobuf/GeneratedMessageTest.java
@@ -157,15 +157,12 @@ public class GeneratedMessageTest extends TestCase {
   public void testProtosShareRepeatedArraysIfDidntChange() throws Exception {
     TestAllTypes.Builder builder = TestAllTypes.newBuilder();
     builder.addRepeatedInt32(100);
-    builder.addRepeatedImportEnum(UnittestImport.ImportEnum.IMPORT_BAR);
     builder.addRepeatedForeignMessage(ForeignMessage.getDefaultInstance());
 
     TestAllTypes value1 = builder.build();
     TestAllTypes value2 = value1.toBuilder().build();
 
     assertSame(value1.getRepeatedInt32List(), value2.getRepeatedInt32List());
-    assertSame(value1.getRepeatedImportEnumList(),
-        value2.getRepeatedImportEnumList());
     assertSame(value1.getRepeatedForeignMessageList(),
         value2.getRepeatedForeignMessageList());
   }
@@ -1512,4 +1509,142 @@ public class GeneratedMessageTest extends TestCase {
       assertEquals(message2.getFooMessage().getQuxInt(), 234);
     }
   }
+
+  public void testGetRepeatedFieldBuilder() {
+    Descriptor descriptor = TestAllTypes.getDescriptor();
+
+    FieldDescriptor fieldDescriptor =
+        descriptor.findFieldByName("repeated_nested_message");
+    FieldDescriptor foreignFieldDescriptor =
+        descriptor.findFieldByName("repeated_foreign_message");
+    FieldDescriptor importFieldDescriptor =
+        descriptor.findFieldByName("repeated_import_message");
+
+    // Mutate the message with new field builder
+    // Mutate nested message
+    TestAllTypes.Builder builder1 = TestAllTypes.newBuilder();
+    Message.Builder fieldBuilder1 = builder1.newBuilderForField(
+        fieldDescriptor);
+    FieldDescriptor subFieldDescriptor1 =
+        fieldBuilder1.getDescriptorForType().findFieldByName("bb");
+    fieldBuilder1.setField(subFieldDescriptor1, 1);
+    builder1.addRepeatedField(fieldDescriptor, fieldBuilder1.build());
+
+    // Mutate foreign message
+    Message.Builder foreignFieldBuilder1 = builder1.newBuilderForField(
+        foreignFieldDescriptor);
+    FieldDescriptor subForeignFieldDescriptor1 =
+        foreignFieldBuilder1.getDescriptorForType().findFieldByName("c");
+    foreignFieldBuilder1.setField(subForeignFieldDescriptor1, 2);
+    builder1.addRepeatedField(foreignFieldDescriptor,
+        foreignFieldBuilder1.build());
+
+    // Mutate import message
+    Message.Builder importFieldBuilder1 = builder1.newBuilderForField(
+        importFieldDescriptor);
+    FieldDescriptor subImportFieldDescriptor1 =
+        importFieldBuilder1.getDescriptorForType().findFieldByName("d");
+    importFieldBuilder1.setField(subImportFieldDescriptor1, 3);
+    builder1.addRepeatedField(importFieldDescriptor,
+        importFieldBuilder1.build());
+
+    Message newMessage1 = builder1.build();
+
+    // Mutate the message with existing field builder
+    // Mutate nested message
+    TestAllTypes.Builder builder2 = TestAllTypes.newBuilder();
+    builder2.addRepeatedNestedMessageBuilder();
+    Message.Builder fieldBuilder2 = builder2.getRepeatedFieldBuilder(
+        fieldDescriptor, 0);
+    FieldDescriptor subFieldDescriptor2 =
+        fieldBuilder2.getDescriptorForType().findFieldByName("bb");
+    fieldBuilder2.setField(subFieldDescriptor2, 1);
+
+    // Mutate foreign message
+    Message.Builder foreignFieldBuilder2 = builder2.newBuilderForField(
+        foreignFieldDescriptor);
+    FieldDescriptor subForeignFieldDescriptor2 =
+        foreignFieldBuilder2.getDescriptorForType().findFieldByName("c");
+    foreignFieldBuilder2.setField(subForeignFieldDescriptor2, 2);
+    builder2.addRepeatedField(foreignFieldDescriptor,
+        foreignFieldBuilder2.build());
+
+    // Mutate import message
+    Message.Builder importFieldBuilder2 = builder2.newBuilderForField(
+        importFieldDescriptor);
+    FieldDescriptor subImportFieldDescriptor2 =
+        importFieldBuilder2.getDescriptorForType().findFieldByName("d");
+    importFieldBuilder2.setField(subImportFieldDescriptor2, 3);
+    builder2.addRepeatedField(importFieldDescriptor,
+        importFieldBuilder2.build());
+
+    Message newMessage2 = builder2.build();
+
+    // These two messages should be equal.
+    assertEquals(newMessage1, newMessage2);
+  }
+
+  public void testGetRepeatedFieldBuilderWithInitializedValue() {
+    Descriptor descriptor = TestAllTypes.getDescriptor();
+    FieldDescriptor fieldDescriptor =
+        descriptor.findFieldByName("repeated_nested_message");
+
+    // Before setting field, builder is initialized by default value. 
+    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
+    builder.addRepeatedNestedMessageBuilder();
+    NestedMessage.Builder fieldBuilder =
+        (NestedMessage.Builder) builder.getRepeatedFieldBuilder(fieldDescriptor, 0);
+    assertEquals(0, fieldBuilder.getBb());
+
+    // Setting field value with new field builder instance.
+    builder = TestAllTypes.newBuilder();
+    NestedMessage.Builder newFieldBuilder =
+        builder.addRepeatedNestedMessageBuilder();
+    newFieldBuilder.setBb(2);
+    // Then get the field builder instance by getRepeatedFieldBuilder().
+    fieldBuilder =
+        (NestedMessage.Builder) builder.getRepeatedFieldBuilder(fieldDescriptor, 0);
+    // It should contain new value.
+    assertEquals(2, fieldBuilder.getBb());
+    // These two builder should be equal.
+    assertSame(fieldBuilder, newFieldBuilder);
+  }
+
+  public void testGetRepeatedFieldBuilderNotSupportedException() {
+    Descriptor descriptor = TestAllTypes.getDescriptor();
+    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
+    try {
+      builder.getRepeatedFieldBuilder(descriptor.findFieldByName("repeated_int32"), 0);
+      fail("Exception was not thrown");
+    } catch (UnsupportedOperationException e) {
+      // We expect this exception.
+    }
+    try {
+      builder.getRepeatedFieldBuilder(
+          descriptor.findFieldByName("repeated_nested_enum"), 0);
+      fail("Exception was not thrown");
+    } catch (UnsupportedOperationException e) {
+      // We expect this exception.
+    }
+    try {
+      builder.getRepeatedFieldBuilder(descriptor.findFieldByName("optional_int32"), 0);
+      fail("Exception was not thrown");
+    } catch (UnsupportedOperationException e) {
+      // We expect this exception.
+    }
+    try {
+      builder.getRepeatedFieldBuilder(
+          descriptor.findFieldByName("optional_nested_enum"), 0);
+      fail("Exception was not thrown");
+    } catch (UnsupportedOperationException e) {
+      // We expect this exception.
+    }
+    try {
+      builder.getRepeatedFieldBuilder(
+          descriptor.findFieldByName("optional_nested_message"), 0);
+      fail("Exception was not thrown");
+    } catch (UnsupportedOperationException e) {
+      // We expect this exception.
+    }
+  }
 }
diff --git a/java/src/test/java/com/google/protobuf/LazyMessageLiteTest.java b/java/src/test/java/com/google/protobuf/LazyMessageLiteTest.java
index 00e3a843..9de794fe 100644
--- a/java/src/test/java/com/google/protobuf/LazyMessageLiteTest.java
+++ b/java/src/test/java/com/google/protobuf/LazyMessageLiteTest.java
@@ -36,8 +36,6 @@ import protobuf_unittest.LazyFieldsLite.LazyNestedInnerMessageLite;
 
 import junit.framework.TestCase;
 
-import org.easymock.classextension.EasyMock;
-
 import java.util.ArrayList;
 
 /**
@@ -52,14 +50,10 @@ public class LazyMessageLiteTest extends TestCase {
   @Override
   protected void setUp() throws Exception {
     super.setUp();
-
-    originalLazyInnerMessageLiteParser = LazyInnerMessageLite.PARSER;
   }
 
   @Override
   protected void tearDown() throws Exception {
-    LazyInnerMessageLite.PARSER = originalLazyInnerMessageLiteParser;
-
     super.tearDown();
   }
 
@@ -291,29 +285,4 @@ public class LazyMessageLiteTest extends TestCase {
 
     assertEquals(bytes, deserialized.toByteString());
   }
-
-  public void testLaziness() throws InvalidProtocolBufferException {
-    LazyInnerMessageLite inner = LazyInnerMessageLite.newBuilder()
-        .setNum(2)
-        .build();
-    LazyMessageLite outer = LazyMessageLite.newBuilder()
-        .setNum(1)
-        .setInner(inner)
-        .setOneofInner(inner)
-        .build();
-    ByteString bytes = outer.toByteString();
-
-
-    // The parser for inner / oneofInner message shouldn't be used if
-    // getInner / getOneofInner is not called.
-    LazyInnerMessageLite.PARSER = EasyMock.createStrictMock(Parser.class);
-
-    EasyMock.replay(LazyInnerMessageLite.PARSER);
-
-    LazyMessageLite deserialized = LazyMessageLite.parseFrom(bytes);
-    assertEquals(1, deserialized.getNum());
-    assertEquals(421,  deserialized.getNumWithDefault());
-
-    EasyMock.verify(LazyInnerMessageLite.PARSER);
-  }
 }
diff --git a/java/src/test/java/com/google/protobuf/LiteEqualsAndHashTest.java b/java/src/test/java/com/google/protobuf/LiteEqualsAndHashTest.java
index 94f4fcf5..035917c8 100644
--- a/java/src/test/java/com/google/protobuf/LiteEqualsAndHashTest.java
+++ b/java/src/test/java/com/google/protobuf/LiteEqualsAndHashTest.java
@@ -82,4 +82,27 @@ public class LiteEqualsAndHashTest extends TestCase {
     BarPrime barPrime = BarPrime.newBuilder().setName("bar").build();
     assertFalse(bar.equals(barPrime));
   }
+
+  public void testEqualsAndHashCodeWithUnknownFields() throws InvalidProtocolBufferException {
+    Foo fooWithOnlyValue = Foo.newBuilder()
+        .setValue(1)
+        .build();
+
+    Foo fooWithValueAndExtension = fooWithOnlyValue.toBuilder()
+        .setValue(1)
+        .setExtension(Bar.fooExt, Bar.newBuilder()
+            .setName("name")
+            .build())
+        .build();
+
+    Foo fooWithValueAndUnknownFields = Foo.parseFrom(fooWithValueAndExtension.toByteArray());
+
+    assertEqualsAndHashCodeAreFalse(fooWithOnlyValue, fooWithValueAndUnknownFields);
+    assertEqualsAndHashCodeAreFalse(fooWithValueAndExtension, fooWithValueAndUnknownFields);
+  }
+
+  private void assertEqualsAndHashCodeAreFalse(Object o1, Object o2) {
+    assertFalse(o1.equals(o2));
+    assertFalse(o1.hashCode() == o2.hashCode());
+  }
 }
diff --git a/java/src/test/java/com/google/protobuf/MapForProto2LiteTest.java b/java/src/test/java/com/google/protobuf/MapForProto2LiteTest.java
new file mode 100644
index 00000000..22dbeb76
--- /dev/null
+++ b/java/src/test/java/com/google/protobuf/MapForProto2LiteTest.java
@@ -0,0 +1,277 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import map_lite_test.MapForProto2TestProto.TestMap;
+import map_lite_test.MapForProto2TestProto.TestMap.MessageValue;
+import map_lite_test.MapForProto2TestProto.TestUnknownEnumValue;
+
+import junit.framework.TestCase;
+
+/**
+ * Unit tests for map fields.
+ */
+public class MapForProto2LiteTest extends TestCase {
+  private void setMapValues(TestMap.Builder builder) {
+    builder.getMutableInt32ToInt32Field().put(1, 11);
+    builder.getMutableInt32ToInt32Field().put(2, 22);
+    builder.getMutableInt32ToInt32Field().put(3, 33);
+
+    builder.getMutableInt32ToStringField().put(1, "11");
+    builder.getMutableInt32ToStringField().put(2, "22");
+    builder.getMutableInt32ToStringField().put(3, "33");
+    
+    builder.getMutableInt32ToBytesField().put(1, TestUtil.toBytes("11"));
+    builder.getMutableInt32ToBytesField().put(2, TestUtil.toBytes("22"));
+    builder.getMutableInt32ToBytesField().put(3, TestUtil.toBytes("33"));
+    
+    builder.getMutableInt32ToEnumField().put(1, TestMap.EnumValue.FOO);
+    builder.getMutableInt32ToEnumField().put(2, TestMap.EnumValue.BAR);
+    builder.getMutableInt32ToEnumField().put(3, TestMap.EnumValue.BAZ);
+    
+    builder.getMutableInt32ToMessageField().put(
+        1, MessageValue.newBuilder().setValue(11).build());
+    builder.getMutableInt32ToMessageField().put(
+        2, MessageValue.newBuilder().setValue(22).build());
+    builder.getMutableInt32ToMessageField().put(
+        3, MessageValue.newBuilder().setValue(33).build());
+    
+    builder.getMutableStringToInt32Field().put("1", 11);
+    builder.getMutableStringToInt32Field().put("2", 22);
+    builder.getMutableStringToInt32Field().put("3", 33);
+  }
+
+  private void assertMapValuesSet(TestMap message) {
+    assertEquals(3, message.getInt32ToInt32Field().size());
+    assertEquals(11, message.getInt32ToInt32Field().get(1).intValue());
+    assertEquals(22, message.getInt32ToInt32Field().get(2).intValue());
+    assertEquals(33, message.getInt32ToInt32Field().get(3).intValue());
+
+    assertEquals(3, message.getInt32ToStringField().size());
+    assertEquals("11", message.getInt32ToStringField().get(1));
+    assertEquals("22", message.getInt32ToStringField().get(2));
+    assertEquals("33", message.getInt32ToStringField().get(3));
+    
+    assertEquals(3, message.getInt32ToBytesField().size());
+    assertEquals(TestUtil.toBytes("11"), message.getInt32ToBytesField().get(1));
+    assertEquals(TestUtil.toBytes("22"), message.getInt32ToBytesField().get(2));
+    assertEquals(TestUtil.toBytes("33"), message.getInt32ToBytesField().get(3));
+    
+    assertEquals(3, message.getInt32ToEnumField().size());
+    assertEquals(TestMap.EnumValue.FOO, message.getInt32ToEnumField().get(1));
+    assertEquals(TestMap.EnumValue.BAR, message.getInt32ToEnumField().get(2));
+    assertEquals(TestMap.EnumValue.BAZ, message.getInt32ToEnumField().get(3));
+    
+    assertEquals(3, message.getInt32ToMessageField().size());
+    assertEquals(11, message.getInt32ToMessageField().get(1).getValue());
+    assertEquals(22, message.getInt32ToMessageField().get(2).getValue());
+    assertEquals(33, message.getInt32ToMessageField().get(3).getValue());
+    
+    assertEquals(3, message.getStringToInt32Field().size());
+    assertEquals(11, message.getStringToInt32Field().get("1").intValue());
+    assertEquals(22, message.getStringToInt32Field().get("2").intValue());
+    assertEquals(33, message.getStringToInt32Field().get("3").intValue());
+  }
+
+  private void updateMapValues(TestMap.Builder builder) {
+    builder.getMutableInt32ToInt32Field().put(1, 111);
+    builder.getMutableInt32ToInt32Field().remove(2);
+    builder.getMutableInt32ToInt32Field().put(4, 44);
+
+    builder.getMutableInt32ToStringField().put(1, "111");
+    builder.getMutableInt32ToStringField().remove(2);
+    builder.getMutableInt32ToStringField().put(4, "44");
+    
+    builder.getMutableInt32ToBytesField().put(1, TestUtil.toBytes("111"));
+    builder.getMutableInt32ToBytesField().remove(2);
+    builder.getMutableInt32ToBytesField().put(4, TestUtil.toBytes("44"));
+    
+    builder.getMutableInt32ToEnumField().put(1, TestMap.EnumValue.BAR);
+    builder.getMutableInt32ToEnumField().remove(2);
+    builder.getMutableInt32ToEnumField().put(4, TestMap.EnumValue.QUX);
+    
+    builder.getMutableInt32ToMessageField().put(
+        1, MessageValue.newBuilder().setValue(111).build());
+    builder.getMutableInt32ToMessageField().remove(2);
+    builder.getMutableInt32ToMessageField().put(
+        4, MessageValue.newBuilder().setValue(44).build());
+    
+    builder.getMutableStringToInt32Field().put("1", 111);
+    builder.getMutableStringToInt32Field().remove("2");
+    builder.getMutableStringToInt32Field().put("4", 44);
+  }
+
+  private void assertMapValuesUpdated(TestMap message) {
+    assertEquals(3, message.getInt32ToInt32Field().size());
+    assertEquals(111, message.getInt32ToInt32Field().get(1).intValue());
+    assertEquals(33, message.getInt32ToInt32Field().get(3).intValue());
+    assertEquals(44, message.getInt32ToInt32Field().get(4).intValue());
+
+    assertEquals(3, message.getInt32ToStringField().size());
+    assertEquals("111", message.getInt32ToStringField().get(1));
+    assertEquals("33", message.getInt32ToStringField().get(3));
+    assertEquals("44", message.getInt32ToStringField().get(4));
+    
+    assertEquals(3, message.getInt32ToBytesField().size());
+    assertEquals(TestUtil.toBytes("111"), message.getInt32ToBytesField().get(1));
+    assertEquals(TestUtil.toBytes("33"), message.getInt32ToBytesField().get(3));
+    assertEquals(TestUtil.toBytes("44"), message.getInt32ToBytesField().get(4));
+    
+    assertEquals(3, message.getInt32ToEnumField().size());
+    assertEquals(TestMap.EnumValue.BAR, message.getInt32ToEnumField().get(1));
+    assertEquals(TestMap.EnumValue.BAZ, message.getInt32ToEnumField().get(3));
+    assertEquals(TestMap.EnumValue.QUX, message.getInt32ToEnumField().get(4));
+    
+    assertEquals(3, message.getInt32ToMessageField().size());
+    assertEquals(111, message.getInt32ToMessageField().get(1).getValue());
+    assertEquals(33, message.getInt32ToMessageField().get(3).getValue());
+    assertEquals(44, message.getInt32ToMessageField().get(4).getValue());
+    
+    assertEquals(3, message.getStringToInt32Field().size());
+    assertEquals(111, message.getStringToInt32Field().get("1").intValue());
+    assertEquals(33, message.getStringToInt32Field().get("3").intValue());
+    assertEquals(44, message.getStringToInt32Field().get("4").intValue());
+  }
+
+  private void assertMapValuesCleared(TestMap message) {
+    assertEquals(0, message.getInt32ToInt32Field().size());
+    assertEquals(0, message.getInt32ToStringField().size());
+    assertEquals(0, message.getInt32ToBytesField().size());
+    assertEquals(0, message.getInt32ToEnumField().size());
+    assertEquals(0, message.getInt32ToMessageField().size());
+    assertEquals(0, message.getStringToInt32Field().size());
+  }
+
+  public void testGettersAndSetters() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    TestMap message = builder.build();
+    assertMapValuesCleared(message);
+    
+    builder = message.toBuilder();
+    setMapValues(builder);
+    message = builder.build();
+    assertMapValuesSet(message);
+    
+    builder = message.toBuilder();
+    updateMapValues(builder);
+    message = builder.build();
+    assertMapValuesUpdated(message);
+    
+    builder = message.toBuilder();
+    builder.clear();
+    message = builder.build();
+    assertMapValuesCleared(message);
+  }
+
+  public void testSerializeAndParse() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    setMapValues(builder);
+    TestMap message = builder.build();
+    assertEquals(message.getSerializedSize(), message.toByteString().size());
+    message = TestMap.PARSER.parseFrom(message.toByteString());
+    assertMapValuesSet(message);
+    
+    builder = message.toBuilder();
+    updateMapValues(builder);
+    message = builder.build();
+    assertEquals(message.getSerializedSize(), message.toByteString().size());
+    message = TestMap.PARSER.parseFrom(message.toByteString());
+    assertMapValuesUpdated(message);
+    
+    builder = message.toBuilder();
+    builder.clear();
+    message = builder.build();
+    assertEquals(message.getSerializedSize(), message.toByteString().size());
+    message = TestMap.PARSER.parseFrom(message.toByteString());
+    assertMapValuesCleared(message);
+  }
+  
+  public void testMergeFrom() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    setMapValues(builder);
+    TestMap message = builder.build();
+    
+    TestMap.Builder other = TestMap.newBuilder();
+    other.mergeFrom(message);
+    assertMapValuesSet(other.build());
+  }
+
+  public void testEqualsAndHashCode() throws Exception {
+    // Test that generated equals() and hashCode() will disregard the order
+    // of map entries when comparing/hashing map fields.
+    
+    // We can't control the order of elements in a HashMap. The best we can do
+    // here is to add elements in different order.
+    TestMap.Builder b1 = TestMap.newBuilder();
+    b1.getMutableInt32ToInt32Field().put(1, 2);
+    b1.getMutableInt32ToInt32Field().put(3, 4);
+    b1.getMutableInt32ToInt32Field().put(5, 6);
+    TestMap m1 = b1.build();
+    
+    TestMap.Builder b2 = TestMap.newBuilder();
+    b2.getMutableInt32ToInt32Field().put(5, 6);
+    b2.getMutableInt32ToInt32Field().put(1, 2);
+    b2.getMutableInt32ToInt32Field().put(3, 4);
+    TestMap m2 = b2.build();
+    
+    assertEquals(m1, m2);
+    assertEquals(m1.hashCode(), m2.hashCode());
+    
+    // Make sure we did compare map fields.
+    b2.getMutableInt32ToInt32Field().put(1, 0);
+    m2 = b2.build();
+    assertFalse(m1.equals(m2));
+    // Don't check m1.hashCode() != m2.hashCode() because it's not guaranteed
+    // to be different.
+  }
+
+  public void testUnknownEnumValues() throws Exception {
+    TestUnknownEnumValue.Builder builder =
+        TestUnknownEnumValue.newBuilder();
+    builder.getMutableInt32ToInt32Field().put(1, 1);
+    builder.getMutableInt32ToInt32Field().put(2, 54321);
+    ByteString data = builder.build().toByteString();
+
+    TestMap message = TestMap.parseFrom(data);
+    // Entries with unknown enum values will be stored into UnknownFieldSet so
+    // there is only one entry in the map.
+    assertEquals(1, message.getInt32ToEnumField().size());
+    assertEquals(TestMap.EnumValue.BAR, message.getInt32ToEnumField().get(1));
+    // Serializing and parsing should preserve the unknown entry.
+    data = message.toByteString();
+    TestUnknownEnumValue messageWithUnknownEnums =
+        TestUnknownEnumValue.parseFrom(data);
+    assertEquals(2, messageWithUnknownEnums.getInt32ToInt32Field().size());
+    assertEquals(1, messageWithUnknownEnums.getInt32ToInt32Field().get(1).intValue());
+    assertEquals(54321, messageWithUnknownEnums.getInt32ToInt32Field().get(2).intValue());
+  }
+  
+}
diff --git a/java/src/test/java/com/google/protobuf/MapForProto2Test.java b/java/src/test/java/com/google/protobuf/MapForProto2Test.java
new file mode 100644
index 00000000..d78c0d94
--- /dev/null
+++ b/java/src/test/java/com/google/protobuf/MapForProto2Test.java
@@ -0,0 +1,488 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import com.google.protobuf.Descriptors.FieldDescriptor;
+import map_test.MapForProto2TestProto.TestMap;
+import map_test.MapForProto2TestProto.TestMap.MessageValue;
+import map_test.MapForProto2TestProto.TestUnknownEnumValue;
+
+import junit.framework.TestCase;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Unit tests for map fields in proto2 protos.
+ */
+public class MapForProto2Test extends TestCase {
+  private void setMapValues(TestMap.Builder builder) {
+    builder.getMutableInt32ToInt32Field().put(1, 11);
+    builder.getMutableInt32ToInt32Field().put(2, 22);
+    builder.getMutableInt32ToInt32Field().put(3, 33);
+
+    builder.getMutableInt32ToStringField().put(1, "11");
+    builder.getMutableInt32ToStringField().put(2, "22");
+    builder.getMutableInt32ToStringField().put(3, "33");
+    
+    builder.getMutableInt32ToBytesField().put(1, TestUtil.toBytes("11"));
+    builder.getMutableInt32ToBytesField().put(2, TestUtil.toBytes("22"));
+    builder.getMutableInt32ToBytesField().put(3, TestUtil.toBytes("33"));
+    
+    builder.getMutableInt32ToEnumField().put(1, TestMap.EnumValue.FOO);
+    builder.getMutableInt32ToEnumField().put(2, TestMap.EnumValue.BAR);
+    builder.getMutableInt32ToEnumField().put(3, TestMap.EnumValue.BAZ);
+    
+    builder.getMutableInt32ToMessageField().put(
+        1, MessageValue.newBuilder().setValue(11).build());
+    builder.getMutableInt32ToMessageField().put(
+        2, MessageValue.newBuilder().setValue(22).build());
+    builder.getMutableInt32ToMessageField().put(
+        3, MessageValue.newBuilder().setValue(33).build());
+    
+    builder.getMutableStringToInt32Field().put("1", 11);
+    builder.getMutableStringToInt32Field().put("2", 22);
+    builder.getMutableStringToInt32Field().put("3", 33);
+  }
+
+  private void assertMapValuesSet(TestMap message) {
+    assertEquals(3, message.getInt32ToInt32Field().size());
+    assertEquals(11, message.getInt32ToInt32Field().get(1).intValue());
+    assertEquals(22, message.getInt32ToInt32Field().get(2).intValue());
+    assertEquals(33, message.getInt32ToInt32Field().get(3).intValue());
+
+    assertEquals(3, message.getInt32ToStringField().size());
+    assertEquals("11", message.getInt32ToStringField().get(1));
+    assertEquals("22", message.getInt32ToStringField().get(2));
+    assertEquals("33", message.getInt32ToStringField().get(3));
+    
+    assertEquals(3, message.getInt32ToBytesField().size());
+    assertEquals(TestUtil.toBytes("11"), message.getInt32ToBytesField().get(1));
+    assertEquals(TestUtil.toBytes("22"), message.getInt32ToBytesField().get(2));
+    assertEquals(TestUtil.toBytes("33"), message.getInt32ToBytesField().get(3));
+    
+    assertEquals(3, message.getInt32ToEnumField().size());
+    assertEquals(TestMap.EnumValue.FOO, message.getInt32ToEnumField().get(1));
+    assertEquals(TestMap.EnumValue.BAR, message.getInt32ToEnumField().get(2));
+    assertEquals(TestMap.EnumValue.BAZ, message.getInt32ToEnumField().get(3));
+    
+    assertEquals(3, message.getInt32ToMessageField().size());
+    assertEquals(11, message.getInt32ToMessageField().get(1).getValue());
+    assertEquals(22, message.getInt32ToMessageField().get(2).getValue());
+    assertEquals(33, message.getInt32ToMessageField().get(3).getValue());
+    
+    assertEquals(3, message.getStringToInt32Field().size());
+    assertEquals(11, message.getStringToInt32Field().get("1").intValue());
+    assertEquals(22, message.getStringToInt32Field().get("2").intValue());
+    assertEquals(33, message.getStringToInt32Field().get("3").intValue());
+  }
+
+  private void updateMapValues(TestMap.Builder builder) {
+    builder.getMutableInt32ToInt32Field().put(1, 111);
+    builder.getMutableInt32ToInt32Field().remove(2);
+    builder.getMutableInt32ToInt32Field().put(4, 44);
+
+    builder.getMutableInt32ToStringField().put(1, "111");
+    builder.getMutableInt32ToStringField().remove(2);
+    builder.getMutableInt32ToStringField().put(4, "44");
+    
+    builder.getMutableInt32ToBytesField().put(1, TestUtil.toBytes("111"));
+    builder.getMutableInt32ToBytesField().remove(2);
+    builder.getMutableInt32ToBytesField().put(4, TestUtil.toBytes("44"));
+    
+    builder.getMutableInt32ToEnumField().put(1, TestMap.EnumValue.BAR);
+    builder.getMutableInt32ToEnumField().remove(2);
+    builder.getMutableInt32ToEnumField().put(4, TestMap.EnumValue.QUX);
+    
+    builder.getMutableInt32ToMessageField().put(
+        1, MessageValue.newBuilder().setValue(111).build());
+    builder.getMutableInt32ToMessageField().remove(2);
+    builder.getMutableInt32ToMessageField().put(
+        4, MessageValue.newBuilder().setValue(44).build());
+    
+    builder.getMutableStringToInt32Field().put("1", 111);
+    builder.getMutableStringToInt32Field().remove("2");
+    builder.getMutableStringToInt32Field().put("4", 44);
+  }
+
+  private void assertMapValuesUpdated(TestMap message) {
+    assertEquals(3, message.getInt32ToInt32Field().size());
+    assertEquals(111, message.getInt32ToInt32Field().get(1).intValue());
+    assertEquals(33, message.getInt32ToInt32Field().get(3).intValue());
+    assertEquals(44, message.getInt32ToInt32Field().get(4).intValue());
+
+    assertEquals(3, message.getInt32ToStringField().size());
+    assertEquals("111", message.getInt32ToStringField().get(1));
+    assertEquals("33", message.getInt32ToStringField().get(3));
+    assertEquals("44", message.getInt32ToStringField().get(4));
+    
+    assertEquals(3, message.getInt32ToBytesField().size());
+    assertEquals(TestUtil.toBytes("111"), message.getInt32ToBytesField().get(1));
+    assertEquals(TestUtil.toBytes("33"), message.getInt32ToBytesField().get(3));
+    assertEquals(TestUtil.toBytes("44"), message.getInt32ToBytesField().get(4));
+    
+    assertEquals(3, message.getInt32ToEnumField().size());
+    assertEquals(TestMap.EnumValue.BAR, message.getInt32ToEnumField().get(1));
+    assertEquals(TestMap.EnumValue.BAZ, message.getInt32ToEnumField().get(3));
+    assertEquals(TestMap.EnumValue.QUX, message.getInt32ToEnumField().get(4));
+    
+    assertEquals(3, message.getInt32ToMessageField().size());
+    assertEquals(111, message.getInt32ToMessageField().get(1).getValue());
+    assertEquals(33, message.getInt32ToMessageField().get(3).getValue());
+    assertEquals(44, message.getInt32ToMessageField().get(4).getValue());
+    
+    assertEquals(3, message.getStringToInt32Field().size());
+    assertEquals(111, message.getStringToInt32Field().get("1").intValue());
+    assertEquals(33, message.getStringToInt32Field().get("3").intValue());
+    assertEquals(44, message.getStringToInt32Field().get("4").intValue());
+  }
+
+  private void assertMapValuesCleared(TestMap message) {
+    assertEquals(0, message.getInt32ToInt32Field().size());
+    assertEquals(0, message.getInt32ToStringField().size());
+    assertEquals(0, message.getInt32ToBytesField().size());
+    assertEquals(0, message.getInt32ToEnumField().size());
+    assertEquals(0, message.getInt32ToMessageField().size());
+    assertEquals(0, message.getStringToInt32Field().size());
+  }
+
+  public void testGettersAndSetters() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    TestMap message = builder.build();
+    assertMapValuesCleared(message);
+    
+    builder = message.toBuilder();
+    setMapValues(builder);
+    message = builder.build();
+    assertMapValuesSet(message);
+    
+    builder = message.toBuilder();
+    updateMapValues(builder);
+    message = builder.build();
+    assertMapValuesUpdated(message);
+    
+    builder = message.toBuilder();
+    builder.clear();
+    message = builder.build();
+    assertMapValuesCleared(message);
+  }
+
+  public void testSerializeAndParse() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    setMapValues(builder);
+    TestMap message = builder.build();
+    assertEquals(message.getSerializedSize(), message.toByteString().size());
+    message = TestMap.PARSER.parseFrom(message.toByteString());
+    assertMapValuesSet(message);
+    
+    builder = message.toBuilder();
+    updateMapValues(builder);
+    message = builder.build();
+    assertEquals(message.getSerializedSize(), message.toByteString().size());
+    message = TestMap.PARSER.parseFrom(message.toByteString());
+    assertMapValuesUpdated(message);
+    
+    builder = message.toBuilder();
+    builder.clear();
+    message = builder.build();
+    assertEquals(message.getSerializedSize(), message.toByteString().size());
+    message = TestMap.PARSER.parseFrom(message.toByteString());
+    assertMapValuesCleared(message);
+  }
+  
+  public void testMergeFrom() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    setMapValues(builder);
+    TestMap message = builder.build();
+    
+    TestMap.Builder other = TestMap.newBuilder();
+    other.mergeFrom(message);
+    assertMapValuesSet(other.build());
+  }
+
+  public void testEqualsAndHashCode() throws Exception {
+    // Test that generated equals() and hashCode() will disregard the order
+    // of map entries when comparing/hashing map fields.
+    
+    // We can't control the order of elements in a HashMap. The best we can do
+    // here is to add elements in different order.
+    TestMap.Builder b1 = TestMap.newBuilder();
+    b1.getMutableInt32ToInt32Field().put(1, 2);
+    b1.getMutableInt32ToInt32Field().put(3, 4);
+    b1.getMutableInt32ToInt32Field().put(5, 6);
+    TestMap m1 = b1.build();
+    
+    TestMap.Builder b2 = TestMap.newBuilder();
+    b2.getMutableInt32ToInt32Field().put(5, 6);
+    b2.getMutableInt32ToInt32Field().put(1, 2);
+    b2.getMutableInt32ToInt32Field().put(3, 4);
+    TestMap m2 = b2.build();
+    
+    assertEquals(m1, m2);
+    assertEquals(m1.hashCode(), m2.hashCode());
+    
+    // Make sure we did compare map fields.
+    b2.getMutableInt32ToInt32Field().put(1, 0);
+    m2 = b2.build();
+    assertFalse(m1.equals(m2));
+    // Don't check m1.hashCode() != m2.hashCode() because it's not guaranteed
+    // to be different.
+  }
+  
+  
+  // The following methods are used to test reflection API.
+  
+  private static FieldDescriptor f(String name) {
+    return TestMap.getDescriptor().findFieldByName(name);
+  }
+  
+  private static Object getFieldValue(Message mapEntry, String name) {
+    FieldDescriptor field = mapEntry.getDescriptorForType().findFieldByName(name);
+    return mapEntry.getField(field);
+  }
+  
+  private static Message.Builder setFieldValue(
+      Message.Builder mapEntry, String name, Object value) {
+    FieldDescriptor field = mapEntry.getDescriptorForType().findFieldByName(name);
+    mapEntry.setField(field, value);
+    return mapEntry;
+  }
+  
+  private static void assertHasMapValues(Message message, String name, Map<?, ?> values) {
+    FieldDescriptor field = f(name);
+    for (Object entry : (List<?>) message.getField(field)) {
+      Message mapEntry = (Message) entry;
+      Object key = getFieldValue(mapEntry, "key");
+      Object value = getFieldValue(mapEntry, "value");
+      assertTrue(values.containsKey(key));
+      assertEquals(value, values.get(key));
+    }
+    assertEquals(values.size(), message.getRepeatedFieldCount(field));
+    for (int i = 0; i < message.getRepeatedFieldCount(field); i++) {
+      Message mapEntry = (Message) message.getRepeatedField(field, i);
+      Object key = getFieldValue(mapEntry, "key");
+      Object value = getFieldValue(mapEntry, "value");
+      assertTrue(values.containsKey(key));
+      assertEquals(value, values.get(key));
+    }
+  }
+  
+  private static <KeyType, ValueType>
+  Message newMapEntry(Message.Builder builder, String name, KeyType key, ValueType value) {
+    FieldDescriptor field = builder.getDescriptorForType().findFieldByName(name);
+    Message.Builder entryBuilder = builder.newBuilderForField(field);
+    FieldDescriptor keyField = entryBuilder.getDescriptorForType().findFieldByName("key");
+    FieldDescriptor valueField = entryBuilder.getDescriptorForType().findFieldByName("value");
+    entryBuilder.setField(keyField, key);
+    entryBuilder.setField(valueField, value);
+    return entryBuilder.build();
+  }
+  
+  private static void setMapValues(Message.Builder builder, String name, Map<?, ?> values) {
+    List<Message> entryList = new ArrayList<Message>();
+    for (Map.Entry<?, ?> entry : values.entrySet()) {
+      entryList.add(newMapEntry(builder, name, entry.getKey(), entry.getValue()));
+    }
+    FieldDescriptor field = builder.getDescriptorForType().findFieldByName(name);
+    builder.setField(field, entryList);
+  }
+  
+  private static <KeyType, ValueType>
+  Map<KeyType, ValueType> mapForValues(
+      KeyType key1, ValueType value1, KeyType key2, ValueType value2) {
+    Map<KeyType, ValueType> map = new HashMap<KeyType, ValueType>();
+    map.put(key1, value1);
+    map.put(key2, value2);
+    return map;
+  }
+
+  public void testReflectionApi() throws Exception {
+    // In reflection API, map fields are just repeated message fields.
+    TestMap.Builder builder = TestMap.newBuilder();
+    builder.getMutableInt32ToInt32Field().put(1, 2);
+    builder.getMutableInt32ToInt32Field().put(3, 4);
+    builder.getMutableInt32ToMessageField().put(
+        11, MessageValue.newBuilder().setValue(22).build());
+    builder.getMutableInt32ToMessageField().put(
+        33, MessageValue.newBuilder().setValue(44).build());
+    TestMap message = builder.build();
+
+    // Test getField(), getRepeatedFieldCount(), getRepeatedField().
+    assertHasMapValues(message, "int32_to_int32_field",
+        mapForValues(1, 2, 3, 4));
+    assertHasMapValues(message, "int32_to_message_field",
+        mapForValues(
+            11, MessageValue.newBuilder().setValue(22).build(),
+            33, MessageValue.newBuilder().setValue(44).build()));
+    
+    // Test clearField()
+    builder.clearField(f("int32_to_int32_field"));
+    builder.clearField(f("int32_to_message_field"));
+    message = builder.build();
+    assertEquals(0, message.getInt32ToInt32Field().size());
+    assertEquals(0, message.getInt32ToMessageField().size());
+    
+    // Test setField()
+    setMapValues(builder, "int32_to_int32_field",
+        mapForValues(11, 22, 33, 44));
+    setMapValues(builder, "int32_to_message_field",
+        mapForValues(
+            111, MessageValue.newBuilder().setValue(222).build(),
+            333, MessageValue.newBuilder().setValue(444).build()));
+    message = builder.build();
+    assertEquals(22, message.getInt32ToInt32Field().get(11).intValue());
+    assertEquals(44, message.getInt32ToInt32Field().get(33).intValue());
+    assertEquals(222, message.getInt32ToMessageField().get(111).getValue());
+    assertEquals(444, message.getInt32ToMessageField().get(333).getValue());
+    
+    // Test addRepeatedField
+    builder.addRepeatedField(f("int32_to_int32_field"),
+        newMapEntry(builder, "int32_to_int32_field", 55, 66));
+    builder.addRepeatedField(f("int32_to_message_field"),
+        newMapEntry(builder, "int32_to_message_field", 555,
+            MessageValue.newBuilder().setValue(666).build()));
+    message = builder.build();
+    assertEquals(66, message.getInt32ToInt32Field().get(55).intValue());
+    assertEquals(666, message.getInt32ToMessageField().get(555).getValue());
+
+    // Test addRepeatedField (overriding existing values)
+    builder.addRepeatedField(f("int32_to_int32_field"),
+        newMapEntry(builder, "int32_to_int32_field", 55, 55));
+    builder.addRepeatedField(f("int32_to_message_field"),
+        newMapEntry(builder, "int32_to_message_field", 555,
+            MessageValue.newBuilder().setValue(555).build()));
+    message = builder.build();
+    assertEquals(55, message.getInt32ToInt32Field().get(55).intValue());
+    assertEquals(555, message.getInt32ToMessageField().get(555).getValue());
+    
+    // Test setRepeatedField
+    for (int i = 0; i < builder.getRepeatedFieldCount(f("int32_to_int32_field")); i++) {
+      Message mapEntry = (Message) builder.getRepeatedField(f("int32_to_int32_field"), i);
+      int oldKey = ((Integer) getFieldValue(mapEntry, "key")).intValue();
+      int oldValue = ((Integer) getFieldValue(mapEntry, "value")).intValue();
+      // Swap key with value for each entry.
+      Message.Builder mapEntryBuilder = mapEntry.toBuilder();
+      setFieldValue(mapEntryBuilder, "key", oldValue);
+      setFieldValue(mapEntryBuilder, "value", oldKey);
+      builder.setRepeatedField(f("int32_to_int32_field"), i, mapEntryBuilder.build());
+    }
+    message = builder.build();
+    assertEquals(11, message.getInt32ToInt32Field().get(22).intValue());
+    assertEquals(33, message.getInt32ToInt32Field().get(44).intValue());
+    assertEquals(55, message.getInt32ToInt32Field().get(55).intValue());
+  }
+  
+  public void testTextFormat() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    setMapValues(builder);
+    TestMap message = builder.build();
+    
+    String textData = TextFormat.printToString(message);
+    
+    builder = TestMap.newBuilder();
+    TextFormat.merge(textData, builder);
+    message = builder.build();
+    
+    assertMapValuesSet(message);
+  }
+  
+  public void testDynamicMessage() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    setMapValues(builder);
+    TestMap message = builder.build();
+    
+    Message dynamicDefaultInstance =
+        DynamicMessage.getDefaultInstance(TestMap.getDescriptor());
+    Message dynamicMessage = dynamicDefaultInstance
+        .newBuilderForType().mergeFrom(message.toByteString()).build();
+    
+    assertEquals(message, dynamicMessage);
+    assertEquals(message.hashCode(), dynamicMessage.hashCode());
+  }
+  
+  public void testReflectionEqualsAndHashCode() throws Exception {
+    // Test that generated equals() and hashCode() will disregard the order
+    // of map entries when comparing/hashing map fields.
+
+    // We use DynamicMessage to test reflection based equals()/hashCode().
+    Message dynamicDefaultInstance =
+        DynamicMessage.getDefaultInstance(TestMap.getDescriptor());
+    FieldDescriptor field = f("int32_to_int32_field");
+    
+    Message.Builder b1 = dynamicDefaultInstance.newBuilderForType();
+    b1.addRepeatedField(field, newMapEntry(b1, "int32_to_int32_field", 1, 2));
+    b1.addRepeatedField(field, newMapEntry(b1, "int32_to_int32_field", 3, 4));
+    b1.addRepeatedField(field, newMapEntry(b1, "int32_to_int32_field", 5, 6));
+    Message m1 = b1.build();
+    
+    Message.Builder b2 = dynamicDefaultInstance.newBuilderForType();
+    b2.addRepeatedField(field, newMapEntry(b2, "int32_to_int32_field", 5, 6));
+    b2.addRepeatedField(field, newMapEntry(b2, "int32_to_int32_field", 1, 2));
+    b2.addRepeatedField(field, newMapEntry(b2, "int32_to_int32_field", 3, 4));
+    Message m2 = b2.build();
+    
+    assertEquals(m1, m2);
+    assertEquals(m1.hashCode(), m2.hashCode());
+    
+    // Make sure we did compare map fields.
+    b2.setRepeatedField(field, 0, newMapEntry(b1, "int32_to_int32_field", 0, 0));
+    m2 = b2.build();
+    assertFalse(m1.equals(m2));
+    // Don't check m1.hashCode() != m2.hashCode() because it's not guaranteed
+    // to be different.
+  }
+  
+  public void testUnknownEnumValues() throws Exception {
+    TestUnknownEnumValue.Builder builder =
+        TestUnknownEnumValue.newBuilder();
+    builder.getMutableInt32ToInt32Field().put(1, 1);
+    builder.getMutableInt32ToInt32Field().put(2, 54321);
+    ByteString data = builder.build().toByteString();
+
+    TestMap message = TestMap.parseFrom(data);
+    // Entries with unknown enum values will be stored into UnknownFieldSet so
+    // there is only one entry in the map.
+    assertEquals(1, message.getInt32ToEnumField().size());
+    assertEquals(TestMap.EnumValue.BAR, message.getInt32ToEnumField().get(1));
+    // UnknownFieldSet should not be empty.
+    assertFalse(message.getUnknownFields().asMap().isEmpty());
+    // Serializing and parsing should preserve the unknown entry.
+    data = message.toByteString();
+    TestUnknownEnumValue messageWithUnknownEnums =
+        TestUnknownEnumValue.parseFrom(data);
+    assertEquals(2, messageWithUnknownEnums.getInt32ToInt32Field().size());
+    assertEquals(1, messageWithUnknownEnums.getInt32ToInt32Field().get(1).intValue());
+    assertEquals(54321, messageWithUnknownEnums.getInt32ToInt32Field().get(2).intValue());
+  }
+
+}
diff --git a/java/src/test/java/com/google/protobuf/MapTest.java b/java/src/test/java/com/google/protobuf/MapTest.java
new file mode 100644
index 00000000..542a20e7
--- /dev/null
+++ b/java/src/test/java/com/google/protobuf/MapTest.java
@@ -0,0 +1,569 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.EnumDescriptor;
+import com.google.protobuf.Descriptors.EnumValueDescriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+import map_test.MapTestProto.TestMap;
+import map_test.MapTestProto.TestMap.MessageValue;
+import map_test.MapTestProto.TestOnChangeEventPropagation;
+
+import junit.framework.TestCase;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Unit tests for map fields.
+ */
+public class MapTest extends TestCase {
+  private void setMapValues(TestMap.Builder builder) {
+    builder.getMutableInt32ToInt32Field().put(1, 11);
+    builder.getMutableInt32ToInt32Field().put(2, 22);
+    builder.getMutableInt32ToInt32Field().put(3, 33);
+
+    builder.getMutableInt32ToStringField().put(1, "11");
+    builder.getMutableInt32ToStringField().put(2, "22");
+    builder.getMutableInt32ToStringField().put(3, "33");
+    
+    builder.getMutableInt32ToBytesField().put(1, TestUtil.toBytes("11"));
+    builder.getMutableInt32ToBytesField().put(2, TestUtil.toBytes("22"));
+    builder.getMutableInt32ToBytesField().put(3, TestUtil.toBytes("33"));
+    
+    builder.getMutableInt32ToEnumField().put(1, TestMap.EnumValue.FOO);
+    builder.getMutableInt32ToEnumField().put(2, TestMap.EnumValue.BAR);
+    builder.getMutableInt32ToEnumField().put(3, TestMap.EnumValue.BAZ);
+    
+    builder.getMutableInt32ToMessageField().put(
+        1, MessageValue.newBuilder().setValue(11).build());
+    builder.getMutableInt32ToMessageField().put(
+        2, MessageValue.newBuilder().setValue(22).build());
+    builder.getMutableInt32ToMessageField().put(
+        3, MessageValue.newBuilder().setValue(33).build());
+    
+    builder.getMutableStringToInt32Field().put("1", 11);
+    builder.getMutableStringToInt32Field().put("2", 22);
+    builder.getMutableStringToInt32Field().put("3", 33);
+  }
+
+  private void assertMapValuesSet(TestMap message) {
+    assertEquals(3, message.getInt32ToInt32Field().size());
+    assertEquals(11, message.getInt32ToInt32Field().get(1).intValue());
+    assertEquals(22, message.getInt32ToInt32Field().get(2).intValue());
+    assertEquals(33, message.getInt32ToInt32Field().get(3).intValue());
+
+    assertEquals(3, message.getInt32ToStringField().size());
+    assertEquals("11", message.getInt32ToStringField().get(1));
+    assertEquals("22", message.getInt32ToStringField().get(2));
+    assertEquals("33", message.getInt32ToStringField().get(3));
+    
+    assertEquals(3, message.getInt32ToBytesField().size());
+    assertEquals(TestUtil.toBytes("11"), message.getInt32ToBytesField().get(1));
+    assertEquals(TestUtil.toBytes("22"), message.getInt32ToBytesField().get(2));
+    assertEquals(TestUtil.toBytes("33"), message.getInt32ToBytesField().get(3));
+    
+    assertEquals(3, message.getInt32ToEnumField().size());
+    assertEquals(TestMap.EnumValue.FOO, message.getInt32ToEnumField().get(1));
+    assertEquals(TestMap.EnumValue.BAR, message.getInt32ToEnumField().get(2));
+    assertEquals(TestMap.EnumValue.BAZ, message.getInt32ToEnumField().get(3));
+    
+    assertEquals(3, message.getInt32ToMessageField().size());
+    assertEquals(11, message.getInt32ToMessageField().get(1).getValue());
+    assertEquals(22, message.getInt32ToMessageField().get(2).getValue());
+    assertEquals(33, message.getInt32ToMessageField().get(3).getValue());
+    
+    assertEquals(3, message.getStringToInt32Field().size());
+    assertEquals(11, message.getStringToInt32Field().get("1").intValue());
+    assertEquals(22, message.getStringToInt32Field().get("2").intValue());
+    assertEquals(33, message.getStringToInt32Field().get("3").intValue());
+  }
+
+  private void updateMapValues(TestMap.Builder builder) {
+    builder.getMutableInt32ToInt32Field().put(1, 111);
+    builder.getMutableInt32ToInt32Field().remove(2);
+    builder.getMutableInt32ToInt32Field().put(4, 44);
+
+    builder.getMutableInt32ToStringField().put(1, "111");
+    builder.getMutableInt32ToStringField().remove(2);
+    builder.getMutableInt32ToStringField().put(4, "44");
+    
+    builder.getMutableInt32ToBytesField().put(1, TestUtil.toBytes("111"));
+    builder.getMutableInt32ToBytesField().remove(2);
+    builder.getMutableInt32ToBytesField().put(4, TestUtil.toBytes("44"));
+    
+    builder.getMutableInt32ToEnumField().put(1, TestMap.EnumValue.BAR);
+    builder.getMutableInt32ToEnumField().remove(2);
+    builder.getMutableInt32ToEnumField().put(4, TestMap.EnumValue.QUX);
+    
+    builder.getMutableInt32ToMessageField().put(
+        1, MessageValue.newBuilder().setValue(111).build());
+    builder.getMutableInt32ToMessageField().remove(2);
+    builder.getMutableInt32ToMessageField().put(
+        4, MessageValue.newBuilder().setValue(44).build());
+    
+    builder.getMutableStringToInt32Field().put("1", 111);
+    builder.getMutableStringToInt32Field().remove("2");
+    builder.getMutableStringToInt32Field().put("4", 44);
+  }
+
+  private void assertMapValuesUpdated(TestMap message) {
+    assertEquals(3, message.getInt32ToInt32Field().size());
+    assertEquals(111, message.getInt32ToInt32Field().get(1).intValue());
+    assertEquals(33, message.getInt32ToInt32Field().get(3).intValue());
+    assertEquals(44, message.getInt32ToInt32Field().get(4).intValue());
+
+    assertEquals(3, message.getInt32ToStringField().size());
+    assertEquals("111", message.getInt32ToStringField().get(1));
+    assertEquals("33", message.getInt32ToStringField().get(3));
+    assertEquals("44", message.getInt32ToStringField().get(4));
+    
+    assertEquals(3, message.getInt32ToBytesField().size());
+    assertEquals(TestUtil.toBytes("111"), message.getInt32ToBytesField().get(1));
+    assertEquals(TestUtil.toBytes("33"), message.getInt32ToBytesField().get(3));
+    assertEquals(TestUtil.toBytes("44"), message.getInt32ToBytesField().get(4));
+    
+    assertEquals(3, message.getInt32ToEnumField().size());
+    assertEquals(TestMap.EnumValue.BAR, message.getInt32ToEnumField().get(1));
+    assertEquals(TestMap.EnumValue.BAZ, message.getInt32ToEnumField().get(3));
+    assertEquals(TestMap.EnumValue.QUX, message.getInt32ToEnumField().get(4));
+    
+    assertEquals(3, message.getInt32ToMessageField().size());
+    assertEquals(111, message.getInt32ToMessageField().get(1).getValue());
+    assertEquals(33, message.getInt32ToMessageField().get(3).getValue());
+    assertEquals(44, message.getInt32ToMessageField().get(4).getValue());
+    
+    assertEquals(3, message.getStringToInt32Field().size());
+    assertEquals(111, message.getStringToInt32Field().get("1").intValue());
+    assertEquals(33, message.getStringToInt32Field().get("3").intValue());
+    assertEquals(44, message.getStringToInt32Field().get("4").intValue());
+  }
+
+  private void assertMapValuesCleared(TestMap message) {
+    assertEquals(0, message.getInt32ToInt32Field().size());
+    assertEquals(0, message.getInt32ToStringField().size());
+    assertEquals(0, message.getInt32ToBytesField().size());
+    assertEquals(0, message.getInt32ToEnumField().size());
+    assertEquals(0, message.getInt32ToMessageField().size());
+    assertEquals(0, message.getStringToInt32Field().size());
+  }
+
+  public void testGettersAndSetters() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    TestMap message = builder.build();
+    assertMapValuesCleared(message);
+    
+    builder = message.toBuilder();
+    setMapValues(builder);
+    message = builder.build();
+    assertMapValuesSet(message);
+    
+    builder = message.toBuilder();
+    updateMapValues(builder);
+    message = builder.build();
+    assertMapValuesUpdated(message);
+    
+    builder = message.toBuilder();
+    builder.clear();
+    message = builder.build();
+    assertMapValuesCleared(message);
+  }
+
+  public void testSerializeAndParse() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    setMapValues(builder);
+    TestMap message = builder.build();
+    assertEquals(message.getSerializedSize(), message.toByteString().size());
+    message = TestMap.PARSER.parseFrom(message.toByteString());
+    assertMapValuesSet(message);
+    
+    builder = message.toBuilder();
+    updateMapValues(builder);
+    message = builder.build();
+    assertEquals(message.getSerializedSize(), message.toByteString().size());
+    message = TestMap.PARSER.parseFrom(message.toByteString());
+    assertMapValuesUpdated(message);
+    
+    builder = message.toBuilder();
+    builder.clear();
+    message = builder.build();
+    assertEquals(message.getSerializedSize(), message.toByteString().size());
+    message = TestMap.PARSER.parseFrom(message.toByteString());
+    assertMapValuesCleared(message);
+  }
+  
+  public void testMergeFrom() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    setMapValues(builder);
+    TestMap message = builder.build();
+    
+    TestMap.Builder other = TestMap.newBuilder();
+    other.mergeFrom(message);
+    assertMapValuesSet(other.build());
+  }
+
+  public void testEqualsAndHashCode() throws Exception {
+    // Test that generated equals() and hashCode() will disregard the order
+    // of map entries when comparing/hashing map fields.
+    
+    // We can't control the order of elements in a HashMap. The best we can do
+    // here is to add elements in different order.
+    TestMap.Builder b1 = TestMap.newBuilder();
+    b1.getMutableInt32ToInt32Field().put(1, 2);
+    b1.getMutableInt32ToInt32Field().put(3, 4);
+    b1.getMutableInt32ToInt32Field().put(5, 6);
+    TestMap m1 = b1.build();
+    
+    TestMap.Builder b2 = TestMap.newBuilder();
+    b2.getMutableInt32ToInt32Field().put(5, 6);
+    b2.getMutableInt32ToInt32Field().put(1, 2);
+    b2.getMutableInt32ToInt32Field().put(3, 4);
+    TestMap m2 = b2.build();
+    
+    assertEquals(m1, m2);
+    assertEquals(m1.hashCode(), m2.hashCode());
+    
+    // Make sure we did compare map fields.
+    b2.getMutableInt32ToInt32Field().put(1, 0);
+    m2 = b2.build();
+    assertFalse(m1.equals(m2));
+    // Don't check m1.hashCode() != m2.hashCode() because it's not guaranteed
+    // to be different.
+  }
+  
+  
+  public void testNestedBuilderOnChangeEventPropagation() {
+    TestOnChangeEventPropagation.Builder parent =
+        TestOnChangeEventPropagation.newBuilder();
+    parent.getOptionalMessageBuilder().getMutableInt32ToInt32Field().put(1, 2);
+    TestOnChangeEventPropagation message = parent.build();
+    assertEquals(2, message.getOptionalMessage().getInt32ToInt32Field().get(1).intValue());
+    
+    // Make a change using nested builder.
+    parent.getOptionalMessageBuilder().getMutableInt32ToInt32Field().put(1, 3);
+    
+    // Should be able to observe the change.
+    message = parent.build();
+    assertEquals(3, message.getOptionalMessage().getInt32ToInt32Field().get(1).intValue());
+    
+    // Make another change using mergeFrom()
+    TestMap.Builder other = TestMap.newBuilder();
+    other.getMutableInt32ToInt32Field().put(1, 4);
+    parent.getOptionalMessageBuilder().mergeFrom(other.build());
+    
+    // Should be able to observe the change.
+    message = parent.build();
+    assertEquals(4, message.getOptionalMessage().getInt32ToInt32Field().get(1).intValue());
+    
+    // Make yet another change by clearing the nested builder.
+    parent.getOptionalMessageBuilder().clear();
+    
+    // Should be able to observe the change.
+    message = parent.build();
+    assertEquals(0, message.getOptionalMessage().getInt32ToInt32Field().size());
+  }
+  
+  // The following methods are used to test reflection API.
+  
+  private static FieldDescriptor f(String name) {
+    return TestMap.getDescriptor().findFieldByName(name);
+  }
+  
+  private static Object getFieldValue(Message mapEntry, String name) {
+    FieldDescriptor field = mapEntry.getDescriptorForType().findFieldByName(name);
+    return mapEntry.getField(field);
+  }
+  
+  private static Message.Builder setFieldValue(
+      Message.Builder mapEntry, String name, Object value) {
+    FieldDescriptor field = mapEntry.getDescriptorForType().findFieldByName(name);
+    mapEntry.setField(field, value);
+    return mapEntry;
+  }
+  
+  private static void assertHasMapValues(Message message, String name, Map<?, ?> values) {
+    FieldDescriptor field = f(name);
+    for (Object entry : (List<?>) message.getField(field)) {
+      Message mapEntry = (Message) entry;
+      Object key = getFieldValue(mapEntry, "key");
+      Object value = getFieldValue(mapEntry, "value");
+      assertTrue(values.containsKey(key));
+      assertEquals(value, values.get(key));
+    }
+    assertEquals(values.size(), message.getRepeatedFieldCount(field));
+    for (int i = 0; i < message.getRepeatedFieldCount(field); i++) {
+      Message mapEntry = (Message) message.getRepeatedField(field, i);
+      Object key = getFieldValue(mapEntry, "key");
+      Object value = getFieldValue(mapEntry, "value");
+      assertTrue(values.containsKey(key));
+      assertEquals(value, values.get(key));
+    }
+  }
+  
+  private static <KeyType, ValueType>
+  Message newMapEntry(Message.Builder builder, String name, KeyType key, ValueType value) {
+    FieldDescriptor field = builder.getDescriptorForType().findFieldByName(name);
+    Message.Builder entryBuilder = builder.newBuilderForField(field);
+    FieldDescriptor keyField = entryBuilder.getDescriptorForType().findFieldByName("key");
+    FieldDescriptor valueField = entryBuilder.getDescriptorForType().findFieldByName("value");
+    entryBuilder.setField(keyField, key);
+    entryBuilder.setField(valueField, value);
+    return entryBuilder.build();
+  }
+  
+  private static void setMapValues(Message.Builder builder, String name, Map<?, ?> values) {
+    List<Message> entryList = new ArrayList<Message>();
+    for (Map.Entry<?, ?> entry : values.entrySet()) {
+      entryList.add(newMapEntry(builder, name, entry.getKey(), entry.getValue()));
+    }
+    FieldDescriptor field = builder.getDescriptorForType().findFieldByName(name);
+    builder.setField(field, entryList);
+  }
+  
+  private static <KeyType, ValueType>
+  Map<KeyType, ValueType> mapForValues(
+      KeyType key1, ValueType value1, KeyType key2, ValueType value2) {
+    Map<KeyType, ValueType> map = new HashMap<KeyType, ValueType>();
+    map.put(key1, value1);
+    map.put(key2, value2);
+    return map;
+  }
+
+  public void testReflectionApi() throws Exception {
+    // In reflection API, map fields are just repeated message fields.
+    TestMap.Builder builder = TestMap.newBuilder();
+    builder.getMutableInt32ToInt32Field().put(1, 2);
+    builder.getMutableInt32ToInt32Field().put(3, 4);
+    builder.getMutableInt32ToMessageField().put(
+        11, MessageValue.newBuilder().setValue(22).build());
+    builder.getMutableInt32ToMessageField().put(
+        33, MessageValue.newBuilder().setValue(44).build());
+    TestMap message = builder.build();
+
+    // Test getField(), getRepeatedFieldCount(), getRepeatedField().
+    assertHasMapValues(message, "int32_to_int32_field",
+        mapForValues(1, 2, 3, 4));
+    assertHasMapValues(message, "int32_to_message_field",
+        mapForValues(
+            11, MessageValue.newBuilder().setValue(22).build(),
+            33, MessageValue.newBuilder().setValue(44).build()));
+    
+    // Test clearField()
+    builder.clearField(f("int32_to_int32_field"));
+    builder.clearField(f("int32_to_message_field"));
+    message = builder.build();
+    assertEquals(0, message.getInt32ToInt32Field().size());
+    assertEquals(0, message.getInt32ToMessageField().size());
+    
+    // Test setField()
+    setMapValues(builder, "int32_to_int32_field",
+        mapForValues(11, 22, 33, 44));
+    setMapValues(builder, "int32_to_message_field",
+        mapForValues(
+            111, MessageValue.newBuilder().setValue(222).build(),
+            333, MessageValue.newBuilder().setValue(444).build()));
+    message = builder.build();
+    assertEquals(22, message.getInt32ToInt32Field().get(11).intValue());
+    assertEquals(44, message.getInt32ToInt32Field().get(33).intValue());
+    assertEquals(222, message.getInt32ToMessageField().get(111).getValue());
+    assertEquals(444, message.getInt32ToMessageField().get(333).getValue());
+    
+    // Test addRepeatedField
+    builder.addRepeatedField(f("int32_to_int32_field"),
+        newMapEntry(builder, "int32_to_int32_field", 55, 66));
+    builder.addRepeatedField(f("int32_to_message_field"),
+        newMapEntry(builder, "int32_to_message_field", 555,
+            MessageValue.newBuilder().setValue(666).build()));
+    message = builder.build();
+    assertEquals(66, message.getInt32ToInt32Field().get(55).intValue());
+    assertEquals(666, message.getInt32ToMessageField().get(555).getValue());
+
+    // Test addRepeatedField (overriding existing values)
+    builder.addRepeatedField(f("int32_to_int32_field"),
+        newMapEntry(builder, "int32_to_int32_field", 55, 55));
+    builder.addRepeatedField(f("int32_to_message_field"),
+        newMapEntry(builder, "int32_to_message_field", 555,
+            MessageValue.newBuilder().setValue(555).build()));
+    message = builder.build();
+    assertEquals(55, message.getInt32ToInt32Field().get(55).intValue());
+    assertEquals(555, message.getInt32ToMessageField().get(555).getValue());
+    
+    // Test setRepeatedField
+    for (int i = 0; i < builder.getRepeatedFieldCount(f("int32_to_int32_field")); i++) {
+      Message mapEntry = (Message) builder.getRepeatedField(f("int32_to_int32_field"), i);
+      int oldKey = ((Integer) getFieldValue(mapEntry, "key")).intValue();
+      int oldValue = ((Integer) getFieldValue(mapEntry, "value")).intValue();
+      // Swap key with value for each entry.
+      Message.Builder mapEntryBuilder = mapEntry.toBuilder();
+      setFieldValue(mapEntryBuilder, "key", oldValue);
+      setFieldValue(mapEntryBuilder, "value", oldKey);
+      builder.setRepeatedField(f("int32_to_int32_field"), i, mapEntryBuilder.build());
+    }
+    message = builder.build();
+    assertEquals(11, message.getInt32ToInt32Field().get(22).intValue());
+    assertEquals(33, message.getInt32ToInt32Field().get(44).intValue());
+    assertEquals(55, message.getInt32ToInt32Field().get(55).intValue());
+  }
+  
+  public void testTextFormat() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    setMapValues(builder);
+    TestMap message = builder.build();
+    
+    String textData = TextFormat.printToString(message);
+    
+    builder = TestMap.newBuilder();
+    TextFormat.merge(textData, builder);
+    message = builder.build();
+    
+    assertMapValuesSet(message);
+  }
+  
+  public void testDynamicMessage() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    setMapValues(builder);
+    TestMap message = builder.build();
+    
+    Message dynamicDefaultInstance =
+        DynamicMessage.getDefaultInstance(TestMap.getDescriptor());
+    Message dynamicMessage = dynamicDefaultInstance
+        .newBuilderForType().mergeFrom(message.toByteString()).build();
+    
+    assertEquals(message, dynamicMessage);
+    assertEquals(message.hashCode(), dynamicMessage.hashCode());
+  }
+  
+  public void testReflectionEqualsAndHashCode() throws Exception {
+    // Test that generated equals() and hashCode() will disregard the order
+    // of map entries when comparing/hashing map fields.
+
+    // We use DynamicMessage to test reflection based equals()/hashCode().
+    Message dynamicDefaultInstance =
+        DynamicMessage.getDefaultInstance(TestMap.getDescriptor());
+    FieldDescriptor field = f("int32_to_int32_field");
+    
+    Message.Builder b1 = dynamicDefaultInstance.newBuilderForType();
+    b1.addRepeatedField(field, newMapEntry(b1, "int32_to_int32_field", 1, 2));
+    b1.addRepeatedField(field, newMapEntry(b1, "int32_to_int32_field", 3, 4));
+    b1.addRepeatedField(field, newMapEntry(b1, "int32_to_int32_field", 5, 6));
+    Message m1 = b1.build();
+    
+    Message.Builder b2 = dynamicDefaultInstance.newBuilderForType();
+    b2.addRepeatedField(field, newMapEntry(b2, "int32_to_int32_field", 5, 6));
+    b2.addRepeatedField(field, newMapEntry(b2, "int32_to_int32_field", 1, 2));
+    b2.addRepeatedField(field, newMapEntry(b2, "int32_to_int32_field", 3, 4));
+    Message m2 = b2.build();
+    
+    assertEquals(m1, m2);
+    assertEquals(m1.hashCode(), m2.hashCode());
+    
+    // Make sure we did compare map fields.
+    b2.setRepeatedField(field, 0, newMapEntry(b1, "int32_to_int32_field", 0, 0));
+    m2 = b2.build();
+    assertFalse(m1.equals(m2));
+    // Don't check m1.hashCode() != m2.hashCode() because it's not guaranteed
+    // to be different.
+  }
+  
+  public void testUnknownEnumValues() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    builder.getMutableInt32ToEnumFieldValue().put(0, 0);
+    builder.getMutableInt32ToEnumFieldValue().put(1, 1);
+    builder.getMutableInt32ToEnumFieldValue().put(2, 1000);  // unknown value.
+    TestMap message = builder.build();
+
+    assertEquals(TestMap.EnumValue.FOO,
+        message.getInt32ToEnumField().get(0));
+    assertEquals(TestMap.EnumValue.BAR,
+        message.getInt32ToEnumField().get(1));
+    assertEquals(TestMap.EnumValue.UNRECOGNIZED,
+        message.getInt32ToEnumField().get(2));
+    assertEquals(1000, message.getInt32ToEnumFieldValue().get(2).intValue());
+    
+    // Unknown enum values should be preserved after:
+    //   1. Serialization and parsing.
+    //   2. toBuild().
+    //   3. mergeFrom().
+    message = TestMap.parseFrom(message.toByteString());
+    assertEquals(1000, message.getInt32ToEnumFieldValue().get(2).intValue());
+    builder = message.toBuilder();
+    assertEquals(1000, builder.getInt32ToEnumFieldValue().get(2).intValue());
+    builder = TestMap.newBuilder().mergeFrom(message);
+    assertEquals(1000, builder.getInt32ToEnumFieldValue().get(2).intValue());
+    
+    // hashCode()/equals() should take unknown enum values into account.
+    builder.getMutableInt32ToEnumFieldValue().put(2, 1001);
+    TestMap message2 = builder.build();
+    assertFalse(message.hashCode() == message2.hashCode());
+    assertFalse(message.equals(message2));
+    // Unknown values will be converted to UNRECOGNIZED so the resulted enum map
+    // should be the same.
+    assertTrue(message.getInt32ToEnumField().equals(message2.getInt32ToEnumField()));
+  }
+  
+  public void testUnknownEnumValuesInReflectionApi() throws Exception {
+    Descriptor descriptor = TestMap.getDescriptor();
+    EnumDescriptor enumDescriptor = TestMap.EnumValue.getDescriptor();
+    FieldDescriptor field = descriptor.findFieldByName("int32_to_enum_field");
+    
+    Map<Integer, Integer> data = new HashMap<Integer, Integer>();
+    data.put(0, 0);
+    data.put(1, 1);
+    data.put(2, 1000);  // unknown value.
+    
+    TestMap.Builder builder = TestMap.newBuilder();
+    for (Map.Entry<Integer, Integer> entry : data.entrySet()) {
+      builder.getMutableInt32ToEnumFieldValue().put(entry.getKey(), entry.getValue());
+    }
+
+    // Try to read unknown enum values using reflection API.
+    for (int i = 0; i < builder.getRepeatedFieldCount(field); i++) {
+      Message mapEntry = (Message) builder.getRepeatedField(field, i);
+      int key = ((Integer) getFieldValue(mapEntry, "key")).intValue();
+      int value = ((EnumValueDescriptor) getFieldValue(mapEntry, "value")).getNumber();
+      assertEquals(data.get(key).intValue(), value);
+      Message.Builder mapEntryBuilder = mapEntry.toBuilder();
+      // Increase the value by 1.
+      setFieldValue(mapEntryBuilder, "value",
+          enumDescriptor.findValueByNumberCreatingIfUnknown(value + 1));
+      builder.setRepeatedField(field, i, mapEntryBuilder.build());
+    }
+
+    // Verify that enum values have been successfully updated.
+    TestMap message = builder.build();
+    for (Map.Entry<Integer, Integer> entry : message.getInt32ToEnumFieldValue().entrySet()) {
+      assertEquals(data.get(entry.getKey()) + 1, entry.getValue().intValue());
+    }
+  }
+}
diff --git a/java/src/test/java/com/google/protobuf/TestBadIdentifiers.java b/java/src/test/java/com/google/protobuf/TestBadIdentifiers.java
index 614ac7fe..2c60fe0e 100644
--- a/java/src/test/java/com/google/protobuf/TestBadIdentifiers.java
+++ b/java/src/test/java/com/google/protobuf/TestBadIdentifiers.java
@@ -72,7 +72,7 @@ public class TestBadIdentifiers extends TestCase {
     assertEquals(0, message.getMessageField5Count());
 
     assertEquals(0, message.getInt32FieldCount11());
-    assertEquals(1, message.getEnumFieldCount12().getNumber());
+    assertEquals(0, message.getEnumFieldCount12().getNumber());
     assertEquals("", message.getStringFieldCount13());
     assertEquals(ByteString.EMPTY, message.getBytesFieldCount14());
     assertEquals(0, message.getMessageFieldCount15().getSerializedSize());
diff --git a/java/src/test/java/com/google/protobuf/TextFormatTest.java b/java/src/test/java/com/google/protobuf/TextFormatTest.java
index 152bdadc..82f9582f 100644
--- a/java/src/test/java/com/google/protobuf/TextFormatTest.java
+++ b/java/src/test/java/com/google/protobuf/TextFormatTest.java
@@ -73,7 +73,7 @@ public class TextFormatTest extends TestCase {
   private static String exoticText =
     "repeated_int32: -1\n" +
     "repeated_int32: -2147483648\n" +
-    "repeated_int64: -1\n" +
+    "repeated_int64: -1,\n" +
     "repeated_int64: -9223372036854775808\n" +
     "repeated_uint32: 4294967295\n" +
     "repeated_uint32: 2147483648\n" +
@@ -101,7 +101,7 @@ public class TextFormatTest extends TestCase {
 
   private static String canonicalExoticText =
       exoticText.replace(": .", ": 0.").replace(": -.", ": -0.")   // short-form double
-      .replace("23e", "23E").replace("E+", "E").replace("0.23E17", "2.3E16");
+      .replace("23e", "23E").replace("E+", "E").replace("0.23E17", "2.3E16").replace(",", "");
 
   private String messageSetText =
     "[protobuf_unittest.TestMessageSetExtension1] {\n" +
@@ -119,6 +119,7 @@ public class TextFormatTest extends TestCase {
       "  i: 456\n" +
       "}\n";
 
+
   private final TextFormat.Parser parserWithOverwriteForbidden =
       TextFormat.Parser.newBuilder()
           .setSingularOverwritePolicy(
@@ -460,6 +461,7 @@ public class TextFormatTest extends TestCase {
     }
   }
 
+
   private void assertParseErrorWithOverwriteForbidden(String error,
       String text) {
     TestAllTypes.Builder builder = TestAllTypes.newBuilder();
@@ -553,10 +555,10 @@ public class TextFormatTest extends TestCase {
 
   public void testEscape() throws Exception {
     // Escape sequences.
-    assertEquals("\\000\\001\\a\\b\\f\\n\\r\\t\\v\\\\\\'\\\"",
-      TextFormat.escapeBytes(bytes("\0\001\007\b\f\n\r\t\013\\\'\"")));
-    assertEquals("\\000\\001\\a\\b\\f\\n\\r\\t\\v\\\\\\'\\\"",
-      TextFormat.escapeText("\0\001\007\b\f\n\r\t\013\\\'\""));
+    assertEquals("\\000\\001\\a\\b\\f\\n\\r\\t\\v\\\\\\'\\\"\\177",
+      TextFormat.escapeBytes(bytes("\0\001\007\b\f\n\r\t\013\\\'\"\177")));
+    assertEquals("\\000\\001\\a\\b\\f\\n\\r\\t\\v\\\\\\'\\\"\\177",
+      TextFormat.escapeText("\0\001\007\b\f\n\r\t\013\\\'\"\177"));
     assertEquals(bytes("\0\001\007\b\f\n\r\t\013\\\'\""),
       TextFormat.unescapeBytes("\\000\\001\\a\\b\\f\\n\\r\\t\\v\\\\\\'\\\""));
     assertEquals("\0\001\007\b\f\n\r\t\013\\\'\"",
@@ -900,6 +902,7 @@ public class TextFormatTest extends TestCase {
             .build()));
   }
 
+
   public void testParseNonRepeatedFields() throws Exception {
     assertParseSuccessWithOverwriteForbidden(
         "repeated_int32: 1\n" +
diff --git a/java/src/test/java/com/google/protobuf/UnknownEnumValueTest.java b/java/src/test/java/com/google/protobuf/UnknownEnumValueTest.java
new file mode 100644
index 00000000..8f45976f
--- /dev/null
+++ b/java/src/test/java/com/google/protobuf/UnknownEnumValueTest.java
@@ -0,0 +1,255 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.EnumDescriptor;
+import com.google.protobuf.Descriptors.EnumValueDescriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+import com.google.protobuf.FieldPresenceTestProto.TestAllTypes;
+import com.google.protobuf.TextFormat.ParseException;
+
+import junit.framework.TestCase;
+
+/**
+ * Unit tests for protos that keep unknown enum values rather than discard
+ * them as unknown fields.
+ */
+public class UnknownEnumValueTest extends TestCase {
+  public void testUnknownEnumValues() throws Exception {
+    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
+    builder.setOptionalNestedEnumValue(4321);
+    builder.addRepeatedNestedEnumValue(5432);
+    builder.addPackedNestedEnumValue(6543);
+    TestAllTypes message = builder.build();
+    assertEquals(4321, message.getOptionalNestedEnumValue());
+    assertEquals(5432, message.getRepeatedNestedEnumValue(0));
+    assertEquals(5432, message.getRepeatedNestedEnumValueList().get(0).intValue());
+    assertEquals(6543, message.getPackedNestedEnumValue(0));
+    // Returns UNRECOGNIZED if an enum type is requested.
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, message.getOptionalNestedEnum());
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, message.getRepeatedNestedEnum(0));
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, message.getRepeatedNestedEnumList().get(0));
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, message.getPackedNestedEnum(0));
+    
+    // Test serialization and parsing.
+    ByteString data = message.toByteString();
+    message = TestAllTypes.parseFrom(data);
+    assertEquals(4321, message.getOptionalNestedEnumValue());
+    assertEquals(5432, message.getRepeatedNestedEnumValue(0));
+    assertEquals(5432, message.getRepeatedNestedEnumValueList().get(0).intValue());
+    assertEquals(6543, message.getPackedNestedEnumValue(0));
+    // Returns UNRECOGNIZED if an enum type is requested.
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, message.getOptionalNestedEnum());
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, message.getRepeatedNestedEnum(0));
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, message.getRepeatedNestedEnumList().get(0));
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, message.getPackedNestedEnum(0));
+    
+    // Test toBuilder().
+    builder = message.toBuilder();
+    assertEquals(4321, builder.getOptionalNestedEnumValue());
+    assertEquals(5432, builder.getRepeatedNestedEnumValue(0));
+    assertEquals(5432, builder.getRepeatedNestedEnumValueList().get(0).intValue());
+    assertEquals(6543, builder.getPackedNestedEnumValue(0));    
+    // Returns UNRECOGNIZED if an enum type is requested.
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, builder.getOptionalNestedEnum());
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, builder.getRepeatedNestedEnum(0));
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, builder.getRepeatedNestedEnumList().get(0));
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, builder.getPackedNestedEnum(0));
+    
+    // Test mergeFrom().
+    builder = TestAllTypes.newBuilder().mergeFrom(message);
+    assertEquals(4321, builder.getOptionalNestedEnumValue());
+    assertEquals(5432, builder.getRepeatedNestedEnumValue(0));
+    assertEquals(5432, builder.getRepeatedNestedEnumValueList().get(0).intValue());
+    assertEquals(6543, builder.getPackedNestedEnumValue(0));
+    // Returns UNRECOGNIZED if an enum type is requested.
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, builder.getOptionalNestedEnum());
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, builder.getRepeatedNestedEnum(0));
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, builder.getRepeatedNestedEnumList().get(0));
+    assertEquals(TestAllTypes.NestedEnum.UNRECOGNIZED, builder.getPackedNestedEnum(0));
+    
+    // Test equals() and hashCode()
+    TestAllTypes sameMessage = builder.build();
+    assertEquals(message, sameMessage);
+    assertEquals(message.hashCode(), sameMessage.hashCode());
+
+    // Getting the numeric value of UNRECOGNIZED will throw an exception.
+    try {
+      TestAllTypes.NestedEnum.UNRECOGNIZED.getNumber();
+      fail("Exception is expected.");
+    } catch (IllegalArgumentException e) {
+      // Expected.
+    }
+
+    // Setting an enum field to an UNRECOGNIZED value will throw an exception.
+    try {
+      builder.setOptionalNestedEnum(builder.getOptionalNestedEnum());
+      fail("Exception is expected.");
+    } catch (IllegalArgumentException e) {
+      // Expected.
+    }
+    try {
+      builder.addRepeatedNestedEnum(builder.getOptionalNestedEnum());
+      fail("Exception is expected.");
+    } catch (IllegalArgumentException e) {
+      // Expected.
+    }
+  }
+  
+  public void testUnknownEnumValueInReflectionApi() throws Exception {
+    Descriptor descriptor = TestAllTypes.getDescriptor();
+    FieldDescriptor optionalNestedEnumField = descriptor.findFieldByName("optional_nested_enum");
+    FieldDescriptor repeatedNestedEnumField = descriptor.findFieldByName("repeated_nested_enum");
+    FieldDescriptor packedNestedEnumField = descriptor.findFieldByName("packed_nested_enum");
+    EnumDescriptor enumType = TestAllTypes.NestedEnum.getDescriptor();
+
+    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
+    builder.setField(optionalNestedEnumField,
+        enumType.findValueByNumberCreatingIfUnknown(4321));
+    builder.addRepeatedField(repeatedNestedEnumField,
+        enumType.findValueByNumberCreatingIfUnknown(5432));
+    builder.addRepeatedField(packedNestedEnumField,
+        enumType.findValueByNumberCreatingIfUnknown(6543));
+    TestAllTypes message = builder.build();
+    
+    // Getters will return unknown enum values as EnumValueDescriptor.
+    EnumValueDescriptor unknown4321 =
+        (EnumValueDescriptor) message.getField(optionalNestedEnumField);
+    EnumValueDescriptor unknown5432 =
+        (EnumValueDescriptor) message.getRepeatedField(repeatedNestedEnumField, 0);
+    EnumValueDescriptor unknown6543 =
+        (EnumValueDescriptor) message.getRepeatedField(packedNestedEnumField, 0);
+    assertEquals(4321, unknown4321.getNumber());
+    assertEquals(5432, unknown5432.getNumber());
+    assertEquals(6543, unknown6543.getNumber());
+    
+    // Unknown EnumValueDescriptor will map to UNRECOGNIZED.
+    assertEquals(
+        TestAllTypes.NestedEnum.valueOf(unknown4321),
+        TestAllTypes.NestedEnum.UNRECOGNIZED);
+    assertEquals(
+        TestAllTypes.NestedEnum.valueOf(unknown5432),
+        TestAllTypes.NestedEnum.UNRECOGNIZED);
+    assertEquals(
+        TestAllTypes.NestedEnum.valueOf(unknown6543),
+        TestAllTypes.NestedEnum.UNRECOGNIZED);
+    
+    // Setters also accept unknown EnumValueDescriptor.
+    builder.setField(optionalNestedEnumField, unknown6543);
+    builder.setRepeatedField(repeatedNestedEnumField, 0, unknown4321);
+    builder.setRepeatedField(packedNestedEnumField, 0, unknown5432);
+    message = builder.build();
+    // Like other descriptors, unknown EnumValueDescriptor can be compared by
+    // object identity.
+    assertTrue(unknown6543 == message.getField(optionalNestedEnumField));
+    assertTrue(unknown4321 == message.getRepeatedField(repeatedNestedEnumField, 0));
+    assertTrue(unknown5432 == message.getRepeatedField(packedNestedEnumField, 0));
+  }
+  
+  public void testUnknownEnumValueWithDynamicMessage() throws Exception {
+    Descriptor descriptor = TestAllTypes.getDescriptor();
+    FieldDescriptor optionalNestedEnumField = descriptor.findFieldByName("optional_nested_enum");
+    FieldDescriptor repeatedNestedEnumField = descriptor.findFieldByName("repeated_nested_enum");
+    FieldDescriptor packedNestedEnumField = descriptor.findFieldByName("packed_nested_enum");
+    EnumDescriptor enumType = TestAllTypes.NestedEnum.getDescriptor();
+    
+    Message dynamicMessageDefaultInstance = DynamicMessage.getDefaultInstance(descriptor);
+
+    Message.Builder builder = dynamicMessageDefaultInstance.newBuilderForType();
+    builder.setField(optionalNestedEnumField,
+        enumType.findValueByNumberCreatingIfUnknown(4321));
+    builder.addRepeatedField(repeatedNestedEnumField,
+        enumType.findValueByNumberCreatingIfUnknown(5432));
+    builder.addRepeatedField(packedNestedEnumField,
+        enumType.findValueByNumberCreatingIfUnknown(6543));
+    Message message = builder.build();
+    assertEquals(4321,
+        ((EnumValueDescriptor) message.getField(optionalNestedEnumField)).getNumber());
+    assertEquals(5432,
+        ((EnumValueDescriptor) message.getRepeatedField(repeatedNestedEnumField, 0)).getNumber());
+    assertEquals(6543,
+        ((EnumValueDescriptor) message.getRepeatedField(packedNestedEnumField, 0)).getNumber());
+    
+    // Test reflection based serialization/parsing implementation.
+    ByteString data = message.toByteString();
+    message = dynamicMessageDefaultInstance
+        .newBuilderForType()
+        .mergeFrom(data)
+        .build();
+    assertEquals(4321,
+        ((EnumValueDescriptor) message.getField(optionalNestedEnumField)).getNumber());
+    assertEquals(5432,
+        ((EnumValueDescriptor) message.getRepeatedField(repeatedNestedEnumField, 0)).getNumber());
+    assertEquals(6543,
+        ((EnumValueDescriptor) message.getRepeatedField(packedNestedEnumField, 0)).getNumber());
+    
+    // Test reflection based equals()/hashCode().
+    builder = dynamicMessageDefaultInstance.newBuilderForType();
+    builder.setField(optionalNestedEnumField,
+        enumType.findValueByNumberCreatingIfUnknown(4321));
+    builder.addRepeatedField(repeatedNestedEnumField,
+        enumType.findValueByNumberCreatingIfUnknown(5432));
+    builder.addRepeatedField(packedNestedEnumField,
+        enumType.findValueByNumberCreatingIfUnknown(6543));
+    Message sameMessage = builder.build();
+    assertEquals(message, sameMessage);
+    assertEquals(message.hashCode(), sameMessage.hashCode());
+    builder.setField(optionalNestedEnumField,
+        enumType.findValueByNumberCreatingIfUnknown(0));
+    Message differentMessage = builder.build();
+    assertFalse(message.equals(differentMessage));
+  }
+  
+  public void testUnknownEnumValuesInTextFormat() {
+    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
+    builder.setOptionalNestedEnumValue(4321);
+    builder.addRepeatedNestedEnumValue(5432);
+    builder.addPackedNestedEnumValue(6543);
+    TestAllTypes message = builder.build();
+    
+    // We can print a message with unknown enum values.
+    String textData = TextFormat.printToString(message);
+    assertEquals(
+        "optional_nested_enum: UNKNOWN_ENUM_VALUE_NestedEnum_4321\n"
+        + "repeated_nested_enum: UNKNOWN_ENUM_VALUE_NestedEnum_5432\n"
+        + "packed_nested_enum: UNKNOWN_ENUM_VALUE_NestedEnum_6543\n", textData);
+    
+    // Parsing unknown enum values will fail just like parsing other kinds of
+    // unknown fields.
+    try {
+      TextFormat.merge(textData, builder);
+      fail();
+    } catch (ParseException e) {
+      // expected.
+    }
+  }
+}
diff --git a/java/src/test/java/com/google/protobuf/UnknownFieldSetLiteTest.java b/java/src/test/java/com/google/protobuf/UnknownFieldSetLiteTest.java
new file mode 100644
index 00000000..6372b7a7
--- /dev/null
+++ b/java/src/test/java/com/google/protobuf/UnknownFieldSetLiteTest.java
@@ -0,0 +1,317 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package com.google.protobuf;
+
+import protobuf_unittest.lite_equals_and_hash.LiteEqualsAndHash;
+import protobuf_unittest.lite_equals_and_hash.LiteEqualsAndHash.Bar;
+import protobuf_unittest.lite_equals_and_hash.LiteEqualsAndHash.Foo;
+
+import junit.framework.TestCase;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+
+/**
+ * Tests for {@link UnknownFieldSetLite}.
+ *
+ * @author dweis@google.com (Daniel Weis)
+ */
+public class UnknownFieldSetLiteTest extends TestCase {
+
+  public void testNoDataIsDefaultInstance() {
+    assertSame(
+        UnknownFieldSetLite.getDefaultInstance(),
+        UnknownFieldSetLite.newBuilder()
+            .build());
+  }
+
+  public void testDefaultInstance() {
+    UnknownFieldSetLite unknownFields = UnknownFieldSetLite.getDefaultInstance();
+
+    assertEquals(0, unknownFields.getSerializedSize());
+    assertEquals(ByteString.EMPTY, toByteString(unknownFields));
+  }
+
+  public void testMergeFieldFrom() throws IOException {
+    Foo foo = Foo.newBuilder()
+      .setValue(2)
+      .build();
+
+    CodedInputStream input = CodedInputStream.newInstance(foo.toByteArray());
+
+    UnknownFieldSetLite.Builder builder = UnknownFieldSetLite.newBuilder();
+    builder.mergeFieldFrom(input.readTag(), input);
+
+    assertEquals(foo.toByteString(), toByteString(builder.build()));
+  }
+
+  public void testSerializedSize() throws IOException {
+    Foo foo = Foo.newBuilder()
+      .setValue(2)
+      .build();
+
+    CodedInputStream input = CodedInputStream.newInstance(foo.toByteArray());
+
+    UnknownFieldSetLite.Builder builder = UnknownFieldSetLite.newBuilder();
+    builder.mergeFieldFrom(input.readTag(), input);
+
+    assertEquals(foo.toByteString().size(), builder.build().getSerializedSize());
+  }
+
+  public void testMergeVarintField() throws IOException {
+    UnknownFieldSetLite.Builder builder = UnknownFieldSetLite.newBuilder();
+    builder.mergeVarintField(10, 2);
+
+    CodedInputStream input =
+        CodedInputStream.newInstance(toByteString(builder.build()).toByteArray());
+
+    int tag = input.readTag();
+    assertEquals(10, WireFormat.getTagFieldNumber(tag));
+    assertEquals(WireFormat.WIRETYPE_VARINT, WireFormat.getTagWireType(tag));
+    assertEquals(2, input.readUInt64());
+    assertTrue(input.isAtEnd());
+  }
+
+  public void testMergeVarintField_negative() throws IOException {
+    UnknownFieldSetLite.Builder builder = UnknownFieldSetLite.newBuilder();
+    builder.mergeVarintField(10, -6);
+
+    CodedInputStream input =
+        CodedInputStream.newInstance(toByteString(builder.build()).toByteArray());
+
+    int tag = input.readTag();
+    assertEquals(10, WireFormat.getTagFieldNumber(tag));
+    assertEquals(WireFormat.WIRETYPE_VARINT, WireFormat.getTagWireType(tag));
+    assertEquals(-6, input.readUInt64());
+    assertTrue(input.isAtEnd());
+  }
+
+  public void testEqualsAndHashCode() {
+    UnknownFieldSetLite.Builder builder1 = UnknownFieldSetLite.newBuilder();
+    builder1.mergeVarintField(10, 2);
+    UnknownFieldSetLite unknownFields1 = builder1.build();
+
+    UnknownFieldSetLite.Builder builder2 = UnknownFieldSetLite.newBuilder();
+    builder2.mergeVarintField(10, 2);
+    UnknownFieldSetLite unknownFields2 = builder2.build();
+
+    assertEquals(unknownFields1, unknownFields2);
+    assertEquals(unknownFields1.hashCode(), unknownFields2.hashCode());
+    assertFalse(unknownFields1.equals(UnknownFieldSetLite.getDefaultInstance()));
+    assertFalse(unknownFields1.hashCode() == UnknownFieldSetLite.getDefaultInstance().hashCode());
+  }
+
+  public void testConcat() throws IOException {
+    UnknownFieldSetLite.Builder builder = UnknownFieldSetLite.newBuilder();
+    builder.mergeVarintField(10, 2);
+    UnknownFieldSetLite unknownFields = builder.build();
+
+    unknownFields = UnknownFieldSetLite.concat(unknownFields, unknownFields);
+
+    CodedInputStream input =
+        CodedInputStream.newInstance(toByteString(unknownFields).toByteArray());
+
+    int tag = input.readTag();
+    assertEquals(10, WireFormat.getTagFieldNumber(tag));
+    assertEquals(WireFormat.WIRETYPE_VARINT, WireFormat.getTagWireType(tag));
+    assertEquals(2, input.readUInt64());
+    assertFalse(input.isAtEnd());
+    input.readTag();
+    assertEquals(10, WireFormat.getTagFieldNumber(tag));
+    assertEquals(WireFormat.WIRETYPE_VARINT, WireFormat.getTagWireType(tag));
+    assertEquals(2, input.readUInt64());
+    assertTrue(input.isAtEnd());
+  }
+
+  public void testConcat_empty() {
+    UnknownFieldSetLite unknownFields = UnknownFieldSetLite.concat(
+        UnknownFieldSetLite.getDefaultInstance(), UnknownFieldSetLite.getDefaultInstance());
+
+    assertEquals(0, unknownFields.getSerializedSize());
+    assertEquals(ByteString.EMPTY, toByteString(unknownFields));
+  }
+
+  public void testBuilderReuse() throws IOException {
+    UnknownFieldSetLite.Builder builder = UnknownFieldSetLite.newBuilder();
+    builder.mergeVarintField(10, 2);
+    builder.build();
+
+    try {
+      builder.build();
+      fail();
+    } catch (IllegalStateException e) {
+      // Expected.
+    }
+
+    try {
+      builder.mergeFieldFrom(0, CodedInputStream.newInstance(new byte[0]));
+      fail();
+    } catch (IllegalStateException e) {
+      // Expected.
+    }
+
+    try {
+      builder.mergeVarintField(5, 1);
+      fail();
+    } catch (IllegalStateException e) {
+      // Expected.
+    }
+  }
+
+  public void testBuilderReuse_empty() {
+    UnknownFieldSetLite.Builder builder = UnknownFieldSetLite.newBuilder();
+    builder.build();
+
+    try {
+      builder.build();
+      fail();
+    } catch (IllegalStateException e) {
+      // Expected.
+    }
+  }
+
+  public void testRoundTrips() throws InvalidProtocolBufferException {
+    Foo foo = Foo.newBuilder()
+        .setValue(1)
+        .setExtension(Bar.fooExt, Bar.newBuilder()
+            .setName("name")
+            .build())
+        .setExtension(LiteEqualsAndHash.varint, 22)
+        .setExtension(LiteEqualsAndHash.fixed32, 44)
+        .setExtension(LiteEqualsAndHash.fixed64, 66L)
+        .setExtension(LiteEqualsAndHash.myGroup, LiteEqualsAndHash.MyGroup.newBuilder()
+            .setGroupValue("value")
+            .build())
+        .build();
+
+    Foo copy = Foo.parseFrom(foo.toByteArray());
+
+    assertEquals(foo.getSerializedSize(), copy.getSerializedSize());
+    assertFalse(foo.equals(copy));
+
+    Foo secondCopy = Foo.parseFrom(foo.toByteArray());
+    assertEquals(copy, secondCopy);
+
+    ExtensionRegistryLite extensionRegistry = ExtensionRegistryLite.newInstance();
+    LiteEqualsAndHash.registerAllExtensions(extensionRegistry);
+    Foo copyOfCopy = Foo.parseFrom(copy.toByteArray(), extensionRegistry);
+
+    assertEquals(foo, copyOfCopy);
+  }
+
+  public void testMalformedBytes() {
+    try {
+      Foo.parseFrom("this is a malformed protocol buffer".getBytes(StandardCharsets.UTF_8));
+      fail();
+    } catch (InvalidProtocolBufferException e) {
+      // Expected.
+    }
+  }
+
+  public void testMissingStartGroupTag() throws IOException {
+    ByteString.Output byteStringOutput = ByteString.newOutput();
+    CodedOutputStream output = CodedOutputStream.newInstance(byteStringOutput);
+    output.writeGroupNoTag(Foo.newBuilder().setValue(11).build());
+    output.writeTag(100, WireFormat.WIRETYPE_END_GROUP);
+    output.flush();
+
+    try {
+      Foo.parseFrom(byteStringOutput.toByteString());
+      fail();
+    } catch (InvalidProtocolBufferException e) {
+      // Expected.
+    }
+  }
+
+  public void testMissingEndGroupTag() throws IOException {
+    ByteString.Output byteStringOutput = ByteString.newOutput();
+    CodedOutputStream output = CodedOutputStream.newInstance(byteStringOutput);
+    output.writeTag(100, WireFormat.WIRETYPE_START_GROUP);
+    output.writeGroupNoTag(Foo.newBuilder().setValue(11).build());
+    output.flush();
+
+    try {
+      Foo.parseFrom(byteStringOutput.toByteString());
+      fail();
+    } catch (InvalidProtocolBufferException e) {
+      // Expected.
+    }
+  }
+
+  public void testMismatchingGroupTags() throws IOException {
+    ByteString.Output byteStringOutput = ByteString.newOutput();
+    CodedOutputStream output = CodedOutputStream.newInstance(byteStringOutput);
+    output.writeTag(100, WireFormat.WIRETYPE_START_GROUP);
+    output.writeGroupNoTag(Foo.newBuilder().setValue(11).build());
+    output.writeTag(101, WireFormat.WIRETYPE_END_GROUP);
+    output.flush();
+
+    try {
+      Foo.parseFrom(byteStringOutput.toByteString());
+      fail();
+    } catch (InvalidProtocolBufferException e) {
+      // Expected.
+    }
+  }
+
+  public void testTruncatedInput() {
+    Foo foo = Foo.newBuilder()
+        .setValue(1)
+        .setExtension(Bar.fooExt, Bar.newBuilder()
+            .setName("name")
+            .build())
+        .setExtension(LiteEqualsAndHash.varint, 22)
+        .setExtension(LiteEqualsAndHash.myGroup, LiteEqualsAndHash.MyGroup.newBuilder()
+            .setGroupValue("value")
+            .build())
+        .build();
+
+    try {
+      Foo.parseFrom(foo.toByteString().substring(0, foo.toByteString().size() - 10));
+      fail();
+    } catch (InvalidProtocolBufferException e) {
+      // Expected.
+    }
+  }
+
+  private ByteString toByteString(UnknownFieldSetLite unknownFields) {
+    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
+    CodedOutputStream output = CodedOutputStream.newInstance(byteArrayOutputStream);
+    try {
+      unknownFields.writeTo(output);
+      output.flush();
+    } catch (IOException e) {
+      throw new RuntimeException(e);
+    }
+    return ByteString.copyFrom(byteArrayOutputStream.toByteArray());
+  }
+}
diff --git a/java/src/test/java/com/google/protobuf/field_presence_test.proto b/java/src/test/java/com/google/protobuf/field_presence_test.proto
new file mode 100644
index 00000000..8d8ea8ef
--- /dev/null
+++ b/java/src/test/java/com/google/protobuf/field_presence_test.proto
@@ -0,0 +1,93 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package field_presence_test;
+
+import "google/protobuf/unittest.proto";
+
+option java_package = "com.google.protobuf";
+option java_outer_classname = "FieldPresenceTestProto";
+option java_generate_equals_and_hash = true;
+
+message TestAllTypes {
+  enum NestedEnum {
+    FOO = 0;
+    BAR = 1;
+    BAZ = 2;
+  }
+  message NestedMessage {
+    optional int32 value = 1;
+  }
+
+  optional int32 optional_int32 = 1;
+  optional string optional_string = 2;
+  optional bytes optional_bytes = 3;
+  optional NestedEnum optional_nested_enum = 4;
+  optional NestedMessage optional_nested_message = 5;
+  optional protobuf_unittest.TestRequired optional_proto2_message = 6;
+
+  oneof oneof_field {
+    int32 oneof_int32 = 11;
+    uint32 oneof_uint32 = 12;
+    string oneof_string = 13;
+    bytes oneof_bytes = 14;
+    NestedEnum oneof_nested_enum = 15;
+    NestedMessage oneof_nested_message = 16;
+    protobuf_unittest.TestRequired oneof_proto2_message = 17;
+  }
+
+  repeated int32 repeated_int32 = 21;
+  repeated string repeated_string = 22;
+  repeated bytes repeated_bytes = 23;
+  repeated NestedEnum repeated_nested_enum = 24;
+  repeated NestedMessage repeated_nested_message = 25;
+  repeated protobuf_unittest.TestRequired repeated_proto2_message = 26;
+  repeated NestedEnum packed_nested_enum = 27 [packed = true];
+}
+
+message TestOptionalFieldsOnly {
+  optional int32 optional_int32 = 1;
+  optional string optional_string = 2;
+  optional bytes optional_bytes = 3;
+  optional TestAllTypes.NestedEnum optional_nested_enum = 4;
+  optional TestAllTypes.NestedMessage optional_nested_message = 5;
+  optional protobuf_unittest.TestRequired optional_proto2_message = 6;
+}
+
+message TestRepeatedFieldsOnly {
+  repeated int32 repeated_int32 = 21;
+  repeated string repeated_string = 22;
+  repeated bytes repeated_bytes = 23;
+  repeated TestAllTypes.NestedEnum repeated_nested_enum = 24;
+  repeated TestAllTypes.NestedMessage repeated_nested_message = 25;
+  repeated protobuf_unittest.TestRequired repeated_proto2_message = 26;
+}
diff --git a/java/src/test/java/com/google/protobuf/lazy_fields_lite.proto b/java/src/test/java/com/google/protobuf/lazy_fields_lite.proto
index baed4e10..015dc267 100644
--- a/java/src/test/java/com/google/protobuf/lazy_fields_lite.proto
+++ b/java/src/test/java/com/google/protobuf/lazy_fields_lite.proto
@@ -32,6 +32,7 @@
 //
 // A proto file with lazy fields
 
+syntax = "proto2";
 
 package protobuf_unittest;
 
diff --git a/java/src/test/java/com/google/protobuf/lite_equals_and_hash.proto b/java/src/test/java/com/google/protobuf/lite_equals_and_hash.proto
index 68615672..86837250 100644
--- a/java/src/test/java/com/google/protobuf/lite_equals_and_hash.proto
+++ b/java/src/test/java/com/google/protobuf/lite_equals_and_hash.proto
@@ -30,6 +30,7 @@
 
 // Author: pbogle@google.com (Phil Bogle)
 
+syntax = "proto2";
 
 package protobuf_unittest.lite_equals_and_hash;
 
@@ -41,9 +42,15 @@ option optimize_for = LITE_RUNTIME;
 message Foo {
   optional int32 value = 1;
   repeated Bar bar = 2;
+
+  extensions 100 to max;
 }
 
 message Bar {
+  extend Foo {
+    optional Bar foo_ext = 100;
+  }
+
   optional string name = 1;
 }
 
@@ -53,3 +60,13 @@ message BarPrime {
 
 message Empty {
 }
+
+extend Foo {
+  optional int32 varint = 101;
+  optional fixed32 fixed32 = 102;
+  optional fixed64 fixed64 = 103;
+  optional group MyGroup = 104 {
+    optional string group_value = 1;
+  }
+}
+
diff --git a/java/src/test/java/com/google/protobuf/map_for_proto2_lite_test.proto b/java/src/test/java/com/google/protobuf/map_for_proto2_lite_test.proto
new file mode 100644
index 00000000..4f23a4a8
--- /dev/null
+++ b/java/src/test/java/com/google/protobuf/map_for_proto2_lite_test.proto
@@ -0,0 +1,63 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto2";
+
+
+option java_outer_classname = "MapForProto2TestProto";
+option java_generate_equals_and_hash = true;
+
+message TestMap {
+  message MessageValue {
+    optional int32 value = 1;
+  }
+  enum EnumValue {
+    FOO = 0;
+    BAR = 1;
+    BAZ = 2;
+    QUX = 3;
+  }
+
+  map<int32, int32>         int32_to_int32_field = 1;
+  map<int32, string>        int32_to_string_field = 2;
+  map<int32, bytes>         int32_to_bytes_field = 3;
+  map<int32, EnumValue>     int32_to_enum_field = 4;
+  map<int32, MessageValue>  int32_to_message_field = 5;
+  map<string, int32>        string_to_int32_field = 6;
+}
+
+message TestUnknownEnumValue {
+  // Wire-compatible with TestMap.int32_to_enum_field so we can test the
+  // parsing behavior of TestMap regarding unknown enum values.
+  map<int32, int32> int32_to_int32_field = 4;
+}
+package map_for_proto2_lite_test;
+option java_package = "map_lite_test";
+option optimize_for = LITE_RUNTIME;
diff --git a/java/src/test/java/com/google/protobuf/map_for_proto2_test.proto b/java/src/test/java/com/google/protobuf/map_for_proto2_test.proto
new file mode 100644
index 00000000..36dfbd10
--- /dev/null
+++ b/java/src/test/java/com/google/protobuf/map_for_proto2_test.proto
@@ -0,0 +1,62 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto2";
+
+package map_for_proto2_test;
+
+option java_package = "map_test";
+option java_outer_classname = "MapForProto2TestProto";
+option java_generate_equals_and_hash = true;
+
+message TestMap {
+  message MessageValue {
+    optional int32 value = 1;
+  }
+  enum EnumValue {
+    FOO = 0;
+    BAR = 1;
+    BAZ = 2;
+    QUX = 3;
+  }
+
+  map<int32, int32>         int32_to_int32_field = 1;
+  map<int32, string>        int32_to_string_field = 2;
+  map<int32, bytes>         int32_to_bytes_field = 3;
+  map<int32, EnumValue>     int32_to_enum_field = 4;
+  map<int32, MessageValue>  int32_to_message_field = 5;
+  map<string, int32>        string_to_int32_field = 6;
+}
+
+message TestUnknownEnumValue {
+  // Wire-compatible with TestMap.int32_to_enum_field so we can test the
+  // parsing behavior of TestMap regarding unknown enum values.
+  map<int32, int32> int32_to_int32_field = 4;
+}
diff --git a/java/src/test/java/com/google/protobuf/map_test.proto b/java/src/test/java/com/google/protobuf/map_test.proto
new file mode 100644
index 00000000..105ee3f8
--- /dev/null
+++ b/java/src/test/java/com/google/protobuf/map_test.proto
@@ -0,0 +1,63 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package map_test;
+
+option java_package = "map_test";
+option java_outer_classname = "MapTestProto";
+option java_generate_equals_and_hash = true;
+
+message TestMap {
+  message MessageValue {
+    optional int32 value = 1;
+  }
+  enum EnumValue {
+    FOO = 0;
+    BAR = 1;
+    BAZ = 2;
+    QUX = 3;
+  }
+
+  map<int32, int32>        int32_to_int32_field = 1;
+  map<int32, string>       int32_to_string_field = 2;
+  map<int32, bytes>        int32_to_bytes_field = 3;
+  map<int32, EnumValue>    int32_to_enum_field = 4;
+  map<int32, MessageValue> int32_to_message_field = 5;
+  map<string, int32>       string_to_int32_field = 6;
+}
+
+// Used to test that a nested bulider containing map fields will properly
+// propagate the onChange event and mark its parent dirty when a change
+// is made to a map field.
+message TestOnChangeEventPropagation {
+  optional TestMap optional_message = 1;
+}
diff --git a/java/src/test/java/com/google/protobuf/multiple_files_test.proto b/java/src/test/java/com/google/protobuf/multiple_files_test.proto
index 7ec89a05..92790506 100644
--- a/java/src/test/java/com/google/protobuf/multiple_files_test.proto
+++ b/java/src/test/java/com/google/protobuf/multiple_files_test.proto
@@ -32,6 +32,7 @@
 //
 // A proto file which tests the java_multiple_files option.
 
+syntax = "proto2";
 
 // Some generic_services option(s) added automatically.
 // See:  http://go/proto2-generic-services-default
diff --git a/java/src/test/java/com/google/protobuf/nested_builders_test.proto b/java/src/test/java/com/google/protobuf/nested_builders_test.proto
index 8ab4a433..a5dd66d8 100644
--- a/java/src/test/java/com/google/protobuf/nested_builders_test.proto
+++ b/java/src/test/java/com/google/protobuf/nested_builders_test.proto
@@ -30,6 +30,7 @@
 
 // Author: jonp@google.com (Jon Perlow)
 //
+syntax = "proto2";
 
 package protobuf_unittest;
 
diff --git a/java/src/test/java/com/google/protobuf/nested_extension.proto b/java/src/test/java/com/google/protobuf/nested_extension.proto
index 86492867..704e649e 100644
--- a/java/src/test/java/com/google/protobuf/nested_extension.proto
+++ b/java/src/test/java/com/google/protobuf/nested_extension.proto
@@ -33,6 +33,7 @@
 // A proto file with nested extensions. Note that this must be defined in
 // a separate file to properly test the initialization of the outer class.
 
+syntax = "proto2";
 
 import "com/google/protobuf/non_nested_extension.proto";
 
diff --git a/java/src/test/java/com/google/protobuf/nested_extension_lite.proto b/java/src/test/java/com/google/protobuf/nested_extension_lite.proto
index 9c686829..a95c38b2 100644
--- a/java/src/test/java/com/google/protobuf/nested_extension_lite.proto
+++ b/java/src/test/java/com/google/protobuf/nested_extension_lite.proto
@@ -34,6 +34,7 @@
 // this must be defined in a separate file to properly test the initialization
 // of the outer class.
 
+syntax = "proto2";
 
 package protobuf_unittest;
 
diff --git a/java/src/test/java/com/google/protobuf/non_nested_extension.proto b/java/src/test/java/com/google/protobuf/non_nested_extension.proto
index cb2f8b00..31fac552 100644
--- a/java/src/test/java/com/google/protobuf/non_nested_extension.proto
+++ b/java/src/test/java/com/google/protobuf/non_nested_extension.proto
@@ -32,6 +32,7 @@
 //
 // A proto file with extensions.
 
+syntax = "proto2";
 
 package protobuf_unittest;
 
diff --git a/java/src/test/java/com/google/protobuf/non_nested_extension_lite.proto b/java/src/test/java/com/google/protobuf/non_nested_extension_lite.proto
index c1f744b8..37c369ed 100644
--- a/java/src/test/java/com/google/protobuf/non_nested_extension_lite.proto
+++ b/java/src/test/java/com/google/protobuf/non_nested_extension_lite.proto
@@ -32,6 +32,7 @@
 //
 // A proto file with extensions for a MessageLite messages.
 
+syntax = "proto2";
 
 package protobuf_unittest;
 
diff --git a/java/src/test/java/com/google/protobuf/outer_class_name_test.proto b/java/src/test/java/com/google/protobuf/outer_class_name_test.proto
index c5114f89..42083681 100644
--- a/java/src/test/java/com/google/protobuf/outer_class_name_test.proto
+++ b/java/src/test/java/com/google/protobuf/outer_class_name_test.proto
@@ -28,6 +28,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+syntax = "proto2";
+
 package protobuf_unittest;
 
 
diff --git a/java/src/test/java/com/google/protobuf/outer_class_name_test2.proto b/java/src/test/java/com/google/protobuf/outer_class_name_test2.proto
index 741cd281..3e5956b0 100644
--- a/java/src/test/java/com/google/protobuf/outer_class_name_test2.proto
+++ b/java/src/test/java/com/google/protobuf/outer_class_name_test2.proto
@@ -28,6 +28,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+syntax = "proto2";
+
 package protobuf_unittest;
 
 
diff --git a/java/src/test/java/com/google/protobuf/outer_class_name_test3.proto b/java/src/test/java/com/google/protobuf/outer_class_name_test3.proto
index 5d5d4ac9..74a8ba3c 100644
--- a/java/src/test/java/com/google/protobuf/outer_class_name_test3.proto
+++ b/java/src/test/java/com/google/protobuf/outer_class_name_test3.proto
@@ -28,6 +28,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+syntax = "proto2";
+
 package protobuf_unittest;
 
 
diff --git a/java/src/test/java/com/google/protobuf/test_bad_identifiers.proto b/java/src/test/java/com/google/protobuf/test_bad_identifiers.proto
index 202e8c91..67035fd5 100644
--- a/java/src/test/java/com/google/protobuf/test_bad_identifiers.proto
+++ b/java/src/test/java/com/google/protobuf/test_bad_identifiers.proto
@@ -33,6 +33,7 @@
 // This file tests that various identifiers work as field and type names even
 // though the same identifiers are used internally by the java code generator.
 
+syntax = "proto2";
 
 // Some generic_services option(s) added automatically.
 // See:  http://go/proto2-generic-services-default
@@ -59,12 +60,14 @@ message Descriptor {
   }
   optional NestedDescriptor nested_descriptor = 2;
   enum NestedEnum {
+    UNKNOWN = 0;
     FOO = 1;
   }
 }
 
 message Parser {
   enum ParserEnum {
+    UNKNOWN = 0;
     PARSER = 1;
   }
   optional ParserEnum parser = 1;
@@ -72,6 +75,7 @@ message Parser {
 
 message Deprecated {
   enum TestEnum {
+    UNKNOWN = 0;
     FOO = 1;
 
     // Test if @Deprecated annotation conflicts with Deprecated message name.
@@ -118,6 +122,7 @@ service TestConflictingMethodNames {
 
 message TestConflictingFieldNames {
   enum TestEnum {
+    UNKNOWN = 0;
     FOO = 1;
   }
   message TestMessage {
@@ -142,16 +147,23 @@ message TestConflictingFieldNames {
 
   // This field conflicts with "int32_field" as they both generate
   // the method getInt32FieldList().
-  required int32 int32_field_list = 31;
+  required int32 int32_field_list = 31;  // NO_PROTO3
 
-  extensions 1000 to max;
+  extensions 1000 to max;  // NO_PROTO3
 
   repeated int64 int64_field = 41;
-  extend TestConflictingFieldNames {
+  extend TestConflictingFieldNames {  // NO_PROTO3
     // We don't generate accessors for extensions so the following extension
     // fields don't conflict with the repeated field "int64_field".
-    optional int64 int64_field_count = 1001;
-    optional int64 int64_field_list = 1002;
-  }
+    optional int64 int64_field_count = 1001;  // NO_PROTO3
+    optional int64 int64_field_list = 1002;  // NO_PROTO3
+  }  // NO_PROTO3
 }
 
+message TestMapField {
+  message MapField {}
+  message Pair {}
+  message Message {}
+
+  map<int32, int32> map_field = 1;
+}
diff --git a/java/src/test/java/com/google/protobuf/test_check_utf8.proto b/java/src/test/java/com/google/protobuf/test_check_utf8.proto
index 206946d8..119c1dcb 100644
--- a/java/src/test/java/com/google/protobuf/test_check_utf8.proto
+++ b/java/src/test/java/com/google/protobuf/test_check_utf8.proto
@@ -31,6 +31,7 @@
 // Author: Jacob Butcher (jbaum@google.com)
 //
 // Test file option java_string_check_utf8.
+syntax = "proto2";
 
 package proto2_test_check_utf8;
 
diff --git a/java/src/test/java/com/google/protobuf/test_check_utf8_size.proto b/java/src/test/java/com/google/protobuf/test_check_utf8_size.proto
index fa057a88..f06d76d6 100644
--- a/java/src/test/java/com/google/protobuf/test_check_utf8_size.proto
+++ b/java/src/test/java/com/google/protobuf/test_check_utf8_size.proto
@@ -31,6 +31,7 @@
 // Author: Jacob Butcher (jbaum@google.com)
 //
 // Test file option java_string_check_utf8.
+syntax = "proto2";
 
 package proto2_test_check_utf8_size;
 
diff --git a/java/src/test/java/com/google/protobuf/test_custom_options.proto b/java/src/test/java/com/google/protobuf/test_custom_options.proto
index f6a5ecd4..f8efd455 100644
--- a/java/src/test/java/com/google/protobuf/test_custom_options.proto
+++ b/java/src/test/java/com/google/protobuf/test_custom_options.proto
@@ -32,6 +32,7 @@
 //
 // Test that custom options defined in a proto file's dependencies are properly
 // initialized.
+syntax = "proto2";
 
 package protobuf_unittest;
 
diff --git a/java/src/test/java/com/google/protobuf/test_extra_interfaces.proto b/java/src/test/java/com/google/protobuf/test_extra_interfaces.proto
index 72e05a36..645f57b4 100644
--- a/java/src/test/java/com/google/protobuf/test_extra_interfaces.proto
+++ b/java/src/test/java/com/google/protobuf/test_extra_interfaces.proto
@@ -29,6 +29,7 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Author: Darick Tong (darick@google.com)
+syntax = "proto2";
 
 package protobuf_unittest;
 
diff --git a/python/google/protobuf/descriptor.py b/python/google/protobuf/descriptor.py
index 6da8bb0b..af571b7c 100755
--- a/python/google/protobuf/descriptor.py
+++ b/python/google/protobuf/descriptor.py
@@ -841,9 +841,10 @@ def MakeDescriptor(desc_proto, package='', build_file_if_cpp=True):
         field_proto.number, field_proto.type,
         FieldDescriptor.ProtoTypeToCppProtoType(field_proto.type),
         field_proto.label, None, nested_desc, enum_desc, None, False, None,
-        has_default_value=False)
+        options=field_proto.options, has_default_value=False)
     fields.append(field)
 
   desc_name = '.'.join(full_message_name)
   return Descriptor(desc_proto.name, desc_name, None, None, fields,
-                    nested_types.values(), enum_types.values(), [])
+                    nested_types.values(), enum_types.values(), [],
+                    options=desc_proto.options)
diff --git a/python/google/protobuf/descriptor_database.py b/python/google/protobuf/descriptor_database.py
index 55fb8c70..b10021e9 100644
--- a/python/google/protobuf/descriptor_database.py
+++ b/python/google/protobuf/descriptor_database.py
@@ -133,5 +133,5 @@ def _ExtractSymbols(desc_proto, package):
   for nested_type in desc_proto.nested_type:
     for symbol in _ExtractSymbols(nested_type, message_name):
       yield symbol
-    for enum_type in desc_proto.enum_type:
-      yield '.'.join((message_name, enum_type.name))
+  for enum_type in desc_proto.enum_type:
+    yield '.'.join((message_name, enum_type.name))
diff --git a/python/google/protobuf/descriptor_pool.py b/python/google/protobuf/descriptor_pool.py
index cf234cfa..bcac513a 100644
--- a/python/google/protobuf/descriptor_pool.py
+++ b/python/google/protobuf/descriptor_pool.py
@@ -554,7 +554,7 @@ class DescriptorPool(object):
         field_desc.default_value = field_proto.default_value.lower() == 'true'
       elif field_proto.type == descriptor.FieldDescriptor.TYPE_ENUM:
         field_desc.default_value = field_desc.enum_type.values_by_name[
-            field_proto.default_value].index
+            field_proto.default_value].number
       elif field_proto.type == descriptor.FieldDescriptor.TYPE_BYTES:
         field_desc.default_value = text_encoding.CUnescape(
             field_proto.default_value)
diff --git a/python/google/protobuf/internal/descriptor_database_test.py b/python/google/protobuf/internal/descriptor_database_test.py
index fc65b69a..8970f5c2 100644
--- a/python/google/protobuf/internal/descriptor_database_test.py
+++ b/python/google/protobuf/internal/descriptor_database_test.py
@@ -58,6 +58,8 @@ class DescriptorDatabaseTest(basetest.TestCase):
         'google.protobuf.python.internal.Factory2Enum'))
     self.assertEquals(file_desc_proto, db.FindFileContainingSymbol(
         'google.protobuf.python.internal.Factory2Message.NestedFactory2Enum'))
+    self.assertEquals(file_desc_proto, db.FindFileContainingSymbol(
+        'google.protobuf.python.internal.MessageWithNestedEnumOnly.NestedEnum'))
 
 if __name__ == '__main__':
   basetest.main()
diff --git a/python/google/protobuf/internal/descriptor_pool_test.py b/python/google/protobuf/internal/descriptor_pool_test.py
index d2f85579..11ef61c5 100644
--- a/python/google/protobuf/internal/descriptor_pool_test.py
+++ b/python/google/protobuf/internal/descriptor_pool_test.py
@@ -48,6 +48,7 @@ from google.protobuf.internal import factory_test2_pb2
 from google.protobuf import descriptor
 from google.protobuf import descriptor_database
 from google.protobuf import descriptor_pool
+from google.protobuf import symbol_database
 
 
 class DescriptorPoolTest(basetest.TestCase):
@@ -237,6 +238,32 @@ class DescriptorPoolTest(basetest.TestCase):
     TEST2_FILE.CheckFile(self, self.pool)
 
 
+  def testEnumDefaultValue(self):
+    """Test the default value of enums which don't start at zero."""
+    def _CheckDefaultValue(file_descriptor):
+      default_value = (file_descriptor
+                       .message_types_by_name['DescriptorPoolTest1']
+                       .fields_by_name['nested_enum']
+                       .default_value)
+      self.assertEqual(default_value,
+                       descriptor_pool_test1_pb2.DescriptorPoolTest1.BETA)
+    # First check what the generated descriptor contains.
+    _CheckDefaultValue(descriptor_pool_test1_pb2.DESCRIPTOR)
+    # Then check the generated pool. Normally this is the same descriptor.
+    file_descriptor = symbol_database.Default().pool.FindFileByName(
+        'google/protobuf/internal/descriptor_pool_test1.proto')
+    self.assertIs(file_descriptor, descriptor_pool_test1_pb2.DESCRIPTOR)
+    _CheckDefaultValue(file_descriptor)
+
+    # Then check the dynamic pool and its internal DescriptorDatabase.
+    descriptor_proto = descriptor_pb2.FileDescriptorProto.FromString(
+        descriptor_pool_test1_pb2.DESCRIPTOR.serialized_pb)
+    self.pool.Add(descriptor_proto)
+    # And do the same check as above
+    file_descriptor = self.pool.FindFileByName(
+        'google/protobuf/internal/descriptor_pool_test1.proto')
+    _CheckDefaultValue(file_descriptor)
+
 
 class ProtoFile(object):
 
@@ -328,7 +355,7 @@ class EnumField(object):
     test.assertEqual(descriptor.FieldDescriptor.CPPTYPE_ENUM,
                      field_desc.cpp_type)
     test.assertTrue(field_desc.has_default_value)
-    test.assertEqual(enum_desc.values_by_name[self.default_value].index,
+    test.assertEqual(enum_desc.values_by_name[self.default_value].number,
                      field_desc.default_value)
     test.assertEqual(msg_desc, field_desc.containing_type)
     test.assertEqual(enum_desc, field_desc.enum_type)
diff --git a/python/google/protobuf/internal/descriptor_pool_test1.proto b/python/google/protobuf/internal/descriptor_pool_test1.proto
index 6dfe4ef3..00816b78 100644
--- a/python/google/protobuf/internal/descriptor_pool_test1.proto
+++ b/python/google/protobuf/internal/descriptor_pool_test1.proto
@@ -28,6 +28,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+syntax = "proto2";
+
 package google.protobuf.python.internal;
 
 
diff --git a/python/google/protobuf/internal/descriptor_pool_test2.proto b/python/google/protobuf/internal/descriptor_pool_test2.proto
index fbc84382..e3fa660c 100644
--- a/python/google/protobuf/internal/descriptor_pool_test2.proto
+++ b/python/google/protobuf/internal/descriptor_pool_test2.proto
@@ -28,6 +28,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+syntax = "proto2";
+
 package google.protobuf.python.internal;
 
 import "google/protobuf/internal/descriptor_pool_test1.proto";
diff --git a/python/google/protobuf/internal/descriptor_test.py b/python/google/protobuf/internal/descriptor_test.py
index b3777e39..3924f21a 100755
--- a/python/google/protobuf/internal/descriptor_test.py
+++ b/python/google/protobuf/internal/descriptor_test.py
@@ -665,5 +665,15 @@ class MakeDescriptorTest(basetest.TestCase):
                      descriptor.FieldDescriptor.CPPTYPE_UINT64)
 
 
+  def testMakeDescriptorWithOptions(self):
+    descriptor_proto = descriptor_pb2.DescriptorProto()
+    aggregate_message = unittest_custom_options_pb2.AggregateMessage
+    aggregate_message.DESCRIPTOR.CopyToProto(descriptor_proto)
+    reformed_descriptor = descriptor.MakeDescriptor(descriptor_proto)
+
+    options = reformed_descriptor.GetOptions()
+    self.assertEquals(101,
+                      options.Extensions[unittest_custom_options_pb2.msgopt].i)
+
 if __name__ == '__main__':
   basetest.main()
diff --git a/python/google/protobuf/internal/factory_test1.proto b/python/google/protobuf/internal/factory_test1.proto
index 9f5a3919..d2fbbeec 100644
--- a/python/google/protobuf/internal/factory_test1.proto
+++ b/python/google/protobuf/internal/factory_test1.proto
@@ -30,6 +30,7 @@
 
 // Author: matthewtoia@google.com (Matt Toia)
 
+syntax = "proto2";
 
 package google.protobuf.python.internal;
 
diff --git a/python/google/protobuf/internal/factory_test2.proto b/python/google/protobuf/internal/factory_test2.proto
index 27feb6ce..bb1b54ad 100644
--- a/python/google/protobuf/internal/factory_test2.proto
+++ b/python/google/protobuf/internal/factory_test2.proto
@@ -30,6 +30,7 @@
 
 // Author: matthewtoia@google.com (Matt Toia)
 
+syntax = "proto2";
 
 package google.protobuf.python.internal;
 
@@ -87,6 +88,12 @@ message LoopMessage {
   optional Factory2Message loop = 1;
 }
 
+message MessageWithNestedEnumOnly {
+  enum NestedEnum {
+    NESTED_MESSAGE_ENUM_0 = 0;
+  }
+}
+
 extend Factory1Message {
   optional string another_field = 1002;
 }
diff --git a/python/google/protobuf/internal/generator_test.py b/python/google/protobuf/internal/generator_test.py
index 422fa9a6..14b05cca 100755
--- a/python/google/protobuf/internal/generator_test.py
+++ b/python/google/protobuf/internal/generator_test.py
@@ -35,7 +35,7 @@
 # indirect testing of the protocol compiler output.
 
 """Unittest that directly tests the output of the pure-Python protocol
-compiler.  See //google/protobuf/reflection_test.py for a test which
+compiler.  See //google/protobuf/internal/reflection_test.py for a test which
 further ensures that we can use Python protocol message objects as we expect.
 """
 
@@ -281,6 +281,8 @@ class GeneratorTest(basetest.TestCase):
                      "baz")
     self.assertEqual(message.Extensions[test_bad_identifiers_pb2.service],
                      "qux")
+    self.assertEqual(message.Extensions[test_bad_identifiers_pb2.class_],
+                     "Foo")
 
   def testOneof(self):
     desc = unittest_pb2.TestAllTypes.DESCRIPTOR
diff --git a/python/google/protobuf/internal/import_test_package/BUILD b/python/google/protobuf/internal/import_test_package/BUILD
new file mode 100644
index 00000000..90e59505
--- /dev/null
+++ b/python/google/protobuf/internal/import_test_package/BUILD
@@ -0,0 +1,27 @@
+# Description:
+#   An example package that contains nested protos that are imported from
+#   __init__.py. See testPackageInitializationImport in reflection_test.py for
+#   details.
+
+package(
+    default_visibility = ["//net/proto2/python/internal:__pkg__"],
+)
+
+proto_library(
+    name = "inner_proto",
+    srcs = ["inner.proto"],
+    py_api_version = 2,
+)
+
+proto_library(
+    name = "outer_proto",
+    srcs = ["outer.proto"],
+    py_api_version = 2,
+    deps = [":inner_proto"],
+)
+
+py_library(
+    name = "import_test_package",
+    srcs = ["__init__.py"],
+    deps = [":outer_proto"],
+)
diff --git a/python/google/protobuf/internal/import_test_package/__init__.py b/python/google/protobuf/internal/import_test_package/__init__.py
new file mode 100644
index 00000000..5121dd0e
--- /dev/null
+++ b/python/google/protobuf/internal/import_test_package/__init__.py
@@ -0,0 +1,33 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# https://developers.google.com/protocol-buffers/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Sample module importing a nested proto from itself."""
+
+from google.protobuf.internal.import_test_package import outer_pb2 as myproto
diff --git a/python/google/protobuf/internal/import_test_package/inner.proto b/python/google/protobuf/internal/import_test_package/inner.proto
new file mode 100644
index 00000000..2887c123
--- /dev/null
+++ b/python/google/protobuf/internal/import_test_package/inner.proto
@@ -0,0 +1,37 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto2";
+
+package google.protobuf.python.internal.import_test_package;
+
+message Inner {
+  optional int32 value = 1 [default = 57];
+}
diff --git a/python/google/protobuf/internal/import_test_package/outer.proto b/python/google/protobuf/internal/import_test_package/outer.proto
new file mode 100644
index 00000000..a27fb5c8
--- /dev/null
+++ b/python/google/protobuf/internal/import_test_package/outer.proto
@@ -0,0 +1,39 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto2";
+
+package google.protobuf.python.internal.import_test_package;
+
+import "google/protobuf/internal/import_test_package/inner.proto";
+
+message Outer {
+  optional Inner inner = 1;
+}
diff --git a/python/google/protobuf/internal/message_test.py b/python/google/protobuf/internal/message_test.py
index 48b7ffd4..42e2ad7e 100755
--- a/python/google/protobuf/internal/message_test.py
+++ b/python/google/protobuf/internal/message_test.py
@@ -337,6 +337,20 @@ class MessageTest(basetest.TestCase):
     empty.ParseFromString(populated.SerializeToString())
     self.assertEqual(str(empty), '')
 
+  def testRepeatedNestedFieldIteration(self):
+    msg = unittest_pb2.TestAllTypes()
+    msg.repeated_nested_message.add(bb=1)
+    msg.repeated_nested_message.add(bb=2)
+    msg.repeated_nested_message.add(bb=3)
+    msg.repeated_nested_message.add(bb=4)
+
+    self.assertEquals([1, 2, 3, 4],
+                      [m.bb for m in msg.repeated_nested_message])
+    self.assertEquals([4, 3, 2, 1],
+                      [m.bb for m in reversed(msg.repeated_nested_message)])
+    self.assertEquals([4, 3, 2, 1],
+                      [m.bb for m in msg.repeated_nested_message[::-1]])
+
   def testSortingRepeatedScalarFieldsDefaultComparator(self):
     """Check some different types with the default comparator."""
     message = unittest_pb2.TestAllTypes()
@@ -641,6 +655,32 @@ class MessageTest(basetest.TestCase):
     m2.ParseFromString(m.SerializeToString())
     self.assertEqual('oneof_uint32', m2.WhichOneof('oneof_field'))
 
+  def testOneofCopyFrom(self):
+    m = unittest_pb2.TestAllTypes()
+    m.oneof_uint32 = 11
+    m2 = unittest_pb2.TestAllTypes()
+    m2.CopyFrom(m)
+    self.assertEqual('oneof_uint32', m2.WhichOneof('oneof_field'))
+
+  def testOneofNestedMergeFrom(self):
+    m = unittest_pb2.NestedTestAllTypes()
+    m.payload.oneof_uint32 = 11
+    m2 = unittest_pb2.NestedTestAllTypes()
+    m2.payload.oneof_bytes = b'bb'
+    m2.child.payload.oneof_bytes = b'bb'
+    m2.MergeFrom(m)
+    self.assertEqual('oneof_uint32', m2.payload.WhichOneof('oneof_field'))
+    self.assertEqual('oneof_bytes', m2.child.payload.WhichOneof('oneof_field'))
+
+  def testOneofClear(self):
+    m = unittest_pb2.TestAllTypes()
+    m.oneof_uint32 = 11
+    m.Clear()
+    self.assertIsNone(m.WhichOneof('oneof_field'))
+    m.oneof_bytes = b'bb'
+    self.assertTrue(m.HasField('oneof_field'))
+
+
   def testSortEmptyRepeatedCompositeContainer(self):
     """Exercise a scenario that has led to segfaults in the past.
     """
diff --git a/python/google/protobuf/internal/missing_enum_values.proto b/python/google/protobuf/internal/missing_enum_values.proto
index e90f0cd3..161fc5e1 100644
--- a/python/google/protobuf/internal/missing_enum_values.proto
+++ b/python/google/protobuf/internal/missing_enum_values.proto
@@ -28,6 +28,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+syntax = "proto2";
+
 package google.protobuf.python.internal;
 
 message TestEnumValues {
diff --git a/python/google/protobuf/internal/more_extensions.proto b/python/google/protobuf/internal/more_extensions.proto
index c04e597f..78f14673 100644
--- a/python/google/protobuf/internal/more_extensions.proto
+++ b/python/google/protobuf/internal/more_extensions.proto
@@ -30,6 +30,7 @@
 
 // Author: robinson@google.com (Will Robinson)
 
+syntax = "proto2";
 
 package google.protobuf.internal;
 
diff --git a/python/google/protobuf/internal/more_extensions_dynamic.proto b/python/google/protobuf/internal/more_extensions_dynamic.proto
index 88bd9c1b..11f85ef6 100644
--- a/python/google/protobuf/internal/more_extensions_dynamic.proto
+++ b/python/google/protobuf/internal/more_extensions_dynamic.proto
@@ -34,6 +34,7 @@
 // generated C++ type is available for the extendee, but the extension is
 // defined in a file whose C++ type is not in the binary.
 
+syntax = "proto2";
 
 import "google/protobuf/internal/more_extensions.proto";
 
diff --git a/python/google/protobuf/internal/more_messages.proto b/python/google/protobuf/internal/more_messages.proto
index 61db66c5..2c6ab9ef 100644
--- a/python/google/protobuf/internal/more_messages.proto
+++ b/python/google/protobuf/internal/more_messages.proto
@@ -30,6 +30,7 @@
 
 // Author: robinson@google.com (Will Robinson)
 
+syntax = "proto2";
 
 package google.protobuf.internal;
 
diff --git a/python/google/protobuf/internal/proto_builder_test.py b/python/google/protobuf/internal/proto_builder_test.py
new file mode 100644
index 00000000..c74db7e7
--- /dev/null
+++ b/python/google/protobuf/internal/proto_builder_test.py
@@ -0,0 +1,77 @@
+#! /usr/bin/python
+#
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# https://developers.google.com/protocol-buffers/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Tests for google.protobuf.proto_builder."""
+
+from google.apputils import basetest
+
+from google.protobuf import descriptor_pb2
+from google.protobuf import descriptor_pool
+from google.protobuf import proto_builder
+from google.protobuf import text_format
+
+
+class ProtoBuilderTest(basetest.TestCase):
+
+  def setUp(self):
+    self._fields = {
+        'foo': descriptor_pb2.FieldDescriptorProto.TYPE_INT64,
+        'bar': descriptor_pb2.FieldDescriptorProto.TYPE_STRING,
+        }
+
+  def testMakeSimpleProtoClass(self):
+    """Test that we can create a proto class."""
+    proto_cls = proto_builder.MakeSimpleProtoClass(
+        self._fields,
+        full_name='net.proto2.python.public.proto_builder_test.Test')
+    proto = proto_cls()
+    proto.foo = 12345
+    proto.bar = 'asdf'
+    self.assertMultiLineEqual(
+        'bar: "asdf"\nfoo: 12345\n', text_format.MessageToString(proto))
+
+  def testMakeSameProtoClassTwice(self):
+    """Test that the DescriptorPool is used."""
+    pool = descriptor_pool.DescriptorPool()
+    proto_cls1 = proto_builder.MakeSimpleProtoClass(
+        self._fields,
+        full_name='net.proto2.python.public.proto_builder_test.Test',
+        pool=pool)
+    proto_cls2 = proto_builder.MakeSimpleProtoClass(
+        self._fields,
+        full_name='net.proto2.python.public.proto_builder_test.Test',
+        pool=pool)
+    self.assertIs(proto_cls1.DESCRIPTOR, proto_cls2.DESCRIPTOR)
+
+
+if __name__ == '__main__':
+  basetest.main()
diff --git a/python/google/protobuf/internal/python_message.py b/python/google/protobuf/internal/python_message.py
index a5c26f45..6fda6ae0 100755
--- a/python/google/protobuf/internal/python_message.py
+++ b/python/google/protobuf/internal/python_message.py
@@ -306,6 +306,17 @@ def _DefaultValueConstructorForField(field):
   return MakeScalarDefault
 
 
+def _ReraiseTypeErrorWithFieldName(message_name, field_name):
+  """Re-raise the currently-handled TypeError with the field name added."""
+  exc = sys.exc_info()[1]
+  if len(exc.args) == 1 and type(exc) is TypeError:
+    # simple TypeError; add field name to exception message
+    exc = TypeError('%s for field %s.%s' % (str(exc), message_name, field_name))
+
+  # re-raise possibly-amended exception with original traceback:
+  raise type(exc), exc, sys.exc_info()[2]
+
+
 def _AddInitMethod(message_descriptor, cls):
   """Adds an __init__ method to cls."""
   fields = message_descriptor.fields
@@ -338,10 +349,16 @@ def _AddInitMethod(message_descriptor, cls):
         self._fields[field] = copy
       elif field.cpp_type == _FieldDescriptor.CPPTYPE_MESSAGE:
         copy = field._default_constructor(self)
-        copy.MergeFrom(field_value)
+        try:
+          copy.MergeFrom(field_value)
+        except TypeError:
+          _ReraiseTypeErrorWithFieldName(message_descriptor.name, field_name)
         self._fields[field] = copy
       else:
-        setattr(self, field_name, field_value)
+        try:
+          setattr(self, field_name, field_value)
+        except TypeError:
+          _ReraiseTypeErrorWithFieldName(message_descriptor.name, field_name)
 
   init.__module__ = None
   init.__doc__ = None
@@ -691,6 +708,7 @@ def _AddClearMethod(message_descriptor, cls):
     # Clear fields.
     self._fields = {}
     self._unknown_fields = ()
+    self._oneofs = {}
     self._Modified()
   cls.Clear = Clear
 
@@ -993,6 +1011,8 @@ def _AddMergeFromMethod(cls):
           field_value.MergeFrom(value)
       else:
         self._fields[field] = value
+        if field.containing_oneof:
+          self._UpdateOneofState(field)
 
     if msg._unknown_fields:
       if not self._unknown_fields:
diff --git a/python/google/protobuf/internal/reflection_test.py b/python/google/protobuf/internal/reflection_test.py
index d59815d0..6b24b092 100755
--- a/python/google/protobuf/internal/reflection_test.py
+++ b/python/google/protobuf/internal/reflection_test.py
@@ -35,8 +35,6 @@
 pure-Python protocol compiler.
 """
 
-__author__ = 'robinson@google.com (Will Robinson)'
-
 import copy
 import gc
 import operator
@@ -1252,15 +1250,18 @@ class ReflectionTest(basetest.TestCase):
 
     # Try something that *is* an extension handle, just not for
     # this message...
-    unknown_handle = more_extensions_pb2.optional_int_extension
-    self.assertRaises(KeyError, extendee_proto.HasExtension,
-                      unknown_handle)
-    self.assertRaises(KeyError, extendee_proto.ClearExtension,
-                      unknown_handle)
-    self.assertRaises(KeyError, extendee_proto.Extensions.__getitem__,
-                      unknown_handle)
-    self.assertRaises(KeyError, extendee_proto.Extensions.__setitem__,
-                      unknown_handle, 5)
+    for unknown_handle in (more_extensions_pb2.optional_int_extension,
+                           more_extensions_pb2.optional_message_extension,
+                           more_extensions_pb2.repeated_int_extension,
+                           more_extensions_pb2.repeated_message_extension):
+      self.assertRaises(KeyError, extendee_proto.HasExtension,
+                        unknown_handle)
+      self.assertRaises(KeyError, extendee_proto.ClearExtension,
+                        unknown_handle)
+      self.assertRaises(KeyError, extendee_proto.Extensions.__getitem__,
+                        unknown_handle)
+      self.assertRaises(KeyError, extendee_proto.Extensions.__setitem__,
+                        unknown_handle, 5)
 
     # Try call HasExtension() with a valid handle, but for a
     # *repeated* field.  (Just as with non-extension repeated
@@ -1669,16 +1670,15 @@ class ReflectionTest(basetest.TestCase):
     proto.optional_string = str('Testing')
     self.assertEqual(proto.optional_string, unicode('Testing'))
 
-    # Try to assign a 'str' value which contains bytes that aren't 7-bit ASCII.
+    # Try to assign a 'bytes' object which contains non-UTF-8.
     self.assertRaises(ValueError,
                       setattr, proto, 'optional_string', b'a\x80a')
-    if str is bytes:  # PY2
-      # Assign a 'str' object which contains a UTF-8 encoded string.
-      self.assertRaises(ValueError,
-                        setattr, proto, 'optional_string', 'Тест')
-    else:
-      proto.optional_string = 'Тест'
-    # No exception thrown.
+    # No exception: Assign already encoded UTF-8 bytes to a string field.
+    utf8_bytes = u'Тест'.encode('utf-8')
+    proto.optional_string = utf8_bytes
+    # No exception: Assign the a non-ascii unicode object.
+    proto.optional_string = u'Тест'
+    # No exception thrown (normal str assignment containing ASCII).
     proto.optional_string = 'abc'
 
   def testStringUTF8Serialization(self):
@@ -1774,6 +1774,24 @@ class ReflectionTest(basetest.TestCase):
     proto.optionalgroup.SetInParent()
     self.assertTrue(proto.HasField('optionalgroup'))
 
+  def testPackageInitializationImport(self):
+    """Test that we can import nested messages from their __init__.py.
+
+    Such setup is not trivial since at the time of processing of __init__.py one
+    can't refer to its submodules by name in code, so expressions like
+    google.protobuf.internal.import_test_package.inner_pb2
+    don't work. They do work in imports, so we have assign an alias at import
+    and then use that alias in generated code.
+    """
+    # We import here since it's the import that used to fail, and we want
+    # the failure to have the right context.
+    # pylint: disable=g-import-not-at-top
+    from google.protobuf.internal import import_test_package
+    # pylint: enable=g-import-not-at-top
+    msg = import_test_package.myproto.Outer()
+    # Just check the default value.
+    self.assertEqual(57, msg.inner.value)
+
 
 #  Since we had so many tests for protocol buffer equality, we broke these out
 #  into separate TestCase classes.
@@ -2802,6 +2820,9 @@ class OptionsTest(basetest.TestCase):
 
 class ClassAPITest(basetest.TestCase):
 
+  @basetest.unittest.skipIf(
+      api_implementation.Type() == 'cpp' and api_implementation.Version() == 2,
+      'C++ implementation requires a call to MakeDescriptor()')
   def testMakeClassWithNestedDescriptor(self):
     leaf_desc = descriptor.Descriptor('leaf', 'package.parent.child.leaf', '',
                                       containing_type=None, fields=[],
diff --git a/python/google/protobuf/internal/test_bad_identifiers.proto b/python/google/protobuf/internal/test_bad_identifiers.proto
index 9eb18cb0..29fa38a2 100644
--- a/python/google/protobuf/internal/test_bad_identifiers.proto
+++ b/python/google/protobuf/internal/test_bad_identifiers.proto
@@ -30,6 +30,7 @@
 
 // Author: kenton@google.com (Kenton Varda)
 
+syntax = "proto2";
 
 package protobuf_unittest;
 
@@ -39,13 +40,15 @@ message TestBadIdentifiers {
   extensions 100 to max;
 }
 
-// Make sure these reasonable extension names don't conflict with internal
-// variables.
 extend TestBadIdentifiers {
+  // Make sure these reasonable extension names don't conflict with internal
+  // variables.
   optional string message = 100 [default="foo"];
   optional string descriptor = 101 [default="bar"];
   optional string reflection = 102 [default="baz"];
   optional string service = 103 [default="qux"];
+  // And Python keywords.
+  optional string class = 104 [default="Foo"];
 }
 
 message AnotherMessage {}
diff --git a/python/google/protobuf/internal/text_format_test.py b/python/google/protobuf/internal/text_format_test.py
index b0a3a5f7..55e3c2c8 100755
--- a/python/google/protobuf/internal/text_format_test.py
+++ b/python/google/protobuf/internal/text_format_test.py
@@ -69,13 +69,18 @@ class TextFormatTest(basetest.TestCase):
     message.my_string = '115'
     message.my_int = 101
     message.my_float = 111
+    message.optional_nested_message.oo = 0
+    message.optional_nested_message.bb = 1
     self.CompareToGoldenText(
         self.RemoveRedundantZeros(text_format.MessageToString(
             message, use_index_order=True)),
-        'my_string: \"115\"\nmy_int: 101\nmy_float: 111\n')
+        'my_string: \"115\"\nmy_int: 101\nmy_float: 111\n'
+        'optional_nested_message {\n  oo: 0\n  bb: 1\n}\n')
     self.CompareToGoldenText(
         self.RemoveRedundantZeros(text_format.MessageToString(
-            message)), 'my_int: 101\nmy_string: \"115\"\nmy_float: 111\n')
+            message)),
+        'my_int: 101\nmy_string: \"115\"\nmy_float: 111\n'
+        'optional_nested_message {\n  bb: 1\n  oo: 0\n}\n')
 
   def testPrintAllExtensions(self):
     message = unittest_pb2.TestAllExtensions()
@@ -511,7 +516,7 @@ class TextFormatTest(basetest.TestCase):
                      message.repeated_string[4])
     self.assertEqual(SLASH + 'x20', message.repeated_string[5])
 
-  def testMergeRepeatedScalars(self):
+  def testMergeDuplicateScalars(self):
     message = unittest_pb2.TestAllTypes()
     text = ('optional_int32: 42 '
             'optional_int32: 67')
@@ -519,7 +524,7 @@ class TextFormatTest(basetest.TestCase):
     self.assertIs(r, message)
     self.assertEqual(67, message.optional_int32)
 
-  def testParseRepeatedScalars(self):
+  def testParseDuplicateScalars(self):
     message = unittest_pb2.TestAllTypes()
     text = ('optional_int32: 42 '
             'optional_int32: 67')
@@ -529,7 +534,7 @@ class TextFormatTest(basetest.TestCase):
          'have multiple "optional_int32" fields.'),
         text_format.Parse, text, message)
 
-  def testMergeRepeatedNestedMessageScalars(self):
+  def testMergeDuplicateNestedMessageScalars(self):
     message = unittest_pb2.TestAllTypes()
     text = ('optional_nested_message { bb: 1 } '
             'optional_nested_message { bb: 2 }')
@@ -537,7 +542,7 @@ class TextFormatTest(basetest.TestCase):
     self.assertTrue(r is message)
     self.assertEqual(2, message.optional_nested_message.bb)
 
-  def testParseRepeatedNestedMessageScalars(self):
+  def testParseDuplicateNestedMessageScalars(self):
     message = unittest_pb2.TestAllTypes()
     text = ('optional_nested_message { bb: 1 } '
             'optional_nested_message { bb: 2 }')
@@ -547,7 +552,7 @@ class TextFormatTest(basetest.TestCase):
          'should not have multiple "bb" fields.'),
         text_format.Parse, text, message)
 
-  def testMergeRepeatedExtensionScalars(self):
+  def testMergeDuplicateExtensionScalars(self):
     message = unittest_pb2.TestAllExtensions()
     text = ('[protobuf_unittest.optional_int32_extension]: 42 '
             '[protobuf_unittest.optional_int32_extension]: 67')
@@ -556,7 +561,7 @@ class TextFormatTest(basetest.TestCase):
         67,
         message.Extensions[unittest_pb2.optional_int32_extension])
 
-  def testParseRepeatedExtensionScalars(self):
+  def testParseDuplicateExtensionScalars(self):
     message = unittest_pb2.TestAllExtensions()
     text = ('[protobuf_unittest.optional_int32_extension]: 42 '
             '[protobuf_unittest.optional_int32_extension]: 67')
diff --git a/python/google/protobuf/internal/type_checkers.py b/python/google/protobuf/internal/type_checkers.py
index 56d26460..118725da 100755
--- a/python/google/protobuf/internal/type_checkers.py
+++ b/python/google/protobuf/internal/type_checkers.py
@@ -154,14 +154,13 @@ class UnicodeValueChecker(object):
                  (proposed_value, type(proposed_value), (bytes, unicode)))
       raise TypeError(message)
 
-    # If the value is of type 'bytes' make sure that it is in 7-bit ASCII
-    # encoding.
+    # If the value is of type 'bytes' make sure that it is valid UTF-8 data.
     if isinstance(proposed_value, bytes):
       try:
-        proposed_value = proposed_value.decode('ascii')
+        proposed_value = proposed_value.decode('utf-8')
       except UnicodeDecodeError:
-        raise ValueError('%.1024r has type bytes, but isn\'t in 7-bit ASCII '
-                         'encoding. Non-ASCII strings must be converted to '
+        raise ValueError('%.1024r has type bytes, but isn\'t valid UTF-8 '
+                         'encoding. Non-UTF-8 strings must be converted to '
                          'unicode objects before being added.' %
                          (proposed_value))
     return proposed_value
diff --git a/python/google/protobuf/internal/unknown_fields_test.py b/python/google/protobuf/internal/unknown_fields_test.py
index 71775609..a4dc1f7c 100755
--- a/python/google/protobuf/internal/unknown_fields_test.py
+++ b/python/google/protobuf/internal/unknown_fields_test.py
@@ -38,12 +38,16 @@ __author__ = 'bohdank@google.com (Bohdan Koval)'
 from google.apputils import basetest
 from google.protobuf import unittest_mset_pb2
 from google.protobuf import unittest_pb2
+from google.protobuf.internal import api_implementation
 from google.protobuf.internal import encoder
 from google.protobuf.internal import missing_enum_values_pb2
 from google.protobuf.internal import test_util
 from google.protobuf.internal import type_checkers
 
 
+@basetest.unittest.skipIf(
+    api_implementation.Type() == 'cpp' and api_implementation.Version() == 2,
+    'C++ implementation does not expose unknown fields to Python')
 class UnknownFieldsTest(basetest.TestCase):
 
   def setUp(self):
@@ -175,7 +179,10 @@ class UnknownFieldsTest(basetest.TestCase):
     self.assertNotEqual(self.empty_message, message)
 
 
-class UnknownFieldsTest(basetest.TestCase):
+@basetest.unittest.skipIf(
+    api_implementation.Type() == 'cpp' and api_implementation.Version() == 2,
+    'C++ implementation does not expose unknown fields to Python')
+class UnknownEnumValuesTest(basetest.TestCase):
 
   def setUp(self):
     self.descriptor = missing_enum_values_pb2.TestEnumValues.DESCRIPTOR
diff --git a/python/google/protobuf/message.py b/python/google/protobuf/message.py
index c186452a..88ed9f4c 100755
--- a/python/google/protobuf/message.py
+++ b/python/google/protobuf/message.py
@@ -233,12 +233,21 @@ class Message(object):
     raise NotImplementedError
 
   def HasField(self, field_name):
-    """Checks if a certain field is set for the message. Note if the
-    field_name is not defined in the message descriptor, ValueError will be
-    raised."""
+    """Checks if a certain field is set for the message, or if any field inside
+    a oneof group is set.  Note that if the field_name is not defined in the
+    message descriptor, ValueError will be raised."""
     raise NotImplementedError
 
   def ClearField(self, field_name):
+    """Clears the contents of a given field, or the field set inside a oneof
+    group.  If the name neither refers to a defined field or oneof group,
+    ValueError is raised."""
+    raise NotImplementedError
+
+  def WhichOneof(self, oneof_group):
+    """Returns the name of the field that is set inside a oneof group, or
+    None if no field is set.  If no group with the given name exists, ValueError
+    will be raised."""
     raise NotImplementedError
 
   def HasExtension(self, extension_handle):
diff --git a/python/google/protobuf/proto_builder.py b/python/google/protobuf/proto_builder.py
new file mode 100644
index 00000000..1fa28f1a
--- /dev/null
+++ b/python/google/protobuf/proto_builder.py
@@ -0,0 +1,98 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# https://developers.google.com/protocol-buffers/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Dynamic Protobuf class creator."""
+
+import hashlib
+import os
+
+from google.protobuf import descriptor_pb2
+from google.protobuf import message_factory
+
+
+def _GetMessageFromFactory(factory, full_name):
+  """Get a proto class from the MessageFactory by name.
+
+  Args:
+    factory: a MessageFactory instance.
+    full_name: str, the fully qualified name of the proto type.
+  Returns:
+    a class, for the type identified by full_name.
+  Raises:
+    KeyError, if the proto is not found in the factory's descriptor pool.
+  """
+  proto_descriptor = factory.pool.FindMessageTypeByName(full_name)
+  proto_cls = factory.GetPrototype(proto_descriptor)
+  return proto_cls
+
+
+def MakeSimpleProtoClass(fields, full_name, pool=None):
+  """Create a Protobuf class whose fields are basic types.
+
+  Note: this doesn't validate field names!
+
+  Args:
+    fields: dict of {name: field_type} mappings for each field in the proto.
+    full_name: str, the fully-qualified name of the proto type.
+    pool: optional DescriptorPool instance.
+  Returns:
+    a class, the new protobuf class with a FileDescriptor.
+  """
+  factory = message_factory.MessageFactory(pool=pool)
+  try:
+    proto_cls = _GetMessageFromFactory(factory, full_name)
+    return proto_cls
+  except KeyError:
+    # The factory's DescriptorPool doesn't know about this class yet.
+    pass
+
+  # Use a consistent file name that is unlikely to conflict with any imported
+  # proto files.
+  fields_hash = hashlib.sha1()
+  for f_name, f_type in sorted(fields.items()):
+    fields_hash.update(f_name.encode('utf8'))
+    fields_hash.update(str(f_type).encode('utf8'))
+  proto_file_name = fields_hash.hexdigest() + '.proto'
+
+  package, name = full_name.rsplit('.', 1)
+  file_proto = descriptor_pb2.FileDescriptorProto()
+  file_proto.name = os.path.join(package.replace('.', '/'), proto_file_name)
+  file_proto.package = package
+  desc_proto = file_proto.message_type.add()
+  desc_proto.name = name
+  for f_number, (f_name, f_type) in enumerate(sorted(fields.items()), 1):
+    field_proto = desc_proto.field.add()
+    field_proto.name = f_name
+    field_proto.number = f_number
+    field_proto.label = descriptor_pb2.FieldDescriptorProto.LABEL_OPTIONAL
+    field_proto.type = f_type
+
+  factory.pool.Add(file_proto)
+  return _GetMessageFromFactory(factory, full_name)
diff --git a/python/google/protobuf/pyext/cpp_message.py b/python/google/protobuf/pyext/cpp_message.py
index dcf34a02..037bb72c 100644
--- a/python/google/protobuf/pyext/cpp_message.py
+++ b/python/google/protobuf/pyext/cpp_message.py
@@ -53,9 +53,5 @@ def NewMessage(bases, message_descriptor, dictionary):
 
 
 def InitMessage(message_descriptor, cls):
-  """Constructs a new message instance (called before instance's __init__)."""
-
-  def SubInit(self, **kwargs):
-    super(cls, self).__init__(message_descriptor, **kwargs)
-  cls.__init__ = SubInit
+  """Finalizes the creation of a message class."""
   cls.AddDescriptors(message_descriptor)
diff --git a/python/google/protobuf/pyext/descriptor.cc b/python/google/protobuf/pyext/descriptor.cc
index 3f7be73c..55bb0b72 100644
--- a/python/google/protobuf/pyext/descriptor.cc
+++ b/python/google/protobuf/pyext/descriptor.cc
@@ -35,6 +35,7 @@
 
 #include <google/protobuf/descriptor.pb.h>
 #include <google/protobuf/pyext/descriptor.h>
+#include <google/protobuf/pyext/message.h>
 #include <google/protobuf/pyext/scoped_pyobject_ptr.h>
 
 #define C(str) const_cast<char*>(str)
@@ -46,7 +47,7 @@
     #error "Python 3.0 - 3.2 are not supported."
   #else
   #define PyString_AsString(ob) \
-    (PyUnicode_Check(ob)? PyUnicode_AsUTF8(ob): PyBytes_AS_STRING(ob))
+    (PyUnicode_Check(ob)? PyUnicode_AsUTF8(ob): PyBytes_AsString(ob))
   #endif
 #endif
 
@@ -65,10 +66,80 @@ namespace python {
 
 static google::protobuf::DescriptorPool* g_descriptor_pool = NULL;
 
+namespace cmessage_descriptor {
+
+static void Dealloc(CMessageDescriptor* self) {
+  Py_TYPE(self)->tp_free(reinterpret_cast<PyObject*>(self));
+}
+
+static PyObject* GetFullName(CMessageDescriptor* self, void *closure) {
+  return PyString_FromStringAndSize(
+      self->descriptor->full_name().c_str(),
+      self->descriptor->full_name().size());
+}
+
+static PyObject* GetName(CMessageDescriptor *self, void *closure) {
+  return PyString_FromStringAndSize(
+      self->descriptor->name().c_str(),
+      self->descriptor->name().size());
+}
+
+static PyGetSetDef Getters[] = {
+  { C("full_name"), (getter)GetFullName, NULL, "Full name", NULL},
+  { C("name"), (getter)GetName, NULL, "Unqualified name", NULL},
+  {NULL}
+};
+
+}  // namespace cmessage_descriptor
+
+PyTypeObject CMessageDescriptor_Type = {
+  PyVarObject_HEAD_INIT(&PyType_Type, 0)
+  C("google.protobuf.internal."
+    "_net_proto2___python."
+    "CMessageDescriptor"),              // tp_name
+  sizeof(CMessageDescriptor),           // tp_basicsize
+  0,                                    // tp_itemsize
+  (destructor)cmessage_descriptor::Dealloc,  // tp_dealloc
+  0,                                    // tp_print
+  0,                                    // tp_getattr
+  0,                                    // tp_setattr
+  0,                                    // tp_compare
+  0,                                    // tp_repr
+  0,                                    // tp_as_number
+  0,                                    // tp_as_sequence
+  0,                                    // tp_as_mapping
+  0,                                    // tp_hash
+  0,                                    // tp_call
+  0,                                    // tp_str
+  0,                                    // tp_getattro
+  0,                                    // tp_setattro
+  0,                                    // tp_as_buffer
+  Py_TPFLAGS_DEFAULT,                   // tp_flags
+  C("A Message Descriptor"),            // tp_doc
+  0,                                    // tp_traverse
+  0,                                    // tp_clear
+  0,                                    // tp_richcompare
+  0,                                    // tp_weaklistoffset
+  0,                                    // tp_iter
+  0,                                    // tp_iternext
+  0,                                    // tp_methods
+  0,                                    // tp_members
+  cmessage_descriptor::Getters,         // tp_getset
+  0,                                    // tp_base
+  0,                                    // tp_dict
+  0,                                    // tp_descr_get
+  0,                                    // tp_descr_set
+  0,                                    // tp_dictoffset
+  0,                                    // tp_init
+  PyType_GenericAlloc,                  // tp_alloc
+  PyType_GenericNew,                    // tp_new
+  PyObject_Del,                         // tp_free
+};
+
+
 namespace cfield_descriptor {
 
 static void Dealloc(CFieldDescriptor* self) {
-  Py_CLEAR(self->descriptor_field);
   Py_TYPE(self)->tp_free(reinterpret_cast<PyObject*>(self));
 }
 
@@ -98,7 +169,7 @@ static PyObject* GetID(CFieldDescriptor *self, void *closure) {
 
 static PyGetSetDef Getters[] = {
   { C("full_name"), (getter)GetFullName, NULL, "Full name", NULL},
-  { C("name"), (getter)GetName, NULL, "last name", NULL},
+  { C("name"), (getter)GetName, NULL, "Unqualified name", NULL},
   { C("cpp_type"), (getter)GetCppType, NULL, "C++ Type", NULL},
   { C("label"), (getter)GetLabel, NULL, "Label", NULL},
   { C("id"), (getter)GetID, NULL, "ID", NULL},
@@ -151,13 +222,56 @@ PyTypeObject CFieldDescriptor_Type = {
   PyObject_Del,                         // tp_free
 };
 
+
 namespace cdescriptor_pool {
 
-static void Dealloc(CDescriptorPool* self) {
+PyDescriptorPool* NewDescriptorPool() {
+  PyDescriptorPool* cdescriptor_pool = PyObject_New(
+      PyDescriptorPool, &PyDescriptorPool_Type);
+  if (cdescriptor_pool == NULL) {
+    return NULL;
+  }
+
+  // Build a DescriptorPool for messages only declared in Python libraries.
+  // generated_pool() contains all messages linked in C++ libraries, and is used
+  // as underlay.
+  cdescriptor_pool->pool = new google::protobuf::DescriptorPool(
+      google::protobuf::DescriptorPool::generated_pool());
+
+  // TODO(amauryfa): Rewrite the SymbolDatabase in C so that it uses the same
+  // storage.
+  cdescriptor_pool->classes_by_descriptor =
+      new PyDescriptorPool::ClassesByMessageMap();
+
+  return cdescriptor_pool;
+}
+
+static void Dealloc(PyDescriptorPool* self) {
+  for (auto it : (*self->classes_by_descriptor)) {
+    Py_DECREF(it.second);
+  }
+  delete self->classes_by_descriptor;
   Py_TYPE(self)->tp_free(reinterpret_cast<PyObject*>(self));
 }
 
-static PyObject* NewCDescriptor(
+const google::protobuf::Descriptor* FindMessageTypeByName(PyDescriptorPool* self,
+                                                const string& name) {
+  return self->pool->FindMessageTypeByName(name);
+}
+
+static PyObject* NewCMessageDescriptor(
+    const google::protobuf::Descriptor* message_descriptor) {
+  CMessageDescriptor* cmessage_descriptor = PyObject_New(
+      CMessageDescriptor, &CMessageDescriptor_Type);
+  if (cmessage_descriptor == NULL) {
+    return NULL;
+  }
+  cmessage_descriptor->descriptor = message_descriptor;
+
+  return reinterpret_cast<PyObject*>(cmessage_descriptor);
+}
+
+static PyObject* NewCFieldDescriptor(
     const google::protobuf::FieldDescriptor* field_descriptor) {
   CFieldDescriptor* cfield_descriptor = PyObject_New(
       CFieldDescriptor, &CFieldDescriptor_Type);
@@ -165,12 +279,61 @@ static PyObject* NewCDescriptor(
     return NULL;
   }
   cfield_descriptor->descriptor = field_descriptor;
-  cfield_descriptor->descriptor_field = NULL;
 
   return reinterpret_cast<PyObject*>(cfield_descriptor);
 }
 
-PyObject* FindFieldByName(CDescriptorPool* self, PyObject* name) {
+// Add a message class to our database.
+const google::protobuf::Descriptor* RegisterMessageClass(
+    PyDescriptorPool* self, PyObject *message_class, PyObject* descriptor) {
+  ScopedPyObjectPtr full_message_name(
+      PyObject_GetAttrString(descriptor, "full_name"));
+  const char* full_name = PyString_AsString(full_message_name);
+  if (full_name == NULL) {
+    return NULL;
+  }
+  const Descriptor *message_descriptor =
+      self->pool->FindMessageTypeByName(full_name);
+  if (!message_descriptor) {
+    PyErr_Format(PyExc_TypeError, "Could not find C++ descriptor for '%s'",
+                 full_name);
+    return NULL;
+  }
+  Py_INCREF(message_class);
+  auto ret = self->classes_by_descriptor->insert(
+      make_pair(message_descriptor, message_class));
+  if (!ret.second) {
+    // Update case: DECREF the previous value.
+    Py_DECREF(ret.first->second);
+    ret.first->second = message_class;
+  }
+
+  // Also add the C++ descriptor to the Python descriptor class.
+  ScopedPyObjectPtr cdescriptor(NewCMessageDescriptor(message_descriptor));
+  if (cdescriptor == NULL) {
+    return NULL;
+  }
+  if (PyObject_SetAttrString(
+          descriptor, "_cdescriptor", cdescriptor) < 0) {
+      return NULL;
+  }
+  return message_descriptor;
+}
+
+// Retrieve the message class added to our database.
+PyObject *GetMessageClass(PyDescriptorPool* self,
+                          const Descriptor *message_descriptor) {
+  auto ret = self->classes_by_descriptor->find(message_descriptor);
+  if (ret == self->classes_by_descriptor->end()) {
+    PyErr_Format(PyExc_TypeError, "No message class registered for '%s'",
+                 message_descriptor->full_name().c_str());
+    return NULL;
+  } else {
+    return ret->second;
+  }
+}
+
+PyObject* FindFieldByName(PyDescriptorPool* self, PyObject* name) {
   const char* full_field_name = PyString_AsString(name);
   if (full_field_name == NULL) {
     return NULL;
@@ -186,10 +349,10 @@ PyObject* FindFieldByName(CDescriptorPool* self, PyObject* name) {
     return NULL;
   }
 
-  return NewCDescriptor(field_descriptor);
+  return NewCFieldDescriptor(field_descriptor);
 }
 
-PyObject* FindExtensionByName(CDescriptorPool* self, PyObject* arg) {
+PyObject* FindExtensionByName(PyDescriptorPool* self, PyObject* arg) {
   const char* full_field_name = PyString_AsString(arg);
   if (full_field_name == NULL) {
     return NULL;
@@ -203,7 +366,7 @@ PyObject* FindExtensionByName(CDescriptorPool* self, PyObject* arg) {
     return NULL;
   }
 
-  return NewCDescriptor(field_descriptor);
+  return NewCFieldDescriptor(field_descriptor);
 }
 
 static PyMethodDef Methods[] = {
@@ -220,12 +383,12 @@ static PyMethodDef Methods[] = {
 
 }  // namespace cdescriptor_pool
 
-PyTypeObject CDescriptorPool_Type = {
+PyTypeObject PyDescriptorPool_Type = {
   PyVarObject_HEAD_INIT(&PyType_Type, 0)
   C("google.protobuf.internal."
     "_net_proto2___python."
     "CFieldDescriptor"),               // tp_name
-  sizeof(CDescriptorPool),             // tp_basicsize
+  sizeof(PyDescriptorPool),            // tp_basicsize
   0,                                   // tp_itemsize
   (destructor)cdescriptor_pool::Dealloc,  // tp_dealloc
   0,                                   // tp_print
@@ -259,29 +422,11 @@ PyTypeObject CDescriptorPool_Type = {
   0,                                   // tp_descr_set
   0,                                   // tp_dictoffset
   0,                                   // tp_init
-  PyType_GenericAlloc,                 // tp_alloc
-  PyType_GenericNew,                   // tp_new
+  0,                                   // tp_alloc
+  0,                                   // tp_new
   PyObject_Del,                        // tp_free
 };
 
-google::protobuf::DescriptorPool* GetDescriptorPool() {
-  if (g_descriptor_pool == NULL) {
-    g_descriptor_pool = new google::protobuf::DescriptorPool(
-        google::protobuf::DescriptorPool::generated_pool());
-  }
-  return g_descriptor_pool;
-}
-
-PyObject* Python_NewCDescriptorPool(PyObject* ignored, PyObject* args) {
-  CDescriptorPool* cdescriptor_pool = PyObject_New(
-      CDescriptorPool, &CDescriptorPool_Type);
-  if (cdescriptor_pool == NULL) {
-    return NULL;
-  }
-  cdescriptor_pool->pool = GetDescriptorPool();
-  return reinterpret_cast<PyObject*>(cdescriptor_pool);
-}
-
 
 // Collects errors that occur during proto file building to allow them to be
 // propagated in the python exception instead of only living in ERROR logs.
@@ -321,6 +466,8 @@ PyObject* Python_BuildFile(PyObject* ignored, PyObject* arg) {
     return NULL;
   }
 
+  // If the file was already part of a C++ library, all its descriptors are in
+  // the underlying pool.  No need to do anything else.
   if (google::protobuf::DescriptorPool::generated_pool()->FindFileByName(
           file_proto.name()) != NULL) {
     Py_RETURN_NONE;
@@ -328,8 +475,8 @@ PyObject* Python_BuildFile(PyObject* ignored, PyObject* arg) {
 
   BuildFileErrorCollector error_collector;
   const google::protobuf::FileDescriptor* descriptor =
-      GetDescriptorPool()->BuildFileCollectingErrors(file_proto,
-                                                     &error_collector);
+      GetDescriptorPool()->pool->BuildFileCollectingErrors(file_proto,
+                                                           &error_collector);
   if (descriptor == NULL) {
     PyErr_Format(PyExc_TypeError,
                  "Couldn't build proto file into descriptor pool!\n%s",
@@ -341,12 +488,13 @@ PyObject* Python_BuildFile(PyObject* ignored, PyObject* arg) {
 }
 
 bool InitDescriptor() {
-  CFieldDescriptor_Type.tp_new = PyType_GenericNew;
+  if (PyType_Ready(&CMessageDescriptor_Type) < 0)
+    return false;
   if (PyType_Ready(&CFieldDescriptor_Type) < 0)
     return false;
 
-  CDescriptorPool_Type.tp_new = PyType_GenericNew;
-  if (PyType_Ready(&CDescriptorPool_Type) < 0)
+  PyDescriptorPool_Type.tp_new = PyType_GenericNew;
+  if (PyType_Ready(&PyDescriptorPool_Type) < 0)
     return false;
 
   return true;
diff --git a/python/google/protobuf/pyext/descriptor.h b/python/google/protobuf/pyext/descriptor.h
index ae7a1b9c..9e5957b5 100644
--- a/python/google/protobuf/pyext/descriptor.h
+++ b/python/google/protobuf/pyext/descriptor.h
@@ -36,6 +36,8 @@
 #include <Python.h>
 #include <structmember.h>
 
+#include <google/protobuf/stubs/hash.h>
+
 #include <google/protobuf/descriptor.h>
 
 #if PY_VERSION_HEX < 0x02050000 && !defined(PY_SSIZE_T_MIN)
@@ -48,46 +50,90 @@ namespace google {
 namespace protobuf {
 namespace python {
 
+typedef struct CMessageDescriptor {
+  PyObject_HEAD
+
+  // The proto2 descriptor that this object represents.
+  const google::protobuf::Descriptor* descriptor;
+} CMessageDescriptor;
+
+
 typedef struct CFieldDescriptor {
   PyObject_HEAD
 
   // The proto2 descriptor that this object represents.
   const google::protobuf::FieldDescriptor* descriptor;
-
-  // Reference to the original field object in the Python DESCRIPTOR.
-  PyObject* descriptor_field;
 } CFieldDescriptor;
 
-typedef struct {
+
+// Wraps operations to the global DescriptorPool which contains information
+// about all messages and fields.
+//
+// There is normally one pool per process. We make it a Python object only
+// because it contains many Python references.
+// TODO(amauryfa): See whether such objects can appear in reference cycles, and
+// consider adding support for the cyclic GC.
+//
+// "Methods" that interacts with this DescriptorPool are in the cdescriptor_pool
+// namespace.
+typedef struct PyDescriptorPool {
   PyObject_HEAD
 
-  const google::protobuf::DescriptorPool* pool;
-} CDescriptorPool;
+  google::protobuf::DescriptorPool* pool;
 
+  // Make our own mapping to retrieve Python classes from C++ descriptors.
+  //
+  // Descriptor pointers stored here are owned by the DescriptorPool above.
+  // Python references to classes are owned by this PyDescriptorPool.
+  typedef hash_map<const Descriptor *, PyObject *> ClassesByMessageMap;
+  ClassesByMessageMap *classes_by_descriptor;
+} PyDescriptorPool;
+
+
+extern PyTypeObject CMessageDescriptor_Type;
 extern PyTypeObject CFieldDescriptor_Type;
 
-extern PyTypeObject CDescriptorPool_Type;
+extern PyTypeObject PyDescriptorPool_Type;
+
 
 namespace cdescriptor_pool {
 
+// Builds a new DescriptorPool. Normally called only once per process.
+PyDescriptorPool* NewDescriptorPool();
+
+// Looks up a message by name.
+// Returns a message Descriptor, or NULL if not found.
+const google::protobuf::Descriptor* FindMessageTypeByName(PyDescriptorPool* self,
+                                                const string& name);
+
+// Registers a new Python class for the given message descriptor.
+// Returns the message Descriptor.
+// On error, returns NULL with a Python exception set.
+const google::protobuf::Descriptor* RegisterMessageClass(
+    PyDescriptorPool* self, PyObject *message_class, PyObject *descriptor);
+
+// Retrieves the Python class registered with the given message descriptor.
+//
+// Returns a *borrowed* reference if found, otherwise returns NULL with an
+// exception set.
+PyObject *GetMessageClass(PyDescriptorPool* self,
+                          const Descriptor *message_descriptor);
+
 // Looks up a field by name. Returns a CDescriptor corresponding to
 // the field on success, or NULL on failure.
 //
 // Returns a new reference.
-PyObject* FindFieldByName(CDescriptorPool* self, PyObject* name);
+PyObject* FindFieldByName(PyDescriptorPool* self, PyObject* name);
 
 // Looks up an extension by name. Returns a CDescriptor corresponding
 // to the field on success, or NULL on failure.
 //
 // Returns a new reference.
-PyObject* FindExtensionByName(CDescriptorPool* self, PyObject* arg);
-
+PyObject* FindExtensionByName(PyDescriptorPool* self, PyObject* arg);
 }  // namespace cdescriptor_pool
 
-PyObject* Python_NewCDescriptorPool(PyObject* ignored, PyObject* args);
 PyObject* Python_BuildFile(PyObject* ignored, PyObject* args);
 bool InitDescriptor();
-google::protobuf::DescriptorPool* GetDescriptorPool();
 
 }  // namespace python
 }  // namespace protobuf
diff --git a/python/google/protobuf/pyext/extension_dict.cc b/python/google/protobuf/pyext/extension_dict.cc
index 3861c794..d83b57d5 100644
--- a/python/google/protobuf/pyext/extension_dict.cc
+++ b/python/google/protobuf/pyext/extension_dict.cc
@@ -62,22 +62,6 @@ static google::protobuf::Message* GetMessage(ExtensionDict* self) {
   }
 }
 
-CFieldDescriptor* InternalGetCDescriptorFromExtension(PyObject* extension) {
-  PyObject* cdescriptor = PyObject_GetAttrString(extension, "_cdescriptor");
-  if (cdescriptor == NULL) {
-    PyErr_SetString(PyExc_KeyError, "Unregistered extension.");
-    return NULL;
-  }
-  if (!PyObject_TypeCheck(cdescriptor, &CFieldDescriptor_Type)) {
-    PyErr_SetString(PyExc_TypeError, "Not a CFieldDescriptor");
-    Py_DECREF(cdescriptor);
-    return NULL;
-  }
-  CFieldDescriptor* descriptor =
-      reinterpret_cast<CFieldDescriptor*>(cdescriptor);
-  return descriptor;
-}
-
 PyObject* len(ExtensionDict* self) {
 #if PY_MAJOR_VERSION >= 3
   return PyLong_FromLong(PyDict_Size(self->values));
@@ -118,16 +102,15 @@ int ReleaseExtension(ExtensionDict* self,
 }
 
 PyObject* subscript(ExtensionDict* self, PyObject* key) {
-  CFieldDescriptor* cdescriptor = InternalGetCDescriptorFromExtension(
-      key);
-  if (cdescriptor == NULL) {
+  const google::protobuf::FieldDescriptor* descriptor =
+      cmessage::GetExtensionDescriptor(key);
+  if (descriptor == NULL) {
     return NULL;
   }
-  ScopedPyObjectPtr py_cdescriptor(reinterpret_cast<PyObject*>(cdescriptor));
-  const google::protobuf::FieldDescriptor* descriptor = cdescriptor->descriptor;
-  if (descriptor == NULL) {
+  if (!CheckFieldBelongsToMessage(descriptor, self->parent->message)) {
     return NULL;
   }
+
   if (descriptor->label() != FieldDescriptor::LABEL_REPEATED &&
       descriptor->cpp_type() != FieldDescriptor::CPPTYPE_MESSAGE) {
     return cmessage::InternalGetScalar(self->parent, descriptor);
@@ -142,7 +125,7 @@ PyObject* subscript(ExtensionDict* self, PyObject* key) {
   if (descriptor->label() != FieldDescriptor::LABEL_REPEATED &&
       descriptor->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
     PyObject* sub_message = cmessage::InternalGetSubMessage(
-        self->parent, cdescriptor);
+        self->parent, descriptor);
     if (sub_message == NULL) {
       return NULL;
     }
@@ -152,33 +135,21 @@ PyObject* subscript(ExtensionDict* self, PyObject* key) {
 
   if (descriptor->label() == FieldDescriptor::LABEL_REPEATED) {
     if (descriptor->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
-      // COPIED
-      PyObject* py_container = PyObject_CallObject(
-          reinterpret_cast<PyObject*>(&RepeatedCompositeContainer_Type),
-          NULL);
+      PyObject *message_class = cdescriptor_pool::GetMessageClass(
+          GetDescriptorPool(), descriptor->message_type());
+      if (message_class == NULL) {
+        return NULL;
+      }
+      PyObject* py_container = repeated_composite_container::NewContainer(
+          self->parent, descriptor, message_class);
       if (py_container == NULL) {
         return NULL;
       }
-      RepeatedCompositeContainer* container =
-          reinterpret_cast<RepeatedCompositeContainer*>(py_container);
-      PyObject* field = cdescriptor->descriptor_field;
-      PyObject* message_type = PyObject_GetAttrString(field, "message_type");
-      PyObject* concrete_class = PyObject_GetAttrString(message_type,
-                                                        "_concrete_class");
-      container->owner = self->owner;
-      container->parent = self->parent;
-      container->message = self->parent->message;
-      container->parent_field = cdescriptor;
-      container->subclass_init = concrete_class;
-      Py_DECREF(message_type);
       PyDict_SetItem(self->values, key, py_container);
       return py_container;
     } else {
-      // COPIED
-      ScopedPyObjectPtr init_args(PyTuple_Pack(2, self->parent, cdescriptor));
-      PyObject* py_container = PyObject_CallObject(
-          reinterpret_cast<PyObject*>(&RepeatedScalarContainer_Type),
-          init_args);
+      PyObject* py_container = repeated_scalar_container::NewContainer(
+          self->parent, descriptor);
       if (py_container == NULL) {
         return NULL;
       }
@@ -191,13 +162,15 @@ PyObject* subscript(ExtensionDict* self, PyObject* key) {
 }
 
 int ass_subscript(ExtensionDict* self, PyObject* key, PyObject* value) {
-  CFieldDescriptor* cdescriptor = InternalGetCDescriptorFromExtension(
-      key);
-  if (cdescriptor == NULL) {
+  const google::protobuf::FieldDescriptor* descriptor =
+      cmessage::GetExtensionDescriptor(key);
+  if (descriptor == NULL) {
+    return -1;
+  }
+  if (!CheckFieldBelongsToMessage(descriptor, self->parent->message)) {
     return -1;
   }
-  ScopedPyObjectPtr py_cdescriptor(reinterpret_cast<PyObject*>(cdescriptor));
-  const google::protobuf::FieldDescriptor* descriptor = cdescriptor->descriptor;
+
   if (descriptor->label() != FieldDescriptor::LABEL_OPTIONAL ||
       descriptor->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
     PyErr_SetString(PyExc_TypeError, "Extension is repeated and/or composite "
@@ -214,20 +187,18 @@ int ass_subscript(ExtensionDict* self, PyObject* key, PyObject* value) {
 }
 
 PyObject* ClearExtension(ExtensionDict* self, PyObject* extension) {
-  CFieldDescriptor* cdescriptor = InternalGetCDescriptorFromExtension(
-      extension);
-  if (cdescriptor == NULL) {
+  const google::protobuf::FieldDescriptor* descriptor =
+      cmessage::GetExtensionDescriptor(extension);
+  if (descriptor == NULL) {
     return NULL;
   }
-  ScopedPyObjectPtr py_cdescriptor(reinterpret_cast<PyObject*>(cdescriptor));
   PyObject* value = PyDict_GetItem(self->values, extension);
   if (value != NULL) {
-    if (ReleaseExtension(self, value, cdescriptor->descriptor) < 0) {
+    if (ReleaseExtension(self, value, descriptor) < 0) {
       return NULL;
     }
   }
-  if (cmessage::ClearFieldByDescriptor(self->parent,
-                                       cdescriptor->descriptor) == NULL) {
+  if (cmessage::ClearFieldByDescriptor(self->parent, descriptor) == NULL) {
     return NULL;
   }
   if (PyDict_DelItem(self->values, extension) < 0) {
@@ -237,14 +208,12 @@ PyObject* ClearExtension(ExtensionDict* self, PyObject* extension) {
 }
 
 PyObject* HasExtension(ExtensionDict* self, PyObject* extension) {
-  CFieldDescriptor* cdescriptor = InternalGetCDescriptorFromExtension(
-      extension);
-  if (cdescriptor == NULL) {
+  const google::protobuf::FieldDescriptor* descriptor =
+      cmessage::GetExtensionDescriptor(extension);
+  if (descriptor == NULL) {
     return NULL;
   }
-  ScopedPyObjectPtr py_cdescriptor(reinterpret_cast<PyObject*>(cdescriptor));
-  PyObject* result = cmessage::HasFieldByDescriptor(
-      self->parent, cdescriptor->descriptor);
+  PyObject* result = cmessage::HasFieldByDescriptor(self->parent, descriptor);
   return result;
 }
 
@@ -263,11 +232,18 @@ PyObject* _FindExtensionByName(ExtensionDict* self, PyObject* name) {
   }
 }
 
-int init(ExtensionDict* self, PyObject* args, PyObject* kwargs) {
-  self->parent = NULL;
-  self->message = NULL;
+ExtensionDict* NewExtensionDict(CMessage *parent) {
+  ExtensionDict* self = reinterpret_cast<ExtensionDict*>(
+      PyType_GenericAlloc(&ExtensionDict_Type, 0));
+  if (self == NULL) {
+    return NULL;
+  }
+
+  self->parent = parent;  // Store a borrowed reference.
+  self->message = parent->message;
+  self->owner = parent->owner;
   self->values = PyDict_New();
-  return 0;
+  return self;
 }
 
 void dealloc(ExtensionDict* self) {
@@ -330,7 +306,7 @@ PyTypeObject ExtensionDict_Type = {
   0,                                   //  tp_descr_get
   0,                                   //  tp_descr_set
   0,                                   //  tp_dictoffset
-  (initproc)extension_dict::init,      //  tp_init
+  0,                                   //  tp_init
 };
 
 }  // namespace python
diff --git a/python/google/protobuf/pyext/extension_dict.h b/python/google/protobuf/pyext/extension_dict.h
index 13c874a4..47625e23 100644
--- a/python/google/protobuf/pyext/extension_dict.h
+++ b/python/google/protobuf/pyext/extension_dict.h
@@ -53,13 +53,26 @@ using internal::shared_ptr;
 namespace python {
 
 struct CMessage;
-struct CFieldDescriptor;
 
 typedef struct ExtensionDict {
   PyObject_HEAD;
+
+  // This is the top-level C++ Message object that owns the whole
+  // proto tree.  Every Python container class holds a
+  // reference to it in order to keep it alive as long as there's a
+  // Python object that references any part of the tree.
   shared_ptr<Message> owner;
+
+  // Weak reference to parent message. Used to make sure
+  // the parent is writable when an extension field is modified.
   CMessage* parent;
+
+  // Pointer to the C++ Message that this ExtensionDict extends.
+  // Not owned by us.
   Message* message;
+
+  // A dict of child messages, indexed by Extension descriptors.
+  // Similar to CMessage::composite_fields.
   PyObject* values;
 } ExtensionDict;
 
@@ -67,11 +80,8 @@ extern PyTypeObject ExtensionDict_Type;
 
 namespace extension_dict {
 
-// Gets the _cdescriptor reference to a CFieldDescriptor object given a
-// python descriptor object.
-//
-// Returns a new reference.
-CFieldDescriptor* InternalGetCDescriptorFromExtension(PyObject* extension);
+// Builds an Extensions dict for a specific message.
+ExtensionDict* NewExtensionDict(CMessage *parent);
 
 // Gets the number of extension values in this ExtensionDict as a python object.
 //
diff --git a/python/google/protobuf/pyext/message.cc b/python/google/protobuf/pyext/message.cc
index 9fb7083f..cd956e0e 100644
--- a/python/google/protobuf/pyext/message.cc
+++ b/python/google/protobuf/pyext/message.cc
@@ -71,7 +71,7 @@
     #error "Python 3.0 - 3.2 are not supported."
   #else
   #define PyString_AsString(ob) \
-    (PyUnicode_Check(ob)? PyUnicode_AsUTF8(ob): PyBytes_AS_STRING(ob))
+    (PyUnicode_Check(ob)? PyUnicode_AsUTF8(ob): PyBytes_AsString(ob))
   #endif
 #endif
 
@@ -81,7 +81,9 @@ namespace python {
 
 // Forward declarations
 namespace cmessage {
-static PyObject* GetDescriptor(CMessage* self, PyObject* name);
+static const google::protobuf::FieldDescriptor* GetFieldDescriptor(
+    CMessage* self, PyObject* name);
+static const google::protobuf::Descriptor* GetMessageDescriptor(PyTypeObject* cls);
 static string GetMessageName(CMessage* self);
 int InternalReleaseFieldByDescriptor(
     const google::protobuf::FieldDescriptor* field_descriptor,
@@ -147,12 +149,15 @@ int ForEachCompositeField(CMessage* self, Visitor visitor) {
   PyObject* key;
   PyObject* field;
 
+  // Never use self->message in this function, it may be already freed.
+  const google::protobuf::Descriptor* message_descriptor =
+      cmessage::GetMessageDescriptor(Py_TYPE(self));
+
   // Visit normal fields.
   while (PyDict_Next(self->composite_fields, &pos, &key, &field)) {
-    PyObject* cdescriptor = cmessage::GetDescriptor(self, key);
-    if (cdescriptor != NULL) {
-      const google::protobuf::FieldDescriptor* descriptor =
-          reinterpret_cast<CFieldDescriptor*>(cdescriptor)->descriptor;
+    const google::protobuf::FieldDescriptor* descriptor =
+      message_descriptor->FindFieldByName(PyString_AsString(key));
+    if (descriptor != NULL) {
       if (VisitCompositeField(descriptor, field, visitor) == -1)
         return -1;
     }
@@ -161,11 +166,11 @@ int ForEachCompositeField(CMessage* self, Visitor visitor) {
   // Visit extension fields.
   if (self->extensions != NULL) {
     while (PyDict_Next(self->extensions->values, &pos, &key, &field)) {
-      CFieldDescriptor* cdescriptor =
-          extension_dict::InternalGetCDescriptorFromExtension(key);
-      if (cdescriptor == NULL)
+      const google::protobuf::FieldDescriptor* descriptor =
+          cmessage::GetExtensionDescriptor(key);
+      if (descriptor == NULL)
         return -1;
-      if (VisitCompositeField(cdescriptor->descriptor, field, visitor) == -1)
+      if (VisitCompositeField(descriptor, field, visitor) == -1)
         return -1;
     }
   }
@@ -191,18 +196,19 @@ PyObject* PickleError_class;
 
 // Constant PyString values used for GetAttr/GetItem.
 static PyObject* kDESCRIPTOR;
-static PyObject* k__descriptors;
+static PyObject* k_cdescriptor;
 static PyObject* kfull_name;
 static PyObject* kname;
-static PyObject* kmessage_type;
-static PyObject* kis_extendable;
 static PyObject* kextensions_by_name;
 static PyObject* k_extensions_by_name;
 static PyObject* k_extensions_by_number;
-static PyObject* k_concrete_class;
 static PyObject* kfields_by_name;
 
-static CDescriptorPool* descriptor_pool;
+static PyDescriptorPool* descriptor_pool;
+
+PyDescriptorPool* GetDescriptorPool() {
+  return descriptor_pool;
+}
 
 /* Is 64bit */
 void FormatTypeError(PyObject* arg, char* expected_types) {
@@ -313,12 +319,12 @@ bool CheckAndSetString(
     }
 
     if (PyBytes_Check(arg)) {
-      PyObject* unicode = PyUnicode_FromEncodedObject(arg, "ascii", NULL);
+      PyObject* unicode = PyUnicode_FromEncodedObject(arg, "utf-8", NULL);
       if (unicode == NULL) {
         PyObject* repr = PyObject_Repr(arg);
         PyErr_Format(PyExc_ValueError,
-                     "%s has type str, but isn't in 7-bit ASCII "
-                     "encoding. Non-ASCII strings must be converted to "
+                     "%s has type str, but isn't valid UTF-8 "
+                     "encoding. Non-UTF-8 strings must be converted to "
                      "unicode objects before being added.",
                      PyString_AsString(repr));
         Py_DECREF(repr);
@@ -335,12 +341,9 @@ bool CheckAndSetString(
   PyObject* encoded_string = NULL;
   if (descriptor->type() == google::protobuf::FieldDescriptor::TYPE_STRING) {
     if (PyBytes_Check(arg)) {
-#if PY_MAJOR_VERSION < 3
-      encoded_string = PyString_AsEncodedObject(arg, "utf-8", NULL);
-#else
+      // The bytes were already validated as correctly encoded UTF-8 above.
       encoded_string = arg;  // Already encoded.
       Py_INCREF(encoded_string);
-#endif
     } else {
       encoded_string = PyUnicode_AsEncodedObject(arg, "utf-8", NULL);
     }
@@ -391,6 +394,17 @@ PyObject* ToStringObject(
   return result;
 }
 
+bool CheckFieldBelongsToMessage(const google::protobuf::FieldDescriptor* field_descriptor,
+                                const google::protobuf::Message* message) {
+  if (message->GetDescriptor() == field_descriptor->containing_type()) {
+    return true;
+  }
+  PyErr_Format(PyExc_KeyError, "Field '%s' does not belong to message '%s'",
+               field_descriptor->full_name().c_str(),
+               message->GetDescriptor()->full_name().c_str());
+  return false;
+}
+
 google::protobuf::DynamicMessageFactory* global_message_factory;
 
 namespace cmessage {
@@ -489,7 +503,7 @@ int AssureWritable(CMessage* self) {
     google::protobuf::Message* parent_message = self->parent->message;
     google::protobuf::Message* mutable_message = GetMutableMessage(
         self->parent,
-        self->parent_field->descriptor);
+        self->parent_field_descriptor);
     if (mutable_message == NULL) {
       return -1;
     }
@@ -512,26 +526,61 @@ int AssureWritable(CMessage* self) {
 
 // --- Globals:
 
-static PyObject* GetDescriptor(CMessage* self, PyObject* name) {
-  PyObject* descriptors =
-      PyDict_GetItem(Py_TYPE(self)->tp_dict, k__descriptors);
-  if (descriptors == NULL) {
-    PyErr_SetString(PyExc_TypeError, "No __descriptors");
+// Retrieve the C++ Descriptor of a message class.
+// On error, returns NULL with an exception set.
+static const google::protobuf::Descriptor* GetMessageDescriptor(PyTypeObject* cls) {
+  ScopedPyObjectPtr descriptor(PyObject_GetAttr(
+      reinterpret_cast<PyObject*>(cls), kDESCRIPTOR));
+  if (descriptor == NULL) {
+    PyErr_SetString(PyExc_TypeError, "Message class has no DESCRIPTOR");
+    return NULL;
+  }
+  ScopedPyObjectPtr cdescriptor(PyObject_GetAttr(descriptor, k_cdescriptor));
+  if (cdescriptor == NULL) {
+    PyErr_SetString(PyExc_TypeError, "Unregistered message.");
+    return NULL;
+  }
+  if (!PyObject_TypeCheck(cdescriptor, &CMessageDescriptor_Type)) {
+    PyErr_SetString(PyExc_TypeError, "Not a CMessageDescriptor");
     return NULL;
   }
+  return reinterpret_cast<CMessageDescriptor*>(cdescriptor.get())->descriptor;
+}
 
-  return PyDict_GetItem(descriptors, name);
+// Retrieve a C++ FieldDescriptor for a message attribute.
+// The C++ message must be valid.
+// TODO(amauryfa): This function should stay internal, because exception
+// handling is not consistent.
+static const google::protobuf::FieldDescriptor* GetFieldDescriptor(
+    CMessage* self, PyObject* name) {
+  const google::protobuf::Descriptor *message_descriptor = self->message->GetDescriptor();
+  const char* field_name = PyString_AsString(name);
+  if (field_name == NULL) {
+    return NULL;
+  }
+  const google::protobuf::FieldDescriptor *field_descriptor =
+      message_descriptor->FindFieldByName(field_name);
+  if (field_descriptor == NULL) {
+    // Note: No exception is set!
+    return NULL;
+  }
+  return field_descriptor;
 }
 
-static const google::protobuf::Message* CreateMessage(const char* message_type) {
-  string message_name(message_type);
-  const google::protobuf::Descriptor* descriptor =
-      GetDescriptorPool()->FindMessageTypeByName(message_name);
-  if (descriptor == NULL) {
-    PyErr_SetString(PyExc_TypeError, message_type);
+// Retrieve a C++ FieldDescriptor for an extension handle.
+const google::protobuf::FieldDescriptor* GetExtensionDescriptor(PyObject* extension) {
+  ScopedPyObjectPtr cdescriptor(
+      PyObject_GetAttrString(extension, "_cdescriptor"));
+  if (cdescriptor == NULL) {
+    PyErr_SetString(PyExc_KeyError, "Unregistered extension.");
+    return NULL;
+  }
+  if (!PyObject_TypeCheck(cdescriptor, &CFieldDescriptor_Type)) {
+    PyErr_SetString(PyExc_TypeError, "Not a CFieldDescriptor");
+    Py_DECREF(cdescriptor);
     return NULL;
   }
-  return global_message_factory->GetPrototype(descriptor);
+  return reinterpret_cast<CFieldDescriptor*>(cdescriptor.get())->descriptor;
 }
 
 // If cmessage_list is not NULL, this function releases values into the
@@ -627,39 +676,8 @@ int InternalDeleteRepeatedField(
   return 0;
 }
 
-int InitAttributes(CMessage* self, PyObject* arg, PyObject* kwargs) {
-  ScopedPyObjectPtr descriptor;
-  if (arg == NULL) {
-    descriptor.reset(
-        PyObject_GetAttr(reinterpret_cast<PyObject*>(self), kDESCRIPTOR));
-    if (descriptor == NULL) {
-      return NULL;
-    }
-  } else {
-    descriptor.reset(arg);
-    descriptor.inc();
-  }
-  ScopedPyObjectPtr is_extendable(PyObject_GetAttr(descriptor, kis_extendable));
-  if (is_extendable == NULL) {
-    return NULL;
-  }
-  int retcode = PyObject_IsTrue(is_extendable);
-  if (retcode == -1) {
-    return NULL;
-  }
-  if (retcode) {
-    PyObject* py_extension_dict = PyObject_CallObject(
-        reinterpret_cast<PyObject*>(&ExtensionDict_Type), NULL);
-    if (py_extension_dict == NULL) {
-      return NULL;
-    }
-    ExtensionDict* extension_dict = reinterpret_cast<ExtensionDict*>(
-        py_extension_dict);
-    extension_dict->parent = self;
-    extension_dict->message = self->message;
-    self->extensions = extension_dict;
-  }
-
+// Initializes fields of a message. Used in constructors.
+int InitAttributes(CMessage* self, PyObject* kwargs) {
   if (kwargs == NULL) {
     return 0;
   }
@@ -672,14 +690,12 @@ int InitAttributes(CMessage* self, PyObject* arg, PyObject* kwargs) {
       PyErr_SetString(PyExc_ValueError, "Field name must be a string");
       return -1;
     }
-    PyObject* py_cdescriptor = GetDescriptor(self, name);
-    if (py_cdescriptor == NULL) {
+    const google::protobuf::FieldDescriptor* descriptor = GetFieldDescriptor(self, name);
+    if (descriptor == NULL) {
       PyErr_Format(PyExc_ValueError, "Protocol message has no \"%s\" field.",
                    PyString_AsString(name));
       return -1;
     }
-    const google::protobuf::FieldDescriptor* descriptor =
-        reinterpret_cast<CFieldDescriptor*>(py_cdescriptor)->descriptor;
     if (descriptor->label() == google::protobuf::FieldDescriptor::LABEL_REPEATED) {
       ScopedPyObjectPtr container(GetAttr(self, name));
       if (container == NULL) {
@@ -719,15 +735,19 @@ int InitAttributes(CMessage* self, PyObject* arg, PyObject* kwargs) {
   return 0;
 }
 
-static PyObject* New(PyTypeObject* type, PyObject* args, PyObject* kwargs) {
-  CMessage* self = reinterpret_cast<CMessage*>(type->tp_alloc(type, 0));
+// Allocates an incomplete Python Message: the caller must fill self->message,
+// self->owner and eventually self->parent.
+CMessage* NewEmptyMessage(PyObject* type,
+                          const google::protobuf::Descriptor *descriptor) {
+  CMessage* self = reinterpret_cast<CMessage*>(
+      PyType_GenericAlloc(reinterpret_cast<PyTypeObject*>(type), 0));
   if (self == NULL) {
     return NULL;
   }
 
   self->message = NULL;
   self->parent = NULL;
-  self->parent_field = NULL;
+  self->parent_field_descriptor = NULL;
   self->read_only = false;
   self->extensions = NULL;
 
@@ -735,43 +755,58 @@ static PyObject* New(PyTypeObject* type, PyObject* args, PyObject* kwargs) {
   if (self->composite_fields == NULL) {
     return NULL;
   }
-  return reinterpret_cast<PyObject*>(self);
-}
-
-PyObject* NewEmpty(PyObject* type) {
-  return New(reinterpret_cast<PyTypeObject*>(type), NULL, NULL);
-}
 
-static int Init(CMessage* self, PyObject* args, PyObject* kwargs) {
-  if (kwargs == NULL) {
-    // TODO(anuraag): Set error
-    return -1;
+  // If there are extension_ranges, the message is "extendable". Allocate a
+  // dictionary to store the extension fields.
+  if (descriptor->extension_range_count() > 0) {
+    // TODO(amauryfa): Delay the construction of this dict until extensions are
+    // really used on the object.
+    ExtensionDict* extension_dict = extension_dict::NewExtensionDict(self);
+    if (extension_dict == NULL) {
+      return NULL;
+    }
+    self->extensions = extension_dict;
   }
 
-  PyObject* descriptor = PyTuple_GetItem(args, 0);
-  if (descriptor == NULL || PyTuple_Size(args) != 1) {
-    PyErr_SetString(PyExc_ValueError, "args must contain one arg: descriptor");
-    return -1;
-  }
+  return self;
+}
 
-  ScopedPyObjectPtr py_message_type(PyObject_GetAttr(descriptor, kfull_name));
-  if (py_message_type == NULL) {
-    return -1;
+// The __new__ method of Message classes.
+// Creates a new C++ message and takes ownership.
+static PyObject* New(PyTypeObject* type,
+                     PyObject* unused_args, PyObject* unused_kwargs) {
+  // Retrieve the message descriptor and the default instance (=prototype).
+  const google::protobuf::Descriptor* message_descriptor = GetMessageDescriptor(type);
+  if (message_descriptor == NULL) {
+    return NULL;
   }
-
-  const char* message_type = PyString_AsString(py_message_type.get());
-  const google::protobuf::Message* message = CreateMessage(message_type);
-  if (message == NULL) {
-    return -1;
+  const google::protobuf::Message* default_message =
+      global_message_factory->GetPrototype(message_descriptor);
+  if (default_message == NULL) {
+    PyErr_SetString(PyExc_TypeError, message_descriptor->full_name().c_str());
+    return NULL;
   }
 
-  self->message = message->New();
+  CMessage* self = NewEmptyMessage(reinterpret_cast<PyObject*>(type),
+                                   message_descriptor);
+  if (self == NULL) {
+    return NULL;
+  }
+  self->message = default_message->New();
   self->owner.reset(self->message);
 
-  if (InitAttributes(self, descriptor, kwargs) < 0) {
+  return reinterpret_cast<PyObject*>(self);
+}
+
+// The __init__ method of Message classes.
+// It initializes fields from keywords passed to the constructor.
+static int Init(CMessage* self, PyObject* args, PyObject* kwargs) {
+  if (PyTuple_Size(args) != 0) {
+    PyErr_SetString(PyExc_TypeError, "No positional arguments allowed");
     return -1;
   }
-  return 0;
+
+  return InitAttributes(self, kwargs);
 }
 
 // ---------------------------------------------------------------------
@@ -853,9 +888,7 @@ PyObject* IsInitialized(CMessage* self, PyObject* args) {
 PyObject* HasFieldByDescriptor(
     CMessage* self, const google::protobuf::FieldDescriptor* field_descriptor) {
   google::protobuf::Message* message = self->message;
-  if (!FIELD_BELONGS_TO_MESSAGE(field_descriptor, message)) {
-    PyErr_SetString(PyExc_KeyError,
-                    "Field does not belong to message!");
+  if (!CheckFieldBelongsToMessage(field_descriptor, message)) {
     return NULL;
   }
   if (field_descriptor->label() == google::protobuf::FieldDescriptor::LABEL_REPEATED) {
@@ -1048,7 +1081,7 @@ int ReleaseSubMessage(google::protobuf::Message* message,
   child_cmessage->message = released_message.get();
   child_cmessage->owner.swap(released_message);
   child_cmessage->parent = NULL;
-  child_cmessage->parent_field = NULL;
+  child_cmessage->parent_field_descriptor = NULL;
   child_cmessage->read_only = false;
   return ForEachCompositeField(child_cmessage,
                                SetOwnerVisitor(child_cmessage->owner));
@@ -1090,10 +1123,8 @@ int InternalReleaseFieldByDescriptor(
 
 int InternalReleaseField(CMessage* self, PyObject* composite_field,
                          PyObject* name) {
-  PyObject* cdescriptor = GetDescriptor(self, name);
-  if (cdescriptor != NULL) {
-    const google::protobuf::FieldDescriptor* descriptor =
-        reinterpret_cast<CFieldDescriptor*>(cdescriptor)->descriptor;
+  const google::protobuf::FieldDescriptor* descriptor = GetFieldDescriptor(self, name);
+  if (descriptor != NULL) {
     return InternalReleaseFieldByDescriptor(
         descriptor, composite_field, self->message);
   }
@@ -1104,9 +1135,7 @@ int InternalReleaseField(CMessage* self, PyObject* composite_field,
 PyObject* ClearFieldByDescriptor(
     CMessage* self,
     const google::protobuf::FieldDescriptor* descriptor) {
-  if (!FIELD_BELONGS_TO_MESSAGE(descriptor, self->message)) {
-    PyErr_SetString(PyExc_KeyError,
-                    "Field does not belong to message!");
+  if (!CheckFieldBelongsToMessage(descriptor, self->message)) {
     return NULL;
   }
   AssureWritable(self);
@@ -1177,15 +1206,10 @@ PyObject* Clear(CMessage* self) {
   // fields have been released.
   if (self->extensions != NULL) {
     Py_CLEAR(self->extensions);
-    PyObject* py_extension_dict = PyObject_CallObject(
-        reinterpret_cast<PyObject*>(&ExtensionDict_Type), NULL);
-    if (py_extension_dict == NULL) {
+    ExtensionDict* extension_dict = extension_dict::NewExtensionDict(self);
+    if (extension_dict == NULL) {
       return NULL;
     }
-    ExtensionDict* extension_dict = reinterpret_cast<ExtensionDict*>(
-        py_extension_dict);
-    extension_dict->parent = self;
-    extension_dict->message = self->message;
     self->extensions = extension_dict;
   }
   PyDict_Clear(self->composite_fields);
@@ -1196,8 +1220,8 @@ PyObject* Clear(CMessage* self) {
 // ---------------------------------------------------------------------
 
 static string GetMessageName(CMessage* self) {
-  if (self->parent_field != NULL) {
-    return self->parent_field->descriptor->full_name();
+  if (self->parent_field_descriptor != NULL) {
+    return self->parent_field_descriptor->full_name();
   } else {
     return self->message->GetDescriptor()->full_name();
   }
@@ -1219,7 +1243,7 @@ static PyObject* SerializeToString(CMessage* self, PyObject* args) {
       return NULL;
     }
     PyErr_Format(EncodeError_class, "Message %s is missing required fields: %s",
-                 GetMessageName(self).c_str(), PyString_AsString(joined.get()));
+                 GetMessageName(self).c_str(), PyString_AsString(joined));
     return NULL;
   }
   int size = self->message->ByteSize();
@@ -1361,7 +1385,7 @@ static PyObject* MergeFromString(CMessage* self, PyObject* arg) {
   AssureWritable(self);
   google::protobuf::io::CodedInputStream input(
       reinterpret_cast<const uint8*>(data), data_length);
-  input.SetExtensionRegistry(GetDescriptorPool(), global_message_factory);
+  input.SetExtensionRegistry(descriptor_pool->pool, global_message_factory);
   bool success = self->message->MergePartialFromCodedStream(&input);
   if (success) {
     return PyInt_FromLong(input.CurrentPosition());
@@ -1421,15 +1445,11 @@ static PyObject* RegisterExtension(PyObject* cls,
     return NULL;
   }
 
-  CFieldDescriptor* cdescriptor =
-      extension_dict::InternalGetCDescriptorFromExtension(extension_handle);
-  ScopedPyObjectPtr py_cdescriptor(reinterpret_cast<PyObject*>(cdescriptor));
-  if (cdescriptor == NULL) {
+  const google::protobuf::FieldDescriptor* descriptor =
+      GetExtensionDescriptor(extension_handle);
+  if (descriptor == NULL) {
     return NULL;
   }
-  Py_INCREF(extension_handle);
-  cdescriptor->descriptor_field = extension_handle;
-  const google::protobuf::FieldDescriptor* descriptor = cdescriptor->descriptor;
   // Check if it's a message set
   if (descriptor->is_extension() &&
       descriptor->containing_type()->options().message_set_wire_format() &&
@@ -1608,8 +1628,14 @@ static PyObject* RichCompare(CMessage* self, PyObject* other, int opid) {
   }
   if (opid == Py_EQ || opid == Py_NE) {
     ScopedPyObjectPtr self_fields(ListFields(self));
+    if (!self_fields) {
+      return NULL;
+    }
     ScopedPyObjectPtr other_fields(ListFields(
         reinterpret_cast<CMessage*>(other)));
+    if (!other_fields) {
+      return NULL;
+    }
     return PyObject_RichCompare(self_fields, other_fields, opid);
   } else {
     Py_INCREF(Py_NotImplemented);
@@ -1623,9 +1649,7 @@ PyObject* InternalGetScalar(
   google::protobuf::Message* message = self->message;
   const google::protobuf::Reflection* reflection = message->GetReflection();
 
-  if (!FIELD_BELONGS_TO_MESSAGE(field_descriptor, message)) {
-    PyErr_SetString(
-        PyExc_KeyError, "Field does not belong to message!");
+  if (!CheckFieldBelongsToMessage(field_descriptor, message)) {
     return NULL;
   }
 
@@ -1701,43 +1725,31 @@ PyObject* InternalGetScalar(
   return result;
 }
 
-PyObject* InternalGetSubMessage(CMessage* self,
-                                CFieldDescriptor* cfield_descriptor) {
-  PyObject* field = cfield_descriptor->descriptor_field;
-  ScopedPyObjectPtr message_type(PyObject_GetAttr(field, kmessage_type));
-  if (message_type == NULL) {
-    return NULL;
-  }
-  ScopedPyObjectPtr concrete_class(
-      PyObject_GetAttr(message_type, k_concrete_class));
-  if (concrete_class == NULL) {
+PyObject* InternalGetSubMessage(
+    CMessage* self, const google::protobuf::FieldDescriptor* field_descriptor) {
+  const google::protobuf::Reflection* reflection = self->message->GetReflection();
+  const google::protobuf::Message& sub_message = reflection->GetMessage(
+      *self->message, field_descriptor, global_message_factory);
+
+  PyObject *message_class = cdescriptor_pool::GetMessageClass(
+      descriptor_pool, field_descriptor->message_type());
+  if (message_class == NULL) {
     return NULL;
   }
-  PyObject* py_cmsg = cmessage::NewEmpty(concrete_class);
-  if (py_cmsg == NULL) {
+
+  CMessage* cmsg = cmessage::NewEmptyMessage(message_class,
+                                             sub_message.GetDescriptor());
+  if (cmsg == NULL) {
     return NULL;
   }
-  if (!PyObject_TypeCheck(py_cmsg, &CMessage_Type)) {
-    PyErr_SetString(PyExc_TypeError, "Not a CMessage!");
-  }
-  CMessage* cmsg = reinterpret_cast<CMessage*>(py_cmsg);
 
-  const google::protobuf::FieldDescriptor* field_descriptor =
-      cfield_descriptor->descriptor;
-  const google::protobuf::Reflection* reflection = self->message->GetReflection();
-  const google::protobuf::Message& sub_message = reflection->GetMessage(
-      *self->message, field_descriptor, global_message_factory);
   cmsg->owner = self->owner;
   cmsg->parent = self;
-  cmsg->parent_field = cfield_descriptor;
+  cmsg->parent_field_descriptor = field_descriptor;
   cmsg->read_only = !reflection->HasField(*self->message, field_descriptor);
   cmsg->message = const_cast<google::protobuf::Message*>(&sub_message);
 
-  if (InitAttributes(cmsg, NULL, NULL) < 0) {
-    Py_DECREF(py_cmsg);
-    return NULL;
-  }
-  return py_cmsg;
+  return reinterpret_cast<PyObject*>(cmsg);
 }
 
 int InternalSetScalar(
@@ -1747,9 +1759,7 @@ int InternalSetScalar(
   google::protobuf::Message* message = self->message;
   const google::protobuf::Reflection* reflection = message->GetReflection();
 
-  if (!FIELD_BELONGS_TO_MESSAGE(field_descriptor, message)) {
-    PyErr_SetString(
-        PyExc_KeyError, "Field does not belong to message!");
+  if (!CheckFieldBelongsToMessage(field_descriptor, message)) {
     return -1;
   }
 
@@ -1838,25 +1848,35 @@ PyObject* FromString(PyTypeObject* cls, PyObject* serialized) {
     return NULL;
   }
 
-  if (InitAttributes(cmsg, NULL, NULL) < 0) {
-    Py_DECREF(py_cmsg);
-    return NULL;
-  }
   return py_cmsg;
 }
 
+
+// Finalize the creation of the Message class.
+// Called from its metaclass: GeneratedProtocolMessageType.__init__().
 static PyObject* AddDescriptors(PyTypeObject* cls,
                                 PyObject* descriptor) {
-  if (PyObject_SetAttr(reinterpret_cast<PyObject*>(cls),
-                       k_extensions_by_name, PyDict_New()) < 0) {
-    return NULL;
-  }
-  if (PyObject_SetAttr(reinterpret_cast<PyObject*>(cls),
-                       k_extensions_by_number, PyDict_New()) < 0) {
+  const google::protobuf::Descriptor* message_descriptor =
+      cdescriptor_pool::RegisterMessageClass(
+          descriptor_pool, reinterpret_cast<PyObject*>(cls), descriptor);
+  if (message_descriptor == NULL) {
     return NULL;
   }
 
-  ScopedPyObjectPtr field_descriptors(PyDict_New());
+  // If there are extension_ranges, the message is "extendable", and extension
+  // classes will register themselves in this class.
+  if (message_descriptor->extension_range_count() > 0) {
+    ScopedPyObjectPtr by_name(PyDict_New());
+    if (PyObject_SetAttr(reinterpret_cast<PyObject*>(cls),
+                         k_extensions_by_name, by_name) < 0) {
+      return NULL;
+    }
+    ScopedPyObjectPtr by_number(PyDict_New());
+    if (PyObject_SetAttr(reinterpret_cast<PyObject*>(cls),
+                         k_extensions_by_number, by_number) < 0) {
+      return NULL;
+    }
+  }
 
   ScopedPyObjectPtr fields(PyObject_GetAttrString(descriptor, "fields"));
   if (fields == NULL) {
@@ -1878,19 +1898,14 @@ static PyObject* AddDescriptors(PyTypeObject* cls,
       return NULL;
     }
 
-    PyObject* field_descriptor =
-        cdescriptor_pool::FindFieldByName(descriptor_pool, full_field_name);
+    ScopedPyObjectPtr field_descriptor(
+        cdescriptor_pool::FindFieldByName(descriptor_pool, full_field_name));
     if (field_descriptor == NULL) {
       PyErr_SetString(PyExc_TypeError, "Couldn't find field");
       return NULL;
     }
-    Py_INCREF(field);
     CFieldDescriptor* cfield_descriptor = reinterpret_cast<CFieldDescriptor*>(
-        field_descriptor);
-    cfield_descriptor->descriptor_field = field;
-    if (PyDict_SetItem(field_descriptors, field_name, field_descriptor) < 0) {
-      return NULL;
-    }
+        field_descriptor.get());
 
     // The FieldDescriptor's name field might either be of type bytes or
     // of type unicode, depending on whether the FieldDescriptor was
@@ -1919,8 +1934,6 @@ static PyObject* AddDescriptors(PyTypeObject* cls,
     }
   }
 
-  PyDict_SetItem(cls->tp_dict, k__descriptors, field_descriptors);
-
   // Enum Values
   ScopedPyObjectPtr enum_types(PyObject_GetAttrString(descriptor,
                                                       "enum_types"));
@@ -1994,15 +2007,11 @@ static PyObject* AddDescriptors(PyTypeObject* cls,
                          extension_name, extension_field) == -1) {
       return NULL;
     }
-    ScopedPyObjectPtr py_cfield_descriptor(
-        PyObject_GetAttrString(extension_field, "_cdescriptor"));
-    if (py_cfield_descriptor == NULL) {
+    const google::protobuf::FieldDescriptor* field_descriptor =
+        GetExtensionDescriptor(extension_field);
+    if (field_descriptor == NULL) {
       return NULL;
     }
-    CFieldDescriptor* cfield_descriptor =
-        reinterpret_cast<CFieldDescriptor*>(py_cfield_descriptor.get());
-    Py_INCREF(extension_field);
-    cfield_descriptor->descriptor_field = extension_field;
 
     ScopedPyObjectPtr field_name_upcased(
         PyObject_CallMethod(extension_name, "upper", NULL));
@@ -2015,13 +2024,12 @@ static PyObject* AddDescriptors(PyTypeObject* cls,
       return NULL;
     }
     ScopedPyObjectPtr number(PyInt_FromLong(
-        cfield_descriptor->descriptor->number()));
+        field_descriptor->number()));
     if (number == NULL) {
       return NULL;
     }
     if (PyObject_SetAttr(reinterpret_cast<PyObject*>(cls),
-                         field_number_name, PyInt_FromLong(
-            cfield_descriptor->descriptor->number())) == -1) {
+                         field_number_name, number) == -1) {
       return NULL;
     }
   }
@@ -2039,10 +2047,6 @@ PyObject* DeepCopy(CMessage* self, PyObject* arg) {
     Py_DECREF(clone);
     return NULL;
   }
-  if (InitAttributes(reinterpret_cast<CMessage*>(clone), NULL, NULL) < 0) {
-    Py_DECREF(clone);
-    return NULL;
-  }
   if (MergeFrom(reinterpret_cast<CMessage*>(clone),
                 reinterpret_cast<PyObject*>(self)) == NULL) {
     Py_DECREF(clone);
@@ -2202,48 +2206,30 @@ PyObject* GetAttr(CMessage* self, PyObject* name) {
     return value;
   }
 
-  PyObject* descriptor = GetDescriptor(self, name);
-  if (descriptor != NULL) {
-    CFieldDescriptor* cdescriptor =
-        reinterpret_cast<CFieldDescriptor*>(descriptor);
-    const google::protobuf::FieldDescriptor* field_descriptor = cdescriptor->descriptor;
+  const google::protobuf::FieldDescriptor* field_descriptor = GetFieldDescriptor(
+      self, name);
+  if (field_descriptor != NULL) {
     if (field_descriptor->label() == google::protobuf::FieldDescriptor::LABEL_REPEATED) {
       if (field_descriptor->cpp_type() ==
           google::protobuf::FieldDescriptor::CPPTYPE_MESSAGE) {
-        PyObject* py_container = PyObject_CallObject(
-            reinterpret_cast<PyObject*>(&RepeatedCompositeContainer_Type),
-            NULL);
-        if (py_container == NULL) {
+        PyObject *message_class = cdescriptor_pool::GetMessageClass(
+            descriptor_pool, field_descriptor->message_type());
+        if (message_class == NULL) {
           return NULL;
         }
-        RepeatedCompositeContainer* container =
-            reinterpret_cast<RepeatedCompositeContainer*>(py_container);
-        PyObject* field = cdescriptor->descriptor_field;
-        PyObject* message_type = PyObject_GetAttr(field, kmessage_type);
-        if (message_type == NULL) {
-          return NULL;
-        }
-        PyObject* concrete_class =
-            PyObject_GetAttr(message_type, k_concrete_class);
-        if (concrete_class == NULL) {
+        PyObject* py_container = repeated_composite_container::NewContainer(
+            self, field_descriptor, message_class);
+        if (py_container == NULL) {
           return NULL;
         }
-        container->parent = self;
-        container->parent_field = cdescriptor;
-        container->message = self->message;
-        container->owner = self->owner;
-        container->subclass_init = concrete_class;
-        Py_DECREF(message_type);
         if (PyDict_SetItem(self->composite_fields, name, py_container) < 0) {
           Py_DECREF(py_container);
           return NULL;
         }
         return py_container;
       } else {
-        ScopedPyObjectPtr init_args(PyTuple_Pack(2, self, cdescriptor));
-        PyObject* py_container = PyObject_CallObject(
-            reinterpret_cast<PyObject*>(&RepeatedScalarContainer_Type),
-            init_args);
+        PyObject* py_container = repeated_scalar_container::NewContainer(
+            self, field_descriptor);
         if (py_container == NULL) {
           return NULL;
         }
@@ -2256,7 +2242,7 @@ PyObject* GetAttr(CMessage* self, PyObject* name) {
     } else {
       if (field_descriptor->cpp_type() ==
           google::protobuf::FieldDescriptor::CPPTYPE_MESSAGE) {
-        PyObject* sub_message = InternalGetSubMessage(self, cdescriptor);
+        PyObject* sub_message = InternalGetSubMessage(self, field_descriptor);
         if (PyDict_SetItem(self->composite_fields, name, sub_message) < 0) {
           Py_DECREF(sub_message);
           return NULL;
@@ -2278,12 +2264,10 @@ int SetAttr(CMessage* self, PyObject* name, PyObject* value) {
     return -1;
   }
 
-  PyObject* descriptor = GetDescriptor(self, name);
-  if (descriptor != NULL) {
+  const google::protobuf::FieldDescriptor* field_descriptor =
+      GetFieldDescriptor(self, name);
+  if (field_descriptor != NULL) {
     AssureWritable(self);
-    CFieldDescriptor* cdescriptor =
-        reinterpret_cast<CFieldDescriptor*>(descriptor);
-    const google::protobuf::FieldDescriptor* field_descriptor = cdescriptor->descriptor;
     if (field_descriptor->label() == google::protobuf::FieldDescriptor::LABEL_REPEATED) {
       PyErr_Format(PyExc_AttributeError, "Assignment not allowed to repeated "
                    "field \"%s\" in protocol message object.",
@@ -2401,22 +2385,18 @@ void InitGlobals() {
   kuint64max_py = PyLong_FromUnsignedLongLong(kuint64max);
 
   kDESCRIPTOR = PyString_FromString("DESCRIPTOR");
-  k__descriptors = PyString_FromString("__descriptors");
+  k_cdescriptor = PyString_FromString("_cdescriptor");
   kfull_name = PyString_FromString("full_name");
-  kis_extendable = PyString_FromString("is_extendable");
   kextensions_by_name = PyString_FromString("extensions_by_name");
   k_extensions_by_name = PyString_FromString("_extensions_by_name");
   k_extensions_by_number = PyString_FromString("_extensions_by_number");
-  k_concrete_class = PyString_FromString("_concrete_class");
-  kmessage_type = PyString_FromString("message_type");
   kname = PyString_FromString("name");
   kfields_by_name = PyString_FromString("fields_by_name");
 
-  global_message_factory = new DynamicMessageFactory(GetDescriptorPool());
-  global_message_factory->SetDelegateToGeneratedFactory(true);
+  descriptor_pool = cdescriptor_pool::NewDescriptorPool();
 
-  descriptor_pool = reinterpret_cast<google::protobuf::python::CDescriptorPool*>(
-      Python_NewCDescriptorPool(NULL, NULL));
+  global_message_factory = new DynamicMessageFactory(descriptor_pool->pool);
+  global_message_factory->SetDelegateToGeneratedFactory(true);
 }
 
 bool InitProto2MessageModule(PyObject *m) {
@@ -2427,19 +2407,32 @@ bool InitProto2MessageModule(PyObject *m) {
     return false;
   }
 
-  // All three of these are actually set elsewhere, directly onto the child
-  // protocol buffer message class, but set them here as well to document that
-  // subclasses need to set these.
+  // DESCRIPTOR is set on each protocol buffer message class elsewhere, but set
+  // it here as well to document that subclasses need to set it.
   PyDict_SetItem(google::protobuf::python::CMessage_Type.tp_dict, kDESCRIPTOR, Py_None);
-  PyDict_SetItem(google::protobuf::python::CMessage_Type.tp_dict,
-                 k_extensions_by_name, Py_None);
-  PyDict_SetItem(google::protobuf::python::CMessage_Type.tp_dict,
-                 k_extensions_by_number, Py_None);
+  // Subclasses with message extensions will override _extensions_by_name and
+  // _extensions_by_number with fresh mutable dictionaries in AddDescriptors.
+  // All other classes can share this same immutable mapping.
+  ScopedPyObjectPtr empty_dict(PyDict_New());
+  if (empty_dict == NULL) {
+    return false;
+  }
+  ScopedPyObjectPtr immutable_dict(PyDictProxy_New(empty_dict));
+  if (immutable_dict == NULL) {
+    return false;
+  }
+  if (PyDict_SetItem(google::protobuf::python::CMessage_Type.tp_dict,
+                     k_extensions_by_name, immutable_dict) < 0) {
+    return false;
+  }
+  if (PyDict_SetItem(google::protobuf::python::CMessage_Type.tp_dict,
+                     k_extensions_by_number, immutable_dict) < 0) {
+    return false;
+  }
 
   PyModule_AddObject(m, "Message", reinterpret_cast<PyObject*>(
       &google::protobuf::python::CMessage_Type));
 
-  google::protobuf::python::RepeatedScalarContainer_Type.tp_new = PyType_GenericNew;
   google::protobuf::python::RepeatedScalarContainer_Type.tp_hash =
       PyObject_HashNotImplemented;
   if (PyType_Ready(&google::protobuf::python::RepeatedScalarContainer_Type) < 0) {
@@ -2450,7 +2443,6 @@ bool InitProto2MessageModule(PyObject *m) {
                      reinterpret_cast<PyObject*>(
                          &google::protobuf::python::RepeatedScalarContainer_Type));
 
-  google::protobuf::python::RepeatedCompositeContainer_Type.tp_new = PyType_GenericNew;
   google::protobuf::python::RepeatedCompositeContainer_Type.tp_hash =
       PyObject_HashNotImplemented;
   if (PyType_Ready(&google::protobuf::python::RepeatedCompositeContainer_Type) < 0) {
@@ -2462,7 +2454,6 @@ bool InitProto2MessageModule(PyObject *m) {
       reinterpret_cast<PyObject*>(
           &google::protobuf::python::RepeatedCompositeContainer_Type));
 
-  google::protobuf::python::ExtensionDict_Type.tp_new = PyType_GenericNew;
   google::protobuf::python::ExtensionDict_Type.tp_hash = PyObject_HashNotImplemented;
   if (PyType_Ready(&google::protobuf::python::ExtensionDict_Type) < 0) {
     return false;
diff --git a/python/google/protobuf/pyext/message.h b/python/google/protobuf/pyext/message.h
index 9f4978f4..73e5a7d3 100644
--- a/python/google/protobuf/pyext/message.h
+++ b/python/google/protobuf/pyext/message.h
@@ -49,12 +49,13 @@ namespace protobuf {
 class Message;
 class Reflection;
 class FieldDescriptor;
+class Descriptor;
 
 using internal::shared_ptr;
 
 namespace python {
 
-struct CFieldDescriptor;
+struct PyDescriptorPool;
 struct ExtensionDict;
 
 typedef struct CMessage {
@@ -79,13 +80,11 @@ typedef struct CMessage {
   // to use this pointer will result in a crash.
   struct CMessage* parent;
 
-  // Weak reference to the parent's descriptor that describes this submessage.
+  // Pointer to the parent's descriptor that describes this submessage.
   // Used together with the parent's message when making a default message
   // instance mutable.
-  // TODO(anuraag): With a bit of work on the Python/C++ layer, it should be
-  // possible to make this a direct pointer to a C++ FieldDescriptor, this would
-  // be easier if this implementation replaces upstream.
-  CFieldDescriptor* parent_field;
+  // The pointer is owned by the global DescriptorPool.
+  const google::protobuf::FieldDescriptor* parent_field_descriptor;
 
   // Pointer to the C++ Message object for this CMessage.  The
   // CMessage does not own this pointer.
@@ -113,8 +112,11 @@ extern PyTypeObject CMessage_Type;
 
 namespace cmessage {
 
-// Create a new empty message that can be populated by the parent.
-PyObject* NewEmpty(PyObject* type);
+// Internal function to create a new empty Message Python object, but with empty
+// pointers to the C++ objects.
+// The caller must fill self->message, self->owner and eventually self->parent.
+CMessage* NewEmptyMessage(PyObject* type,
+                          const google::protobuf::Descriptor* descriptor);
 
 // Release a submessage from its proto tree, making it a new top-level messgae.
 // A new message will be created if this is a read-only default instance.
@@ -124,12 +126,16 @@ int ReleaseSubMessage(google::protobuf::Message* message,
                       const google::protobuf::FieldDescriptor* field_descriptor,
                       CMessage* child_cmessage);
 
+// Retrieves the C++ descriptor of a Python Extension descriptor.
+// On error, return NULL with an exception set.
+const google::protobuf::FieldDescriptor* GetExtensionDescriptor(PyObject* extension);
+
 // Initializes a new CMessage instance for a submessage. Only called once per
 // submessage as the result is cached in composite_fields.
 //
 // Corresponds to reflection api method GetMessage.
-PyObject* InternalGetSubMessage(CMessage* self,
-                                CFieldDescriptor* cfield_descriptor);
+PyObject* InternalGetSubMessage(
+    CMessage* self, const google::protobuf::FieldDescriptor* field_descriptor);
 
 // Deletes a range of C++ submessages in a repeated field (following a
 // removal in a RepeatedCompositeContainer).
@@ -190,10 +196,8 @@ PyObject* HasFieldByDescriptor(
 // Corresponds to reflection api method HasField.
 PyObject* HasField(CMessage* self, PyObject* arg);
 
-// Initializes constants/enum values on a message. This is called by
-// RepeatedCompositeContainer and ExtensionDict after calling the constructor.
-// TODO(anuraag): Make it always called from within the constructor since it can
-int InitAttributes(CMessage* self, PyObject* descriptor, PyObject* kwargs);
+// Initializes values of fields on a newly constructed message.
+int InitAttributes(CMessage* self, PyObject* kwargs);
 
 PyObject* MergeFrom(CMessage* self, PyObject* arg);
 
@@ -218,12 +222,14 @@ int AssureWritable(CMessage* self);
 
 }  // namespace cmessage
 
+
+// Retrieve the global descriptor pool owned by the _message module.
+PyDescriptorPool* GetDescriptorPool();
+
+
 /* Is 64bit */
 #define IS_64BIT (SIZEOF_LONG == 8)
 
-#define FIELD_BELONGS_TO_MESSAGE(field_descriptor, message) \
-    ((message)->GetDescriptor() == (field_descriptor)->containing_type())
-
 #define FIELD_IS_REPEATED(field_descriptor)                 \
     ((field_descriptor)->label() == google::protobuf::FieldDescriptor::LABEL_REPEATED)
 
@@ -296,6 +302,11 @@ bool CheckAndSetString(
 PyObject* ToStringObject(
     const google::protobuf::FieldDescriptor* descriptor, string value);
 
+// Check if the passed field descriptor belongs to the given message.
+// If not, return false and set a Python exception (a KeyError)
+bool CheckFieldBelongsToMessage(const google::protobuf::FieldDescriptor* field_descriptor,
+                                const google::protobuf::Message* message);
+
 extern PyObject* PickleError_class;
 
 }  // namespace python
diff --git a/python/google/protobuf/pyext/proto2_api_test.proto b/python/google/protobuf/pyext/proto2_api_test.proto
index 72c31b1c..18aecfb7 100644
--- a/python/google/protobuf/pyext/proto2_api_test.proto
+++ b/python/google/protobuf/pyext/proto2_api_test.proto
@@ -28,6 +28,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+syntax = "proto2";
+
 import "google/protobuf/internal/cpp/proto1_api_test.proto";
 
 package google.protobuf.python.internal;
diff --git a/python/google/protobuf/pyext/python.proto b/python/google/protobuf/pyext/python.proto
index d47d402c..cce645d7 100644
--- a/python/google/protobuf/pyext/python.proto
+++ b/python/google/protobuf/pyext/python.proto
@@ -33,6 +33,7 @@
 // These message definitions are used to exercises known corner cases
 // in the C++ implementation of the Python API.
 
+syntax = "proto2";
 
 package google.protobuf.python.internal;
 
@@ -63,4 +64,5 @@ message TestAllExtensions {
 
 extend TestAllExtensions {
   optional TestAllTypes.NestedMessage optional_nested_message_extension = 1;
+  repeated TestAllTypes.NestedMessage repeated_nested_message_extension = 2;
 }
diff --git a/python/google/protobuf/pyext/repeated_composite_container.cc b/python/google/protobuf/pyext/repeated_composite_container.cc
index 5c05b3d8..36fe86ae 100644
--- a/python/google/protobuf/pyext/repeated_composite_container.cc
+++ b/python/google/protobuf/pyext/repeated_composite_container.cc
@@ -65,14 +65,14 @@ namespace repeated_composite_container {
 #define GOOGLE_CHECK_ATTACHED(self)             \
   do {                                   \
     GOOGLE_CHECK_NOTNULL((self)->message);      \
-    GOOGLE_CHECK_NOTNULL((self)->parent_field); \
+    GOOGLE_CHECK_NOTNULL((self)->parent_field_descriptor); \
   } while (0);
 
 #define GOOGLE_CHECK_RELEASED(self)             \
   do {                                   \
     GOOGLE_CHECK((self)->owner.get() == NULL);  \
     GOOGLE_CHECK((self)->message == NULL);      \
-    GOOGLE_CHECK((self)->parent_field == NULL); \
+    GOOGLE_CHECK((self)->parent_field_descriptor == NULL); \
     GOOGLE_CHECK((self)->parent == NULL);       \
   } while (0);
 
@@ -122,7 +122,7 @@ static int InternalQuickSort(RepeatedCompositeContainer* self,
 
   google::protobuf::Message* message = self->message;
   const google::protobuf::Reflection* reflection = message->GetReflection();
-  const google::protobuf::FieldDescriptor* descriptor = self->parent_field->descriptor;
+  const google::protobuf::FieldDescriptor* descriptor = self->parent_field_descriptor;
   Py_ssize_t left;
   Py_ssize_t right;
 
@@ -202,7 +202,7 @@ static Py_ssize_t Length(RepeatedCompositeContainer* self) {
   google::protobuf::Message* message = self->message;
   if (message != NULL) {
     return message->GetReflection()->FieldSize(*message,
-                                               self->parent_field->descriptor);
+                                               self->parent_field_descriptor);
   } else {
     // The container has been released (i.e. by a call to Clear() or
     // ClearField() on the parent) and thus there's no message.
@@ -225,19 +225,19 @@ static int UpdateChildMessages(RepeatedCompositeContainer* self) {
   const google::protobuf::Reflection* reflection = message->GetReflection();
   for (Py_ssize_t i = child_length; i < message_length; ++i) {
     const Message& sub_message = reflection->GetRepeatedMessage(
-        *(self->message), self->parent_field->descriptor, i);
-    ScopedPyObjectPtr py_cmsg(cmessage::NewEmpty(self->subclass_init));
-    if (py_cmsg == NULL) {
+        *(self->message), self->parent_field_descriptor, i);
+    CMessage* cmsg = cmessage::NewEmptyMessage(self->subclass_init,
+                                               sub_message.GetDescriptor());
+    ScopedPyObjectPtr py_cmsg(reinterpret_cast<PyObject*>(cmsg));
+    if (cmsg == NULL) {
       return -1;
     }
-    CMessage* cmsg = reinterpret_cast<CMessage*>(py_cmsg.get());
     cmsg->owner = self->owner;
     cmsg->message = const_cast<google::protobuf::Message*>(&sub_message);
     cmsg->parent = self->parent;
-    if (cmessage::InitAttributes(cmsg, NULL, NULL) < 0) {
+    if (PyList_Append(self->child_messages, py_cmsg) < 0) {
       return -1;
     }
-    PyList_Append(self->child_messages, py_cmsg);
   }
   return 0;
 }
@@ -258,23 +258,25 @@ static PyObject* AddToAttached(RepeatedCompositeContainer* self,
   google::protobuf::Message* message = self->message;
   google::protobuf::Message* sub_message =
       message->GetReflection()->AddMessage(message,
-                                           self->parent_field->descriptor);
-  PyObject* py_cmsg = cmessage::NewEmpty(self->subclass_init);
-  if (py_cmsg == NULL) {
+                                           self->parent_field_descriptor);
+  CMessage* cmsg = cmessage::NewEmptyMessage(self->subclass_init,
+                                             sub_message->GetDescriptor());
+  if (cmsg == NULL)
     return NULL;
-  }
-  CMessage* cmsg = reinterpret_cast<CMessage*>(py_cmsg);
 
   cmsg->owner = self->owner;
   cmsg->message = sub_message;
   cmsg->parent = self->parent;
-  // cmessage::InitAttributes must be called after cmsg->message has
-  // been set.
-  if (cmessage::InitAttributes(cmsg, NULL, kwargs) < 0) {
+  if (cmessage::InitAttributes(cmsg, kwargs) < 0) {
+    Py_DECREF(cmsg);
+    return NULL;
+  }
+
+  PyObject* py_cmsg = reinterpret_cast<PyObject*>(cmsg);
+  if (PyList_Append(self->child_messages, py_cmsg) < 0) {
     Py_DECREF(py_cmsg);
     return NULL;
   }
-  PyList_Append(self->child_messages, py_cmsg);
   return py_cmsg;
 }
 
@@ -283,20 +285,16 @@ static PyObject* AddToReleased(RepeatedCompositeContainer* self,
                                PyObject* kwargs) {
   GOOGLE_CHECK_RELEASED(self);
 
-  // Create the CMessage
-  PyObject* py_cmsg = PyObject_CallObject(self->subclass_init, NULL);
+  // Create a new Message detached from the rest.
+  PyObject* py_cmsg = PyEval_CallObjectWithKeywords(
+      self->subclass_init, NULL, kwargs);
   if (py_cmsg == NULL)
     return NULL;
-  CMessage* cmsg = reinterpret_cast<CMessage*>(py_cmsg);
-  if (cmessage::InitAttributes(cmsg, NULL, kwargs) < 0) {
+
+  if (PyList_Append(self->child_messages, py_cmsg) < 0) {
     Py_DECREF(py_cmsg);
     return NULL;
   }
-
-  // The Message got created by the call to subclass_init above and
-  // it set self->owner to the newly allocated message.
-
-  PyList_Append(self->child_messages, py_cmsg);
   return py_cmsg;
 }
 
@@ -354,35 +352,9 @@ PyObject* Subscript(RepeatedCompositeContainer* self, PyObject* slice) {
   if (UpdateChildMessages(self) < 0) {
     return NULL;
   }
-  Py_ssize_t from;
-  Py_ssize_t to;
-  Py_ssize_t step;
-  Py_ssize_t length = Length(self);
-  Py_ssize_t slicelength;
-  if (PySlice_Check(slice)) {
-#if PY_MAJOR_VERSION >= 3
-    if (PySlice_GetIndicesEx(slice,
-#else
-    if (PySlice_GetIndicesEx(reinterpret_cast<PySliceObject*>(slice),
-#endif
-                             length, &from, &to, &step, &slicelength) == -1) {
-      return NULL;
-    }
-    return PyList_GetSlice(self->child_messages, from, to);
-  } else if (PyInt_Check(slice) || PyLong_Check(slice)) {
-    from = to = PyLong_AsLong(slice);
-    if (from < 0) {
-      from = to = length + from;
-    }
-    PyObject* result = PyList_GetItem(self->child_messages, from);
-    if (result == NULL) {
-      return NULL;
-    }
-    Py_INCREF(result);
-    return result;
-  }
-  PyErr_SetString(PyExc_TypeError, "index must be an integer or slice");
-  return NULL;
+  // Just forward the call to the subscript-handling function of the
+  // list containing the child messages.
+  return PyObject_GetItem(self->child_messages, slice);
 }
 
 int AssignSubscript(RepeatedCompositeContainer* self,
@@ -399,7 +371,7 @@ int AssignSubscript(RepeatedCompositeContainer* self,
   // Delete from the underlying Message, if any.
   if (self->message != NULL) {
     if (cmessage::InternalDeleteRepeatedField(self->message,
-                                              self->parent_field->descriptor,
+                                              self->parent_field_descriptor,
                                               slice,
                                               self->child_messages) < 0) {
       return -1;
@@ -512,7 +484,7 @@ static PyObject* SortAttached(RepeatedCompositeContainer* self,
   if (reverse) {
     google::protobuf::Message* message = self->message;
     const google::protobuf::Reflection* reflection = message->GetReflection();
-    const google::protobuf::FieldDescriptor* descriptor = self->parent_field->descriptor;
+    const google::protobuf::FieldDescriptor* descriptor = self->parent_field_descriptor;
 
     // Reverse the Message array.
     for (int i = 0; i < length / 2; ++i)
@@ -554,8 +526,9 @@ static PyObject* Sort(RepeatedCompositeContainer* self,
     }
   }
 
-  if (UpdateChildMessages(self) < 0)
+  if (UpdateChildMessages(self) < 0) {
     return NULL;
+  }
   if (self->message == NULL) {
     return SortReleased(self, args, kwds);
   } else {
@@ -617,7 +590,7 @@ void ReleaseLastTo(const FieldDescriptor* field,
   shared_ptr<Message> released_message(
       ReleaseLast(field, cmessage->message->GetDescriptor(), message));
   cmessage->parent = NULL;
-  cmessage->parent_field = NULL;
+  cmessage->parent_field_descriptor = NULL;
   cmessage->message = released_message.get();
   cmessage->read_only = false;
   cmessage::SetOwner(cmessage, released_message);
@@ -633,7 +606,7 @@ int Release(RepeatedCompositeContainer* self) {
   }
 
   Message* message = self->message;
-  const FieldDescriptor* field = self->parent_field->descriptor;
+  const FieldDescriptor* field = self->parent_field_descriptor;
 
   // The reflection API only lets us release the last message in a
   // repeated field.  Therefore we iterate through the children
@@ -648,7 +621,7 @@ int Release(RepeatedCompositeContainer* self) {
 
   // Detach from containing message.
   self->parent = NULL;
-  self->parent_field = NULL;
+  self->parent_field_descriptor = NULL;
   self->message = NULL;
   self->owner.reset();
 
@@ -670,22 +643,40 @@ int SetOwner(RepeatedCompositeContainer* self,
   return 0;
 }
 
-static int Init(RepeatedCompositeContainer* self,
-                PyObject* args,
-                PyObject* kwargs) {
-  self->message = NULL;
-  self->parent = NULL;
-  self->parent_field = NULL;
-  self->subclass_init = NULL;
+// The private constructor of RepeatedCompositeContainer objects.
+PyObject *NewContainer(
+    CMessage* parent,
+    const google::protobuf::FieldDescriptor* parent_field_descriptor,
+    PyObject *concrete_class) {
+  if (!CheckFieldBelongsToMessage(parent_field_descriptor, parent->message)) {
+    return NULL;
+  }
+
+  RepeatedCompositeContainer* self =
+      reinterpret_cast<RepeatedCompositeContainer*>(
+          PyType_GenericAlloc(&RepeatedCompositeContainer_Type, 0));
+  if (self == NULL) {
+    return NULL;
+  }
+
+  self->message = parent->message;
+  self->parent = parent;
+  self->parent_field_descriptor = parent_field_descriptor;
+  self->owner = parent->owner;
+  Py_INCREF(concrete_class);
+  self->subclass_init = concrete_class;
   self->child_messages = PyList_New(0);
-  return 0;
+
+  return reinterpret_cast<PyObject*>(self);
 }
 
 static void Dealloc(RepeatedCompositeContainer* self) {
   Py_CLEAR(self->child_messages);
+  Py_CLEAR(self->subclass_init);
   // TODO(tibell): Do we need to call delete on these objects to make
   // sure their destructors are called?
   self->owner.reset();
+
   Py_TYPE(self)->tp_free(reinterpret_cast<PyObject*>(self));
 }
 
@@ -755,7 +746,7 @@ PyTypeObject RepeatedCompositeContainer_Type = {
   0,                                   //  tp_descr_get
   0,                                   //  tp_descr_set
   0,                                   //  tp_dictoffset
-  (initproc)repeated_composite_container::Init,  //  tp_init
+  0,                                   //  tp_init
 };
 
 }  // namespace python
diff --git a/python/google/protobuf/pyext/repeated_composite_container.h b/python/google/protobuf/pyext/repeated_composite_container.h
index 898ef5a7..a76a5d6a 100644
--- a/python/google/protobuf/pyext/repeated_composite_container.h
+++ b/python/google/protobuf/pyext/repeated_composite_container.h
@@ -55,7 +55,6 @@ using internal::shared_ptr;
 namespace python {
 
 struct CMessage;
-struct CFieldDescriptor;
 
 // A RepeatedCompositeContainer can be in one of two states: attached
 // or released.
@@ -66,7 +65,7 @@ struct CFieldDescriptor;
 // 'child_messages' are owner by the 'owner'.
 //
 // When in the released state 'message', 'owner', 'parent', and
-// 'parent_field' are NULL.
+// 'parent_field_descriptor' are NULL.
 typedef struct RepeatedCompositeContainer {
   PyObject_HEAD;
 
@@ -82,7 +81,8 @@ typedef struct RepeatedCompositeContainer {
   CMessage* parent;
 
   // A descriptor used to modify the underlying 'message'.
-  CFieldDescriptor* parent_field;
+  // The pointer is owned by the global DescriptorPool.
+  const google::protobuf::FieldDescriptor* parent_field_descriptor;
 
   // Pointer to the C++ Message that contains this container.  The
   // RepeatedCompositeContainer does not own this pointer.
@@ -102,6 +102,13 @@ extern PyTypeObject RepeatedCompositeContainer_Type;
 
 namespace repeated_composite_container {
 
+// Builds a RepeatedCompositeContainer object, from a parent message and a
+// field descriptor.
+PyObject *NewContainer(
+    CMessage* parent,
+    const google::protobuf::FieldDescriptor* parent_field_descriptor,
+    PyObject *concrete_class);
+
 // Returns the number of items in this repeated composite container.
 static Py_ssize_t Length(RepeatedCompositeContainer* self);
 
diff --git a/python/google/protobuf/pyext/repeated_scalar_container.cc b/python/google/protobuf/pyext/repeated_scalar_container.cc
index e627d37d..49d23fd6 100644
--- a/python/google/protobuf/pyext/repeated_scalar_container.cc
+++ b/python/google/protobuf/pyext/repeated_scalar_container.cc
@@ -52,7 +52,7 @@
     #error "Python 3.0 - 3.2 are not supported."
   #else
   #define PyString_AsString(ob) \
-    (PyUnicode_Check(ob)? PyUnicode_AsUTF8(ob): PyBytes_AS_STRING(ob))
+    (PyUnicode_Check(ob)? PyUnicode_AsUTF8(ob): PyBytes_AsString(ob))
   #endif
 #endif
 
@@ -67,7 +67,7 @@ namespace repeated_scalar_container {
 static int InternalAssignRepeatedField(
     RepeatedScalarContainer* self, PyObject* list) {
   self->message->GetReflection()->ClearField(self->message,
-                                             self->parent_field->descriptor);
+                                             self->parent_field_descriptor);
   for (Py_ssize_t i = 0; i < PyList_GET_SIZE(list); ++i) {
     PyObject* value = PyList_GET_ITEM(list, i);
     if (Append(self, value) == NULL) {
@@ -80,7 +80,7 @@ static int InternalAssignRepeatedField(
 static Py_ssize_t Len(RepeatedScalarContainer* self) {
   google::protobuf::Message* message = self->message;
   return message->GetReflection()->FieldSize(*message,
-                                             self->parent_field->descriptor);
+                                             self->parent_field_descriptor);
 }
 
 static int AssignItem(RepeatedScalarContainer* self,
@@ -89,12 +89,7 @@ static int AssignItem(RepeatedScalarContainer* self,
   cmessage::AssureWritable(self->parent);
   google::protobuf::Message* message = self->message;
   const google::protobuf::FieldDescriptor* field_descriptor =
-      self->parent_field->descriptor;
-  if (!FIELD_BELONGS_TO_MESSAGE(field_descriptor, message)) {
-    PyErr_SetString(
-        PyExc_KeyError, "Field does not belong to message!");
-    return -1;
-  }
+      self->parent_field_descriptor;
 
   const google::protobuf::Reflection* reflection = message->GetReflection();
   int field_size = reflection->FieldSize(*message, field_descriptor);
@@ -175,7 +170,7 @@ static int AssignItem(RepeatedScalarContainer* self,
         ScopedPyObjectPtr s(PyObject_Str(arg));
         if (s != NULL) {
           PyErr_Format(PyExc_ValueError, "Unknown enum value: %s",
-                       PyString_AsString(s.get()));
+                       PyString_AsString(s));
         }
         return -1;
       }
@@ -193,7 +188,7 @@ static int AssignItem(RepeatedScalarContainer* self,
 static PyObject* Item(RepeatedScalarContainer* self, Py_ssize_t index) {
   google::protobuf::Message* message = self->message;
   const google::protobuf::FieldDescriptor* field_descriptor =
-      self->parent_field->descriptor;
+      self->parent_field_descriptor;
   const google::protobuf::Reflection* reflection = message->GetReflection();
 
   int field_size = reflection->FieldSize(*message, field_descriptor);
@@ -358,13 +353,7 @@ PyObject* Append(RepeatedScalarContainer* self, PyObject* item) {
   cmessage::AssureWritable(self->parent);
   google::protobuf::Message* message = self->message;
   const google::protobuf::FieldDescriptor* field_descriptor =
-      self->parent_field->descriptor;
-
-  if (!FIELD_BELONGS_TO_MESSAGE(field_descriptor, message)) {
-    PyErr_SetString(
-        PyExc_KeyError, "Field does not belong to message!");
-    return NULL;
-  }
+      self->parent_field_descriptor;
 
   const google::protobuf::Reflection* reflection = message->GetReflection();
   switch (field_descriptor->cpp_type()) {
@@ -422,7 +411,7 @@ PyObject* Append(RepeatedScalarContainer* self, PyObject* item) {
         ScopedPyObjectPtr s(PyObject_Str(item));
         if (s != NULL) {
           PyErr_Format(PyExc_ValueError, "Unknown enum value: %s",
-                       PyString_AsString(s.get()));
+                       PyString_AsString(s));
         }
         return NULL;
       }
@@ -451,7 +440,7 @@ static int AssSubscript(RepeatedScalarContainer* self,
   cmessage::AssureWritable(self->parent);
   google::protobuf::Message* message = self->message;
   const google::protobuf::FieldDescriptor* field_descriptor =
-      self->parent_field->descriptor;
+      self->parent_field_descriptor;
 
 #if PY_MAJOR_VERSION < 3
   if (PyInt_Check(slice)) {
@@ -638,47 +627,25 @@ static PyObject* Sort(RepeatedScalarContainer* self,
   Py_RETURN_NONE;
 }
 
-static int Init(RepeatedScalarContainer* self,
-                PyObject* args,
-                PyObject* kwargs) {
-  PyObject* py_parent;
-  PyObject* py_parent_field;
-  if (!PyArg_UnpackTuple(args, "__init__()", 2, 2, &py_parent,
-                         &py_parent_field)) {
-    return -1;
-  }
-
-  if (!PyObject_TypeCheck(py_parent, &CMessage_Type)) {
-    PyErr_Format(PyExc_TypeError,
-                 "expect %s, but got %s",
-                 CMessage_Type.tp_name,
-                 Py_TYPE(py_parent)->tp_name);
-    return -1;
+// The private constructor of RepeatedScalarContainer objects.
+PyObject *NewContainer(
+    CMessage* parent, const google::protobuf::FieldDescriptor* parent_field_descriptor) {
+  if (!CheckFieldBelongsToMessage(parent_field_descriptor, parent->message)) {
+    return NULL;
   }
 
-  if (!PyObject_TypeCheck(py_parent_field, &CFieldDescriptor_Type)) {
-    PyErr_Format(PyExc_TypeError,
-                 "expect %s, but got %s",
-                 CFieldDescriptor_Type.tp_name,
-                 Py_TYPE(py_parent_field)->tp_name);
-    return -1;
+  RepeatedScalarContainer* self = reinterpret_cast<RepeatedScalarContainer*>(
+      PyType_GenericAlloc(&RepeatedScalarContainer_Type, 0));
+  if (self == NULL) {
+    return NULL;
   }
 
-  CMessage* cmessage = reinterpret_cast<CMessage*>(py_parent);
-  CFieldDescriptor* cdescriptor = reinterpret_cast<CFieldDescriptor*>(
-      py_parent_field);
-
-  if (!FIELD_BELONGS_TO_MESSAGE(cdescriptor->descriptor, cmessage->message)) {
-    PyErr_SetString(
-        PyExc_KeyError, "Field does not belong to message!");
-    return -1;
-  }
+  self->message = parent->message;
+  self->parent = parent;
+  self->parent_field_descriptor = parent_field_descriptor;
+  self->owner = parent->owner;
 
-  self->message = cmessage->message;
-  self->parent = cmessage;
-  self->parent_field = cdescriptor;
-  self->owner = cmessage->owner;
-  return 0;
+  return reinterpret_cast<PyObject*>(self);
 }
 
 // Initializes the underlying Message object of "to" so it becomes a new parent
@@ -699,10 +666,7 @@ static int InitializeAndCopyToParentContainer(
   google::protobuf::Message* new_message = global_message_factory->GetPrototype(
       from->message->GetDescriptor())->New();
   to->parent = NULL;
-  // TODO(anuraag): Document why it's OK to hang on to parent_field,
-  //     even though it's a weak reference. It ought to be enough to
-  //     hold on to the FieldDescriptor only.
-  to->parent_field = from->parent_field;
+  to->parent_field_descriptor = from->parent_field_descriptor;
   to->message = new_message;
   to->owner.reset(new_message);
   if (InternalAssignRepeatedField(to, values) < 0) {
@@ -716,23 +680,17 @@ int Release(RepeatedScalarContainer* self) {
 }
 
 PyObject* DeepCopy(RepeatedScalarContainer* self, PyObject* arg) {
-  ScopedPyObjectPtr init_args(
-      PyTuple_Pack(2, self->parent, self->parent_field));
-  PyObject* clone = PyObject_CallObject(
-      reinterpret_cast<PyObject*>(&RepeatedScalarContainer_Type), init_args);
+  RepeatedScalarContainer* clone = reinterpret_cast<RepeatedScalarContainer*>(
+      PyType_GenericAlloc(&RepeatedScalarContainer_Type, 0));
   if (clone == NULL) {
     return NULL;
   }
-  if (!PyObject_TypeCheck(clone, &RepeatedScalarContainer_Type)) {
-    Py_DECREF(clone);
-    return NULL;
-  }
-  if (InitializeAndCopyToParentContainer(
-          self, reinterpret_cast<RepeatedScalarContainer*>(clone)) < 0) {
+
+  if (InitializeAndCopyToParentContainer(self, clone) < 0) {
     Py_DECREF(clone);
     return NULL;
   }
-  return clone;
+  return reinterpret_cast<PyObject*>(clone);
 }
 
 static void Dealloc(RepeatedScalarContainer* self) {
@@ -817,7 +775,7 @@ PyTypeObject RepeatedScalarContainer_Type = {
   0,                                   //  tp_descr_get
   0,                                   //  tp_descr_set
   0,                                   //  tp_dictoffset
-  (initproc)repeated_scalar_container::Init,  //  tp_init
+  0,                                   //  tp_init
 };
 
 }  // namespace python
diff --git a/python/google/protobuf/pyext/repeated_scalar_container.h b/python/google/protobuf/pyext/repeated_scalar_container.h
index 69d15d5c..513bfe48 100644
--- a/python/google/protobuf/pyext/repeated_scalar_container.h
+++ b/python/google/protobuf/pyext/repeated_scalar_container.h
@@ -41,6 +41,7 @@
 #include <google/protobuf/stubs/shared_ptr.h>
 #endif
 
+#include <google/protobuf/descriptor.h>
 
 namespace google {
 namespace protobuf {
@@ -51,7 +52,6 @@ using internal::shared_ptr;
 
 namespace python {
 
-struct CFieldDescriptor;
 struct CMessage;
 
 typedef struct RepeatedScalarContainer {
@@ -73,16 +73,22 @@ typedef struct RepeatedScalarContainer {
   // modifying the container.
   CMessage* parent;
 
-  // Weak reference to the parent's descriptor that describes this
+  // Pointer to the parent's descriptor that describes this
   // field.  Used together with the parent's message when making a
   // default message instance mutable.
-  CFieldDescriptor* parent_field;
+  // The pointer is owned by the global DescriptorPool.
+  const google::protobuf::FieldDescriptor* parent_field_descriptor;
 } RepeatedScalarContainer;
 
 extern PyTypeObject RepeatedScalarContainer_Type;
 
 namespace repeated_scalar_container {
 
+// Builds a RepeatedScalarContainer object, from a parent message and a
+// field descriptor.
+extern PyObject *NewContainer(
+    CMessage* parent, const google::protobuf::FieldDescriptor* parent_field_descriptor);
+
 // Appends the scalar 'item' to the end of the container 'self'.
 //
 // Returns None if successful; returns NULL and sets an exception if
diff --git a/python/google/protobuf/pyext/scoped_pyobject_ptr.h b/python/google/protobuf/pyext/scoped_pyobject_ptr.h
index 9f337c3c..fefebb6a 100644
--- a/python/google/protobuf/pyext/scoped_pyobject_ptr.h
+++ b/python/google/protobuf/pyext/scoped_pyobject_ptr.h
@@ -33,6 +33,8 @@
 #ifndef GOOGLE_PROTOBUF_PYTHON_CPP_SCOPED_PYOBJECT_PTR_H__
 #define GOOGLE_PROTOBUF_PYTHON_CPP_SCOPED_PYOBJECT_PTR_H__
 
+#include <google/protobuf/stubs/common.h>
+
 #include <Python.h>
 
 namespace google {
diff --git a/python/google/protobuf/text_format.py b/python/google/protobuf/text_format.py
index 2429fa59..b2f3d32c 100755
--- a/python/google/protobuf/text_format.py
+++ b/python/google/protobuf/text_format.py
@@ -112,15 +112,17 @@ def PrintMessage(message, out, indent=0, as_utf8=False, as_one_line=False,
       for element in value:
         PrintField(field, element, out, indent, as_utf8, as_one_line,
                    pointy_brackets=pointy_brackets,
+                   use_index_order=use_index_order,
                    float_format=float_format)
     else:
       PrintField(field, value, out, indent, as_utf8, as_one_line,
                  pointy_brackets=pointy_brackets,
+                 use_index_order=use_index_order,
                  float_format=float_format)
 
 
 def PrintField(field, value, out, indent=0, as_utf8=False, as_one_line=False,
-               pointy_brackets=False, float_format=None):
+               pointy_brackets=False, use_index_order=False, float_format=None):
   """Print a single field name/value pair.  For repeated fields, the value
   should be a single element."""
 
@@ -148,6 +150,7 @@ def PrintField(field, value, out, indent=0, as_utf8=False, as_one_line=False,
 
   PrintFieldValue(field, value, out, indent, as_utf8, as_one_line,
                   pointy_brackets=pointy_brackets,
+                  use_index_order=use_index_order,
                   float_format=float_format)
   if as_one_line:
     out.write(' ')
@@ -157,6 +160,7 @@ def PrintField(field, value, out, indent=0, as_utf8=False, as_one_line=False,
 
 def PrintFieldValue(field, value, out, indent=0, as_utf8=False,
                     as_one_line=False, pointy_brackets=False,
+                    use_index_order=False,
                     float_format=None):
   """Print a single field value (not including name).  For repeated fields,
   the value should be a single element."""
@@ -173,12 +177,14 @@ def PrintFieldValue(field, value, out, indent=0, as_utf8=False,
       out.write(' %s ' % openb)
       PrintMessage(value, out, indent, as_utf8, as_one_line,
                    pointy_brackets=pointy_brackets,
+                   use_index_order=use_index_order,
                    float_format=float_format)
       out.write(closeb)
     else:
       out.write(' %s\n' % openb)
       PrintMessage(value, out, indent + 2, as_utf8, as_one_line,
                    pointy_brackets=pointy_brackets,
+                   use_index_order=use_index_order,
                    float_format=float_format)
       out.write(' ' * indent + closeb)
   elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_ENUM:
diff --git a/python/setup.py b/python/setup.py
index 22a2c98f..7337260a 100755
--- a/python/setup.py
+++ b/python/setup.py
@@ -86,6 +86,8 @@ def GenerateUnittestProtos():
   generate_proto("google/protobuf/internal/more_messages.proto")
   generate_proto("google/protobuf/internal/factory_test1.proto")
   generate_proto("google/protobuf/internal/factory_test2.proto")
+  generate_proto("google/protobuf/internal/import_test_package/inner.proto")
+  generate_proto("google/protobuf/internal/import_test_package/outer.proto")
   generate_proto("google/protobuf/pyext/python.proto")
 
 def MakeTestSuite():
@@ -185,6 +187,7 @@ if __name__ == '__main__':
           'google.protobuf.descriptor_database',
           'google.protobuf.descriptor_pool',
           'google.protobuf.message_factory',
+          'google.protobuf.proto_builder',
           'google.protobuf.pyext.cpp_message',
           'google.protobuf.reflection',
           'google.protobuf.service',
diff --git a/src/Makefile.am b/src/Makefile.am
index 2e22b020..a111e14c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -38,6 +38,7 @@ MAINTAINERCLEANFILES =   \
   Makefile.in
 
 nobase_include_HEADERS =                                        \
+  google/protobuf/stubs/atomic_sequence_num.h                   \
   google/protobuf/stubs/atomicops.h                             \
   google/protobuf/stubs/atomicops_internals_arm64_gcc.h         \
   google/protobuf/stubs/atomicops_internals_arm_gcc.h           \
@@ -51,24 +52,32 @@ nobase_include_HEADERS =                                        \
   google/protobuf/stubs/atomicops_internals_tsan.h              \
   google/protobuf/stubs/atomicops_internals_x86_gcc.h           \
   google/protobuf/stubs/atomicops_internals_x86_msvc.h          \
+  google/protobuf/stubs/casts.h                                 \
+  google/protobuf/stubs/singleton.h                             \
   google/protobuf/stubs/common.h                                \
-  google/protobuf/stubs/platform_macros.h                       \
+  google/protobuf/stubs/fastmem.h                               \
   google/protobuf/stubs/once.h                                  \
+  google/protobuf/stubs/platform_macros.h                       \
   google/protobuf/stubs/stl_util.h                              \
   google/protobuf/stubs/template_util.h                         \
   google/protobuf/stubs/type_traits.h                           \
+  google/protobuf/arena.h                                       \
+  google/protobuf/arenastring.h                                 \
+  google/protobuf/descriptor_database.h                         \
   google/protobuf/descriptor.h                                  \
   google/protobuf/descriptor.pb.h                               \
-  google/protobuf/descriptor_database.h                         \
   google/protobuf/dynamic_message.h                             \
   google/protobuf/extension_set.h                               \
   google/protobuf/generated_enum_reflection.h                   \
-  google/protobuf/generated_message_util.h                      \
   google/protobuf/generated_message_reflection.h                \
+  google/protobuf/generated_message_util.h                      \
   google/protobuf/message.h                                     \
   google/protobuf/message_lite.h                                \
+  google/protobuf/metadata.h                                    \
+  google/protobuf/reflection.h                                  \
   google/protobuf/reflection_ops.h                              \
   google/protobuf/repeated_field.h                              \
+  google/protobuf/repeated_field_reflection.h                   \
   google/protobuf/service.h                                     \
   google/protobuf/text_format.h                                 \
   google/protobuf/unknown_field_set.h                           \
@@ -107,6 +116,8 @@ libprotobuf_lite_la_SOURCES =                                  \
   google/protobuf/stubs/shared_ptr.h                           \
   google/protobuf/stubs/stringprintf.cc                        \
   google/protobuf/stubs/stringprintf.h                         \
+  google/protobuf/arena.cc                                     \
+  google/protobuf/arenastring.cc                               \
   google/protobuf/extension_set.cc                             \
   google/protobuf/generated_message_util.cc                    \
   google/protobuf/message_lite.cc                              \
@@ -127,12 +138,13 @@ libprotobuf_la_SOURCES =                                       \
   google/protobuf/stubs/substitute.h                           \
   google/protobuf/stubs/structurally_valid.cc                  \
   google/protobuf/descriptor.cc                                \
-  google/protobuf/descriptor.pb.cc                             \
   google/protobuf/descriptor_database.cc                       \
+  google/protobuf/descriptor.pb.cc                             \
   google/protobuf/dynamic_message.cc                           \
   google/protobuf/extension_set_heavy.cc                       \
   google/protobuf/generated_message_reflection.cc              \
   google/protobuf/message.cc                                   \
+  google/protobuf/reflection_internal.h                        \
   google/protobuf/reflection_ops.cc                            \
   google/protobuf/service.cc                                   \
   google/protobuf/text_format.cc                               \
@@ -184,9 +196,9 @@ libprotoc_la_SOURCES =                                         \
   google/protobuf/compiler/java/java_context.cc                \
   google/protobuf/compiler/java/java_context.h                 \
   google/protobuf/compiler/java/java_enum.cc                   \
-  google/protobuf/compiler/java/java_enum.h                    \
   google/protobuf/compiler/java/java_enum_field.cc             \
   google/protobuf/compiler/java/java_enum_field.h              \
+  google/protobuf/compiler/java/java_enum.h                    \
   google/protobuf/compiler/java/java_extension.cc              \
   google/protobuf/compiler/java/java_extension.h               \
   google/protobuf/compiler/java/java_field.cc                  \
@@ -200,10 +212,12 @@ libprotoc_la_SOURCES =                                         \
   google/protobuf/compiler/java/java_helpers.h                 \
   google/protobuf/compiler/java/java_lazy_message_field.cc     \
   google/protobuf/compiler/java/java_lazy_message_field.h      \
+  google/protobuf/compiler/java/java_map_field.cc              \
+  google/protobuf/compiler/java/java_map_field.h               \
   google/protobuf/compiler/java/java_message.cc                \
-  google/protobuf/compiler/java/java_message.h                 \
   google/protobuf/compiler/java/java_message_field.cc          \
   google/protobuf/compiler/java/java_message_field.h           \
+  google/protobuf/compiler/java/java_message.h                 \
   google/protobuf/compiler/java/java_name_resolver.cc          \
   google/protobuf/compiler/java/java_name_resolver.h           \
   google/protobuf/compiler/java/java_primitive_field.cc        \
@@ -226,18 +240,25 @@ protoc_SOURCES = google/protobuf/compiler/main.cc
 
 protoc_inputs =                                                \
   google/protobuf/unittest.proto                               \
-  google/protobuf/unittest_empty.proto                         \
-  google/protobuf/unittest_import.proto                        \
-  google/protobuf/unittest_import_public.proto                 \
-  google/protobuf/unittest_mset.proto                          \
-  google/protobuf/unittest_optimize_for.proto                  \
-  google/protobuf/unittest_embed_optimize_for.proto            \
+  google/protobuf/unittest_arena.proto                         \
   google/protobuf/unittest_custom_options.proto                \
-  google/protobuf/unittest_lite.proto                          \
+  google/protobuf/unittest_drop_unknown_fields.proto           \
+  google/protobuf/unittest_embed_optimize_for.proto            \
+  google/protobuf/unittest_empty.proto                         \
   google/protobuf/unittest_import_lite.proto                   \
+  google/protobuf/unittest_import.proto                        \
   google/protobuf/unittest_import_public_lite.proto            \
+  google/protobuf/unittest_import_public.proto                 \
   google/protobuf/unittest_lite_imports_nonlite.proto          \
+  google/protobuf/unittest_lite.proto                          \
+  google/protobuf/unittest_mset.proto                          \
+  google/protobuf/unittest_no_arena_import.proto               \
+  google/protobuf/unittest_no_arena.proto                      \
+  google/protobuf/unittest_no_field_presence.proto             \
   google/protobuf/unittest_no_generic_services.proto           \
+  google/protobuf/unittest_optimize_for.proto                  \
+  google/protobuf/unittest_preserve_unknown_enum.proto         \
+  google/protobuf/unittest_proto3_arena.proto                  \
   google/protobuf/compiler/cpp/cpp_test_bad_identifiers.proto
 
 EXTRA_DIST =                                                   \
@@ -273,24 +294,38 @@ protoc_outputs =                                               \
   $(protoc_lite_outputs)                                       \
   google/protobuf/unittest.pb.cc                               \
   google/protobuf/unittest.pb.h                                \
+  google/protobuf/unittest_arena.pb.cc                         \
+  google/protobuf/unittest_arena.pb.h                          \
+  google/protobuf/unittest_custom_options.pb.cc                \
+  google/protobuf/unittest_custom_options.pb.h                 \
+  google/protobuf/unittest_drop_unknown_fields.pb.cc           \
+  google/protobuf/unittest_drop_unknown_fields.pb.h            \
+  google/protobuf/unittest_embed_optimize_for.pb.cc            \
+  google/protobuf/unittest_embed_optimize_for.pb.h             \
   google/protobuf/unittest_empty.pb.cc                         \
   google/protobuf/unittest_empty.pb.h                          \
   google/protobuf/unittest_import.pb.cc                        \
   google/protobuf/unittest_import.pb.h                         \
   google/protobuf/unittest_import_public.pb.cc                 \
   google/protobuf/unittest_import_public.pb.h                  \
-  google/protobuf/unittest_mset.pb.cc                          \
-  google/protobuf/unittest_mset.pb.h                           \
-  google/protobuf/unittest_optimize_for.pb.cc                  \
-  google/protobuf/unittest_optimize_for.pb.h                   \
-  google/protobuf/unittest_embed_optimize_for.pb.cc            \
-  google/protobuf/unittest_embed_optimize_for.pb.h             \
-  google/protobuf/unittest_custom_options.pb.cc                \
-  google/protobuf/unittest_custom_options.pb.h                 \
   google/protobuf/unittest_lite_imports_nonlite.pb.cc          \
   google/protobuf/unittest_lite_imports_nonlite.pb.h           \
+  google/protobuf/unittest_mset.pb.cc                          \
+  google/protobuf/unittest_mset.pb.h                           \
+  google/protobuf/unittest_no_arena.pb.cc                      \
+  google/protobuf/unittest_no_arena.pb.h                       \
+  google/protobuf/unittest_no_arena_import.pb.cc               \
+  google/protobuf/unittest_no_arena_import.pb.h                \
+  google/protobuf/unittest_no_field_presence.pb.cc             \
+  google/protobuf/unittest_no_field_presence.pb.h              \
   google/protobuf/unittest_no_generic_services.pb.cc           \
   google/protobuf/unittest_no_generic_services.pb.h            \
+  google/protobuf/unittest_optimize_for.pb.cc                  \
+  google/protobuf/unittest_optimize_for.pb.h                   \
+  google/protobuf/unittest_preserve_unknown_enum.pb.cc         \
+  google/protobuf/unittest_preserve_unknown_enum.pb.h          \
+  google/protobuf/unittest_proto3_arena.pb.cc                  \
+  google/protobuf/unittest_proto3_arena.pb.h                   \
   google/protobuf/compiler/cpp/cpp_test_bad_identifiers.pb.cc  \
   google/protobuf/compiler/cpp/cpp_test_bad_identifiers.pb.h
 
@@ -342,15 +377,21 @@ protobuf_test_SOURCES =                                        \
   google/protobuf/stubs/stringprintf_unittest.cc               \
   google/protobuf/stubs/template_util_unittest.cc              \
   google/protobuf/stubs/type_traits_unittest.cc                \
+  google/protobuf/arenastring_unittest.cc                      \
+  google/protobuf/arena_unittest.cc                            \
   google/protobuf/descriptor_database_unittest.cc              \
   google/protobuf/descriptor_unittest.cc                       \
+  google/protobuf/drop_unknown_fields_test.cc                  \
   google/protobuf/dynamic_message_unittest.cc                  \
   google/protobuf/extension_set_unittest.cc                    \
   google/protobuf/generated_message_reflection_unittest.cc     \
   google/protobuf/message_unittest.cc                          \
+  google/protobuf/no_field_presence_test.cc                    \
+  google/protobuf/preserve_unknown_enum_test.cc                \
+  google/protobuf/proto3_arena_unittest.cc                     \
   google/protobuf/reflection_ops_unittest.cc                   \
-  google/protobuf/repeated_field_unittest.cc                   \
   google/protobuf/repeated_field_reflection_unittest.cc        \
+  google/protobuf/repeated_field_unittest.cc                   \
   google/protobuf/text_format_unittest.cc                      \
   google/protobuf/unknown_field_set_unittest.cc                \
   google/protobuf/wire_format_unittest.cc                      \
diff --git a/src/google/protobuf/arena.cc b/src/google/protobuf/arena.cc
new file mode 100644
index 00000000..59863986
--- /dev/null
+++ b/src/google/protobuf/arena.cc
@@ -0,0 +1,238 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/arena.h>
+
+namespace google {
+namespace protobuf {
+
+google::protobuf::internal::SequenceNumber Arena::lifecycle_id_generator_;
+__thread Arena::ThreadCache Arena::thread_cache_ = { -1, NULL };
+
+void Arena::Init(const ArenaOptions& options) {
+  lifecycle_id_ = lifecycle_id_generator_.GetNext();
+  start_block_size_ = options.start_block_size;
+  max_block_size_ = options.max_block_size;
+  block_alloc = options.block_alloc;
+  block_dealloc = options.block_dealloc;
+  blocks_ = NULL;
+  hint_ = NULL;
+  owns_first_block_ = true;
+  cleanup_list_ = NULL;
+
+  if (options.initial_block != NULL && options.initial_block_size > 0) {
+    // Add first unowned block to list.
+    Block* first_block = reinterpret_cast<Block*>(options.initial_block);
+    first_block->size = options.initial_block_size;
+    first_block->pos = kHeaderSize;
+    first_block->next = NULL;
+    first_block->owner = &first_block->owner;
+    AddBlock(first_block);
+    owns_first_block_ = false;
+  }
+}
+
+uint64 Arena::Reset() {
+  CleanupList();
+  uint64 space_used = FreeBlocks();
+  // Invalidate any ThreadCaches pointing to any blocks we just destroyed.
+  lifecycle_id_ = lifecycle_id_generator_.GetNext();
+  return space_used;
+}
+
+Arena::Block* Arena::NewBlock(void* me, Block* my_last_block, size_t n,
+                              size_t start_block_size, size_t max_block_size) {
+  size_t size;
+  if (my_last_block != NULL) {
+    // Double the current block size, up to a limit.
+    size = 2 * (my_last_block->size);
+    if (size > max_block_size) size = max_block_size;
+  } else {
+    size = start_block_size;
+  }
+  if (n > size - kHeaderSize) {
+    // TODO(sanjay): Check if n + kHeaderSize would overflow
+    size = kHeaderSize + n;
+  }
+
+  Block* b = reinterpret_cast<Block*>(block_alloc(size));
+  b->pos = kHeaderSize + n;
+  b->size = size;
+  if (b->avail() == 0) {
+    // Do not attempt to reuse this block.
+    b->owner = NULL;
+  } else {
+    b->owner = me;
+  }
+  return b;
+}
+
+void Arena::AddBlock(Block* b) {
+  MutexLock l(&blocks_lock_);
+  b->next = reinterpret_cast<Block*>(google::protobuf::internal::NoBarrier_Load(&blocks_));
+  google::protobuf::internal::Release_Store(&blocks_, reinterpret_cast<google::protobuf::internal::AtomicWord>(b));
+  if (b->avail() != 0) {
+    // Direct future allocations to this block.
+    google::protobuf::internal::Release_Store(&hint_, reinterpret_cast<google::protobuf::internal::AtomicWord>(b));
+  }
+}
+
+void Arena::AddListNode(void* elem, void (*cleanup)(void*)) {
+  Node* node = reinterpret_cast<Node*>(AllocateAligned(sizeof(Node)));
+  node->elem = elem;
+  node->cleanup = cleanup;
+  node->next = reinterpret_cast<Node*>(
+      google::protobuf::internal::NoBarrier_AtomicExchange(&cleanup_list_,
+            reinterpret_cast<google::protobuf::internal::AtomicWord>(node)));
+}
+
+void* Arena::AllocateAligned(size_t n) {
+  // Align n to next multiple of 8 (from Hacker's Delight, Chapter 3.)
+  n = (n + 7) & -8;
+
+  // If this thread already owns a block in this arena then try to use that.
+  // This fast path optimizes the case where multiple threads allocate from the
+  // same arena.
+  if (thread_cache_.last_lifecycle_id_seen == lifecycle_id_ &&
+      thread_cache_.last_block_used_ != NULL) {
+    if (thread_cache_.last_block_used_->avail() < n) {
+      return SlowAlloc(n);
+    }
+    return AllocFromBlock(thread_cache_.last_block_used_, n);
+  }
+
+  // Check whether we own the last accessed block on this arena.
+  // This fast path optimizes the case where a single thread uses multiple
+  // arenas.
+  void* me = &thread_cache_;
+  Block* b = reinterpret_cast<Block*>(google::protobuf::internal::Acquire_Load(&hint_));
+  if (!b || b->owner != me || b->avail() < n) {
+    // If the next block to allocate from is the first block, try to claim it
+    // for this thread.
+    if (!owns_first_block_ && b->next == NULL) {
+      MutexLock l(&blocks_lock_);
+      if (b->owner == &b->owner) {
+        b->owner = me;
+        SetThreadCacheBlock(b);
+        return AllocFromBlock(b, n);
+      }
+    }
+    return SlowAlloc(n);
+  }
+  return AllocFromBlock(b, n);
+}
+
+void* Arena::AllocFromBlock(Block* b, size_t n) {
+  size_t p = b->pos;
+  b->pos = p + n;
+  return reinterpret_cast<char*>(b) + p;
+}
+
+void* Arena::SlowAlloc(size_t n) {
+  void* me = &thread_cache_;
+  Block* b = FindBlock(me);  // Find block owned by me.
+  // See if allocation fits in my latest block.
+  if (b != NULL && b->avail() >= n) {
+    SetThreadCacheBlock(b);
+    google::protobuf::internal::NoBarrier_Store(&hint_, reinterpret_cast<google::protobuf::internal::AtomicWord>(b));
+    return AllocFromBlock(b, n);
+  }
+  b = NewBlock(me, b, n, start_block_size_, max_block_size_);
+  AddBlock(b);
+  if (b->owner == me) {  // If this block can be reused (see NewBlock()).
+    SetThreadCacheBlock(b);
+  }
+  return reinterpret_cast<char*>(b) + kHeaderSize;
+}
+
+uint64 Arena::SpaceUsed() const {
+  uint64 space_used = 0;
+  Block* b = reinterpret_cast<Block*>(google::protobuf::internal::NoBarrier_Load(&blocks_));
+  while (b != NULL) {
+    space_used += (b->size);
+    b = b->next;
+  }
+  return space_used;
+}
+
+
+uint64 Arena::FreeBlocks() {
+  uint64 space_used = 0;
+  Block* b = reinterpret_cast<Block*>(google::protobuf::internal::NoBarrier_Load(&blocks_));
+  Block* first_block = NULL;
+  while (b != NULL) {
+    space_used += (b->size);
+    Block* next = b->next;
+    if (next != NULL) {
+      block_dealloc(b, b->size);
+    } else {
+      if (owns_first_block_) {
+        block_dealloc(b, b->size);
+      } else {
+        // User passed in the first block, skip free'ing the memory.
+        first_block = b;
+      }
+    }
+    b = next;
+  }
+  blocks_ = 0;
+  hint_ = 0;
+  if (!owns_first_block_) {
+    // Make the first block that was passed in through ArenaOptions
+    // available for reuse.
+    first_block->pos = kHeaderSize;
+    first_block->owner = &first_block->owner;
+    AddBlock(first_block);
+  }
+  return space_used;
+}
+
+void Arena::CleanupList() {
+  Node* head =
+      reinterpret_cast<Node*>(google::protobuf::internal::NoBarrier_Load(&cleanup_list_));
+  while (head != NULL) {
+    head->cleanup(head->elem);
+    head = head->next;
+  }
+  cleanup_list_ = 0;
+}
+
+Arena::Block* Arena::FindBlock(void* me) {
+  // TODO(sanjay): We might want to keep a separate list with one
+  // entry per thread.
+  Block* b = reinterpret_cast<Block*>(google::protobuf::internal::Acquire_Load(&blocks_));
+  while (b != NULL && b->owner != me) {
+    b = b->next;
+  }
+  return b;
+}
+
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/arena.h b/src/google/protobuf/arena.h
new file mode 100644
index 00000000..519e3569
--- /dev/null
+++ b/src/google/protobuf/arena.h
@@ -0,0 +1,479 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This header is logically internal, but is made public because it is used
+// from protocol-compiler-generated code, which may reside in other components.
+
+#ifndef GOOGLE_PROTOBUF_ARENA_H__
+#define GOOGLE_PROTOBUF_ARENA_H__
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/atomic_sequence_num.h>
+#include <google/protobuf/stubs/atomicops.h>
+#include <google/protobuf/stubs/type_traits.h>
+
+namespace google {
+namespace protobuf {
+
+class Arena;       // defined below
+class Message;     // message.h
+
+namespace internal {
+class ArenaString; // arenastring.h
+class LazyField;   // lazy_field.h
+
+template<typename Type>
+class GenericTypeHandler; // repeated_field.h
+
+// Templated cleanup methods.
+template<typename T> void arena_destruct_object(void* object) {
+  reinterpret_cast<T*>(object)->~T();
+}
+template<typename T> void arena_delete_object(void* object) {
+  delete reinterpret_cast<T*>(object);
+}
+inline void arena_free(void* object, size_t size) {
+  free(object);
+}
+
+}  // namespace internal
+
+// ArenaOptions provides optional additional parameters to arena construction
+// that control its block-allocation behavior.
+struct ArenaOptions {
+  // This defines the size of the first block requested from the system malloc.
+  // Subsequent block sizes will increase in a geometric series up to a maximum.
+  size_t start_block_size;
+
+  // This defines the maximum block size requested from system malloc (unless an
+  // individual arena allocation request occurs with a size larger than this
+  // maximum). Requested block sizes increase up to this value, then remain
+  // here.
+  size_t max_block_size;
+
+  // An initial block of memory for the arena to use, or NULL for none. If
+  // provided, the block must live at least as long as the arena itself. The
+  // creator of the Arena retains ownership of the block after the Arena is
+  // destroyed.
+  char* initial_block;
+
+  // The size of the initial block, if provided.
+  size_t initial_block_size;
+
+  // A function pointer to an alloc method that returns memory blocks of size
+  // requested. By default, it contains a ptr to the malloc function.
+  void* (*block_alloc)(size_t);
+  // A function pointer to a dealloc method that takes ownership of the blocks
+  // from the arena. By default, it contains a ptr to a wrapper function that
+  // calls free.
+  void (*block_dealloc)(void*, size_t);
+
+  ArenaOptions()
+      : start_block_size(kDefaultStartBlockSize),
+        max_block_size(kDefaultMaxBlockSize),
+        initial_block(NULL),
+        initial_block_size(0),
+        block_alloc(&malloc),
+        block_dealloc(&internal::arena_free) {}
+
+ private:
+  // Constants define default starting block size and max block size for
+  // arena allocator behavior -- see descriptions above.
+  static const size_t kDefaultStartBlockSize = 256;
+  static const size_t kDefaultMaxBlockSize   = 8192;
+};
+
+// Arena allocator. Arena allocation replaces ordinary (heap-based) allocation
+// with new/delete, and improves performance by aggregating allocations into
+// larger blocks and freeing allocations all at once. Protocol messages are
+// allocated on an arena by using Arena::CreateMessage<T>(Arena*), below, and
+// are automatically freed when the arena is destroyed.
+//
+// This is a thread-safe implementation: multiple threads may allocate from the
+// arena concurrently. Destruction is not thread-safe and the destructing
+// thread must synchronize with users of the arena first.
+class LIBPROTOBUF_EXPORT Arena {
+ public:
+  // Arena constructor taking custom options. See ArenaOptions below for
+  // descriptions of the options available.
+  explicit Arena(const ArenaOptions& options) {
+    Init(options);
+  }
+
+  // Default constructor with sensible default options, tuned for average
+  // use-cases.
+  Arena() {
+    Init(ArenaOptions());
+  }
+
+  // Destructor deletes all owned heap allocated objects, and destructs objects
+  // that have non-trivial destructors, except for proto2 message objects whose
+  // destructors can be skipped. Also, frees all blocks except the initial block
+  // if it was passed in.
+  ~Arena() {
+    Reset();
+  }
+
+  // API to create proto2 message objects on the arena. If the arena passed in
+  // is NULL, then a heap allocated object is returned. Type T must be a message
+  // defined in a .proto file with cc_enable_arenas set to true, otherwise a
+  // compilation error will occur.
+  //
+  // RepeatedField and RepeatedPtrField may also be instantiated directly on an
+  // arena with this method: they act as "arena-capable message types" for the
+  // purposes of the Arena API.
+  template <typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static T* CreateMessage(::google::protobuf::Arena* arena) {
+    if (arena == NULL) {
+      return new T;
+    } else {
+      return arena->CreateMessageInternal<T>(static_cast<T*>(0));
+    }
+  }
+
+  // API to create any objects on the arena. Note that only the object will
+  // be created on the arena; the underlying ptrs (in case of a proto2 message)
+  // will be still heap allocated. Proto messages should usually be allocated
+  // with CreateMessage<T>() instead.
+  template <typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static T* Create(::google::protobuf::Arena* arena) {
+    if (arena == NULL) {
+      return new T();
+    } else {
+      return arena->CreateInternal<T>(
+          SkipDeleteList<T>(static_cast<T*>(0)));
+    }
+  }
+
+  // Version of the above with one constructor argument for the created object.
+  template <typename T, typename Arg> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static T* Create(::google::protobuf::Arena* arena, const Arg& arg) {
+    if (arena == NULL) {
+      return new T(arg);
+    } else {
+      return arena->CreateInternal<T>(SkipDeleteList<T>(static_cast<T*>(0)),
+                                      arg);
+    }
+  }
+
+  // Version of the above with two constructor arguments for the created object.
+  template <typename T, typename Arg1, typename Arg2> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static T* Create(::google::protobuf::Arena* arena, const Arg1& arg1, const Arg2& arg2) {
+    if (arena == NULL) {
+      return new T(arg1, arg2);
+    } else {
+      return arena->CreateInternal<T>(SkipDeleteList<T>(static_cast<T*>(0)),
+                                      arg1,
+                                      arg2);
+    }
+  }
+
+  // Create an array of object type T on the arena. Type T must have a trivial
+  // constructor, as it will not be invoked when created on the arena.
+  template <typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static T* CreateArray(::google::protobuf::Arena* arena, size_t num_elements) {
+    if (arena == NULL) {
+      return new T[num_elements];
+    } else {
+      return static_cast<T*>(
+          arena->AllocateAligned(num_elements * sizeof(T)));
+    }
+  }
+
+  // Returns the total space used by the arena, which is the sums of the sizes
+  // of the underlying blocks. The total space used may not include the new
+  // blocks that are allocated by this arena from other threads concurrently
+  // with the call to this method.
+  uint64 SpaceUsed() const GOOGLE_ATTRIBUTE_NOINLINE;
+
+  // Frees all storage allocated by this arena after calling destructors
+  // registered with OwnDestructor() and freeing objects registered with Own().
+  // Any objects allocated on this arena are unusable after this call. It also
+  // returns the total space used by the arena which is the sums of the sizes
+  // of the allocated blocks. This method is not thread-safe.
+  uint64 Reset() GOOGLE_ATTRIBUTE_NOINLINE;
+
+  // Adds |object| to a list of heap-allocated objects to be freed with |delete|
+  // when the arena is destroyed or reset.
+  template <typename T> GOOGLE_ATTRIBUTE_NOINLINE
+  void Own(T* object) {
+    OwnInternal(object, google::protobuf::internal::is_convertible<T*, ::google::protobuf::Message*>());
+  }
+
+  // Adds |object| to a list of objects whose destructors will be manually
+  // called when the arena is destroyed or reset. This differs from Own() in
+  // that it does not free the underlying memory with |delete|; hence, it is
+  // normally only used for objects that are placement-newed into
+  // arena-allocated memory.
+  template <typename T> GOOGLE_ATTRIBUTE_NOINLINE
+  void OwnDestructor(T* object) {
+    if (object != NULL) {
+      AddListNode(object, &internal::arena_destruct_object<T>);
+    }
+  }
+
+  // Adds a custom member function on an object to the list of destructors that
+  // will be manually called when the arena is destroyed or reset. This differs
+  // from OwnDestructor() in that any member function may be specified, not only
+  // the class destructor.
+  void OwnCustomDestructor(void* object, void (*destruct)(void*))
+      GOOGLE_ATTRIBUTE_NOINLINE {
+    AddListNode(object, destruct);
+  }
+
+  // Retrieves the arena associated with |value| if |value| is an arena-capable
+  // message, or NULL otherwise. This differs from value->GetArena() in that the
+  // latter is a virtual call, while this method is a templated call that
+  // resolves at compile-time.
+  template<typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static inline ::google::protobuf::Arena* GetArena(T* value) {
+    return GetArenaInternal(value, static_cast<T*>(0));
+  }
+
+  // Helper typetrait that indicates support for arenas in a type T at compile
+  // time. This is public only to allow construction of higher-level templated
+  // utilities. is_arena_constructable<T>::value is an instance of
+  // google::protobuf::internal::true_type if the message type T has arena support enabled, and
+  // google::protobuf::internal::false_type otherwise.
+  //
+  // This is inside Arena because only Arena has the friend relationships
+  // necessary to see the underlying generated code traits.
+  template<typename T>
+  struct is_arena_constructable {
+    template<typename U>
+    static char ArenaConstructable(
+        const typename U::InternalArenaConstructable_*);
+    template<typename U>
+    static double ArenaConstructable(...);
+
+    // This will resolve to either google::protobuf::internal::true_type or google::protobuf::internal::false_type.
+    typedef google::protobuf::internal::integral_constant<bool,
+              sizeof(ArenaConstructable<const T>(static_cast<const T*>(0))) ==
+              sizeof(char)> type;
+    static const type value;
+  };
+
+ private:
+  // Blocks are variable length malloc-ed objects.  The following structure
+  // describes the common header for all blocks.
+  struct Block {
+    void* owner;   // &ThreadCache of thread that owns this block, or
+                   // &this->owner if not yet owned by a thread.
+    Block* next;   // Next block in arena (may have different owner)
+    // ((char*) &block) + pos is next available byte. It is always
+    // aligned at a multiple of 8 bytes.
+    size_t pos;
+    size_t size;  // total size of the block.
+    size_t avail() const GOOGLE_ATTRIBUTE_ALWAYS_INLINE { return size - pos; }
+    // data follows
+  };
+
+  void* (*block_alloc)(size_t);  // Allocates a free block of a particular size.
+  void (*block_dealloc)(void*, size_t);  // Deallocates the given block.
+
+  template<typename Type> friend class ::google::protobuf::internal::GenericTypeHandler;
+  friend class MockArena;              // For unit-testing.
+  friend class internal::ArenaString;  // For AllocateAligned.
+  friend class internal::LazyField;    // For CreateMaybeMessage.
+
+  struct ThreadCache {
+    // The ThreadCache is considered valid as long as this matches the
+    // lifecycle_id of the arena being used.
+    int64 last_lifecycle_id_seen;
+    Block* last_block_used_;
+  };
+
+  static const size_t kHeaderSize = sizeof(Block);
+  static google::protobuf::internal::SequenceNumber lifecycle_id_generator_;
+  static __thread ThreadCache thread_cache_;
+
+  // SFINAE for skipping addition to delete list for a Type. This is mainly to
+  // skip proto2/proto1 message objects with cc_enable_arenas=true from being
+  // part of the delete list. Also, note, compiler will optimize out the branch
+  // in CreateInternal<T>.
+  //
+  template<typename T>
+  static inline bool SkipDeleteList(typename T::DestructorSkippable_*) {
+    return true;
+  }
+
+  // For non message objects, we skip addition to delete list if the object has
+  // a trivial destructor.
+  template<typename T>
+  static inline bool SkipDeleteList(...) {
+    return google::protobuf::internal::has_trivial_destructor<T>::value;
+  }
+
+  // CreateMessage<T> requires that T supports arenas, but this private method
+  // works whether or not T supports arenas. These are not exposed to user code
+  // as it can cause confusing API usages, and end up having double free in
+  // user code. These are used only internally from LazyField and Repeated
+  // fields, since they are designed to work in all mode combinations.
+  template<typename Msg> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static Msg* CreateMaybeMessage(
+      Arena* arena, typename Msg::InternalArenaConstructable_*) {
+    return CreateMessage<Msg>(arena);
+  }
+
+  template<typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static T* CreateMaybeMessage(Arena* arena, ...) {
+    return Create<T>(arena);
+  }
+
+  template <typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  inline T* CreateInternal(
+      bool skip_explicit_ownership) {
+    T* t = new (AllocateAligned(sizeof(T))) T();
+    if (!skip_explicit_ownership) {
+      AddListNode(t, &internal::arena_destruct_object<T>);
+    }
+    return t;
+  }
+
+  template <typename T, typename Arg> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  inline T* CreateInternal(
+      bool skip_explicit_ownership, const Arg& arg) {
+    T* t = new (AllocateAligned(sizeof(T))) T(arg);
+    if (!skip_explicit_ownership) {
+      AddListNode(t, &internal::arena_destruct_object<T>);
+    }
+    return t;
+  }
+
+  template <typename T, typename Arg1, typename Arg2> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  inline T* CreateInternal(
+      bool skip_explicit_ownership, const Arg1& arg1, const Arg2& arg2) {
+    T* t = new (AllocateAligned(sizeof(T))) T(arg1, arg2);
+    if (!skip_explicit_ownership) {
+      AddListNode(t, &internal::arena_destruct_object<T>);
+    }
+    return t;
+  }
+
+  template <typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  inline T* CreateMessageInternal(typename T::InternalArenaConstructable_*) {
+    return CreateInternal<T, Arena*>(SkipDeleteList<T>(static_cast<T*>(0)),
+                                     this);
+  }
+
+  // These implement Own(), which registers an object for deletion (destructor
+  // call and operator delete()). The second parameter has type 'true_type' if T
+  // is a subtype of ::google::protobuf::Message and 'false_type' otherwise. Collapsing
+  // all template instantiations to one for generic Message reduces code size,
+  // using the virtual destructor instead.
+  template<typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  void OwnInternal(T* object, google::protobuf::internal::true_type) {
+    if (object != NULL) {
+      AddListNode(object, &internal::arena_delete_object< ::google::protobuf::Message >);
+    }
+  }
+  template<typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  void OwnInternal(T* object, google::protobuf::internal::false_type) {
+    if (object != NULL) {
+      AddListNode(object, &internal::arena_delete_object<T>);
+    }
+  }
+
+  // Implementation for GetArena(). Only message objects with
+  // InternalArenaConstructable_ tags can be associated with an arena, and such
+  // objects must implement a GetArenaNoVirtual() method.
+  template<typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static inline ::google::protobuf::Arena* GetArenaInternal(T* value,
+      typename T::InternalArenaConstructable_*) {
+    return value->GetArenaNoVirtual();
+  }
+
+  template<typename T> GOOGLE_ATTRIBUTE_ALWAYS_INLINE
+  static inline ::google::protobuf::Arena* GetArenaInternal(T* value, ...) {
+    return NULL;
+  }
+
+
+  void* AllocateAligned(size_t size);
+
+  void Init(const ArenaOptions& options);
+
+  // Free all blocks and return the total space used which is the sums of sizes
+  // of the all the allocated blocks.
+  uint64 FreeBlocks();
+
+  // Add object pointer and cleanup function pointer to the list.
+  // TODO(rohananil, cfallin): We could pass in a sub-arena into this method
+  // to avoid polluting blocks of this arena with list nodes. This would help in
+  // mixed mode (where many protobufs have cc_enable_arenas=false), and is an
+  // alternative to a chunked linked-list, but with extra overhead of *next.
+  void AddListNode(void* elem, void (*cleanup)(void*));
+  // Delete or Destruct all objects owned by the arena.
+  void CleanupList();
+
+  inline void SetThreadCacheBlock(Block* block) {
+    thread_cache_.last_block_used_ = block;
+    thread_cache_.last_lifecycle_id_seen = lifecycle_id_;
+  }
+
+  int64 lifecycle_id_;  // Unique for each arena. Changes on Reset().
+  size_t start_block_size_;  // Starting block size of the arena.
+  size_t max_block_size_;    // Max block size of the arena.
+
+  google::protobuf::internal::AtomicWord blocks_;  // Head of linked list of all allocated blocks
+  google::protobuf::internal::AtomicWord hint_;    // Fast thread-local block access
+
+  // Node contains the ptr of the object to be cleaned up and the associated
+  // cleanup function ptr.
+  struct Node {
+    void* elem;              // Pointer to the object to be cleaned up.
+    void (*cleanup)(void*);  // Function pointer to the destructor or deleter.
+    Node* next;              // Next node in the list.
+  };
+
+  google::protobuf::internal::AtomicWord cleanup_list_;  // Head of a linked list of nodes containing object
+                             // ptrs and cleanup methods.
+
+  bool owns_first_block_;    // Indicates that arena owns the first block
+  Mutex blocks_lock_;
+
+  void AddBlock(Block* b);
+  void* SlowAlloc(size_t n);
+  Block* FindBlock(void* me);
+  Block* NewBlock(void* me, Block* my_last_block, size_t n,
+                  size_t start_block_size, size_t max_block_size);
+  static void* AllocFromBlock(Block* b, size_t n);
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Arena);
+};
+
+template<typename T>
+const typename Arena::is_arena_constructable<T>::type
+    Arena::is_arena_constructable<T>::value =
+        typename Arena::is_arena_constructable<T>::type();
+
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_ARENA_H__
diff --git a/src/google/protobuf/arena_nc.cc b/src/google/protobuf/arena_nc.cc
new file mode 100644
index 00000000..f2f08427
--- /dev/null
+++ b/src/google/protobuf/arena_nc.cc
@@ -0,0 +1,45 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Negative compilation test for arena usage.
+
+#include <google/protobuf/arena.h>
+#include <google/protobuf/unittest.pb.h>
+
+#ifdef TEST_ARENA_PRIVATE_CONSTRUCTOR
+
+namespace google {
+void ArenaPrivateConstructor() {
+  google::protobuf::Arena arena;
+  protobuf_unittest::TestAllTypes message(&arena);
+}
+
+#endif
+}  // namespace google
diff --git a/src/google/protobuf/arena_nc_test.py b/src/google/protobuf/arena_nc_test.py
new file mode 100644
index 00000000..41b1b5f8
--- /dev/null
+++ b/src/google/protobuf/arena_nc_test.py
@@ -0,0 +1,59 @@
+#! /usr/bin/python
+#
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# https://developers.google.com/protocol-buffers/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Negative compilation unit tests for arena API."""
+
+from google3.testing.pybase import fake_target_util
+from google.apputils import basetest
+
+
+class ArenaNcTest(basetest.TestCase):
+
+  def testCompilerErrors(self):
+    """Runs a list of tests to verify compiler error messages."""
+
+    # Defines a list of test specs, where each element is a tuple
+    # (test name, list of regexes for matching the compiler errors).
+    test_specs = [
+        ('ARENA_PRIVATE_CONSTRUCTOR',
+         [r'calling a protected constructor']),
+        ('SANITY', None)]
+
+    fake_target_util.AssertCcCompilerErrors(
+        self,                         # The current test case.
+        'google3/google/protobuf/arena_nc',  # The fake target file.
+        'arena_nc.o',                 # The sub-target to build.
+        test_specs                    # List of test specifications.
+        )
+
+if __name__ == '__main__':
+  basetest.main()
diff --git a/src/google/protobuf/arena_unittest.cc b/src/google/protobuf/arena_unittest.cc
new file mode 100644
index 00000000..7ab6fad8
--- /dev/null
+++ b/src/google/protobuf/arena_unittest.cc
@@ -0,0 +1,972 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/arena.h>
+
+#include <string>
+#include <vector>
+
+#include <google/protobuf/test_util.h>
+#include <google/protobuf/unittest_arena.pb.h>
+#include <google/protobuf/unittest_no_arena.pb.h>
+#include <google/protobuf/unittest.pb.h>
+#include <google/protobuf/testing/googletest.h>
+#include <gtest/gtest.h>
+
+
+namespace google {
+using proto2_arena_unittest::ArenaMessage;
+using protobuf_unittest::TestAllTypes;
+using protobuf_unittest::TestAllExtensions;
+using protobuf_unittest::TestOneof2;
+using protobuf_unittest::TestEmptyMessage;
+
+namespace protobuf {
+namespace {
+
+class Notifier {
+ public:
+  Notifier() : count_(0) {}
+  void Notify() {
+    count_++;
+  }
+  int GetCount() {
+    return count_;
+  }
+
+ private:
+  int count_;
+};
+
+class SimpleDataType {
+ public:
+  SimpleDataType() : notifier_(NULL) {}
+  void SetNotifier(Notifier* notifier) {
+    notifier_ = notifier;
+  }
+  virtual ~SimpleDataType() {
+    if (notifier_ != NULL) {
+      notifier_->Notify();
+    }
+  };
+ private:
+  Notifier* notifier_;
+};
+}  // namespace
+
+TEST(ArenaTest, ArenaConstructable) {
+  EXPECT_TRUE(Arena::is_arena_constructable<TestAllTypes>::type::value);
+  EXPECT_TRUE(Arena::is_arena_constructable<const TestAllTypes>::type::value);
+  EXPECT_FALSE(Arena::is_arena_constructable<Arena>::type::value);
+}
+
+TEST(ArenaTest, BasicCreate) {
+  Arena arena;
+  EXPECT_TRUE(Arena::Create<int32>(&arena) != NULL);
+  EXPECT_TRUE(Arena::Create<int64>(&arena) != NULL);
+  EXPECT_TRUE(Arena::Create<float>(&arena) != NULL);
+  EXPECT_TRUE(Arena::Create<double>(&arena) != NULL);
+  EXPECT_TRUE(Arena::Create<string>(&arena) != NULL);
+  arena.Own(new int32);
+  arena.Own(new int64);
+  arena.Own(new float);
+  arena.Own(new double);
+  arena.Own(new string);
+  arena.Own<int>(NULL);
+  Notifier notifier;
+  SimpleDataType* data = Arena::Create<SimpleDataType>(&arena);
+  data->SetNotifier(&notifier);
+  data = new SimpleDataType;
+  data->SetNotifier(&notifier);
+  arena.Own(data);
+  arena.Reset();
+  EXPECT_EQ(2, notifier.GetCount());
+}
+
+TEST(ArenaTest, Parsing) {
+  TestAllTypes original;
+  TestUtil::SetAllFields(&original);
+
+  // Test memory leak.
+  Arena arena;
+  TestAllTypes* arena_message = Arena::CreateMessage<TestAllTypes>(&arena);
+  arena_message->ParseFromString(original.SerializeAsString());
+  TestUtil::ExpectAllFieldsSet(*arena_message);
+
+  // Test that string fields have null terminator bytes (earlier bug).
+  EXPECT_EQ(strlen(original.optional_string().c_str()),
+            strlen(arena_message->optional_string().c_str()));
+}
+
+TEST(ArenaTest, UnknownFields) {
+  TestAllTypes original;
+  TestUtil::SetAllFields(&original);
+
+  // Test basic parsing into (populating) and reading out of unknown fields on
+  // an arena.
+  Arena arena;
+  TestEmptyMessage* arena_message =
+      Arena::CreateMessage<TestEmptyMessage>(&arena);
+  arena_message->ParseFromString(original.SerializeAsString());
+
+  TestAllTypes copied;
+  copied.ParseFromString(arena_message->SerializeAsString());
+  TestUtil::ExpectAllFieldsSet(copied);
+
+  // Exercise UFS manual manipulation (setters).
+  arena_message = Arena::CreateMessage<TestEmptyMessage>(&arena);
+  arena_message->mutable_unknown_fields()->AddVarint(
+      TestAllTypes::kOptionalInt32FieldNumber, 42);
+  copied.Clear();
+  copied.ParseFromString(arena_message->SerializeAsString());
+  EXPECT_TRUE(copied.has_optional_int32());
+  EXPECT_EQ(42, copied.optional_int32());
+
+  // Exercise UFS swap path.
+  TestEmptyMessage* arena_message_2 =
+      Arena::CreateMessage<TestEmptyMessage>(&arena);
+  arena_message_2->Swap(arena_message);
+  copied.Clear();
+  copied.ParseFromString(arena_message_2->SerializeAsString());
+  EXPECT_TRUE(copied.has_optional_int32());
+  EXPECT_EQ(42, copied.optional_int32());
+
+  // Test field manipulation.
+  TestEmptyMessage* arena_message_3 =
+      Arena::CreateMessage<TestEmptyMessage>(&arena);
+  arena_message_3->mutable_unknown_fields()->AddVarint(1000, 42);
+  arena_message_3->mutable_unknown_fields()->AddFixed32(1001, 42);
+  arena_message_3->mutable_unknown_fields()->AddFixed64(1002, 42);
+  arena_message_3->mutable_unknown_fields()->AddLengthDelimited(1003);
+  arena_message_3->mutable_unknown_fields()->DeleteSubrange(0, 2);
+  arena_message_3->mutable_unknown_fields()->DeleteByNumber(1002);
+  arena_message_3->mutable_unknown_fields()->DeleteByNumber(1003);
+  EXPECT_TRUE(arena_message_3->unknown_fields().empty());
+}
+
+TEST(ArenaTest, Swap) {
+  Arena arena1;
+  Arena arena2;
+  TestAllTypes* arena1_message;
+  TestAllTypes* arena2_message;
+
+  // Case 1: Swap(), no UFS on either message, both messages on different
+  // arenas. Arena pointers should remain the same after swap.
+  arena1_message = Arena::CreateMessage<TestAllTypes>(&arena1);
+  arena2_message = Arena::CreateMessage<TestAllTypes>(&arena2);
+  arena1_message->Swap(arena2_message);
+  EXPECT_EQ(&arena1, arena1_message->GetArena());
+  EXPECT_EQ(&arena2, arena2_message->GetArena());
+
+  // Case 2: Swap(), UFS on one message, both messages on different arenas.
+  arena1_message = Arena::CreateMessage<TestAllTypes>(&arena1);
+  arena2_message = Arena::CreateMessage<TestAllTypes>(&arena2);
+  arena1_message->mutable_unknown_fields()->AddVarint(1, 42);
+  arena1_message->Swap(arena2_message);
+  EXPECT_EQ(&arena1, arena1_message->GetArena());
+  EXPECT_EQ(&arena2, arena2_message->GetArena());
+  EXPECT_EQ(0, arena1_message->unknown_fields().field_count());
+  EXPECT_EQ(1, arena2_message->unknown_fields().field_count());
+  EXPECT_EQ(42, arena2_message->unknown_fields().field(0).varint());
+
+  // Case 3: Swap(), UFS on both messages, both messages on different arenas.
+  arena1_message = Arena::CreateMessage<TestAllTypes>(&arena1);
+  arena2_message = Arena::CreateMessage<TestAllTypes>(&arena2);
+  arena1_message->mutable_unknown_fields()->AddVarint(1, 42);
+  arena2_message->mutable_unknown_fields()->AddVarint(2, 84);
+  arena1_message->Swap(arena2_message);
+  EXPECT_EQ(&arena1, arena1_message->GetArena());
+  EXPECT_EQ(&arena2, arena2_message->GetArena());
+  EXPECT_EQ(1, arena1_message->unknown_fields().field_count());
+  EXPECT_EQ(1, arena2_message->unknown_fields().field_count());
+  EXPECT_EQ(84, arena1_message->unknown_fields().field(0).varint());
+  EXPECT_EQ(42, arena2_message->unknown_fields().field(0).varint());
+}
+
+TEST(ArenaTest, SetAllocatedMessage) {
+  Arena arena;
+  TestAllTypes *arena_message = Arena::CreateMessage<TestAllTypes>(&arena);
+  TestAllTypes::NestedMessage* nested = new TestAllTypes::NestedMessage;
+  nested->set_bb(118);
+  arena_message->set_allocated_optional_nested_message(nested);
+  EXPECT_EQ(118, arena_message->optional_nested_message().bb());
+
+  protobuf_unittest_no_arena::TestNoArenaMessage no_arena_message;
+  EXPECT_FALSE(no_arena_message.has_arena_message());
+  no_arena_message.set_allocated_arena_message(NULL);
+  EXPECT_FALSE(no_arena_message.has_arena_message());
+  no_arena_message.set_allocated_arena_message(new ArenaMessage);
+  EXPECT_TRUE(no_arena_message.has_arena_message());
+}
+
+TEST(ArenaTest, ReleaseMessage) {
+  Arena arena;
+  TestAllTypes* arena_message = Arena::CreateMessage<TestAllTypes>(&arena);
+  arena_message->mutable_optional_nested_message()->set_bb(118);
+  scoped_ptr<TestAllTypes::NestedMessage> nested(
+      arena_message->release_optional_nested_message());
+  EXPECT_EQ(118, nested->bb());
+
+  TestAllTypes::NestedMessage* released_null =
+      arena_message->release_optional_nested_message();
+  EXPECT_EQ(NULL, released_null);
+}
+
+TEST(ArenaTest, SetAllocatedString) {
+  Arena arena;
+  TestAllTypes* arena_message = Arena::CreateMessage<TestAllTypes>(&arena);
+  string* allocated_str = new string("hello");
+  arena_message->set_allocated_optional_string(allocated_str);
+  EXPECT_EQ("hello", arena_message->optional_string());
+}
+
+TEST(ArenaTest, ReleaseString) {
+  Arena arena;
+  TestAllTypes* arena_message = Arena::CreateMessage<TestAllTypes>(&arena);
+  arena_message->set_optional_string("hello");
+  scoped_ptr<string> released_str(
+      arena_message->release_optional_string());
+  EXPECT_EQ("hello", *released_str);
+
+  // Test default value.
+}
+
+
+TEST(ArenaTest, SwapBetweenArenasWithAllFieldsSet) {
+  Arena arena1;
+  TestAllTypes* arena1_message = Arena::CreateMessage<TestAllTypes>(&arena1);
+  {
+    Arena arena2;
+    TestAllTypes* arena2_message = Arena::CreateMessage<TestAllTypes>(&arena2);
+    TestUtil::SetAllFields(arena2_message);
+    arena2_message->Swap(arena1_message);
+    string output;
+    arena2_message->SerializeToString(&output);
+    EXPECT_EQ(0, output.size());
+  }
+  TestUtil::ExpectAllFieldsSet(*arena1_message);
+}
+
+TEST(ArenaTest, SwapBetweenArenaAndNonArenaWithAllFieldsSet) {
+  TestAllTypes non_arena_message;
+  TestUtil::SetAllFields(&non_arena_message);
+  {
+    Arena arena2;
+    TestAllTypes* arena2_message = Arena::CreateMessage<TestAllTypes>(&arena2);
+    TestUtil::SetAllFields(arena2_message);
+    arena2_message->Swap(&non_arena_message);
+    TestUtil::ExpectAllFieldsSet(*arena2_message);
+    TestUtil::ExpectAllFieldsSet(non_arena_message);
+  }
+}
+
+TEST(ArenaTest, UnsafeArenaSwap) {
+  Arena shared_arena;
+  TestAllTypes* message1 = Arena::CreateMessage<TestAllTypes>(&shared_arena);
+  TestAllTypes* message2 = Arena::CreateMessage<TestAllTypes>(&shared_arena);
+  TestUtil::SetAllFields(message1);
+  message1->UnsafeArenaSwap(message2);
+  TestUtil::ExpectAllFieldsSet(*message2);
+}
+
+TEST(ArenaTest, SwapBetweenArenasUsingReflection) {
+  Arena arena1;
+  TestAllTypes* arena1_message = Arena::CreateMessage<TestAllTypes>(&arena1);
+  {
+    Arena arena2;
+    TestAllTypes* arena2_message = Arena::CreateMessage<TestAllTypes>(&arena2);
+    TestUtil::SetAllFields(arena2_message);
+    const Reflection* r = arena2_message->GetReflection();
+    r->Swap(arena1_message, arena2_message);
+    string output;
+    arena2_message->SerializeToString(&output);
+    EXPECT_EQ(0, output.size());
+  }
+  TestUtil::ExpectAllFieldsSet(*arena1_message);
+}
+
+TEST(ArenaTest, SwapBetweenArenaAndNonArenaUsingReflection) {
+  TestAllTypes non_arena_message;
+  TestUtil::SetAllFields(&non_arena_message);
+  {
+    Arena arena2;
+    TestAllTypes* arena2_message = Arena::CreateMessage<TestAllTypes>(&arena2);
+    TestUtil::SetAllFields(arena2_message);
+    const Reflection* r = arena2_message->GetReflection();
+    r->Swap(&non_arena_message, arena2_message);
+    TestUtil::ExpectAllFieldsSet(*arena2_message);
+    TestUtil::ExpectAllFieldsSet(non_arena_message);
+  }
+}
+
+TEST(ArenaTest, ReleaseFromArenaMessageMakesCopy) {
+  TestAllTypes::NestedMessage* nested_msg = NULL;
+  string* nested_string = NULL;
+  {
+    Arena arena;
+    TestAllTypes* arena_message = Arena::CreateMessage<TestAllTypes>(&arena);
+    arena_message->mutable_optional_nested_message()->set_bb(42);
+    *arena_message->mutable_optional_string() = "Hello";
+    nested_msg = arena_message->release_optional_nested_message();
+    nested_string = arena_message->release_optional_string();
+  }
+  EXPECT_EQ(42, nested_msg->bb());
+  EXPECT_EQ("Hello", *nested_string);
+  delete nested_msg;
+  delete nested_string;
+}
+
+TEST(ArenaTest, ReleaseFromArenaMessageUsingReflectionMakesCopy) {
+  TestAllTypes::NestedMessage* nested_msg = NULL;
+  // Note: no string: reflection API only supports releasing submessages.
+  {
+    Arena arena;
+    TestAllTypes* arena_message = Arena::CreateMessage<TestAllTypes>(&arena);
+    arena_message->mutable_optional_nested_message()->set_bb(42);
+    const Reflection* r = arena_message->GetReflection();
+    const FieldDescriptor* f = arena_message->GetDescriptor()->FindFieldByName(
+        "optional_nested_message");
+    nested_msg = dynamic_cast<TestAllTypes::NestedMessage*>(
+        r->ReleaseMessage(arena_message, f));
+  }
+  EXPECT_EQ(42, nested_msg->bb());
+  delete nested_msg;
+}
+
+TEST(ArenaTest, UnsafeArenaReleaseDoesNotMakeCopy) {
+  Arena arena;
+  TestAllTypes* arena_message = Arena::CreateMessage<TestAllTypes>(&arena);
+  TestAllTypes::NestedMessage* nested_msg = NULL;
+  TestAllTypes::NestedMessage* orig_nested_msg = NULL;
+  string* nested_string = NULL;
+  string* orig_nested_string = NULL;
+  arena_message->mutable_optional_nested_message()->set_bb(42);
+  *arena_message->mutable_optional_string() = "Hello";
+  orig_nested_msg = arena_message->mutable_optional_nested_message();
+  orig_nested_string = arena_message->mutable_optional_string();
+  nested_msg = arena_message->unsafe_arena_release_optional_nested_message();
+  nested_string = arena_message->unsafe_arena_release_optional_string();
+
+  EXPECT_EQ(orig_nested_msg, nested_msg);
+  EXPECT_EQ(orig_nested_string, nested_string);
+  // Released pointers still on arena; no 'delete' calls needed here.
+}
+
+TEST(ArenaTest, SetAllocatedAcrossArenas) {
+  Arena arena1;
+  TestAllTypes* arena1_message = Arena::CreateMessage<TestAllTypes>(&arena1);
+  TestAllTypes::NestedMessage* heap_submessage =
+      new TestAllTypes::NestedMessage();
+  heap_submessage->set_bb(42);
+  arena1_message->set_allocated_optional_nested_message(heap_submessage);
+  // Should keep same object and add to arena's Own()-list.
+  EXPECT_EQ(heap_submessage,
+            arena1_message->mutable_optional_nested_message());
+  {
+    Arena arena2;
+    TestAllTypes::NestedMessage* arena2_submessage =
+        Arena::CreateMessage<TestAllTypes::NestedMessage>(&arena2);
+    arena2_submessage->set_bb(42);
+    arena1_message->set_allocated_optional_nested_message(arena2_submessage);
+    EXPECT_NE(arena2_submessage,
+              arena1_message->mutable_optional_nested_message());
+  }
+
+  TestAllTypes::NestedMessage* arena1_submessage =
+      Arena::CreateMessage<TestAllTypes::NestedMessage>(&arena1);
+  arena1_submessage->set_bb(42);
+  TestAllTypes* heap_message = new TestAllTypes;
+  heap_message->set_allocated_optional_nested_message(arena1_submessage);
+  EXPECT_NE(arena1_submessage,
+            heap_message->mutable_optional_nested_message());
+  delete heap_message;
+}
+
+TEST(ArenaTest, SetAllocatedAcrossArenasWithReflection) {
+  // Same as above, with reflection.
+  Arena arena1;
+  TestAllTypes* arena1_message = Arena::CreateMessage<TestAllTypes>(&arena1);
+  const Reflection* r = arena1_message->GetReflection();
+  const Descriptor* d = arena1_message->GetDescriptor();
+  const FieldDescriptor* msg_field = d->FindFieldByName(
+      "optional_nested_message");
+  TestAllTypes::NestedMessage* heap_submessage =
+      new TestAllTypes::NestedMessage();
+  heap_submessage->set_bb(42);
+  r->SetAllocatedMessage(arena1_message, heap_submessage, msg_field);
+  // Should keep same object and add to arena's Own()-list.
+  EXPECT_EQ(heap_submessage,
+            arena1_message->mutable_optional_nested_message());
+  {
+    Arena arena2;
+    TestAllTypes::NestedMessage* arena2_submessage =
+        Arena::CreateMessage<TestAllTypes::NestedMessage>(&arena2);
+    arena2_submessage->set_bb(42);
+    r->SetAllocatedMessage(arena1_message, arena2_submessage, msg_field);
+    EXPECT_NE(arena2_submessage,
+              arena1_message->mutable_optional_nested_message());
+  }
+
+  TestAllTypes::NestedMessage* arena1_submessage =
+      Arena::CreateMessage<TestAllTypes::NestedMessage>(&arena1);
+  arena1_submessage->set_bb(42);
+  TestAllTypes* heap_message = new TestAllTypes;
+  r->SetAllocatedMessage(heap_message, arena1_submessage, msg_field);
+  EXPECT_NE(arena1_submessage,
+            heap_message->mutable_optional_nested_message());
+  delete heap_message;
+}
+
+TEST(ArenaTest, AddAllocatedWithReflection) {
+  Arena arena1;
+  ArenaMessage* arena1_message = Arena::CreateMessage<ArenaMessage>(&arena1);
+  const Reflection* r = arena1_message->GetReflection();
+  const Descriptor* d = arena1_message->GetDescriptor();
+  const FieldDescriptor* fd =
+      d->FindFieldByName("repeated_import_no_arena_message");
+  // Message with cc_enable_arenas = false;
+  r->AddMessage(arena1_message, fd);
+  r->AddMessage(arena1_message, fd);
+  r->AddMessage(arena1_message, fd);
+  EXPECT_EQ(3, r->FieldSize(*arena1_message, fd));
+  // Message with cc_enable_arenas = true;
+  fd = d->FindFieldByName("repeated_nested_message");
+  r->AddMessage(arena1_message, fd);
+  r->AddMessage(arena1_message, fd);
+  r->AddMessage(arena1_message, fd);
+  EXPECT_EQ(3, r->FieldSize(*arena1_message, fd));
+}
+
+TEST(ArenaTest, RepeatedPtrFieldAddClearedTest) {
+  {
+    RepeatedPtrField<TestAllTypes> repeated_field;
+    EXPECT_TRUE(repeated_field.empty());
+    EXPECT_EQ(0, repeated_field.size());
+    // Ownership is passed to repeated_field.
+    TestAllTypes* cleared = new TestAllTypes();
+    repeated_field.AddCleared(cleared);
+    EXPECT_TRUE(repeated_field.empty());
+    EXPECT_EQ(0, repeated_field.size());
+  }
+  {
+    RepeatedPtrField<TestAllTypes> repeated_field;
+    EXPECT_TRUE(repeated_field.empty());
+    EXPECT_EQ(0, repeated_field.size());
+    // Ownership is passed to repeated_field.
+    TestAllTypes* cleared = new TestAllTypes();
+    repeated_field.AddAllocated(cleared);
+    EXPECT_FALSE(repeated_field.empty());
+    EXPECT_EQ(1, repeated_field.size());
+  }
+}
+
+// N.B.: no reflection version of this test because all the arena-specific code
+// is in RepeatedPtrField, and the reflection works implicitly based on that.
+TEST(ArenaTest, AddAllocatedToRepeatedField) {
+  // Heap->arena case.
+  Arena arena1;
+  TestAllTypes* arena1_message = Arena::CreateMessage<TestAllTypes>(&arena1);
+  for (int i = 0; i < 10; i++) {
+    TestAllTypes::NestedMessage* heap_submessage =
+        new TestAllTypes::NestedMessage();
+    heap_submessage->set_bb(42);
+    arena1_message->mutable_repeated_nested_message()->
+        AddAllocated(heap_submessage);
+    // Should not copy object -- will use arena_->Own().
+    EXPECT_EQ(heap_submessage,
+              &arena1_message->repeated_nested_message(i));
+    EXPECT_EQ(42, arena1_message->repeated_nested_message(i).bb());
+  }
+
+  // Arena1->Arena2 case.
+  arena1_message->Clear();
+  for (int i = 0; i < 10; i++) {
+    Arena arena2;
+    TestAllTypes::NestedMessage* arena2_submessage =
+        Arena::CreateMessage<TestAllTypes::NestedMessage>(&arena2);
+    arena2_submessage->set_bb(42);
+    arena1_message->mutable_repeated_nested_message()->
+        AddAllocated(arena2_submessage);
+    // Should copy object.
+    EXPECT_NE(arena2_submessage,
+              &arena1_message->repeated_nested_message(i));
+    EXPECT_EQ(42, arena1_message->repeated_nested_message(i).bb());
+  }
+
+  // Arena->heap case.
+  TestAllTypes* heap_message = new TestAllTypes();
+  for (int i = 0; i < 10; i++) {
+    Arena arena2;
+    TestAllTypes::NestedMessage* arena2_submessage =
+        Arena::CreateMessage<TestAllTypes::NestedMessage>(&arena2);
+    arena2_submessage->set_bb(42);
+    heap_message->mutable_repeated_nested_message()->
+        AddAllocated(arena2_submessage);
+    // Should copy object.
+    EXPECT_NE(arena2_submessage,
+              &heap_message->repeated_nested_message(i));
+    EXPECT_EQ(42, heap_message->repeated_nested_message(i).bb());
+  }
+  delete heap_message;
+
+  // Heap-arena case for strings (which are not arena-allocated).
+  arena1_message->Clear();
+  for (int i = 0; i < 10; i++) {
+    string* s = new string("Test");
+    arena1_message->mutable_repeated_string()->
+        AddAllocated(s);
+    // Should not copy.
+    EXPECT_EQ(s, &arena1_message->repeated_string(i));
+    EXPECT_EQ("Test", arena1_message->repeated_string(i));
+  }
+}
+
+TEST(ArenaTest, ReleaseLastRepeatedField) {
+  // Release from arena-allocated repeated field and ensure that returned object
+  // is heap-allocated.
+  Arena arena;
+  TestAllTypes* arena_message = Arena::CreateMessage<TestAllTypes>(&arena);
+  for (int i = 0; i < 10; i++) {
+    TestAllTypes::NestedMessage* nested =
+        Arena::CreateMessage<TestAllTypes::NestedMessage>(&arena);
+    nested->set_bb(42);
+    arena_message->mutable_repeated_nested_message()->AddAllocated(nested);
+  }
+
+  for (int i = 0; i < 10; i++) {
+    const TestAllTypes::NestedMessage *orig_submessage =
+        &arena_message->repeated_nested_message(10 - 1 - i);  // last element
+    TestAllTypes::NestedMessage *released =
+        arena_message->mutable_repeated_nested_message()->ReleaseLast();
+    EXPECT_NE(released, orig_submessage);
+    EXPECT_EQ(42, released->bb());
+    delete released;
+  }
+
+  // Test UnsafeArenaReleaseLast().
+  for (int i = 0; i < 10; i++) {
+    TestAllTypes::NestedMessage* nested =
+        Arena::CreateMessage<TestAllTypes::NestedMessage>(&arena);
+    nested->set_bb(42);
+    arena_message->mutable_repeated_nested_message()->AddAllocated(nested);
+  }
+
+  for (int i = 0; i < 10; i++) {
+    const TestAllTypes::NestedMessage *orig_submessage =
+        &arena_message->repeated_nested_message(10 - 1 - i);  // last element
+    TestAllTypes::NestedMessage *released =
+        arena_message->mutable_repeated_nested_message()->
+        UnsafeArenaReleaseLast();
+    EXPECT_EQ(released, orig_submessage);
+    EXPECT_EQ(42, released->bb());
+    // no delete -- |released| is on the arena.
+  }
+
+  // Test string case as well. ReleaseLast() in this case must copy the string,
+  // even though it was originally heap-allocated and its pointer was simply
+  // appended to the repeated field's internal vector, because the string was
+  // placed on the arena's destructor list and cannot be removed from that list
+  // (so the arena permanently owns the original instance).
+  arena_message->Clear();
+  for (int i = 0; i < 10; i++) {
+    string* s = new string("Test");
+    arena_message->mutable_repeated_string()->AddAllocated(s);
+  }
+  for (int i = 0; i < 10; i++) {
+    const string* orig_element = &arena_message->repeated_string(10 - 1 - i);
+    string* released = arena_message->mutable_repeated_string()->ReleaseLast();
+    EXPECT_NE(released, orig_element);
+    EXPECT_EQ("Test", *released);
+    delete released;
+  }
+}
+
+TEST(ArenaTest, UnsafeArenaReleaseAdd) {
+  // Use unsafe_arena_release() and unsafe_arena_set_allocated() to transfer an
+  // arena-allocated string from one message to another.
+  Arena arena;
+  TestAllTypes* message1 = Arena::CreateMessage<TestAllTypes>(&arena);
+  TestAllTypes* message2 = Arena::CreateMessage<TestAllTypes>(&arena);
+  string* arena_string = Arena::Create<string>(&arena);
+  *arena_string = "Test content";
+
+  message1->unsafe_arena_set_allocated_optional_string(arena_string);
+  EXPECT_EQ(arena_string, message1->mutable_optional_string());
+  message2->unsafe_arena_set_allocated_optional_string(
+      message1->unsafe_arena_release_optional_string());
+  EXPECT_EQ(arena_string, message2->mutable_optional_string());
+}
+
+TEST(ArenaTest, UnsafeArenaAddAllocated) {
+  Arena arena;
+  TestAllTypes* message = Arena::CreateMessage<TestAllTypes>(&arena);
+  for (int i = 0; i < 10; i++) {
+    string* arena_string = Arena::Create<string>(&arena);
+    message->mutable_repeated_string()->UnsafeArenaAddAllocated(arena_string);
+    EXPECT_EQ(arena_string, message->mutable_repeated_string(i));
+  }
+}
+
+namespace {
+void TestSwapRepeatedField(Arena* arena1, Arena* arena2) {
+  // Test "safe" (copying) semantics for direct Swap() on RepeatedPtrField
+  // between arenas.
+  RepeatedPtrField<TestAllTypes> field1(arena1);
+  RepeatedPtrField<TestAllTypes> field2(arena2);
+  for (int i = 0; i < 10; i++) {
+    TestAllTypes* t = Arena::CreateMessage<TestAllTypes>(arena1);
+    t->set_optional_string("field1");
+    t->set_optional_int32(i);
+    if (arena1 != NULL) {
+      field1.UnsafeArenaAddAllocated(t);
+    } else {
+      field1.AddAllocated(t);
+    }
+  }
+  for (int i = 0; i < 5; i++) {
+    TestAllTypes* t = Arena::CreateMessage<TestAllTypes>(arena2);
+    t->set_optional_string("field2");
+    t->set_optional_int32(i);
+    if (arena2 != NULL) {
+      field2.UnsafeArenaAddAllocated(t);
+    } else {
+      field2.AddAllocated(t);
+    }
+  }
+  field1.Swap(&field2);
+  EXPECT_EQ(5, field1.size());
+  EXPECT_EQ(10, field2.size());
+  EXPECT_TRUE(string("field1") == field2.Get(0).optional_string());
+  EXPECT_TRUE(string("field2") == field1.Get(0).optional_string());
+  // Ensure that fields retained their original order:
+  for (int i = 0; i < field1.size(); i++) {
+    EXPECT_EQ(i, field1.Get(i).optional_int32());
+  }
+  for (int i = 0; i < field2.size(); i++) {
+    EXPECT_EQ(i, field2.Get(i).optional_int32());
+  }
+}
+}  // namespace
+
+TEST(ArenaTest, SwapRepeatedField) {
+  Arena arena;
+  TestSwapRepeatedField(&arena, &arena);
+}
+
+TEST(ArenaTest, SwapRepeatedFieldWithDifferentArenas) {
+  Arena arena1;
+  Arena arena2;
+  TestSwapRepeatedField(&arena1, &arena2);
+}
+
+TEST(ArenaTest, SwapRepeatedFieldWithNoArenaOnRightHandSide) {
+  Arena arena;
+  TestSwapRepeatedField(&arena, NULL);
+}
+
+TEST(ArenaTest, SwapRepeatedFieldWithNoArenaOnLeftHandSide) {
+  Arena arena;
+  TestSwapRepeatedField(NULL, &arena);
+}
+
+TEST(ArenaTest, ExtensionsOnArena) {
+  Arena arena;
+  // Ensure no leaks.
+  TestAllExtensions* message_ext =
+      Arena::CreateMessage<TestAllExtensions>(&arena);
+  message_ext->SetExtension(
+      protobuf_unittest::optional_int32_extension, 42);
+  message_ext->SetExtension(
+      protobuf_unittest::optional_string_extension, string("test"));
+  message_ext->MutableExtension(
+      protobuf_unittest::optional_nested_message_extension)->set_bb(42);
+}
+
+class NoHeapChecker {
+ public:
+  NoHeapChecker() {
+    capture_alloc.Hook();
+  }
+  ~NoHeapChecker() {
+    capture_alloc.Unhook();
+    EXPECT_EQ(0, capture_alloc.alloc_count());
+    EXPECT_EQ(0, capture_alloc.free_count());
+  }
+ private:
+  class NewDeleteCapture {
+   public:
+    // TOOD(xiaofeng): Implement this for opensource protobuf.
+    void Hook() {}
+    void Unhook() {}
+    int alloc_count() { return 0; }
+    int free_count() { return 0; }
+  } capture_alloc;
+};
+
+TEST(ArenaTest, RepeatedFieldOnArena) {
+  // Preallocate an initial arena block to avoid mallocs during hooked region.
+  std::vector<char> arena_block(1024 * 1024);
+  ArenaOptions options;
+  options.initial_block = arena_block.data();
+  options.initial_block_size = arena_block.size();
+  Arena arena(options);
+
+  {
+    NoHeapChecker no_heap;
+
+    // Fill some repeated fields on the arena to test for leaks. Also verify no
+    // memory allocations.
+    RepeatedField<int32> repeated_int32(&arena);
+    RepeatedPtrField<TestAllTypes> repeated_message(&arena);
+    for (int i = 0; i < 100; i++) {
+      repeated_int32.Add(42);
+      repeated_message.Add()->set_optional_int32(42);
+      EXPECT_EQ(&arena, repeated_message.Get(0).GetArena());
+      const TestAllTypes* msg_in_repeated_field = &repeated_message.Get(0);
+      TestAllTypes* msg = repeated_message.UnsafeArenaReleaseLast();
+      EXPECT_EQ(msg_in_repeated_field, msg);
+    }
+
+    // UnsafeArenaExtractSubrange (i) should not leak and (ii) should return
+    // on-arena pointers.
+    for (int i = 0; i < 10; i++) {
+      repeated_message.Add()->set_optional_int32(42);
+    }
+    TestAllTypes* extracted_messages[5];
+    repeated_message.UnsafeArenaExtractSubrange(0, 5, extracted_messages);
+    EXPECT_EQ(&arena, repeated_message.Get(0).GetArena());
+    EXPECT_EQ(5, repeated_message.size());
+  }
+
+  // Now, outside the scope of the NoHeapChecker, test ExtractSubrange's copying
+  // semantics.
+  {
+    RepeatedPtrField<TestAllTypes> repeated_message(&arena);
+    for (int i = 0; i < 100; i++) {
+      repeated_message.Add()->set_optional_int32(42);
+    }
+
+    TestAllTypes* extracted_messages[5];
+    // ExtractSubrange should copy to the heap.
+    repeated_message.ExtractSubrange(0, 5, extracted_messages);
+    EXPECT_EQ(NULL, extracted_messages[0]->GetArena());
+    // We need to free the heap-allocated messages to prevent a leak.
+    for (int i = 0; i < 5; i++) {
+      delete extracted_messages[i];
+      extracted_messages[i] = NULL;
+    }
+  }
+
+  // Now check that we can create RepeatedFields/RepeatedPtrFields themselves on
+  // the arena. They have the necessary type traits so that they can behave like
+  // messages in this way. This is useful for higher-level generic templated
+  // code that may allocate messages or repeated fields of messages on an arena.
+  {
+    RepeatedPtrField<TestAllTypes>* repeated_ptr_on_arena =
+        Arena::CreateMessage< RepeatedPtrField<TestAllTypes> >(&arena);
+    for (int i = 0; i < 10; i++) {
+      // Add some elements and let the leak-checker ensure that everything is
+      // freed.
+      repeated_ptr_on_arena->Add();
+    }
+
+    RepeatedField<int>* repeated_int_on_arena =
+        Arena::CreateMessage< RepeatedField<int> >(&arena);
+    for (int i = 0; i < 100; i++) {
+      repeated_int_on_arena->Add(i);
+    }
+
+  }
+
+  arena.Reset();
+}
+
+
+TEST(ArenaTest, MutableMessageReflection) {
+  Arena arena;
+  TestAllTypes* message = Arena::CreateMessage<TestAllTypes>(&arena);
+  const Reflection* r = message->GetReflection();
+  const Descriptor* d = message->GetDescriptor();
+  const FieldDescriptor* field = d->FindFieldByName("optional_nested_message");
+  TestAllTypes::NestedMessage* submessage =
+      dynamic_cast<TestAllTypes::NestedMessage*>(
+          r->MutableMessage(message, field));
+  TestAllTypes::NestedMessage* submessage_expected =
+      message->mutable_optional_nested_message();
+
+  EXPECT_EQ(submessage_expected, submessage);
+  EXPECT_EQ(&arena, submessage->GetArena());
+
+  const FieldDescriptor* oneof_field = d->FindFieldByName("oneof_nested_message");
+  submessage = dynamic_cast<TestAllTypes::NestedMessage*>(
+      r->MutableMessage(message, oneof_field));
+  submessage_expected = message->mutable_oneof_nested_message();
+
+  EXPECT_EQ(submessage_expected, submessage);
+  EXPECT_EQ(&arena, submessage->GetArena());
+}
+
+
+namespace {
+
+void FillArenaAwareFields(TestAllTypes* message) {
+  string test_string = "hello world";
+  message->set_optional_int32(42);
+  message->set_optional_string(test_string);
+  message->set_optional_bytes(test_string);
+  message->mutable_optional_nested_message()->set_bb(42);
+
+  message->set_oneof_uint32(42);
+  message->mutable_oneof_nested_message()->set_bb(42);
+  message->set_oneof_string(test_string);
+  message->set_oneof_bytes(test_string);
+
+  message->add_repeated_int32(42);
+  // No repeated string: not yet arena-aware.
+  message->add_repeated_nested_message()->set_bb(42);
+  message->mutable_optional_lazy_message()->set_bb(42);
+}
+
+}
+
+// Test: no allocations occur on heap while touching all supported field types.
+TEST(ArenaTest, NoHeapAllocationsTest) {
+  // Allocate a large initial block to avoid mallocs during hooked test.
+  std::vector<char> arena_block(128 * 1024);
+  ArenaOptions options;
+  options.initial_block = arena_block.data();
+  options.initial_block_size = arena_block.size();
+  Arena arena(options);
+
+  {
+
+    TestAllTypes* message = Arena::CreateMessage<TestAllTypes>(&arena);
+    FillArenaAwareFields(message);
+  }
+
+  arena.Reset();
+}
+
+
+// Test construction on an arena via generic MessageLite interface. We should be
+// able to successfully deserialize on the arena without incurring heap
+// allocations, i.e., everything should still be arena-allocation-aware.
+TEST(ArenaTest, MessageLiteOnArena) {
+  std::vector<char> arena_block(128 * 1024);
+  ArenaOptions options;
+  options.initial_block = arena_block.data();
+  options.initial_block_size = arena_block.size();
+  Arena arena(options);
+  const google::protobuf::MessageLite* prototype = dynamic_cast<
+      const google::protobuf::MessageLite*>(&TestAllTypes::default_instance());
+
+  TestAllTypes initial_message;
+  FillArenaAwareFields(&initial_message);
+  string serialized;
+  initial_message.SerializeToString(&serialized);
+
+  {
+
+    google::protobuf::MessageLite* generic_message = prototype->New(&arena);
+    EXPECT_TRUE(generic_message != NULL);
+    EXPECT_EQ(&arena, generic_message->GetArena());
+    EXPECT_TRUE(generic_message->ParseFromString(serialized));
+    TestAllTypes* deserialized = dynamic_cast<TestAllTypes*>(generic_message);
+    EXPECT_TRUE(deserialized != NULL);
+    EXPECT_EQ(42, deserialized->optional_int32());
+  }
+
+  arena.Reset();
+}
+
+
+// RepeatedField should support non-POD types, and invoke constructors and
+// destructors appropriately, because it's used this way by lots of other code
+// (even if this was not its original intent).
+TEST(ArenaTest, RepeatedFieldWithNonPODType) {
+  {
+    RepeatedField<string> field_on_heap;
+    for (int i = 0; i < 100; i++) {
+      *field_on_heap.Add() = "test string long enough to exceed inline buffer";
+    }
+  }
+  {
+    Arena arena;
+    RepeatedField<string> field_on_arena(&arena);
+    for (int i = 0; i < 100; i++) {
+      *field_on_arena.Add() = "test string long enough to exceed inline buffer";
+    }
+  }
+}
+
+TEST(ArenaTest, SpaceUsed) {
+  ArenaOptions options;
+  options.start_block_size = 256;
+  options.max_block_size = 8192;
+  Arena arena_1(options);
+  EXPECT_EQ(0, arena_1.SpaceUsed());
+  EXPECT_EQ(0, arena_1.Reset());
+  ::google::protobuf::Arena::CreateArray<char>(&arena_1, 320);
+  // Arena will allocate slightly more than 320 for the block headers.
+  EXPECT_LE(320, arena_1.SpaceUsed());
+  EXPECT_LE(320, arena_1.Reset());
+
+  // Test with initial block.
+  std::vector<char> arena_block(1024);
+  options.initial_block = arena_block.data();
+  options.initial_block_size = arena_block.size();
+  Arena arena_2(options);
+  EXPECT_EQ(1024, arena_2.SpaceUsed());
+  EXPECT_EQ(1024, arena_2.Reset());
+  ::google::protobuf::Arena::CreateArray<char>(&arena_2, 55);
+  EXPECT_EQ(1024, arena_2.SpaceUsed());
+  EXPECT_EQ(1024, arena_2.Reset());
+
+  // Reset options to test doubling policy explicitly.
+  options.initial_block = NULL;
+  options.initial_block_size = 0;
+  Arena arena_3(options);
+  ::google::protobuf::Arena::CreateArray<char>(&arena_3, 190);
+  EXPECT_EQ(256, arena_3.SpaceUsed());
+  ::google::protobuf::Arena::CreateArray<char>(&arena_3, 70);
+  EXPECT_EQ(256 + 512, arena_3.SpaceUsed());
+  EXPECT_EQ(256 + 512, arena_3.Reset());
+}
+
+TEST(ArenaTest, Alignment) {
+  ::google::protobuf::Arena arena;
+  for (int i = 0; i < 200; i++) {
+    void* p = ::google::protobuf::Arena::CreateArray<char>(&arena, i);
+    GOOGLE_CHECK_EQ(reinterpret_cast<uintptr_t>(p) % 8, 0) << i << ": " << p;
+  }
+}
+
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/arenastring.cc b/src/google/protobuf/arenastring.cc
new file mode 100644
index 00000000..7f33a0c8
--- /dev/null
+++ b/src/google/protobuf/arenastring.cc
@@ -0,0 +1,43 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// The ArenaString implementation is not included in the open-source release. Do
+// not include this file in the distribution.
+
+#include <google/protobuf/arenastring.h>
+
+namespace google {
+namespace protobuf {
+namespace internal {
+
+
+}  // namespace internal
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/arenastring.h b/src/google/protobuf/arenastring.h
new file mode 100755
index 00000000..5f02ef0d
--- /dev/null
+++ b/src/google/protobuf/arenastring.h
@@ -0,0 +1,314 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_ARENASTRING_H__
+#define GOOGLE_PROTOBUF_ARENASTRING_H__
+
+#include <stdint.h>
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/fastmem.h>
+
+#include <google/protobuf/arena.h>
+#include <google/protobuf/generated_message_util.h>
+
+
+
+// This is the implementation of arena string fields written for the open-source
+// release. The ArenaStringPtr struct below is an internal implementation class
+// and *should not be used* by user code. It is used to collect string
+// operations together into one place and abstract away the underlying
+// string-field pointer representation, so that (for example) an alternate
+// implementation that knew more about ::std::string's internals could integrate more
+// closely with the arena allocator.
+
+namespace google {
+namespace protobuf {
+namespace internal {
+
+struct ArenaStringPtr {
+  inline void Set(const ::std::string* default_value,
+                  const ::std::string& value, ::google::protobuf::Arena* arena) {
+    if (ptr_ == default_value) {
+      CreateInstance(arena, &value);
+    } else {
+      *ptr_ = value;
+    }
+  }
+
+  // Basic accessors.
+  inline const ::std::string& Get(const ::std::string* default_value) const {
+    return *ptr_;
+  }
+
+  inline ::std::string* Mutable(const ::std::string* default_value,
+                           ::google::protobuf::Arena* arena) {
+    if (ptr_ == default_value) {
+      CreateInstance(arena, default_value);
+    }
+    return ptr_;
+  }
+
+  // Release returns a ::std::string* instance that is heap-allocated and is not
+  // Own()'d by any arena. If the field was not set, it returns NULL. The caller
+  // retains ownership. Clears this field back to NULL state. Used to implement
+  // release_<field>() methods on generated classes.
+  inline ::std::string* Release(const ::std::string* default_value,
+                           ::google::protobuf::Arena* arena) {
+    if (ptr_ == default_value) {
+      return NULL;
+    }
+    ::std::string* released = NULL;
+    if (arena != NULL) {
+      // ptr_ is owned by the arena -- we need to return a copy.
+      released = new ::std::string(*ptr_);
+    } else {
+      released = ptr_;
+    }
+    ptr_ = const_cast< ::std::string* >(default_value);
+    return released;
+  }
+
+  // UnsafeArenaRelease returns a ::std::string*, but it may be arena-owned (i.e.
+  // have its destructor already registered) if arena != NULL. If the field was
+  // not set, this returns NULL. This method clears this field back to NULL
+  // state. Used to implement unsafe_arena_release_<field>() methods on
+  // generated classes.
+  inline ::std::string* UnsafeArenaRelease(const ::std::string* default_value,
+                                      ::google::protobuf::Arena* arena) {
+    if (ptr_ == default_value) {
+      return NULL;
+    }
+    ::std::string* released = ptr_;
+    ptr_ = const_cast< ::std::string* >(default_value);
+    return released;
+  }
+
+  // Takes a string that is heap-allocated, and takes ownership. The string's
+  // destructor is registered with the arena. Used to implement
+  // set_allocated_<field> in generated classes.
+  inline void SetAllocated(const ::std::string* default_value,
+                           ::std::string* value, ::google::protobuf::Arena* arena) {
+    if (arena == NULL && ptr_ != default_value) {
+      Destroy(default_value, arena);
+    }
+    if (value != NULL) {
+      ptr_ = value;
+      if (arena != NULL) {
+        arena->Own(value);
+      }
+    } else {
+      ptr_ = const_cast< ::std::string* >(default_value);
+    }
+  }
+
+  // Takes a string that has lifetime equal to the arena's lifetime. The arena
+  // must be non-null. It is safe only to pass this method a value returned by
+  // UnsafeArenaRelease() on another field of a message in the same arena. Used
+  // to implement unsafe_arena_set_allocated_<field> in generated classes.
+  inline void UnsafeArenaSetAllocated(const ::std::string* default_value,
+                                      ::std::string* value, ::google::protobuf::Arena* arena) {
+    if (value != NULL) {
+      ptr_ = value;
+    } else {
+      ptr_ = const_cast< ::std::string* >(default_value);
+    }
+  }
+
+  // Swaps internal pointers. Arena-safety semantics: this is guarded by the
+  // logic in Swap()/UnsafeArenaSwap() at the message level, so this method is
+  // 'unsafe' if called directly.
+  inline void Swap(ArenaStringPtr* other) GOOGLE_ATTRIBUTE_ALWAYS_INLINE {
+    std::swap(ptr_, other->ptr_);
+  }
+
+  // Frees storage (if not on an arena) and sets field to default value.
+  inline void Destroy(const ::std::string* default_value,
+                      ::google::protobuf::Arena* arena) {
+    if (arena == NULL && ptr_ != default_value) {
+      delete ptr_;
+    }
+    ptr_ = const_cast< ::std::string* >(default_value);
+  }
+
+  // Clears content, but keeps allocated string if arena != NULL, to avoid the
+  // overhead of heap operations. After this returns, the content (as seen by
+  // the user) will always be the empty string. Assumes that |default_value|
+  // is an empty string.
+  inline void ClearToEmpty(const ::std::string* default_value,
+                           ::google::protobuf::Arena* arena) {
+    if (ptr_ == default_value) {
+      // Already set to default (which is empty) -- do nothing.
+    } else {
+      ptr_->clear();
+    }
+  }
+
+  // Clears content, but keeps allocated string if arena != NULL, to avoid the
+  // overhead of heap operations. After this returns, the content (as seen by
+  // the user) will always be equal to |default_value|.
+  inline void ClearToDefault(const ::std::string* default_value,
+                             ::google::protobuf::Arena* arena) {
+    if (ptr_ == default_value) {
+      // Already set to default -- do nothing.
+    } else {
+      // Have another allocated string -- rather than throwing this away and
+      // resetting ptr_ to the canonical default string instance, we just reuse
+      // this instance.
+      *ptr_ = *default_value;
+    }
+  }
+
+  // Called from generated code / reflection runtime only. Resets value to point
+  // to a default string pointer, with the semantics that this ArenaStringPtr
+  // does not own the pointed-to memory. Disregards initial value of ptr_ (so
+  // this is the *ONLY* safe method to call after construction or when
+  // reinitializing after becoming the active field in a oneof union).
+  inline void UnsafeSetDefault(const ::std::string* default_value) {
+    // Casting away 'const' is safe here: accessors ensure that ptr_ is only
+    // returned as a const if it is equal to default_value.
+    ptr_ = const_cast< ::std::string* >(default_value);
+  }
+
+  // The 'NoArena' variants of methods below assume arena == NULL and are
+  // optimized to provide very little overhead relative to a raw string pointer
+  // (while still being in-memory compatible with other code that assumes
+  // ArenaStringPtr). Note the invariant that a class instance that has only
+  // ever been mutated by NoArena methods must *only* be in the String state
+  // (i.e., tag bits are not used), *NEVER* ArenaString. This allows all
+  // tagged-pointer manipulations to be avoided.
+  inline void SetNoArena(const ::std::string* default_value,
+                         const ::std::string& value) {
+    if (ptr_ == default_value) {
+      CreateInstanceNoArena(&value);
+    } else {
+      *ptr_ = value;
+    }
+  }
+
+  inline const ::std::string& GetNoArena(const ::std::string* default_value) const {
+    return *ptr_;
+  }
+
+  inline ::std::string* MutableNoArena(const ::std::string* default_value) {
+    if (ptr_ == default_value) {
+      CreateInstanceNoArena(default_value);
+    }
+    return ptr_;
+  }
+
+  inline ::std::string* ReleaseNoArena(const ::std::string* default_value) {
+    if (ptr_ == default_value) {
+      return NULL;
+    } else {
+      ::std::string* released = ptr_;
+      ptr_ = const_cast< ::std::string* >(default_value);
+      return released;
+    }
+  }
+
+  inline void SetAllocatedNoArena(const ::std::string* default_value,
+                                  ::std::string* value) {
+    if (ptr_ != default_value) {
+      delete ptr_;
+    }
+    if (value != NULL) {
+      ptr_ = value;
+    } else {
+      ptr_ = const_cast< ::std::string* >(default_value);
+    }
+  }
+
+  inline void DestroyNoArena(const ::std::string* default_value) {
+    if (ptr_ != default_value) {
+      delete ptr_;
+    }
+    ptr_ = NULL;
+  }
+
+  inline void ClearToEmptyNoArena(const ::std::string* default_value) {
+    if (ptr_ == default_value) {
+      // Nothing: already equal to default (which is the empty string).
+    } else {
+      ptr_->clear();
+    }
+  }
+
+  inline void ClearToDefaultNoArena(const ::std::string* default_value) {
+    if (ptr_ == default_value) {
+      // Nothing: already set to default.
+    } else {
+      // Reuse existing allocated instance.
+      *ptr_ = *default_value;
+    }
+  }
+
+  // Internal accessor used only at parse time to provide direct access to the
+  // raw pointer from the shared parse routine (in the non-arenas case). The
+  // parse routine does the string allocation in order to save code size in the
+  // generated parsing code.
+  inline ::std::string** UnsafeRawStringPointer() {
+    return &ptr_;
+  }
+
+ private:
+  ::std::string* ptr_;
+
+  inline void CreateInstance(::google::protobuf::Arena* arena,
+                             const ::std::string* initial_value)
+      GOOGLE_ATTRIBUTE_NOINLINE {
+    // Assumes ptr_ is not NULL.
+    if (initial_value != NULL) {
+      ptr_ = new ::std::string(*initial_value);
+    } else {
+      ptr_ = new ::std::string();
+    }
+    if (arena != NULL) {
+      arena->Own(ptr_);
+    }
+  }
+  inline void CreateInstanceNoArena(const ::std::string* initial_value)
+      GOOGLE_ATTRIBUTE_NOINLINE {
+    if (initial_value != NULL) {
+      ptr_ = new ::std::string(*initial_value);
+    } else {
+      ptr_ = new ::std::string();
+    }
+  }
+};
+
+}  // namespace internal
+}  // namespace protobuf
+
+
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_ARENASTRING_H__
diff --git a/src/google/protobuf/arenastring_unittest.cc b/src/google/protobuf/arenastring_unittest.cc
new file mode 100644
index 00000000..8ebd4b9c
--- /dev/null
+++ b/src/google/protobuf/arenastring_unittest.cc
@@ -0,0 +1,112 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// arenastring_unittest.cc is not open-sourced. Do not include in open-source
+// distribution.
+
+// Based on mvels@'s frankenstring.
+
+#include <google/protobuf/arenastring.h>
+
+#include <string>
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <cstdlib>
+
+#include <google/protobuf/stubs/common.h>
+#include <gtest/gtest.h>
+
+namespace google {
+using google::protobuf::internal::ArenaString;
+using google::protobuf::internal::ArenaStringPtr;
+
+namespace protobuf {
+
+
+static string WrapString(const char* value) {
+  return value;
+}
+
+// Test ArenaStringPtr with arena == NULL.
+TEST(ArenaStringPtrTest, ArenaStringPtrOnHeap) {
+  ArenaStringPtr field;
+  ::std::string default_value = "default";
+  field.UnsafeSetDefault(&default_value);
+  EXPECT_EQ(string("default"), field.Get(&default_value));
+  field.Set(&default_value, WrapString("Test short"), NULL);
+  EXPECT_EQ(string("Test short"), field.Get(&default_value));
+  field.Set(&default_value, WrapString("Test long long long long value"), NULL);
+  EXPECT_EQ(string("Test long long long long value"), field.Get(&default_value));
+  field.Set(&default_value, string(""), NULL);
+  field.Destroy(&default_value, NULL);
+
+  ArenaStringPtr field2;
+  field2.UnsafeSetDefault(&default_value);
+  ::std::string* mut = field2.Mutable(&default_value, NULL);
+  EXPECT_EQ(mut, field2.Mutable(&default_value, NULL));
+  EXPECT_EQ(mut, &field2.Get(&default_value));
+  EXPECT_NE(&default_value, mut);
+  EXPECT_EQ(string("default"), *mut);
+  *mut = "Test long long long long value";  // ensure string allocates storage
+  EXPECT_EQ(string("Test long long long long value"), field2.Get(&default_value));
+  field2.Destroy(&default_value, NULL);
+}
+
+TEST(ArenaStringPtrTest, ArenaStringPtrOnArena) {
+  google::protobuf::Arena arena;
+  ArenaStringPtr field;
+  ::std::string default_value = "default";
+  field.UnsafeSetDefault(&default_value);
+  EXPECT_EQ(string("default"), field.Get(&default_value));
+  field.Set(&default_value, WrapString("Test short"), &arena);
+  EXPECT_EQ(string("Test short"), field.Get(&default_value));
+  field.Set(&default_value, WrapString("Test long long long long value"), &arena);
+  EXPECT_EQ(string("Test long long long long value"),
+            field.Get(&default_value));
+  field.Set(&default_value, string(""), &arena);
+  field.Destroy(&default_value, &arena);
+
+  ArenaStringPtr field2;
+  field2.UnsafeSetDefault(&default_value);
+  ::std::string* mut = field2.Mutable(&default_value, &arena);
+  EXPECT_EQ(mut, field2.Mutable(&default_value, &arena));
+  EXPECT_EQ(mut, &field2.Get(&default_value));
+  EXPECT_NE(&default_value, mut);
+  EXPECT_EQ(string("default"), *mut);
+  *mut = "Test long long long long value";  // ensure string allocates storage
+  EXPECT_EQ(string("Test long long long long value"),
+            field2.Get(&default_value));
+  field2.Destroy(&default_value, &arena);
+}
+
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/compiler/command_line_interface.cc b/src/google/protobuf/compiler/command_line_interface.cc
index f9f27bd8..fc7df414 100644
--- a/src/google/protobuf/compiler/command_line_interface.cc
+++ b/src/google/protobuf/compiler/command_line_interface.cc
@@ -50,6 +50,9 @@
 
 #include <google/protobuf/stubs/hash.h>
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 
 #include <google/protobuf/stubs/common.h>
 #include <google/protobuf/stubs/stringprintf.h>
diff --git a/src/google/protobuf/compiler/command_line_interface_unittest.cc b/src/google/protobuf/compiler/command_line_interface_unittest.cc
index 5bc1fea9..6e1a204d 100644
--- a/src/google/protobuf/compiler/command_line_interface_unittest.cc
+++ b/src/google/protobuf/compiler/command_line_interface_unittest.cc
@@ -41,6 +41,9 @@
 #include <unistd.h>
 #endif
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <vector>
 
 #include <google/protobuf/descriptor.pb.h>
@@ -48,6 +51,7 @@
 #include <google/protobuf/io/zero_copy_stream.h>
 #include <google/protobuf/compiler/command_line_interface.h>
 #include <google/protobuf/compiler/code_generator.h>
+#include <google/protobuf/testing/file.h>
 #include <google/protobuf/compiler/mock_code_generator.h>
 #include <google/protobuf/compiler/subprocess.h>
 #include <google/protobuf/io/printer.h>
@@ -59,6 +63,7 @@
 #include <google/protobuf/testing/googletest.h>
 #include <gtest/gtest.h>
 
+
 namespace google {
 namespace protobuf {
 namespace compiler {
@@ -77,6 +82,10 @@ namespace compiler {
 
 namespace {
 
+bool FileExists(const string& path) {
+  return File::Exists(path);
+}
+
 class CommandLineInterfaceTest : public testing::Test {
  protected:
   virtual void SetUp();
@@ -226,7 +235,7 @@ void CommandLineInterfaceTest::SetUp() {
 
   // If the temp directory already exists, it must be left over from a
   // previous run.  Delete it.
-  if (File::Exists(temp_directory_)) {
+  if (FileExists(temp_directory_)) {
     File::DeleteRecursively(temp_directory_, NULL, NULL);
   }
 
@@ -335,7 +344,7 @@ void CommandLineInterfaceTest::CreateTempFile(
   string::size_type slash_pos = name.find_last_of('/');
   if (slash_pos != string::npos) {
     string dir = name.substr(0, slash_pos);
-    if (!File::Exists(temp_directory_ + "/" + dir)) {
+    if (!FileExists(temp_directory_ + "/" + dir)) {
       GOOGLE_CHECK_OK(File::RecursivelyCreateDir(temp_directory_ + "/" + dir,
                                           0777));
     }
diff --git a/src/google/protobuf/compiler/cpp/cpp_enum.cc b/src/google/protobuf/compiler/cpp/cpp_enum.cc
index c31cb5b3..32d5516e 100644
--- a/src/google/protobuf/compiler/cpp/cpp_enum.cc
+++ b/src/google/protobuf/compiler/cpp/cpp_enum.cc
@@ -101,6 +101,15 @@ void EnumGenerator::GenerateDefinition(io::Printer* printer) {
     }
   }
 
+  if (HasPreservingUnknownEnumSemantics(descriptor_->file())) {
+    // For new enum semantics: generate min and max sentinel values equal to
+    // INT32_MIN and INT32_MAX
+    if (descriptor_->value_count() > 0) printer->Print(",\n");
+    printer->Print(vars,
+        "$classname$_$prefix$INT_MIN_SENTINEL_DO_NOT_USE_ = INT32_MIN,\n"
+        "$classname$_$prefix$INT_MAX_SENTINEL_DO_NOT_USE_ = INT32_MAX");
+  }
+
   printer->Outdent();
   printer->Print("\n};\n");
 
diff --git a/src/google/protobuf/compiler/cpp/cpp_enum_field.cc b/src/google/protobuf/compiler/cpp/cpp_enum_field.cc
index 20b18ade..17926135 100644
--- a/src/google/protobuf/compiler/cpp/cpp_enum_field.cc
+++ b/src/google/protobuf/compiler/cpp/cpp_enum_field.cc
@@ -87,9 +87,13 @@ GenerateInlineAccessorDefinitions(io::Printer* printer) const {
     "  // @@protoc_insertion_point(field_get:$full_name$)\n"
     "  return static_cast< $type$ >($name$_);\n"
     "}\n"
-    "inline void $classname$::set_$name$($type$ value) {\n"
-    "  assert($type$_IsValid(value));\n"
-    "  set_has_$name$();\n"
+    "inline void $classname$::set_$name$($type$ value) {\n");
+  if (!HasPreservingUnknownEnumSemantics(descriptor_->file())) {
+    printer->Print(variables_,
+    "  assert($type$_IsValid(value));\n");
+  }
+  printer->Print(variables_,
+    "  $set_hasbit$\n"
     "  $name$_ = value;\n"
     "  // @@protoc_insertion_point(field_set:$full_name$)\n"
     "}\n");
@@ -121,21 +125,27 @@ GenerateMergeFromCodedStream(io::Printer* printer) const {
     "int value;\n"
     "DO_((::google::protobuf::internal::WireFormatLite::ReadPrimitive<\n"
     "         int, ::google::protobuf::internal::WireFormatLite::TYPE_ENUM>(\n"
-    "       input, &value)));\n"
-    "if ($type$_IsValid(value)) {\n"
-    "  set_$name$(static_cast< $type$ >(value));\n");
-  if (UseUnknownFieldSet(descriptor_->file())) {
+    "       input, &value)));\n");
+  if (HasPreservingUnknownEnumSemantics(descriptor_->file())) {
     printer->Print(variables_,
-      "} else {\n"
-      "  mutable_unknown_fields()->AddVarint($number$, value);\n");
+      "set_$name$(static_cast< $type$ >(value));\n");
   } else {
-    printer->Print(
-      "} else {\n"
-      "  unknown_fields_stream.WriteVarint32(tag);\n"
-      "  unknown_fields_stream.WriteVarint32(value);\n");
+    printer->Print(variables_,
+      "if ($type$_IsValid(value)) {\n"
+      "  set_$name$(static_cast< $type$ >(value));\n");
+    if (UseUnknownFieldSet(descriptor_->file())) {
+      printer->Print(variables_,
+        "} else {\n"
+        "  mutable_unknown_fields()->AddVarint($number$, value);\n");
+    } else {
+      printer->Print(
+        "} else {\n"
+        "  unknown_fields_stream.WriteVarint32(tag);\n"
+        "  unknown_fields_stream.WriteVarint32(value);\n");
+    }
+    printer->Print(variables_,
+      "}\n");
   }
-  printer->Print(variables_,
-    "}\n");
 }
 
 void EnumFieldGenerator::
@@ -174,18 +184,24 @@ void EnumOneofFieldGenerator::
 GenerateInlineAccessorDefinitions(io::Printer* printer) const {
   printer->Print(variables_,
     "inline $type$ $classname$::$name$() const {\n"
+    "  // @@protoc_insertion_point(field_get:$full_name$)\n"
     "  if (has_$name$()) {\n"
     "    return static_cast< $type$ >($oneof_prefix$$name$_);\n"
     "  }\n"
     "  return static_cast< $type$ >($default$);\n"
     "}\n"
-    "inline void $classname$::set_$name$($type$ value) {\n"
-    "  assert($type$_IsValid(value));\n"
+    "inline void $classname$::set_$name$($type$ value) {\n");
+  if (!HasPreservingUnknownEnumSemantics(descriptor_->file())) {
+    printer->Print(variables_,
+    "  assert($type$_IsValid(value));\n");
+  }
+  printer->Print(variables_,
     "  if (!has_$name$()) {\n"
     "    clear_$oneof_name$();\n"
     "    set_has_$name$();\n"
     "  }\n"
     "  $oneof_prefix$$name$_ = value;\n"
+    "  // @@protoc_insertion_point(field_set:$full_name$)\n"
     "}\n");
 }
 
@@ -245,13 +261,21 @@ GenerateInlineAccessorDefinitions(io::Printer* printer) const {
     "  // @@protoc_insertion_point(field_get:$full_name$)\n"
     "  return static_cast< $type$ >($name$_.Get(index));\n"
     "}\n"
-    "inline void $classname$::set_$name$(int index, $type$ value) {\n"
-    "  assert($type$_IsValid(value));\n"
+    "inline void $classname$::set_$name$(int index, $type$ value) {\n");
+  if (!HasPreservingUnknownEnumSemantics(descriptor_->file())) {
+    printer->Print(variables_,
+    "  assert($type$_IsValid(value));\n");
+  }
+  printer->Print(variables_,
     "  $name$_.Set(index, value);\n"
     "  // @@protoc_insertion_point(field_set:$full_name$)\n"
     "}\n"
-    "inline void $classname$::add_$name$($type$ value) {\n"
-    "  assert($type$_IsValid(value));\n"
+    "inline void $classname$::add_$name$($type$ value) {\n");
+  if (!HasPreservingUnknownEnumSemantics(descriptor_->file())) {
+    printer->Print(variables_,
+    "  assert($type$_IsValid(value));\n");
+  }
+  printer->Print(variables_,
     "  $name$_.Add(value);\n"
     "  // @@protoc_insertion_point(field_add:$full_name$)\n"
     "}\n");
@@ -280,7 +304,7 @@ GenerateMergingCode(io::Printer* printer) const {
 
 void RepeatedEnumFieldGenerator::
 GenerateSwappingCode(io::Printer* printer) const {
-  printer->Print(variables_, "$name$_.Swap(&other->$name$_);\n");
+  printer->Print(variables_, "$name$_.UnsafeArenaSwap(&other->$name$_);\n");
 }
 
 void RepeatedEnumFieldGenerator::
@@ -295,20 +319,26 @@ GenerateMergeFromCodedStream(io::Printer* printer) const {
     "int value;\n"
     "DO_((::google::protobuf::internal::WireFormatLite::ReadPrimitive<\n"
     "         int, ::google::protobuf::internal::WireFormatLite::TYPE_ENUM>(\n"
-    "       input, &value)));\n"
-    "if ($type$_IsValid(value)) {\n"
-    "  add_$name$(static_cast< $type$ >(value));\n");
-  if (UseUnknownFieldSet(descriptor_->file())) {
+    "       input, &value)));\n");
+  if (HasPreservingUnknownEnumSemantics(descriptor_->file())) {
     printer->Print(variables_,
-      "} else {\n"
-      "  mutable_unknown_fields()->AddVarint($number$, value);\n");
+      "add_$name$(static_cast< $type$ >(value));\n");
   } else {
-    printer->Print(
-      "} else {\n"
-      "  unknown_fields_stream.WriteVarint32(tag);\n"
-      "  unknown_fields_stream.WriteVarint32(value);\n");
+    printer->Print(variables_,
+      "if ($type$_IsValid(value)) {\n"
+      "  add_$name$(static_cast< $type$ >(value));\n");
+    if (UseUnknownFieldSet(descriptor_->file())) {
+      printer->Print(variables_,
+        "} else {\n"
+        "  mutable_unknown_fields()->AddVarint($number$, value);\n");
+    } else {
+      printer->Print(
+        "} else {\n"
+        "  unknown_fields_stream.WriteVarint32(tag);\n"
+        "  unknown_fields_stream.WriteVarint32(value);\n");
+    }
+    printer->Print("}\n");
   }
-  printer->Print("}\n");
 }
 
 void RepeatedEnumFieldGenerator::
@@ -318,8 +348,15 @@ GenerateMergeFromCodedStreamWithPacking(io::Printer* printer) const {
     // rarely be executed.
     printer->Print(variables_,
       "DO_((::google::protobuf::internal::WireFormatLite::ReadPackedEnumNoInline(\n"
-      "       input,\n"
-      "       &$type$_IsValid,\n"
+      "       input,\n");
+    if (HasPreservingUnknownEnumSemantics(descriptor_->file())) {
+      printer->Print(variables_,
+      "       NULL,\n");
+    } else {
+      printer->Print(variables_,
+      "       &$type$_IsValid,\n");
+    }
+    printer->Print(variables_,
       "       this->mutable_$name$())));\n");
   } else {
     printer->Print(variables_,
@@ -331,10 +368,17 @@ GenerateMergeFromCodedStreamWithPacking(io::Printer* printer) const {
       "  int value;\n"
       "  DO_((::google::protobuf::internal::WireFormatLite::ReadPrimitive<\n"
       "         int, ::google::protobuf::internal::WireFormatLite::TYPE_ENUM>(\n"
-      "       input, &value)));\n"
+      "       input, &value)));\n");
+    if (HasPreservingUnknownEnumSemantics(descriptor_->file())) {
+      printer->Print(variables_,
+      "  add_$name$(static_cast< $type$ >(value));\n");
+    } else {
+      printer->Print(variables_,
       "  if ($type$_IsValid(value)) {\n"
       "    add_$name$(static_cast< $type$ >(value));\n"
-      "  }\n"
+      "  }\n");
+    }
+    printer->Print(variables_,
       "}\n"
       "input->PopLimit(limit);\n");
   }
diff --git a/src/google/protobuf/compiler/cpp/cpp_field.cc b/src/google/protobuf/compiler/cpp/cpp_field.cc
index 1e9a40ac..85838ac3 100644
--- a/src/google/protobuf/compiler/cpp/cpp_field.cc
+++ b/src/google/protobuf/compiler/cpp/cpp_field.cc
@@ -34,6 +34,9 @@
 
 #include <google/protobuf/compiler/cpp/cpp_field.h>
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 
 #include <google/protobuf/compiler/cpp/cpp_helpers.h>
 #include <google/protobuf/compiler/cpp/cpp_primitive_field.h>
@@ -68,6 +71,20 @@ void SetCommonFieldVariables(const FieldDescriptor* descriptor,
       ? " PROTOBUF_DEPRECATED" : "";
 
   (*variables)["cppget"] = "Get";
+
+  if (HasFieldPresence(descriptor->file())) {
+    (*variables)["set_hasbit"] =
+        "set_has_" + FieldName(descriptor) + "();";
+    (*variables)["clear_hasbit"] =
+        "clear_has_" + FieldName(descriptor) + "();";
+  } else {
+    (*variables)["set_hasbit"] = "";
+    (*variables)["clear_hasbit"] = "";
+  }
+
+  // By default, empty string, so that generic code used for both oneofs and
+  // singular fields can be written.
+  (*variables)["oneof_prefix"] = "";
 }
 
 void SetCommonOneofFieldVariables(const FieldDescriptor* descriptor,
diff --git a/src/google/protobuf/compiler/cpp/cpp_field.h b/src/google/protobuf/compiler/cpp/cpp_field.h
index 0342c35e..088e5063 100644
--- a/src/google/protobuf/compiler/cpp/cpp_field.h
+++ b/src/google/protobuf/compiler/cpp/cpp_field.h
@@ -37,6 +37,9 @@
 
 #include <map>
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <string>
 
 #include <google/protobuf/descriptor.h>
@@ -124,6 +127,16 @@ class FieldGenerator {
   // Most field types don't need this, so the default implementation is empty.
   virtual void GenerateDestructorCode(io::Printer* /*printer*/) const {}
 
+  // Generate a manual destructor invocation for use when the message is on an
+  // arena. The code that this method generates will be executed inside a
+  // shared-for-the-whole-message-class method registered with OwnDestructor().
+  // The method should return |true| if it generated any code that requires a
+  // call; this allows the message generator to eliminate the OwnDestructor()
+  // registration if no fields require it.
+  virtual bool GenerateArenaDestructorCode(io::Printer* printer) const {
+    return false;
+  }
+
   // Generate code that allocates the fields's default instance.
   virtual void GenerateDefaultInstanceAllocator(io::Printer* /*printer*/)
       const {}
diff --git a/src/google/protobuf/compiler/cpp/cpp_file.cc b/src/google/protobuf/compiler/cpp/cpp_file.cc
index fa194273..dc8bf613 100644
--- a/src/google/protobuf/compiler/cpp/cpp_file.cc
+++ b/src/google/protobuf/compiler/cpp/cpp_file.cc
@@ -34,6 +34,9 @@
 
 #include <google/protobuf/compiler/cpp/cpp_file.h>
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <set>
 
 #include <google/protobuf/compiler/cpp/cpp_enum.h>
@@ -102,6 +105,7 @@ void FileGenerator::GenerateHeader(io::Printer* printer) {
     "#define PROTOBUF_$filename_identifier$__INCLUDED\n"
     "\n"
     "#include <string>\n"
+    "#include <stdint.h>\n"  // INT32_MIN, INT32_MAX
     "\n",
     "filename", file_->name(),
     "filename_identifier", filename_identifier);
@@ -131,7 +135,10 @@ void FileGenerator::GenerateHeader(io::Printer* printer) {
 
   // OK, it's now safe to #include other files.
   printer->Print(
-    "#include <google/protobuf/generated_message_util.h>\n");
+    "#include <google/protobuf/arena.h>\n"
+    "#include <google/protobuf/arenastring.h>\n"
+    "#include <google/protobuf/generated_message_util.h>\n"
+    "#include <google/protobuf/metadata.h>\n");
   if (file_->message_type_count() > 0) {
     if (HasDescriptorMethods(file_)) {
       printer->Print(
@@ -181,6 +188,7 @@ void FileGenerator::GenerateHeader(io::Printer* printer) {
     "// @@protoc_insertion_point(includes)\n");
 
 
+
   // Open namespace.
   GenerateNamespaceOpeners(printer);
 
@@ -189,9 +197,10 @@ void FileGenerator::GenerateHeader(io::Printer* printer) {
   printer->Print(
     "\n"
     "// Internal implementation detail -- do not call these.\n"
-    "void $dllexport_decl$ $adddescriptorsname$();\n",
+    "void $dllexport_decl$$adddescriptorsname$();\n",
     "adddescriptorsname", GlobalAddDescriptorsName(file_->name()),
-    "dllexport_decl", options_.dllexport_decl);
+    "dllexport_decl",
+    options_.dllexport_decl.empty() ? "" : options_.dllexport_decl + " ");
 
   printer->Print(
     // Note that we don't put dllexport_decl on these because they are only
@@ -295,7 +304,7 @@ void FileGenerator::GenerateHeader(io::Printer* printer) {
     }
     printer->Print(
         "\n"
-        "}  // namespace google\n}  // namespace protobuf\n"
+        "}  // namespace protobuf\n}  // namespace google\n"
         "#endif  // SWIG\n");
   }
 
diff --git a/src/google/protobuf/compiler/cpp/cpp_file.h b/src/google/protobuf/compiler/cpp/cpp_file.h
index 4e4d8b6a..13d06f98 100644
--- a/src/google/protobuf/compiler/cpp/cpp_file.h
+++ b/src/google/protobuf/compiler/cpp/cpp_file.h
@@ -36,6 +36,9 @@
 #define GOOGLE_PROTOBUF_COMPILER_CPP_FILE_H__
 
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <string>
 #include <vector>
 #include <google/protobuf/stubs/common.h>
diff --git a/src/google/protobuf/compiler/cpp/cpp_generator.cc b/src/google/protobuf/compiler/cpp/cpp_generator.cc
index 75d558ea..a2fb7162 100644
--- a/src/google/protobuf/compiler/cpp/cpp_generator.cc
+++ b/src/google/protobuf/compiler/cpp/cpp_generator.cc
@@ -36,6 +36,9 @@
 
 #include <vector>
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <utility>
 
 #include <google/protobuf/compiler/cpp/cpp_file.h>
diff --git a/src/google/protobuf/compiler/cpp/cpp_helpers.cc b/src/google/protobuf/compiler/cpp/cpp_helpers.cc
index b7a47acb..63b0265e 100644
--- a/src/google/protobuf/compiler/cpp/cpp_helpers.cc
+++ b/src/google/protobuf/compiler/cpp/cpp_helpers.cc
@@ -60,16 +60,17 @@ string DotsToColons(const string& name) {
 }
 
 const char* const kKeywordList[] = {
-  "and", "and_eq", "asm", "auto", "bitand", "bitor", "bool", "break", "case",
-  "catch", "char", "class", "compl", "const", "const_cast", "continue",
-  "default", "delete", "do", "double", "dynamic_cast", "else", "enum",
-  "explicit", "extern", "false", "float", "for", "friend", "goto", "if",
-  "inline", "int", "long", "mutable", "namespace", "new", "not", "not_eq",
-  "operator", "or", "or_eq", "private", "protected", "public", "register",
-  "reinterpret_cast", "return", "short", "signed", "sizeof", "static",
-  "static_cast", "struct", "switch", "template", "this", "throw", "true", "try",
-  "typedef", "typeid", "typename", "union", "unsigned", "using", "virtual",
-  "void", "volatile", "wchar_t", "while", "xor", "xor_eq"
+  "alignas", "alignof", "and", "and_eq", "asm", "auto", "bitand", "bitor",
+  "bool", "break", "case", "catch", "char", "class", "compl", "const",
+  "constexpr", "const_cast", "continue", "decltype", "default", "delete", "do",
+  "double", "dynamic_cast", "else", "enum", "explicit", "extern", "false",
+  "float", "for", "friend", "goto", "if", "inline", "int", "long", "mutable",
+  "namespace", "new", "noexcept", "not", "not_eq", "nullptr", "operator", "or",
+  "or_eq", "private", "protected", "public", "register", "reinterpret_cast",
+  "return", "short", "signed", "sizeof", "static", "static_assert",
+  "static_cast", "struct", "switch", "template", "this", "thread_local",
+  "throw", "true", "try", "typedef", "typeid", "typename", "union", "unsigned",
+  "using", "virtual", "void", "volatile", "wchar_t", "while", "xor", "xor_eq"
 };
 
 hash_set<string> MakeKeywordsMap() {
diff --git a/src/google/protobuf/compiler/cpp/cpp_helpers.h b/src/google/protobuf/compiler/cpp/cpp_helpers.h
index 5d30240c..1cff17c8 100644
--- a/src/google/protobuf/compiler/cpp/cpp_helpers.h
+++ b/src/google/protobuf/compiler/cpp/cpp_helpers.h
@@ -135,8 +135,15 @@ string SafeFunctionName(const Descriptor* descriptor,
                         const FieldDescriptor* field,
                         const string& prefix);
 
-// Do message classes in this file use UnknownFieldSet?
-// Otherwise, messages will store unknown fields in a string
+// Returns true if unknown fields are preseved after parsing.
+inline bool PreserveUnknownFields(const Descriptor* message) {
+  return message->file()->syntax() != FileDescriptor::SYNTAX_PROTO3;
+}
+
+// If PreserveUnknownFields() is true, determines whether unknown
+// fields will be stored in an UnknownFieldSet or a string.
+// If PreserveUnknownFields() is false, this method will not be
+// used.
 inline bool UseUnknownFieldSet(const FileDescriptor* file) {
   return file->options().optimize_for() != FileOptions::LITE_RUNTIME;
 }
@@ -198,6 +205,28 @@ bool IsStringOrMessage(const FieldDescriptor* field);
 
 string UnderscoresToCamelCase(const string& input, bool cap_next_letter);
 
+inline bool HasFieldPresence(const FileDescriptor* file) {
+  return file->syntax() != FileDescriptor::SYNTAX_PROTO3;
+}
+
+// Returns true if 'enum' semantics are such that unknown values are preserved
+// in the enum field itself, rather than going to the UnknownFieldSet.
+inline bool HasPreservingUnknownEnumSemantics(const FileDescriptor* file) {
+  return file->syntax() == FileDescriptor::SYNTAX_PROTO3;
+}
+
+inline bool SupportsArenas(const FileDescriptor* file) {
+  return true;
+}
+
+inline bool SupportsArenas(const Descriptor* desc) {
+  return SupportsArenas(desc->file());
+}
+
+inline bool SupportsArenas(const FieldDescriptor* field) {
+  return SupportsArenas(field->file());
+}
+
 }  // namespace cpp
 }  // namespace compiler
 }  // namespace protobuf
diff --git a/src/google/protobuf/compiler/cpp/cpp_message.cc b/src/google/protobuf/compiler/cpp/cpp_message.cc
index 3a9d2639..54a92ae4 100644
--- a/src/google/protobuf/compiler/cpp/cpp_message.cc
+++ b/src/google/protobuf/compiler/cpp/cpp_message.cc
@@ -36,6 +36,9 @@
 #include <google/protobuf/stubs/hash.h>
 #include <map>
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <set>
 #include <utility>
 #include <vector>
@@ -281,8 +284,67 @@ string MessageTypeProtoName(const FieldDescriptor* field) {
   return field->message_type()->full_name();
 }
 
+// Emits an if-statement with a condition that evaluates to true if |field| is
+// considered non-default (will be sent over the wire), for message types
+// without true field presence. Should only be called if
+// !HasFieldPresence(message_descriptor).
+bool EmitFieldNonDefaultCondition(io::Printer* printer,
+                                  const string& prefix,
+                                  const FieldDescriptor* field) {
+  // Merge and serialize semantics: primitive fields are merged/serialized only
+  // if non-zero (numeric) or non-empty (string).
+  if (!field->is_repeated() && !field->containing_oneof()) {
+    if (field->cpp_type() == FieldDescriptor::CPPTYPE_STRING) {
+      printer->Print(
+          "if ($prefix$$name$().size() > 0) {\n",
+          "prefix", prefix,
+          "name", FieldName(field));
+    } else if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
+      // Message fields still have has_$name$() methods.
+      printer->Print(
+          "if ($prefix$has_$name$()) {\n",
+          "prefix", prefix,
+          "name", FieldName(field));
+    } else {
+      printer->Print(
+          "if ($prefix$$name$() != 0) {\n",
+          "prefix", prefix,
+          "name", FieldName(field));
+    }
+    printer->Indent();
+    return true;
+  } else if (field->containing_oneof()) {
+    printer->Print(
+        "if (has_$name$()) {\n",
+        "name", FieldName(field));
+    printer->Indent();
+    return true;
+  }
+  return false;
+}
+
+// Does the given field have a has_$name$() method?
+bool HasHasMethod(const FieldDescriptor* field) {
+  if (HasFieldPresence(field->file())) {
+    // In proto1/proto2, every field has a has_$name$() method.
+    return true;
+  }
+  // For message types without true field presence, only fields with a message
+  // type have a has_$name$() method.
+  return field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE;
 }
 
+// Does the given field have a private (internal helper only) has_$name$()
+// method?
+bool HasPrivateHasMethod(const FieldDescriptor* field) {
+  // Only for oneofs in message types with no field presence. has_$name$(),
+  // based on the oneof case, is still useful internally for generated code.
+  return (!HasFieldPresence(field->file()) &&
+          field->containing_oneof() != NULL);
+}
+
+}  // anonymous namespace
+
 // ===================================================================
 
 MessageGenerator::MessageGenerator(const Descriptor* descriptor,
@@ -312,6 +374,13 @@ MessageGenerator::MessageGenerator(const Descriptor* descriptor,
     extension_generators_[i].reset(
       new ExtensionGenerator(descriptor->extension(i), options));
   }
+
+  num_required_fields_ = 0;
+  for (int i = 0; i < descriptor->field_count(); i++) {
+    if (descriptor->field(i)->is_required()) {
+      ++num_required_fields_;
+    }
+  }
 }
 
 MessageGenerator::~MessageGenerator() {}
@@ -360,8 +429,13 @@ GenerateFieldAccessorDeclarations(io::Printer* printer) {
 
     if (field->is_repeated()) {
       printer->Print(vars, "inline int $name$_size() const$deprecation$;\n");
-    } else {
+    } else if (HasHasMethod(field)) {
       printer->Print(vars, "inline bool has_$name$() const$deprecation$;\n");
+    } else if (HasPrivateHasMethod(field)) {
+      printer->Print(vars,
+          "private:\n"
+          "inline bool has_$name$() const$deprecation$;\n"
+          "public:\n");
     }
 
     printer->Print(vars, "inline void clear_$name$()$deprecation$;\n");
@@ -410,32 +484,59 @@ GenerateFieldAccessorDefinitions(io::Printer* printer) {
         "}\n");
     } else if (field->containing_oneof()) {
       // Singular field in a oneof
+      // N.B.: Without field presence, we do not use has-bits or generate
+      // has_$name$() methods, but oneofs still have set_has_$name$().
+      // Oneofs also have has_$name$() but only as a private helper
+      // method, so that generated code is slightly cleaner (vs.  comparing
+      // _oneof_case_[index] against a constant everywhere).
       vars["field_name"] = UnderscoresToCamelCase(field->name(), true);
       vars["oneof_name"] = field->containing_oneof()->name();
       vars["oneof_index"] = SimpleItoa(field->containing_oneof()->index());
       printer->Print(vars,
         "inline bool $classname$::has_$name$() const {\n"
         "  return $oneof_name$_case() == k$field_name$;\n"
-        "}\n"
+        "}\n");
+      printer->Print(vars,
         "inline void $classname$::set_has_$name$() {\n"
         "  _oneof_case_[$oneof_index$] = k$field_name$;\n"
         "}\n");
     } else {
       // Singular field.
-      char buffer[kFastToBufferSize];
-      vars["has_array_index"] = SimpleItoa(field->index() / 32);
-      vars["has_mask"] = FastHex32ToBuffer(1u << (field->index() % 32), buffer);
-      printer->Print(vars,
-        "inline bool $classname$::has_$name$() const {\n"
-        "  return (_has_bits_[$has_array_index$] & 0x$has_mask$u) != 0;\n"
-        "}\n"
-        "inline void $classname$::set_has_$name$() {\n"
-        "  _has_bits_[$has_array_index$] |= 0x$has_mask$u;\n"
-        "}\n"
-        "inline void $classname$::clear_has_$name$() {\n"
-        "  _has_bits_[$has_array_index$] &= ~0x$has_mask$u;\n"
-        "}\n"
-        );
+      if (HasFieldPresence(descriptor_->file())) {
+        // N.B.: without field presence, we do not use has-bits or generate
+        // has_$name$() methods.
+        char buffer[kFastToBufferSize];
+        vars["has_array_index"] = SimpleItoa(field->index() / 32);
+        vars["has_mask"] = FastHex32ToBuffer(1u << (field->index() % 32),
+                                             buffer);
+        printer->Print(vars,
+          "inline bool $classname$::has_$name$() const {\n"
+          "  return (_has_bits_[$has_array_index$] & 0x$has_mask$u) != 0;\n"
+          "}\n"
+          "inline void $classname$::set_has_$name$() {\n"
+          "  _has_bits_[$has_array_index$] |= 0x$has_mask$u;\n"
+          "}\n"
+          "inline void $classname$::clear_has_$name$() {\n"
+          "  _has_bits_[$has_array_index$] &= ~0x$has_mask$u;\n"
+          "}\n"
+          );
+      } else {
+        // Message fields have a has_$name$() method.
+        if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
+          bool is_lazy = false;
+          if (is_lazy) {
+            printer->Print(vars,
+              "inline bool $classname$::has_$name$() const {\n"
+              "  return !$name$_.IsCleared();\n"
+              "}\n");
+          } else {
+            printer->Print(vars,
+              "inline bool $classname$::has_$name$() const {\n"
+              "  return $name$_ != NULL;\n"
+              "}\n");
+          }
+        }
+      }
     }
 
     // Generate clear_$name$()
@@ -457,9 +558,11 @@ GenerateFieldAccessorDefinitions(io::Printer* printer) {
       printer->Print("}\n");
     } else {
       field_generators_.get(field).GenerateClearingCode(printer);
-      if (!field->is_repeated()) {
-        printer->Print(vars,
-                       "clear_has_$name$();\n");
+      if (HasFieldPresence(descriptor_->file())) {
+        if (!field->is_repeated()) {
+          printer->Print(vars,
+                         "clear_has_$name$();\n");
+        }
       }
     }
 
@@ -553,26 +656,41 @@ GenerateClassDefinition(io::Printer* printer) {
     "}\n"
     "\n");
 
-  if (UseUnknownFieldSet(descriptor_->file())) {
-    printer->Print(
-      "inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {\n"
-      "  return _unknown_fields_;\n"
-      "}\n"
-      "\n"
-      "inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {\n"
-      "  return &_unknown_fields_;\n"
-      "}\n"
-      "\n");
-  } else {
+  if (PreserveUnknownFields(descriptor_)) {
+    if (UseUnknownFieldSet(descriptor_->file())) {
+      printer->Print(
+        "inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {\n"
+        "  return _internal_metadata_.unknown_fields();\n"
+        "}\n"
+        "\n"
+        "inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {\n"
+        "  return _internal_metadata_.mutable_unknown_fields();\n"
+        "}\n"
+        "\n");
+    } else {
+      printer->Print(
+        "inline const ::std::string& unknown_fields() const {\n"
+        "  return _unknown_fields_;\n"
+        "}\n"
+        "\n"
+        "inline ::std::string* mutable_unknown_fields() {\n"
+        "  return &_unknown_fields_;\n"
+        "}\n"
+        "\n");
+    }
+  }
+
+  // N.B.: We exclude GetArena() when arena support is disabled, falling back on
+  // MessageLite's implementation which returns NULL rather than generating our
+  // own method which returns NULL, in order to reduce code size.
+  if (SupportsArenas(descriptor_)) {
+    // virtual method version of GetArenaNoVirtual(), required for generic dispatch given a
+    // MessageLite* (e.g., in RepeatedField::AddAllocated()).
     printer->Print(
-      "inline const ::std::string& unknown_fields() const {\n"
-      "  return _unknown_fields_;\n"
-      "}\n"
-      "\n"
-      "inline ::std::string* mutable_unknown_fields() {\n"
-      "  return &_unknown_fields_;\n"
-      "}\n"
-      "\n");
+        "inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }\n"
+        "inline void* GetMaybeArenaPointer() const {\n"
+        "  return MaybeArenaPtr();\n"
+        "}\n");
   }
 
   // Only generate this member if it's not disabled.
@@ -628,12 +746,18 @@ GenerateClassDefinition(io::Printer* printer) {
   }
 
 
+  if (SupportsArenas(descriptor_)) {
+    printer->Print(vars,
+      "void UnsafeArenaSwap($classname$* other);\n");
+  }
   printer->Print(vars,
     "void Swap($classname$* other);\n"
     "\n"
     "// implements Message ----------------------------------------------\n"
     "\n"
-    "$classname$* New() const;\n");
+    "inline $classname$* New() const { return New(NULL); }\n"
+    "\n"
+    "$classname$* New(::google::protobuf::Arena* arena) const;\n");
 
   if (HasGeneratedMethods(descriptor_->file())) {
     if (HasDescriptorMethods(descriptor_->file())) {
@@ -699,7 +823,41 @@ GenerateClassDefinition(io::Printer* printer) {
     "void SharedCtor();\n"
     "void SharedDtor();\n"
     "void SetCachedSize(int size) const;\n"
-    "public:\n");
+    "void InternalSwap($classname$* other);\n",
+    "classname", classname_);
+  if (SupportsArenas(descriptor_)) {
+    printer->Print(
+      "protected:\n"
+      "explicit $classname$(::google::protobuf::Arena* arena);\n"
+      "private:\n"
+      "static void ArenaDtor(void* object);\n"
+      "inline void RegisterArenaDtor(::google::protobuf::Arena* arena);\n",
+      "classname", classname_);
+  }
+
+  if (UseUnknownFieldSet(descriptor_->file())) {
+    printer->Print(
+      "private:\n"
+      "inline ::google::protobuf::Arena* GetArenaNoVirtual() const {\n"
+      "  return _internal_metadata_.arena();\n"
+      "}\n"
+      "inline void* MaybeArenaPtr() const {\n"
+      "  return _internal_metadata_.raw_arena_ptr();\n"
+      "}\n"
+      "public:\n"
+      "\n");
+  } else {
+    printer->Print(
+      "private:\n"
+      "inline ::google::protobuf::Arena* GetArenaNoVirtual() const {\n"
+      "  return _arena_ptr_;\n"
+      "}\n"
+      "inline ::google::protobuf::Arena* MaybeArenaPtr() const {\n"
+      "  return _arena_ptr_;\n"
+      "}\n"
+      "public:\n"
+      "\n");
+  }
 
   if (HasDescriptorMethods(descriptor_->file())) {
     printer->Print(
@@ -759,10 +917,18 @@ GenerateClassDefinition(io::Printer* printer) {
 
   for (int i = 0; i < descriptor_->field_count(); i++) {
     if (!descriptor_->field(i)->is_repeated()) {
-      printer->Print(
-        "inline void set_has_$name$();\n",
-        "name", FieldName(descriptor_->field(i)));
-      if (!descriptor_->field(i)->containing_oneof()) {
+      // set_has_***() generated in all proto1/2 code and in oneofs (only) for
+      // messages without true field presence.
+      if (HasFieldPresence(descriptor_->file()) ||
+          descriptor_->field(i)->containing_oneof()) {
+        printer->Print(
+          "inline void set_has_$name$();\n",
+          "name", FieldName(descriptor_->field(i)));
+      }
+      // clear_has_***() generated only for non-oneof fields
+      // in proto1/2.
+      if (!descriptor_->field(i)->containing_oneof() &&
+          HasFieldPresence(descriptor_->file())) {
         printer->Print(
           "inline void clear_has_$name$();\n",
           "name", FieldName(descriptor_->field(i)));
@@ -780,6 +946,14 @@ GenerateClassDefinition(io::Printer* printer) {
         "oneof_name", descriptor_->oneof_decl(i)->name());
   }
 
+  if (HasGeneratedMethods(descriptor_->file()) &&
+      !descriptor_->options().message_set_wire_format() &&
+      num_required_fields_ > 1) {
+    printer->Print(
+        "// helper for ByteSize()\n"
+        "int RequiredFieldsByteSizeFallback() const;\n\n");
+  }
+
   // Prepare decls for _cached_size_ and _has_bits_.  Their position in the
   // output will be determined later.
 
@@ -816,23 +990,32 @@ GenerateClassDefinition(io::Printer* printer) {
 
   if (UseUnknownFieldSet(descriptor_->file())) {
     printer->Print(
-      "::google::protobuf::UnknownFieldSet _unknown_fields_;\n"
-      "\n");
+      "::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;\n");
   } else {
     printer->Print(
       "::std::string _unknown_fields_;\n"
+      "::google::protobuf::Arena* _arena_ptr_;\n"
       "\n");
   }
 
-  // _has_bits_ is frequently accessed, so to reduce code size and improve
-  // speed, it should be close to the start of the object.  But, try not to
-  // waste space:_has_bits_ by itself always makes sense if its size is a
-  // multiple of 8, but, otherwise, maybe _has_bits_ and cached_size_ together
-  // will work well.
-  printer->Print(has_bits_decl.c_str());
-  if ((sizeof_has_bits % 8) != 0) {
-    printer->Print(cached_size_decl.c_str());
-    need_to_emit_cached_size = false;
+  if (SupportsArenas(descriptor_)) {
+    printer->Print(
+      "friend class ::google::protobuf::Arena;\n"
+      "typedef void InternalArenaConstructable_;\n"
+      "typedef void DestructorSkippable_;\n");
+  }
+
+  if (HasFieldPresence(descriptor_->file())) {
+    // _has_bits_ is frequently accessed, so to reduce code size and improve
+    // speed, it should be close to the start of the object.  But, try not to
+    // waste space:_has_bits_ by itself always makes sense if its size is a
+    // multiple of 8, but, otherwise, maybe _has_bits_ and cached_size_ together
+    // will work well.
+    printer->Print(has_bits_decl.c_str());
+    if ((sizeof_has_bits % 8) != 0) {
+      printer->Print(cached_size_decl.c_str());
+      need_to_emit_cached_size = false;
+    }
   }
 
   // Field members:
@@ -871,7 +1054,10 @@ GenerateClassDefinition(io::Printer* printer) {
   // For each oneof generate a union
   for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
     printer->Print(
-        "union $camel_oneof_name$Union {\n",
+        "union $camel_oneof_name$Union {\n"
+        // explicit empty constructor is needed when union contains
+        // ArenaStringPtr members for string fields.
+        "  $camel_oneof_name$Union() {}\n",
         "camel_oneof_name",
         UnderscoresToCamelCase(descriptor_->oneof_decl(i)->name(), true));
     printer->Indent();
@@ -1029,10 +1215,28 @@ GenerateDescriptorInitializer(io::Printer* printer, int index) {
     "  new ::google::protobuf::internal::GeneratedMessageReflection(\n"
     "    $classname$_descriptor_,\n"
     "    $classname$::default_instance_,\n"
-    "    $classname$_offsets_,\n"
-    "    GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET($classname$, _has_bits_[0]),\n"
+    "    $classname$_offsets_,\n");
+  if (!HasFieldPresence(descriptor_->file())) {
+    // If we don't have field presence, then _has_bits_ does not exist.
+    printer->Print(vars,
+    "    -1,\n");
+  } else {
+    printer->Print(vars,
+    "    GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET($classname$, _has_bits_[0]),\n");
+  }
+
+  // Unknown field offset: either points to the unknown field set if embedded
+  // directly, or indicates that the unknown field set is stored as part of the
+  // internal metadata if not.
+  if (UseUnknownFieldSet(descriptor_->file())) {
+    printer->Print(vars,
+    "    -1,\n");
+  } else {
+    printer->Print(vars,
     "    GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET("
       "$classname$, _unknown_fields_),\n");
+  }
+
   if (descriptor_->extension_range_count() > 0) {
     printer->Print(vars,
       "    GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET("
@@ -1054,8 +1258,23 @@ GenerateDescriptorInitializer(io::Printer* printer, int index) {
     "    ::google::protobuf::DescriptorPool::generated_pool(),\n");
   printer->Print(vars,
     "    ::google::protobuf::MessageFactory::generated_factory(),\n");
+
   printer->Print(vars,
-    "    sizeof($classname$));\n");
+    "    sizeof($classname$),\n");
+
+  // Arena offset: either an offset to the metadata struct that contains the
+  // arena pointer and unknown field set (in a space-efficient way) if we use
+  // that implementation strategy, or an offset directly to the arena pointer if
+  // not (because e.g. we don't have an unknown field set).
+  if (UseUnknownFieldSet(descriptor_->file())) {
+    printer->Print(vars,
+    "    GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET("
+    "$classname$, _internal_metadata_));\n");
+  } else {
+    printer->Print(vars,
+    "    GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET("
+    "$classname$, _arena_));\n");
+  }
 
   // Handle nested types.
   for (int i = 0; i < descriptor_->nested_type_count(); i++) {
@@ -1100,7 +1319,7 @@ GenerateDefaultInstanceAllocator(io::Printer* printer) {
   if ((descriptor_->oneof_decl_count() > 0) &&
       HasDescriptorMethods(descriptor_->file())) {
     printer->Print(
-    "$classname$_default_oneof_instance_ = new $classname$OneofInstance;\n",
+    "$classname$_default_oneof_instance_ = new $classname$OneofInstance();\n",
     "classname", classname_);
   }
 
@@ -1312,8 +1531,10 @@ GenerateSharedConstructorCode(io::Printer* printer) {
     }
   }
 
-  printer->Print(
-    "::memset(_has_bits_, 0, sizeof(_has_bits_));\n");
+  if (HasFieldPresence(descriptor_->file())) {
+    printer->Print(
+      "::memset(_has_bits_, 0, sizeof(_has_bits_));\n");
+  }
 
   for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
     printer->Print(
@@ -1331,6 +1552,14 @@ GenerateSharedDestructorCode(io::Printer* printer) {
     "void $classname$::SharedDtor() {\n",
     "classname", classname_);
   printer->Indent();
+  if (SupportsArenas(descriptor_)) {
+    // Do nothing when the message is allocated in an arena.
+    printer->Print(
+      "if (GetArenaNoVirtual() != NULL) {\n"
+      "  return;\n"
+      "}\n"
+      "\n");
+  }
   // Write the destructors for each field except oneof members.
   for (int i = 0; i < descriptor_->field_count(); i++) {
     if (!descriptor_->field(i)->containing_oneof()) {
@@ -1381,19 +1610,107 @@ GenerateSharedDestructorCode(io::Printer* printer) {
 }
 
 void MessageGenerator::
+GenerateArenaDestructorCode(io::Printer* printer) {
+  // Generate the ArenaDtor() method. Track whether any fields actually produced
+  // code that needs to be called.
+  printer->Print(
+      "void $classname$::ArenaDtor(void* object) {\n",
+      "classname", classname_);
+  printer->Indent();
+
+  // This code is placed inside a static method, rather than an ordinary one,
+  // since that simplifies Arena's destructor list (ordinary function pointers
+  // rather than member function pointers). _this is the object being
+  // destructed.
+  printer->Print(
+      "$classname$* _this = reinterpret_cast< $classname$* >(object);\n"
+      // avoid an "unused variable" warning in case no fields have dtor code.
+      "(void)_this;\n",
+      "classname", classname_);
+
+  bool need_registration = false;
+  for (int i = 0; i < descriptor_->field_count(); i++) {
+    if (field_generators_.get(descriptor_->field(i))
+                         .GenerateArenaDestructorCode(printer)) {
+      need_registration = true;
+    }
+  }
+  printer->Outdent();
+  printer->Print(
+      "}\n");
+
+  if (need_registration) {
+    printer->Print(
+        "inline void $classname$::RegisterArenaDtor(::google::protobuf::Arena* arena) {\n"
+        "  if (arena != NULL) {"
+        "    arena->OwnCustomDestructor(this, &$classname$::ArenaDtor);\n"
+        "  }\n"
+        "}\n",
+        "classname", classname_);
+  } else {
+    printer->Print(
+        "void $classname$::RegisterArenaDtor(::google::protobuf::Arena* arena) {\n"
+        "}\n",
+        "classname", classname_);
+  }
+}
+
+void MessageGenerator::
 GenerateStructors(io::Printer* printer) {
   string superclass = SuperClassName(descriptor_);
+  string initializer_with_arena;
+  if (UseUnknownFieldSet(descriptor_->file())) {
+    initializer_with_arena = "_internal_metadata_(arena)";
+  } else {
+    initializer_with_arena = "_arena_ptr_(arena)";
+  }
+  if (descriptor_->extension_range_count() > 0) {
+      initializer_with_arena  = string("\n  _extensions_(arena)") +
+        (!initializer_with_arena.empty() ?  ", " : "") + initializer_with_arena;
+  } else {
+    initializer_with_arena  = "\n  " + initializer_with_arena;
+  }
+
+  // Initialize member variables with arena constructor.
+  for (int i = 0; i < descriptor_->field_count(); i++) {
+    bool has_arena_constructor = descriptor_->field(i)->is_repeated();
+    if (has_arena_constructor) {
+      initializer_with_arena += string(",\n  ") +
+          FieldName(descriptor_->field(i)) + string("_(arena)");
+    }
+  }
+  initializer_with_arena = superclass + "()" +
+      (!initializer_with_arena.empty() ?  "," : " ") + initializer_with_arena;
+
+  string initializer_null;
+  initializer_null = (UseUnknownFieldSet(descriptor_->file()) ?
+    ", _internal_metadata_(NULL) " : ", _arena_ptr_(NULL)");
 
-  // Generate the default constructor.
   printer->Print(
-    "$classname$::$classname$()\n"
-    "  : $superclass$() {\n"
-    "  SharedCtor();\n"
-    "  // @@protoc_insertion_point(constructor:$full_name$)\n"
-    "}\n",
-    "classname", classname_,
-    "superclass", superclass,
-    "full_name", descriptor_->full_name());
+      "$classname$::$classname$()\n"
+      "  : $superclass$() $initializer$ {\n"
+      "  SharedCtor();\n"
+      "  // @@protoc_insertion_point(constructor:$full_name$)\n"
+      "}\n",
+      "classname", classname_,
+      "superclass", superclass,
+      "full_name", descriptor_->full_name(),
+      "initializer", initializer_null);
+
+  if (SupportsArenas(descriptor_)) {
+    printer->Print(
+        "\n"
+        "$classname$::$classname$(::google::protobuf::Arena* arena)\n"
+        "  : $initializer$ {\n"
+        "  SharedCtor();\n"
+        "  RegisterArenaDtor(arena);\n"
+        "  // @@protoc_insertion_point(arena_constructor:$full_name$)\n"
+        "}\n",
+        "initializer", initializer_with_arena,
+        "classname", classname_,
+        "superclass", superclass,
+        "full_name", descriptor_->full_name());
+  }
 
   printer->Print(
     "\n"
@@ -1441,7 +1758,17 @@ GenerateStructors(io::Printer* printer) {
   // Generate the copy constructor.
   printer->Print(
     "$classname$::$classname$(const $classname$& from)\n"
-    "  : $superclass$() {\n"
+    "  : $superclass$()",
+    "classname", classname_,
+    "superclass", superclass,
+    "full_name", descriptor_->full_name());
+  if (UseUnknownFieldSet(descriptor_->file())) {
+    printer->Print(
+        ",\n    _internal_metadata_(NULL) {\n");
+  } else if (!UseUnknownFieldSet(descriptor_->file())) {
+    printer->Print(",\n    _arena_ptr_(NULL) {\n");
+  }
+  printer->Print(
     "  SharedCtor();\n"
     "  MergeFrom(from);\n"
     "  // @@protoc_insertion_point(copy_constructor:$full_name$)\n"
@@ -1467,6 +1794,11 @@ GenerateStructors(io::Printer* printer) {
   // Generate the shared destructor code.
   GenerateSharedDestructorCode(printer);
 
+  // Generate the arena-specific destructor code.
+  if (SupportsArenas(descriptor_)) {
+    GenerateArenaDestructorCode(printer);
+  }
+
   // Generate SetCachedSize.
   printer->Print(
     "void $classname$::SetCachedSize(int size) const {\n"
@@ -1512,11 +1844,23 @@ GenerateStructors(io::Printer* printer) {
     "\n",
     "classname", classname_);
 
-  printer->Print(
-    "$classname$* $classname$::New() const {\n"
-    "  return new $classname$;\n"
-    "}\n",
-    "classname", classname_);
+  if (SupportsArenas(descriptor_)) {
+    printer->Print(
+      "$classname$* $classname$::New(::google::protobuf::Arena* arena) const {\n"
+      "  return ::google::protobuf::Arena::CreateMessage<$classname$>(arena);\n"
+      "}\n",
+      "classname", classname_);
+  } else {
+    printer->Print(
+      "$classname$* $classname$::New(::google::protobuf::Arena* arena) const {\n"
+      "  $classname$* n = new $classname$;\n"
+      "  if (arena != NULL) {\n"
+      "    arena->Own(n);\n"
+      "  }\n"
+      "  return n;\n"
+      "}\n",
+      "classname", classname_);
+  }
 
 }
 
@@ -1616,16 +1960,19 @@ GenerateClear(io::Printer* printer) {
       const string& memsets = memsets_for_chunk[i / 8];
       uint32 mask = fields_mask_for_chunk[i / 8];
       int count = popcnt(mask);
+      GOOGLE_DCHECK_GE(count, 1);
       if (count == 1 ||
           (count <= 4 && count == memset_field_count_for_chunk[i / 8])) {
         // No "if" here because the chunk is trivial.
       } else {
-        printer->Print(
-          "if (_has_bits_[$index$ / 32] & $mask$) {\n",
-          "index", SimpleItoa(i / 8 * 8),
-          "mask", SimpleItoa(mask));
-        printer->Indent();
-        chunk_block_in_progress = true;
+        if (HasFieldPresence(descriptor_->file())) {
+          printer->Print(
+            "if (_has_bits_[$index$ / 32] & $mask$) {\n",
+            "index", SimpleItoa(i / 8 * 8),
+            "mask", SimpleItoa(mask));
+          printer->Indent();
+          chunk_block_in_progress = true;
+        }
       }
       printer->Print(memsets.c_str());
     }
@@ -1639,14 +1986,18 @@ GenerateClear(io::Printer* printer) {
       field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE ||
       field->cpp_type() == FieldDescriptor::CPPTYPE_STRING;
 
-    if (should_check_bit) {
+    bool have_enclosing_if = false;
+    if (should_check_bit &&
+        // If no field presence, then always clear strings/messages as well.
+        HasFieldPresence(descriptor_->file())) {
       printer->Print("if (has_$name$()) {\n", "name", fieldname);
       printer->Indent();
+      have_enclosing_if = true;
     }
 
     field_generators_.get(field).GenerateClearingCode(printer);
 
-    if (should_check_bit) {
+    if (have_enclosing_if) {
       printer->Outdent();
       printer->Print("}\n");
     }
@@ -1678,16 +2029,22 @@ GenerateClear(io::Printer* printer) {
         "oneof_name", descriptor_->oneof_decl(i)->name());
   }
 
-  // Step 5: Everything else.
-  printer->Print(
-    "::memset(_has_bits_, 0, sizeof(_has_bits_));\n");
-
-  if (UseUnknownFieldSet(descriptor_->file())) {
+  if (HasFieldPresence(descriptor_->file())) {
+    // Step 5: Everything else.
     printer->Print(
-      "mutable_unknown_fields()->Clear();\n");
-  } else {
-    printer->Print(
-      "mutable_unknown_fields()->clear();\n");
+      "::memset(_has_bits_, 0, sizeof(_has_bits_));\n");
+  }
+
+  if (PreserveUnknownFields(descriptor_)) {
+    if (UseUnknownFieldSet(descriptor_->file())) {
+      printer->Print(
+        "if (_internal_metadata_.have_unknown_fields()) {\n"
+        "  mutable_unknown_fields()->Clear();\n"
+        "}\n");
+    } else {
+      printer->Print(
+        "mutable_unknown_fields()->clear();\n");
+    }
   }
 
   printer->Outdent();
@@ -1748,12 +2105,42 @@ GenerateOneofClear(io::Printer* printer) {
 
 void MessageGenerator::
 GenerateSwap(io::Printer* printer) {
-  // Generate the Swap member function.
-  printer->Print("void $classname$::Swap($classname$* other) {\n",
+  if (SupportsArenas(descriptor_)) {
+    // Generate the Swap member function. This is a lightweight wrapper around
+    // UnsafeArenaSwap() / MergeFrom() with temporaries, depending on the memory
+    // ownership situation: swapping across arenas or between an arena and a
+    // heap requires copying.
+    printer->Print(
+        "void $classname$::Swap($classname$* other) {\n"
+        "  if (other == this) return;\n"
+        "  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {\n"
+        "    InternalSwap(other);\n"
+        "  } else {\n"
+        "    $classname$ temp;\n"
+        "    temp.MergeFrom(*this);\n"
+        "    CopyFrom(*other);\n"
+        "    other->CopyFrom(temp);\n"
+        "  }\n"
+        "}\n"
+        "void $classname$::UnsafeArenaSwap($classname$* other) {\n"
+        "  if (other == this) return;\n"
+        "  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());\n"
+        "  InternalSwap(other);\n"
+        "}\n",
+        "classname", classname_);
+  } else {
+    printer->Print(
+        "void $classname$::Swap($classname$* other) {\n"
+        "  if (other == this) return;\n"
+        "  InternalSwap(other);\n"
+        "}\n",
+        "classname", classname_);
+  }
+
+  // Generate the UnsafeArenaSwap member function.
+  printer->Print("void $classname$::InternalSwap($classname$* other) {\n",
                  "classname", classname_);
   printer->Indent();
-  printer->Print("if (other != this) {\n");
-  printer->Indent();
 
   if (HasGeneratedMethods(descriptor_->file())) {
     for (int i = 0; i < descriptor_->field_count(); i++) {
@@ -1769,15 +2156,25 @@ GenerateSwap(io::Printer* printer) {
         "i", SimpleItoa(i));
     }
 
-    for (int i = 0; i < (descriptor_->field_count() + 31) / 32; ++i) {
-      printer->Print("std::swap(_has_bits_[$i$], other->_has_bits_[$i$]);\n",
-                     "i", SimpleItoa(i));
+    if (HasFieldPresence(descriptor_->file())) {
+      for (int i = 0; i < (descriptor_->field_count() + 31) / 32; ++i) {
+        printer->Print("std::swap(_has_bits_[$i$], other->_has_bits_[$i$]);\n",
+                       "i", SimpleItoa(i));
+      }
     }
 
-    if (UseUnknownFieldSet(descriptor_->file())) {
-      printer->Print("_unknown_fields_.Swap(&other->_unknown_fields_);\n");
+    if (PreserveUnknownFields(descriptor_)) {
+      if (UseUnknownFieldSet(descriptor_->file())) {
+        printer->Print(
+          "_internal_metadata_.Swap(&other->_internal_metadata_);\n");
+      } else {
+        printer->Print("_unknown_fields_.swap(other->_unknown_fields_);\n");
+      }
     } else {
-      printer->Print("_unknown_fields_.swap(other->_unknown_fields_);\n");
+      // Still swap internal_metadata as it may contain more than just
+      // unknown fields.
+      printer->Print(
+        "_internal_metadata_.Swap(&other->_internal_metadata_);\n");
     }
     printer->Print("std::swap(_cached_size_, other->_cached_size_);\n");
     if (descriptor_->extension_range_count() > 0) {
@@ -1789,8 +2186,6 @@ GenerateSwap(io::Printer* printer) {
 
   printer->Outdent();
   printer->Print("}\n");
-  printer->Outdent();
-  printer->Print("}\n");
 }
 
 void MessageGenerator::
@@ -1886,33 +2281,48 @@ GenerateMergeFrom(io::Printer* printer) {
     const FieldDescriptor* field = descriptor_->field(i);
 
     if (!field->is_repeated() && !field->containing_oneof()) {
-      // See above in GenerateClear for an explanation of this.
-      if (i / 8 != last_index / 8 || last_index < 0) {
-        if (last_index >= 0) {
-          printer->Outdent();
-          printer->Print("}\n");
+      if (HasFieldPresence(descriptor_->file())) {
+        // See above in GenerateClear for an explanation of this.
+        if (i / 8 != last_index / 8 || last_index < 0) {
+          if (last_index >= 0) {
+            printer->Outdent();
+            printer->Print("}\n");
+          }
+          printer->Print(
+            "if (from._has_bits_[$index$ / 32] & "
+            "(0xffu << ($index$ % 32))) {\n",
+            "index", SimpleItoa(field->index()));
+          printer->Indent();
         }
-        printer->Print(
-          "if (from._has_bits_[$index$ / 32] & (0xffu << ($index$ % 32))) {\n",
-          "index", SimpleItoa(field->index()));
-        printer->Indent();
       }
 
       last_index = i;
 
-      printer->Print(
-        "if (from.has_$name$()) {\n",
-        "name", FieldName(field));
-      printer->Indent();
+      bool have_enclosing_if = false;
+      if (HasFieldPresence(descriptor_->file())) {
+        printer->Print(
+          "if (from.has_$name$()) {\n",
+          "name", FieldName(field));
+        printer->Indent();
+        have_enclosing_if = true;
+      } else {
+        // Merge semantics without true field presence: primitive fields are
+        // merged only if non-zero (numeric) or non-empty (string).
+        have_enclosing_if = EmitFieldNonDefaultCondition(
+            printer, "from.", field);
+      }
 
       field_generators_.get(field).GenerateMergingCode(printer);
 
-      printer->Outdent();
-      printer->Print("}\n");
+      if (have_enclosing_if) {
+        printer->Outdent();
+        printer->Print("}\n");
+      }
     }
   }
 
-  if (last_index >= 0) {
+  if (HasFieldPresence(descriptor_->file()) &&
+      last_index >= 0) {
     printer->Outdent();
     printer->Print("}\n");
   }
@@ -1921,12 +2331,16 @@ GenerateMergeFrom(io::Printer* printer) {
     printer->Print("_extensions_.MergeFrom(from._extensions_);\n");
   }
 
-  if (UseUnknownFieldSet(descriptor_->file())) {
-    printer->Print(
-      "mutable_unknown_fields()->MergeFrom(from.unknown_fields());\n");
-  } else {
-    printer->Print(
-      "mutable_unknown_fields()->append(from.unknown_fields());\n");
+  if (PreserveUnknownFields(descriptor_)) {
+    if (UseUnknownFieldSet(descriptor_->file())) {
+      printer->Print(
+        "if (from._internal_metadata_.have_unknown_fields()) {\n"
+        "  mutable_unknown_fields()->MergeFrom(from.unknown_fields());\n"
+        "}\n");
+    } else {
+      printer->Print(
+        "mutable_unknown_fields()->append(from.unknown_fields());\n");
+    }
   }
 
   printer->Outdent();
@@ -2171,24 +2585,33 @@ GenerateMergeFromCodedStream(io::Printer* printer) {
       }
     }
     printer->Print(") {\n");
-    if (UseUnknownFieldSet(descriptor_->file())) {
-      PrintHandlingOptionalStaticInitializers(
-        descriptor_->file(), printer,
-        // With static initializers.
-        "  DO_(_extensions_.ParseField(tag, input, default_instance_,\n"
-        "                              mutable_unknown_fields()));\n",
-        // Without.
-        "  DO_(_extensions_.ParseField(tag, input, &default_instance(),\n"
-        "                              mutable_unknown_fields()));\n");
+    if (PreserveUnknownFields(descriptor_)) {
+      if (UseUnknownFieldSet(descriptor_->file())) {
+        PrintHandlingOptionalStaticInitializers(
+          descriptor_->file(), printer,
+          // With static initializers.
+          "  DO_(_extensions_.ParseField(tag, input, default_instance_,\n"
+          "                              mutable_unknown_fields()));\n",
+          // Without.
+          "  DO_(_extensions_.ParseField(tag, input, &default_instance(),\n"
+          "                              mutable_unknown_fields()));\n");
+      } else {
+        PrintHandlingOptionalStaticInitializers(
+          descriptor_->file(), printer,
+          // With static initializers.
+          "  DO_(_extensions_.ParseField(tag, input, default_instance_,\n"
+          "                              &unknown_fields_stream));\n",
+          // Without.
+          "  DO_(_extensions_.ParseField(tag, input, &default_instance(),\n"
+          "                              &unknown_fields_stream));\n");
+      }
     } else {
       PrintHandlingOptionalStaticInitializers(
         descriptor_->file(), printer,
         // With static initializers.
-        "  DO_(_extensions_.ParseField(tag, input, default_instance_,\n"
-        "                              &unknown_fields_stream));\n",
+        "  DO_(_extensions_.ParseField(tag, input, default_instance_);\n",
         // Without.
-        "  DO_(_extensions_.ParseField(tag, input, &default_instance(),\n"
-        "                              &unknown_fields_stream));\n");
+        "  DO_(_extensions_.ParseField(tag, input, &default_instance());\n");
     }
     printer->Print(
       "  continue;\n"
@@ -2196,14 +2619,19 @@ GenerateMergeFromCodedStream(io::Printer* printer) {
   }
 
   // We really don't recognize this tag.  Skip it.
-  if (UseUnknownFieldSet(descriptor_->file())) {
-    printer->Print(
-      "DO_(::google::protobuf::internal::WireFormat::SkipField(\n"
-      "      input, tag, mutable_unknown_fields()));\n");
+  if (PreserveUnknownFields(descriptor_)) {
+    if (UseUnknownFieldSet(descriptor_->file())) {
+      printer->Print(
+        "DO_(::google::protobuf::internal::WireFormat::SkipField(\n"
+        "      input, tag, mutable_unknown_fields()));\n");
+    } else {
+      printer->Print(
+        "DO_(::google::protobuf::internal::WireFormatLite::SkipField(\n"
+        "    input, tag, &unknown_fields_stream));\n");
+    }
   } else {
     printer->Print(
-      "DO_(::google::protobuf::internal::WireFormatLite::SkipField(\n"
-      "    input, tag, &unknown_fields_stream));\n");
+      "DO_(::google::protobuf::internal::WireFormatLite::SkipField(input, tag));\n");
   }
 
   if (descriptor_->field_count() > 0) {
@@ -2232,11 +2660,15 @@ void MessageGenerator::GenerateSerializeOneField(
     io::Printer* printer, const FieldDescriptor* field, bool to_array) {
   PrintFieldComment(printer, field);
 
-  if (!field->is_repeated()) {
+  bool have_enclosing_if = false;
+  if (!field->is_repeated() && HasFieldPresence(descriptor_->file())) {
     printer->Print(
       "if (has_$name$()) {\n",
       "name", FieldName(field));
     printer->Indent();
+    have_enclosing_if = true;
+  } else if (!HasFieldPresence(descriptor_->file())) {
+    have_enclosing_if = EmitFieldNonDefaultCondition(printer, "this->", field);
   }
 
   if (to_array) {
@@ -2246,7 +2678,7 @@ void MessageGenerator::GenerateSerializeOneField(
     field_generators_.get(field).GenerateSerializeWithCachedSizes(printer);
   }
 
-  if (!field->is_repeated()) {
+  if (have_enclosing_if) {
     printer->Outdent();
     printer->Print("}\n");
   }
@@ -2386,28 +2818,69 @@ GenerateSerializeWithCachedSizesBody(io::Printer* printer, bool to_array) {
     }
   }
 
-  if (UseUnknownFieldSet(descriptor_->file())) {
-    printer->Print("if (!unknown_fields().empty()) {\n");
-    printer->Indent();
-    if (to_array) {
+  if (PreserveUnknownFields(descriptor_)) {
+    if (UseUnknownFieldSet(descriptor_->file())) {
+      printer->Print("if (_internal_metadata_.have_unknown_fields()) {\n");
+      printer->Indent();
+      if (to_array) {
+        printer->Print(
+          "target = "
+              "::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(\n"
+          "    unknown_fields(), target);\n");
+      } else {
+        printer->Print(
+          "::google::protobuf::internal::WireFormat::SerializeUnknownFields(\n"
+          "    unknown_fields(), output);\n");
+      }
+      printer->Outdent();
+
       printer->Print(
-        "target = "
-            "::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(\n"
-        "    unknown_fields(), target);\n");
+        "}\n");
     } else {
       printer->Print(
-        "::google::protobuf::internal::WireFormat::SerializeUnknownFields(\n"
-        "    unknown_fields(), output);\n");
+        "output->WriteRaw(unknown_fields().data(),\n"
+        "                 unknown_fields().size());\n");
     }
-    printer->Outdent();
+  }
+}
 
-    printer->Print(
-      "}\n");
-  } else {
-    printer->Print(
-      "output->WriteRaw(unknown_fields().data(),\n"
-      "                 unknown_fields().size());\n");
+static vector<uint32> RequiredFieldsBitMask(const Descriptor* desc) {
+  vector<uint32> result;
+  uint32 mask = 0;
+  for (int i = 0; i < desc->field_count(); i++) {
+    if (i > 0 && i % 32 == 0) {
+      result.push_back(mask);
+      mask = 0;
+    }
+    if (desc->field(i)->is_required()) {
+      mask |= (1 << (i & 31));
+    }
+  }
+  if (mask != 0) {
+    result.push_back(mask);
   }
+  return result;
+}
+
+// Create an expression that evaluates to
+//  "for all i, (_has_bits_[i] & masks[i]) == masks[i]"
+// masks is allowed to be shorter than _has_bits_, but at least one element of
+// masks must be non-zero.
+static string ConditionalToCheckBitmasks(const vector<uint32>& masks) {
+  vector<string> parts;
+  for (int i = 0; i < masks.size(); i++) {
+    if (masks[i] == 0) continue;
+    char buffer[kFastToBufferSize];
+    FastHex32ToBuffer(masks[i], buffer);
+    string m = StrCat("0x", buffer);
+    // Each xor evaluates to 0 if the expected bits are present.
+    parts.push_back(StrCat("((_has_bits_[", i, "] & ", m, ") ^ ", m, ")"));
+  }
+  GOOGLE_CHECK(!parts.empty());
+  // If we have multiple parts, each expected to be 0, then bitwise-or them.
+  string result = parts.size() == 1 ? parts[0] :
+      StrCat("(", Join(parts, "\n       | "), ")");
+  return result + " == 0";
 }
 
 void MessageGenerator::
@@ -2420,8 +2893,10 @@ GenerateByteSize(io::Printer* printer) {
       "classname", classname_);
     GOOGLE_CHECK(UseUnknownFieldSet(descriptor_->file()));
     printer->Print(
+      "if (_internal_metadata_.have_unknown_fields()) {\n"
       "  total_size += ::google::protobuf::internal::WireFormat::\n"
-      "      ComputeUnknownMessageSetItemsSize(unknown_fields());\n");
+      "      ComputeUnknownMessageSetItemsSize(unknown_fields());\n"
+      "}\n");
     printer->Print(
       "  GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();\n"
       "  _cached_size_ = total_size;\n"
@@ -2431,6 +2906,33 @@ GenerateByteSize(io::Printer* printer) {
     return;
   }
 
+  if (num_required_fields_ > 1 && HasFieldPresence(descriptor_->file())) {
+    // Emit a function (rarely used, we hope) that handles the required fields
+    // by checking for each one individually.
+    printer->Print(
+        "int $classname$::RequiredFieldsByteSizeFallback() const {\n",
+        "classname", classname_);
+    printer->Indent();
+    printer->Print("int total_size = 0;\n");
+    for (int i = 0; i < descriptor_->field_count(); i++) {
+      const FieldDescriptor* field = descriptor_->field(i);
+      if (field->is_required()) {
+        printer->Print("\n"
+                       "if (has_$name$()) {\n",
+                       "name", FieldName(field));
+        printer->Indent();
+        PrintFieldComment(printer, field);
+        field_generators_.get(field).GenerateByteSize(printer);
+        printer->Outdent();
+        printer->Print("}\n");
+      }
+    }
+    printer->Print("\n"
+                   "return total_size;\n");
+    printer->Outdent();
+    printer->Print("}\n");
+  }
+
   printer->Print(
     "int $classname$::ByteSize() const {\n",
     "classname", classname_);
@@ -2439,45 +2941,121 @@ GenerateByteSize(io::Printer* printer) {
     "int total_size = 0;\n"
     "\n");
 
-  int last_index = -1;
+  // Handle required fields (if any).  We expect all of them to be
+  // present, so emit one conditional that checks for that.  If they are all
+  // present then the fast path executes; otherwise the slow path executes.
+  if (num_required_fields_ > 1 && HasFieldPresence(descriptor_->file())) {
+    // The fast path works if all required fields are present.
+    vector<uint32> masks_for_has_bits = RequiredFieldsBitMask(descriptor_);
+    printer->Print((string("if (") +
+                    ConditionalToCheckBitmasks(masks_for_has_bits) +
+                    ") {  // All required fields are present.\n").c_str());
+    printer->Indent();
+    for (int i = 0; i < descriptor_->field_count(); i++) {
+      const FieldDescriptor* field = descriptor_->field(i);
+      if (!field->is_required()) continue;
+      PrintFieldComment(printer, field);
+      field_generators_.get(field).GenerateByteSize(printer);
+      printer->Print("\n");
+    }
+    printer->Outdent();
+    printer->Print("} else {\n"  // the slow path
+                   "  total_size += RequiredFieldsByteSizeFallback();\n"
+                   "}\n");
+  } else {
+    // num_required_fields_ <= 1: no need to be tricky
+    for (int i = 0; i < descriptor_->field_count(); i++) {
+      const FieldDescriptor* field = descriptor_->field(i);
+      if (!field->is_required()) continue;
+      PrintFieldComment(printer, field);
+      printer->Print("if (has_$name$()) {\n",
+                     "name", FieldName(field));
+      printer->Indent();
+      field_generators_.get(field).GenerateByteSize(printer);
+      printer->Outdent();
+      printer->Print("}\n");
+    }
+  }
 
+  // Handle optional fields (worry below about repeateds, oneofs, etc.).
+  // These are handled in chunks of 8.  The first chunk is
+  // the non-requireds-non-repeateds-non-unions-non-extensions in
+  //  descriptor_->field(0), descriptor_->field(1), ... descriptor_->field(7),
+  // and the second chunk is the same for
+  //  descriptor_->field(8), descriptor_->field(9), ... descriptor_->field(15),
+  // etc.
+  hash_map<int, uint32> fields_mask_for_chunk;
   for (int i = 0; i < descriptor_->field_count(); i++) {
     const FieldDescriptor* field = descriptor_->field(i);
+    if (!field->is_required() && !field->is_repeated() &&
+        !field->containing_oneof()) {
+      fields_mask_for_chunk[i / 8] |= static_cast<uint32>(1) << (i % 32);
+    }
+  }
 
-    if (!field->is_repeated() && !field->containing_oneof()) {
+  int last_index = -1;
+  bool chunk_block_in_progress = false;
+  for (int i = 0; i < descriptor_->field_count(); i++) {
+    const FieldDescriptor* field = descriptor_->field(i);
+    if (!field->is_required() && !field->is_repeated() &&
+        !field->containing_oneof()) {
       // See above in GenerateClear for an explanation of this.
       // TODO(kenton):  Share code?  Unclear how to do so without
       //   over-engineering.
-      if ((i / 8) != (last_index / 8) ||
-          last_index < 0) {
-        if (last_index >= 0) {
+      if (i / 8 != last_index / 8 || last_index < 0) {
+        // End previous chunk, if there was one.
+        if (chunk_block_in_progress) {
           printer->Outdent();
           printer->Print("}\n");
+          chunk_block_in_progress = false;
+        }
+        // Start chunk.
+        uint32 mask = fields_mask_for_chunk[i / 8];
+        int count = popcnt(mask);
+        GOOGLE_DCHECK_GE(count, 1);
+        if (count == 1) {
+          // No "if" here because the chunk is trivial.
+        } else {
+          if (HasFieldPresence(descriptor_->file())) {
+            printer->Print(
+              "if (_has_bits_[$index$ / 32] & $mask$) {\n",
+              "index", SimpleItoa(i),
+              "mask", SimpleItoa(mask));
+            printer->Indent();
+            chunk_block_in_progress = true;
+          }
         }
-        printer->Print(
-          "if (_has_bits_[$index$ / 32] & (0xffu << ($index$ % 32))) {\n",
-          "index", SimpleItoa(field->index()));
-        printer->Indent();
       }
       last_index = i;
 
       PrintFieldComment(printer, field);
 
-      printer->Print(
-        "if (has_$name$()) {\n",
-        "name", FieldName(field));
-      printer->Indent();
+      bool have_enclosing_if = false;
+      if (HasFieldPresence(descriptor_->file())) {
+        printer->Print(
+          "if (has_$name$()) {\n",
+          "name", FieldName(field));
+        printer->Indent();
+        have_enclosing_if = true;
+      } else {
+        // Without field presence: field is serialized only if it has a
+        // non-default value.
+        have_enclosing_if = EmitFieldNonDefaultCondition(
+            printer, "this->", field);
+      }
 
       field_generators_.get(field).GenerateByteSize(printer);
 
-      printer->Outdent();
-      printer->Print(
-        "}\n"
-        "\n");
+      if (have_enclosing_if) {
+        printer->Outdent();
+        printer->Print(
+          "}\n"
+          "\n");
+      }
     }
   }
 
-  if (last_index >= 0) {
+  if (chunk_block_in_progress) {
     printer->Outdent();
     printer->Print("}\n");
   }
@@ -2532,19 +3110,19 @@ GenerateByteSize(io::Printer* printer) {
       "\n");
   }
 
-  if (UseUnknownFieldSet(descriptor_->file())) {
-    printer->Print("if (!unknown_fields().empty()) {\n");
-    printer->Indent();
-    printer->Print(
-      "total_size +=\n"
-      "  ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(\n"
-      "    unknown_fields());\n");
-    printer->Outdent();
-    printer->Print("}\n");
-  } else {
-    printer->Print(
-      "total_size += unknown_fields().size();\n"
-      "\n");
+  if (PreserveUnknownFields(descriptor_)) {
+    if (UseUnknownFieldSet(descriptor_->file())) {
+      printer->Print(
+        "if (_internal_metadata_.have_unknown_fields()) {\n"
+        "  total_size +=\n"
+        "    ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(\n"
+        "      unknown_fields());\n"
+        "}\n");
+    } else {
+      printer->Print(
+        "total_size += unknown_fields().size();\n"
+        "\n");
+    }
   }
 
   // We update _cached_size_ even though this is a const method.  In theory,
@@ -2569,27 +3147,29 @@ GenerateIsInitialized(io::Printer* printer) {
     "classname", classname_);
   printer->Indent();
 
-  // Check that all required fields in this message are set.  We can do this
-  // most efficiently by checking 32 "has bits" at a time.
-  int has_bits_array_size = (descriptor_->field_count() + 31) / 32;
-  for (int i = 0; i < has_bits_array_size; i++) {
-    uint32 mask = 0;
-    for (int bit = 0; bit < 32; bit++) {
-      int index = i * 32 + bit;
-      if (index >= descriptor_->field_count()) break;
-      const FieldDescriptor* field = descriptor_->field(index);
-
-      if (field->is_required()) {
-        mask |= 1 << bit;
+  if (HasFieldPresence(descriptor_->file())) {
+    // Check that all required fields in this message are set.  We can do this
+    // most efficiently by checking 32 "has bits" at a time.
+    int has_bits_array_size = (descriptor_->field_count() + 31) / 32;
+    for (int i = 0; i < has_bits_array_size; i++) {
+      uint32 mask = 0;
+      for (int bit = 0; bit < 32; bit++) {
+        int index = i * 32 + bit;
+        if (index >= descriptor_->field_count()) break;
+        const FieldDescriptor* field = descriptor_->field(index);
+
+        if (field->is_required()) {
+          mask |= 1 << bit;
+        }
       }
-    }
 
-    if (mask != 0) {
-      char buffer[kFastToBufferSize];
-      printer->Print(
-        "if ((_has_bits_[$i$] & 0x$mask$) != 0x$mask$) return false;\n",
-        "i", SimpleItoa(i),
-        "mask", FastHex32ToBuffer(mask, buffer));
+      if (mask != 0) {
+        char buffer[kFastToBufferSize];
+        printer->Print(
+          "if ((_has_bits_[$i$] & 0x$mask$) != 0x$mask$) return false;\n",
+          "i", SimpleItoa(i),
+          "mask", FastHex32ToBuffer(mask, buffer));
+      }
     }
   }
 
@@ -2607,7 +3187,7 @@ GenerateIsInitialized(io::Printer* printer) {
           "name", FieldName(field));
       } else {
         if (field->options().weak()) {
-          // For weak fields, use the data member (google::protobuf::Message*) instead
+          // For weak fields, use the data member (::google::protobuf::Message*) instead
           // of the getter to avoid a link dependency on the weak message type
           // which is only forward declared.
           printer->Print(
diff --git a/src/google/protobuf/compiler/cpp/cpp_message.h b/src/google/protobuf/compiler/cpp/cpp_message.h
index bfd3cec1..a781c234 100644
--- a/src/google/protobuf/compiler/cpp/cpp_message.h
+++ b/src/google/protobuf/compiler/cpp/cpp_message.h
@@ -36,6 +36,9 @@
 #define GOOGLE_PROTOBUF_COMPILER_CPP_MESSAGE_H__
 
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <string>
 #include <vector>
 #include <google/protobuf/compiler/cpp/cpp_field.h>
@@ -58,8 +61,7 @@ class ExtensionGenerator;      // extension.h
 class MessageGenerator {
  public:
   // See generator.cc for the meaning of dllexport_decl.
-  explicit MessageGenerator(const Descriptor* descriptor,
-                            const Options& options);
+  MessageGenerator(const Descriptor* descriptor, const Options& options);
   ~MessageGenerator();
 
   // Header stuff.
@@ -130,6 +132,8 @@ class MessageGenerator {
   void GenerateSharedConstructorCode(io::Printer* printer);
   // Generate the shared destructor code.
   void GenerateSharedDestructorCode(io::Printer* printer);
+  // Generate the arena-specific destructor code.
+  void GenerateArenaDestructorCode(io::Printer* printer);
 
   // Generate standard Message methods.
   void GenerateClear(io::Printer* printer);
@@ -162,6 +166,7 @@ class MessageGenerator {
   scoped_array<scoped_ptr<MessageGenerator> > nested_generators_;
   scoped_array<scoped_ptr<EnumGenerator> > enum_generators_;
   scoped_array<scoped_ptr<ExtensionGenerator> > extension_generators_;
+  int num_required_fields_;
   bool uses_string_;
 
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MessageGenerator);
diff --git a/src/google/protobuf/compiler/cpp/cpp_message_field.cc b/src/google/protobuf/compiler/cpp/cpp_message_field.cc
index 6ac15a5a..da1ec60b 100644
--- a/src/google/protobuf/compiler/cpp/cpp_message_field.cc
+++ b/src/google/protobuf/compiler/cpp/cpp_message_field.cc
@@ -86,6 +86,12 @@ GenerateAccessorDeclarations(io::Printer* printer) const {
     "inline $type$* mutable_$name$()$deprecation$;\n"
     "inline $type$* $release_name$()$deprecation$;\n"
     "inline void set_allocated_$name$($type$* $name$)$deprecation$;\n");
+  if (SupportsArenas(descriptor_)) {
+    printer->Print(variables_,
+      "inline $type$* unsafe_arena_release_$name$()$deprecation$;\n"
+      "inline void unsafe_arena_set_allocated_$name$(\n"
+      "    $type$* $name$)$deprecation$;\n");
+  }
 }
 
 void MessageFieldGenerator::
@@ -101,36 +107,157 @@ GenerateInlineAccessorDefinitions(io::Printer* printer) const {
     // Without.
     "  return $name$_ != NULL ? *$name$_ : *default_instance().$name$_;\n");
 
-  printer->Print(variables_,
-    "}\n"
-    "inline $type$* $classname$::mutable_$name$() {\n"
-    "  set_has_$name$();\n"
-    "  if ($name$_ == NULL) $name$_ = new $type$;\n"
-    "  // @@protoc_insertion_point(field_mutable:$full_name$)\n"
-    "  return $name$_;\n"
-    "}\n"
-    "inline $type$* $classname$::$release_name$() {\n"
-    "  clear_has_$name$();\n"
-    "  $type$* temp = $name$_;\n"
-    "  $name$_ = NULL;\n"
-    "  return temp;\n"
-    "}\n"
-    "inline void $classname$::set_allocated_$name$($type$* $name$) {\n"
-    "  delete $name$_;\n"
-    "  $name$_ = $name$;\n"
-    "  if ($name$) {\n"
-    "    set_has_$name$();\n"
-    "  } else {\n"
-    "    clear_has_$name$();\n"
-    "  }\n"
-    "  // @@protoc_insertion_point(field_set_allocated:$full_name$)\n"
-    "}\n");
+  if (SupportsArenas(descriptor_)) {
+    printer->Print(variables_,
+      "}\n"
+      "inline $type$* $classname$::mutable_$name$() {\n"
+      "  $set_hasbit$\n"
+      "  if ($name$_ == NULL) {\n");
+    if (SupportsArenas(descriptor_->message_type())) {
+      printer->Print(variables_,
+      "    $name$_ = ::google::protobuf::Arena::CreateMessage< $type$ >(\n"
+      "        GetArenaNoVirtual());\n");
+    } else {
+      printer->Print(variables_,
+       "    $name$_ = ::google::protobuf::Arena::Create< $type$ >(\n"
+       "        GetArenaNoVirtual());\n");
+    }
+    printer->Print(variables_, "  }\n"
+      "  // @@protoc_insertion_point(field_mutable:$full_name$)\n"
+      "  return $name$_;\n"
+      "}\n"
+      "inline $type$* $classname$::$release_name$() {\n"
+      "  $clear_hasbit$\n"
+      "  if (GetArenaNoVirtual() != NULL) {\n"
+      "    if ($name$_ == NULL) {\n"
+      "      return NULL;\n"
+      "    } else {\n"
+      "      $type$* temp = new $type$;\n"
+      "      temp->MergeFrom(*$name$_);\n"
+      "      $name$_ = NULL;\n"
+      "      return temp;\n"
+      "    }\n"
+      "  } else {\n"
+      "    $type$* temp = $name$_;\n"
+      "    $name$_ = NULL;\n"
+      "    return temp;\n"
+      "  }\n"
+      "}\n"
+      "inline $type$* $classname$::unsafe_arena_release_$name$() {\n"
+      "  $clear_hasbit$\n"
+      "  $type$* temp = $name$_;\n"
+      "  $name$_ = NULL;\n"
+      "  return temp;\n"
+      "}\n"
+      "inline void $classname$::set_allocated_$name$($type$* $name$) {\n"
+      "  if (GetArenaNoVirtual() == NULL) {\n"
+      "    delete $name$_;\n"
+      "  }\n"
+      "  if ($name$ != NULL) {\n");
+    if (SupportsArenas(descriptor_->message_type())) {
+      // If we're on an arena and the incoming message is not, simply Own() it
+      // rather than copy to the arena -- either way we need a heap dealloc,
+      // so we might as well defer it. Otherwise, if incoming message is on a
+      // different ownership domain (specific arena, or the heap) than we are,
+      // copy to our arena (or heap, as the case may be).
+      printer->Print(variables_,
+        "    if (GetArenaNoVirtual() != NULL && \n"
+        "        ::google::protobuf::Arena::GetArena($name$) == NULL) {\n"
+        "      GetArenaNoVirtual()->Own($name$);\n"
+        "    } else if (GetArenaNoVirtual() !=\n"
+        "               ::google::protobuf::Arena::GetArena($name$)) {\n"
+        "      $type$* new_$name$ = \n"
+        "            ::google::protobuf::Arena::CreateMessage< $type$ >(\n"
+        "            GetArenaNoVirtual());\n"
+        "      new_$name$->CopyFrom(*$name$);\n"
+        "      $name$ = new_$name$;\n"
+        "    }\n");
+    } else {
+      printer->Print(variables_,
+        "    if (GetArenaNoVirtual() != NULL) {\n"
+        "      GetArenaNoVirtual()->Own($name$);\n"
+        "    }\n");
+    }
+
+    printer->Print(variables_,
+      "  }\n"
+      "  $name$_ = $name$;\n"
+      "  if ($name$) {\n"
+      "    $set_hasbit$\n"
+      "  } else {\n"
+      "    $clear_hasbit$\n"
+      "  }\n"
+      "  // @@protoc_insertion_point(field_set_allocated:$full_name$)\n"
+      "}\n"
+      "inline void $classname$::unsafe_arena_set_allocated_$name$(\n"
+      "    $type$* $name$) {\n"
+      // If we're not on an arena, free whatever we were holding before.
+      // (If we are on arena, we can just forget the earlier pointer.)
+      "  if (GetArenaNoVirtual() == NULL) {\n"
+      "    delete $name$_;\n"
+      "  }\n"
+      "  $name$_ = $name$;\n"
+      "  if ($name$) {\n"
+      "    $set_hasbit$\n"
+      "  } else {\n"
+      "    $clear_hasbit$\n"
+      "  }\n"
+      "  // @@protoc_insertion_point(field_unsafe_arena_set_allocated"
+      ":$full_name$)\n"
+      "}\n");
+  } else {
+    printer->Print(variables_,
+      "}\n"
+      "inline $type$* $classname$::mutable_$name$() {\n"
+      "  $set_hasbit$\n"
+      "  if ($name$_ == NULL) {\n"
+      "    $name$_ = new $type$;\n"
+      "  }\n"
+      "  // @@protoc_insertion_point(field_mutable:$full_name$)\n"
+      "  return $name$_;\n"
+      "}\n"
+      "inline $type$* $classname$::$release_name$() {\n"
+      "  $clear_hasbit$\n"
+      "  $type$* temp = $name$_;\n"
+      "  $name$_ = NULL;\n"
+      "  return temp;\n"
+      "}\n"
+      "inline void $classname$::set_allocated_$name$($type$* $name$) {\n"
+      "  delete $name$_;\n");
+
+    if (SupportsArenas(descriptor_->message_type())) {
+      printer->Print(variables_,
+      "  if ($name$ != NULL && $name$->GetArena() != NULL) {\n"
+      "    $type$* new_$name$ = new $type$;\n"
+      "    new_$name$->CopyFrom(*$name$);\n"
+      "    $name$ = new_$name$;\n"
+      "  }\n");
+    }
+
+    printer->Print(variables_,
+      "  $name$_ = $name$;\n"
+      "  if ($name$) {\n"
+      "    $set_hasbit$\n"
+      "  } else {\n"
+      "    $clear_hasbit$\n"
+      "  }\n"
+      "  // @@protoc_insertion_point(field_set_allocated:$full_name$)\n"
+      "}\n");
+  }
 }
 
 void MessageFieldGenerator::
 GenerateClearingCode(io::Printer* printer) const {
-  printer->Print(variables_,
-    "if ($name$_ != NULL) $name$_->$type$::Clear();\n");
+  if (!HasFieldPresence(descriptor_->file())) {
+    // If we don't have has-bits, message presence is indicated only by ptr !=
+    // NULL. Thus on clear, we need to delete the object.
+    printer->Print(variables_,
+      "if ($name$_ != NULL) delete $name$_;\n"
+      "$name$_ = NULL;\n");
+  } else {
+    printer->Print(variables_,
+      "if ($name$_ != NULL) $name$_->$type$::Clear();\n");
+  }
 }
 
 void MessageFieldGenerator::
@@ -198,43 +325,165 @@ MessageOneofFieldGenerator::~MessageOneofFieldGenerator() {}
 
 void MessageOneofFieldGenerator::
 GenerateInlineAccessorDefinitions(io::Printer* printer) const {
-  printer->Print(variables_,
-    "inline const $type$& $classname$::$name$() const {\n"
-    "  return has_$name$() ? *$oneof_prefix$$name$_\n"
-    "                      : $type$::default_instance();\n"
-    "}\n"
-    "inline $type$* $classname$::mutable_$name$() {\n"
-    "  if (!has_$name$()) {\n"
-    "    clear_$oneof_name$();\n"
-    "    set_has_$name$();\n"
-    "    $oneof_prefix$$name$_ = new $type$;\n"
-    "  }\n"
-    "  return $oneof_prefix$$name$_;\n"
-    "}\n"
-    "inline $type$* $classname$::$release_name$() {\n"
-    "  if (has_$name$()) {\n"
-    "    clear_has_$oneof_name$();\n"
-    "    $type$* temp = $oneof_prefix$$name$_;\n"
-    "    $oneof_prefix$$name$_ = NULL;\n"
-    "    return temp;\n"
-    "  } else {\n"
-    "    return NULL;\n"
-    "  }\n"
-    "}\n"
-    "inline void $classname$::set_allocated_$name$($type$* $name$) {\n"
-    "  clear_$oneof_name$();\n"
-    "  if ($name$) {\n"
-    "    set_has_$name$();\n"
-    "    $oneof_prefix$$name$_ = $name$;\n"
-    "  }\n"
-    "}\n");
+  if (SupportsArenas(descriptor_)) {
+    printer->Print(variables_,
+      "inline const $type$& $classname$::$name$() const {\n"
+      "  // @@protoc_insertion_point(field_get:$full_name$)\n"
+      "  return has_$name$() ? *$oneof_prefix$$name$_\n"
+      "                      : $type$::default_instance();\n"
+      "}\n"
+      "inline $type$* $classname$::mutable_$name$() {\n"
+      "  if (!has_$name$()) {\n"
+      "    clear_$oneof_name$();\n"
+      "    set_has_$name$();\n");
+    if (SupportsArenas(descriptor_->message_type())) {
+      printer->Print(variables_,
+         "    $oneof_prefix$$name$_ = \n"
+         "      ::google::protobuf::Arena::CreateMessage< $type$ >(\n"
+         "      GetArenaNoVirtual());\n");
+    } else {
+      printer->Print(variables_,
+         "    $oneof_prefix$$name$_ = \n"
+         "      ::google::protobuf::Arena::Create< $type$ >(\n"
+         "      GetArenaNoVirtual());\n");
+    }
+    printer->Print(variables_,
+      "  }\n"
+      "  // @@protoc_insertion_point(field_mutable:$full_name$)\n"
+      "  return $oneof_prefix$$name$_;\n"
+      "}\n"
+      "inline $type$* $classname$::$release_name$() {\n"
+      "  if (has_$name$()) {\n"
+      "    clear_has_$oneof_name$();\n"
+      "    if (GetArenaNoVirtual() != NULL) {\n"
+      // N.B.: safe to use the underlying field pointer here because we are sure
+      // that it is non-NULL (because has_$name$() returned true).
+      "      $type$* temp = new $type$;\n"
+      "      temp->MergeFrom(*$oneof_prefix$$name$_);\n"
+      "      $oneof_prefix$$name$_ = NULL;\n"
+      "      return temp;\n"
+      "    } else {\n"
+      "      $type$* temp = $oneof_prefix$$name$_;\n"
+      "      $oneof_prefix$$name$_ = NULL;\n"
+      "      return temp;\n"
+      "    }\n"
+      "  } else {\n"
+      "    return NULL;\n"
+      "  }\n"
+      "}\n"
+      "inline $type$* $classname$::unsafe_arena_release_$name$() {\n"
+      "  if (has_$name$()) {\n"
+      "    clear_has_$oneof_name$();\n"
+      "    $type$* temp = $oneof_prefix$$name$_;\n"
+      "    $oneof_prefix$$name$_ = NULL;\n"
+      "    return temp;\n"
+      "  } else {\n"
+      "    return NULL;\n"
+      "  }\n"
+      "}\n"
+      "inline void $classname$::set_allocated_$name$($type$* $name$) {\n"
+      "  clear_$oneof_name$();\n"
+      "  if ($name$) {\n");
+
+    if (SupportsArenas(descriptor_->message_type())) {
+      printer->Print(variables_,
+        // If incoming message is on the heap and we are on an arena, just Own()
+        // it (see above). If it's on a different arena than we are or one of us
+        // is on the heap, we make a copy to our arena/heap.
+        "    if (GetArenaNoVirtual() != NULL &&\n"
+        "        ::google::protobuf::Arena::GetArena($name$) == NULL) {\n"
+        "      GetArenaNoVirtual()->Own($name$);\n"
+        "    } else if (GetArenaNoVirtual() !=\n"
+        "               ::google::protobuf::Arena::GetArena($name$)) {\n"
+        "      $type$* new_$name$ = \n"
+        "          ::google::protobuf::Arena::CreateMessage< $type$ >(\n"
+        "          GetArenaNoVirtual());\n"
+        "      new_$name$->CopyFrom(*$name$);\n"
+        "      $name$ = new_$name$;\n"
+        "    }\n");
+    } else {
+      printer->Print(variables_,
+        "    if (GetArenaNoVirtual() != NULL) {\n"
+        "      GetArenaNoVirtual()->Own($name$);\n"
+        "    }\n");
+    }
+
+    printer->Print(variables_,
+      "    set_has_$name$();\n"
+      "    $oneof_prefix$$name$_ = $name$;\n"
+      "  }\n"
+      "  // @@protoc_insertion_point(field_set_allocated:$full_name$)\n"
+      "}\n"
+      "inline void $classname$::unsafe_arena_set_allocated_$name$("
+      "$type$* $name$) {\n"
+      // We rely on the oneof clear method to free the earlier contents of this
+      // oneof. We can directly use the pointer we're given to set the new
+      // value.
+      "  clear_$oneof_name$();\n"
+      "  if ($name$) {\n"
+      "    set_has_$name$();\n"
+      "    $oneof_prefix$$name$_ = $name$;\n"
+      "  }\n"
+      "  // @@protoc_insertion_point(field_unsafe_arena_set_allocated:"
+      "$full_name$)\n"
+      "}\n");
+  } else {
+    printer->Print(variables_,
+      "inline const $type$& $classname$::$name$() const {\n"
+      "  // @@protoc_insertion_point(field_get:$full_name$)\n"
+      "  return has_$name$() ? *$oneof_prefix$$name$_\n"
+      "                      : $type$::default_instance();\n"
+      "}\n"
+      "inline $type$* $classname$::mutable_$name$() {\n"
+      "  if (!has_$name$()) {\n"
+      "    clear_$oneof_name$();\n"
+      "    set_has_$name$();\n"
+      "    $oneof_prefix$$name$_ = new $type$;\n"
+      "  }\n"
+      "  // @@protoc_insertion_point(field_mutable:$full_name$)\n"
+      "  return $oneof_prefix$$name$_;\n"
+      "}\n"
+      "inline $type$* $classname$::$release_name$() {\n"
+      "  if (has_$name$()) {\n"
+      "    clear_has_$oneof_name$();\n"
+      "    $type$* temp = $oneof_prefix$$name$_;\n"
+      "    $oneof_prefix$$name$_ = NULL;\n"
+      "    return temp;\n"
+      "  } else {\n"
+      "    return NULL;\n"
+      "  }\n"
+      "}\n"
+      "inline void $classname$::set_allocated_$name$($type$* $name$) {\n"
+      "  clear_$oneof_name$();\n"
+      "  if ($name$) {\n");
+    if (SupportsArenas(descriptor_->message_type())) {
+      printer->Print(variables_,
+        "    if ($name$->GetArena() != NULL) {\n"
+        "      $type$* new_$name$ = new $type$;\n"
+        "      new_$name$->CopyFrom(*$name$);\n"
+        "      $name$ = new_$name$;\n"
+        "    }\n");
+    }
+    printer->Print(variables_,
+      "    set_has_$name$();\n"
+      "    $oneof_prefix$$name$_ = $name$;\n"
+      "  }\n"
+      "  // @@protoc_insertion_point(field_set_allocated:$full_name$)\n"
+      "}\n");
+  }
 }
 
 void MessageOneofFieldGenerator::
 GenerateClearingCode(io::Printer* printer) const {
-  // if it is the active field, it cannot be NULL.
-  printer->Print(variables_,
-    "delete $oneof_prefix$$name$_;\n");
+  if (SupportsArenas(descriptor_)) {
+    printer->Print(variables_,
+      "if (GetArenaNoVirtual() == NULL) {\n"
+      "  delete $oneof_prefix$$name$_;\n"
+      "}\n");
+  } else {
+    printer->Print(variables_,
+      "delete $oneof_prefix$$name$_;\n");
+  }
 }
 
 void MessageOneofFieldGenerator::
@@ -318,7 +567,7 @@ GenerateMergingCode(io::Printer* printer) const {
 
 void RepeatedMessageFieldGenerator::
 GenerateSwappingCode(io::Printer* printer) const {
-  printer->Print(variables_, "$name$_.Swap(&other->$name$_);\n");
+  printer->Print(variables_, "$name$_.UnsafeArenaSwap(&other->$name$_);\n");
 }
 
 void RepeatedMessageFieldGenerator::
diff --git a/src/google/protobuf/compiler/cpp/cpp_plugin_unittest.cc b/src/google/protobuf/compiler/cpp/cpp_plugin_unittest.cc
index 2dbf14ce..26cefb2e 100644
--- a/src/google/protobuf/compiler/cpp/cpp_plugin_unittest.cc
+++ b/src/google/protobuf/compiler/cpp/cpp_plugin_unittest.cc
@@ -35,6 +35,9 @@
 //   worth.
 
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 
 #include <google/protobuf/compiler/cpp/cpp_generator.h>
 #include <google/protobuf/compiler/command_line_interface.h>
@@ -69,6 +72,100 @@ class TestGenerator : public CodeGenerator {
     TryInsert("test.pb.cc", "includes", context);
     TryInsert("test.pb.cc", "namespace_scope", context);
     TryInsert("test.pb.cc", "global_scope", context);
+
+    // Check field accessors for an optional int32:
+    TryInsert("test.pb.h", "field_get:foo.Bar.optInt", context);
+    TryInsert("test.pb.h", "field_set:foo.Bar.optInt", context);
+
+    // Check field accessors for a repeated int32:
+    TryInsert("test.pb.h", "field_get:foo.Bar.repeatedInt", context);
+    TryInsert("test.pb.h", "field_set:foo.Bar.repeatedInt", context);
+
+    // Check field accessors for a required string:
+    TryInsert("test.pb.h", "field_get:foo.Bar.requiredString", context);
+    TryInsert("test.pb.h", "field_set:foo.Bar.requiredString", context);
+    TryInsert("test.pb.h", "field_set_char:foo.Bar.requiredString", context);
+    TryInsert("test.pb.h", "field_set_pointer:foo.Bar.requiredString", context);
+    TryInsert("test.pb.h", "field_mutable:foo.Bar.requiredString", context);
+    TryInsert("test.pb.h", "field_set_allocated:foo.Bar.requiredString",
+              context);
+    TryInsert("test.pb.h", "field_set_char:foo.Bar.requiredString", context);
+    TryInsert("test.pb.h", "field_set_pointer:foo.Bar.requiredString", context);
+
+    // Check field accessors for a repeated string:
+    TryInsert("test.pb.h", "field_get:foo.Bar.repeatedString", context);
+    TryInsert("test.pb.h", "field_set:foo.Bar.repeatedString", context);
+    TryInsert("test.pb.h", "field_set_char:foo.Bar.repeatedString", context);
+    TryInsert("test.pb.h", "field_set_pointer:foo.Bar.repeatedString", context);
+    TryInsert("test.pb.h", "field_mutable:foo.Bar.repeatedString", context);
+    TryInsert("test.pb.h", "field_set_char:foo.Bar.repeatedString", context);
+    TryInsert("test.pb.h", "field_set_pointer:foo.Bar.repeatedString", context);
+
+    // Check field accessors for an int inside oneof{}:
+    TryInsert("test.pb.h", "field_get:foo.Bar.oneOfInt", context);
+    TryInsert("test.pb.h", "field_set:foo.Bar.oneOfInt", context);
+
+    // Check field accessors for a string inside oneof{}:
+    TryInsert("test.pb.h", "field_get:foo.Bar.oneOfString", context);
+    TryInsert("test.pb.h", "field_set:foo.Bar.oneOfString", context);
+    TryInsert("test.pb.h", "field_set_char:foo.Bar.oneOfString", context);
+    TryInsert("test.pb.h", "field_set_pointer:foo.Bar.oneOfString", context);
+    TryInsert("test.pb.h", "field_mutable:foo.Bar.oneOfString", context);
+    TryInsert("test.pb.h", "field_set_allocated:foo.Bar.oneOfString", context);
+    TryInsert("test.pb.h", "field_set_char:foo.Bar.oneOfString", context);
+    TryInsert("test.pb.h", "field_set_pointer:foo.Bar.oneOfString", context);
+
+    // Check field accessors for an optional message:
+    TryInsert("test.pb.h", "field_get:foo.Bar.optMessage", context);
+    TryInsert("test.pb.h", "field_mutable:foo.Bar.optMessage", context);
+    TryInsert("test.pb.h", "field_set_allocated:foo.Bar.optMessage", context);
+
+    // Check field accessors for a repeated message:
+    TryInsert("test.pb.h", "field_add:foo.Bar.repeatedMessage", context);
+    TryInsert("test.pb.h", "field_get:foo.Bar.repeatedMessage", context);
+    TryInsert("test.pb.h", "field_list:foo.Bar.repeatedMessage", context);
+    TryInsert("test.pb.h", "field_mutable:foo.Bar.repeatedMessage", context);
+    TryInsert("test.pb.h", "field_mutable_list:foo.Bar.repeatedMessage",
+              context);
+
+    // Check field accessors for a message inside oneof{}:
+    TryInsert("test.pb.h", "field_get:foo.Bar.oneOfMessage", context);
+    TryInsert("test.pb.h", "field_mutable:foo.Bar.oneOfMessage", context);
+    TryInsert("test.pb.h", "field_set_allocated:foo.Bar.oneOfMessage", context);
+
+    // Check field accessors for an optional enum:
+    TryInsert("test.pb.h", "field_get:foo.Bar.optEnum", context);
+    TryInsert("test.pb.h", "field_set:foo.Bar.optEnum", context);
+
+    // Check field accessors for a repeated enum:
+    TryInsert("test.pb.h", "field_get:foo.Bar.repeatedEnum", context);
+    TryInsert("test.pb.h", "field_set:foo.Bar.repeatedEnum", context);
+    TryInsert("test.pb.h", "field_add:foo.Bar.repeatedEnum", context);
+    TryInsert("test.pb.h", "field_list:foo.Bar.repeatedEnum", context);
+    TryInsert("test.pb.h", "field_mutable_list:foo.Bar.repeatedEnum", context);
+
+    // Check field accessors for an enum inside oneof{}:
+    TryInsert("test.pb.h", "field_get:foo.Bar.oneOfEnum", context);
+    TryInsert("test.pb.h", "field_set:foo.Bar.oneOfEnum", context);
+
+    // Check field accessors for a required cord:
+    TryInsert("test.pb.h", "field_get:foo.Bar.requiredCord", context);
+    TryInsert("test.pb.h", "field_set:foo.Bar.requiredCord", context);
+    TryInsert("test.pb.h", "field_mutable:foo.Bar.requiredCord", context);
+
+    // Check field accessors for a repeated cord:
+    TryInsert("test.pb.h", "field_get:foo.Bar.repeatedCord", context);
+    TryInsert("test.pb.h", "field_set:foo.Bar.repeatedCord", context);
+    TryInsert("test.pb.h", "field_add:foo.Bar.repeatedCord", context);
+    TryInsert("test.pb.h", "field_list:foo.Bar.repeatedCord", context);
+    TryInsert("test.pb.h", "field_mutable:foo.Bar.repeatedCord", context);
+    TryInsert("test.pb.h", "field_mutable_list:foo.Bar.repeatedCord", context);
+
+    // Check field accessors for a cord inside oneof{}:
+    TryInsert("test.pb.h", "field_get:foo.Bar.oneOfCord", context);
+    TryInsert("test.pb.h", "field_set:foo.Bar.oneOfCord", context);
+    TryInsert("test.pb.h", "field_mutable:foo.Bar.oneOfCord", context);
+
     return true;
   }
 
@@ -88,8 +185,39 @@ TEST(CppPluginTest, PluginTest) {
   GOOGLE_CHECK_OK(File::SetContents(TestTempDir() + "/test.proto",
                              "syntax = \"proto2\";\n"
                              "package foo;\n"
+                             "\n"
+                             "enum Thud { VALUE = 0; }\n"
+                             "\n"
                              "message Bar {\n"
                              "  message Baz {}\n"
+                             "  optional int32 optInt = 1;\n"
+                             "  repeated int32 repeatedInt = 2;\n"
+                             "\n"
+                             "  required string requiredString = 3;\n"
+                             "  repeated string repeatedString = 4;\n"
+                             "\n"
+                             "  optional Baz optMessage = 6;\n"
+                             "  repeated Baz repeatedMessage = 7;\n"
+                             "\n"
+                             "  optional Thud optEnum = 8;\n"
+                             "  repeated Thud repeatedEnum = 9;\n"
+                             "\n"
+                             "  required string requiredCord = 10 [\n"
+                             "    ctype = CORD\n"
+                             "  ];\n"
+                             "  repeated string repeatedCord = 11 [\n"
+                             "    ctype = CORD\n"
+                             "  ];\n"
+                             "\n"
+                             "  oneof Qux {\n"
+                             "    int64 oneOfInt = 20;\n"
+                             "    string oneOfString = 21;\n"
+                             "    Baz oneOfMessage = 22;\n"
+                             "    Thud oneOfEnum = 23;"
+                             "    string oneOfCord = 24 [\n"
+                             "      ctype = CORD\n"
+                             "    ];\n"
+                             "  }\n"
                              "}\n",
                              true));
 
diff --git a/src/google/protobuf/compiler/cpp/cpp_primitive_field.cc b/src/google/protobuf/compiler/cpp/cpp_primitive_field.cc
index 44290a31..9a2c930e 100644
--- a/src/google/protobuf/compiler/cpp/cpp_primitive_field.cc
+++ b/src/google/protobuf/compiler/cpp/cpp_primitive_field.cc
@@ -129,7 +129,7 @@ GenerateInlineAccessorDefinitions(io::Printer* printer) const {
     "  return $name$_;\n"
     "}\n"
     "inline void $classname$::set_$name$($type$ value) {\n"
-    "  set_has_$name$();\n"
+    "  $set_hasbit$\n"
     "  $name$_ = value;\n"
     "  // @@protoc_insertion_point(field_set:$full_name$)\n"
     "}\n");
@@ -161,7 +161,7 @@ GenerateMergeFromCodedStream(io::Printer* printer) const {
     "DO_((::google::protobuf::internal::WireFormatLite::ReadPrimitive<\n"
     "         $type$, $wire_format_field_type$>(\n"
     "       input, &$name$_)));\n"
-    "set_has_$name$();\n");
+    "$set_hasbit$\n");
 }
 
 void PrimitiveFieldGenerator::
@@ -207,6 +207,7 @@ void PrimitiveOneofFieldGenerator::
 GenerateInlineAccessorDefinitions(io::Printer* printer) const {
   printer->Print(variables_,
     "inline $type$ $classname$::$name$() const {\n"
+    "  // @@protoc_insertion_point(field_get:$full_name$)\n"
     "  if (has_$name$()) {\n"
     "    return $oneof_prefix$$name$_;\n"
     "  }\n"
@@ -218,6 +219,7 @@ GenerateInlineAccessorDefinitions(io::Printer* printer) const {
     "    set_has_$name$();\n"
     "  }\n"
     "  $oneof_prefix$$name$_ = value;\n"
+    "  // @@protoc_insertion_point(field_set:$full_name$)\n"
     "}\n");
 }
 
@@ -330,7 +332,7 @@ GenerateMergingCode(io::Printer* printer) const {
 
 void RepeatedPrimitiveFieldGenerator::
 GenerateSwappingCode(io::Printer* printer) const {
-  printer->Print(variables_, "$name$_.Swap(&other->$name$_);\n");
+  printer->Print(variables_, "$name$_.UnsafeArenaSwap(&other->$name$_);\n");
 }
 
 void RepeatedPrimitiveFieldGenerator::
diff --git a/src/google/protobuf/compiler/cpp/cpp_string_field.cc b/src/google/protobuf/compiler/cpp/cpp_string_field.cc
index 180d236b..a2a8c81c 100644
--- a/src/google/protobuf/compiler/cpp/cpp_string_field.cc
+++ b/src/google/protobuf/compiler/cpp/cpp_string_field.cc
@@ -52,9 +52,14 @@ void SetStringVariables(const FieldDescriptor* descriptor,
   (*variables)["default"] = DefaultValue(descriptor);
   (*variables)["default_length"] =
       SimpleItoa(descriptor->default_value_string().length());
-  (*variables)["default_variable"] = descriptor->default_value_string().empty()
-      ? "&::google::protobuf::internal::GetEmptyStringAlreadyInited()"
-      : "_default_" + FieldName(descriptor) + "_";
+  string default_variable_string =
+      descriptor->default_value_string().empty()
+          ? "&::google::protobuf::internal::GetEmptyStringAlreadyInited()"
+          : "_default_" + FieldName(descriptor) + "_";
+  (*variables)["default_variable"] = default_variable_string;
+  (*variables)["default_value_init"] =
+      descriptor->default_value_string().empty()
+      ? "" : "*" + default_variable_string;
   (*variables)["pointer_type"] =
       descriptor->type() == FieldDescriptor::TYPE_BYTES ? "void" : "char";
   // NOTE: Escaped here to unblock proto1->proto2 migration.
@@ -63,6 +68,8 @@ void SetStringVariables(const FieldDescriptor* descriptor,
       SafeFunctionName(descriptor->containing_type(),
                        descriptor, "release_");
   (*variables)["full_name"] = descriptor->full_name();
+
+  (*variables)["string_piece"] = "::std::string";
 }
 
 }  // namespace
@@ -80,7 +87,19 @@ StringFieldGenerator::~StringFieldGenerator() {}
 
 void StringFieldGenerator::
 GeneratePrivateMembers(io::Printer* printer) const {
-  printer->Print(variables_, "::std::string* $name$_;\n");
+  // N.B. that we continue to use |ArenaStringPtr| instead of |string*| for
+  // string fields, even when SupportArenas(descriptor_) == false. Why?
+  // The simple answer is to avoid unmaintainable complexity. The reflection
+  // code assumes ArenaStringPtrs. These are *almost* in-memory-compatible with
+  // string*, except for the pointer tags and related ownership semantics. We
+  // could modify the runtime code to use string* for the not-supporting-arenas
+  // case, but this would require a way to detect which type of class was
+  // generated (adding overhead and complexity to GeneratedMessageReflection)
+  // and littering the runtime code paths with conditionals. It's simpler to
+  // stick with this but use lightweight accessors that assume arena == NULL.
+  // There should be very little overhead anyway because it's just a tagged
+  // pointer in-memory.
+  printer->Print(variables_, "::google::protobuf::internal::ArenaStringPtr $name$_;\n");
 }
 
 void StringFieldGenerator::
@@ -125,6 +144,12 @@ GenerateAccessorDeclarations(io::Printer* printer) const {
     "inline ::std::string* mutable_$name$()$deprecation$;\n"
     "inline ::std::string* $release_name$()$deprecation$;\n"
     "inline void set_allocated_$name$(::std::string* $name$)$deprecation$;\n");
+  if (SupportsArenas(descriptor_)) {
+    printer->Print(variables_,
+      "inline ::std::string* unsafe_arena_release_$name$()$deprecation$;\n"
+      "inline void unsafe_arena_set_allocated_$name$(\n"
+      "    ::std::string* $name$)$deprecation$;\n");
+  }
 
 
   if (descriptor_->options().ctype() != FieldOptions::STRING) {
@@ -136,74 +161,113 @@ GenerateAccessorDeclarations(io::Printer* printer) const {
 
 void StringFieldGenerator::
 GenerateInlineAccessorDefinitions(io::Printer* printer) const {
-  printer->Print(variables_,
-    "inline const ::std::string& $classname$::$name$() const {\n"
-    "  // @@protoc_insertion_point(field_get:$full_name$)\n"
-    "  return *$name$_;\n"
-    "}\n"
-    "inline void $classname$::set_$name$(const ::std::string& value) {\n"
-    "  set_has_$name$();\n"
-    "  if ($name$_ == $default_variable$) {\n"
-    "    $name$_ = new ::std::string;\n"
-    "  }\n"
-    "  $name$_->assign(value);\n"
-    "  // @@protoc_insertion_point(field_set:$full_name$)\n"
-    "}\n"
-    "inline void $classname$::set_$name$(const char* value) {\n"
-    "  set_has_$name$();\n"
-    "  if ($name$_ == $default_variable$) {\n"
-    "    $name$_ = new ::std::string;\n"
-    "  }\n"
-    "  $name$_->assign(value);\n"
-    "  // @@protoc_insertion_point(field_set_char:$full_name$)\n"
-    "}\n"
-    "inline "
-    "void $classname$::set_$name$(const $pointer_type$* value, size_t size) {\n"
-    "  set_has_$name$();\n"
-    "  if ($name$_ == $default_variable$) {\n"
-    "    $name$_ = new ::std::string;\n"
-    "  }\n"
-    "  $name$_->assign(reinterpret_cast<const char*>(value), size);\n"
-    "  // @@protoc_insertion_point(field_set_pointer:$full_name$)\n"
-    "}\n"
-    "inline ::std::string* $classname$::mutable_$name$() {\n"
-    "  set_has_$name$();\n"
-    "  if ($name$_ == $default_variable$) {\n");
-  if (descriptor_->default_value_string().empty()) {
+  if (SupportsArenas(descriptor_)) {
     printer->Print(variables_,
-      "    $name$_ = new ::std::string;\n");
+      "inline const ::std::string& $classname$::$name$() const {\n"
+      "  // @@protoc_insertion_point(field_get:$full_name$)\n"
+      "  return $name$_.Get($default_variable$);\n"
+      "}\n"
+      "inline void $classname$::set_$name$(const ::std::string& value) {\n"
+      "  $set_hasbit$\n"
+      "  $name$_.Set($default_variable$, value, GetArenaNoVirtual());\n"
+      "  // @@protoc_insertion_point(field_set:$full_name$)\n"
+      "}\n"
+      "inline void $classname$::set_$name$(const char* value) {\n"
+      "  $set_hasbit$\n"
+      "  $name$_.Set($default_variable$, $string_piece$(value),\n"
+      "              GetArenaNoVirtual());\n"
+      "  // @@protoc_insertion_point(field_set_char:$full_name$)\n"
+      "}\n"
+      "inline "
+      "void $classname$::set_$name$(const $pointer_type$* value,\n"
+      "    size_t size) {\n"
+      "  $set_hasbit$\n"
+      "  $name$_.Set($default_variable$, $string_piece$(\n"
+      "      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());\n"
+      "  // @@protoc_insertion_point(field_set_pointer:$full_name$)\n"
+      "}\n"
+      "inline ::std::string* $classname$::mutable_$name$() {\n"
+      "  $set_hasbit$\n"
+      "  // @@protoc_insertion_point(field_mutable:$full_name$)\n"
+      "  return $name$_.Mutable($default_variable$, GetArenaNoVirtual());\n"
+      "}\n"
+      "inline ::std::string* $classname$::$release_name$() {\n"
+      "  $clear_hasbit$\n"
+      "  return $name$_.Release($default_variable$, GetArenaNoVirtual());\n"
+      "}\n"
+      "inline ::std::string* $classname$::unsafe_arena_release_$name$() {\n"
+      "  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);\n"
+      "  $clear_hasbit$\n"
+      "  return $name$_.UnsafeArenaRelease($default_variable$,\n"
+      "      GetArenaNoVirtual());\n"
+      "}\n"
+      "inline void $classname$::set_allocated_$name$(::std::string* $name$) {\n"
+      "  if ($name$ != NULL) {\n"
+      "    $set_hasbit$\n"
+      "  } else {\n"
+      "    $clear_hasbit$\n"
+      "  }\n"
+      "  $name$_.SetAllocated($default_variable$, $name$,\n"
+      "      GetArenaNoVirtual());\n"
+      "  // @@protoc_insertion_point(field_set_allocated:$full_name$)\n"
+      "}\n"
+      "inline void $classname$::unsafe_arena_set_allocated_$name$(\n"
+      "    ::std::string* $name$) {\n"
+      "  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);\n"
+      "  if ($name$ != NULL) {\n"
+      "    $set_hasbit$\n"
+      "  } else {\n"
+      "    $clear_hasbit$\n"
+      "  }\n"
+      "  $set_hasbit$\n"
+      "  $name$_.UnsafeArenaSetAllocated($default_variable$,\n"
+      "      $name$, GetArenaNoVirtual());\n"
+      "  // @@protoc_insertion_point(field_set_allocated:$full_name$)\n"
+      "}\n");
   } else {
+    // No-arena case.
     printer->Print(variables_,
-      "    $name$_ = new ::std::string(*$default_variable$);\n");
+      "inline const ::std::string& $classname$::$name$() const {\n"
+      "  // @@protoc_insertion_point(field_get:$full_name$)\n"
+      "  return $name$_.GetNoArena($default_variable$);\n"
+      "}\n"
+      "inline void $classname$::set_$name$(const ::std::string& value) {\n"
+      "  $set_hasbit$\n"
+      "  $name$_.SetNoArena($default_variable$, value);\n"
+      "  // @@protoc_insertion_point(field_set:$full_name$)\n"
+      "}\n"
+      "inline void $classname$::set_$name$(const char* value) {\n"
+      "  $set_hasbit$\n"
+      "  $name$_.SetNoArena($default_variable$, $string_piece$(value));\n"
+      "  // @@protoc_insertion_point(field_set_char:$full_name$)\n"
+      "}\n"
+      "inline "
+      "void $classname$::set_$name$(const $pointer_type$* value, "
+      "size_t size) {\n"
+      "  $set_hasbit$\n"
+      "  $name$_.SetNoArena($default_variable$,\n"
+      "      $string_piece$(reinterpret_cast<const char*>(value), size));\n"
+      "  // @@protoc_insertion_point(field_set_pointer:$full_name$)\n"
+      "}\n"
+      "inline ::std::string* $classname$::mutable_$name$() {\n"
+      "  $set_hasbit$\n"
+      "  // @@protoc_insertion_point(field_mutable:$full_name$)\n"
+      "  return $name$_.MutableNoArena($default_variable$);\n"
+      "}\n"
+      "inline ::std::string* $classname$::$release_name$() {\n"
+      "  $clear_hasbit$\n"
+      "  return $name$_.ReleaseNoArena($default_variable$);\n"
+      "}\n"
+      "inline void $classname$::set_allocated_$name$(::std::string* $name$) {\n"
+      "  if ($name$ != NULL) {\n"
+      "    $set_hasbit$\n"
+      "  } else {\n"
+      "    $clear_hasbit$\n"
+      "  }\n"
+      "  $name$_.SetAllocatedNoArena($default_variable$, $name$);\n"
+      "  // @@protoc_insertion_point(field_set_allocated:$full_name$)\n"
+      "}\n");
   }
-  printer->Print(variables_,
-    "  }\n"
-    "  // @@protoc_insertion_point(field_mutable:$full_name$)\n"
-    "  return $name$_;\n"
-    "}\n"
-    "inline ::std::string* $classname$::$release_name$() {\n"
-    "  clear_has_$name$();\n"
-    "  if ($name$_ == $default_variable$) {\n"
-    "    return NULL;\n"
-    "  } else {\n"
-    "    ::std::string* temp = $name$_;\n"
-    "    $name$_ = const_cast< ::std::string*>($default_variable$);\n"
-    "    return temp;\n"
-    "  }\n"
-    "}\n"
-    "inline void $classname$::set_allocated_$name$(::std::string* $name$) {\n"
-    "  if ($name$_ != $default_variable$) {\n"
-    "    delete $name$_;\n"
-    "  }\n"
-    "  if ($name$) {\n"
-    "    set_has_$name$();\n"
-    "    $name$_ = $name$;\n"
-    "  } else {\n"
-    "    clear_has_$name$();\n"
-    "    $name$_ = const_cast< ::std::string*>($default_variable$);\n"
-    "  }\n"
-    "  // @@protoc_insertion_point(field_set_allocated:$full_name$)\n"
-    "}\n");
 }
 
 void StringFieldGenerator::
@@ -217,16 +281,26 @@ GenerateNonInlineAccessorDefinitions(io::Printer* printer) const {
 
 void StringFieldGenerator::
 GenerateClearingCode(io::Printer* printer) const {
-  if (descriptor_->default_value_string().empty()) {
-    printer->Print(variables_,
-      "if ($name$_ != $default_variable$) {\n"
-      "  $name$_->clear();\n"
-      "}\n");
+  // Two-dimension specialization here: supporting arenas or not, and default
+  // value is the empty string or not. Complexity here ensures the minimal
+  // number of branches / amount of extraneous code at runtime (given that the
+  // below methods are inlined one-liners)!
+  if (SupportsArenas(descriptor_)) {
+    if (descriptor_->default_value_string().empty()) {
+      printer->Print(variables_,
+        "$name$_.ClearToEmpty($default_variable$, GetArenaNoVirtual());\n");
+    } else {
+      printer->Print(variables_,
+        "$name$_.ClearToDefault($default_variable$, GetArenaNoVirtual());\n");
+    }
   } else {
-    printer->Print(variables_,
-      "if ($name$_ != $default_variable$) {\n"
-      "  $name$_->assign(*$default_variable$);\n"
-      "}\n");
+    if (descriptor_->default_value_string().empty()) {
+      printer->Print(variables_,
+        "$name$_.ClearToEmptyNoArena($default_variable$);\n");
+    } else {
+      printer->Print(variables_,
+        "$name$_.ClearToDefaultNoArena($default_variable$);\n");
+    }
   }
 }
 
@@ -237,21 +311,24 @@ GenerateMergingCode(io::Printer* printer) const {
 
 void StringFieldGenerator::
 GenerateSwappingCode(io::Printer* printer) const {
-  printer->Print(variables_, "std::swap($name$_, other->$name$_);\n");
+  printer->Print(variables_, "$name$_.Swap(&other->$name$_);\n");
 }
 
 void StringFieldGenerator::
 GenerateConstructorCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "$name$_ = const_cast< ::std::string*>($default_variable$);\n");
+      "$name$_.UnsafeSetDefault($default_variable$);\n");
 }
 
 void StringFieldGenerator::
 GenerateDestructorCode(io::Printer* printer) const {
-  printer->Print(variables_,
-    "if ($name$_ != $default_variable$) {\n"
-    "  delete $name$_;\n"
-    "}\n");
+  if (SupportsArenas(descriptor_)) {
+    printer->Print(variables_,
+      "$name$_.Destroy($default_variable$, GetArenaNoVirtual());\n");
+  } else {
+    printer->Print(variables_,
+      "$name$_.DestroyNoArena($default_variable$);\n");
+  }
 }
 
 void StringFieldGenerator::
@@ -276,13 +353,14 @@ GenerateMergeFromCodedStream(io::Printer* printer) const {
   printer->Print(variables_,
     "DO_(::google::protobuf::internal::WireFormatLite::Read$declared_type$(\n"
     "      input, this->mutable_$name$()));\n");
+
   if (HasUtf8Verification(descriptor_->file()) &&
       descriptor_->type() == FieldDescriptor::TYPE_STRING) {
     printer->Print(variables_,
       "::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(\n"
       "  this->$name$().data(), this->$name$().length(),\n"
       "  ::google::protobuf::internal::WireFormat::PARSE,\n"
-      "  \"$name$\");\n");
+      "  \"$full_name$\");\n");
   }
 }
 
@@ -294,7 +372,7 @@ GenerateSerializeWithCachedSizes(io::Printer* printer) const {
       "::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(\n"
       "  this->$name$().data(), this->$name$().length(),\n"
       "  ::google::protobuf::internal::WireFormat::SERIALIZE,\n"
-      "  \"$name$\");\n");
+      "  \"$full_name$\");\n");
   }
   printer->Print(variables_,
     "::google::protobuf::internal::WireFormatLite::Write$declared_type$MaybeAliased(\n"
@@ -309,7 +387,7 @@ GenerateSerializeWithCachedSizesToArray(io::Printer* printer) const {
       "::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(\n"
       "  this->$name$().data(), this->$name$().length(),\n"
       "  ::google::protobuf::internal::WireFormat::SERIALIZE,\n"
-      "  \"$name$\");\n");
+      "  \"$full_name$\");\n");
   }
   printer->Print(variables_,
     "target =\n"
@@ -338,84 +416,186 @@ StringOneofFieldGenerator::~StringOneofFieldGenerator() {}
 
 void StringOneofFieldGenerator::
 GenerateInlineAccessorDefinitions(io::Printer* printer) const {
-  printer->Print(variables_,
-    "inline const ::std::string& $classname$::$name$() const {\n"
-    "  if (has_$name$()) {\n"
-    "    return *$oneof_prefix$$name$_;\n"
-    "  }\n");
-  if (descriptor_->default_value_string().empty()) {
-    printer->Print(variables_,
-      "  return ::google::protobuf::internal::GetEmptyStringAlreadyInited();\n");
-  } else {
-    printer->Print(variables_,
-      "  return *$default_variable$;\n");
-  }
-  printer->Print(variables_,
-    "}\n"
-    "inline void $classname$::set_$name$(const ::std::string& value) {\n"
-    "  if (!has_$name$()) {\n"
-    "    clear_$oneof_name$();\n"
-    "    set_has_$name$();\n"
-    "    $oneof_prefix$$name$_ = new ::std::string;\n"
-    "  }\n"
-    "  $oneof_prefix$$name$_->assign(value);\n"
-    "}\n"
-    "inline void $classname$::set_$name$(const char* value) {\n"
-    "  if (!has_$name$()) {\n"
-    "    clear_$oneof_name$();\n"
-    "    set_has_$name$();\n"
-    "    $oneof_prefix$$name$_ = new ::std::string;\n"
-    "  }\n"
-    "  $oneof_prefix$$name$_->assign(value);\n"
-    "}\n"
-    "inline "
-    "void $classname$::set_$name$(const $pointer_type$* value, size_t size) {\n"
-    "  if (!has_$name$()) {\n"
-    "    clear_$oneof_name$();\n"
-    "    set_has_$name$();\n"
-    "    $oneof_prefix$$name$_ = new ::std::string;\n"
-    "  }\n"
-    "  $oneof_prefix$$name$_->assign(\n"
-    "      reinterpret_cast<const char*>(value), size);\n"
-    "}\n"
-    "inline ::std::string* $classname$::mutable_$name$() {\n"
-    "  if (!has_$name$()) {\n"
-    "    clear_$oneof_name$();\n"
-    "    set_has_$name$();\n");
-  if (descriptor_->default_value_string().empty()) {
+  if (SupportsArenas(descriptor_)) {
     printer->Print(variables_,
-      "    $oneof_prefix$$name$_ = new ::std::string;\n");
+      "inline const ::std::string& $classname$::$name$() const {\n"
+      "  // @@protoc_insertion_point(field_get:$full_name$)\n"
+      "  if (has_$name$()) {\n"
+      "    return $oneof_prefix$$name$_.Get($default_variable$);\n"
+      "  }\n"
+      "  return *$default_variable$;\n"
+      "}\n"
+      "inline void $classname$::set_$name$(const ::std::string& value) {\n"
+      "  if (!has_$name$()) {\n"
+      "    clear_$oneof_name$();\n"
+      "    set_has_$name$();\n"
+      "    $oneof_prefix$$name$_.UnsafeSetDefault($default_variable$);\n"
+      "  }\n"
+      "  $oneof_prefix$$name$_.Set($default_variable$, value,\n"
+      "      GetArenaNoVirtual());\n"
+      "  // @@protoc_insertion_point(field_set:$full_name$)\n"
+      "}\n"
+      "inline void $classname$::set_$name$(const char* value) {\n"
+      "  if (!has_$name$()) {\n"
+      "    clear_$oneof_name$();\n"
+      "    set_has_$name$();\n"
+      "    $oneof_prefix$$name$_.UnsafeSetDefault($default_variable$);\n"
+      "  }\n"
+      "  $oneof_prefix$$name$_.Set($default_variable$,\n"
+      "      $string_piece$(value), GetArenaNoVirtual());\n"
+      "  // @@protoc_insertion_point(field_set_char:$full_name$)\n"
+      "}\n"
+      "inline "
+      "void $classname$::set_$name$(const $pointer_type$* value,\n"
+      "                             size_t size) {\n"
+      "  if (!has_$name$()) {\n"
+      "    clear_$oneof_name$();\n"
+      "    set_has_$name$();\n"
+      "    $oneof_prefix$$name$_.UnsafeSetDefault($default_variable$);\n"
+      "  }\n"
+      "  $oneof_prefix$$name$_.Set($default_variable$, $string_piece$(\n"
+      "      reinterpret_cast<const char*>(value), size),\n"
+      "      GetArenaNoVirtual());\n"
+      "  // @@protoc_insertion_point(field_set_pointer:$full_name$)\n"
+      "}\n"
+      "inline ::std::string* $classname$::mutable_$name$() {\n"
+      "  if (!has_$name$()) {\n"
+      "    clear_$oneof_name$();\n"
+      "    set_has_$name$();\n"
+      "    $oneof_prefix$$name$_.UnsafeSetDefault($default_variable$);\n"
+      "  }\n"
+      "  return $oneof_prefix$$name$_.Mutable($default_variable$,\n"
+      "      GetArenaNoVirtual());\n"
+      "  // @@protoc_insertion_point(field_mutable:$full_name$)\n"
+      "}\n"
+      "inline ::std::string* $classname$::$release_name$() {\n"
+      "  if (has_$name$()) {\n"
+      "    clear_has_$oneof_name$();\n"
+      "    return $oneof_prefix$$name$_.Release($default_variable$,\n"
+      "        GetArenaNoVirtual());\n"
+      "  } else {\n"
+      "    return NULL;\n"
+      "  }\n"
+      "}\n"
+      "inline ::std::string* $classname$::unsafe_arena_release_$name$() {\n"
+      "  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);\n"
+      "  if (has_$name$()) {\n"
+      "    clear_has_$oneof_name$();\n"
+      "    return $oneof_prefix$$name$_.UnsafeArenaRelease(\n"
+      "        $default_variable$, GetArenaNoVirtual());\n"
+      "  } else {\n"
+      "    return NULL;\n"
+      "  }\n"
+      "}\n"
+      "inline void $classname$::set_allocated_$name$(::std::string* $name$) {\n"
+      "  if (!has_$name$()) {\n"
+      "    $oneof_prefix$$name$_.UnsafeSetDefault($default_variable$);\n"
+      "  }\n"
+      "  clear_$oneof_name$();\n"
+      "  if ($name$ != NULL) {\n"
+      "    set_has_$name$();\n"
+      "    $oneof_prefix$$name$_.SetAllocated($default_variable$, $name$,\n"
+      "        GetArenaNoVirtual());\n"
+      "  }\n"
+      "  // @@protoc_insertion_point(field_set_allocated:$full_name$)\n"
+      "}\n"
+      "inline void $classname$::unsafe_arena_set_allocated_$name$("
+      "::std::string* $name$) {\n"
+      "  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);\n"
+      "  if (!has_$name$()) {\n"
+      "    $oneof_prefix$$name$_.UnsafeSetDefault($default_variable$);\n"
+      "  }\n"
+      "  clear_$oneof_name$();\n"
+      "  if ($name$) {\n"
+      "    set_has_$name$();\n"
+      "    $oneof_prefix$$name$_.UnsafeArenaSetAllocated($default_variable$, "
+      "$name$, GetArenaNoVirtual());\n"
+      "  }\n"
+      "  // @@protoc_insertion_point(field_set_allocated:$full_name$)\n"
+      "}\n");
   } else {
+    // No-arena case.
     printer->Print(variables_,
-      "    $oneof_prefix$$name$_ = new ::std::string(*$default_variable$);\n");
+      "inline const ::std::string& $classname$::$name$() const {\n"
+      "  // @@protoc_insertion_point(field_get:$full_name$)\n"
+      "  if (has_$name$()) {\n"
+      "    return $oneof_prefix$$name$_.GetNoArena($default_variable$);\n"
+      "  }\n"
+      "  return *$default_variable$;\n"
+      "}\n"
+      "inline void $classname$::set_$name$(const ::std::string& value) {\n"
+      "  // @@protoc_insertion_point(field_set:$full_name$)\n"
+      "  if (!has_$name$()) {\n"
+      "    clear_$oneof_name$();\n"
+      "    set_has_$name$();\n"
+      "    $oneof_prefix$$name$_.UnsafeSetDefault($default_variable$);\n"
+      "  }\n"
+      "  $oneof_prefix$$name$_.SetNoArena($default_variable$, value);\n"
+      "  // @@protoc_insertion_point(field_set:$full_name$)\n"
+      "}\n"
+      "inline void $classname$::set_$name$(const char* value) {\n"
+      "  if (!has_$name$()) {\n"
+      "    clear_$oneof_name$();\n"
+      "    set_has_$name$();\n"
+      "    $oneof_prefix$$name$_.UnsafeSetDefault($default_variable$);\n"
+      "  }\n"
+      "  $oneof_prefix$$name$_.SetNoArena($default_variable$,\n"
+      "      $string_piece$(value));\n"
+      "  // @@protoc_insertion_point(field_set_char:$full_name$)\n"
+      "}\n"
+      "inline "
+      "void $classname$::set_$name$(const $pointer_type$* value, size_t size) {\n"
+      "  if (!has_$name$()) {\n"
+      "    clear_$oneof_name$();\n"
+      "    set_has_$name$();\n"
+      "    $oneof_prefix$$name$_.UnsafeSetDefault($default_variable$);\n"
+      "  }\n"
+      "  $oneof_prefix$$name$_.SetNoArena($default_variable$, $string_piece$(\n"
+      "      reinterpret_cast<const char*>(value), size));\n"
+      "  // @@protoc_insertion_point(field_set_pointer:$full_name$)\n"
+      "}\n"
+      "inline ::std::string* $classname$::mutable_$name$() {\n"
+      "  if (!has_$name$()) {\n"
+      "    clear_$oneof_name$();\n"
+      "    set_has_$name$();\n"
+      "    $oneof_prefix$$name$_.UnsafeSetDefault($default_variable$);\n"
+      "  }\n"
+      "  // @@protoc_insertion_point(field_mutable:$full_name$)\n"
+      "  return $oneof_prefix$$name$_.MutableNoArena($default_variable$);\n"
+      "}\n"
+      "inline ::std::string* $classname$::$release_name$() {\n"
+      "  if (has_$name$()) {\n"
+      "    clear_has_$oneof_name$();\n"
+      "    return $oneof_prefix$$name$_.ReleaseNoArena($default_variable$);\n"
+      "  } else {\n"
+      "    return NULL;\n"
+      "  }\n"
+      "}\n"
+      "inline void $classname$::set_allocated_$name$(::std::string* $name$) {\n"
+      "  if (!has_$name$()) {\n"
+      "    $oneof_prefix$$name$_.UnsafeSetDefault($default_variable$);\n"
+      "  }\n"
+      "  clear_$oneof_name$();\n"
+      "  if ($name$ != NULL) {\n"
+      "    set_has_$name$();\n"
+      "    $oneof_prefix$$name$_.SetAllocatedNoArena($default_variable$,\n"
+      "        $name$);\n"
+      "  }\n"
+      "  // @@protoc_insertion_point(field_set_allocated:$full_name$)\n"
+      "}\n");
   }
-  printer->Print(variables_,
-    "  }\n"
-    "  return $oneof_prefix$$name$_;\n"
-    "}\n"
-    "inline ::std::string* $classname$::$release_name$() {\n"
-    "  if (has_$name$()) {\n"
-    "    clear_has_$oneof_name$();\n"
-    "    ::std::string* temp = $oneof_prefix$$name$_;\n"
-    "    $oneof_prefix$$name$_ = NULL;\n"
-    "    return temp;\n"
-    "  } else {\n"
-    "    return NULL;\n"
-    "  }\n"
-    "}\n"
-    "inline void $classname$::set_allocated_$name$(::std::string* $name$) {\n"
-    "  clear_$oneof_name$();\n"
-    "  if ($name$) {\n"
-    "    set_has_$name$();\n"
-    "    $oneof_prefix$$name$_ = $name$;\n"
-    "  }\n"
-    "}\n");
 }
 
 void StringOneofFieldGenerator::
 GenerateClearingCode(io::Printer* printer) const {
+  if (SupportsArenas(descriptor_)) {
     printer->Print(variables_,
-      "delete $oneof_prefix$$name$_;\n");
+      "$oneof_prefix$$name$_.Destroy($default_variable$,\n"
+      "    GetArenaNoVirtual());\n");
+  } else {
+    printer->Print(variables_,
+      "$oneof_prefix$$name$_.DestroyNoArena($default_variable$);\n");
+  }
 }
 
 void StringOneofFieldGenerator::
@@ -425,25 +605,45 @@ GenerateSwappingCode(io::Printer* printer) const {
 
 void StringOneofFieldGenerator::
 GenerateConstructorCode(io::Printer* printer) const {
-  if (!descriptor_->default_value_string().empty()) {
+  printer->Print(variables_,
+    "  const_cast< ::google::protobuf::internal::ArenaStringPtr*>("
+    "&$classname$_default_oneof_instance_->$name$_)->UnsafeSetDefault("
+    "$default_variable$);\n");
+}
+
+void StringOneofFieldGenerator::
+GenerateDestructorCode(io::Printer* printer) const {
+  if (SupportsArenas(descriptor_)) {
     printer->Print(variables_,
-      "  $classname$_default_oneof_instance_->$name$_ = "
-      "$classname$::$default_variable$;\n");
+      "if (has_$name$()) {\n"
+      "  $oneof_prefix$$name$_.Destroy($default_variable$,\n"
+      "      GetArenaNoVirtual());\n"
+      "}\n");
   } else {
     printer->Print(variables_,
-      "  $classname$_default_oneof_instance_->$name$_ = "
-      "$default_variable$;\n");
+      "if (has_$name$()) {\n"
+      "  $oneof_prefix$$name$_.DestroyNoArena($default_variable$);\n"
+      "}\n");
   }
 }
 
 void StringOneofFieldGenerator::
-GenerateDestructorCode(io::Printer* printer) const {
-  printer->Print(variables_,
-    "if (has_$name$()) {\n"
-    "  delete $oneof_prefix$$name$_;\n"
-    "}\n");
+GenerateMergeFromCodedStream(io::Printer* printer) const {
+    printer->Print(variables_,
+      "DO_(::google::protobuf::internal::WireFormatLite::Read$declared_type$(\n"
+      "      input, this->mutable_$name$()));\n");
+
+  if (HasUtf8Verification(descriptor_->file()) &&
+      descriptor_->type() == FieldDescriptor::TYPE_STRING) {
+    printer->Print(variables_,
+      "::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(\n"
+      "  this->$name$().data(), this->$name$().length(),\n"
+      "  ::google::protobuf::internal::WireFormat::PARSE,\n"
+      "  \"$full_name$\");\n");
+  }
 }
 
+
 // ===================================================================
 
 RepeatedStringFieldGenerator::
@@ -566,7 +766,7 @@ GenerateMergingCode(io::Printer* printer) const {
 
 void RepeatedStringFieldGenerator::
 GenerateSwappingCode(io::Printer* printer) const {
-  printer->Print(variables_, "$name$_.Swap(&other->$name$_);\n");
+  printer->Print(variables_, "$name$_.UnsafeArenaSwap(&other->$name$_);\n");
 }
 
 void RepeatedStringFieldGenerator::
@@ -586,7 +786,7 @@ GenerateMergeFromCodedStream(io::Printer* printer) const {
       "  this->$name$(this->$name$_size() - 1).data(),\n"
       "  this->$name$(this->$name$_size() - 1).length(),\n"
       "  ::google::protobuf::internal::WireFormat::PARSE,\n"
-      "  \"$name$\");\n");
+      "  \"$full_name$\");\n");
   }
 }
 
@@ -600,7 +800,7 @@ GenerateSerializeWithCachedSizes(io::Printer* printer) const {
       "::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(\n"
       "  this->$name$(i).data(), this->$name$(i).length(),\n"
       "  ::google::protobuf::internal::WireFormat::SERIALIZE,\n"
-      "  \"$name$\");\n");
+      "  \"$full_name$\");\n");
   }
   printer->Print(variables_,
     "  ::google::protobuf::internal::WireFormatLite::Write$declared_type$(\n"
@@ -618,7 +818,7 @@ GenerateSerializeWithCachedSizesToArray(io::Printer* printer) const {
       "  ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(\n"
       "    this->$name$(i).data(), this->$name$(i).length(),\n"
       "    ::google::protobuf::internal::WireFormat::SERIALIZE,\n"
-      "    \"$name$\");\n");
+      "    \"$full_name$\");\n");
   }
   printer->Print(variables_,
     "  target = ::google::protobuf::internal::WireFormatLite::\n"
diff --git a/src/google/protobuf/compiler/cpp/cpp_string_field.h b/src/google/protobuf/compiler/cpp/cpp_string_field.h
index 86da38f2..0a5ca440 100644
--- a/src/google/protobuf/compiler/cpp/cpp_string_field.h
+++ b/src/google/protobuf/compiler/cpp/cpp_string_field.h
@@ -88,6 +88,7 @@ class StringOneofFieldGenerator : public StringFieldGenerator {
   void GenerateSwappingCode(io::Printer* printer) const;
   void GenerateConstructorCode(io::Printer* printer) const;
   void GenerateDestructorCode(io::Printer* printer) const;
+  void GenerateMergeFromCodedStream(io::Printer* printer) const;
 
  private:
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(StringOneofFieldGenerator);
diff --git a/src/google/protobuf/compiler/cpp/cpp_test_bad_identifiers.proto b/src/google/protobuf/compiler/cpp/cpp_test_bad_identifiers.proto
index 6b7f8308..4fa3c144 100644
--- a/src/google/protobuf/compiler/cpp/cpp_test_bad_identifiers.proto
+++ b/src/google/protobuf/compiler/cpp/cpp_test_bad_identifiers.proto
@@ -35,6 +35,7 @@
 // This file tests that various identifiers work as field and type names even
 // though the same identifiers are used internally by the C++ code generator.
 
+syntax = "proto2";
 
 // Some generic_services option(s) added automatically.
 // See:  http://go/proto2-generic-services-default
@@ -58,7 +59,7 @@ message TestConflictingSymbolNames {
   optional int32 total_size = 6;
   optional int32 tag = 7;
 
-  enum TestEnum { FOO = 1; }
+  enum TestEnum { FOO = 0; }
   message Data1 { repeated int32 data = 1; }
   message Data2 { repeated TestEnum data = 1; }
   message Data3 { repeated string data = 1; }
@@ -99,6 +100,8 @@ message TestConflictingSymbolNames {
   optional uint32 int = 30;
   optional uint32 friend = 31;
   optional uint32 class = 37;
+  optional uint32 typedecl = 39;
+  optional uint32 auto = 40;
 
   // The generator used to #define a macro called "DO" inside the .cc file.
   message DO {}
@@ -116,15 +119,18 @@ message TestConflictingSymbolNames {
   // names.
   optional DO release_do = 36;
 
-  extensions 1000 to max;
-}
+  // For clashing local variables in Serialize and ByteSize calculation.
+  optional string target = 38;
 
-message TestConflictingSymbolNamesExtension {
-  extend TestConflictingSymbolNames {
-    repeated int32 repeated_int32_ext = 20423638 [packed=true];
-  }
+  extensions 1000 to max;  // NO_PROTO3
 }
 
+message TestConflictingSymbolNamesExtension {                    // NO_PROTO3
+  extend TestConflictingSymbolNames {                            // NO_PROTO3
+    repeated int32 repeated_int32_ext = 20423638 [packed=true];  // NO_PROTO3
+  }                                                              // NO_PROTO3
+}                                                                // NO_PROTO3
+
 message DummyMessage {}
 
 service TestConflictingMethodNames {
diff --git a/src/google/protobuf/compiler/cpp/cpp_unittest.cc b/src/google/protobuf/compiler/cpp/cpp_unittest.cc
index 93e1c3f1..c509a6a9 100644
--- a/src/google/protobuf/compiler/cpp/cpp_unittest.cc
+++ b/src/google/protobuf/compiler/cpp/cpp_unittest.cc
@@ -47,6 +47,9 @@
 #include <google/protobuf/compiler/cpp/cpp_unittest.h>
 
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <vector>
 
 #include <google/protobuf/unittest.pb.h>
diff --git a/src/google/protobuf/compiler/importer.cc b/src/google/protobuf/compiler/importer.cc
index e6c446af..678823cd 100644
--- a/src/google/protobuf/compiler/importer.cc
+++ b/src/google/protobuf/compiler/importer.cc
@@ -44,6 +44,9 @@
 
 #include <algorithm>
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 
 #include <google/protobuf/compiler/importer.h>
 
diff --git a/src/google/protobuf/compiler/importer_unittest.cc b/src/google/protobuf/compiler/importer_unittest.cc
index 8cc5d882..81c636c6 100644
--- a/src/google/protobuf/compiler/importer_unittest.cc
+++ b/src/google/protobuf/compiler/importer_unittest.cc
@@ -34,9 +34,13 @@
 
 #include <google/protobuf/stubs/hash.h>
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 
 #include <google/protobuf/compiler/importer.h>
 #include <google/protobuf/descriptor.h>
+#include <google/protobuf/testing/file.h>
 #include <google/protobuf/io/zero_copy_stream_impl.h>
 
 #include <google/protobuf/stubs/map_util.h>
@@ -53,6 +57,10 @@ namespace compiler {
 
 namespace {
 
+bool FileExists(const string& path) {
+  return File::Exists(path);
+}
+
 #define EXPECT_SUBSTRING(needle, haystack) \
   EXPECT_PRED_FORMAT2(testing::IsSubstring, (needle), (haystack))
 
@@ -215,120 +223,6 @@ TEST_F(ImporterTest, RecursiveImport) {
     error_collector_.text_);
 }
 
-// TODO(sanjay): The MapField tests below more properly belong in
-// descriptor_unittest, but are more convenient to test here.
-TEST_F(ImporterTest, MapFieldValid) {
-  AddFile(
-      "map.proto",
-      "syntax = \"proto2\";\n"
-      "message Item {\n"
-      "  required string key = 1;\n"
-      "}\n"
-      "message Map {\n"
-      "  repeated Item items = 1 [experimental_map_key = \"key\"];\n"
-      "}\n"
-      );
-  const FileDescriptor* file = importer_.Import("map.proto");
-  ASSERT_TRUE(file != NULL) << error_collector_.text_;
-  EXPECT_EQ("", error_collector_.text_);
-
-  // Check that Map::items points to Item::key
-  const Descriptor* item_type = file->FindMessageTypeByName("Item");
-  ASSERT_TRUE(item_type != NULL);
-  const Descriptor* map_type = file->FindMessageTypeByName("Map");
-  ASSERT_TRUE(map_type != NULL);
-  const FieldDescriptor* key_field = item_type->FindFieldByName("key");
-  ASSERT_TRUE(key_field != NULL);
-  const FieldDescriptor* items_field = map_type->FindFieldByName("items");
-  ASSERT_TRUE(items_field != NULL);
-  EXPECT_EQ(items_field->experimental_map_key(), key_field);
-}
-
-TEST_F(ImporterTest, MapFieldNotRepeated) {
-  AddFile(
-      "map.proto",
-      "syntax = \"proto2\";\n"
-      "message Item {\n"
-      "  required string key = 1;\n"
-      "}\n"
-      "message Map {\n"
-      "  required Item items = 1 [experimental_map_key = \"key\"];\n"
-      "}\n"
-      );
-  EXPECT_TRUE(importer_.Import("map.proto") == NULL);
-  EXPECT_SUBSTRING("only allowed for repeated fields", error());
-}
-
-TEST_F(ImporterTest, MapFieldNotMessageType) {
-  AddFile(
-      "map.proto",
-      "syntax = \"proto2\";\n"
-      "message Map {\n"
-      "  repeated int32 items = 1 [experimental_map_key = \"key\"];\n"
-      "}\n"
-      );
-  EXPECT_TRUE(importer_.Import("map.proto") == NULL);
-  EXPECT_SUBSTRING("only allowed for fields with a message type", error());
-}
-
-TEST_F(ImporterTest, MapFieldTypeNotFound) {
-  AddFile(
-      "map.proto",
-      "syntax = \"proto2\";\n"
-      "message Map {\n"
-      "  repeated Unknown items = 1 [experimental_map_key = \"key\"];\n"
-      "}\n"
-      );
-  EXPECT_TRUE(importer_.Import("map.proto") == NULL);
-  EXPECT_SUBSTRING("not defined", error());
-}
-
-TEST_F(ImporterTest, MapFieldKeyNotFound) {
-  AddFile(
-      "map.proto",
-      "syntax = \"proto2\";\n"
-      "message Item {\n"
-      "  required string key = 1;\n"
-      "}\n"
-      "message Map {\n"
-      "  repeated Item items = 1 [experimental_map_key = \"badkey\"];\n"
-      "}\n"
-      );
-  EXPECT_TRUE(importer_.Import("map.proto") == NULL);
-  EXPECT_SUBSTRING("Could not find field", error());
-}
-
-TEST_F(ImporterTest, MapFieldKeyRepeated) {
-  AddFile(
-      "map.proto",
-      "syntax = \"proto2\";\n"
-      "message Item {\n"
-      "  repeated string key = 1;\n"
-      "}\n"
-      "message Map {\n"
-      "  repeated Item items = 1 [experimental_map_key = \"key\"];\n"
-      "}\n"
-      );
-  EXPECT_TRUE(importer_.Import("map.proto") == NULL);
-  EXPECT_SUBSTRING("must not name a repeated field", error());
-}
-
-TEST_F(ImporterTest, MapFieldKeyNotScalar) {
-  AddFile(
-      "map.proto",
-      "syntax = \"proto2\";\n"
-      "message ItemKey { }\n"
-      "message Item {\n"
-      "  required ItemKey key = 1;\n"
-      "}\n"
-      "message Map {\n"
-      "  repeated Item items = 1 [experimental_map_key = \"key\"];\n"
-      "}\n"
-      );
-  EXPECT_TRUE(importer_.Import("map.proto") == NULL);
-  EXPECT_SUBSTRING("must name a scalar or string", error());
-}
-
 
 // ===================================================================
 
@@ -339,7 +233,7 @@ class DiskSourceTreeTest : public testing::Test {
     dirnames_.push_back(TestTempDir() + "/test_proto2_import_path_2");
 
     for (int i = 0; i < dirnames_.size(); i++) {
-      if (File::Exists(dirnames_[i])) {
+      if (FileExists(dirnames_[i])) {
         File::DeleteRecursively(dirnames_[i], NULL, NULL);
       }
       GOOGLE_CHECK_OK(File::CreateDir(dirnames_[i], 0777));
diff --git a/src/google/protobuf/compiler/java/java_context.h b/src/google/protobuf/compiler/java/java_context.h
index 57914450..7f1ce1f9 100644
--- a/src/google/protobuf/compiler/java/java_context.h
+++ b/src/google/protobuf/compiler/java/java_context.h
@@ -33,6 +33,9 @@
 
 #include <map>
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <vector>
 
 #include <google/protobuf/stubs/common.h>
diff --git a/src/google/protobuf/compiler/java/java_enum.cc b/src/google/protobuf/compiler/java/java_enum.cc
index 668377a3..0353b607 100644
--- a/src/google/protobuf/compiler/java/java_enum.cc
+++ b/src/google/protobuf/compiler/java/java_enum.cc
@@ -111,6 +111,10 @@ void EnumGenerator::Generate(io::Printer* printer) {
       "$name$($index$, $number$),\n");
   }
 
+  if (SupportUnknownEnumValue(descriptor_->file())) {
+    printer->Print("UNRECOGNIZED(-1, -1),\n");
+  }
+
   printer->Print(
     ";\n"
     "\n");
@@ -141,7 +145,17 @@ void EnumGenerator::Generate(io::Printer* printer) {
 
   printer->Print(
     "\n"
-    "public final int getNumber() { return value; }\n"
+    "public final int getNumber() {\n");
+  if (SupportUnknownEnumValue(descriptor_->file())) {
+    printer->Print(
+      "  if (index == -1) {\n"
+      "    throw new java.lang.IllegalArgumentException(\n"
+      "        \"Can't get the number of an unknown enum value.\");\n"
+      "  }\n");
+  }
+  printer->Print(
+    "  return value;\n"
+    "}\n"
     "\n"
     "public static $classname$ valueOf(int value) {\n"
     "  switch (value) {\n",
@@ -231,11 +245,12 @@ void EnumGenerator::Generate(io::Printer* printer) {
             "index", SimpleItoa(descriptor_->index()));
         }
         printer->Print(
-          "return $immutable_package$.$descriptor_class$.getDescriptor()\n"
+          "return $immutable_package$.$descriptor_class$.$descriptor$\n"
           "    .getEnumTypes().get($index$);\n",
           "immutable_package", FileJavaPackage(descriptor_->file(), true),
           "descriptor_class",
           name_resolver_->GetDescriptorClassName(descriptor_->file()),
+          "descriptor", "getDescriptor()",
           "index", SimpleItoa(descriptor_->index()));
         printer->Outdent();
       }
@@ -283,11 +298,18 @@ void EnumGenerator::Generate(io::Printer* printer) {
       "  if (desc.getType() != getDescriptor()) {\n"
       "    throw new java.lang.IllegalArgumentException(\n"
       "      \"EnumValueDescriptor is not for this type.\");\n"
-      "  }\n"
+      "  }\n",
+      "classname", descriptor_->name());
+    if (SupportUnknownEnumValue(descriptor_->file())) {
+      printer->Print(
+        "  if (desc.getIndex() == -1) {\n"
+        "    return UNRECOGNIZED;\n"
+        "  }\n");
+    }
+    printer->Print(
       "  return VALUES[desc.getIndex()];\n"
       "}\n"
-      "\n",
-      "classname", descriptor_->name());
+      "\n");
 
     // index is only used for reflection; lite implementation does not need it
     printer->Print("private final int index;\n");
diff --git a/src/google/protobuf/compiler/java/java_enum_field.cc b/src/google/protobuf/compiler/java/java_enum_field.cc
index 1f0c4af0..71a2ba4b 100644
--- a/src/google/protobuf/compiler/java/java_enum_field.cc
+++ b/src/google/protobuf/compiler/java/java_enum_field.cc
@@ -65,6 +65,8 @@ void SetEnumVariables(const FieldDescriptor* descriptor,
   (*variables)["mutable_type"] =
       name_resolver->GetMutableClassName(descriptor->enum_type());
   (*variables)["default"] = ImmutableDefaultValue(descriptor, name_resolver);
+  (*variables)["default_number"] = SimpleItoa(
+      descriptor->default_value_enum()->number());
   (*variables)["tag"] = SimpleItoa(internal::WireFormat::MakeTag(descriptor));
   (*variables)["tag_size"] = SimpleItoa(
       internal::WireFormat::TagSize(descriptor->number(), GetType(descriptor)));
@@ -95,7 +97,8 @@ void SetEnumVariables(const FieldDescriptor* descriptor,
     (*variables)["clear_has_field_bit_builder"] = "";
 
     (*variables)["is_field_present_message"] =
-          (*variables)["name"] + "_ != " + (*variables)["default"];
+        (*variables)["name"] + "_ != " +
+        (*variables)["default"] + ".getNumber()";
   }
 
   // For repated builders, one bit is used for whether the array is immutable.
@@ -114,6 +117,12 @@ void SetEnumVariables(const FieldDescriptor* descriptor,
       GenerateGetBitFromLocal(builderBitIndex);
   (*variables)["set_has_field_bit_to_local"] =
       GenerateSetBitToLocal(messageBitIndex);
+
+  if (SupportUnknownEnumValue(descriptor->file())) {
+    (*variables)["unknown"] = (*variables)["type"] + ".UNRECOGNIZED";
+  } else {
+    (*variables)["unknown"] = (*variables)["default"];
+  }
 }
 
 }  // namespace
@@ -150,6 +159,11 @@ GenerateInterfaceMembers(io::Printer* printer) const {
     printer->Print(variables_,
       "$deprecation$boolean has$capitalized_name$();\n");
   }
+  if (SupportUnknownEnumValue(descriptor_->file())) {
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$int get$capitalized_name$Value();\n");
+  }
   WriteFieldDocComment(printer, descriptor_);
   printer->Print(variables_,
     "$deprecation$$type$ get$capitalized_name$();\n");
@@ -158,7 +172,7 @@ GenerateInterfaceMembers(io::Printer* printer) const {
 void ImmutableEnumFieldGenerator::
 GenerateMembers(io::Printer* printer) const {
   printer->Print(variables_,
-    "private $type$ $name$_;\n");
+    "private int $name$_;\n");
   PrintExtraFieldInfo(variables_, printer);
   if (SupportFieldPresence(descriptor_->file())) {
     WriteFieldDocComment(printer, descriptor_);
@@ -167,17 +181,25 @@ GenerateMembers(io::Printer* printer) const {
       "  return $get_has_field_bit_message$;\n"
       "}\n");
   }
+  if (SupportUnknownEnumValue(descriptor_->file())) {
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$public int get$capitalized_name$Value() {\n"
+      "  return $name$_;\n"
+      "}\n");
+  }
   WriteFieldDocComment(printer, descriptor_);
   printer->Print(variables_,
     "$deprecation$public $type$ get$capitalized_name$() {\n"
-    "  return $name$_;\n"
+    "  $type$ result = $type$.valueOf($name$_);\n"
+    "  return result == null ? $unknown$ : result;\n"
     "}\n");
 }
 
 void ImmutableEnumFieldGenerator::
 GenerateBuilderMembers(io::Printer* printer) const {
   printer->Print(variables_,
-    "private $type$ $name$_ = $default$;\n");
+    "private int $name$_ = $default_number$;\n");
   if (SupportFieldPresence(descriptor_->file())) {
     WriteFieldDocComment(printer, descriptor_);
     printer->Print(variables_,
@@ -185,10 +207,25 @@ GenerateBuilderMembers(io::Printer* printer) const {
       "  return $get_has_field_bit_builder$;\n"
       "}\n");
   }
+  if (SupportUnknownEnumValue(descriptor_->file())) {
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$public int get$capitalized_name$Value() {\n"
+      "  return $name$_;\n"
+      "}\n");
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$public Builder set$capitalized_name$Value(int value) {\n"
+      "  $name$_ = value;\n"
+      "  $on_changed$\n"
+      "  return this;\n"
+      "}\n");
+  }
   WriteFieldDocComment(printer, descriptor_);
   printer->Print(variables_,
     "$deprecation$public $type$ get$capitalized_name$() {\n"
-    "  return $name$_;\n"
+    "  $type$ result = $type$.valueOf($name$_);\n"
+    "  return result == null ? $unknown$ : result;\n"
     "}\n");
   WriteFieldDocComment(printer, descriptor_);
   printer->Print(variables_,
@@ -197,7 +234,7 @@ GenerateBuilderMembers(io::Printer* printer) const {
     "    throw new NullPointerException();\n"
     "  }\n"
     "  $set_has_field_bit_builder$\n"
-    "  $name$_ = value;\n"
+    "  $name$_ = value.getNumber();\n"
     "  $on_changed$\n"
     "  return this;\n"
     "}\n");
@@ -205,7 +242,7 @@ GenerateBuilderMembers(io::Printer* printer) const {
   printer->Print(variables_,
     "$deprecation$public Builder clear$capitalized_name$() {\n"
     "  $clear_has_field_bit_builder$\n"
-    "  $name$_ = $default$;\n"
+    "  $name$_ = $default_number$;\n"
     "  $on_changed$\n"
     "  return this;\n"
     "}\n");
@@ -218,13 +255,13 @@ GenerateFieldBuilderInitializationCode(io::Printer* printer)  const {
 
 void ImmutableEnumFieldGenerator::
 GenerateInitializationCode(io::Printer* printer) const {
-  printer->Print(variables_, "$name$_ = $default$;\n");
+  printer->Print(variables_, "$name$_ = $default_number$;\n");
 }
 
 void ImmutableEnumFieldGenerator::
 GenerateBuilderClearCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "$name$_ = $default$;\n"
+    "$name$_ = $default_number$;\n"
     "$clear_has_field_bit_builder$\n");
 }
 
@@ -235,11 +272,13 @@ GenerateMergingCode(io::Printer* printer) const {
       "if (other.has$capitalized_name$()) {\n"
       "  set$capitalized_name$(other.get$capitalized_name$());\n"
       "}\n");
-  } else {
+  } else if (SupportUnknownEnumValue(descriptor_->file())) {
     printer->Print(variables_,
-      "if (other.get$capitalized_name$() != $default$) {\n"
-      "  set$capitalized_name$(other.get$capitalized_name$());\n"
+      "if (other.$name$_ != $default_number$) {\n"
+      "  set$capitalized_name$Value(other.get$capitalized_name$Value());\n"
       "}\n");
+  } else {
+    GOOGLE_LOG(FATAL) << "Can't reach here.";
   }
 }
 
@@ -257,23 +296,26 @@ GenerateBuildingCode(io::Printer* printer) const {
 
 void ImmutableEnumFieldGenerator::
 GenerateParsingCode(io::Printer* printer) const {
-  printer->Print(variables_,
-    "int rawValue = input.readEnum();\n"
-    "$type$ value = $type$.valueOf(rawValue);\n"
-    "if (value == null) {\n");
-  if (UseUnknownFieldSet(descriptor_->containing_type())) {
+  if (SupportUnknownEnumValue(descriptor_->file())) {
     printer->Print(variables_,
-      "  unknownFields.mergeVarintField($number$, rawValue);\n");
+      "int rawValue = input.readEnum();\n"
+      "$set_has_field_bit_message$\n"
+      "$name$_ = rawValue;\n");
   } else {
     printer->Print(variables_,
-      "  unknownFieldsCodedOutput.writeRawVarint32(tag);\n"
-      "  unknownFieldsCodedOutput.writeRawVarint32(rawValue);\n");
+      "int rawValue = input.readEnum();\n"
+      "$type$ value = $type$.valueOf(rawValue);\n"
+      "if (value == null) {\n");
+    if (PreserveUnknownFields(descriptor_->containing_type())) {
+      printer->Print(variables_,
+        "  unknownFields.mergeVarintField($number$, rawValue);\n");
+    }
+    printer->Print(variables_,
+      "} else {\n"
+      "  $set_has_field_bit_message$\n"
+      "  $name$_ = rawValue;\n"
+      "}\n");
   }
-  printer->Print(variables_,
-    "} else {\n"
-    "  $set_has_field_bit_message$\n"
-    "  $name$_ = value;\n"
-    "}\n");
 }
 
 void ImmutableEnumFieldGenerator::
@@ -285,7 +327,7 @@ void ImmutableEnumFieldGenerator::
 GenerateSerializationCode(io::Printer* printer) const {
   printer->Print(variables_,
     "if ($is_field_present_message$) {\n"
-    "  output.writeEnum($number$, $name$_.getNumber());\n"
+    "  output.writeEnum($number$, $name$_);\n"
     "}\n");
 }
 
@@ -294,23 +336,21 @@ GenerateSerializedSizeCode(io::Printer* printer) const {
   printer->Print(variables_,
     "if ($is_field_present_message$) {\n"
     "  size += com.google.protobuf.CodedOutputStream\n"
-    "    .computeEnumSize($number$, $name$_.getNumber());\n"
+    "    .computeEnumSize($number$, $name$_);\n"
     "}\n");
 }
 
 void ImmutableEnumFieldGenerator::
 GenerateEqualsCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "result = result &&\n"
-    "    (get$capitalized_name$() == other.get$capitalized_name$());\n");
+    "result = result && $name$_ == other.$name$_;\n");
 }
 
 void ImmutableEnumFieldGenerator::
 GenerateHashCode(io::Printer* printer) const {
   printer->Print(variables_,
     "hash = (37 * hash) + $constant_name$;\n"
-    "hash = (53 * hash) + com.google.protobuf.Internal.hashEnum(\n"
-    "    get$capitalized_name$());\n");
+    "hash = (53 * hash) + $name$_;\n");
 }
 
 string ImmutableEnumFieldGenerator::GetBoxedType() const {
@@ -344,11 +384,22 @@ GenerateMembers(io::Printer* printer) const {
       "  return $has_oneof_case_message$;\n"
       "}\n");
   }
+  if (SupportUnknownEnumValue(descriptor_->file())) {
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$public int get$capitalized_name$Value() {\n"
+      "  if ($has_oneof_case_message$) {\n"
+      "    return (java.lang.Integer) $oneof_name$_;\n"
+      "  }\n"
+      "  return $default_number$;\n"
+      "}\n");
+  }
   WriteFieldDocComment(printer, descriptor_);
   printer->Print(variables_,
     "$deprecation$public $type$ get$capitalized_name$() {\n"
     "  if ($has_oneof_case_message$) {\n"
-    "    return ($type$) $oneof_name$_;\n"
+    "    $type$ result =  $type$.valueOf((java.lang.Integer) $oneof_name$_);\n"
+    "    return result == null ? $unknown$ : result;\n"
     "  }\n"
     "  return $default$;\n"
     "}\n");
@@ -363,11 +414,30 @@ GenerateBuilderMembers(io::Printer* printer) const {
       "  return $has_oneof_case_message$;\n"
       "}\n");
   }
+  if (SupportUnknownEnumValue(descriptor_->file())) {
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$public int get$capitalized_name$Value() {\n"
+      "  if ($has_oneof_case_message$) {\n"
+      "    return ((java.lang.Integer) $oneof_name$_).intValue();\n"
+      "  }\n"
+      "  return $default_number$;\n"
+      "}\n");
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$public Builder set$capitalized_name$Value(int value) {\n"
+      "  $set_oneof_case_message$;\n"
+      "  $oneof_name$_ = value;\n"
+      "  $on_changed$\n"
+      "  return this;\n"
+      "}\n");
+  }
   WriteFieldDocComment(printer, descriptor_);
   printer->Print(variables_,
     "$deprecation$public $type$ get$capitalized_name$() {\n"
     "  if ($has_oneof_case_message$) {\n"
-    "    return ($type$) $oneof_name$_;\n"
+    "    $type$ result =  $type$.valueOf((java.lang.Integer) $oneof_name$_);\n"
+    "    return result == null ? $unknown$ : result;\n"
     "  }\n"
     "  return $default$;\n"
     "}\n");
@@ -378,7 +448,7 @@ GenerateBuilderMembers(io::Printer* printer) const {
     "    throw new NullPointerException();\n"
     "  }\n"
     "  $set_oneof_case_message$;\n"
-    "  $oneof_name$_ = value;\n"
+    "  $oneof_name$_ = value.getNumber();\n"
     "  $on_changed$\n"
     "  return this;\n"
     "}\n");
@@ -404,36 +474,44 @@ GenerateBuildingCode(io::Printer* printer) const {
 
 void ImmutableEnumOneofFieldGenerator::
 GenerateMergingCode(io::Printer* printer) const {
-  printer->Print(variables_,
-    "set$capitalized_name$(other.get$capitalized_name$());\n");
+  if (SupportUnknownEnumValue(descriptor_->file())) {
+    printer->Print(variables_,
+      "set$capitalized_name$Value(other.get$capitalized_name$Value());\n");
+  } else {
+    printer->Print(variables_,
+      "set$capitalized_name$(other.get$capitalized_name$());\n");
+  }
 }
 
 void ImmutableEnumOneofFieldGenerator::
 GenerateParsingCode(io::Printer* printer) const {
-  printer->Print(variables_,
-    "int rawValue = input.readEnum();\n"
-    "$type$ value = $type$.valueOf(rawValue);\n"
-    "if (value == null) {\n");
-  if (UseUnknownFieldSet(descriptor_->containing_type())) {
+  if (SupportUnknownEnumValue(descriptor_->file())) {
     printer->Print(variables_,
-      "  unknownFields.mergeVarintField($number$, rawValue);\n");
+      "int rawValue = input.readEnum();\n"
+      "$set_oneof_case_message$;\n"
+      "$oneof_name$_ = rawValue;\n");
   } else {
     printer->Print(variables_,
-      "  unknownFieldsCodedOutput.writeRawVarint32(tag);\n"
-      "  unknownFieldsCodedOutput.writeRawVarint32(rawValue);\n");
+      "int rawValue = input.readEnum();\n"
+      "$type$ value = $type$.valueOf(rawValue);\n"
+      "if (value == null) {\n");
+    if (PreserveUnknownFields(descriptor_->containing_type())) {
+      printer->Print(variables_,
+        "  unknownFields.mergeVarintField($number$, rawValue);\n");
+    }
+    printer->Print(variables_,
+      "} else {\n"
+      "  $set_oneof_case_message$;\n"
+      "  $oneof_name$_ = rawValue;\n"
+      "}\n");
   }
-  printer->Print(variables_,
-    "} else {\n"
-    "  $set_oneof_case_message$;\n"
-    "  $oneof_name$_ = value;\n"
-    "}\n");
 }
 
 void ImmutableEnumOneofFieldGenerator::
 GenerateSerializationCode(io::Printer* printer) const {
   printer->Print(variables_,
     "if ($has_oneof_case_message$) {\n"
-    "  output.writeEnum($number$, (($type$) $oneof_name$_).getNumber());\n"
+    "  output.writeEnum($number$, ((java.lang.Integer) $oneof_name$_));\n"
     "}\n");
 }
 
@@ -442,10 +520,36 @@ GenerateSerializedSizeCode(io::Printer* printer) const {
   printer->Print(variables_,
     "if ($has_oneof_case_message$) {\n"
     "  size += com.google.protobuf.CodedOutputStream\n"
-    "    .computeEnumSize($number$, (($type$) $oneof_name$_).getNumber());\n"
+    "    .computeEnumSize($number$, ((java.lang.Integer) $oneof_name$_));\n"
     "}\n");
 }
 
+void ImmutableEnumOneofFieldGenerator::
+GenerateEqualsCode(io::Printer* printer) const {
+  if (SupportUnknownEnumValue(descriptor_->file())) {
+    printer->Print(variables_,
+      "result = result && get$capitalized_name$Value()\n"
+      "    == other.get$capitalized_name$Value();\n");
+  } else {
+    printer->Print(variables_,
+      "result = result && get$capitalized_name$()\n"
+      "    .equals(other.get$capitalized_name$());\n");
+  }
+}
+
+void ImmutableEnumOneofFieldGenerator::
+GenerateHashCode(io::Printer* printer) const {
+  if (SupportUnknownEnumValue(descriptor_->file())) {
+    printer->Print(variables_,
+      "hash = (37 * hash) + $constant_name$;\n"
+      "hash = (53 * hash) + get$capitalized_name$Value();\n");
+  } else {
+    printer->Print(variables_,
+      "hash = (37 * hash) + $constant_name$;\n"
+      "hash = (53 * hash) + get$capitalized_name$().getNumber();\n");
+  }
+}
+
 // ===================================================================
 
 RepeatedImmutableEnumFieldGenerator::
@@ -482,17 +586,36 @@ GenerateInterfaceMembers(io::Printer* printer) const {
   WriteFieldDocComment(printer, descriptor_);
   printer->Print(variables_,
     "$deprecation$$type$ get$capitalized_name$(int index);\n");
+  if (SupportUnknownEnumValue(descriptor_->file())) {
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$java.util.List<java.lang.Integer>\n"
+      "get$capitalized_name$ValueList();\n");
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$int get$capitalized_name$Value(int index);\n");
+  }
 }
 
 void RepeatedImmutableEnumFieldGenerator::
 GenerateMembers(io::Printer* printer) const {
   printer->Print(variables_,
-    "private java.util.List<$type$> $name$_;\n");
+    "private java.util.List<java.lang.Integer> $name$_;\n"
+    "private static final com.google.protobuf.Internal.ListAdapter.Converter<\n"
+    "    java.lang.Integer, $type$> $name$_converter_ =\n"
+    "        new com.google.protobuf.Internal.ListAdapter.Converter<\n"
+    "            java.lang.Integer, $type$>() {\n"
+    "          public $type$ convert(java.lang.Integer from) {\n"
+    "            $type$ result = $type$.valueOf(from);\n"
+    "            return result == null ? $unknown$ : result;\n"
+    "          }\n"
+    "        };\n");
   PrintExtraFieldInfo(variables_, printer);
   WriteFieldDocComment(printer, descriptor_);
   printer->Print(variables_,
     "$deprecation$public java.util.List<$type$> get$capitalized_name$List() {\n"
-    "  return $name$_;\n"   // note:  unmodifiable list
+    "  return new com.google.protobuf.Internal.ListAdapter<\n"
+    "      java.lang.Integer, $type$>($name$_, $name$_converter_);\n"
     "}\n");
   WriteFieldDocComment(printer, descriptor_);
   printer->Print(variables_,
@@ -502,8 +625,21 @@ GenerateMembers(io::Printer* printer) const {
   WriteFieldDocComment(printer, descriptor_);
   printer->Print(variables_,
     "$deprecation$public $type$ get$capitalized_name$(int index) {\n"
-    "  return $name$_.get(index);\n"
+    "  return $name$_converter_.convert($name$_.get(index));\n"
     "}\n");
+  if (SupportUnknownEnumValue(descriptor_->file())) {
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$public java.util.List<java.lang.Integer>\n"
+      "get$capitalized_name$ValueList() {\n"
+      "  return $name$_;\n"
+      "}\n");
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$public int get$capitalized_name$Value(int index) {\n"
+      "  return $name$_.get(index);\n"
+      "}\n");
+  }
 
   if (descriptor_->options().packed() &&
       HasGeneratedMethods(descriptor_->containing_type())) {
@@ -524,12 +660,12 @@ GenerateBuilderMembers(io::Printer* printer) const {
     // memory allocations. Note, immutable is a strong guarantee here -- not
     // just that the list cannot be modified via the reference but that the
     // list can never be modified.
-    "private java.util.List<$type$> $name$_ =\n"
+    "private java.util.List<java.lang.Integer> $name$_ =\n"
     "  java.util.Collections.emptyList();\n"
 
     "private void ensure$capitalized_name$IsMutable() {\n"
     "  if (!$get_mutable_bit_builder$) {\n"
-    "    $name$_ = new java.util.ArrayList<$type$>($name$_);\n"
+    "    $name$_ = new java.util.ArrayList<java.lang.Integer>($name$_);\n"
     "    $set_mutable_bit_builder$;\n"
     "  }\n"
     "}\n");
@@ -541,7 +677,8 @@ GenerateBuilderMembers(io::Printer* printer) const {
     //   has been built, thus mutating the message which is supposed to be
     //   immutable.
     "$deprecation$public java.util.List<$type$> get$capitalized_name$List() {\n"
-    "  return java.util.Collections.unmodifiableList($name$_);\n"
+    "  return new com.google.protobuf.Internal.ListAdapter<\n"
+    "      java.lang.Integer, $type$>($name$_, $name$_converter_);\n"
     "}\n");
   WriteFieldDocComment(printer, descriptor_);
   printer->Print(variables_,
@@ -551,7 +688,7 @@ GenerateBuilderMembers(io::Printer* printer) const {
   WriteFieldDocComment(printer, descriptor_);
   printer->Print(variables_,
     "$deprecation$public $type$ get$capitalized_name$(int index) {\n"
-    "  return $name$_.get(index);\n"
+    "  return $name$_converter_.convert($name$_.get(index));\n"
     "}\n");
   WriteFieldDocComment(printer, descriptor_);
   printer->Print(variables_,
@@ -561,7 +698,7 @@ GenerateBuilderMembers(io::Printer* printer) const {
     "    throw new NullPointerException();\n"
     "  }\n"
     "  ensure$capitalized_name$IsMutable();\n"
-    "  $name$_.set(index, value);\n"
+    "  $name$_.set(index, value.getNumber());\n"
     "  $on_changed$\n"
     "  return this;\n"
     "}\n");
@@ -572,7 +709,7 @@ GenerateBuilderMembers(io::Printer* printer) const {
     "    throw new NullPointerException();\n"
     "  }\n"
     "  ensure$capitalized_name$IsMutable();\n"
-    "  $name$_.add(value);\n"
+    "  $name$_.add(value.getNumber());\n"
     "  $on_changed$\n"
     "  return this;\n"
     "}\n");
@@ -581,8 +718,9 @@ GenerateBuilderMembers(io::Printer* printer) const {
     "$deprecation$public Builder addAll$capitalized_name$(\n"
     "    java.lang.Iterable<? extends $type$> values) {\n"
     "  ensure$capitalized_name$IsMutable();\n"
-    "  com.google.protobuf.AbstractMessageLite.Builder.addAll(\n"
-    "      values, $name$_);\n"
+    "  for ($type$ value : values) {\n"
+    "    $name$_.add(value.getNumber());\n"
+    "  }\n"
     "  $on_changed$\n"
     "  return this;\n"
     "}\n");
@@ -594,6 +732,48 @@ GenerateBuilderMembers(io::Printer* printer) const {
     "  $on_changed$\n"
     "  return this;\n"
     "}\n");
+
+  if (SupportUnknownEnumValue(descriptor_->file())) {
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$public java.util.List<java.lang.Integer>\n"
+      "get$capitalized_name$ValueList() {\n"
+      "  return java.util.Collections.unmodifiableList($name$_);\n"
+      "}\n");
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$public int get$capitalized_name$Value(int index) {\n"
+      "  return $name$_.get(index);\n"
+      "}\n");
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$public Builder set$capitalized_name$Value(\n"
+      "    int index, int value) {\n"
+      "  ensure$capitalized_name$IsMutable();\n"
+      "  $name$_.set(index, value);\n"
+      "  $on_changed$\n"
+      "  return this;\n"
+      "}\n");
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$public Builder add$capitalized_name$Value(int value) {\n"
+      "  ensure$capitalized_name$IsMutable();\n"
+      "  $name$_.add(value);\n"
+      "  $on_changed$\n"
+      "  return this;\n"
+      "}\n");
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(variables_,
+      "$deprecation$public Builder addAll$capitalized_name$Value(\n"
+      "    java.lang.Iterable<java.lang.Integer> values) {\n"
+      "  ensure$capitalized_name$IsMutable();\n"
+      "  for (int value : values) {\n"
+      "    $name$_.add(value);\n"
+      "  }\n"
+      "  $on_changed$\n"
+      "  return this;\n"
+      "}\n");
+  }
 }
 
 void RepeatedImmutableEnumFieldGenerator::
@@ -648,26 +828,32 @@ GenerateBuildingCode(io::Printer* printer) const {
 void RepeatedImmutableEnumFieldGenerator::
 GenerateParsingCode(io::Printer* printer) const {
   // Read and store the enum
-  printer->Print(variables_,
-    "int rawValue = input.readEnum();\n"
-    "$type$ value = $type$.valueOf(rawValue);\n"
-    "if (value == null) {\n");
-  if (UseUnknownFieldSet(descriptor_->containing_type())) {
+  if (SupportUnknownEnumValue(descriptor_->file())) {
     printer->Print(variables_,
-      "  unknownFields.mergeVarintField($number$, rawValue);\n");
+      "int rawValue = input.readEnum();\n"
+      "if (!$get_mutable_bit_parser$) {\n"
+      "  $name$_ = new java.util.ArrayList<java.lang.Integer>();\n"
+      "  $set_mutable_bit_parser$;\n"
+      "}\n"
+      "$name$_.add(rawValue);\n");
   } else {
     printer->Print(variables_,
-      "  unknownFieldsCodedOutput.writeRawVarint32(tag);\n"
-      "  unknownFieldsCodedOutput.writeRawVarint32(rawValue);\n");
+      "int rawValue = input.readEnum();\n"
+      "$type$ value = $type$.valueOf(rawValue);\n"
+        "if (value == null) {\n");
+    if (PreserveUnknownFields(descriptor_->containing_type())) {
+      printer->Print(variables_,
+        "  unknownFields.mergeVarintField($number$, rawValue);\n");
+    }
+    printer->Print(variables_,
+      "} else {\n"
+      "  if (!$get_mutable_bit_parser$) {\n"
+      "    $name$_ = new java.util.ArrayList<java.lang.Integer>();\n"
+      "    $set_mutable_bit_parser$;\n"
+      "  }\n"
+      "  $name$_.add(rawValue);\n"
+      "}\n");
   }
-  printer->Print(variables_,
-    "  } else {\n"
-    "  if (!$get_mutable_bit_parser$) {\n"
-    "    $name$_ = new java.util.ArrayList<$type$>();\n"
-    "    $set_mutable_bit_parser$;\n"
-    "  }\n"
-    "  $name$_.add(value);\n"
-    "}\n");
 }
 
 void RepeatedImmutableEnumFieldGenerator::
@@ -705,12 +891,12 @@ GenerateSerializationCode(io::Printer* printer) const {
       "  output.writeRawVarint32($name$MemoizedSerializedSize);\n"
       "}\n"
       "for (int i = 0; i < $name$_.size(); i++) {\n"
-      "  output.writeEnumNoTag($name$_.get(i).getNumber());\n"
+      "  output.writeEnumNoTag($name$_.get(i));\n"
       "}\n");
   } else {
     printer->Print(variables_,
       "for (int i = 0; i < $name$_.size(); i++) {\n"
-      "  output.writeEnum($number$, $name$_.get(i).getNumber());\n"
+      "  output.writeEnum($number$, $name$_.get(i));\n"
       "}\n");
   }
 }
@@ -725,7 +911,7 @@ GenerateSerializedSizeCode(io::Printer* printer) const {
   printer->Print(variables_,
     "for (int i = 0; i < $name$_.size(); i++) {\n"
     "  dataSize += com.google.protobuf.CodedOutputStream\n"
-    "    .computeEnumSizeNoTag($name$_.get(i).getNumber());\n"
+    "    .computeEnumSizeNoTag($name$_.get(i));\n"
     "}\n");
   printer->Print(
     "size += dataSize;\n");
@@ -754,8 +940,7 @@ GenerateSerializedSizeCode(io::Printer* printer) const {
 void RepeatedImmutableEnumFieldGenerator::
 GenerateEqualsCode(io::Printer* printer) const {
   printer->Print(variables_,
-    "result = result && get$capitalized_name$List()\n"
-    "    .equals(other.get$capitalized_name$List());\n");
+    "result = result && $name$_.equals(other.$name$_);\n");
 }
 
 void RepeatedImmutableEnumFieldGenerator::
@@ -763,8 +948,7 @@ GenerateHashCode(io::Printer* printer) const {
   printer->Print(variables_,
     "if (get$capitalized_name$Count() > 0) {\n"
     "  hash = (37 * hash) + $constant_name$;\n"
-    "  hash = (53 * hash) + com.google.protobuf.Internal.hashEnumList(\n"
-    "      get$capitalized_name$List());\n"
+    "  hash = (53 * hash) + $name$_.hashCode();\n"
     "}\n");
 }
 
diff --git a/src/google/protobuf/compiler/java/java_enum_field.h b/src/google/protobuf/compiler/java/java_enum_field.h
index 6a9535aa..b8ff7343 100644
--- a/src/google/protobuf/compiler/java/java_enum_field.h
+++ b/src/google/protobuf/compiler/java/java_enum_field.h
@@ -106,6 +106,8 @@ class ImmutableEnumOneofFieldGenerator : public ImmutableEnumFieldGenerator {
   void GenerateParsingCode(io::Printer* printer) const;
   void GenerateSerializationCode(io::Printer* printer) const;
   void GenerateSerializedSizeCode(io::Printer* printer) const;
+  void GenerateEqualsCode(io::Printer* printer) const;
+  void GenerateHashCode(io::Printer* printer) const;
 
  private:
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ImmutableEnumOneofFieldGenerator);
diff --git a/src/google/protobuf/compiler/java/java_field.cc b/src/google/protobuf/compiler/java/java_field.cc
index d7b0f3fc..49635bb4 100644
--- a/src/google/protobuf/compiler/java/java_field.cc
+++ b/src/google/protobuf/compiler/java/java_field.cc
@@ -35,12 +35,16 @@
 #include <google/protobuf/compiler/java/java_field.h>
 
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 
 #include <google/protobuf/stubs/common.h>
 #include <google/protobuf/compiler/java/java_context.h>
 #include <google/protobuf/compiler/java/java_enum_field.h>
 #include <google/protobuf/compiler/java/java_helpers.h>
 #include <google/protobuf/compiler/java/java_lazy_message_field.h>
+#include <google/protobuf/compiler/java/java_map_field.h>
 #include <google/protobuf/compiler/java/java_message_field.h>
 #include <google/protobuf/compiler/java/java_primitive_field.h>
 #include <google/protobuf/compiler/java/java_string_field.h>
@@ -48,6 +52,7 @@
 #include <google/protobuf/stubs/strutil.h>
 #include <google/protobuf/stubs/substitute.h>
 
+
 namespace google {
 namespace protobuf {
 namespace compiler {
@@ -61,12 +66,17 @@ ImmutableFieldGenerator* MakeImmutableGenerator(
   if (field->is_repeated()) {
     switch (GetJavaType(field)) {
       case JAVATYPE_MESSAGE:
-        if (IsLazy(field)) {
-          return new RepeatedImmutableLazyMessageFieldGenerator(
+        if (IsMapEntry(field->message_type())) {
+          return new ImmutableMapFieldGenerator(
               field, messageBitIndex, builderBitIndex, context);
         } else {
-          return new RepeatedImmutableMessageFieldGenerator(
-              field, messageBitIndex, builderBitIndex, context);
+          if (IsLazy(field)) {
+            return new RepeatedImmutableLazyMessageFieldGenerator(
+                field, messageBitIndex, builderBitIndex, context);
+          } else {
+            return new RepeatedImmutableMessageFieldGenerator(
+                field, messageBitIndex, builderBitIndex, context);
+          }
         }
       case JAVATYPE_ENUM:
         return new RepeatedImmutableEnumFieldGenerator(
diff --git a/src/google/protobuf/compiler/java/java_field.h b/src/google/protobuf/compiler/java/java_field.h
index db339d5b..5bc5634e 100644
--- a/src/google/protobuf/compiler/java/java_field.h
+++ b/src/google/protobuf/compiler/java/java_field.h
@@ -37,6 +37,9 @@
 
 #include <map>
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <string>
 
 #include <google/protobuf/stubs/common.h>
diff --git a/src/google/protobuf/compiler/java/java_file.cc b/src/google/protobuf/compiler/java/java_file.cc
index 231b1445..1ac945cd 100644
--- a/src/google/protobuf/compiler/java/java_file.cc
+++ b/src/google/protobuf/compiler/java/java_file.cc
@@ -35,6 +35,9 @@
 #include <google/protobuf/compiler/java/java_file.h>
 
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 
 #include <google/protobuf/compiler/java/java_context.h>
 #include <google/protobuf/compiler/java/java_enum.h>
@@ -180,29 +183,6 @@ bool FileGenerator::Validate(string* error) {
       "option to specify a different outer class name for the .proto file.");
     return false;
   }
-  // If java_outer_classname option is not set and the default outer class name
-  // conflicts with a type defined in the message, we will append a suffix to
-  // avoid the conflict. This allows proto1 API protos to be dual-compiled into
-  // proto2 API without code change. When this happens we'd like to issue an
-  // warning to let the user know that the outer class name has been changed.
-  // Although we only do this automatic naming fix for immutable API, mutable
-  // outer class name will also be affected as it's contructed from immutable
-  // outer class name with an additional "Mutable" prefix. Since the naming
-  // change in mutable API is not caused by a naming conflict, we generate the
-  // warning for immutable API only.
-  if (immutable_api_ && !file_->options().has_java_outer_classname()) {
-    string default_classname =
-        name_resolver_->GetFileDefaultImmutableClassName(file_);
-    if (default_classname != classname_) {
-      GOOGLE_LOG(WARNING) << file_->name() << ": The default outer class name, \""
-                   << default_classname << "\", conflicts with a type "
-                   << "declared in the proto file and an alternative outer "
-                   << "class name is used: \"" << classname_ << "\". To avoid "
-                   << "this warning, please use the java_outer_classname "
-                   << "option to specify a different outer class name for "
-                   << "the .proto file.";
-    }
-  }
   return true;
 }
 
@@ -323,6 +303,7 @@ void FileGenerator::GenerateDescriptorInitializationCodeForImmutable(
   SharedCodeGenerator shared_code_generator(file_);
   shared_code_generator.GenerateDescriptors(printer);
 
+
   for (int i = 0; i < file_->message_type_count(); i++) {
     message_generators_[i]->GenerateStaticVariableInitializers(printer);
   }
diff --git a/src/google/protobuf/compiler/java/java_file.h b/src/google/protobuf/compiler/java/java_file.h
index c805b9a6..0b2230a0 100644
--- a/src/google/protobuf/compiler/java/java_file.h
+++ b/src/google/protobuf/compiler/java/java_file.h
@@ -36,6 +36,9 @@
 #define GOOGLE_PROTOBUF_COMPILER_JAVA_FILE_H__
 
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <string>
 #include <vector>
 #include <google/protobuf/stubs/common.h>
diff --git a/src/google/protobuf/compiler/java/java_generator.cc b/src/google/protobuf/compiler/java/java_generator.cc
index c3a47e3e..a743ce22 100644
--- a/src/google/protobuf/compiler/java/java_generator.cc
+++ b/src/google/protobuf/compiler/java/java_generator.cc
@@ -35,6 +35,9 @@
 #include <google/protobuf/compiler/java/java_generator.h>
 
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 
 #include <google/protobuf/compiler/java/java_file.h>
 #include <google/protobuf/compiler/java/java_generator_factory.h>
@@ -99,10 +102,14 @@ bool JavaGenerator::Generate(const FileDescriptor* file,
 
   vector<string> all_files;
 
+
   vector<FileGenerator*> file_generators;
   if (generate_immutable_code) {
     file_generators.push_back(new FileGenerator(file, /* immutable = */ true));
   }
+  if (generate_mutable_code) {
+    file_generators.push_back(new FileGenerator(file, /* mutable = */ false));
+  }
   for (int i = 0; i < file_generators.size(); ++i) {
     if (!file_generators[i]->Validate(error)) {
       for (int j = 0; j < file_generators.size(); ++j) {
diff --git a/src/google/protobuf/compiler/java/java_helpers.cc b/src/google/protobuf/compiler/java/java_helpers.cc
index 3efd7edb..23685385 100644
--- a/src/google/protobuf/compiler/java/java_helpers.cc
+++ b/src/google/protobuf/compiler/java/java_helpers.cc
@@ -306,6 +306,26 @@ JavaType GetJavaType(const FieldDescriptor* field) {
   return JAVATYPE_INT;
 }
 
+const char* PrimitiveTypeName(JavaType type) {
+  switch (type) {
+    case JAVATYPE_INT    : return "int";
+    case JAVATYPE_LONG   : return "long";
+    case JAVATYPE_FLOAT  : return "float";
+    case JAVATYPE_DOUBLE : return "double";
+    case JAVATYPE_BOOLEAN: return "boolean";
+    case JAVATYPE_STRING : return "java.lang.String";
+    case JAVATYPE_BYTES  : return "com.google.protobuf.ByteString";
+    case JAVATYPE_ENUM   : return NULL;
+    case JAVATYPE_MESSAGE: return NULL;
+
+    // No default because we want the compiler to complain if any new
+    // JavaTypes are added.
+  }
+
+  GOOGLE_LOG(FATAL) << "Can't get here.";
+  return NULL;
+}
+
 const char* BoxedPrimitiveTypeName(JavaType type) {
   switch (type) {
     case JAVATYPE_INT    : return "java.lang.Integer";
diff --git a/src/google/protobuf/compiler/java/java_helpers.h b/src/google/protobuf/compiler/java/java_helpers.h
index 93f23a93..2707fa0a 100644
--- a/src/google/protobuf/compiler/java/java_helpers.h
+++ b/src/google/protobuf/compiler/java/java_helpers.h
@@ -149,6 +149,8 @@ enum JavaType {
 
 JavaType GetJavaType(const FieldDescriptor* field);
 
+const char* PrimitiveTypeName(JavaType type);
+
 // Get the fully-qualified class name for a boxed primitive type, e.g.
 // "java.lang.Integer" for JAVATYPE_INT.  Returns NULL for enum and message
 // types.
@@ -168,13 +170,6 @@ inline string ImmutableDefaultValue(const FieldDescriptor* field,
 }
 bool IsDefaultValueJavaDefault(const FieldDescriptor* field);
 
-// Does this message class use UnknownFieldSet?
-// Otherwise, unknown fields will be stored in a ByteString object
-inline bool UseUnknownFieldSet(const Descriptor* descriptor) {
-  return descriptor->file()->options().optimize_for() !=
-           FileOptions::LITE_RUNTIME;
-}
-
 // Does this message class have generated parsing, serialization, and other
 // standard methods for which reflection-based fallback implementations exist?
 inline bool HasGeneratedMethods(const Descriptor* descriptor) {
@@ -308,12 +303,27 @@ bool HasRequiredFields(const Descriptor* descriptor);
 
 // Whether a .proto file supports field presence test for non-message types.
 inline bool SupportFieldPresence(const FileDescriptor* descriptor) {
-  return true;
+  return descriptor->syntax() != FileDescriptor::SYNTAX_PROTO3;
+}
+
+// Whether unknown enum values are kept (i.e., not stored in UnknownFieldSet
+// but in the message and can be queried using additional getters that return
+// ints.
+inline bool SupportUnknownEnumValue(const FileDescriptor* descriptor) {
+  return descriptor->syntax() == FileDescriptor::SYNTAX_PROTO3;
 }
 
 // Check whether a mesasge has repeated fields.
 bool HasRepeatedFields(const Descriptor* descriptor);
 
+inline bool IsMapEntry(const Descriptor* descriptor) {
+  return descriptor->options().map_entry();
+}
+
+inline bool PreserveUnknownFields(const Descriptor* descriptor) {
+  return descriptor->file()->syntax() != FileDescriptor::SYNTAX_PROTO3;
+}
+
 }  // namespace java
 }  // namespace compiler
 }  // namespace protobuf
diff --git a/src/google/protobuf/compiler/java/java_map_field.cc b/src/google/protobuf/compiler/java/java_map_field.cc
new file mode 100644
index 00000000..2986f51f
--- /dev/null
+++ b/src/google/protobuf/compiler/java/java_map_field.cc
@@ -0,0 +1,455 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/compiler/java/java_map_field.h>
+
+#include <google/protobuf/compiler/java/java_context.h>
+#include <google/protobuf/compiler/java/java_doc_comment.h>
+#include <google/protobuf/compiler/java/java_helpers.h>
+#include <google/protobuf/compiler/java/java_name_resolver.h>
+#include <google/protobuf/io/printer.h>
+
+namespace google {
+namespace protobuf {
+namespace compiler {
+namespace java {
+
+namespace {
+
+const FieldDescriptor* KeyField(const FieldDescriptor* descriptor) {
+  GOOGLE_CHECK_EQ(FieldDescriptor::TYPE_MESSAGE, descriptor->type());
+  const Descriptor* message = descriptor->message_type();
+  GOOGLE_CHECK(message->options().map_entry());
+  return message->FindFieldByName("key");
+}
+
+const FieldDescriptor* ValueField(const FieldDescriptor* descriptor) {
+  GOOGLE_CHECK_EQ(FieldDescriptor::TYPE_MESSAGE, descriptor->type());
+  const Descriptor* message = descriptor->message_type();
+  GOOGLE_CHECK(message->options().map_entry());
+  return message->FindFieldByName("value");
+}
+
+string TypeName(const FieldDescriptor* field,
+                ClassNameResolver* name_resolver,
+                bool boxed) {
+  if (GetJavaType(field) == JAVATYPE_MESSAGE) {
+    return name_resolver->GetImmutableClassName(field->message_type());
+  } else if (GetJavaType(field) == JAVATYPE_ENUM) {
+    return name_resolver->GetImmutableClassName(field->enum_type());
+  } else {
+    return boxed ? BoxedPrimitiveTypeName(GetJavaType(field))
+                 : PrimitiveTypeName(GetJavaType(field));
+  }
+}
+
+string WireType(const FieldDescriptor* field) {
+  return "com.google.protobuf.WireFormat.FieldType." +
+      string(FieldTypeName(field->type()));
+}
+
+void SetMessageVariables(const FieldDescriptor* descriptor,
+                         int messageBitIndex,
+                         int builderBitIndex,
+                         const FieldGeneratorInfo* info,
+                         ClassNameResolver* name_resolver,
+                         map<string, string>* variables) {
+  SetCommonFieldVariables(descriptor, info, variables);
+
+  (*variables)["type"] =
+      name_resolver->GetImmutableClassName(descriptor->message_type());
+  const FieldDescriptor* key = KeyField(descriptor);
+  const FieldDescriptor* value = ValueField(descriptor);
+  (*variables)["key_type"] = TypeName(key, name_resolver, false);
+  (*variables)["boxed_key_type"] = TypeName(key, name_resolver, true);
+  (*variables)["key_wire_type"] = WireType(key);
+  (*variables)["key_default_value"] = DefaultValue(key, true, name_resolver);
+  if (GetJavaType(value) == JAVATYPE_ENUM) {
+    // We store enums as Integers internally.
+    (*variables)["value_type"] = "int";
+    (*variables)["boxed_value_type"] = "java.lang.Integer";
+    (*variables)["value_wire_type"] = WireType(value);
+    (*variables)["value_default_value"] =
+        DefaultValue(value, true, name_resolver) + ".getNumber()";
+
+    (*variables)["value_enum_type"] = TypeName(value, name_resolver, false);
+
+    if (SupportUnknownEnumValue(descriptor->file())) {
+      // Map unknown values to a special UNRECOGNIZED value if supported.
+      (*variables)["unrecognized_value"] =
+          (*variables)["value_enum_type"] + ".UNRECOGNIZED";
+    } else {
+      // Map unknown values to the default value if we don't have UNRECOGNIZED.
+      (*variables)["unrecognized_value"] =
+          DefaultValue(value, true, name_resolver);
+    }
+  } else {
+    (*variables)["value_type"] = TypeName(value, name_resolver, false);
+    (*variables)["boxed_value_type"] = TypeName(value, name_resolver, true);
+    (*variables)["value_wire_type"] = WireType(value);
+    (*variables)["value_default_value"] =
+        DefaultValue(value, true, name_resolver);
+  }
+  (*variables)["type_parameters"] =
+      (*variables)["boxed_key_type"] + ", " + (*variables)["boxed_value_type"];
+  // TODO(birdo): Add @deprecated javadoc when generating javadoc is supported
+  // by the proto compiler
+  (*variables)["deprecation"] = descriptor->options().deprecated()
+      ? "@java.lang.Deprecated " : "";
+  (*variables)["on_changed"] =
+      HasDescriptorMethods(descriptor->containing_type()) ? "onChanged();" : "";
+
+  // For repeated fields, one bit is used for whether the array is immutable
+  // in the parsing constructor.
+  (*variables)["get_mutable_bit_parser"] =
+      GenerateGetBitMutableLocal(builderBitIndex);
+  (*variables)["set_mutable_bit_parser"] =
+      GenerateSetBitMutableLocal(builderBitIndex);
+
+  if (HasDescriptorMethods(descriptor->file())) {
+    (*variables)["lite"] = "";
+    (*variables)["map_field_parameter"] = (*variables)["name"] + "DefaultEntry";
+    (*variables)["descriptor"] =
+        name_resolver->GetImmutableClassName(descriptor->file()) +
+        ".internal_" + UniqueFileScopeIdentifier(descriptor->message_type()) +
+        "_descriptor, ";
+  } else {
+    (*variables)["lite"] = "Lite";
+    (*variables)["map_field_parameter"] = "";
+    (*variables)["descriptor"] = "";
+  }
+}
+
+}  // namespace
+
+ImmutableMapFieldGenerator::
+ImmutableMapFieldGenerator(const FieldDescriptor* descriptor,
+                                       int messageBitIndex,
+                                       int builderBitIndex,
+                                       Context* context)
+  : descriptor_(descriptor), messageBitIndex_(messageBitIndex),
+    builderBitIndex_(builderBitIndex), context_(context),
+    name_resolver_(context->GetNameResolver())  {
+  SetMessageVariables(descriptor, messageBitIndex, builderBitIndex,
+                      context->GetFieldGeneratorInfo(descriptor),
+                      name_resolver_, &variables_);
+}
+
+ImmutableMapFieldGenerator::
+~ImmutableMapFieldGenerator() {}
+
+int ImmutableMapFieldGenerator::GetNumBitsForMessage() const {
+  return 0;
+}
+
+int ImmutableMapFieldGenerator::GetNumBitsForBuilder() const {
+  return 1;
+}
+
+void ImmutableMapFieldGenerator::
+GenerateInterfaceMembers(io::Printer* printer) const {
+  if (GetJavaType(ValueField(descriptor_)) == JAVATYPE_ENUM) {
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(
+        variables_,
+        "$deprecation$java.util.Map<$boxed_key_type$, $value_enum_type$>\n"
+        "get$capitalized_name$();\n");
+    if (SupportUnknownEnumValue(descriptor_->file())) {
+      WriteFieldDocComment(printer, descriptor_);
+      printer->Print(
+          variables_,
+          "$deprecation$java.util.Map<$type_parameters$>\n"
+          "get$capitalized_name$Value();\n");
+    }
+  } else {
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(
+        variables_,
+        "$deprecation$java.util.Map<$type_parameters$>\n"
+        "get$capitalized_name$();\n");
+  }
+}
+
+void ImmutableMapFieldGenerator::
+GenerateMembers(io::Printer* printer) const {
+  printer->Print(
+      variables_,
+      "private static final com.google.protobuf.MapEntry$lite$<\n"
+      "    $type_parameters$> $name$DefaultEntry =\n"
+      "        com.google.protobuf.MapEntry$lite$\n"
+      "        .<$type_parameters$>newDefaultInstance(\n"
+      "            $descriptor$\n"
+      "            $key_wire_type$,\n"
+      "            $key_default_value$,\n"
+      "            $value_wire_type$,\n"
+      "            $value_default_value$);\n");
+  printer->Print(
+      variables_,
+      "private com.google.protobuf.MapField$lite$<\n"
+      "    $type_parameters$> $name$_ =\n"
+      "        com.google.protobuf.MapField$lite$.emptyMapField(\n"
+      "            $map_field_parameter$);\n"
+      "\n");
+  if (GetJavaType(ValueField(descriptor_)) == JAVATYPE_ENUM) {
+    printer->Print(
+        variables_,
+        "private static final\n"
+        "com.google.protobuf.Internal.MapAdapter.Converter<\n"
+        "    java.lang.Integer, $value_enum_type$> $name$ValueConverter =\n"
+        "        com.google.protobuf.Internal.MapAdapter.newEnumConverter(\n"
+        "            $value_enum_type$.internalGetValueMap(),\n"
+        "            $unrecognized_value$);\n");
+    if (SupportUnknownEnumValue(descriptor_->file())) {
+      WriteFieldDocComment(printer, descriptor_);
+      printer->Print(
+          variables_,
+          "$deprecation$\n"
+          "public java.util.Map<$boxed_key_type$, $boxed_value_type$>\n"
+          "get$capitalized_name$Value() {\n"
+          "  return $name$_.getMap();\n"
+          "}\n");
+    }
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(
+        variables_,
+        "$deprecation$\n"
+        "public java.util.Map<$boxed_key_type$, $value_enum_type$>\n"
+        "get$capitalized_name$() {\n"
+        "  return new com.google.protobuf.Internal.MapAdapter<\n"
+        "      $boxed_key_type$, $value_enum_type$, java.lang.Integer>(\n"
+        "          $name$_.getMap(), $name$ValueConverter);\n"
+        "}\n");
+  } else {
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(
+        variables_,
+        "$deprecation$\n"
+        "public java.util.Map<$type_parameters$> get$capitalized_name$() {\n"
+        "  return $name$_.getMap();\n"
+        "}\n");
+  }
+}
+
+void ImmutableMapFieldGenerator::
+GenerateBuilderMembers(io::Printer* printer) const {
+  printer->Print(
+      variables_,
+      "private com.google.protobuf.MapField$lite$<\n"
+      "    $type_parameters$> $name$_ =\n"
+      "        com.google.protobuf.MapField$lite$.newMapField(\n"
+      "            $map_field_parameter$);\n"
+      "\n");
+  if (GetJavaType(ValueField(descriptor_)) == JAVATYPE_ENUM) {
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(
+        variables_,
+        "$deprecation$\n"
+        "public java.util.Map<$boxed_key_type$, $value_enum_type$>\n"
+        "get$capitalized_name$() {\n"
+        "  return new com.google.protobuf.Internal.MapAdapter<\n"
+        "      $boxed_key_type$, $value_enum_type$, java.lang.Integer>(\n"
+        "          $name$_.getMap(), $name$ValueConverter);\n"
+        "}\n");
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(
+        variables_,
+        "$deprecation$\n"
+        "public java.util.Map<$boxed_key_type$, $value_enum_type$>\n"
+        "getMutable$capitalized_name$() {\n"
+        "  $on_changed$\n"
+        "  return new com.google.protobuf.Internal.MapAdapter<\n"
+        "      $boxed_key_type$, $value_enum_type$, java.lang.Integer>(\n"
+        "          $name$_.getMutableMap(), $name$ValueConverter);\n"
+        "}\n");
+    if (SupportUnknownEnumValue(descriptor_->file())) {
+      WriteFieldDocComment(printer, descriptor_);
+      printer->Print(
+          variables_,
+          "$deprecation$\n"
+          "public java.util.Map<$boxed_key_type$, $boxed_value_type$>\n"
+          "get$capitalized_name$Value() {\n"
+          "  return $name$_.getMap();\n"
+          "}\n");
+      WriteFieldDocComment(printer, descriptor_);
+      printer->Print(
+          variables_,
+          "$deprecation$\n"
+          "public java.util.Map<$boxed_key_type$, $boxed_value_type$>\n"
+          "getMutable$capitalized_name$Value() {\n"
+          "  $on_changed$\n"
+          "  return $name$_.getMutableMap();\n"
+          "}\n");
+    }
+  } else {
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(
+        variables_,
+        "public java.util.Map<$type_parameters$> get$capitalized_name$() {\n"
+        "  return $name$_.getMap();\n"
+        "}\n");
+    WriteFieldDocComment(printer, descriptor_);
+    printer->Print(
+        variables_,
+        "public java.util.Map<$type_parameters$>\n"
+        "getMutable$capitalized_name$() {\n"
+        "  $on_changed$\n"
+        "  return $name$_.getMutableMap();\n"
+        "}\n");
+  }
+}
+
+void ImmutableMapFieldGenerator::
+GenerateFieldBuilderInitializationCode(io::Printer* printer)  const {
+  // Nothing to initialize.
+}
+
+void ImmutableMapFieldGenerator::
+GenerateInitializationCode(io::Printer* printer) const {
+  // Nothing to initialize.
+}
+
+void ImmutableMapFieldGenerator::
+GenerateBuilderClearCode(io::Printer* printer) const {
+  printer->Print(
+      variables_,
+      "$name$_.clear();\n");
+}
+
+void ImmutableMapFieldGenerator::
+GenerateMergingCode(io::Printer* printer) const {
+  printer->Print(
+      variables_,
+      "$name$_.mergeFrom(other.$name$_);\n");
+}
+
+void ImmutableMapFieldGenerator::
+GenerateBuildingCode(io::Printer* printer) const {
+  printer->Print(
+      variables_,
+      // We do a copy of the map field to ensure that the built result is
+      // immutable. Implementation of this copy() method can do copy-on-write
+      // to defer this copy until further modifications are made on the field.
+      "result.$name$_ = $name$_.copy();\n");
+}
+
+void ImmutableMapFieldGenerator::
+GenerateParsingCode(io::Printer* printer) const {
+  printer->Print(
+      variables_,
+      "if (!$get_mutable_bit_parser$) {\n"
+      "  $name$_ = com.google.protobuf.MapField$lite$.newMapField(\n"
+      "      $map_field_parameter$);\n"
+      "  $set_mutable_bit_parser$;\n"
+      "}\n");
+  if (!SupportUnknownEnumValue(descriptor_->file()) &&
+      GetJavaType(ValueField(descriptor_)) == JAVATYPE_ENUM) {
+    printer->Print(
+        variables_,
+        "com.google.protobuf.ByteString bytes = input.readBytes();\n"
+        "com.google.protobuf.MapEntry$lite$<$type_parameters$>\n"
+        "$name$ = $name$DefaultEntry.getParserForType().parseFrom(bytes);\n");
+    printer->Print(
+        variables_,
+        "if ($value_enum_type$.valueOf($name$.getValue()) == null) {\n"
+        "  unknownFields.mergeLengthDelimitedField($number$, bytes);\n"
+        "} else {\n"
+        "  $name$_.getMutableMap().put($name$.getKey(), $name$.getValue());\n"
+        "}\n");
+  } else {
+    printer->Print(
+        variables_,
+        "com.google.protobuf.MapEntry$lite$<$type_parameters$>\n"
+        "$name$ = input.readMessage(\n"
+        "    $name$DefaultEntry.getParserForType(), extensionRegistry);\n"
+        "$name$_.getMutableMap().put($name$.getKey(), $name$.getValue());\n");
+  }
+}
+
+void ImmutableMapFieldGenerator::
+GenerateParsingDoneCode(io::Printer* printer) const {
+  // Nothing to do here.
+}
+
+void ImmutableMapFieldGenerator::
+GenerateSerializationCode(io::Printer* printer) const {
+  printer->Print(
+      variables_,
+      "for (java.util.Map.Entry<$type_parameters$> entry\n"
+      "     : $name$_.getMap().entrySet()) {\n"
+      "  com.google.protobuf.MapEntry$lite$<$type_parameters$>\n"
+      "  $name$ = $name$DefaultEntry.newBuilderForType()\n"
+      "      .setKey(entry.getKey())\n"
+      "      .setValue(entry.getValue())\n"
+      "      .build();\n"
+      "  output.writeMessage($number$, $name$);\n"
+      "}\n");
+}
+
+void ImmutableMapFieldGenerator::
+GenerateSerializedSizeCode(io::Printer* printer) const {
+  printer->Print(
+      variables_,
+      "for (java.util.Map.Entry<$type_parameters$> entry\n"
+      "     : $name$_.getMap().entrySet()) {\n"
+      "  com.google.protobuf.MapEntry$lite$<$type_parameters$>\n"
+      "  $name$ = $name$DefaultEntry.newBuilderForType()\n"
+      "      .setKey(entry.getKey())\n"
+      "      .setValue(entry.getValue())\n"
+      "      .build();\n"
+      "  size += com.google.protobuf.CodedOutputStream\n"
+      "      .computeMessageSize($number$, $name$);\n"
+      "}\n");
+}
+
+void ImmutableMapFieldGenerator::
+GenerateEqualsCode(io::Printer* printer) const {
+  printer->Print(
+      variables_,
+      "result = result && $name$_.equals(other.$name$_);\n");
+}
+
+void ImmutableMapFieldGenerator::
+GenerateHashCode(io::Printer* printer) const {
+  printer->Print(
+      variables_,
+      "if (!$name$_.getMap().isEmpty()) {\n"
+      "  hash = (37 * hash) + $constant_name$;\n"
+      "  hash = (53 * hash) + $name$_.hashCode();\n"
+      "}\n");
+}
+
+string ImmutableMapFieldGenerator::GetBoxedType() const {
+  return name_resolver_->GetImmutableClassName(descriptor_->message_type());
+}
+
+}  // namespace java
+}  // namespace compiler
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/compiler/java/java_map_field.h b/src/google/protobuf/compiler/java/java_map_field.h
new file mode 100644
index 00000000..80a94f45
--- /dev/null
+++ b/src/google/protobuf/compiler/java/java_map_field.h
@@ -0,0 +1,82 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_COMPILER_JAVA_MAP_FIELD_H__
+#define GOOGLE_PROTOBUF_COMPILER_JAVA_MAP_FIELD_H__
+
+#include <google/protobuf/compiler/java/java_field.h>
+
+namespace google {
+namespace protobuf {
+namespace compiler {
+namespace java {
+
+class ImmutableMapFieldGenerator : public ImmutableFieldGenerator {
+ public:
+  explicit ImmutableMapFieldGenerator(
+      const FieldDescriptor* descriptor, int messageBitIndex,
+      int builderBitIndex, Context* context);
+  ~ImmutableMapFieldGenerator();
+
+  // implements ImmutableFieldGenerator ---------------------------------------
+  int GetNumBitsForMessage() const;
+  int GetNumBitsForBuilder() const;
+  void GenerateInterfaceMembers(io::Printer* printer) const;
+  void GenerateMembers(io::Printer* printer) const;
+  void GenerateBuilderMembers(io::Printer* printer) const;
+  void GenerateInitializationCode(io::Printer* printer) const;
+  void GenerateBuilderClearCode(io::Printer* printer) const;
+  void GenerateMergingCode(io::Printer* printer) const;
+  void GenerateBuildingCode(io::Printer* printer) const;
+  void GenerateParsingCode(io::Printer* printer) const;
+  void GenerateParsingDoneCode(io::Printer* printer) const;
+  void GenerateSerializationCode(io::Printer* printer) const;
+  void GenerateSerializedSizeCode(io::Printer* printer) const;
+  void GenerateFieldBuilderInitializationCode(io::Printer* printer) const;
+  void GenerateEqualsCode(io::Printer* printer) const;
+  void GenerateHashCode(io::Printer* printer) const;
+
+  string GetBoxedType() const;
+
+ private:
+  const FieldDescriptor* descriptor_;
+  map<string, string> variables_;
+  const int messageBitIndex_;
+  const int builderBitIndex_;
+  Context* context_;
+  ClassNameResolver* name_resolver_;
+};
+
+}  // namespace java
+}  // namespace compiler
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_COMPILER_JAVA_MAP_FIELD_H__
diff --git a/src/google/protobuf/compiler/java/java_message.cc b/src/google/protobuf/compiler/java/java_message.cc
index 8aa89ac7..dd1ad6a6 100644
--- a/src/google/protobuf/compiler/java/java_message.cc
+++ b/src/google/protobuf/compiler/java/java_message.cc
@@ -38,6 +38,9 @@
 #include <google/protobuf/stubs/hash.h>
 #include <map>
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <vector>
 
 #include <google/protobuf/compiler/java/java_context.h>
@@ -264,60 +267,36 @@ void ImmutableMessageGenerator::Generate(io::Printer* printer) {
     descriptor_->containing_type() == NULL &&
     MultipleJavaFiles(descriptor_->file(), /* immutable = */ true);
 
+  map<string, string> variables;
+  variables["static"] = is_own_file ? " " : " static ";
+  variables["classname"] = descriptor_->name();
+  variables["extra_interfaces"] = ExtraMessageInterfaces(descriptor_);
+  variables["lite"] = HasDescriptorMethods(descriptor_) ? "" : "Lite";
+
   WriteMessageDocComment(printer, descriptor_);
 
   // The builder_type stores the super type name of the nested Builder class.
   string builder_type;
   if (descriptor_->extension_range_count() > 0) {
-    if (HasDescriptorMethods(descriptor_)) {
-      printer->Print(
-        "public$static$final class $classname$ extends\n"
-        "    com.google.protobuf.GeneratedMessage.ExtendableMessage<\n"
-        "      $classname$> implements\n"
-        "    $extra_interfaces$\n"
-        "    $classname$OrBuilder {\n",
-        "static", is_own_file ? " " : " static ",
-        "classname", descriptor_->name(),
-        "extra_interfaces", ExtraMessageInterfaces(descriptor_));
-      builder_type = strings::Substitute(
-          "com.google.protobuf.GeneratedMessage.ExtendableBuilder<$0, ?>",
-          name_resolver_->GetImmutableClassName(descriptor_));
-    } else {
-      printer->Print(
-        "public$static$final class $classname$ extends\n"
-        "    com.google.protobuf.GeneratedMessageLite.ExtendableMessage<\n"
-        "      $classname$> implements\n"
-        "    $extra_interfaces$\n"
-        "    $classname$OrBuilder {\n",
-        "static", is_own_file ? " " : " static ",
-        "classname", descriptor_->name(),
-        "extra_interfaces", ExtraMessageInterfaces(descriptor_));
-      builder_type = strings::Substitute(
-          "com.google.protobuf.GeneratedMessageLite.ExtendableBuilder<$0, ?>",
-          name_resolver_->GetImmutableClassName(descriptor_));
-    }
+    printer->Print(variables,
+      "public $static$final class $classname$ extends\n"
+      "    com.google.protobuf.GeneratedMessage$lite$.ExtendableMessage<\n"
+      "      $classname$> implements\n"
+      "    $extra_interfaces$\n"
+      "    $classname$OrBuilder {\n");
+    builder_type = strings::Substitute(
+        "com.google.protobuf.GeneratedMessage$1.ExtendableBuilder<$0, ?>",
+        name_resolver_->GetImmutableClassName(descriptor_),
+        variables["lite"]);
   } else {
-    if (HasDescriptorMethods(descriptor_)) {
-      printer->Print(
-        "public$static$final class $classname$ extends\n"
-        "    com.google.protobuf.GeneratedMessage implements\n"
-        "    $extra_interfaces$\n"
-        "    $classname$OrBuilder {\n",
-        "static", is_own_file ? " " : " static ",
-        "classname", descriptor_->name(),
-        "extra_interfaces", ExtraMessageInterfaces(descriptor_));
-      builder_type = "com.google.protobuf.GeneratedMessage.Builder<?>";
-    } else {
-      printer->Print(
-        "public$static$final class $classname$ extends\n"
-        "    com.google.protobuf.GeneratedMessageLite implements\n"
-        "    $extra_interfaces$\n"
-        "    $classname$OrBuilder {\n",
-        "static", is_own_file ? " " : " static ",
-        "classname", descriptor_->name(),
-        "extra_interfaces", ExtraMessageInterfaces(descriptor_));
-      builder_type = "com.google.protobuf.GeneratedMessageLite.Builder";
-    }
+    printer->Print(variables,
+      "public $static$final class $classname$ extends\n"
+      "    com.google.protobuf.GeneratedMessage$lite$ implements\n"
+      "    $extra_interfaces$\n"
+      "    $classname$OrBuilder {\n");
+    builder_type = strings::Substitute(
+        "com.google.protobuf.GeneratedMessage$0.Builder",
+        variables["lite"]);
   }
   printer->Indent();
   // Using builder_type, instead of Builder, prevents the Builder class from
@@ -328,16 +307,22 @@ void ImmutableMessageGenerator::Generate(io::Printer* printer) {
     "// Use $classname$.newBuilder() to construct.\n"
     "private $classname$($buildertype$ builder) {\n"
     "  super(builder);\n"
-    "$set_unknown_fields$\n"
     "}\n",
     "classname", descriptor_->name(),
-    "buildertype", builder_type,
-    "set_unknown_fields",
-    "  this.unknownFields = builder.getUnknownFields();");
+    "buildertype", builder_type);
   printer->Print(
-    // Used when constructing the default instance, which cannot be initialized
-    // immediately because it may cyclically refer to other default instances.
-    "private $classname$(boolean noInit) {$set_default_unknown_fields$}\n"
+    "private $classname$() {\n",
+    "classname", descriptor_->name());
+  printer->Indent();
+  for (int i = 0; i < descriptor_->field_count(); i++) {
+    if (!descriptor_->field(i)->containing_oneof()) {
+      field_generators_.get(descriptor_->field(i))
+          .GenerateInitializationCode(printer);
+    }
+  }
+  printer->Outdent();
+  printer->Print(
+    "}\n"
     "\n"
     "private static final $classname$ defaultInstance;\n"
     "public static $classname$ getDefaultInstance() {\n"
@@ -349,23 +334,22 @@ void ImmutableMessageGenerator::Generate(io::Printer* printer) {
     "}\n"
     "\n",
     "classname", descriptor_->name(),
-    "set_default_unknown_fields", UseUnknownFieldSet(descriptor_)
-        ? " this.unknownFields ="
-          " com.google.protobuf.UnknownFieldSet.getDefaultInstance(); "
-        : " this.unknownFields = com.google.protobuf.ByteString.EMPTY;");
+    "lite", variables["lite"]);
 
-  if (UseUnknownFieldSet(descriptor_)) {
+  if (HasDescriptorMethods(descriptor_)) {
     printer->Print(
-        "private final com.google.protobuf.UnknownFieldSet unknownFields;\n"
-        ""
-        "@java.lang.Override\n"
-        "public final com.google.protobuf.UnknownFieldSet\n"
-        "    getUnknownFields() {\n"
-        "  return this.unknownFields;\n"
-        "}\n");
-  } else {
+      "@java.lang.Override\n"
+      "public final com.google.protobuf.UnknownFieldSet\n"
+      "getUnknownFields() {\n");
+    if (PreserveUnknownFields(descriptor_)) {
+      printer->Print(
+        "  return this.unknownFields;\n");
+    } else {
+      printer->Print(
+        "  return com.google.protobuf.UnknownFieldSet.getDefaultInstance();\n");
+    }
     printer->Print(
-        "private final com.google.protobuf.ByteString unknownFields;\n");
+      "}\n");
   }
 
   if (HasGeneratedMethods(descriptor_)) {
@@ -382,6 +366,8 @@ void ImmutableMessageGenerator::Generate(io::Printer* printer) {
   }
 
   for (int i = 0; i < descriptor_->nested_type_count(); i++) {
+    // Don't generate Java classes for map entry messages.
+    if (IsMapEntry(descriptor_->nested_type(i))) continue;
     ImmutableMessageGenerator messageGenerator(
         descriptor_->nested_type(i), context_);
     messageGenerator.GenerateInterface(printer);
@@ -480,20 +466,6 @@ void ImmutableMessageGenerator::Generate(io::Printer* printer) {
     printer->Print("\n");
   }
 
-  // Called by the constructor, except in the case of the default instance,
-  // in which case this is called by static init code later on.
-  printer->Print("private void initFields() {\n");
-  printer->Indent();
-  for (int i = 0; i < descriptor_->field_count(); i++) {
-    if (!descriptor_->field(i)->containing_oneof()) {
-      field_generators_.get(descriptor_->field(i))
-          .GenerateInitializationCode(printer);
-    }
-  }
-
-  printer->Outdent();
-  printer->Print("}\n");
-
   if (HasGeneratedMethods(descriptor_)) {
     GenerateIsInitialized(printer, MEMOIZE);
     GenerateMessageSerializationMethods(printer);
@@ -512,8 +484,7 @@ void ImmutableMessageGenerator::Generate(io::Printer* printer) {
   printer->Print(
     "\n"
     "static {\n"
-    "  defaultInstance = new $classname$(true);\n"
-    "  defaultInstance.initFields();\n"
+    "  defaultInstance = new $classname$();\n"
     "}\n"
     "\n"
     "// @@protoc_insertion_point(class_scope:$full_name$)\n",
@@ -593,17 +564,15 @@ GenerateMessageSerializationMethods(io::Printer* printer) {
     }
   }
 
-  if (UseUnknownFieldSet(descriptor_)) {
-    if (descriptor_->options().message_set_wire_format()) {
+  if (PreserveUnknownFields(descriptor_)) {
+    if (descriptor_->options().message_set_wire_format()
+        && HasDescriptorMethods(descriptor_)) {
       printer->Print(
-        "getUnknownFields().writeAsMessageSetTo(output);\n");
+        "unknownFields.writeAsMessageSetTo(output);\n");
     } else {
       printer->Print(
-        "getUnknownFields().writeTo(output);\n");
+        "unknownFields.writeTo(output);\n");
     }
-  } else {
-    printer->Print(
-      "output.writeRawBytes(unknownFields);\n");
   }
 
   printer->Outdent();
@@ -632,17 +601,15 @@ GenerateMessageSerializationMethods(io::Printer* printer) {
     }
   }
 
-  if (UseUnknownFieldSet(descriptor_)) {
-    if (descriptor_->options().message_set_wire_format()) {
+  if (PreserveUnknownFields(descriptor_)) {
+    if (descriptor_->options().message_set_wire_format()
+        && HasDescriptorMethods(descriptor_)) {
       printer->Print(
-        "size += getUnknownFields().getSerializedSizeAsMessageSet();\n");
+        "size += unknownFields.getSerializedSizeAsMessageSet();\n");
     } else {
       printer->Print(
-        "size += getUnknownFields().getSerializedSize();\n");
+        "size += unknownFields.getSerializedSize();\n");
     }
-  } else {
-    printer->Print(
-      "size += unknownFields.size();\n");
   }
 
   printer->Outdent();
@@ -653,13 +620,7 @@ GenerateMessageSerializationMethods(io::Printer* printer) {
     "\n");
 
   printer->Print(
-    "private static final long serialVersionUID = 0L;\n"
-    "@java.lang.Override\n"
-    "protected java.lang.Object writeReplace()\n"
-    "    throws java.io.ObjectStreamException {\n"
-    "  return super.writeReplace();\n"
-    "}\n"
-    "\n");
+    "private static final long serialVersionUID = 0L;\n");
 }
 
 void ImmutableMessageGenerator::
@@ -740,7 +701,7 @@ void ImmutableMessageGenerator::GenerateSerializeOneExtensionRange(
 
 void ImmutableMessageGenerator::GenerateBuilder(io::Printer* printer) {
   printer->Print(
-    "public static Builder newBuilder() { return Builder.create(); }\n"
+    "public static Builder newBuilder() { return new Builder(); }\n"
     "public Builder newBuilderForType() { return newBuilder(); }\n"
     "public static Builder newBuilder($classname$ prototype) {\n"
     "  return newBuilder().mergeFrom(prototype);\n"
@@ -809,7 +770,6 @@ void ImmutableMessageGenerator::GenerateBuilder(io::Printer* printer) {
 
   if (HasGeneratedMethods(descriptor_)) {
     GenerateIsInitialized(printer, DONT_MEMOIZE);
-    GenerateBuilderParsingMethods(printer);
   }
 
   // oneof
@@ -864,6 +824,20 @@ void ImmutableMessageGenerator::GenerateBuilder(io::Printer* printer) {
                      .GenerateBuilderMembers(printer);
   }
 
+  if (!PreserveUnknownFields(descriptor_)) {
+    printer->Print(
+      "public final Builder setUnknownFields(\n"
+      "    final com.google.protobuf.UnknownFieldSet unknownFields) {\n"
+      "  return this;\n"
+      "}\n"
+      "\n"
+      "public final Builder mergeUnknownFields(\n"
+      "    final com.google.protobuf.UnknownFieldSet unknownFields) {\n"
+      "  return this;\n"
+      "}\n"
+      "\n");
+  }
+
   printer->Print(
     "\n"
     "// @@protoc_insertion_point(builder_scope:$full_name$)\n",
@@ -886,6 +860,41 @@ GenerateDescriptorMethods(io::Printer* printer) {
         "fileclass", name_resolver_->GetImmutableClassName(descriptor_->file()),
         "identifier", UniqueFileScopeIdentifier(descriptor_));
     }
+    vector<const FieldDescriptor*> map_fields;
+    for (int i = 0; i < descriptor_->field_count(); i++) {
+      const FieldDescriptor* field = descriptor_->field(i);
+      if (GetJavaType(field) == JAVATYPE_MESSAGE &&
+          IsMapEntry(field->message_type())) {
+        map_fields.push_back(field);
+      }
+    }
+    if (!map_fields.empty()) {
+      printer->Print(
+        "@SuppressWarnings({\"rawtypes\"})\n"
+        "protected com.google.protobuf.MapField internalGetMapField(\n"
+        "    int number) {\n"
+        "  switch (number) {\n");
+      printer->Indent();
+      printer->Indent();
+      for (int i = 0; i < map_fields.size(); ++i) {
+        const FieldDescriptor* field = map_fields[i];
+        const FieldGeneratorInfo* info = context_->GetFieldGeneratorInfo(field);
+        printer->Print(
+          "case $number$:\n"
+          "  return $name$_;\n",
+          "number", SimpleItoa(field->number()),
+          "name", info->name);
+      }
+      printer->Print(
+          "default:\n"
+          "  throw new RuntimeException(\n"
+          "      \"Invalid map field number: \" + number);\n");
+      printer->Outdent();
+      printer->Outdent();
+      printer->Print(
+          "  }\n"
+          "}\n");
+    }
     printer->Print(
       "protected com.google.protobuf.GeneratedMessage.FieldAccessorTable\n"
       "    internalGetFieldAccessorTable() {\n"
@@ -949,13 +958,8 @@ GenerateCommonBuilderMethods(io::Printer* printer) {
   }
 
   printer->Print(
-    "private static Builder create() {\n"
-    "  return new Builder();\n"
-    "}\n"
-    "\n"
     "public Builder clear() {\n"
-    "  super.clear();\n",
-    "classname", name_resolver_->GetImmutableClassName(descriptor_));
+    "  super.clear();\n");
 
   printer->Indent();
 
@@ -979,12 +983,8 @@ GenerateCommonBuilderMethods(io::Printer* printer) {
   printer->Print(
     "  return this;\n"
     "}\n"
-    "\n"
-    "public Builder clone() {\n"
-    "  return create().mergeFrom(buildPartial());\n"
-    "}\n"
-    "\n",
-    "classname", name_resolver_->GetImmutableClassName(descriptor_));
+    "\n");
+
   if (HasDescriptorMethods(descriptor_)) {
     printer->Print(
       "public com.google.protobuf.Descriptors.Descriptor\n"
@@ -1153,13 +1153,13 @@ GenerateCommonBuilderMethods(io::Printer* printer) {
         "  this.mergeExtensionFields(other);\n");
     }
 
-    if (UseUnknownFieldSet(descriptor_)) {
+    if (PreserveUnknownFields(descriptor_)) {
       printer->Print(
-        "  this.mergeUnknownFields(other.getUnknownFields());\n");
-    } else {
-      printer->Print(
-        "  setUnknownFields(\n"
-        "      getUnknownFields().concat(other.unknownFields));\n");
+        "  this.mergeUnknownFields(other.unknownFields);\n");
+    }
+
+    if (HasDescriptorMethods(descriptor_)) {
+      printer->Print("  onChanged();\n");
     }
 
     printer->Print(
@@ -1171,31 +1171,6 @@ GenerateCommonBuilderMethods(io::Printer* printer) {
 
 // ===================================================================
 
-void ImmutableMessageGenerator::
-GenerateBuilderParsingMethods(io::Printer* printer) {
-  printer->Print(
-    "public Builder mergeFrom(\n"
-    "    com.google.protobuf.CodedInputStream input,\n"
-    "    com.google.protobuf.ExtensionRegistryLite extensionRegistry)\n"
-    "    throws java.io.IOException {\n"
-    "  $classname$ parsedMessage = null;\n"
-    "  try {\n"
-    "    parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);\n"
-    "  } catch (com.google.protobuf.InvalidProtocolBufferException e) {\n"
-    "    parsedMessage = ($classname$) e.getUnfinishedMessage();\n"
-    "    throw e;\n"
-    "  } finally {\n"
-    "    if (parsedMessage != null) {\n"
-    "      mergeFrom(parsedMessage);\n"
-    "    }\n"
-    "  }\n"
-    "  return this;\n"
-    "}\n",
-    "classname", name_resolver_->GetImmutableClassName(descriptor_));
-}
-
-// ===================================================================
-
 void ImmutableMessageGenerator::GenerateIsInitialized(
     io::Printer* printer, UseMemoization useMemoization) {
   bool memoization = useMemoization == MEMOIZE;
@@ -1256,15 +1231,26 @@ void ImmutableMessageGenerator::GenerateIsInitialized(
             "memoize", memoization ? "memoizedIsInitialized = 0;" : "");
           break;
         case FieldDescriptor::LABEL_OPTIONAL:
+          if (!SupportFieldPresence(descriptor_->file()) &&
+              field->containing_oneof() != NULL) {
+            const OneofDescriptor* oneof = field->containing_oneof();
+            const OneofGeneratorInfo* oneof_info =
+                context_->GetOneofGeneratorInfo(oneof);
+            printer->Print(
+              "if ($oneof_name$Case_ == $field_number$) {\n",
+              "oneof_name", oneof_info->name,
+              "field_number", SimpleItoa(field->number()));
+          } else {
+            printer->Print(
+              "if (has$name$()) {\n",
+              "name", info->capitalized_name);
+          }
           printer->Print(
-            "if (has$name$()) {\n"
             "  if (!get$name$().isInitialized()) {\n"
             "    $memoize$\n"
             "    return false;\n"
             "  }\n"
             "}\n",
-            "type", name_resolver_->GetImmutableClassName(
-                field->message_type()),
             "name", info->capitalized_name,
             "memoize", memoization ? "memoizedIsInitialized = 0;" : "");
           break;
@@ -1358,10 +1344,14 @@ GenerateEqualsAndHashCode(io::Printer* printer) {
         "}\n");
     }
   }
-  if (HasDescriptorMethods(descriptor_)) {
+  if (PreserveUnknownFields(descriptor_)) {
+    // Always consider unknown fields for equality. This will sometimes return
+    // false for non-canonical ordering when running in LITE_RUNTIME but it's
+    // the best we can do.
     printer->Print(
-      "result = result &&\n"
-      "    getUnknownFields().equals(other.getUnknownFields());\n");
+      "result = result && unknownFields.equals(other.unknownFields);\n");
+  }
+  if (HasDescriptorMethods(descriptor_)) {
     if (descriptor_->extension_range_count() > 0) {
       printer->Print(
         "result = result &&\n"
@@ -1421,13 +1411,8 @@ GenerateEqualsAndHashCode(io::Printer* printer) {
     }
   }
 
-  if (UseUnknownFieldSet(descriptor_)) {
-    printer->Print(
-      "hash = (29 * hash) + getUnknownFields().hashCode();\n");
-  } else {
-    printer->Print(
-      "hash = (29 * hash) + unknownFields.hashCode();\n");
-  }
+  printer->Print(
+    "hash = (29 * hash) + unknownFields.hashCode();\n");
   printer->Print(
     "memoizedHashCode = hash;\n"
     "return hash;\n");
@@ -1468,7 +1453,7 @@ GenerateParsingConstructor(io::Printer* printer) {
 
   // Initialize all fields to default.
   printer->Print(
-      "initFields();\n");
+      "this();\n");
 
   // Use builder bits to track mutable repeated fields.
   int totalBuilderBits = 0;
@@ -1483,17 +1468,16 @@ GenerateParsingConstructor(io::Printer* printer) {
       "bit_field_name", GetBitFieldName(i));
   }
 
-  if (UseUnknownFieldSet(descriptor_)) {
-    printer->Print(
-      "com.google.protobuf.UnknownFieldSet.Builder unknownFields =\n"
-      "    com.google.protobuf.UnknownFieldSet.newBuilder();\n");
-  } else {
-    printer->Print(
-      "com.google.protobuf.ByteString.Output unknownFieldsOutput =\n"
-      "    com.google.protobuf.ByteString.newOutput();\n"
-      "com.google.protobuf.CodedOutputStream unknownFieldsCodedOutput =\n"
-      "    com.google.protobuf.CodedOutputStream.newInstance(\n"
-      "        unknownFieldsOutput);\n");
+  if (PreserveUnknownFields(descriptor_)) {
+    if (HasDescriptorMethods(descriptor_)) {
+      printer->Print(
+        "com.google.protobuf.UnknownFieldSet.Builder unknownFields =\n"
+        "    com.google.protobuf.UnknownFieldSet.newBuilder();\n");
+    } else {
+      printer->Print(
+        "com.google.protobuf.UnknownFieldSetLite.Builder unknownFields =\n"
+        "    com.google.protobuf.UnknownFieldSetLite.newBuilder();\n");
+    }
   }
 
   printer->Print(
@@ -1513,16 +1497,41 @@ GenerateParsingConstructor(io::Printer* printer) {
   printer->Print(
     "case 0:\n"          // zero signals EOF / limit reached
     "  done = true;\n"
-    "  break;\n"
-    "default: {\n"
-    "  if (!parseUnknownField(input,$unknown_fields$\n"
-    "                         extensionRegistry, tag)) {\n"
-    "    done = true;\n"  // it's an endgroup tag
-    "  }\n"
-    "  break;\n"
-    "}\n",
-    "unknown_fields", UseUnknownFieldSet(descriptor_)
-        ? " unknownFields," : " unknownFieldsCodedOutput,");
+    "  break;\n");
+
+  if (PreserveUnknownFields(descriptor_)) {
+    if (!HasDescriptorMethods(descriptor_)
+        && descriptor_->extension_range_count() > 0) {
+      // Lite runtime directly invokes parseUnknownField to reduce method
+      // counts.
+      printer->Print(
+        "default: {\n"
+        "  if (!parseUnknownField(extensions, getDefaultInstanceForType(),\n"
+        "                         input, unknownFields,\n"
+        "                         extensionRegistry, tag)) {\n"
+        "    done = true;\n"  // it's an endgroup tag
+        "  }\n"
+        "  break;\n"
+        "}\n");
+    } else {
+      printer->Print(
+        "default: {\n"
+        "  if (!parseUnknownField(input, unknownFields,\n"
+        "                         extensionRegistry, tag)) {\n"
+        "    done = true;\n"  // it's an endgroup tag
+        "  }\n"
+        "  break;\n"
+        "}\n");
+    }
+  } else {
+    printer->Print(
+      "default: {\n"
+      "  if (!input.skipField(tag)) {\n"
+      "    done = true;\n"  // it's an endgroup tag
+      "  }\n"
+      "  break;\n"
+      "}\n");
+  }
 
   for (int i = 0; i < descriptor_->field_count(); i++) {
     const FieldDescriptor* field = sorted_fields[i];
@@ -1582,19 +1591,9 @@ GenerateParsingConstructor(io::Printer* printer) {
     field_generators_.get(field).GenerateParsingDoneCode(printer);
   }
 
-  // Make unknown fields immutable.
-  if (UseUnknownFieldSet(descriptor_)) {
-    printer->Print(
-        "this.unknownFields = unknownFields.build();\n");
-  } else {
-    printer->Print(
-        "try {\n"
-        "  unknownFieldsCodedOutput.flush();\n"
-        "} catch (java.io.IOException e) {\n"
-        "// Should not happen\n"
-        "} finally {\n"
-        "  unknownFields = unknownFieldsOutput.toByteString();\n"
-        "}\n");
+  if (PreserveUnknownFields(descriptor_)) {
+    // Make unknown fields immutable.
+    printer->Print("this.unknownFields = unknownFields.build();\n");
   }
 
   // Make extensions immutable.
@@ -1611,7 +1610,7 @@ GenerateParsingConstructor(io::Printer* printer) {
 // ===================================================================
 void ImmutableMessageGenerator::GenerateParser(io::Printer* printer) {
   printer->Print(
-      "public static com.google.protobuf.Parser<$classname$> PARSER =\n"
+      "public static final com.google.protobuf.Parser<$classname$> PARSER =\n"
       "    new com.google.protobuf.AbstractParser<$classname$>() {\n",
       "classname", descriptor_->name());
   printer->Indent();
diff --git a/src/google/protobuf/compiler/java/java_message.h b/src/google/protobuf/compiler/java/java_message.h
index fece1c21..2703016e 100644
--- a/src/google/protobuf/compiler/java/java_message.h
+++ b/src/google/protobuf/compiler/java/java_message.h
@@ -118,7 +118,6 @@ class ImmutableMessageGenerator : public MessageGenerator {
   void GenerateBuilder(io::Printer* printer);
   void GenerateCommonBuilderMethods(io::Printer* printer);
   void GenerateDescriptorMethods(io::Printer* printer);
-  void GenerateBuilderParsingMethods(io::Printer* printer);
   void GenerateIsInitialized(io::Printer* printer,
       UseMemoization useMemoization);
   void GenerateEqualsAndHashCode(io::Printer* printer);
diff --git a/src/google/protobuf/compiler/java/java_message_field.cc b/src/google/protobuf/compiler/java/java_message_field.cc
index e681314e..538f1248 100644
--- a/src/google/protobuf/compiler/java/java_message_field.cc
+++ b/src/google/protobuf/compiler/java/java_message_field.cc
@@ -179,7 +179,7 @@ GenerateMembers(io::Printer* printer) const {
     WriteFieldDocComment(printer, descriptor_);
     printer->Print(variables_,
       "$deprecation$public $type$ get$capitalized_name$() {\n"
-      "  return $name$_;\n"
+      "  return $name$_ == null ? $type$.getDefaultInstance() : $name$_;\n"
       "}\n");
 
     if (HasNestedBuilders(descriptor_->containing_type())) {
@@ -187,7 +187,7 @@ GenerateMembers(io::Printer* printer) const {
       printer->Print(variables_,
         "$deprecation$public $type$OrBuilder "
         "get$capitalized_name$OrBuilder() {\n"
-        "  return $name$_;\n"
+        "  return $name$_ == null ? $type$.getDefaultInstance() : $name$_;\n"
         "}\n");
     }
   } else {
@@ -257,14 +257,8 @@ GenerateBuilderMembers(io::Printer* printer) const {
 
   bool support_field_presence = SupportFieldPresence(descriptor_->file());
 
-  if (support_field_presence) {
-    printer->Print(variables_,
-      // Used when the builder is null.
-      "private $type$ $name$_ = $type$.getDefaultInstance();\n");
-  } else {
-    printer->Print(variables_,
-      "private $type$ $name$_ = null;\n");
-  }
+  printer->Print(variables_,
+    "private $type$ $name$_ = null;\n");
 
   if (HasNestedBuilders(descriptor_->containing_type())) {
     printer->Print(variables_,
@@ -296,13 +290,8 @@ GenerateBuilderMembers(io::Printer* printer) const {
   WriteFieldDocComment(printer, descriptor_);
   PrintNestedBuilderFunction(printer,
     "$deprecation$public $type$ get$capitalized_name$()",
-
-    support_field_presence
-        ?  "return $name$_;\n"
-        : "return $name$_ == null ? $type$.getDefaultInstance() : $name$_;\n",
-
+    "return $name$_ == null ? $type$.getDefaultInstance() : $name$_;\n",
     "return $name$Builder_.getMessage();\n",
-
     NULL);
 
   // Field.Builder setField(Field value)
@@ -342,6 +331,7 @@ GenerateBuilderMembers(io::Printer* printer) const {
 
     support_field_presence
         ? "if ($get_has_field_bit_builder$ &&\n"
+          "    $name$_ != null &&\n"
           "    $name$_ != $type$.getDefaultInstance()) {\n"
           "  $name$_ =\n"
           "    $type$.newBuilder($name$_).mergeFrom(value).buildPartial();\n"
@@ -367,11 +357,8 @@ GenerateBuilderMembers(io::Printer* printer) const {
   PrintNestedBuilderFunction(printer,
     "$deprecation$public Builder clear$capitalized_name$()",
 
-    support_field_presence
-        ? "$name$_ = $type$.getDefaultInstance();\n"
-          "$on_changed$\n"
-        : "$name$_ = null;\n"
-          "$on_changed$\n",
+    "$name$_ = null;\n"
+    "$on_changed$\n",
 
     support_field_presence
         ? "$name$Builder_.clear();\n"
@@ -394,16 +381,9 @@ GenerateBuilderMembers(io::Printer* printer) const {
       "$deprecation$public $type$OrBuilder get$capitalized_name$OrBuilder() {\n"
       "  if ($name$Builder_ != null) {\n"
       "    return $name$Builder_.getMessageOrBuilder();\n"
-      "  } else {\n");
-    if (support_field_presence) {
-      printer->Print(variables_,
-        "    return $name$_;\n");
-    } else {
-      printer->Print(variables_,
-        "    return $name$_ == null ?\n"
-        "        $type$.getDefaultInstance() : $name$_;\n");
-    }
-    printer->Print(variables_,
+      "  } else {\n"
+      "    return $name$_ == null ?\n"
+      "        $type$.getDefaultInstance() : $name$_;\n"
       "  }\n"
       "}\n");
     WriteFieldDocComment(printer, descriptor_);
@@ -434,17 +414,13 @@ GenerateFieldBuilderInitializationCode(io::Printer* printer)  const {
 
 
 void ImmutableMessageFieldGenerator::
-GenerateInitializationCode(io::Printer* printer) const {
-  if (SupportFieldPresence(descriptor_->file())) {
-    printer->Print(variables_, "$name$_ = $type$.getDefaultInstance();\n");
-  }
-}
+GenerateInitializationCode(io::Printer* printer) const {}
 
 void ImmutableMessageFieldGenerator::
 GenerateBuilderClearCode(io::Printer* printer) const {
   if (SupportFieldPresence(descriptor_->file())) {
     PrintNestedBuilderCondition(printer,
-      "$name$_ = $type$.getDefaultInstance();\n",
+      "$name$_ = null;\n",
 
       "$name$Builder_.clear();\n");
     printer->Print(variables_, "$clear_has_field_bit_builder$\n");
@@ -514,7 +490,7 @@ void ImmutableMessageFieldGenerator::
 GenerateSerializationCode(io::Printer* printer) const {
   printer->Print(variables_,
     "if ($is_field_present_message$) {\n"
-    "  output.write$group_or_message$($number$, $name$_);\n"
+    "  output.write$group_or_message$($number$, get$capitalized_name$());\n"
     "}\n");
 }
 
@@ -523,7 +499,7 @@ GenerateSerializedSizeCode(io::Printer* printer) const {
   printer->Print(variables_,
     "if ($is_field_present_message$) {\n"
     "  size += com.google.protobuf.CodedOutputStream\n"
-    "    .compute$group_or_message$Size($number$, $name$_);\n"
+    "    .compute$group_or_message$Size($number$, get$capitalized_name$());\n"
     "}\n");
 }
 
diff --git a/src/google/protobuf/compiler/java/java_plugin_unittest.cc b/src/google/protobuf/compiler/java/java_plugin_unittest.cc
index c4d6995d..45aa8ffe 100644
--- a/src/google/protobuf/compiler/java/java_plugin_unittest.cc
+++ b/src/google/protobuf/compiler/java/java_plugin_unittest.cc
@@ -35,6 +35,9 @@
 //   worth.
 
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 
 #include <google/protobuf/compiler/java/java_generator.h>
 #include <google/protobuf/compiler/command_line_interface.h>
diff --git a/src/google/protobuf/compiler/java/java_primitive_field.cc b/src/google/protobuf/compiler/java/java_primitive_field.cc
index 6713d29a..e331d7a4 100644
--- a/src/google/protobuf/compiler/java/java_primitive_field.cc
+++ b/src/google/protobuf/compiler/java/java_primitive_field.cc
@@ -55,26 +55,6 @@ using internal::WireFormatLite;
 
 namespace {
 
-const char* PrimitiveTypeName(JavaType type) {
-  switch (type) {
-    case JAVATYPE_INT    : return "int";
-    case JAVATYPE_LONG   : return "long";
-    case JAVATYPE_FLOAT  : return "float";
-    case JAVATYPE_DOUBLE : return "double";
-    case JAVATYPE_BOOLEAN: return "boolean";
-    case JAVATYPE_STRING : return "java.lang.String";
-    case JAVATYPE_BYTES  : return "com.google.protobuf.ByteString";
-    case JAVATYPE_ENUM   : return NULL;
-    case JAVATYPE_MESSAGE: return NULL;
-
-    // No default because we want the compiler to complain if any new
-    // JavaTypes are added.
-  }
-
-  GOOGLE_LOG(FATAL) << "Can't get here.";
-  return NULL;
-}
-
 void SetPrimitiveVariables(const FieldDescriptor* descriptor,
                            int messageBitIndex,
                            int builderBitIndex,
diff --git a/src/google/protobuf/compiler/java/java_shared_code_generator.cc b/src/google/protobuf/compiler/java/java_shared_code_generator.cc
index ea77f792..f8723f2a 100644
--- a/src/google/protobuf/compiler/java/java_shared_code_generator.cc
+++ b/src/google/protobuf/compiler/java/java_shared_code_generator.cc
@@ -33,6 +33,9 @@
 #include <google/protobuf/compiler/java/java_shared_code_generator.h>
 
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 
 #include <google/protobuf/compiler/java/java_helpers.h>
 #include <google/protobuf/compiler/java/java_name_resolver.h>
@@ -176,7 +179,8 @@ void SharedCodeGenerator::GenerateDescriptors(io::Printer* printer) {
   // Invoke internalBuildGeneratedFileFrom() to build the file.
   printer->Print(
     "com.google.protobuf.Descriptors.FileDescriptor\n"
-    "  .internalBuildGeneratedFileFrom(descriptorData,\n"
+    "  .internalBuildGeneratedFileFrom(descriptorData,\n");
+  printer->Print(
     "    new com.google.protobuf.Descriptors.FileDescriptor[] {\n");
 
   for (int i = 0; i < dependencies.size(); i++) {
diff --git a/src/google/protobuf/compiler/java/java_shared_code_generator.h b/src/google/protobuf/compiler/java/java_shared_code_generator.h
index 1bb2f3dc..fdbe2ce8 100644
--- a/src/google/protobuf/compiler/java/java_shared_code_generator.h
+++ b/src/google/protobuf/compiler/java/java_shared_code_generator.h
@@ -36,6 +36,9 @@
 #define GOOGLE_PROTOBUF_COMPILER_JAVA_SHARED_CODE_GENERATOR_H__
 
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <string>
 #include <vector>
 
@@ -68,6 +71,7 @@ class SharedCodeGenerator {
 
   void Generate(GeneratorContext* generator_context,
                 vector<string>* file_list);
+
   void GenerateDescriptors(io::Printer* printer);
 
  private:
diff --git a/src/google/protobuf/compiler/java/java_string_field.cc b/src/google/protobuf/compiler/java/java_string_field.cc
index 8889a744..1c9302af 100644
--- a/src/google/protobuf/compiler/java/java_string_field.cc
+++ b/src/google/protobuf/compiler/java/java_string_field.cc
@@ -407,6 +407,15 @@ GenerateParsingCode(io::Printer* printer) const {
       "String s = input.readStringRequireUtf8();\n"
       "$set_has_field_bit_message$\n"
       "$name$_ = s;\n");
+  } else if (!HasDescriptorMethods(descriptor_->file())) {
+    // Lite runtime should attempt to reduce allocations by attempting to
+    // construct the string directly from the input stream buffer. This avoids
+    // spurious intermediary ByteString allocations, cutting overall allocations
+    // in half.
+    printer->Print(variables_,
+      "String s = input.readString();\n"
+      "$set_has_field_bit_message$\n"
+      "$name$_ = s;\n");
   } else {
     printer->Print(variables_,
       "com.google.protobuf.ByteString bs = input.readBytes();\n"
@@ -659,6 +668,15 @@ GenerateParsingCode(io::Printer* printer) const {
       "String s = input.readStringRequireUtf8();\n"
       "$set_oneof_case_message$;\n"
       "$oneof_name$_ = s;\n}\n");
+  } else if (!HasDescriptorMethods(descriptor_->file())) {
+    // Lite runtime should attempt to reduce allocations by attempting to
+    // construct the string directly from the input stream buffer. This avoids
+    // spurious intermediary ByteString allocations, cutting overall allocations
+    // in half.
+    printer->Print(variables_,
+      "String s = input.readString();\n"
+      "$set_oneof_case_message$;\n"
+      "$oneof_name$_ = s;\n");
   } else {
     printer->Print(variables_,
       "com.google.protobuf.ByteString bs = input.readBytes();\n"
@@ -923,6 +941,13 @@ GenerateParsingCode(io::Printer* printer) const {
   if (CheckUtf8(descriptor_)) {
     printer->Print(variables_,
     "String s = input.readStringRequireUtf8();\n");
+  } else if (!HasDescriptorMethods(descriptor_->file())) {
+    // Lite runtime should attempt to reduce allocations by attempting to
+    // construct the string directly from the input stream buffer. This avoids
+    // spurious intermediary ByteString allocations, cutting overall allocations
+    // in half.
+    printer->Print(variables_,
+    "String s = input.readString();\n");
   } else {
     printer->Print(variables_,
     "com.google.protobuf.ByteString bs = input.readBytes();\n");
@@ -932,7 +957,7 @@ GenerateParsingCode(io::Printer* printer) const {
     "  $name$_ = new com.google.protobuf.LazyStringArrayList();\n"
     "  $set_mutable_bit_parser$;\n"
     "}\n");
-  if (CheckUtf8(descriptor_)) {
+  if (CheckUtf8(descriptor_) || !HasDescriptorMethods(descriptor_->file())) {
     printer->Print(variables_,
       "$name$_.add(s);\n");
   } else {
diff --git a/src/google/protobuf/compiler/mock_code_generator.cc b/src/google/protobuf/compiler/mock_code_generator.cc
index 916b0ccd..70373c8e 100644
--- a/src/google/protobuf/compiler/mock_code_generator.cc
+++ b/src/google/protobuf/compiler/mock_code_generator.cc
@@ -33,6 +33,9 @@
 #include <google/protobuf/compiler/mock_code_generator.h>
 
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 
 #include <google/protobuf/testing/file.h>
 #include <google/protobuf/descriptor.pb.h>
diff --git a/src/google/protobuf/compiler/parser.cc b/src/google/protobuf/compiler/parser.cc
index 474a8f80..0ed80d54 100644
--- a/src/google/protobuf/compiler/parser.cc
+++ b/src/google/protobuf/compiler/parser.cc
@@ -84,6 +84,32 @@ TypeNameMap MakeTypeNameTable() {
 
 const TypeNameMap kTypeNames = MakeTypeNameTable();
 
+// Camel-case the field name and append "Entry" for generated map entry name.
+// e.g. map<KeyType, ValueType> foo_map => FooMapEntry
+string MapEntryName(const string& field_name) {
+  string result;
+  static const char kSuffix[] = "Entry";
+  result.reserve(field_name.size() + sizeof(kSuffix));
+  bool cap_next = true;
+  for (int i = 0; i < field_name.size(); ++i) {
+    if (field_name[i] == '_') {
+      cap_next = true;
+    } else if (cap_next) {
+      // Note: Do not use ctype.h due to locales.
+      if ('a' <= field_name[i] && field_name[i] <= 'z') {
+        result.push_back(field_name[i] - 'a' + 'A');
+      } else {
+        result.push_back(field_name[i]);
+      }
+      cap_next = false;
+    } else {
+      result.push_back(field_name[i]);
+    }
+  }
+  result.append(kSuffix);
+  return result;
+}
+
 }  // anonymous namespace
 
 // Makes code slightly more readable.  The meaning of "DO(foo)" is
@@ -439,6 +465,8 @@ bool Parser::Parse(io::Tokenizer* input, FileDescriptorProto* file) {
         // identifier.
         return false;
       }
+      // Store the syntax into the file.
+      if (file != NULL) file->set_syntax(syntax_identifier_);
     } else if (!stop_after_syntax_identifier_) {
       syntax_identifier_ = "proto2";
     }
@@ -467,7 +495,9 @@ bool Parser::Parse(io::Tokenizer* input, FileDescriptorProto* file) {
 }
 
 bool Parser::ParseSyntaxIdentifier() {
-  DO(Consume("syntax", "File must begin with 'syntax = \"proto2\";'."));
+  DO(Consume(
+      "syntax",
+      "File must begin with a syntax statement, e.g. 'syntax = \"proto2\";'."));
   DO(Consume("="));
   io::Tokenizer::Token syntax_token = input_->current();
   string syntax;
@@ -476,10 +506,11 @@ bool Parser::ParseSyntaxIdentifier() {
 
   syntax_identifier_ = syntax;
 
-  if (syntax != "proto2" && !stop_after_syntax_identifier_) {
+  if (syntax != "proto2" && syntax != "proto3" &&
+      !stop_after_syntax_identifier_) {
     AddError(syntax_token.line, syntax_token.column,
       "Unrecognized syntax identifier \"" + syntax + "\".  This parser "
-      "only recognizes \"proto2\".");
+      "only recognizes \"proto2\" and \"proto3\".");
     return false;
   }
 
@@ -673,8 +704,9 @@ bool Parser::ParseMessageField(FieldDescriptorProto* field,
     LocationRecorder location(field_location,
                               FieldDescriptorProto::kLabelFieldNumber);
     FieldDescriptorProto::Label label;
-    DO(ParseLabel(&label, containing_file));
-    field->set_label(label);
+    if (ParseLabel(&label, containing_file)) {
+      field->set_label(label);
+    }
   }
 
   return ParseMessageFieldNoLabel(field, messages, parent_location,
@@ -690,20 +722,75 @@ bool Parser::ParseMessageFieldNoLabel(
     int location_field_number_for_nested_type,
     const LocationRecorder& field_location,
     const FileDescriptorProto* containing_file) {
+  MapField map_field;
   // Parse type.
   {
     LocationRecorder location(field_location);  // add path later
     location.RecordLegacyLocation(field, DescriptorPool::ErrorCollector::TYPE);
 
+    bool type_parsed = false;
     FieldDescriptorProto::Type type = FieldDescriptorProto::TYPE_INT32;
     string type_name;
-    DO(ParseType(&type, &type_name));
-    if (type_name.empty()) {
-      location.AddPath(FieldDescriptorProto::kTypeFieldNumber);
-      field->set_type(type);
-    } else {
+
+    // Special case map field. We only treat the field as a map field if the
+    // field type name starts with the word "map" with a following "<".
+    if (TryConsume("map")) {
+      if (LookingAt("<")) {
+        map_field.is_map_field = true;
+      } else {
+        // False positive
+        type_parsed = true;
+        type_name = "map";
+      }
+    }
+    if (map_field.is_map_field) {
+      if (field->has_oneof_index()) {
+        AddError("Map fields are not allowed in oneofs.");
+        return false;
+      }
+      if (field->has_label()) {
+        AddError(
+            "Field labels (required/optional/repeated) are not allowed on "
+            "map fields.");
+        return false;
+      }
+      if (field->has_extendee()) {
+        AddError("Map fields are not allowed to be extensions.");
+        return false;
+      }
+      field->set_label(FieldDescriptorProto::LABEL_REPEATED);
+      DO(Consume("<"));
+      DO(ParseType(&map_field.key_type, &map_field.key_type_name));
+      DO(Consume(","));
+      DO(ParseType(&map_field.value_type, &map_field.value_type_name));
+      DO(Consume(">"));
+      // Defer setting of the type name of the map field until the
+      // field name is parsed. Add the source location though.
       location.AddPath(FieldDescriptorProto::kTypeNameFieldNumber);
-      field->set_type_name(type_name);
+    } else {
+      // Handle the case where no explicit label is given for a non-map field.
+      if (!field->has_label() && DefaultToOptionalFields()) {
+        field->set_label(FieldDescriptorProto::LABEL_OPTIONAL);
+      }
+      if (!field->has_label()) {
+        AddError("Expected \"required\", \"optional\", or \"repeated\".");
+        // We can actually reasonably recover here by just assuming the user
+        // forgot the label altogether.
+        field->set_label(FieldDescriptorProto::LABEL_OPTIONAL);
+      }
+
+      // Handle the case where the actual type is a message or enum named "map",
+      // which we already consumed in the code above.
+      if (!type_parsed) {
+        DO(ParseType(&type, &type_name));
+      }
+      if (type_name.empty()) {
+        location.AddPath(FieldDescriptorProto::kTypeFieldNumber);
+        field->set_type(type);
+      } else {
+        location.AddPath(FieldDescriptorProto::kTypeNameFieldNumber);
+        field->set_type_name(type_name);
+      }
     }
   }
 
@@ -781,9 +868,42 @@ bool Parser::ParseMessageFieldNoLabel(
     DO(ConsumeEndOfDeclaration(";", &field_location));
   }
 
+  // Create a map entry type if this is a map field.
+  if (map_field.is_map_field) {
+    GenerateMapEntry(map_field, field, messages);
+  }
+
   return true;
 }
 
+void Parser::GenerateMapEntry(const MapField& map_field,
+                              FieldDescriptorProto* field,
+                              RepeatedPtrField<DescriptorProto>* messages) {
+  DescriptorProto* entry = messages->Add();
+  string entry_name = MapEntryName(field->name());
+  field->set_type_name(entry_name);
+  entry->set_name(entry_name);
+  entry->mutable_options()->set_map_entry(true);
+  FieldDescriptorProto* key_field = entry->add_field();
+  key_field->set_name("key");
+  key_field->set_label(FieldDescriptorProto::LABEL_OPTIONAL);
+  key_field->set_number(1);
+  if (map_field.key_type_name.empty()) {
+    key_field->set_type(map_field.key_type);
+  } else {
+    key_field->set_type_name(map_field.key_type_name);
+  }
+  FieldDescriptorProto* value_field = entry->add_field();
+  value_field->set_name("value");
+  value_field->set_label(FieldDescriptorProto::LABEL_OPTIONAL);
+  value_field->set_number(2);
+  if (map_field.value_type_name.empty()) {
+    value_field->set_type(map_field.value_type);
+  } else {
+    value_field->set_type_name(map_field.value_type_name);
+  }
+}
+
 bool Parser::ParseFieldOptions(FieldDescriptorProto* field,
                                const LocationRecorder& field_location,
                                const FileDescriptorProto* containing_file) {
@@ -1588,13 +1708,8 @@ bool Parser::ParseLabel(FieldDescriptorProto::Label* label,
   } else if (TryConsume("required")) {
     *label = FieldDescriptorProto::LABEL_REQUIRED;
     return true;
-  } else {
-    AddError("Expected \"required\", \"optional\", or \"repeated\".");
-    // We can actually reasonably recover here by just assuming the user
-    // forgot the label altogether.
-    *label = FieldDescriptorProto::LABEL_OPTIONAL;
-    return true;
   }
+  return false;
 }
 
 bool Parser::ParseType(FieldDescriptorProto::Type* type,
diff --git a/src/google/protobuf/compiler/parser.h b/src/google/protobuf/compiler/parser.h
index d0a2359b..a15cc705 100644
--- a/src/google/protobuf/compiler/parser.h
+++ b/src/google/protobuf/compiler/parser.h
@@ -403,7 +403,7 @@ class LIBPROTOBUF_EXPORT Parser {
                     Message* mutable_options);
 
   // Parse "required", "optional", or "repeated" and fill in "label"
-  // with the value.
+  // with the value. Returns true if shuch a label is consumed.
   bool ParseLabel(FieldDescriptorProto::Label* label,
                   const FileDescriptorProto* containing_file);
 
@@ -460,6 +460,28 @@ class LIBPROTOBUF_EXPORT Parser {
   // the ending brace.
   bool ParseUninterpretedBlock(string* value);
 
+  struct MapField {
+    // Whether the field is a map field.
+    bool is_map_field;
+    // The types of the key and value if they are primitive types.
+    FieldDescriptorProto::Type key_type;
+    FieldDescriptorProto::Type value_type;
+    // Or the type names string if the types are customized types.
+    string key_type_name;
+    string value_type_name;
+
+    MapField() : is_map_field(false) {}
+  };
+  // Desugar the map syntax to generate a nested map entry message.
+  void GenerateMapEntry(const MapField& map_field, FieldDescriptorProto* field,
+                        RepeatedPtrField<DescriptorProto>* messages);
+
+  // Whether fields without label default to optional fields.
+  bool DefaultToOptionalFields() const {
+    return syntax_identifier_ == "proto3";
+  }
+
+
   // =================================================================
 
   io::Tokenizer* input_;
diff --git a/src/google/protobuf/compiler/parser_unittest.cc b/src/google/protobuf/compiler/parser_unittest.cc
index 9ec29a48..c2206ade 100644
--- a/src/google/protobuf/compiler/parser_unittest.cc
+++ b/src/google/protobuf/compiler/parser_unittest.cc
@@ -33,6 +33,9 @@
 //  Sanjay Ghemawat, Jeff Dean, and others.
 
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <vector>
 #include <algorithm>
 #include <map>
@@ -250,6 +253,7 @@ TEST_F(ParseMessageTest, ExplicitSyntaxIdentifier) {
     "  required int32 foo = 1;\n"
     "}\n",
 
+    "syntax: 'proto2' "
     "message_type {"
     "  name: \"TestMessage\""
     "  field { name:\"foo\" label:LABEL_REQUIRED type:TYPE_INT32 number:1 }"
@@ -265,6 +269,7 @@ TEST_F(ParseMessageTest, ExplicitRequiredSyntaxIdentifier) {
     "  required int32 foo = 1;\n"
     "}\n",
 
+    "syntax: 'proto2' "
     "message_type {"
     "  name: \"TestMessage\""
     "  field { name:\"foo\" label:LABEL_REQUIRED type:TYPE_INT32 number:1 }"
@@ -500,6 +505,54 @@ TEST_F(ParseMessageTest, MultipleOneofs) {
     "}");
 }
 
+TEST_F(ParseMessageTest, Maps) {
+  ExpectParsesTo(
+    "message TestMessage {\n"
+    "  map<int32, string> primitive_type_map = 1;\n"
+    "  map<KeyType, ValueType> composite_type_map = 2;\n"
+    "}\n",
+
+    "message_type {"
+    "  name: \"TestMessage\""
+    "  nested_type {"
+    "    name: \"PrimitiveTypeMapEntry\""
+    "    field { "
+    "       name: \"key\" number: 1 label:LABEL_OPTIONAL"
+    "       type:TYPE_INT32"
+    "    }"
+    "    field { "
+    "       name: \"value\" number: 2 label:LABEL_OPTIONAL"
+    "       type:TYPE_STRING"
+    "    }"
+    "    options { map_entry: true }"
+    "  }"
+    "  nested_type {"
+    "    name: \"CompositeTypeMapEntry\""
+    "    field { "
+    "       name: \"key\" number: 1 label:LABEL_OPTIONAL"
+    "       type_name: \"KeyType\""
+    "    }"
+    "    field { "
+    "       name: \"value\" number: 2 label:LABEL_OPTIONAL"
+    "       type_name: \"ValueType\""
+    "    }"
+    "    options { map_entry: true }"
+    "  }"
+    "  field {"
+    "    name: \"primitive_type_map\""
+    "    label: LABEL_REPEATED"
+    "    type_name: \"PrimitiveTypeMapEntry\""
+    "    number: 1"
+    "  }"
+    "  field {"
+    "    name: \"composite_type_map\""
+    "    label: LABEL_REPEATED"
+    "    type_name: \"CompositeTypeMapEntry\""
+    "    number: 2"
+    "  }"
+    "}");
+}
+
 TEST_F(ParseMessageTest, Group) {
   ExpectParsesTo(
     "message TestMessage {\n"
@@ -639,6 +692,20 @@ TEST_F(ParseMessageTest, MultipleExtensionsOneExtendee) {
     "            type_name:\"TestMessage\" extendee: \"Extendee1\" }");
 }
 
+TEST_F(ParseMessageTest, OptionalOptionalLabelProto3) {
+  ExpectParsesTo(
+    "syntax = \"proto3\";\n"
+    "message TestMessage {\n"
+    "  int32 foo = 1;\n"
+    "  optional int32 bar = 2;\n"
+    "}\n",
+
+    "syntax: \"proto3\" "
+    "message_type {"
+    "  name: \"TestMessage\""
+    "  field { name:\"foo\" label:LABEL_OPTIONAL type:TYPE_INT32 number:1 }"
+    "  field { name:\"bar\" label:LABEL_OPTIONAL type:TYPE_INT32 number:2 } }");
+}
 
 // ===================================================================
 
@@ -828,9 +895,9 @@ typedef ParserTest ParseErrorTest;
 
 TEST_F(ParseErrorTest, MissingSyntaxIdentifier) {
   require_syntax_identifier_ = true;
-  ExpectHasEarlyExitErrors(
-    "message TestMessage {}",
-    "0:0: File must begin with 'syntax = \"proto2\";'.\n");
+  ExpectHasEarlyExitErrors("message TestMessage {}",
+                           "0:0: File must begin with a syntax statement, e.g. "
+                           "'syntax = \"proto2\";'.\n");
   EXPECT_EQ("", parser_->GetSyntaxIdentifier());
 }
 
@@ -838,7 +905,7 @@ TEST_F(ParseErrorTest, UnknownSyntaxIdentifier) {
   ExpectHasEarlyExitErrors(
     "syntax = \"no_such_syntax\";",
     "0:9: Unrecognized syntax identifier \"no_such_syntax\".  This parser "
-      "only recognizes \"proto2\".\n");
+      "only recognizes \"proto2\" and \"proto3\".\n");
   EXPECT_EQ("no_such_syntax", parser_->GetSyntaxIdentifier());
 }
 
@@ -1041,6 +1108,55 @@ TEST_F(ParseErrorTest, LabelInOneof) {
       "/ repeated).\n");
 }
 
+TEST_F(ParseErrorTest, MapInOneof) {
+  ExpectHasErrors(
+    "message TestMessage {\n"
+    "  oneof foo {\n"
+    "    map<int32, int32> foo_map = 1;\n"
+    "    map message_field = 2;\n"  // a normal message field is OK
+    "  }\n"
+    "}\n",
+    "2:7: Map fields are not allowed in oneofs.\n");
+}
+
+TEST_F(ParseErrorTest, LabelForMap) {
+  ExpectHasErrors(
+    "message TestMessage {\n"
+    "  optional map<int32, int32> int_map = 1;\n"
+    "  required map<int32, int32> int_map2 = 2;\n"
+    "  repeated map<int32, int32> int_map3 = 3;\n"
+    "  optional map map_message = 4;\n"  // a normal message field is OK
+    "}\n",
+    "1:14: Field labels (required/optional/repeated) are not allowed on map "
+    "fields.\n"
+    "2:14: Field labels (required/optional/repeated) are not allowed on map "
+    "fields.\n"
+    "3:14: Field labels (required/optional/repeated) are not allowed on map "
+    "fields.\n");
+}
+
+TEST_F(ParseErrorTest, MalformedMaps) {
+  ExpectHasErrors(
+    "message TestMessage {\n"
+    "  map map_message = 1;\n"   // a normal message field lacking label
+    "  map<string> str_map = 2;\n"
+    "  map<string,> str_map2 = 3;\n"
+    "  map<,string> str_map3 = 4;\n"
+    "  map<> empty_map = 5;\n"
+    "  map<string,string str_map6 = 6;\n"
+    "}"
+    "extend SomeMessage {\n"
+    "  map<int32, int32> int_map = 1;\n"
+    "}",
+    "1:6: Expected \"required\", \"optional\", or \"repeated\".\n"
+    "2:12: Expected \",\".\n"
+    "3:13: Expected type name.\n"
+    "4:6: Expected type name.\n"
+    "5:6: Expected type name.\n"
+    "6:20: Expected \">\".\n"
+    "8:5: Map fields are not allowed to be extensions.\n");
+}
+
 TEST_F(ParseErrorTest, GroupNotCapitalized) {
   ExpectHasErrors(
     "message TestMessage {\n"
@@ -1413,7 +1529,7 @@ TEST_F(ParserValidationErrorTest, ResovledUndefinedOptionError) {
 // definitions again afoter parsing (note, however, that the order of messages
 // cannot be guaranteed to be the same)
 
-typedef ParserTest ParseDecriptorDebugTest;
+typedef ParserTest ParseDescriptorDebugTest;
 
 class CompareDescriptorNames {
  public:
@@ -1447,7 +1563,28 @@ void SortMessages(FileDescriptorProto *file_descriptor_proto) {
   sort(data, data + size, CompareDescriptorNames());
 }
 
-TEST_F(ParseDecriptorDebugTest, TestAllDescriptorTypes) {
+// Strips the message and enum field type names for comparison purpose only.
+void StripFieldTypeName(DescriptorProto* proto) {
+  for (int i = 0; i < proto->field_size(); ++i) {
+    string type_name = proto->field(i).type_name();
+    string::size_type pos = type_name.find_last_of(".");
+    if (pos != string::npos) {
+      proto->mutable_field(i)->mutable_type_name()->assign(
+          type_name.begin() + pos + 1, type_name.end());
+    }
+  }
+  for (int i = 0; i < proto->nested_type_size(); ++i) {
+    StripFieldTypeName(proto->mutable_nested_type(i));
+  }
+}
+
+void StripFieldTypeName(FileDescriptorProto* file_proto) {
+  for (int i = 0; i < file_proto->message_type_size(); ++i) {
+    StripFieldTypeName(file_proto->mutable_message_type(i));
+  }
+}
+
+TEST_F(ParseDescriptorDebugTest, TestAllDescriptorTypes) {
   const FileDescriptor* original_file =
      protobuf_unittest::TestAllTypes::descriptor()->file();
   FileDescriptorProto expected;
@@ -1499,7 +1636,7 @@ TEST_F(ParseDecriptorDebugTest, TestAllDescriptorTypes) {
   EXPECT_EQ(expected.DebugString(), parsed.DebugString());
 }
 
-TEST_F(ParseDecriptorDebugTest, TestCustomOptions) {
+TEST_F(ParseDescriptorDebugTest, TestCustomOptions) {
   const FileDescriptor* original_file =
      protobuf_unittest::AggregateMessage::descriptor()->file();
   FileDescriptorProto expected;
@@ -1538,6 +1675,106 @@ TEST_F(ParseDecriptorDebugTest, TestCustomOptions) {
   EXPECT_EQ(expected.DebugString(), parsed.DebugString());
 }
 
+// Ensure that DebugStringWithOptions(), with |include_comments| set to true,
+// includes comments from the original parser input in all of the appropriate
+// places.
+TEST_F(ParseDescriptorDebugTest, TestCommentsInDebugString) {
+  SetupParser(
+      "// Message comment.\n"
+      "message TestMessage1 {\n"
+      "  // Field comment.\n"
+      "  optional int32 foo = 1;\n"
+      "\n"
+      "  // Nested-message comment.\n"
+      "  message NestedMessage {\n"
+      "    optional int32 bar = 1;\n"
+      "  }\n"
+      "}\n"
+      "\n"
+      "// Enum comment.\n"
+      "enum MyEnumType {\n"
+      "  // Enum-value comment.\n"
+      "  ASDF = 1;\n"
+      "}\n"
+      "\n"
+      "// Service comment.\n"
+      "service MyService {\n"
+      "  // RPC comment.\n"
+      "  rpc MyRPCCall(TestMessage1) returns (TestMessage1) { }\n"
+      "}\n");
+
+  FileDescriptorProto parsed_desc;
+  parsed_desc.set_name("foo.proto");
+  SourceLocationTable source_locations;
+  parser_->RecordSourceLocationsTo(&source_locations);
+  parser_->Parse(input_.get(), &parsed_desc);
+  EXPECT_EQ(io::Tokenizer::TYPE_END, input_->current().type);
+  ASSERT_EQ("", error_collector_.text_);
+
+  // We need to import the FileDescriptorProto to get a FileDescriptor.
+  MockValidationErrorCollector collector(source_locations, &error_collector_);
+  const FileDescriptor* descriptor =
+      pool_.BuildFileCollectingErrors(parsed_desc, &collector);
+  ASSERT_TRUE(descriptor != NULL);
+
+  DebugStringOptions debug_string_options;
+  debug_string_options.include_comments = true;
+  const string debug_string =
+      descriptor->DebugStringWithOptions(debug_string_options);
+
+  // Ensure that each of the comments appears somewhere in the DebugString(),
+  // and that these comments appear in order. We don't test the exact comment
+  // placement or formatting, because we do not want to be too fragile here.
+  const char* expected_comments[] = {
+    "Message comment.",
+    "Field comment",
+    "Nested-message comment",
+    "Enum comment",
+    "Enum-value comment",
+    "Service comment",
+    "RPC comment",
+  };
+
+  for (int i = 0; i < GOOGLE_ARRAYSIZE(expected_comments); ++i) {
+    string::size_type found_pos = debug_string.find(expected_comments[i]);
+    ASSERT_TRUE(found_pos != string::npos);
+  }
+}
+
+TEST_F(ParseDescriptorDebugTest, TestMaps) {
+  SetupParser(
+      "syntax = \"proto3\"; "
+      "message Foo { "
+      "  message Bar { } "
+      "  map<int32, Bar> enum_message_map = 1; "
+      "  map<string, float> primitive_map = 2; "
+      "} ");
+  FileDescriptorProto original;
+  EXPECT_TRUE(parser_->Parse(input_.get(), &original));
+  original.set_name("foo.proto");
+  const FileDescriptor* file = pool_.BuildFile(original);
+  ASSERT_TRUE(file != NULL);
+
+  // Make sure the debug string uses map syntax and does not have the auto
+  // generated entry.
+  string debug_string = file->DebugString();
+  EXPECT_TRUE(debug_string.find("map<") != string::npos);
+  EXPECT_TRUE(debug_string.find("option map_entry") == string::npos);
+  EXPECT_TRUE(debug_string.find("MapEntry") == string::npos);
+
+  // Make sure the descriptor debug string is parsable.
+  FileDescriptorProto parsed;
+  SetupParser(debug_string.c_str());
+  parsed.set_name("foo.proto");
+  ASSERT_TRUE(parser_->Parse(input_.get(), &parsed));
+
+  original.clear_source_code_info();
+  parsed.clear_source_code_info();
+  StripFieldTypeName(&original);
+  StripFieldTypeName(&parsed);
+  EXPECT_EQ(original.DebugString(), parsed.DebugString());
+}
+
 // ===================================================================
 // SourceCodeInfo tests.
 
diff --git a/src/google/protobuf/compiler/plugin.pb.cc b/src/google/protobuf/compiler/plugin.pb.cc
index b5cd01b5..efa64f3d 100644
--- a/src/google/protobuf/compiler/plugin.pb.cc
+++ b/src/google/protobuf/compiler/plugin.pb.cc
@@ -53,11 +53,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fcompiler_2fplugin_2eproto() {
       CodeGeneratorRequest::default_instance_,
       CodeGeneratorRequest_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(CodeGeneratorRequest, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(CodeGeneratorRequest, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(CodeGeneratorRequest));
+      sizeof(CodeGeneratorRequest),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(CodeGeneratorRequest, _internal_metadata_));
   CodeGeneratorResponse_descriptor_ = file->message_type(1);
   static const int CodeGeneratorResponse_offsets_[2] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(CodeGeneratorResponse, error_),
@@ -69,11 +70,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fcompiler_2fplugin_2eproto() {
       CodeGeneratorResponse::default_instance_,
       CodeGeneratorResponse_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(CodeGeneratorResponse, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(CodeGeneratorResponse, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(CodeGeneratorResponse));
+      sizeof(CodeGeneratorResponse),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(CodeGeneratorResponse, _internal_metadata_));
   CodeGeneratorResponse_File_descriptor_ = CodeGeneratorResponse_descriptor_->nested_type(0);
   static const int CodeGeneratorResponse_File_offsets_[3] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(CodeGeneratorResponse_File, name_),
@@ -86,11 +88,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fcompiler_2fplugin_2eproto() {
       CodeGeneratorResponse_File::default_instance_,
       CodeGeneratorResponse_File_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(CodeGeneratorResponse_File, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(CodeGeneratorResponse_File, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(CodeGeneratorResponse_File));
+      sizeof(CodeGeneratorResponse_File),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(CodeGeneratorResponse_File, _internal_metadata_));
 }
 
 namespace {
@@ -169,16 +172,27 @@ const int CodeGeneratorRequest::kProtoFileFieldNumber;
 #endif  // !_MSC_VER
 
 CodeGeneratorRequest::CodeGeneratorRequest()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.compiler.CodeGeneratorRequest)
 }
 
+CodeGeneratorRequest::CodeGeneratorRequest(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena),
+  file_to_generate_(arena),
+  proto_file_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.compiler.CodeGeneratorRequest)
+}
+
 void CodeGeneratorRequest::InitAsDefaultInstance() {
 }
 
 CodeGeneratorRequest::CodeGeneratorRequest(const CodeGeneratorRequest& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.compiler.CodeGeneratorRequest)
@@ -187,7 +201,7 @@ CodeGeneratorRequest::CodeGeneratorRequest(const CodeGeneratorRequest& from)
 void CodeGeneratorRequest::SharedCtor() {
   ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
-  parameter_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  parameter_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
 
@@ -197,13 +211,21 @@ CodeGeneratorRequest::~CodeGeneratorRequest() {
 }
 
 void CodeGeneratorRequest::SharedDtor() {
-  if (parameter_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete parameter_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
+  parameter_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   if (this != default_instance_) {
   }
 }
 
+void CodeGeneratorRequest::ArenaDtor(void* object) {
+  CodeGeneratorRequest* _this = reinterpret_cast< CodeGeneratorRequest* >(object);
+  (void)_this;
+}
+void CodeGeneratorRequest::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void CodeGeneratorRequest::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -221,20 +243,20 @@ const CodeGeneratorRequest& CodeGeneratorRequest::default_instance() {
 
 CodeGeneratorRequest* CodeGeneratorRequest::default_instance_ = NULL;
 
-CodeGeneratorRequest* CodeGeneratorRequest::New() const {
-  return new CodeGeneratorRequest;
+CodeGeneratorRequest* CodeGeneratorRequest::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<CodeGeneratorRequest>(arena);
 }
 
 void CodeGeneratorRequest::Clear() {
   if (has_parameter()) {
-    if (parameter_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-      parameter_->clear();
-    }
+    parameter_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   }
   file_to_generate_.Clear();
   proto_file_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool CodeGeneratorRequest::MergePartialFromCodedStream(
@@ -257,7 +279,7 @@ bool CodeGeneratorRequest::MergePartialFromCodedStream(
             this->file_to_generate(this->file_to_generate_size() - 1).data(),
             this->file_to_generate(this->file_to_generate_size() - 1).length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "file_to_generate");
+            "google.protobuf.compiler.CodeGeneratorRequest.file_to_generate");
         } else {
           goto handle_unusual;
         }
@@ -275,7 +297,7 @@ bool CodeGeneratorRequest::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->parameter().data(), this->parameter().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "parameter");
+            "google.protobuf.compiler.CodeGeneratorRequest.parameter");
         } else {
           goto handle_unusual;
         }
@@ -327,7 +349,7 @@ void CodeGeneratorRequest::SerializeWithCachedSizes(
   ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
     this->file_to_generate(i).data(), this->file_to_generate(i).length(),
     ::google::protobuf::internal::WireFormat::SERIALIZE,
-    "file_to_generate");
+    "google.protobuf.compiler.CodeGeneratorRequest.file_to_generate");
     ::google::protobuf::internal::WireFormatLite::WriteString(
       1, this->file_to_generate(i), output);
   }
@@ -337,7 +359,7 @@ void CodeGeneratorRequest::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->parameter().data(), this->parameter().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "parameter");
+      "google.protobuf.compiler.CodeGeneratorRequest.parameter");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       2, this->parameter(), output);
   }
@@ -348,7 +370,7 @@ void CodeGeneratorRequest::SerializeWithCachedSizes(
       15, this->proto_file(i), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -363,7 +385,7 @@ void CodeGeneratorRequest::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->file_to_generate(i).data(), this->file_to_generate(i).length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "file_to_generate");
+      "google.protobuf.compiler.CodeGeneratorRequest.file_to_generate");
     target = ::google::protobuf::internal::WireFormatLite::
       WriteStringToArray(1, this->file_to_generate(i), target);
   }
@@ -373,7 +395,7 @@ void CodeGeneratorRequest::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->parameter().data(), this->parameter().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "parameter");
+      "google.protobuf.compiler.CodeGeneratorRequest.parameter");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         2, this->parameter(), target);
@@ -386,7 +408,7 @@ void CodeGeneratorRequest::SerializeWithCachedSizes(
         15, this->proto_file(i), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -397,15 +419,13 @@ void CodeGeneratorRequest::SerializeWithCachedSizes(
 int CodeGeneratorRequest::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[1 / 32] & (0xffu << (1 % 32))) {
-    // optional string parameter = 2;
-    if (has_parameter()) {
-      total_size += 1 +
-        ::google::protobuf::internal::WireFormatLite::StringSize(
-          this->parameter());
-    }
-
+  // optional string parameter = 2;
+  if (has_parameter()) {
+    total_size += 1 +
+      ::google::protobuf::internal::WireFormatLite::StringSize(
+        this->parameter());
   }
+
   // repeated string file_to_generate = 1;
   total_size += 1 * this->file_to_generate_size();
   for (int i = 0; i < this->file_to_generate_size(); i++) {
@@ -421,7 +441,7 @@ int CodeGeneratorRequest::ByteSize() const {
         this->proto_file(i));
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -453,7 +473,9 @@ void CodeGeneratorRequest::MergeFrom(const CodeGeneratorRequest& from) {
       set_parameter(from.parameter());
     }
   }
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void CodeGeneratorRequest::CopyFrom(const ::google::protobuf::Message& from) {
@@ -475,15 +497,29 @@ bool CodeGeneratorRequest::IsInitialized() const {
 }
 
 void CodeGeneratorRequest::Swap(CodeGeneratorRequest* other) {
-  if (other != this) {
-    file_to_generate_.Swap(&other->file_to_generate_);
-    std::swap(parameter_, other->parameter_);
-    proto_file_.Swap(&other->proto_file_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    CodeGeneratorRequest temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void CodeGeneratorRequest::UnsafeArenaSwap(CodeGeneratorRequest* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void CodeGeneratorRequest::InternalSwap(CodeGeneratorRequest* other) {
+  file_to_generate_.UnsafeArenaSwap(&other->file_to_generate_);
+  parameter_.Swap(&other->parameter_);
+  proto_file_.UnsafeArenaSwap(&other->proto_file_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+}
 
 ::google::protobuf::Metadata CodeGeneratorRequest::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -503,16 +539,25 @@ const int CodeGeneratorResponse_File::kContentFieldNumber;
 #endif  // !_MSC_VER
 
 CodeGeneratorResponse_File::CodeGeneratorResponse_File()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.compiler.CodeGeneratorResponse.File)
 }
 
+CodeGeneratorResponse_File::CodeGeneratorResponse_File(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.compiler.CodeGeneratorResponse.File)
+}
+
 void CodeGeneratorResponse_File::InitAsDefaultInstance() {
 }
 
 CodeGeneratorResponse_File::CodeGeneratorResponse_File(const CodeGeneratorResponse_File& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.compiler.CodeGeneratorResponse.File)
@@ -521,9 +566,9 @@ CodeGeneratorResponse_File::CodeGeneratorResponse_File(const CodeGeneratorRespon
 void CodeGeneratorResponse_File::SharedCtor() {
   ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-  insertion_point_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-  content_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  name_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  insertion_point_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  content_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
 
@@ -533,19 +578,23 @@ CodeGeneratorResponse_File::~CodeGeneratorResponse_File() {
 }
 
 void CodeGeneratorResponse_File::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
-  }
-  if (insertion_point_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete insertion_point_;
-  }
-  if (content_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete content_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
+  name_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+  insertion_point_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+  content_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   if (this != default_instance_) {
   }
 }
 
+void CodeGeneratorResponse_File::ArenaDtor(void* object) {
+  CodeGeneratorResponse_File* _this = reinterpret_cast< CodeGeneratorResponse_File* >(object);
+  (void)_this;
+}
+void CodeGeneratorResponse_File::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void CodeGeneratorResponse_File::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -563,30 +612,26 @@ const CodeGeneratorResponse_File& CodeGeneratorResponse_File::default_instance()
 
 CodeGeneratorResponse_File* CodeGeneratorResponse_File::default_instance_ = NULL;
 
-CodeGeneratorResponse_File* CodeGeneratorResponse_File::New() const {
-  return new CodeGeneratorResponse_File;
+CodeGeneratorResponse_File* CodeGeneratorResponse_File::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<CodeGeneratorResponse_File>(arena);
 }
 
 void CodeGeneratorResponse_File::Clear() {
   if (_has_bits_[0 / 32] & 7) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        name_->clear();
-      }
+      name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     if (has_insertion_point()) {
-      if (insertion_point_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        insertion_point_->clear();
-      }
+      insertion_point_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     if (has_content()) {
-      if (content_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        content_->clear();
-      }
+      content_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
   }
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool CodeGeneratorResponse_File::MergePartialFromCodedStream(
@@ -607,7 +652,7 @@ bool CodeGeneratorResponse_File::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->name().data(), this->name().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "name");
+            "google.protobuf.compiler.CodeGeneratorResponse.File.name");
         } else {
           goto handle_unusual;
         }
@@ -624,7 +669,7 @@ bool CodeGeneratorResponse_File::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->insertion_point().data(), this->insertion_point().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "insertion_point");
+            "google.protobuf.compiler.CodeGeneratorResponse.File.insertion_point");
         } else {
           goto handle_unusual;
         }
@@ -641,7 +686,7 @@ bool CodeGeneratorResponse_File::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->content().data(), this->content().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "content");
+            "google.protobuf.compiler.CodeGeneratorResponse.File.content");
         } else {
           goto handle_unusual;
         }
@@ -679,7 +724,7 @@ void CodeGeneratorResponse_File::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.compiler.CodeGeneratorResponse.File.name");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       1, this->name(), output);
   }
@@ -689,7 +734,7 @@ void CodeGeneratorResponse_File::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->insertion_point().data(), this->insertion_point().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "insertion_point");
+      "google.protobuf.compiler.CodeGeneratorResponse.File.insertion_point");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       2, this->insertion_point(), output);
   }
@@ -699,12 +744,12 @@ void CodeGeneratorResponse_File::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->content().data(), this->content().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "content");
+      "google.protobuf.compiler.CodeGeneratorResponse.File.content");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       15, this->content(), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -719,7 +764,7 @@ void CodeGeneratorResponse_File::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.compiler.CodeGeneratorResponse.File.name");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         1, this->name(), target);
@@ -730,7 +775,7 @@ void CodeGeneratorResponse_File::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->insertion_point().data(), this->insertion_point().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "insertion_point");
+      "google.protobuf.compiler.CodeGeneratorResponse.File.insertion_point");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         2, this->insertion_point(), target);
@@ -741,13 +786,13 @@ void CodeGeneratorResponse_File::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->content().data(), this->content().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "content");
+      "google.protobuf.compiler.CodeGeneratorResponse.File.content");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         15, this->content(), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -758,7 +803,7 @@ void CodeGeneratorResponse_File::SerializeWithCachedSizes(
 int CodeGeneratorResponse_File::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
+  if (_has_bits_[0 / 32] & 7) {
     // optional string name = 1;
     if (has_name()) {
       total_size += 1 +
@@ -781,7 +826,7 @@ int CodeGeneratorResponse_File::ByteSize() const {
     }
 
   }
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -817,7 +862,9 @@ void CodeGeneratorResponse_File::MergeFrom(const CodeGeneratorResponse_File& fro
       set_content(from.content());
     }
   }
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void CodeGeneratorResponse_File::CopyFrom(const ::google::protobuf::Message& from) {
@@ -838,15 +885,29 @@ bool CodeGeneratorResponse_File::IsInitialized() const {
 }
 
 void CodeGeneratorResponse_File::Swap(CodeGeneratorResponse_File* other) {
-  if (other != this) {
-    std::swap(name_, other->name_);
-    std::swap(insertion_point_, other->insertion_point_);
-    std::swap(content_, other->content_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    CodeGeneratorResponse_File temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void CodeGeneratorResponse_File::UnsafeArenaSwap(CodeGeneratorResponse_File* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void CodeGeneratorResponse_File::InternalSwap(CodeGeneratorResponse_File* other) {
+  name_.Swap(&other->name_);
+  insertion_point_.Swap(&other->insertion_point_);
+  content_.Swap(&other->content_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+}
 
 ::google::protobuf::Metadata CodeGeneratorResponse_File::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -865,16 +926,26 @@ const int CodeGeneratorResponse::kFileFieldNumber;
 #endif  // !_MSC_VER
 
 CodeGeneratorResponse::CodeGeneratorResponse()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.compiler.CodeGeneratorResponse)
 }
 
+CodeGeneratorResponse::CodeGeneratorResponse(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena),
+  file_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.compiler.CodeGeneratorResponse)
+}
+
 void CodeGeneratorResponse::InitAsDefaultInstance() {
 }
 
 CodeGeneratorResponse::CodeGeneratorResponse(const CodeGeneratorResponse& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.compiler.CodeGeneratorResponse)
@@ -883,7 +954,7 @@ CodeGeneratorResponse::CodeGeneratorResponse(const CodeGeneratorResponse& from)
 void CodeGeneratorResponse::SharedCtor() {
   ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
-  error_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  error_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
 
@@ -893,13 +964,21 @@ CodeGeneratorResponse::~CodeGeneratorResponse() {
 }
 
 void CodeGeneratorResponse::SharedDtor() {
-  if (error_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete error_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
+  error_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   if (this != default_instance_) {
   }
 }
 
+void CodeGeneratorResponse::ArenaDtor(void* object) {
+  CodeGeneratorResponse* _this = reinterpret_cast< CodeGeneratorResponse* >(object);
+  (void)_this;
+}
+void CodeGeneratorResponse::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void CodeGeneratorResponse::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -917,19 +996,19 @@ const CodeGeneratorResponse& CodeGeneratorResponse::default_instance() {
 
 CodeGeneratorResponse* CodeGeneratorResponse::default_instance_ = NULL;
 
-CodeGeneratorResponse* CodeGeneratorResponse::New() const {
-  return new CodeGeneratorResponse;
+CodeGeneratorResponse* CodeGeneratorResponse::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<CodeGeneratorResponse>(arena);
 }
 
 void CodeGeneratorResponse::Clear() {
   if (has_error()) {
-    if (error_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-      error_->clear();
-    }
+    error_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   }
   file_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool CodeGeneratorResponse::MergePartialFromCodedStream(
@@ -950,7 +1029,7 @@ bool CodeGeneratorResponse::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->error().data(), this->error().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "error");
+            "google.protobuf.compiler.CodeGeneratorResponse.error");
         } else {
           goto handle_unusual;
         }
@@ -1002,7 +1081,7 @@ void CodeGeneratorResponse::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->error().data(), this->error().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "error");
+      "google.protobuf.compiler.CodeGeneratorResponse.error");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       1, this->error(), output);
   }
@@ -1013,7 +1092,7 @@ void CodeGeneratorResponse::SerializeWithCachedSizes(
       15, this->file(i), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -1028,7 +1107,7 @@ void CodeGeneratorResponse::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->error().data(), this->error().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "error");
+      "google.protobuf.compiler.CodeGeneratorResponse.error");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         1, this->error(), target);
@@ -1041,7 +1120,7 @@ void CodeGeneratorResponse::SerializeWithCachedSizes(
         15, this->file(i), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -1052,15 +1131,13 @@ void CodeGeneratorResponse::SerializeWithCachedSizes(
 int CodeGeneratorResponse::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
-    // optional string error = 1;
-    if (has_error()) {
-      total_size += 1 +
-        ::google::protobuf::internal::WireFormatLite::StringSize(
-          this->error());
-    }
-
+  // optional string error = 1;
+  if (has_error()) {
+    total_size += 1 +
+      ::google::protobuf::internal::WireFormatLite::StringSize(
+        this->error());
   }
+
   // repeated .google.protobuf.compiler.CodeGeneratorResponse.File file = 15;
   total_size += 1 * this->file_size();
   for (int i = 0; i < this->file_size(); i++) {
@@ -1069,7 +1146,7 @@ int CodeGeneratorResponse::ByteSize() const {
         this->file(i));
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -1100,7 +1177,9 @@ void CodeGeneratorResponse::MergeFrom(const CodeGeneratorResponse& from) {
       set_error(from.error());
     }
   }
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void CodeGeneratorResponse::CopyFrom(const ::google::protobuf::Message& from) {
@@ -1121,14 +1200,28 @@ bool CodeGeneratorResponse::IsInitialized() const {
 }
 
 void CodeGeneratorResponse::Swap(CodeGeneratorResponse* other) {
-  if (other != this) {
-    std::swap(error_, other->error_);
-    file_.Swap(&other->file_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    CodeGeneratorResponse temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void CodeGeneratorResponse::UnsafeArenaSwap(CodeGeneratorResponse* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void CodeGeneratorResponse::InternalSwap(CodeGeneratorResponse* other) {
+  error_.Swap(&other->error_);
+  file_.UnsafeArenaSwap(&other->file_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+}
 
 ::google::protobuf::Metadata CodeGeneratorResponse::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
diff --git a/src/google/protobuf/compiler/plugin.pb.h b/src/google/protobuf/compiler/plugin.pb.h
index 567b30ef..636992a6 100644
--- a/src/google/protobuf/compiler/plugin.pb.h
+++ b/src/google/protobuf/compiler/plugin.pb.h
@@ -5,6 +5,7 @@
 #define PROTOBUF_google_2fprotobuf_2fcompiler_2fplugin_2eproto__INCLUDED
 
 #include <string>
+#include <stdint.h>
 
 #include <google/protobuf/stubs/common.h>
 
@@ -19,7 +20,10 @@
 #error regenerate this file with a newer version of protoc.
 #endif
 
+#include <google/protobuf/arena.h>
+#include <google/protobuf/arenastring.h>
 #include <google/protobuf/generated_message_util.h>
+#include <google/protobuf/metadata.h>
 #include <google/protobuf/message.h>
 #include <google/protobuf/repeated_field.h>
 #include <google/protobuf/extension_set.h>
@@ -55,21 +59,28 @@ class LIBPROTOC_EXPORT CodeGeneratorRequest : public ::google::protobuf::Message
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const CodeGeneratorRequest& default_instance();
 
+  void UnsafeArenaSwap(CodeGeneratorRequest* other);
   void Swap(CodeGeneratorRequest* other);
 
   // implements Message ----------------------------------------------
 
-  CodeGeneratorRequest* New() const;
+  inline CodeGeneratorRequest* New() const { return New(NULL); }
+
+  CodeGeneratorRequest* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const CodeGeneratorRequest& from);
@@ -88,7 +99,21 @@ class LIBPROTOC_EXPORT CodeGeneratorRequest : public ::google::protobuf::Message
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(CodeGeneratorRequest* other);
+  protected:
+  explicit CodeGeneratorRequest(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -122,6 +147,9 @@ class LIBPROTOC_EXPORT CodeGeneratorRequest : public ::google::protobuf::Message
   inline ::std::string* mutable_parameter();
   inline ::std::string* release_parameter();
   inline void set_allocated_parameter(::std::string* parameter);
+  inline ::std::string* unsafe_arena_release_parameter();
+  inline void unsafe_arena_set_allocated_parameter(
+      ::std::string* parameter);
 
   // repeated .google.protobuf.FileDescriptorProto proto_file = 15;
   inline int proto_file_size() const;
@@ -140,12 +168,14 @@ class LIBPROTOC_EXPORT CodeGeneratorRequest : public ::google::protobuf::Message
   inline void set_has_parameter();
   inline void clear_has_parameter();
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
   ::google::protobuf::RepeatedPtrField< ::std::string> file_to_generate_;
-  ::std::string* parameter_;
+  ::google::protobuf::internal::ArenaStringPtr parameter_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::FileDescriptorProto > proto_file_;
   friend void LIBPROTOC_EXPORT protobuf_AddDesc_google_2fprotobuf_2fcompiler_2fplugin_2eproto();
   friend void protobuf_AssignDesc_google_2fprotobuf_2fcompiler_2fplugin_2eproto();
@@ -169,21 +199,28 @@ class LIBPROTOC_EXPORT CodeGeneratorResponse_File : public ::google::protobuf::M
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const CodeGeneratorResponse_File& default_instance();
 
+  void UnsafeArenaSwap(CodeGeneratorResponse_File* other);
   void Swap(CodeGeneratorResponse_File* other);
 
   // implements Message ----------------------------------------------
 
-  CodeGeneratorResponse_File* New() const;
+  inline CodeGeneratorResponse_File* New() const { return New(NULL); }
+
+  CodeGeneratorResponse_File* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const CodeGeneratorResponse_File& from);
@@ -202,7 +239,21 @@ class LIBPROTOC_EXPORT CodeGeneratorResponse_File : public ::google::protobuf::M
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(CodeGeneratorResponse_File* other);
+  protected:
+  explicit CodeGeneratorResponse_File(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -220,6 +271,9 @@ class LIBPROTOC_EXPORT CodeGeneratorResponse_File : public ::google::protobuf::M
   inline ::std::string* mutable_name();
   inline ::std::string* release_name();
   inline void set_allocated_name(::std::string* name);
+  inline ::std::string* unsafe_arena_release_name();
+  inline void unsafe_arena_set_allocated_name(
+      ::std::string* name);
 
   // optional string insertion_point = 2;
   inline bool has_insertion_point() const;
@@ -232,6 +286,9 @@ class LIBPROTOC_EXPORT CodeGeneratorResponse_File : public ::google::protobuf::M
   inline ::std::string* mutable_insertion_point();
   inline ::std::string* release_insertion_point();
   inline void set_allocated_insertion_point(::std::string* insertion_point);
+  inline ::std::string* unsafe_arena_release_insertion_point();
+  inline void unsafe_arena_set_allocated_insertion_point(
+      ::std::string* insertion_point);
 
   // optional string content = 15;
   inline bool has_content() const;
@@ -244,6 +301,9 @@ class LIBPROTOC_EXPORT CodeGeneratorResponse_File : public ::google::protobuf::M
   inline ::std::string* mutable_content();
   inline ::std::string* release_content();
   inline void set_allocated_content(::std::string* content);
+  inline ::std::string* unsafe_arena_release_content();
+  inline void unsafe_arena_set_allocated_content(
+      ::std::string* content);
 
   // @@protoc_insertion_point(class_scope:google.protobuf.compiler.CodeGeneratorResponse.File)
  private:
@@ -254,13 +314,15 @@ class LIBPROTOC_EXPORT CodeGeneratorResponse_File : public ::google::protobuf::M
   inline void set_has_content();
   inline void clear_has_content();
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
-  ::std::string* name_;
-  ::std::string* insertion_point_;
-  ::std::string* content_;
+  ::google::protobuf::internal::ArenaStringPtr name_;
+  ::google::protobuf::internal::ArenaStringPtr insertion_point_;
+  ::google::protobuf::internal::ArenaStringPtr content_;
   friend void LIBPROTOC_EXPORT protobuf_AddDesc_google_2fprotobuf_2fcompiler_2fplugin_2eproto();
   friend void protobuf_AssignDesc_google_2fprotobuf_2fcompiler_2fplugin_2eproto();
   friend void protobuf_ShutdownFile_google_2fprotobuf_2fcompiler_2fplugin_2eproto();
@@ -283,21 +345,28 @@ class LIBPROTOC_EXPORT CodeGeneratorResponse : public ::google::protobuf::Messag
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const CodeGeneratorResponse& default_instance();
 
+  void UnsafeArenaSwap(CodeGeneratorResponse* other);
   void Swap(CodeGeneratorResponse* other);
 
   // implements Message ----------------------------------------------
 
-  CodeGeneratorResponse* New() const;
+  inline CodeGeneratorResponse* New() const { return New(NULL); }
+
+  CodeGeneratorResponse* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const CodeGeneratorResponse& from);
@@ -316,7 +385,21 @@ class LIBPROTOC_EXPORT CodeGeneratorResponse : public ::google::protobuf::Messag
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(CodeGeneratorResponse* other);
+  protected:
+  explicit CodeGeneratorResponse(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -336,6 +419,9 @@ class LIBPROTOC_EXPORT CodeGeneratorResponse : public ::google::protobuf::Messag
   inline ::std::string* mutable_error();
   inline ::std::string* release_error();
   inline void set_allocated_error(::std::string* error);
+  inline ::std::string* unsafe_arena_release_error();
+  inline void unsafe_arena_set_allocated_error(
+      ::std::string* error);
 
   // repeated .google.protobuf.compiler.CodeGeneratorResponse.File file = 15;
   inline int file_size() const;
@@ -354,11 +440,13 @@ class LIBPROTOC_EXPORT CodeGeneratorResponse : public ::google::protobuf::Messag
   inline void set_has_error();
   inline void clear_has_error();
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
-  ::std::string* error_;
+  ::google::protobuf::internal::ArenaStringPtr error_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::compiler::CodeGeneratorResponse_File > file_;
   friend void LIBPROTOC_EXPORT protobuf_AddDesc_google_2fprotobuf_2fcompiler_2fplugin_2eproto();
   friend void protobuf_AssignDesc_google_2fprotobuf_2fcompiler_2fplugin_2eproto();
@@ -439,68 +527,67 @@ inline void CodeGeneratorRequest::clear_has_parameter() {
   _has_bits_[0] &= ~0x00000002u;
 }
 inline void CodeGeneratorRequest::clear_parameter() {
-  if (parameter_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    parameter_->clear();
-  }
+  parameter_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_parameter();
 }
 inline const ::std::string& CodeGeneratorRequest::parameter() const {
   // @@protoc_insertion_point(field_get:google.protobuf.compiler.CodeGeneratorRequest.parameter)
-  return *parameter_;
+  return parameter_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void CodeGeneratorRequest::set_parameter(const ::std::string& value) {
   set_has_parameter();
-  if (parameter_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    parameter_ = new ::std::string;
-  }
-  parameter_->assign(value);
+  parameter_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.compiler.CodeGeneratorRequest.parameter)
 }
 inline void CodeGeneratorRequest::set_parameter(const char* value) {
   set_has_parameter();
-  if (parameter_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    parameter_ = new ::std::string;
-  }
-  parameter_->assign(value);
+  parameter_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.compiler.CodeGeneratorRequest.parameter)
 }
-inline void CodeGeneratorRequest::set_parameter(const char* value, size_t size) {
+inline void CodeGeneratorRequest::set_parameter(const char* value,
+    size_t size) {
   set_has_parameter();
-  if (parameter_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    parameter_ = new ::std::string;
-  }
-  parameter_->assign(reinterpret_cast<const char*>(value), size);
+  parameter_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.compiler.CodeGeneratorRequest.parameter)
 }
 inline ::std::string* CodeGeneratorRequest::mutable_parameter() {
   set_has_parameter();
-  if (parameter_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    parameter_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.compiler.CodeGeneratorRequest.parameter)
-  return parameter_;
+  return parameter_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* CodeGeneratorRequest::release_parameter() {
   clear_has_parameter();
-  if (parameter_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = parameter_;
-    parameter_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return parameter_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* CodeGeneratorRequest::unsafe_arena_release_parameter() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_parameter();
+  return parameter_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void CodeGeneratorRequest::set_allocated_parameter(::std::string* parameter) {
-  if (parameter_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete parameter_;
+  if (parameter != NULL) {
+    set_has_parameter();
+  } else {
+    clear_has_parameter();
   }
-  if (parameter) {
+  parameter_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), parameter,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.compiler.CodeGeneratorRequest.parameter)
+}
+inline void CodeGeneratorRequest::unsafe_arena_set_allocated_parameter(
+    ::std::string* parameter) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (parameter != NULL) {
     set_has_parameter();
-    parameter_ = parameter;
   } else {
     clear_has_parameter();
-    parameter_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_parameter();
+  parameter_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      parameter, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.compiler.CodeGeneratorRequest.parameter)
 }
 
@@ -549,68 +636,67 @@ inline void CodeGeneratorResponse_File::clear_has_name() {
   _has_bits_[0] &= ~0x00000001u;
 }
 inline void CodeGeneratorResponse_File::clear_name() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_->clear();
-  }
+  name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_name();
 }
 inline const ::std::string& CodeGeneratorResponse_File::name() const {
   // @@protoc_insertion_point(field_get:google.protobuf.compiler.CodeGeneratorResponse.File.name)
-  return *name_;
+  return name_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void CodeGeneratorResponse_File::set_name(const ::std::string& value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.compiler.CodeGeneratorResponse.File.name)
 }
 inline void CodeGeneratorResponse_File::set_name(const char* value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.compiler.CodeGeneratorResponse.File.name)
 }
-inline void CodeGeneratorResponse_File::set_name(const char* value, size_t size) {
+inline void CodeGeneratorResponse_File::set_name(const char* value,
+    size_t size) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(reinterpret_cast<const char*>(value), size);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.compiler.CodeGeneratorResponse.File.name)
 }
 inline ::std::string* CodeGeneratorResponse_File::mutable_name() {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.compiler.CodeGeneratorResponse.File.name)
-  return name_;
+  return name_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* CodeGeneratorResponse_File::release_name() {
   clear_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = name_;
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return name_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* CodeGeneratorResponse_File::unsafe_arena_release_name() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_name();
+  return name_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void CodeGeneratorResponse_File::set_allocated_name(::std::string* name) {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
+  if (name != NULL) {
+    set_has_name();
+  } else {
+    clear_has_name();
   }
-  if (name) {
+  name_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), name,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.compiler.CodeGeneratorResponse.File.name)
+}
+inline void CodeGeneratorResponse_File::unsafe_arena_set_allocated_name(
+    ::std::string* name) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (name != NULL) {
     set_has_name();
-    name_ = name;
   } else {
     clear_has_name();
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_name();
+  name_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      name, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.compiler.CodeGeneratorResponse.File.name)
 }
 
@@ -625,68 +711,67 @@ inline void CodeGeneratorResponse_File::clear_has_insertion_point() {
   _has_bits_[0] &= ~0x00000002u;
 }
 inline void CodeGeneratorResponse_File::clear_insertion_point() {
-  if (insertion_point_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    insertion_point_->clear();
-  }
+  insertion_point_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_insertion_point();
 }
 inline const ::std::string& CodeGeneratorResponse_File::insertion_point() const {
   // @@protoc_insertion_point(field_get:google.protobuf.compiler.CodeGeneratorResponse.File.insertion_point)
-  return *insertion_point_;
+  return insertion_point_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void CodeGeneratorResponse_File::set_insertion_point(const ::std::string& value) {
   set_has_insertion_point();
-  if (insertion_point_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    insertion_point_ = new ::std::string;
-  }
-  insertion_point_->assign(value);
+  insertion_point_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.compiler.CodeGeneratorResponse.File.insertion_point)
 }
 inline void CodeGeneratorResponse_File::set_insertion_point(const char* value) {
   set_has_insertion_point();
-  if (insertion_point_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    insertion_point_ = new ::std::string;
-  }
-  insertion_point_->assign(value);
+  insertion_point_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.compiler.CodeGeneratorResponse.File.insertion_point)
 }
-inline void CodeGeneratorResponse_File::set_insertion_point(const char* value, size_t size) {
+inline void CodeGeneratorResponse_File::set_insertion_point(const char* value,
+    size_t size) {
   set_has_insertion_point();
-  if (insertion_point_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    insertion_point_ = new ::std::string;
-  }
-  insertion_point_->assign(reinterpret_cast<const char*>(value), size);
+  insertion_point_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.compiler.CodeGeneratorResponse.File.insertion_point)
 }
 inline ::std::string* CodeGeneratorResponse_File::mutable_insertion_point() {
   set_has_insertion_point();
-  if (insertion_point_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    insertion_point_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.compiler.CodeGeneratorResponse.File.insertion_point)
-  return insertion_point_;
+  return insertion_point_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* CodeGeneratorResponse_File::release_insertion_point() {
   clear_has_insertion_point();
-  if (insertion_point_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = insertion_point_;
-    insertion_point_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return insertion_point_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* CodeGeneratorResponse_File::unsafe_arena_release_insertion_point() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_insertion_point();
+  return insertion_point_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void CodeGeneratorResponse_File::set_allocated_insertion_point(::std::string* insertion_point) {
-  if (insertion_point_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete insertion_point_;
+  if (insertion_point != NULL) {
+    set_has_insertion_point();
+  } else {
+    clear_has_insertion_point();
   }
-  if (insertion_point) {
+  insertion_point_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), insertion_point,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.compiler.CodeGeneratorResponse.File.insertion_point)
+}
+inline void CodeGeneratorResponse_File::unsafe_arena_set_allocated_insertion_point(
+    ::std::string* insertion_point) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (insertion_point != NULL) {
     set_has_insertion_point();
-    insertion_point_ = insertion_point;
   } else {
     clear_has_insertion_point();
-    insertion_point_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_insertion_point();
+  insertion_point_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      insertion_point, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.compiler.CodeGeneratorResponse.File.insertion_point)
 }
 
@@ -701,68 +786,67 @@ inline void CodeGeneratorResponse_File::clear_has_content() {
   _has_bits_[0] &= ~0x00000004u;
 }
 inline void CodeGeneratorResponse_File::clear_content() {
-  if (content_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    content_->clear();
-  }
+  content_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_content();
 }
 inline const ::std::string& CodeGeneratorResponse_File::content() const {
   // @@protoc_insertion_point(field_get:google.protobuf.compiler.CodeGeneratorResponse.File.content)
-  return *content_;
+  return content_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void CodeGeneratorResponse_File::set_content(const ::std::string& value) {
   set_has_content();
-  if (content_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    content_ = new ::std::string;
-  }
-  content_->assign(value);
+  content_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.compiler.CodeGeneratorResponse.File.content)
 }
 inline void CodeGeneratorResponse_File::set_content(const char* value) {
   set_has_content();
-  if (content_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    content_ = new ::std::string;
-  }
-  content_->assign(value);
+  content_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.compiler.CodeGeneratorResponse.File.content)
 }
-inline void CodeGeneratorResponse_File::set_content(const char* value, size_t size) {
+inline void CodeGeneratorResponse_File::set_content(const char* value,
+    size_t size) {
   set_has_content();
-  if (content_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    content_ = new ::std::string;
-  }
-  content_->assign(reinterpret_cast<const char*>(value), size);
+  content_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.compiler.CodeGeneratorResponse.File.content)
 }
 inline ::std::string* CodeGeneratorResponse_File::mutable_content() {
   set_has_content();
-  if (content_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    content_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.compiler.CodeGeneratorResponse.File.content)
-  return content_;
+  return content_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* CodeGeneratorResponse_File::release_content() {
   clear_has_content();
-  if (content_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = content_;
-    content_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return content_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* CodeGeneratorResponse_File::unsafe_arena_release_content() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_content();
+  return content_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void CodeGeneratorResponse_File::set_allocated_content(::std::string* content) {
-  if (content_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete content_;
+  if (content != NULL) {
+    set_has_content();
+  } else {
+    clear_has_content();
   }
-  if (content) {
+  content_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), content,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.compiler.CodeGeneratorResponse.File.content)
+}
+inline void CodeGeneratorResponse_File::unsafe_arena_set_allocated_content(
+    ::std::string* content) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (content != NULL) {
     set_has_content();
-    content_ = content;
   } else {
     clear_has_content();
-    content_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_content();
+  content_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      content, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.compiler.CodeGeneratorResponse.File.content)
 }
 
@@ -781,68 +865,67 @@ inline void CodeGeneratorResponse::clear_has_error() {
   _has_bits_[0] &= ~0x00000001u;
 }
 inline void CodeGeneratorResponse::clear_error() {
-  if (error_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    error_->clear();
-  }
+  error_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_error();
 }
 inline const ::std::string& CodeGeneratorResponse::error() const {
   // @@protoc_insertion_point(field_get:google.protobuf.compiler.CodeGeneratorResponse.error)
-  return *error_;
+  return error_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void CodeGeneratorResponse::set_error(const ::std::string& value) {
   set_has_error();
-  if (error_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    error_ = new ::std::string;
-  }
-  error_->assign(value);
+  error_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.compiler.CodeGeneratorResponse.error)
 }
 inline void CodeGeneratorResponse::set_error(const char* value) {
   set_has_error();
-  if (error_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    error_ = new ::std::string;
-  }
-  error_->assign(value);
+  error_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.compiler.CodeGeneratorResponse.error)
 }
-inline void CodeGeneratorResponse::set_error(const char* value, size_t size) {
+inline void CodeGeneratorResponse::set_error(const char* value,
+    size_t size) {
   set_has_error();
-  if (error_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    error_ = new ::std::string;
-  }
-  error_->assign(reinterpret_cast<const char*>(value), size);
+  error_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.compiler.CodeGeneratorResponse.error)
 }
 inline ::std::string* CodeGeneratorResponse::mutable_error() {
   set_has_error();
-  if (error_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    error_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.compiler.CodeGeneratorResponse.error)
-  return error_;
+  return error_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* CodeGeneratorResponse::release_error() {
   clear_has_error();
-  if (error_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = error_;
-    error_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return error_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* CodeGeneratorResponse::unsafe_arena_release_error() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_error();
+  return error_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void CodeGeneratorResponse::set_allocated_error(::std::string* error) {
-  if (error_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete error_;
+  if (error != NULL) {
+    set_has_error();
+  } else {
+    clear_has_error();
   }
-  if (error) {
+  error_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), error,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.compiler.CodeGeneratorResponse.error)
+}
+inline void CodeGeneratorResponse::unsafe_arena_set_allocated_error(
+    ::std::string* error) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (error != NULL) {
     set_has_error();
-    error_ = error;
   } else {
     clear_has_error();
-    error_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_error();
+  error_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      error, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.compiler.CodeGeneratorResponse.error)
 }
 
@@ -888,8 +971,8 @@ namespace google {
 namespace protobuf {
 
 
-}  // namespace google
 }  // namespace protobuf
+}  // namespace google
 #endif  // SWIG
 
 // @@protoc_insertion_point(global_scope)
diff --git a/src/google/protobuf/compiler/plugin.proto b/src/google/protobuf/compiler/plugin.proto
index b65379d7..e627289b 100644
--- a/src/google/protobuf/compiler/plugin.proto
+++ b/src/google/protobuf/compiler/plugin.proto
@@ -44,6 +44,7 @@
 // plugin should be named "protoc-gen-$NAME", and will then be used when the
 // flag "--${NAME}_out" is passed to protoc.
 
+syntax = "proto2";
 package google.protobuf.compiler;
 option java_package = "com.google.protobuf.compiler";
 option java_outer_classname = "PluginProtos";
diff --git a/src/google/protobuf/compiler/python/python_generator.cc b/src/google/protobuf/compiler/python/python_generator.cc
index 15e05da9..d72ca207 100644
--- a/src/google/protobuf/compiler/python/python_generator.cc
+++ b/src/google/protobuf/compiler/python/python_generator.cc
@@ -44,11 +44,15 @@
 // performance-minded Python code leverage the fast C++ implementation
 // directly.
 
+#include <google/protobuf/stubs/hash.h>
 #include <limits>
 #include <map>
-#include <utility>
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <string>
+#include <utility>
 #include <vector>
 
 #include <google/protobuf/compiler/python/python_generator.h>
@@ -69,6 +73,41 @@ namespace python {
 
 namespace {
 
+const char* const kKeywordList[] = {
+  "and", "as", "break", "class", "continue", "def", "elif", "else", "except",
+  "False", "for", "from", "if", "import", "not", "or", "raise", "return",
+  "True", "try", "with", "while", "yield"
+};
+
+hash_set<string> MakeKeywordsMap() {
+  hash_set<string> result;
+  for (int i = 0; i < GOOGLE_ARRAYSIZE(kKeywordList); ++i) {
+    result.insert(kKeywordList[i]);
+  }
+  return result;
+}
+
+hash_set<string>* keywords_ = NULL;
+GOOGLE_PROTOBUF_DECLARE_ONCE(keywords_once_);
+
+void InitKeywords() {
+  keywords_ = new hash_set<string>();
+  *keywords_ = MakeKeywordsMap();
+}
+
+hash_set<string>& GetKeywords() {
+  ::google::protobuf::GoogleOnceInit(&keywords_once_, &InitKeywords);
+  return *keywords_;
+}
+
+string FieldName(const FieldDescriptor& field) {
+  string result = field.name();
+  if (GetKeywords().count(result) > 0) {
+    result.append("_");
+  }
+  return result;
+}
+
 // Returns a copy of |filename| with any trailing ".protodevel" or ".proto
 // suffix stripped.
 // TODO(robinson): Unify with copy in compiler/cpp/internal/helpers.cc.
@@ -88,6 +127,37 @@ string ModuleName(const string& filename) {
 }
 
 
+// Returns the alias we assign to the module of the given .proto filename
+// when importing. See testPackageInitializationImport in
+// google/protobuf/python/reflection_test.py
+// to see why we need the alias.
+string ModuleAlias(const string& filename) {
+  string module_name = ModuleName(filename);
+  // We can't have dots in the module name, so we replace each with _dot_.
+  // But that could lead to a collision between a.b and a_dot_b, so we also
+  // duplicate each underscore.
+  GlobalReplaceSubstring("_", "__", &module_name);
+  GlobalReplaceSubstring(".", "_dot_", &module_name);
+  return module_name;
+}
+
+
+// Returns an import statement of form "from X.Y.Z import T" for the given
+// .proto filename.
+string ModuleImportStatement(const string& filename) {
+  string module_name = ModuleName(filename);
+  int last_dot_pos = module_name.rfind('.');
+  if (last_dot_pos == string::npos) {
+    // NOTE(petya): this is not tested as it would require a protocol buffer
+    // outside of any package, and I don't think that is easily achievable.
+    return "import " + module_name;
+  } else {
+    return "from " + module_name.substr(0, last_dot_pos) + " import " +
+        module_name.substr(last_dot_pos + 1);
+  }
+}
+
+
 // Returns the name of all containing types for descriptor,
 // in order from outermost to innermost, followed by descriptor's
 // own name.  Each name is separated by |separator|.
@@ -309,9 +379,12 @@ bool Generator::Generate(const FileDescriptor* file,
 // Prints Python imports for all modules imported by |file|.
 void Generator::PrintImports() const {
   for (int i = 0; i < file_->dependency_count(); ++i) {
-    string module_name = ModuleName(file_->dependency(i)->name());
-    printer_->Print("import $module$\n", "module",
-                    module_name);
+    const string& filename = file_->dependency(i)->name();
+    string import_statement = ModuleImportStatement(filename);
+    string module_alias = ModuleAlias(filename);
+    printer_->Print("$statement$ as $alias$\n", "statement",
+                    import_statement, "alias", module_alias);
+    CopyPublicDependenciesAliases(module_alias, file_->dependency(i));
   }
   printer_->Print("\n");
 
@@ -342,8 +415,9 @@ void Generator::PrintFileDescriptor() const {
   if (file_->dependency_count() != 0) {
     printer_->Print(",\ndependencies=[");
     for (int i = 0; i < file_->dependency_count(); ++i) {
-      string module_name = ModuleName(file_->dependency(i)->name());
-      printer_->Print("$module_name$.DESCRIPTOR,", "module_name", module_name);
+      string module_alias = ModuleAlias(file_->dependency(i)->name());
+      printer_->Print("$module_alias$.DESCRIPTOR,", "module_alias",
+                      module_alias);
     }
     printer_->Print("]");
   }
@@ -457,7 +531,7 @@ void Generator::PrintTopLevelExtensions() const {
     printer_->Print("$constant_name$ = $number$\n",
       "constant_name", constant_name,
       "number", SimpleItoa(extension_field.number()));
-    printer_->Print("$name$ = ", "name", extension_field.name());
+    printer_->Print("$name$ = ", "name", FieldName(extension_field));
     PrintFieldDescriptor(extension_field, is_extension);
     printer_->Print("\n");
   }
@@ -804,7 +878,7 @@ void Generator::AddExtensionToFileDescriptor(
     const FieldDescriptor& descriptor) const {
   map<string, string> m;
   m["descriptor_name"] = kDescriptorKey;
-  m["field_name"] = descriptor.name();
+  m["field_name"] = FieldName(descriptor);
   const char file_descriptor_template[] =
       "$descriptor_name$.extensions_by_name['$field_name$'] = "
       "$field_name$\n";
@@ -857,12 +931,12 @@ string Generator::FieldReferencingExpression(
   GOOGLE_CHECK_EQ(field.file(), file_) << field.file()->name() << " vs. "
                                 << file_->name();
   if (!containing_type) {
-    return field.name();
+    return FieldName(field);
   }
   return strings::Substitute(
       "$0.$1['$2']",
       ModuleLevelDescriptorName(*containing_type),
-      python_dict_name, field.name());
+      python_dict_name, FieldName(field));
 }
 
 // Prints containing_type for nested descriptors or enum descriptors.
@@ -991,7 +1065,7 @@ void Generator::PrintFieldDescriptor(
   string options_string;
   field.options().SerializeToString(&options_string);
   map<string, string> m;
-  m["name"] = field.name();
+  m["name"] = FieldName(field);
   m["full_name"] = field.full_name();
   m["index"] = SimpleItoa(field.index());
   m["number"] = SimpleItoa(field.number());
@@ -1084,7 +1158,7 @@ string Generator::ModuleLevelDescriptorName(
   // We now have the name relative to its own module.  Also qualify with
   // the module name iff this descriptor is from a different .proto file.
   if (descriptor.file() != file_) {
-    name = ModuleName(descriptor.file()->name()) + "." + name;
+    name = ModuleAlias(descriptor.file()->name()) + "." + name;
   }
   return name;
 }
@@ -1096,7 +1170,7 @@ string Generator::ModuleLevelDescriptorName(
 string Generator::ModuleLevelMessageName(const Descriptor& descriptor) const {
   string name = NamePrefixedWithNestedTypes(descriptor, ".");
   if (descriptor.file() != file_) {
-    name = ModuleName(descriptor.file()->name()) + "." + name;
+    name = ModuleAlias(descriptor.file()->name()) + "." + name;
   }
   return name;
 }
@@ -1109,7 +1183,7 @@ string Generator::ModuleLevelServiceDescriptorName(
   UpperString(&name);
   name = "_" + name;
   if (descriptor.file() != file_) {
-    name = ModuleName(descriptor.file()->name()) + "." + name;
+    name = ModuleAlias(descriptor.file()->name()) + "." + name;
   }
   return name;
 }
@@ -1211,7 +1285,7 @@ void Generator::FixOptionsForField(
     if (field.is_extension()) {
       if (field.extension_scope() == NULL) {
         // Top level extensions.
-        field_name = field.name();
+        field_name = FieldName(field);
       } else {
         field_name = FieldReferencingExpression(
             field.extension_scope(), field, "extensions_by_name");
@@ -1256,6 +1330,18 @@ void Generator::FixOptionsForMessage(const Descriptor& descriptor) const {
   }
 }
 
+// If a dependency forwards other files through public dependencies, let's
+// copy over the corresponding module aliases.
+void Generator::CopyPublicDependenciesAliases(
+    const string& copy_from, const FileDescriptor* file) const {
+  for (int i = 0; i < file->public_dependency_count(); ++i) {
+    string module_alias = ModuleAlias(file->public_dependency(i)->name());
+    printer_->Print("$alias$ = $copy_from$.$alias$\n", "alias", module_alias,
+                    "copy_from", copy_from);
+    CopyPublicDependenciesAliases(copy_from, file->public_dependency(i));
+  }
+}
+
 }  // namespace python
 }  // namespace compiler
 }  // namespace protobuf
diff --git a/src/google/protobuf/compiler/python/python_generator.h b/src/google/protobuf/compiler/python/python_generator.h
index f86e9ea2..7e8f58e5 100644
--- a/src/google/protobuf/compiler/python/python_generator.h
+++ b/src/google/protobuf/compiler/python/python_generator.h
@@ -148,6 +148,9 @@ class LIBPROTOC_EXPORT Generator : public CodeGenerator {
   void FixOptionsForEnum(const EnumDescriptor& descriptor) const;
   void FixOptionsForMessage(const Descriptor& descriptor) const;
 
+  void CopyPublicDependenciesAliases(
+      const string& copy_from, const FileDescriptor* file) const;
+
   // Very coarse-grained lock to ensure that Generate() is reentrant.
   // Guards file_, printer_ and file_descriptor_serialized_.
   mutable Mutex mutex_;
diff --git a/src/google/protobuf/compiler/python/python_plugin_unittest.cc b/src/google/protobuf/compiler/python/python_plugin_unittest.cc
index 09dbc654..24c2f971 100644
--- a/src/google/protobuf/compiler/python/python_plugin_unittest.cc
+++ b/src/google/protobuf/compiler/python/python_plugin_unittest.cc
@@ -35,6 +35,9 @@
 //   worth.
 
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 
 #include <google/protobuf/compiler/python/python_generator.h>
 #include <google/protobuf/compiler/command_line_interface.h>
diff --git a/src/google/protobuf/descriptor.cc b/src/google/protobuf/descriptor.cc
index 21dda598..ab8691fd 100644
--- a/src/google/protobuf/descriptor.cc
+++ b/src/google/protobuf/descriptor.cc
@@ -54,6 +54,7 @@
 #include <google/protobuf/io/zero_copy_stream_impl.h>
 #include <google/protobuf/stubs/common.h>
 #include <google/protobuf/stubs/once.h>
+#include <google/protobuf/stubs/stringprintf.h>
 #include <google/protobuf/stubs/strutil.h>
 #include <google/protobuf/stubs/substitute.h>
 #include <google/protobuf/stubs/map_util.h>
@@ -134,6 +135,17 @@ const char * const FieldDescriptor::kLabelToName[MAX_LABEL + 1] = {
   "repeated",  // LABEL_REPEATED
 };
 
+const char* FileDescriptor::SyntaxName(FileDescriptor::Syntax syntax) {
+  switch (syntax) {
+    case SYNTAX_PROTO2:
+      return "proto2";
+    case SYNTAX_PROTO3:
+      return "proto3";
+    case SYNTAX_UNKNOWN:
+      return "unknown";
+  }
+}
+
 static const char * const kNonLinkedWeakMessageReplacementName = "google.protobuf.Empty";
 
 #ifndef _MSC_VER  // MSVC doesn't need these and won't even accept them.
@@ -144,8 +156,8 @@ const int FieldDescriptor::kLastReservedNumber;
 
 namespace {
 
-string ToCamelCase(const string& input) {
-  bool capitalize_next = false;
+string ToCamelCase(const string& input, bool lower_first) {
+  bool capitalize_next = !lower_first;
   string result;
   result.reserve(input.size());
 
@@ -166,8 +178,8 @@ string ToCamelCase(const string& input) {
   }
 
   // Lower-case the first letter.
-  if (!result.empty() && 'A' <= result[0] && result[0] <= 'Z') {
-    result[0] = result[0] - 'A' + 'a';
+  if (lower_first && !result.empty() && 'A' <= result[0] && result[0] <= 'Z') {
+      result[0] = result[0] - 'A' + 'a';
   }
 
   return result;
@@ -327,6 +339,31 @@ typedef hash_map<EnumIntPair, const EnumValueDescriptor*,
 typedef map<DescriptorIntPair, const FieldDescriptor*>
   ExtensionsGroupedByDescriptorMap;
 typedef hash_map<string, const SourceCodeInfo_Location*> LocationsByPathMap;
+
+set<string>* allowed_proto3_extendees_ = NULL;
+GOOGLE_PROTOBUF_DECLARE_ONCE(allowed_proto3_extendees_init_);
+
+void InitAllowedProto3Extendee() {
+  allowed_proto3_extendees_ = new set<string>;
+  allowed_proto3_extendees_->insert("google.protobuf.FileOptions");
+  allowed_proto3_extendees_->insert("google.protobuf.MessageOptions");
+  allowed_proto3_extendees_->insert("google.protobuf.FieldOptions");
+  allowed_proto3_extendees_->insert("google.protobuf.EnumOptions");
+  allowed_proto3_extendees_->insert("google.protobuf.EnumValueOptions");
+  allowed_proto3_extendees_->insert("google.protobuf.ServiceOptions");
+  allowed_proto3_extendees_->insert("google.protobuf.MethodOptions");
+}
+
+// Checks whether the extendee type is allowed in proto3.
+// Only extensions to descriptor options are allowed. We use name comparison
+// instead of comparing the descriptor directly because the extensions may be
+// defined in a different pool.
+bool AllowedExtendeeInProto3(const string& name) {
+  ::google::protobuf::GoogleOnceInit(&allowed_proto3_extendees_init_, &InitAllowedProto3Extendee);
+  return allowed_proto3_extendees_->find(name) !=
+         allowed_proto3_extendees_->end();
+}
+
 }  // anonymous namespace
 
 // ===================================================================
@@ -532,6 +569,9 @@ class FileDescriptorTables {
     const void* parent, const string& camelcase_name) const;
   inline const EnumValueDescriptor* FindEnumValueByNumber(
     const EnumDescriptor* parent, int number) const;
+  // This creates a new EnumValueDescriptor if not found, in a thread-safe way.
+  inline const EnumValueDescriptor* FindEnumValueByNumberCreatingIfUnknown(
+      const EnumDescriptor* parent, int number) const;
 
   // -----------------------------------------------------------------
   // Adding items.
@@ -567,10 +607,16 @@ class FileDescriptorTables {
   FieldsByNameMap       fields_by_camelcase_name_;
   FieldsByNumberMap     fields_by_number_;       // Not including extensions.
   EnumValuesByNumberMap enum_values_by_number_;
+  mutable EnumValuesByNumberMap unknown_enum_values_by_number_
+      GOOGLE_GUARDED_BY(unknown_enum_values_mu_);
 
   // Populated on first request to save space, hence constness games.
   mutable GoogleOnceDynamic locations_by_path_once_;
   mutable LocationsByPathMap locations_by_path_;
+
+  // Mutex to protect the unknown-enum-value map due to dynamic
+  // EnumValueDescriptor creation on unknown values.
+  mutable Mutex unknown_enum_values_mu_;
 };
 
 DescriptorPool::Tables::Tables()
@@ -600,7 +646,8 @@ FileDescriptorTables::FileDescriptorTables()
       fields_by_lowercase_name_(3),
       fields_by_camelcase_name_(3),
       fields_by_number_(3),
-      enum_values_by_number_(3) {
+      enum_values_by_number_(3),
+      unknown_enum_values_by_number_(3) {
 }
 
 FileDescriptorTables::~FileDescriptorTables() {}
@@ -749,6 +796,60 @@ inline const EnumValueDescriptor* FileDescriptorTables::FindEnumValueByNumber(
   return FindPtrOrNull(enum_values_by_number_, make_pair(parent, number));
 }
 
+inline const EnumValueDescriptor*
+FileDescriptorTables::FindEnumValueByNumberCreatingIfUnknown(
+    const EnumDescriptor* parent, int number) const {
+  // First try, with map of compiled-in values.
+  {
+    const EnumValueDescriptor* desc = FindPtrOrNull(
+        enum_values_by_number_, make_pair(parent, number));
+    if (desc != NULL) {
+      return desc;
+    }
+  }
+  // Second try, with reader lock held on unknown enum values: common case.
+  {
+    ReaderMutexLock l(&unknown_enum_values_mu_);
+    const EnumValueDescriptor* desc = FindPtrOrNull(
+        unknown_enum_values_by_number_, make_pair(parent, number));
+    if (desc != NULL) {
+      return desc;
+    }
+  }
+  // If not found, try again with writer lock held, and create new descriptor if
+  // necessary.
+  {
+    WriterMutexLock l(&unknown_enum_values_mu_);
+    const EnumValueDescriptor* desc = FindPtrOrNull(
+        unknown_enum_values_by_number_, make_pair(parent, number));
+    if (desc != NULL) {
+      return desc;
+    }
+
+    // Create an EnumValueDescriptor dynamically. We don't insert it into the
+    // EnumDescriptor (it's not a part of the enum as originally defined), but
+    // we do insert it into the table so that we can return the same pointer
+    // later.
+    string enum_value_name = StringPrintf(
+        "UNKNOWN_ENUM_VALUE_%s_%d", parent->name().c_str(), number);
+    DescriptorPool::Tables* tables =
+        const_cast<DescriptorPool::Tables*>(DescriptorPool::generated_pool()->
+                                            tables_.get());
+    EnumValueDescriptor* result = tables->Allocate<EnumValueDescriptor>();
+    result->name_ = tables->AllocateString(enum_value_name);
+    result->full_name_ = tables->AllocateString(parent->full_name() +
+                                                "." + enum_value_name);
+    result->number_ = number;
+    result->type_ = parent;
+    result->options_ = &EnumValueOptions::default_instance();
+    InsertIfNotPresent(&unknown_enum_values_by_number_,
+                       make_pair(parent, number),
+                       result);
+    return result;
+  }
+}
+
+
 inline const FieldDescriptor* DescriptorPool::Tables::FindExtension(
     const Descriptor* extendee, int number) {
   return FindPtrOrNull(extensions_, make_pair(extendee, number));
@@ -1311,6 +1412,11 @@ EnumDescriptor::FindValueByNumber(int key) const {
   return file()->tables_->FindEnumValueByNumber(this, key);
 }
 
+const EnumValueDescriptor*
+EnumDescriptor::FindValueByNumberCreatingIfUnknown(int key) const {
+  return file()->tables_->FindEnumValueByNumberCreatingIfUnknown(this, key);
+}
+
 const MethodDescriptor*
 ServiceDescriptor::FindMethodByName(const string& key) const {
   Symbol result =
@@ -1562,6 +1668,8 @@ string FieldDescriptor::DefaultValueAsString(bool quote_string_type) const {
 void FileDescriptor::CopyTo(FileDescriptorProto* proto) const {
   proto->set_name(name());
   if (!package().empty()) proto->set_package(package());
+  // TODO(liujisi): Also populate when syntax="proto2".
+  if (syntax() == SYNTAX_PROTO3) proto->set_syntax(SyntaxName(syntax()));
 
   for (int i = 0; i < dependency_count(); i++) {
     proto->add_dependency(dependency(i)->name());
@@ -1594,7 +1702,8 @@ void FileDescriptor::CopyTo(FileDescriptorProto* proto) const {
 }
 
 void FileDescriptor::CopySourceCodeInfoTo(FileDescriptorProto* proto) const {
-  if (source_code_info_ != &SourceCodeInfo::default_instance()) {
+  if (source_code_info_ &&
+      source_code_info_ != &SourceCodeInfo::default_instance()) {
     proto->mutable_source_code_info()->CopyFrom(*source_code_info_);
   }
 }
@@ -1802,10 +1911,67 @@ bool FormatLineOptions(int depth, const Message &options, string *output) {
   return !all_options.empty();
 }
 
+template<typename DescType>
+class SourceLocationCommentPrinter {
+ public:
+  SourceLocationCommentPrinter(const DescType* desc,
+                               const string& prefix,
+                               const DebugStringOptions& options)
+      : options_(options), prefix_(prefix) {
+    // Perform the SourceLocation lookup only if we're including user comments,
+    // because the lookup is fairly expensive.
+    have_source_loc_ = options.include_comments &&
+        desc->GetSourceLocation(&source_loc_);
+  }
+  void AddPreComment(string* output) {
+    if (have_source_loc_ && source_loc_.leading_comments.size() > 0) {
+      *output += FormatComment(source_loc_.leading_comments);
+    }
+  }
+  void AddPostComment(string* output) {
+    if (have_source_loc_ && source_loc_.trailing_comments.size() > 0) {
+      *output += FormatComment(source_loc_.trailing_comments);
+    }
+  }
+
+  // Format comment such that each line becomes a full-line C++-style comment in
+  // the DebugString() output.
+  string FormatComment(const string& comment_text) {
+    string stripped_comment = comment_text;
+    StripWhitespace(&stripped_comment);
+    vector<string> lines = Split(stripped_comment, "\n");
+    string output;
+    for (int i = 0; i < lines.size(); ++i) {
+      const string& line = lines[i];
+      strings::SubstituteAndAppend(&output, "$0// $1\n", prefix_, line);
+    }
+    return output;
+  }
+
+ private:
+  const DescType* desc_;
+  bool have_source_loc_;
+  SourceLocation source_loc_;
+  DebugStringOptions options_;
+  string prefix_;
+};
+
 }  // anonymous namespace
 
 string FileDescriptor::DebugString() const {
-  string contents = "syntax = \"proto2\";\n\n";
+  DebugStringOptions options;  // default options
+  return DebugStringWithOptions(options);
+}
+
+string FileDescriptor::DebugStringWithOptions(
+    const DebugStringOptions& debug_string_options) const {
+  string contents;
+  strings::SubstituteAndAppend(&contents, "syntax = \"$0\";\n\n",
+                               SyntaxName(syntax()));
+
+  SourceLocationCommentPrinter<FileDescriptor>
+      comment_printer(this, "", debug_string_options);
+  comment_printer.AddPreComment(&contents);
 
   set<int> public_dependencies;
   set<int> weak_dependencies;
@@ -1836,7 +2002,7 @@ string FileDescriptor::DebugString() const {
   }
 
   for (int i = 0; i < enum_type_count(); i++) {
-    enum_type(i)->DebugString(0, &contents);
+    enum_type(i)->DebugString(0, &contents, debug_string_options);
     contents.append("\n");
   }
 
@@ -1851,15 +2017,14 @@ string FileDescriptor::DebugString() const {
 
   for (int i = 0; i < message_type_count(); i++) {
     if (groups.count(message_type(i)) == 0) {
-      strings::SubstituteAndAppend(&contents, "message $0",
-                                   message_type(i)->name());
-      message_type(i)->DebugString(0, &contents);
+      message_type(i)->DebugString(0, &contents, debug_string_options,
+                                   /* include_opening_clause */ true);
       contents.append("\n");
     }
   }
 
   for (int i = 0; i < service_count(); i++) {
-    service(i)->DebugString(&contents);
+    service(i)->DebugString(&contents, debug_string_options);
     contents.append("\n");
   }
 
@@ -1871,23 +2036,46 @@ string FileDescriptor::DebugString() const {
       strings::SubstituteAndAppend(&contents, "extend .$0 {\n",
                                    containing_type->full_name());
     }
-    extension(i)->DebugString(1, FieldDescriptor::PRINT_LABEL, &contents);
+    extension(i)->DebugString(1, FieldDescriptor::PRINT_LABEL, &contents,
+                              debug_string_options);
   }
   if (extension_count() > 0) contents.append("}\n\n");
 
+  comment_printer.AddPostComment(&contents);
+
   return contents;
 }
 
 string Descriptor::DebugString() const {
+  DebugStringOptions options;  // default options
+  return DebugStringWithOptions(options);
+}
+
+string Descriptor::DebugStringWithOptions(
+    const DebugStringOptions& options) const {
   string contents;
-  strings::SubstituteAndAppend(&contents, "message $0", name());
-  DebugString(0, &contents);
+  DebugString(0, &contents, options, /* include_opening_clause */ true);
   return contents;
 }
 
-void Descriptor::DebugString(int depth, string *contents) const {
+void Descriptor::DebugString(int depth, string *contents,
+                             const DebugStringOptions&
+                             debug_string_options,
+                             bool include_opening_clause) const {
+  if (options().map_entry()) {
+    // Do not generate debug string for auto-generated map-entry type.
+    return;
+  }
   string prefix(depth * 2, ' ');
   ++depth;
+
+  SourceLocationCommentPrinter<Descriptor>
+      comment_printer(this, prefix, debug_string_options);
+  comment_printer.AddPreComment(contents);
+
+  if (include_opening_clause) {
+    strings::SubstituteAndAppend(contents, "$0message $1", prefix, name());
+  }
   contents->append(" {\n");
 
   FormatLineOptions(depth, options(), contents);
@@ -1909,20 +2097,21 @@ void Descriptor::DebugString(int depth, string *contents) const {
 
   for (int i = 0; i < nested_type_count(); i++) {
     if (groups.count(nested_type(i)) == 0) {
-      strings::SubstituteAndAppend(contents, "$0  message $1",
-                                   prefix, nested_type(i)->name());
-      nested_type(i)->DebugString(depth, contents);
+      nested_type(i)->DebugString(depth, contents, debug_string_options,
+                                  /* include_opening_clause */ true);
     }
   }
   for (int i = 0; i < enum_type_count(); i++) {
-    enum_type(i)->DebugString(depth, contents);
+    enum_type(i)->DebugString(depth, contents, debug_string_options);
   }
   for (int i = 0; i < field_count(); i++) {
     if (field(i)->containing_oneof() == NULL) {
-      field(i)->DebugString(depth, FieldDescriptor::PRINT_LABEL, contents);
+      field(i)->DebugString(depth, FieldDescriptor::PRINT_LABEL, contents,
+                            debug_string_options);
     } else if (field(i)->containing_oneof()->field(0) == field(i)) {
       // This is the first field in this oneof, so print the whole oneof.
-      field(i)->containing_oneof()->DebugString(depth, contents);
+      field(i)->containing_oneof()->DebugString(depth, contents,
+                                                debug_string_options);
     }
   }
 
@@ -1943,15 +2132,23 @@ void Descriptor::DebugString(int depth, string *contents) const {
                                    prefix, containing_type->full_name());
     }
     extension(i)->DebugString(
-        depth + 1, FieldDescriptor::PRINT_LABEL, contents);
+        depth + 1, FieldDescriptor::PRINT_LABEL, contents,
+        debug_string_options);
   }
   if (extension_count() > 0)
     strings::SubstituteAndAppend(contents, "$0  }\n", prefix);
 
   strings::SubstituteAndAppend(contents, "$0}\n", prefix);
+  comment_printer.AddPostComment(contents);
 }
 
 string FieldDescriptor::DebugString() const {
+  DebugStringOptions options;  // default options
+  return DebugStringWithOptions(options);
+}
+
+string FieldDescriptor::DebugStringWithOptions(
+    const DebugStringOptions& debug_string_options) const {
   string contents;
   int depth = 0;
   if (is_extension()) {
@@ -1959,35 +2156,55 @@ string FieldDescriptor::DebugString() const {
                                  containing_type()->full_name());
     depth = 1;
   }
-  DebugString(depth, PRINT_LABEL, &contents);
+  DebugString(depth, PRINT_LABEL, &contents, debug_string_options);
   if (is_extension()) {
     contents.append("}\n");
   }
   return contents;
 }
 
+// The field type string used in FieldDescriptor::DebugString()
+string FieldDescriptor::FieldTypeNameDebugString() const {
+  switch(type()) {
+    case TYPE_MESSAGE:
+      return "." + message_type()->full_name();
+    case TYPE_ENUM:
+      return "." + enum_type()->full_name();
+    default:
+      return kTypeToName[type()];
+  }
+}
+
 void FieldDescriptor::DebugString(int depth,
                                   PrintLabelFlag print_label_flag,
-                                  string *contents) const {
+                                  string *contents,
+                                  const DebugStringOptions&
+                                  debug_string_options) const {
   string prefix(depth * 2, ' ');
   string field_type;
-  switch (type()) {
-    case TYPE_MESSAGE:
-      field_type = "." + message_type()->full_name();
-      break;
-    case TYPE_ENUM:
-      field_type = "." + enum_type()->full_name();
-      break;
-    default:
-      field_type = kTypeToName[type()];
+
+  // Special case map fields.
+  bool is_map = false;
+  if (type() == TYPE_MESSAGE && message_type()->options().map_entry()) {
+    is_map = true;
+    strings::SubstituteAndAppend(
+        &field_type, "map<$0, $1>",
+        message_type()->field(0)->FieldTypeNameDebugString(),
+        message_type()->field(1)->FieldTypeNameDebugString());
+  } else {
+    field_type = FieldTypeNameDebugString();
   }
 
   string label;
-  if (print_label_flag == PRINT_LABEL) {
+  if (print_label_flag == PRINT_LABEL && !is_map) {
     label = kLabelToName[this->label()];
     label.push_back(' ');
   }
 
+  SourceLocationCommentPrinter<FieldDescriptor>
+      comment_printer(this, prefix, debug_string_options);
+  comment_printer.AddPreComment(contents);
+
   strings::SubstituteAndAppend(contents, "$0$1$2 $3 = $4",
                                prefix,
                                label,
@@ -2015,57 +2232,101 @@ void FieldDescriptor::DebugString(int depth,
   }
 
   if (type() == TYPE_GROUP) {
-    message_type()->DebugString(depth, contents);
+    message_type()->DebugString(depth, contents, debug_string_options,
+                                /* include_opening_clause */ false);
   } else {
     contents->append(";\n");
   }
+
+  comment_printer.AddPostComment(contents);
 }
 
 string OneofDescriptor::DebugString() const {
+  DebugStringOptions options;  // default values
+  return DebugStringWithOptions(options);
+}
+
+string OneofDescriptor::DebugStringWithOptions(
+    const DebugStringOptions& options) const {
   string contents;
-  DebugString(0, &contents);
+  DebugString(0, &contents, options);
   return contents;
 }
 
-void OneofDescriptor::DebugString(int depth, string* contents) const {
+void OneofDescriptor::DebugString(int depth, string* contents,
+                                  const DebugStringOptions&
+                                  debug_string_options) const {
   string prefix(depth * 2, ' ');
   ++depth;
+  SourceLocationCommentPrinter<OneofDescriptor>
+      comment_printer(this, prefix, debug_string_options);
+  comment_printer.AddPreComment(contents);
   strings::SubstituteAndAppend(
       contents, "$0 oneof $1 {\n", prefix, name());
   for (int i = 0; i < field_count(); i++) {
-    field(i)->DebugString(depth, FieldDescriptor::OMIT_LABEL, contents);
+    field(i)->DebugString(depth, FieldDescriptor::OMIT_LABEL, contents,
+                          debug_string_options);
   }
   strings::SubstituteAndAppend(contents, "$0}\n", prefix);
+  comment_printer.AddPostComment(contents);
 }
 
 string EnumDescriptor::DebugString() const {
+  DebugStringOptions options;  // default values
+  return DebugStringWithOptions(options);
+}
+
+string EnumDescriptor::DebugStringWithOptions(
+    const DebugStringOptions& options) const {
   string contents;
-  DebugString(0, &contents);
+  DebugString(0, &contents, options);
   return contents;
 }
 
-void EnumDescriptor::DebugString(int depth, string *contents) const {
+void EnumDescriptor::DebugString(int depth, string *contents,
+                                 const DebugStringOptions&
+                                 debug_string_options) const {
   string prefix(depth * 2, ' ');
   ++depth;
+
+  SourceLocationCommentPrinter<EnumDescriptor>
+      comment_printer(this, prefix, debug_string_options);
+  comment_printer.AddPreComment(contents);
+
   strings::SubstituteAndAppend(contents, "$0enum $1 {\n",
                                prefix, name());
 
   FormatLineOptions(depth, options(), contents);
 
   for (int i = 0; i < value_count(); i++) {
-    value(i)->DebugString(depth, contents);
+    value(i)->DebugString(depth, contents, debug_string_options);
   }
   strings::SubstituteAndAppend(contents, "$0}\n", prefix);
+
+  comment_printer.AddPostComment(contents);
 }
 
 string EnumValueDescriptor::DebugString() const {
+  DebugStringOptions options;  // default values
+  return DebugStringWithOptions(options);
+}
+
+string EnumValueDescriptor::DebugStringWithOptions(
+    const DebugStringOptions& options) const {
   string contents;
-  DebugString(0, &contents);
+  DebugString(0, &contents, options);
   return contents;
 }
 
-void EnumValueDescriptor::DebugString(int depth, string *contents) const {
+void EnumValueDescriptor::DebugString(int depth, string *contents,
+                                      const DebugStringOptions&
+                                      debug_string_options) const {
   string prefix(depth * 2, ' ');
+
+  SourceLocationCommentPrinter<EnumValueDescriptor>
+      comment_printer(this, prefix, debug_string_options);
+  comment_printer.AddPreComment(contents);
+
   strings::SubstituteAndAppend(contents, "$0$1 = $2",
                                prefix, name(), number());
 
@@ -2074,35 +2335,64 @@ void EnumValueDescriptor::DebugString(int depth, string *contents) const {
     strings::SubstituteAndAppend(contents, " [$0]", formatted_options);
   }
   contents->append(";\n");
+
+  comment_printer.AddPostComment(contents);
 }
 
 string ServiceDescriptor::DebugString() const {
+  DebugStringOptions options;  // default values
+  return DebugStringWithOptions(options);
+}
+
+string ServiceDescriptor::DebugStringWithOptions(
+    const DebugStringOptions& options) const {
   string contents;
-  DebugString(&contents);
+  DebugString(&contents, options);
   return contents;
 }
 
-void ServiceDescriptor::DebugString(string *contents) const {
+void ServiceDescriptor::DebugString(string *contents,
+                                    const DebugStringOptions&
+                                    debug_string_options) const {
+  SourceLocationCommentPrinter<ServiceDescriptor>
+      comment_printer(this, /* prefix */ "", debug_string_options);
+  comment_printer.AddPreComment(contents);
+
   strings::SubstituteAndAppend(contents, "service $0 {\n", name());
 
   FormatLineOptions(1, options(), contents);
 
   for (int i = 0; i < method_count(); i++) {
-    method(i)->DebugString(1, contents);
+    method(i)->DebugString(1, contents, debug_string_options);
   }
 
   contents->append("}\n");
+
+  comment_printer.AddPostComment(contents);
 }
 
 string MethodDescriptor::DebugString() const {
+  DebugStringOptions options;  // default values
+  return DebugStringWithOptions(options);
+}
+
+string MethodDescriptor::DebugStringWithOptions(
+    const DebugStringOptions& options) const {
   string contents;
-  DebugString(0, &contents);
+  DebugString(0, &contents, options);
   return contents;
 }
 
-void MethodDescriptor::DebugString(int depth, string *contents) const {
+void MethodDescriptor::DebugString(int depth, string *contents,
+                                   const DebugStringOptions&
+                                   debug_string_options) const {
   string prefix(depth * 2, ' ');
   ++depth;
+
+  SourceLocationCommentPrinter<MethodDescriptor>
+      comment_printer(this, prefix, debug_string_options);
+  comment_printer.AddPreComment(contents);
+
   strings::SubstituteAndAppend(contents, "$0rpc $1(.$2) returns (.$3)",
                                prefix, name(),
                                input_type()->full_name(),
@@ -2115,6 +2405,8 @@ void MethodDescriptor::DebugString(int depth, string *contents) const {
   } else {
     contents->append(";\n");
   }
+
+  comment_printer.AddPostComment(contents);
 }
 
 
@@ -2142,6 +2434,11 @@ bool FileDescriptor::GetSourceLocation(const vector<int>& path,
   return false;
 }
 
+bool FileDescriptor::GetSourceLocation(SourceLocation* out_location) const {
+  vector<int> path;  // empty path for root FileDescriptor
+  return GetSourceLocation(path, out_location);
+}
+
 bool FieldDescriptor::is_packed() const {
   return is_packable() && (options_ != NULL) && options_->packed();
 }
@@ -2409,7 +2706,7 @@ class DescriptorBuilder {
 
   // Creates a placeholder file.  Never returns NULL.  This is used when an
   // import is not found and AllowUnknownDependencies() is enabled.
-  const FileDescriptor* NewPlaceholderFile(const string& name);
+  FileDescriptor* NewPlaceholderFile(const string& name);
 
   // Calls tables_->AddSymbol() and records an error if it fails.  Returns
   // true if successful or false if failed, though most callers can ignore
@@ -2667,9 +2964,24 @@ class DescriptorBuilder {
                               const ServiceDescriptorProto& proto);
   void ValidateMethodOptions(MethodDescriptor* method,
                              const MethodDescriptorProto& proto);
-
-  void ValidateMapKey(FieldDescriptor* field,
-                      const FieldDescriptorProto& proto);
+  void ValidateProto3(FileDescriptor* file,
+                      const FileDescriptorProto& proto);
+  void ValidateProto3Message(Descriptor* message,
+                             const DescriptorProto& proto);
+  void ValidateProto3Field(FieldDescriptor* field,
+                           const FieldDescriptorProto& proto);
+  void ValidateProto3Enum(EnumDescriptor* enm,
+                          const EnumDescriptorProto& proto);
+
+  // Returns true if the map entry message is compatible with the
+  // auto-generated entry message from map fields syntax.
+  bool ValidateMapEntry(FieldDescriptor* field,
+                        const FieldDescriptorProto& proto);
+
+  // Recursively detects naming conflicts with map entry types for a
+  // better error message.
+  void DetectMapConflicts(const Descriptor* message,
+                          const DescriptorProto& proto);
 
 };
 
@@ -2992,19 +3304,9 @@ Symbol DescriptorBuilder::NewPlaceholder(const string& name,
   }
 
   // Create the placeholders.
-  FileDescriptor* placeholder_file = tables_->Allocate<FileDescriptor>();
-  memset(placeholder_file, 0, sizeof(*placeholder_file));
-
-  placeholder_file->source_code_info_ = &SourceCodeInfo::default_instance();
-
-  placeholder_file->name_ =
-    tables_->AllocateString(*placeholder_full_name + ".placeholder.proto");
+  FileDescriptor* placeholder_file = NewPlaceholderFile(
+      *placeholder_full_name + ".placeholder.proto");
   placeholder_file->package_ = placeholder_package;
-  placeholder_file->pool_ = pool_;
-  placeholder_file->options_ = &FileOptions::default_instance();
-  placeholder_file->tables_ = &FileDescriptorTables::kEmpty;
-  placeholder_file->is_placeholder_ = true;
-  // All other fields are zero or NULL.
 
   if (placeholder_type == PLACEHOLDER_ENUM) {
     placeholder_file->enum_type_count_ = 1;
@@ -3068,7 +3370,7 @@ Symbol DescriptorBuilder::NewPlaceholder(const string& name,
   }
 }
 
-const FileDescriptor* DescriptorBuilder::NewPlaceholderFile(
+FileDescriptor* DescriptorBuilder::NewPlaceholderFile(
     const string& name) {
   FileDescriptor* placeholder = tables_->Allocate<FileDescriptor>();
   memset(placeholder, 0, sizeof(*placeholder));
@@ -3078,7 +3380,9 @@ const FileDescriptor* DescriptorBuilder::NewPlaceholderFile(
   placeholder->pool_ = pool_;
   placeholder->options_ = &FileOptions::default_instance();
   placeholder->tables_ = &FileDescriptorTables::kEmpty;
+  placeholder->source_code_info_ = &SourceCodeInfo::default_instance();
   placeholder->is_placeholder_ = true;
+  placeholder->syntax_ = FileDescriptor::SYNTAX_PROTO2;
   // All other fields are zero or NULL.
 
   return placeholder;
@@ -3363,6 +3667,19 @@ const FileDescriptor* DescriptorBuilder::BuildFile(
              "Missing field: FileDescriptorProto.name.");
   }
 
+  // TODO(liujisi): Report error when the syntax is empty after all the protos
+  // have added the syntax statement.
+  if (proto.syntax().empty() || proto.syntax() == "proto2") {
+    file_->syntax_ = FileDescriptor::SYNTAX_PROTO2;
+  } else if (proto.syntax() == "proto3") {
+    file_->syntax_ = FileDescriptor::SYNTAX_PROTO3;
+  } else {
+    file_->syntax_ = FileDescriptor::SYNTAX_UNKNOWN;
+    AddError(proto.name(), proto, DescriptorPool::ErrorCollector::OTHER,
+             "Unrecognized syntax: " + proto.syntax());
+  }
+
+
   result->name_ = tables_->AllocateString(proto.name());
   if (proto.has_package()) {
     result->package_ = tables_->AllocateString(proto.package());
@@ -3506,6 +3823,14 @@ const FileDescriptor* DescriptorBuilder::BuildFile(
     ValidateFileOptions(result, proto);
   }
 
+  // Additional naming conflict check for map entry types. Only need to check
+  // this if there are already errors.
+  if (had_errors_) {
+    for (int i = 0; i < proto.message_type_size(); ++i) {
+      DetectMapConflicts(result->message_type(i), proto.message_type(i));
+    }
+  }
+
 
   if (!unused_dependency_.empty()) {
     LogUnusedDependency(result);
@@ -3621,7 +3946,9 @@ void DescriptorBuilder::BuildFieldOrExtension(const FieldDescriptorProto& proto,
   // Don't bother with the above optimization for camel-case names since
   // .proto files that follow the guide shouldn't be using names in this
   // format, so the optimization wouldn't help much.
-  result->camelcase_name_ = tables_->AllocateString(ToCamelCase(proto.name()));
+  result->camelcase_name_ =
+      tables_->AllocateString(ToCamelCase(proto.name(),
+                                          /* lower_first = */ true));
 
   // Some compilers do not allow static_cast directly between two enum types,
   // so we must cast to int first.
@@ -3646,7 +3973,6 @@ void DescriptorBuilder::BuildFieldOrExtension(const FieldDescriptorProto& proto,
   // Some of these may be filled in when cross-linking.
   result->containing_type_ = NULL;
   result->extension_scope_ = NULL;
-  result->experimental_map_key_ = NULL;
   result->message_type_ = NULL;
   result->enum_type_ = NULL;
 
@@ -4472,8 +4798,98 @@ void DescriptorBuilder::ValidateFileOptions(FileDescriptor* file,
       }
     }
   }
+  if (file->syntax() == FileDescriptor::SYNTAX_PROTO3) {
+    ValidateProto3(file, proto);
+  }
 }
 
+void DescriptorBuilder::ValidateProto3(
+    FileDescriptor* file, const FileDescriptorProto& proto) {
+  for (int i = 0; i < file->extension_count(); ++i) {
+    ValidateProto3Field(file->extensions_ + i, proto.extension(i));
+  }
+  for (int i = 0; i < file->message_type_count(); ++i) {
+    ValidateProto3Message(file->message_types_ + i, proto.message_type(i));
+  }
+  for (int i = 0; i < file->enum_type_count(); ++i) {
+    ValidateProto3Enum(file->enum_types_ + i, proto.enum_type(i));
+  }
+  if (IsLite(file)) {
+    AddError(file->name(), proto,
+             DescriptorPool::ErrorCollector::OTHER,
+             "Lite runtime is not supported in proto3.");
+  }
+}
+
+void DescriptorBuilder::ValidateProto3Message(
+    Descriptor* message, const DescriptorProto& proto) {
+  for (int i = 0; i < message->nested_type_count(); ++i) {
+    ValidateProto3Message(message->nested_types_ + i,
+                                 proto.nested_type(i));
+  }
+  for (int i = 0; i < message->enum_type_count(); ++i) {
+    ValidateProto3Enum(message->enum_types_ + i,
+                              proto.enum_type(i));
+  }
+  for (int i = 0; i < message->field_count(); ++i) {
+    ValidateProto3Field(message->fields_ + i, proto.field(i));
+  }
+  for (int i = 0; i < message->extension_count(); ++i) {
+    ValidateProto3Field(message->extensions_ +i, proto.extension(i));
+  }
+  if (message->extension_range_count() > 0) {
+    AddError(message->full_name(), proto,
+             DescriptorPool::ErrorCollector::OTHER,
+             "Extension ranges are not allowed in proto3.");
+  }
+  if (message->options().message_set_wire_format()) {
+    // Using MessageSet doesn't make sense since we disallow extensions.
+    AddError(message->full_name(), proto,
+             DescriptorPool::ErrorCollector::OTHER,
+             "MessageSet is not supported in proto3.");
+  }
+}
+
+void DescriptorBuilder::ValidateProto3Field(
+    FieldDescriptor* field, const FieldDescriptorProto& proto) {
+  if (field->is_extension() &&
+      !AllowedExtendeeInProto3(field->containing_type()->full_name())) {
+    AddError(field->full_name(), proto,
+             DescriptorPool::ErrorCollector::OTHER,
+             "Extensions in proto3 are only allowed for defining options.");
+  }
+  if (field->is_required()) {
+    AddError(field->full_name(), proto,
+             DescriptorPool::ErrorCollector::OTHER,
+             "Required fields are not allowed in proto3.");
+  }
+  if (field->has_default_value()) {
+    AddError(
+        field->full_name(), proto, DescriptorPool::ErrorCollector::OTHER,
+        "Explicit default values are not allowed in proto3.");
+  }
+  if (field->cpp_type() == FieldDescriptor::CPPTYPE_ENUM &&
+      field->enum_type() &&
+      field->enum_type()->file()->syntax() != FileDescriptor::SYNTAX_PROTO3) {
+    // Proto3 messages can only use Proto3 enum types; otherwise we can't
+    // guarantee that the default value is zero.
+    AddError(field->full_name(), proto,
+             DescriptorPool::ErrorCollector::TYPE,
+             "Enum type \"" + field->enum_type()->full_name() +
+             "\" is not a proto3 enum, but is used in \"" +
+             field->containing_type()->full_name() +
+             "\" which is a proto3 message type.");
+  }
+}
+
+void DescriptorBuilder::ValidateProto3Enum(
+    EnumDescriptor* enm, const EnumDescriptorProto& proto) {
+  if (enm->value_count() > 0 && enm->value(0)->number() != 0) {
+    AddError(
+        enm->full_name(), proto, DescriptorPool::ErrorCollector::OTHER,
+        "The first enum value must be zero in proto3.");
+  }
+}
 
 void DescriptorBuilder::ValidateMessageOptions(Descriptor* message,
                                                const DescriptorProto& proto) {
@@ -4499,10 +4915,6 @@ void DescriptorBuilder::ValidateMessageOptions(Descriptor* message,
 
 void DescriptorBuilder::ValidateFieldOptions(FieldDescriptor* field,
     const FieldDescriptorProto& proto) {
-  if (field->options().has_experimental_map_key()) {
-    ValidateMapKey(field, proto);
-  }
-
   // Only message type fields may be lazy.
   if (field->options().lazy()) {
     if (field->type() != FieldDescriptor::TYPE_MESSAGE) {
@@ -4551,6 +4963,17 @@ void DescriptorBuilder::ValidateFieldOptions(FieldDescriptor* field,
              "a lite type, but the reverse is allowed.");
   }
 
+  // Validate map types.
+  if (field->type() == FieldDescriptor::TYPE_MESSAGE &&
+      field->message_type()->options().map_entry()) {
+    if (!ValidateMapEntry(field, proto)) {
+      AddError(field->full_name(), proto,
+               DescriptorPool::ErrorCollector::OTHER,
+               "map_entry should not be set explicitly. Use map<KeyType, "
+               "ValueType> instead.");
+    }
+  }
+
 }
 
 void DescriptorBuilder::ValidateEnumOptions(EnumDescriptor* enm,
@@ -4608,57 +5031,127 @@ void DescriptorBuilder::ValidateMethodOptions(MethodDescriptor* /* method */,
   // Nothing to do so far.
 }
 
-void DescriptorBuilder::ValidateMapKey(FieldDescriptor* field,
-                                       const FieldDescriptorProto& proto) {
-  if (!field->is_repeated()) {
-    AddError(field->full_name(), proto, DescriptorPool::ErrorCollector::TYPE,
-             "map type is only allowed for repeated fields.");
-    return;
+bool DescriptorBuilder::ValidateMapEntry(FieldDescriptor* field,
+                                         const FieldDescriptorProto& proto) {
+  const Descriptor* message = field->message_type();
+  if (// Must not contain extensions, extension range or nested message or
+      // enums
+      message->extension_count() != 0 ||
+      field->label() != FieldDescriptor::LABEL_REPEATED ||
+      message->extension_range_count() != 0 ||
+      message->nested_type_count() != 0 || message->enum_type_count() != 0 ||
+      // Must contain exactly two fields
+      message->field_count() != 2 ||
+      // Field name and message name must match
+      message->name() != ToCamelCase(field->name(), false) + "Entry" ||
+      // Entry message must be in the same containing type of the field.
+      field->containing_type() != message->containing_type()) {
+    return false;
   }
 
-  if (field->cpp_type() != FieldDescriptor::CPPTYPE_MESSAGE) {
-    AddError(field->full_name(), proto, DescriptorPool::ErrorCollector::TYPE,
-             "map type is only allowed for fields with a message type.");
-    return;
+  const FieldDescriptor* key = message->field(0);
+  const FieldDescriptor* value = message->field(1);
+  if (key->label() != FieldDescriptor::LABEL_OPTIONAL || key->number() != 1 ||
+      key->name() != "key") {
+    return false;
+  }
+  if (value->label() != FieldDescriptor::LABEL_OPTIONAL ||
+      value->number() != 2 || value->name() != "value") {
+    return false;
   }
 
-  const Descriptor* item_type = field->message_type();
-  if (item_type == NULL) {
-    AddError(field->full_name(), proto, DescriptorPool::ErrorCollector::TYPE,
-             "Could not find field type.");
-    return;
+  // Check key types are legal.
+  switch (key->type()) {
+    case FieldDescriptor::TYPE_ENUM:
+      AddError(
+          field->full_name(), proto, DescriptorPool::ErrorCollector::TYPE,
+          "Key in map fields cannot be enum types.");
+      break;
+    case FieldDescriptor::TYPE_FLOAT:
+    case FieldDescriptor::TYPE_DOUBLE:
+    case FieldDescriptor::TYPE_MESSAGE:
+    case FieldDescriptor::TYPE_GROUP:
+    case FieldDescriptor::TYPE_BYTES:
+      AddError(
+          field->full_name(), proto, DescriptorPool::ErrorCollector::TYPE,
+          "Key in map fields cannot be float/double, bytes or message types.");
+      break;
+    case FieldDescriptor::TYPE_BOOL:
+    case FieldDescriptor::TYPE_INT32:
+    case FieldDescriptor::TYPE_INT64:
+    case FieldDescriptor::TYPE_SINT32:
+    case FieldDescriptor::TYPE_SINT64:
+    case FieldDescriptor::TYPE_STRING:
+    case FieldDescriptor::TYPE_UINT32:
+    case FieldDescriptor::TYPE_UINT64:
+    case FieldDescriptor::TYPE_FIXED32:
+    case FieldDescriptor::TYPE_FIXED64:
+    case FieldDescriptor::TYPE_SFIXED32:
+    case FieldDescriptor::TYPE_SFIXED64:
+      // Legal cases
+      break;
+    // Do not add a default, so that the compiler will complian when new types
+    // are added.
   }
 
-  // Find the field in item_type named by "experimental_map_key"
-  const string& key_name = field->options().experimental_map_key();
-  const Symbol key_symbol = LookupSymbol(
-      key_name,
-      // We append ".key_name" to the containing type's name since
-      // LookupSymbol() searches for peers of the supplied name, not
-      // children of the supplied name.
-      item_type->full_name() + "." + key_name);
+  return true;
+}
 
-  if (key_symbol.IsNull() || key_symbol.field_descriptor->is_extension()) {
-    AddError(field->full_name(), proto, DescriptorPool::ErrorCollector::TYPE,
-             "Could not find field named \"" + key_name + "\" in type \"" +
-             item_type->full_name() + "\".");
-    return;
+void DescriptorBuilder::DetectMapConflicts(const Descriptor* message,
+                                           const DescriptorProto& proto) {
+  map<string, const Descriptor*> seen_types;
+  for (int i = 0; i < message->nested_type_count(); ++i) {
+    const Descriptor* nested = message->nested_type(i);
+    pair<map<string, const Descriptor*>::iterator, bool> result =
+        seen_types.insert(make_pair(nested->name(), nested));
+    if (!result.second) {
+      if (result.first->second->options().map_entry() ||
+          nested->options().map_entry()) {
+        AddError(message->full_name(), proto,
+                 DescriptorPool::ErrorCollector::NAME,
+                 "Expanded map entry type " + nested->name() +
+                 " conflicts with an existing nested message type.");
+      }
+    }
+    // Recursively test on the nested types.
+    DetectMapConflicts(message->nested_type(i), proto.nested_type(i));
+  }
+  // Check for conflicted field names.
+  for (int i = 0; i < message->field_count(); ++i) {
+    const FieldDescriptor* field = message->field(i);
+    map<string, const Descriptor*>::iterator iter =
+        seen_types.find(field->name());
+    if (iter != seen_types.end() && iter->second->options().map_entry()) {
+      AddError(message->full_name(), proto,
+               DescriptorPool::ErrorCollector::NAME,
+               "Expanded map entry type " + iter->second->name() +
+               " conflicts with an existing field.");
+    }
   }
-  const FieldDescriptor* key_field = key_symbol.field_descriptor;
-
-  if (key_field->is_repeated()) {
-    AddError(field->full_name(), proto, DescriptorPool::ErrorCollector::TYPE,
-             "map_key must not name a repeated field.");
-    return;
+  // Check for conflicted enum names.
+  for (int i = 0; i < message->enum_type_count(); ++i) {
+    const EnumDescriptor* enum_desc = message->enum_type(i);
+    map<string, const Descriptor*>::iterator iter =
+        seen_types.find(enum_desc->name());
+    if (iter != seen_types.end() && iter->second->options().map_entry()) {
+      AddError(message->full_name(), proto,
+               DescriptorPool::ErrorCollector::NAME,
+               "Expanded map entry type " + iter->second->name() +
+               " conflicts with an existing enum type.");
+    }
   }
-
-  if (key_field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
-    AddError(field->full_name(), proto, DescriptorPool::ErrorCollector::TYPE,
-             "map key must name a scalar or string field.");
-    return;
+  // Check for conflicted oneof names.
+  for (int i = 0; i < message->oneof_decl_count(); ++i) {
+    const OneofDescriptor* oneof_desc = message->oneof_decl(i);
+    map<string, const Descriptor*>::iterator iter =
+        seen_types.find(oneof_desc->name());
+    if (iter != seen_types.end() && iter->second->options().map_entry()) {
+      AddError(message->full_name(), proto,
+               DescriptorPool::ErrorCollector::NAME,
+               "Expanded map entry type " + iter->second->name() +
+               " conflicts with an existing oneof type.");
+    }
   }
-
-  field->experimental_map_key_ = key_field;
 }
 
 
diff --git a/src/google/protobuf/descriptor.h b/src/google/protobuf/descriptor.h
index 68013f8e..b7ea756c 100644
--- a/src/google/protobuf/descriptor.h
+++ b/src/google/protobuf/descriptor.h
@@ -104,6 +104,11 @@ class FileDescriptorTables;
 // Defined in unknown_field_set.h.
 class UnknownField;
 
+// Defined in generated_message_reflection.h.
+namespace internal {
+  class GeneratedMessageReflection;
+}
+
 // NB, all indices are zero-based.
 struct SourceLocation {
   int start_line;
@@ -118,6 +123,20 @@ struct SourceLocation {
   string trailing_comments;
 };
 
+// Options when generating machine-parsable output from a descriptor with
+// DebugString().
+struct DebugStringOptions {
+  // include original user comments as recorded in SourceLocation entries. N.B.
+  // that this must be |false| by default: several other pieces of code (for
+  // example, the C++ code generation for fields in the proto compiler) rely on
+  // DebugString() output being unobstructed by user comments.
+  bool include_comments;
+
+  DebugStringOptions()
+      : include_comments(false)
+  {}
+};
+
 // Describes a type of protocol message, or a particular group within a
 // message.  To obtain the Descriptor for a given message object, call
 // Message::GetDescriptor().  Generated message classes also have a
@@ -162,6 +181,10 @@ class LIBPROTOBUF_EXPORT Descriptor {
   // will be suitable for re-parsing.
   string DebugString() const;
 
+  // Similar to DebugString(), but additionally takes options (e.g.,
+  // include original user comments in output).
+  string DebugStringWithOptions(const DebugStringOptions& options) const;
+
   // Returns true if this is a placeholder for an unknown type. This will
   // only be the case if this descriptor comes from a DescriptorPool
   // with AllowUnknownDependencies() set.
@@ -282,8 +305,12 @@ class LIBPROTOBUF_EXPORT Descriptor {
   typedef MessageOptions OptionsType;
 
   // Internal version of DebugString; controls the level of indenting for
-  // correct depth
-  void DebugString(int depth, string *contents) const;
+  // correct depth. Takes |options| to control debug-string options, and
+  // |include_opening_clause| to indicate whether the "message ... " part of the
+  // clause has already been generated (this varies depending on context).
+  void DebugString(int depth, string *contents,
+                   const DebugStringOptions& options,
+                   bool include_opening_clause) const;
 
   // Walks up the descriptor tree to generate the source location path
   // to this descriptor from the file root.
@@ -513,12 +540,6 @@ class LIBPROTOBUF_EXPORT FieldDescriptor {
   // returns null.
   const EnumDescriptor* enum_type() const;
 
-  // EXPERIMENTAL; DO NOT USE.
-  // If this field is a map field, experimental_map_key() is the field
-  // that is the key for this map.
-  // experimental_map_key()->containing_type() is the same as message_type().
-  const FieldDescriptor* experimental_map_key() const;
-
   // Get the FieldOptions for this field.  This includes things listed in
   // square brackets after the field definition.  E.g., the field:
   //   optional string text = 1 [ctype=CORD];
@@ -533,6 +554,9 @@ class LIBPROTOBUF_EXPORT FieldDescriptor {
   // See Descriptor::DebugString().
   string DebugString() const;
 
+  // See Descriptor::DebugStringWithOptions().
+  string DebugStringWithOptions(const DebugStringOptions& options) const;
+
   // Helper method to get the CppType for a particular Type.
   static CppType TypeToCppType(Type type);
 
@@ -558,13 +582,16 @@ class LIBPROTOBUF_EXPORT FieldDescriptor {
   // See Descriptor::DebugString().
   enum PrintLabelFlag { PRINT_LABEL, OMIT_LABEL };
   void DebugString(int depth, PrintLabelFlag print_label_flag,
-                   string* contents) const;
+                   string* contents, const DebugStringOptions& options) const;
 
   // formats the default value appropriately and returns it as a string.
   // Must have a default value to call this. If quote_string_type is true, then
   // types of CPPTYPE_STRING whill be surrounded by quotes and CEscaped.
   string DefaultValueAsString(bool quote_string_type) const;
 
+  // Helper function that returns the field type name for DebugString.
+  string FieldTypeNameDebugString() const;
+
   // Walks up the descriptor tree to generate the source location path
   // to this descriptor from the file root.
   void GetLocationPath(vector<int>* output) const;
@@ -584,7 +611,6 @@ class LIBPROTOBUF_EXPORT FieldDescriptor {
   const Descriptor* extension_scope_;
   const Descriptor* message_type_;
   const EnumDescriptor* enum_type_;
-  const FieldDescriptor* experimental_map_key_;
   const FieldOptions* options_;
   // IMPORTANT:  If you add a new field, make sure to search for all instances
   // of Allocate<FieldDescriptor>() and AllocateArray<FieldDescriptor>() in
@@ -645,6 +671,9 @@ class LIBPROTOBUF_EXPORT OneofDescriptor {
   // See Descriptor::DebugString().
   string DebugString() const;
 
+  // See Descriptor::DebugStringWithOptions().
+  string DebugStringWithOptions(const DebugStringOptions& options) const;
+
   // Source Location ---------------------------------------------------
 
   // Updates |*out_location| to the source location of the complete
@@ -654,7 +683,8 @@ class LIBPROTOBUF_EXPORT OneofDescriptor {
 
  private:
   // See Descriptor::DebugString().
-  void DebugString(int depth, string* contents) const;
+  void DebugString(int depth, string* contents,
+                   const DebugStringOptions& options) const;
 
   // Walks up the descriptor tree to generate the source location path
   // to this descriptor from the file root.
@@ -723,6 +753,10 @@ class LIBPROTOBUF_EXPORT EnumDescriptor {
   // See Descriptor::DebugString().
   string DebugString() const;
 
+  // See Descriptor::DebugStringWithOptions().
+  string DebugStringWithOptions(const DebugStringOptions& options) const;
+
+
   // Returns true if this is a placeholder for an unknown enum. This will
   // only be the case if this descriptor comes from a DescriptorPool
   // with AllowUnknownDependencies() set.
@@ -738,8 +772,21 @@ class LIBPROTOBUF_EXPORT EnumDescriptor {
  private:
   typedef EnumOptions OptionsType;
 
+  // Looks up a value by number.  If the value does not exist, dynamically
+  // creates a new EnumValueDescriptor for that value, assuming that it was
+  // unknown. If a new descriptor is created, this is done in a thread-safe way,
+  // and future calls will return the same value descriptor pointer.
+  //
+  // This is private but is used by GeneratedMessageReflection (which is
+  // friended below) to return a valid EnumValueDescriptor from GetEnum() when
+  // this feature is enabled.
+  const EnumValueDescriptor*
+      FindValueByNumberCreatingIfUnknown(int number) const;
+
+
   // See Descriptor::DebugString().
-  void DebugString(int depth, string *contents) const;
+  void DebugString(int depth, string *contents,
+                   const DebugStringOptions& options) const;
 
   // Walks up the descriptor tree to generate the source location path
   // to this descriptor from the file root.
@@ -769,6 +816,7 @@ class LIBPROTOBUF_EXPORT EnumDescriptor {
   friend class FieldDescriptor;
   friend class EnumValueDescriptor;
   friend class FileDescriptor;
+  friend class LIBPROTOBUF_EXPORT internal::GeneratedMessageReflection;
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(EnumDescriptor);
 };
 
@@ -806,6 +854,10 @@ class LIBPROTOBUF_EXPORT EnumValueDescriptor {
   // See Descriptor::DebugString().
   string DebugString() const;
 
+  // See Descriptor::DebugStringWithOptions().
+  string DebugStringWithOptions(const DebugStringOptions& options) const;
+
+
   // Source Location ---------------------------------------------------
 
   // Updates |*out_location| to the source location of the complete
@@ -817,7 +869,8 @@ class LIBPROTOBUF_EXPORT EnumValueDescriptor {
   typedef EnumValueOptions OptionsType;
 
   // See Descriptor::DebugString().
-  void DebugString(int depth, string *contents) const;
+  void DebugString(int depth, string *contents,
+                   const DebugStringOptions& options) const;
 
   // Walks up the descriptor tree to generate the source location path
   // to this descriptor from the file root.
@@ -836,6 +889,7 @@ class LIBPROTOBUF_EXPORT EnumValueDescriptor {
   EnumValueDescriptor() {}
   friend class DescriptorBuilder;
   friend class EnumDescriptor;
+  friend class FileDescriptorTables;
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(EnumValueDescriptor);
 };
 
@@ -876,6 +930,10 @@ class LIBPROTOBUF_EXPORT ServiceDescriptor {
   // See Descriptor::DebugString().
   string DebugString() const;
 
+  // See Descriptor::DebugStringWithOptions().
+  string DebugStringWithOptions(const DebugStringOptions& options) const;
+
+
   // Source Location ---------------------------------------------------
 
   // Updates |*out_location| to the source location of the complete
@@ -887,7 +945,7 @@ class LIBPROTOBUF_EXPORT ServiceDescriptor {
   typedef ServiceOptions OptionsType;
 
   // See Descriptor::DebugString().
-  void DebugString(string *contents) const;
+  void DebugString(string *contents, const DebugStringOptions& options) const;
 
   // Walks up the descriptor tree to generate the source location path
   // to this descriptor from the file root.
@@ -945,6 +1003,10 @@ class LIBPROTOBUF_EXPORT MethodDescriptor {
   // See Descriptor::DebugString().
   string DebugString() const;
 
+  // See Descriptor::DebugStringWithOptions().
+  string DebugStringWithOptions(const DebugStringOptions& options) const;
+
+
   // Source Location ---------------------------------------------------
 
   // Updates |*out_location| to the source location of the complete
@@ -956,7 +1018,8 @@ class LIBPROTOBUF_EXPORT MethodDescriptor {
   typedef MethodOptions OptionsType;
 
   // See Descriptor::DebugString().
-  void DebugString(int depth, string *contents) const;
+  void DebugString(int depth, string *contents,
+                   const DebugStringOptions& options) const;
 
   // Walks up the descriptor tree to generate the source location path
   // to this descriptor from the file root.
@@ -1052,6 +1115,15 @@ class LIBPROTOBUF_EXPORT FileDescriptor {
   // message.
   const FileOptions& options() const;
 
+  // Syntax of this file.
+  enum Syntax {
+    SYNTAX_UNKNOWN = 0,
+    SYNTAX_PROTO2  = 2,
+    SYNTAX_PROTO3  = 3,
+  };
+  Syntax syntax() const;
+  static const char* SyntaxName(Syntax syntax);
+
   // Find a top-level message type by name.  Returns NULL if not found.
   const Descriptor* FindMessageTypeByName(const string& name) const;
   // Find a top-level enum type by name.  Returns NULL if not found.
@@ -1082,11 +1154,18 @@ class LIBPROTOBUF_EXPORT FileDescriptor {
   // See Descriptor::DebugString().
   string DebugString() const;
 
+  // See Descriptor::DebugStringWithOptions().
+  string DebugStringWithOptions(const DebugStringOptions& options) const;
+
   // Returns true if this is a placeholder for an unknown file. This will
   // only be the case if this descriptor comes from a DescriptorPool
   // with AllowUnknownDependencies() set.
   bool is_placeholder() const;
 
+  // Updates |*out_location| to the source location of the complete extent of
+  // this file declaration (namely, the empty path).
+  bool GetSourceLocation(SourceLocation* out_location) const;
+
  private:
   // Source Location ---------------------------------------------------
 
@@ -1116,6 +1195,7 @@ class LIBPROTOBUF_EXPORT FileDescriptor {
   int service_count_;
   ServiceDescriptor* services_;
   int extension_count_;
+  Syntax syntax_;
   bool is_placeholder_;
   FieldDescriptor* extensions_;
   const FileOptions* options_;
@@ -1394,6 +1474,7 @@ class LIBPROTOBUF_EXPORT DescriptorPool {
   friend class ServiceDescriptor;
   friend class FileDescriptor;
   friend class DescriptorBuilder;
+  friend class FileDescriptorTables;
 
   // Return true if the given name is a sub-symbol of any non-package
   // descriptor that already exists in the descriptor pool.  (The full
@@ -1494,8 +1575,6 @@ PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, index_in_oneof, int)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, extension_scope, const Descriptor*)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, message_type, const Descriptor*)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, enum_type, const EnumDescriptor*)
-PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, experimental_map_key,
-                         const FieldDescriptor*)
 PROTOBUF_DEFINE_OPTIONS_ACCESSOR(FieldDescriptor, FieldOptions)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, has_default_value, bool)
 PROTOBUF_DEFINE_ACCESSOR(FieldDescriptor, default_value_int32 , int32 )
@@ -1679,6 +1758,10 @@ inline const FileDescriptor* FileDescriptor::weak_dependency(
   return dependencies_[weak_dependencies_[index]];
 }
 
+inline FileDescriptor::Syntax FileDescriptor::syntax() const {
+  return syntax_;
+}
+
 // Can't use PROTOBUF_DEFINE_ARRAY_ACCESSOR because fields_ is actually an array
 // of pointers rather than the usual array of objects.
 inline const FieldDescriptor* OneofDescriptor::field(int index) const {
diff --git a/src/google/protobuf/descriptor.pb.cc b/src/google/protobuf/descriptor.pb.cc
index c3aa2fb6..4fe01ce3 100644
--- a/src/google/protobuf/descriptor.pb.cc
+++ b/src/google/protobuf/descriptor.pb.cc
@@ -108,13 +108,14 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       FileDescriptorSet::default_instance_,
       FileDescriptorSet_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileDescriptorSet, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileDescriptorSet, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(FileDescriptorSet));
+      sizeof(FileDescriptorSet),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileDescriptorSet, _internal_metadata_));
   FileDescriptorProto_descriptor_ = file->message_type(1);
-  static const int FileDescriptorProto_offsets_[11] = {
+  static const int FileDescriptorProto_offsets_[12] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileDescriptorProto, name_),
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileDescriptorProto, package_),
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileDescriptorProto, dependency_),
@@ -126,6 +127,7 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileDescriptorProto, extension_),
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileDescriptorProto, options_),
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileDescriptorProto, source_code_info_),
+    GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileDescriptorProto, syntax_),
   };
   FileDescriptorProto_reflection_ =
     new ::google::protobuf::internal::GeneratedMessageReflection(
@@ -133,11 +135,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       FileDescriptorProto::default_instance_,
       FileDescriptorProto_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileDescriptorProto, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileDescriptorProto, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(FileDescriptorProto));
+      sizeof(FileDescriptorProto),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileDescriptorProto, _internal_metadata_));
   DescriptorProto_descriptor_ = file->message_type(2);
   static const int DescriptorProto_offsets_[8] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(DescriptorProto, name_),
@@ -155,11 +158,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       DescriptorProto::default_instance_,
       DescriptorProto_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(DescriptorProto, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(DescriptorProto, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(DescriptorProto));
+      sizeof(DescriptorProto),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(DescriptorProto, _internal_metadata_));
   DescriptorProto_ExtensionRange_descriptor_ = DescriptorProto_descriptor_->nested_type(0);
   static const int DescriptorProto_ExtensionRange_offsets_[2] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(DescriptorProto_ExtensionRange, start_),
@@ -171,11 +175,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       DescriptorProto_ExtensionRange::default_instance_,
       DescriptorProto_ExtensionRange_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(DescriptorProto_ExtensionRange, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(DescriptorProto_ExtensionRange, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(DescriptorProto_ExtensionRange));
+      sizeof(DescriptorProto_ExtensionRange),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(DescriptorProto_ExtensionRange, _internal_metadata_));
   FieldDescriptorProto_descriptor_ = file->message_type(3);
   static const int FieldDescriptorProto_offsets_[9] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FieldDescriptorProto, name_),
@@ -194,11 +199,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       FieldDescriptorProto::default_instance_,
       FieldDescriptorProto_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FieldDescriptorProto, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FieldDescriptorProto, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(FieldDescriptorProto));
+      sizeof(FieldDescriptorProto),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FieldDescriptorProto, _internal_metadata_));
   FieldDescriptorProto_Type_descriptor_ = FieldDescriptorProto_descriptor_->enum_type(0);
   FieldDescriptorProto_Label_descriptor_ = FieldDescriptorProto_descriptor_->enum_type(1);
   OneofDescriptorProto_descriptor_ = file->message_type(4);
@@ -211,11 +217,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       OneofDescriptorProto::default_instance_,
       OneofDescriptorProto_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(OneofDescriptorProto, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(OneofDescriptorProto, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(OneofDescriptorProto));
+      sizeof(OneofDescriptorProto),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(OneofDescriptorProto, _internal_metadata_));
   EnumDescriptorProto_descriptor_ = file->message_type(5);
   static const int EnumDescriptorProto_offsets_[3] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumDescriptorProto, name_),
@@ -228,11 +235,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       EnumDescriptorProto::default_instance_,
       EnumDescriptorProto_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumDescriptorProto, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumDescriptorProto, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(EnumDescriptorProto));
+      sizeof(EnumDescriptorProto),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumDescriptorProto, _internal_metadata_));
   EnumValueDescriptorProto_descriptor_ = file->message_type(6);
   static const int EnumValueDescriptorProto_offsets_[3] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumValueDescriptorProto, name_),
@@ -245,11 +253,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       EnumValueDescriptorProto::default_instance_,
       EnumValueDescriptorProto_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumValueDescriptorProto, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumValueDescriptorProto, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(EnumValueDescriptorProto));
+      sizeof(EnumValueDescriptorProto),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumValueDescriptorProto, _internal_metadata_));
   ServiceDescriptorProto_descriptor_ = file->message_type(7);
   static const int ServiceDescriptorProto_offsets_[3] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(ServiceDescriptorProto, name_),
@@ -262,11 +271,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       ServiceDescriptorProto::default_instance_,
       ServiceDescriptorProto_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(ServiceDescriptorProto, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(ServiceDescriptorProto, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(ServiceDescriptorProto));
+      sizeof(ServiceDescriptorProto),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(ServiceDescriptorProto, _internal_metadata_));
   MethodDescriptorProto_descriptor_ = file->message_type(8);
   static const int MethodDescriptorProto_offsets_[4] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MethodDescriptorProto, name_),
@@ -280,11 +290,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       MethodDescriptorProto::default_instance_,
       MethodDescriptorProto_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MethodDescriptorProto, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MethodDescriptorProto, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(MethodDescriptorProto));
+      sizeof(MethodDescriptorProto),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MethodDescriptorProto, _internal_metadata_));
   FileOptions_descriptor_ = file->message_type(9);
   static const int FileOptions_offsets_[12] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileOptions, java_package_),
@@ -306,17 +317,19 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       FileOptions::default_instance_,
       FileOptions_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileOptions, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileOptions, _unknown_fields_),
+      -1,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileOptions, _extensions_),
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(FileOptions));
+      sizeof(FileOptions),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FileOptions, _internal_metadata_));
   FileOptions_OptimizeMode_descriptor_ = FileOptions_descriptor_->enum_type(0);
   MessageOptions_descriptor_ = file->message_type(10);
-  static const int MessageOptions_offsets_[4] = {
+  static const int MessageOptions_offsets_[5] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MessageOptions, message_set_wire_format_),
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MessageOptions, no_standard_descriptor_accessor_),
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MessageOptions, deprecated_),
+    GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MessageOptions, map_entry_),
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MessageOptions, uninterpreted_option_),
   };
   MessageOptions_reflection_ =
@@ -325,18 +338,18 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       MessageOptions::default_instance_,
       MessageOptions_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MessageOptions, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MessageOptions, _unknown_fields_),
+      -1,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MessageOptions, _extensions_),
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(MessageOptions));
+      sizeof(MessageOptions),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MessageOptions, _internal_metadata_));
   FieldOptions_descriptor_ = file->message_type(11);
-  static const int FieldOptions_offsets_[7] = {
+  static const int FieldOptions_offsets_[6] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FieldOptions, ctype_),
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FieldOptions, packed_),
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FieldOptions, lazy_),
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FieldOptions, deprecated_),
-    GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FieldOptions, experimental_map_key_),
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FieldOptions, weak_),
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FieldOptions, uninterpreted_option_),
   };
@@ -346,11 +359,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       FieldOptions::default_instance_,
       FieldOptions_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FieldOptions, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FieldOptions, _unknown_fields_),
+      -1,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FieldOptions, _extensions_),
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(FieldOptions));
+      sizeof(FieldOptions),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(FieldOptions, _internal_metadata_));
   FieldOptions_CType_descriptor_ = FieldOptions_descriptor_->enum_type(0);
   EnumOptions_descriptor_ = file->message_type(12);
   static const int EnumOptions_offsets_[3] = {
@@ -364,11 +378,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       EnumOptions::default_instance_,
       EnumOptions_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumOptions, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumOptions, _unknown_fields_),
+      -1,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumOptions, _extensions_),
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(EnumOptions));
+      sizeof(EnumOptions),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumOptions, _internal_metadata_));
   EnumValueOptions_descriptor_ = file->message_type(13);
   static const int EnumValueOptions_offsets_[2] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumValueOptions, deprecated_),
@@ -380,11 +395,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       EnumValueOptions::default_instance_,
       EnumValueOptions_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumValueOptions, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumValueOptions, _unknown_fields_),
+      -1,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumValueOptions, _extensions_),
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(EnumValueOptions));
+      sizeof(EnumValueOptions),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(EnumValueOptions, _internal_metadata_));
   ServiceOptions_descriptor_ = file->message_type(14);
   static const int ServiceOptions_offsets_[2] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(ServiceOptions, deprecated_),
@@ -396,11 +412,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       ServiceOptions::default_instance_,
       ServiceOptions_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(ServiceOptions, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(ServiceOptions, _unknown_fields_),
+      -1,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(ServiceOptions, _extensions_),
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(ServiceOptions));
+      sizeof(ServiceOptions),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(ServiceOptions, _internal_metadata_));
   MethodOptions_descriptor_ = file->message_type(15);
   static const int MethodOptions_offsets_[2] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MethodOptions, deprecated_),
@@ -412,11 +429,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       MethodOptions::default_instance_,
       MethodOptions_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MethodOptions, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MethodOptions, _unknown_fields_),
+      -1,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MethodOptions, _extensions_),
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(MethodOptions));
+      sizeof(MethodOptions),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(MethodOptions, _internal_metadata_));
   UninterpretedOption_descriptor_ = file->message_type(16);
   static const int UninterpretedOption_offsets_[7] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(UninterpretedOption, name_),
@@ -433,11 +451,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       UninterpretedOption::default_instance_,
       UninterpretedOption_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(UninterpretedOption, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(UninterpretedOption, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(UninterpretedOption));
+      sizeof(UninterpretedOption),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(UninterpretedOption, _internal_metadata_));
   UninterpretedOption_NamePart_descriptor_ = UninterpretedOption_descriptor_->nested_type(0);
   static const int UninterpretedOption_NamePart_offsets_[2] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(UninterpretedOption_NamePart, name_part_),
@@ -449,11 +468,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       UninterpretedOption_NamePart::default_instance_,
       UninterpretedOption_NamePart_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(UninterpretedOption_NamePart, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(UninterpretedOption_NamePart, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(UninterpretedOption_NamePart));
+      sizeof(UninterpretedOption_NamePart),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(UninterpretedOption_NamePart, _internal_metadata_));
   SourceCodeInfo_descriptor_ = file->message_type(17);
   static const int SourceCodeInfo_offsets_[1] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(SourceCodeInfo, location_),
@@ -464,11 +484,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       SourceCodeInfo::default_instance_,
       SourceCodeInfo_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(SourceCodeInfo, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(SourceCodeInfo, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(SourceCodeInfo));
+      sizeof(SourceCodeInfo),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(SourceCodeInfo, _internal_metadata_));
   SourceCodeInfo_Location_descriptor_ = SourceCodeInfo_descriptor_->nested_type(0);
   static const int SourceCodeInfo_Location_offsets_[4] = {
     GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(SourceCodeInfo_Location, path_),
@@ -482,11 +503,12 @@ void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto() {
       SourceCodeInfo_Location::default_instance_,
       SourceCodeInfo_Location_offsets_,
       GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(SourceCodeInfo_Location, _has_bits_[0]),
-      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(SourceCodeInfo_Location, _unknown_fields_),
+      -1,
       -1,
       ::google::protobuf::DescriptorPool::generated_pool(),
       ::google::protobuf::MessageFactory::generated_factory(),
-      sizeof(SourceCodeInfo_Location));
+      sizeof(SourceCodeInfo_Location),
+      GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET(SourceCodeInfo_Location, _internal_metadata_));
 }
 
 namespace {
@@ -600,7 +622,7 @@ void protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto() {
     "\n google/protobuf/descriptor.proto\022\017goog"
     "le.protobuf\"G\n\021FileDescriptorSet\0222\n\004file"
     "\030\001 \003(\0132$.google.protobuf.FileDescriptorP"
-    "roto\"\313\003\n\023FileDescriptorProto\022\014\n\004name\030\001 \001"
+    "roto\"\333\003\n\023FileDescriptorProto\022\014\n\004name\030\001 \001"
     "(\t\022\017\n\007package\030\002 \001(\t\022\022\n\ndependency\030\003 \003(\t\022"
     "\031\n\021public_dependency\030\n \003(\005\022\027\n\017weak_depen"
     "dency\030\013 \003(\005\0226\n\014message_type\030\004 \003(\0132 .goog"
@@ -611,104 +633,104 @@ void protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto() {
     "\0132%.google.protobuf.FieldDescriptorProto"
     "\022-\n\007options\030\010 \001(\0132\034.google.protobuf.File"
     "Options\0229\n\020source_code_info\030\t \001(\0132\037.goog"
-    "le.protobuf.SourceCodeInfo\"\344\003\n\017Descripto"
-    "rProto\022\014\n\004name\030\001 \001(\t\0224\n\005field\030\002 \003(\0132%.go"
-    "ogle.protobuf.FieldDescriptorProto\0228\n\tex"
-    "tension\030\006 \003(\0132%.google.protobuf.FieldDes"
-    "criptorProto\0225\n\013nested_type\030\003 \003(\0132 .goog"
-    "le.protobuf.DescriptorProto\0227\n\tenum_type"
-    "\030\004 \003(\0132$.google.protobuf.EnumDescriptorP"
-    "roto\022H\n\017extension_range\030\005 \003(\0132/.google.p"
-    "rotobuf.DescriptorProto.ExtensionRange\0229"
-    "\n\noneof_decl\030\010 \003(\0132%.google.protobuf.One"
-    "ofDescriptorProto\0220\n\007options\030\007 \001(\0132\037.goo"
-    "gle.protobuf.MessageOptions\032,\n\016Extension"
-    "Range\022\r\n\005start\030\001 \001(\005\022\013\n\003end\030\002 \001(\005\"\251\005\n\024Fi"
-    "eldDescriptorProto\022\014\n\004name\030\001 \001(\t\022\016\n\006numb"
-    "er\030\003 \001(\005\022:\n\005label\030\004 \001(\0162+.google.protobu"
-    "f.FieldDescriptorProto.Label\0228\n\004type\030\005 \001"
-    "(\0162*.google.protobuf.FieldDescriptorProt"
-    "o.Type\022\021\n\ttype_name\030\006 \001(\t\022\020\n\010extendee\030\002 "
-    "\001(\t\022\025\n\rdefault_value\030\007 \001(\t\022\023\n\013oneof_inde"
-    "x\030\t \001(\005\022.\n\007options\030\010 \001(\0132\035.google.protob"
-    "uf.FieldOptions\"\266\002\n\004Type\022\017\n\013TYPE_DOUBLE\020"
-    "\001\022\016\n\nTYPE_FLOAT\020\002\022\016\n\nTYPE_INT64\020\003\022\017\n\013TYP"
-    "E_UINT64\020\004\022\016\n\nTYPE_INT32\020\005\022\020\n\014TYPE_FIXED"
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+    "name\030\001 \001(\t\022\022\n\ninput_type\030\002 \001(\t\022\023\n\013output"
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+    "otobuf.MethodOptions\"\253\004\n\013FileOptions\022\024\n\014"
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+    "ode\022\t\n\005SPEED\020\001\022\r\n\tCODE_SIZE\020\002\022\020\n\014LITE_RU"
+    "NTIME\020\003*\t\010\350\007\020\200\200\200\200\002\"\346\001\n\016MessageOptions\022&\n"
+    "\027message_set_wire_format\030\001 \001(\010:\005false\022.\n"
+    "\037no_standard_descriptor_accessor\030\002 \001(\010:\005"
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-    "\030\006 \001(\001\022\024\n\014string_value\030\007 \001(\014\022\027\n\017aggregat"
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-    " \002(\t\022\024\n\014is_extension\030\002 \002(\010\"\261\001\n\016SourceCod"
-    "eInfo\022:\n\010location\030\001 \003(\0132(.google.protobu"
-    "f.SourceCodeInfo.Location\032c\n\010Location\022\020\n"
-    "\004path\030\001 \003(\005B\002\020\001\022\020\n\004span\030\002 \003(\005B\002\020\001\022\030\n\020lea"
-    "ding_comments\030\003 \001(\t\022\031\n\021trailing_comments"
-    "\030\004 \001(\tB)\n\023com.google.protobufB\020Descripto"
-    "rProtosH\001", 4449);
+    "on\"/\n\005CType\022\n\n\006STRING\020\000\022\010\n\004CORD\020\001\022\020\n\014STR"
+    "ING_PIECE\020\002*\t\010\350\007\020\200\200\200\200\002\"\215\001\n\013EnumOptions\022\023"
+    "\n\013allow_alias\030\002 \001(\010\022\031\n\ndeprecated\030\003 \001(\010:"
+    "\005false\022C\n\024uninterpreted_option\030\347\007 \003(\0132$."
+    "google.protobuf.UninterpretedOption*\t\010\350\007"
+    "\020\200\200\200\200\002\"}\n\020EnumValueOptions\022\031\n\ndeprecated"
+    "\030\001 \001(\010:\005false\022C\n\024uninterpreted_option\030\347\007"
+    " \003(\0132$.google.protobuf.UninterpretedOpti"
+    "on*\t\010\350\007\020\200\200\200\200\002\"{\n\016ServiceOptions\022\031\n\ndepre"
+    "cated\030! \001(\010:\005false\022C\n\024uninterpreted_opti"
+    "on\030\347\007 \003(\0132$.google.protobuf.Uninterprete"
+    "dOption*\t\010\350\007\020\200\200\200\200\002\"z\n\rMethodOptions\022\031\n\nd"
+    "eprecated\030! \001(\010:\005false\022C\n\024uninterpreted_"
+    "option\030\347\007 \003(\0132$.google.protobuf.Uninterp"
+    "retedOption*\t\010\350\007\020\200\200\200\200\002\"\236\002\n\023Uninterpreted"
+    "Option\022;\n\004name\030\002 \003(\0132-.google.protobuf.U"
+    "ninterpretedOption.NamePart\022\030\n\020identifie"
+    "r_value\030\003 \001(\t\022\032\n\022positive_int_value\030\004 \001("
+    "\004\022\032\n\022negative_int_value\030\005 \001(\003\022\024\n\014double_"
+    "value\030\006 \001(\001\022\024\n\014string_value\030\007 \001(\014\022\027\n\017agg"
+    "regate_value\030\010 \001(\t\0323\n\010NamePart\022\021\n\tname_p"
+    "art\030\001 \002(\t\022\024\n\014is_extension\030\002 \002(\010\"\261\001\n\016Sour"
+    "ceCodeInfo\022:\n\010location\030\001 \003(\0132(.google.pr"
+    "otobuf.SourceCodeInfo.Location\032c\n\010Locati"
+    "on\022\020\n\004path\030\001 \003(\005B\002\020\001\022\020\n\004span\030\002 \003(\005B\002\020\001\022\030"
+    "\n\020leading_comments\030\003 \001(\t\022\031\n\021trailing_com"
+    "ments\030\004 \001(\tB)\n\023com.google.protobufB\020Desc"
+    "riptorProtosH\001", 4454);
   ::google::protobuf::MessageFactory::InternalRegisterGeneratedFile(
     "google/protobuf/descriptor.proto", &protobuf_RegisterTypes);
   FileDescriptorSet::default_instance_ = new FileDescriptorSet();
@@ -770,16 +792,26 @@ const int FileDescriptorSet::kFileFieldNumber;
 #endif  // !_MSC_VER
 
 FileDescriptorSet::FileDescriptorSet()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.FileDescriptorSet)
 }
 
+FileDescriptorSet::FileDescriptorSet(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena),
+  file_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.FileDescriptorSet)
+}
+
 void FileDescriptorSet::InitAsDefaultInstance() {
 }
 
 FileDescriptorSet::FileDescriptorSet(const FileDescriptorSet& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.FileDescriptorSet)
@@ -796,10 +828,20 @@ FileDescriptorSet::~FileDescriptorSet() {
 }
 
 void FileDescriptorSet::SharedDtor() {
+  if (GetArenaNoVirtual() != NULL) {
+    return;
+  }
+
   if (this != default_instance_) {
   }
 }
 
+void FileDescriptorSet::ArenaDtor(void* object) {
+  FileDescriptorSet* _this = reinterpret_cast< FileDescriptorSet* >(object);
+  (void)_this;
+}
+void FileDescriptorSet::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void FileDescriptorSet::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -817,14 +859,16 @@ const FileDescriptorSet& FileDescriptorSet::default_instance() {
 
 FileDescriptorSet* FileDescriptorSet::default_instance_ = NULL;
 
-FileDescriptorSet* FileDescriptorSet::New() const {
-  return new FileDescriptorSet;
+FileDescriptorSet* FileDescriptorSet::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<FileDescriptorSet>(arena);
 }
 
 void FileDescriptorSet::Clear() {
   file_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool FileDescriptorSet::MergePartialFromCodedStream(
@@ -882,7 +926,7 @@ void FileDescriptorSet::SerializeWithCachedSizes(
       1, this->file(i), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -899,7 +943,7 @@ void FileDescriptorSet::SerializeWithCachedSizes(
         1, this->file(i), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -918,7 +962,7 @@ int FileDescriptorSet::ByteSize() const {
         this->file(i));
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -944,7 +988,9 @@ void FileDescriptorSet::MergeFrom(const ::google::protobuf::Message& from) {
 void FileDescriptorSet::MergeFrom(const FileDescriptorSet& from) {
   GOOGLE_CHECK_NE(&from, this);
   file_.MergeFrom(from.file_);
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void FileDescriptorSet::CopyFrom(const ::google::protobuf::Message& from) {
@@ -966,13 +1012,27 @@ bool FileDescriptorSet::IsInitialized() const {
 }
 
 void FileDescriptorSet::Swap(FileDescriptorSet* other) {
-  if (other != this) {
-    file_.Swap(&other->file_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    FileDescriptorSet temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void FileDescriptorSet::UnsafeArenaSwap(FileDescriptorSet* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void FileDescriptorSet::InternalSwap(FileDescriptorSet* other) {
+  file_.UnsafeArenaSwap(&other->file_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+}
 
 ::google::protobuf::Metadata FileDescriptorSet::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -997,21 +1057,38 @@ const int FileDescriptorProto::kServiceFieldNumber;
 const int FileDescriptorProto::kExtensionFieldNumber;
 const int FileDescriptorProto::kOptionsFieldNumber;
 const int FileDescriptorProto::kSourceCodeInfoFieldNumber;
+const int FileDescriptorProto::kSyntaxFieldNumber;
 #endif  // !_MSC_VER
 
 FileDescriptorProto::FileDescriptorProto()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.FileDescriptorProto)
 }
 
+FileDescriptorProto::FileDescriptorProto(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena),
+  dependency_(arena),
+  public_dependency_(arena),
+  weak_dependency_(arena),
+  message_type_(arena),
+  enum_type_(arena),
+  service_(arena),
+  extension_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.FileDescriptorProto)
+}
+
 void FileDescriptorProto::InitAsDefaultInstance() {
   options_ = const_cast< ::google::protobuf::FileOptions*>(&::google::protobuf::FileOptions::default_instance());
   source_code_info_ = const_cast< ::google::protobuf::SourceCodeInfo*>(&::google::protobuf::SourceCodeInfo::default_instance());
 }
 
 FileDescriptorProto::FileDescriptorProto(const FileDescriptorProto& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.FileDescriptorProto)
@@ -1020,10 +1097,11 @@ FileDescriptorProto::FileDescriptorProto(const FileDescriptorProto& from)
 void FileDescriptorProto::SharedCtor() {
   ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-  package_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  name_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  package_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   options_ = NULL;
   source_code_info_ = NULL;
+  syntax_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
 
@@ -1033,18 +1111,25 @@ FileDescriptorProto::~FileDescriptorProto() {
 }
 
 void FileDescriptorProto::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
-  }
-  if (package_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete package_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
+  name_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+  package_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+  syntax_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   if (this != default_instance_) {
     delete options_;
     delete source_code_info_;
   }
 }
 
+void FileDescriptorProto::ArenaDtor(void* object) {
+  FileDescriptorProto* _this = reinterpret_cast< FileDescriptorProto* >(object);
+  (void)_this;
+}
+void FileDescriptorProto::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void FileDescriptorProto::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -1062,30 +1147,29 @@ const FileDescriptorProto& FileDescriptorProto::default_instance() {
 
 FileDescriptorProto* FileDescriptorProto::default_instance_ = NULL;
 
-FileDescriptorProto* FileDescriptorProto::New() const {
-  return new FileDescriptorProto;
+FileDescriptorProto* FileDescriptorProto::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<FileDescriptorProto>(arena);
 }
 
 void FileDescriptorProto::Clear() {
   if (_has_bits_[0 / 32] & 3) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        name_->clear();
-      }
+      name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     if (has_package()) {
-      if (package_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        package_->clear();
-      }
+      package_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
   }
-  if (_has_bits_[8 / 32] & 1536) {
+  if (_has_bits_[8 / 32] & 3584) {
     if (has_options()) {
       if (options_ != NULL) options_->::google::protobuf::FileOptions::Clear();
     }
     if (has_source_code_info()) {
       if (source_code_info_ != NULL) source_code_info_->::google::protobuf::SourceCodeInfo::Clear();
     }
+    if (has_syntax()) {
+      syntax_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+    }
   }
   dependency_.Clear();
   public_dependency_.Clear();
@@ -1095,7 +1179,9 @@ void FileDescriptorProto::Clear() {
   service_.Clear();
   extension_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool FileDescriptorProto::MergePartialFromCodedStream(
@@ -1116,7 +1202,7 @@ bool FileDescriptorProto::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->name().data(), this->name().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "name");
+            "google.protobuf.FileDescriptorProto.name");
         } else {
           goto handle_unusual;
         }
@@ -1133,7 +1219,7 @@ bool FileDescriptorProto::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->package().data(), this->package().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "package");
+            "google.protobuf.FileDescriptorProto.package");
         } else {
           goto handle_unusual;
         }
@@ -1151,7 +1237,7 @@ bool FileDescriptorProto::MergePartialFromCodedStream(
             this->dependency(this->dependency_size() - 1).data(),
             this->dependency(this->dependency_size() - 1).length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "dependency");
+            "google.protobuf.FileDescriptorProto.dependency");
         } else {
           goto handle_unusual;
         }
@@ -1276,6 +1362,23 @@ bool FileDescriptorProto::MergePartialFromCodedStream(
           goto handle_unusual;
         }
         if (input->ExpectTag(88)) goto parse_weak_dependency;
+        if (input->ExpectTag(98)) goto parse_syntax;
+        break;
+      }
+
+      // optional string syntax = 12;
+      case 12: {
+        if (tag == 98) {
+         parse_syntax:
+          DO_(::google::protobuf::internal::WireFormatLite::ReadString(
+                input, this->mutable_syntax()));
+          ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
+            this->syntax().data(), this->syntax().length(),
+            ::google::protobuf::internal::WireFormat::PARSE,
+            "google.protobuf.FileDescriptorProto.syntax");
+        } else {
+          goto handle_unusual;
+        }
         if (input->ExpectAtEnd()) goto success;
         break;
       }
@@ -1310,7 +1413,7 @@ void FileDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.FileDescriptorProto.name");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       1, this->name(), output);
   }
@@ -1320,7 +1423,7 @@ void FileDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->package().data(), this->package().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "package");
+      "google.protobuf.FileDescriptorProto.package");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       2, this->package(), output);
   }
@@ -1330,7 +1433,7 @@ void FileDescriptorProto::SerializeWithCachedSizes(
   ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
     this->dependency(i).data(), this->dependency(i).length(),
     ::google::protobuf::internal::WireFormat::SERIALIZE,
-    "dependency");
+    "google.protobuf.FileDescriptorProto.dependency");
     ::google::protobuf::internal::WireFormatLite::WriteString(
       3, this->dependency(i), output);
   }
@@ -1383,7 +1486,17 @@ void FileDescriptorProto::SerializeWithCachedSizes(
       11, this->weak_dependency(i), output);
   }
 
-  if (!unknown_fields().empty()) {
+  // optional string syntax = 12;
+  if (has_syntax()) {
+    ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
+      this->syntax().data(), this->syntax().length(),
+      ::google::protobuf::internal::WireFormat::SERIALIZE,
+      "google.protobuf.FileDescriptorProto.syntax");
+    ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
+      12, this->syntax(), output);
+  }
+
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -1398,7 +1511,7 @@ void FileDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.FileDescriptorProto.name");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         1, this->name(), target);
@@ -1409,7 +1522,7 @@ void FileDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->package().data(), this->package().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "package");
+      "google.protobuf.FileDescriptorProto.package");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         2, this->package(), target);
@@ -1420,7 +1533,7 @@ void FileDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->dependency(i).data(), this->dependency(i).length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "dependency");
+      "google.protobuf.FileDescriptorProto.dependency");
     target = ::google::protobuf::internal::WireFormatLite::
       WriteStringToArray(3, this->dependency(i), target);
   }
@@ -1479,7 +1592,18 @@ void FileDescriptorProto::SerializeWithCachedSizes(
       WriteInt32ToArray(11, this->weak_dependency(i), target);
   }
 
-  if (!unknown_fields().empty()) {
+  // optional string syntax = 12;
+  if (has_syntax()) {
+    ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
+      this->syntax().data(), this->syntax().length(),
+      ::google::protobuf::internal::WireFormat::SERIALIZE,
+      "google.protobuf.FileDescriptorProto.syntax");
+    target =
+      ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
+        12, this->syntax(), target);
+  }
+
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -1490,7 +1614,7 @@ void FileDescriptorProto::SerializeWithCachedSizes(
 int FileDescriptorProto::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
+  if (_has_bits_[0 / 32] & 3) {
     // optional string name = 1;
     if (has_name()) {
       total_size += 1 +
@@ -1506,7 +1630,7 @@ int FileDescriptorProto::ByteSize() const {
     }
 
   }
-  if (_has_bits_[9 / 32] & (0xffu << (9 % 32))) {
+  if (_has_bits_[9 / 32] & 3584) {
     // optional .google.protobuf.FileOptions options = 8;
     if (has_options()) {
       total_size += 1 +
@@ -1521,6 +1645,13 @@ int FileDescriptorProto::ByteSize() const {
           this->source_code_info());
     }
 
+    // optional string syntax = 12;
+    if (has_syntax()) {
+      total_size += 1 +
+        ::google::protobuf::internal::WireFormatLite::StringSize(
+          this->syntax());
+    }
+
   }
   // repeated string dependency = 3;
   total_size += 1 * this->dependency_size();
@@ -1581,7 +1712,7 @@ int FileDescriptorProto::ByteSize() const {
         this->extension(i));
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -1628,8 +1759,13 @@ void FileDescriptorProto::MergeFrom(const FileDescriptorProto& from) {
     if (from.has_source_code_info()) {
       mutable_source_code_info()->::google::protobuf::SourceCodeInfo::MergeFrom(from.source_code_info());
     }
+    if (from.has_syntax()) {
+      set_syntax(from.syntax());
+    }
+  }
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
   }
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
 }
 
 void FileDescriptorProto::CopyFrom(const ::google::protobuf::Message& from) {
@@ -1657,22 +1793,37 @@ bool FileDescriptorProto::IsInitialized() const {
 }
 
 void FileDescriptorProto::Swap(FileDescriptorProto* other) {
-  if (other != this) {
-    std::swap(name_, other->name_);
-    std::swap(package_, other->package_);
-    dependency_.Swap(&other->dependency_);
-    public_dependency_.Swap(&other->public_dependency_);
-    weak_dependency_.Swap(&other->weak_dependency_);
-    message_type_.Swap(&other->message_type_);
-    enum_type_.Swap(&other->enum_type_);
-    service_.Swap(&other->service_);
-    extension_.Swap(&other->extension_);
-    std::swap(options_, other->options_);
-    std::swap(source_code_info_, other->source_code_info_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
-  }
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    FileDescriptorProto temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
+  }
+}
+void FileDescriptorProto::UnsafeArenaSwap(FileDescriptorProto* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void FileDescriptorProto::InternalSwap(FileDescriptorProto* other) {
+  name_.Swap(&other->name_);
+  package_.Swap(&other->package_);
+  dependency_.UnsafeArenaSwap(&other->dependency_);
+  public_dependency_.UnsafeArenaSwap(&other->public_dependency_);
+  weak_dependency_.UnsafeArenaSwap(&other->weak_dependency_);
+  message_type_.UnsafeArenaSwap(&other->message_type_);
+  enum_type_.UnsafeArenaSwap(&other->enum_type_);
+  service_.UnsafeArenaSwap(&other->service_);
+  extension_.UnsafeArenaSwap(&other->extension_);
+  std::swap(options_, other->options_);
+  std::swap(source_code_info_, other->source_code_info_);
+  syntax_.Swap(&other->syntax_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
 }
 
 ::google::protobuf::Metadata FileDescriptorProto::GetMetadata() const {
@@ -1692,16 +1843,25 @@ const int DescriptorProto_ExtensionRange::kEndFieldNumber;
 #endif  // !_MSC_VER
 
 DescriptorProto_ExtensionRange::DescriptorProto_ExtensionRange()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.DescriptorProto.ExtensionRange)
 }
 
+DescriptorProto_ExtensionRange::DescriptorProto_ExtensionRange(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.DescriptorProto.ExtensionRange)
+}
+
 void DescriptorProto_ExtensionRange::InitAsDefaultInstance() {
 }
 
 DescriptorProto_ExtensionRange::DescriptorProto_ExtensionRange(const DescriptorProto_ExtensionRange& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.DescriptorProto.ExtensionRange)
@@ -1720,10 +1880,20 @@ DescriptorProto_ExtensionRange::~DescriptorProto_ExtensionRange() {
 }
 
 void DescriptorProto_ExtensionRange::SharedDtor() {
+  if (GetArenaNoVirtual() != NULL) {
+    return;
+  }
+
   if (this != default_instance_) {
   }
 }
 
+void DescriptorProto_ExtensionRange::ArenaDtor(void* object) {
+  DescriptorProto_ExtensionRange* _this = reinterpret_cast< DescriptorProto_ExtensionRange* >(object);
+  (void)_this;
+}
+void DescriptorProto_ExtensionRange::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void DescriptorProto_ExtensionRange::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -1741,8 +1911,8 @@ const DescriptorProto_ExtensionRange& DescriptorProto_ExtensionRange::default_in
 
 DescriptorProto_ExtensionRange* DescriptorProto_ExtensionRange::default_instance_ = NULL;
 
-DescriptorProto_ExtensionRange* DescriptorProto_ExtensionRange::New() const {
-  return new DescriptorProto_ExtensionRange;
+DescriptorProto_ExtensionRange* DescriptorProto_ExtensionRange::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<DescriptorProto_ExtensionRange>(arena);
 }
 
 void DescriptorProto_ExtensionRange::Clear() {
@@ -1762,7 +1932,9 @@ void DescriptorProto_ExtensionRange::Clear() {
 #undef ZR_
 
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool DescriptorProto_ExtensionRange::MergePartialFromCodedStream(
@@ -1839,7 +2011,7 @@ void DescriptorProto_ExtensionRange::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormatLite::WriteInt32(2, this->end(), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -1859,7 +2031,7 @@ void DescriptorProto_ExtensionRange::SerializeWithCachedSizes(
     target = ::google::protobuf::internal::WireFormatLite::WriteInt32ToArray(2, this->end(), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -1870,7 +2042,7 @@ void DescriptorProto_ExtensionRange::SerializeWithCachedSizes(
 int DescriptorProto_ExtensionRange::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
+  if (_has_bits_[0 / 32] & 3) {
     // optional int32 start = 1;
     if (has_start()) {
       total_size += 1 +
@@ -1886,7 +2058,7 @@ int DescriptorProto_ExtensionRange::ByteSize() const {
     }
 
   }
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -1919,7 +2091,9 @@ void DescriptorProto_ExtensionRange::MergeFrom(const DescriptorProto_ExtensionRa
       set_end(from.end());
     }
   }
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void DescriptorProto_ExtensionRange::CopyFrom(const ::google::protobuf::Message& from) {
@@ -1940,14 +2114,28 @@ bool DescriptorProto_ExtensionRange::IsInitialized() const {
 }
 
 void DescriptorProto_ExtensionRange::Swap(DescriptorProto_ExtensionRange* other) {
-  if (other != this) {
-    std::swap(start_, other->start_);
-    std::swap(end_, other->end_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    DescriptorProto_ExtensionRange temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void DescriptorProto_ExtensionRange::UnsafeArenaSwap(DescriptorProto_ExtensionRange* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void DescriptorProto_ExtensionRange::InternalSwap(DescriptorProto_ExtensionRange* other) {
+  std::swap(start_, other->start_);
+  std::swap(end_, other->end_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+}
 
 ::google::protobuf::Metadata DescriptorProto_ExtensionRange::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -1972,17 +2160,32 @@ const int DescriptorProto::kOptionsFieldNumber;
 #endif  // !_MSC_VER
 
 DescriptorProto::DescriptorProto()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.DescriptorProto)
 }
 
+DescriptorProto::DescriptorProto(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena),
+  field_(arena),
+  extension_(arena),
+  nested_type_(arena),
+  enum_type_(arena),
+  extension_range_(arena),
+  oneof_decl_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.DescriptorProto)
+}
+
 void DescriptorProto::InitAsDefaultInstance() {
   options_ = const_cast< ::google::protobuf::MessageOptions*>(&::google::protobuf::MessageOptions::default_instance());
 }
 
 DescriptorProto::DescriptorProto(const DescriptorProto& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.DescriptorProto)
@@ -1991,7 +2194,7 @@ DescriptorProto::DescriptorProto(const DescriptorProto& from)
 void DescriptorProto::SharedCtor() {
   ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  name_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   options_ = NULL;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
@@ -2002,14 +2205,22 @@ DescriptorProto::~DescriptorProto() {
 }
 
 void DescriptorProto::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
+  name_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   if (this != default_instance_) {
     delete options_;
   }
 }
 
+void DescriptorProto::ArenaDtor(void* object) {
+  DescriptorProto* _this = reinterpret_cast< DescriptorProto* >(object);
+  (void)_this;
+}
+void DescriptorProto::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void DescriptorProto::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -2027,16 +2238,14 @@ const DescriptorProto& DescriptorProto::default_instance() {
 
 DescriptorProto* DescriptorProto::default_instance_ = NULL;
 
-DescriptorProto* DescriptorProto::New() const {
-  return new DescriptorProto;
+DescriptorProto* DescriptorProto::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<DescriptorProto>(arena);
 }
 
 void DescriptorProto::Clear() {
   if (_has_bits_[0 / 32] & 129) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        name_->clear();
-      }
+      name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     if (has_options()) {
       if (options_ != NULL) options_->::google::protobuf::MessageOptions::Clear();
@@ -2049,7 +2258,9 @@ void DescriptorProto::Clear() {
   extension_range_.Clear();
   oneof_decl_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool DescriptorProto::MergePartialFromCodedStream(
@@ -2070,7 +2281,7 @@ bool DescriptorProto::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->name().data(), this->name().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "name");
+            "google.protobuf.DescriptorProto.name");
         } else {
           goto handle_unusual;
         }
@@ -2205,7 +2416,7 @@ void DescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.DescriptorProto.name");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       1, this->name(), output);
   }
@@ -2252,7 +2463,7 @@ void DescriptorProto::SerializeWithCachedSizes(
       8, this->oneof_decl(i), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -2267,7 +2478,7 @@ void DescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.DescriptorProto.name");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         1, this->name(), target);
@@ -2322,7 +2533,7 @@ void DescriptorProto::SerializeWithCachedSizes(
         8, this->oneof_decl(i), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -2333,7 +2544,7 @@ void DescriptorProto::SerializeWithCachedSizes(
 int DescriptorProto::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
+  if (_has_bits_[0 / 32] & 129) {
     // optional string name = 1;
     if (has_name()) {
       total_size += 1 +
@@ -2397,7 +2608,7 @@ int DescriptorProto::ByteSize() const {
         this->oneof_decl(i));
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -2436,7 +2647,9 @@ void DescriptorProto::MergeFrom(const DescriptorProto& from) {
       mutable_options()->::google::protobuf::MessageOptions::MergeFrom(from.options());
     }
   }
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void DescriptorProto::CopyFrom(const ::google::protobuf::Message& from) {
@@ -2464,19 +2677,33 @@ bool DescriptorProto::IsInitialized() const {
 }
 
 void DescriptorProto::Swap(DescriptorProto* other) {
-  if (other != this) {
-    std::swap(name_, other->name_);
-    field_.Swap(&other->field_);
-    extension_.Swap(&other->extension_);
-    nested_type_.Swap(&other->nested_type_);
-    enum_type_.Swap(&other->enum_type_);
-    extension_range_.Swap(&other->extension_range_);
-    oneof_decl_.Swap(&other->oneof_decl_);
-    std::swap(options_, other->options_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
-  }
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    DescriptorProto temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
+  }
+}
+void DescriptorProto::UnsafeArenaSwap(DescriptorProto* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void DescriptorProto::InternalSwap(DescriptorProto* other) {
+  name_.Swap(&other->name_);
+  field_.UnsafeArenaSwap(&other->field_);
+  extension_.UnsafeArenaSwap(&other->extension_);
+  nested_type_.UnsafeArenaSwap(&other->nested_type_);
+  enum_type_.UnsafeArenaSwap(&other->enum_type_);
+  extension_range_.UnsafeArenaSwap(&other->extension_range_);
+  oneof_decl_.UnsafeArenaSwap(&other->oneof_decl_);
+  std::swap(options_, other->options_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
 }
 
 ::google::protobuf::Metadata DescriptorProto::GetMetadata() const {
@@ -2579,17 +2806,26 @@ const int FieldDescriptorProto::kOptionsFieldNumber;
 #endif  // !_MSC_VER
 
 FieldDescriptorProto::FieldDescriptorProto()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.FieldDescriptorProto)
 }
 
+FieldDescriptorProto::FieldDescriptorProto(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.FieldDescriptorProto)
+}
+
 void FieldDescriptorProto::InitAsDefaultInstance() {
   options_ = const_cast< ::google::protobuf::FieldOptions*>(&::google::protobuf::FieldOptions::default_instance());
 }
 
 FieldDescriptorProto::FieldDescriptorProto(const FieldDescriptorProto& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.FieldDescriptorProto)
@@ -2598,13 +2834,13 @@ FieldDescriptorProto::FieldDescriptorProto(const FieldDescriptorProto& from)
 void FieldDescriptorProto::SharedCtor() {
   ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  name_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   number_ = 0;
   label_ = 1;
   type_ = 1;
-  type_name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-  extendee_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-  default_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  type_name_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  extendee_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  default_value_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   oneof_index_ = 0;
   options_ = NULL;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
@@ -2616,23 +2852,25 @@ FieldDescriptorProto::~FieldDescriptorProto() {
 }
 
 void FieldDescriptorProto::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
-  }
-  if (type_name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete type_name_;
-  }
-  if (extendee_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete extendee_;
-  }
-  if (default_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete default_value_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
+  name_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+  type_name_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+  extendee_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+  default_value_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   if (this != default_instance_) {
     delete options_;
   }
 }
 
+void FieldDescriptorProto::ArenaDtor(void* object) {
+  FieldDescriptorProto* _this = reinterpret_cast< FieldDescriptorProto* >(object);
+  (void)_this;
+}
+void FieldDescriptorProto::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void FieldDescriptorProto::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -2650,34 +2888,26 @@ const FieldDescriptorProto& FieldDescriptorProto::default_instance() {
 
 FieldDescriptorProto* FieldDescriptorProto::default_instance_ = NULL;
 
-FieldDescriptorProto* FieldDescriptorProto::New() const {
-  return new FieldDescriptorProto;
+FieldDescriptorProto* FieldDescriptorProto::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<FieldDescriptorProto>(arena);
 }
 
 void FieldDescriptorProto::Clear() {
   if (_has_bits_[0 / 32] & 255) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        name_->clear();
-      }
+      name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     number_ = 0;
     label_ = 1;
     type_ = 1;
     if (has_type_name()) {
-      if (type_name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        type_name_->clear();
-      }
+      type_name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     if (has_extendee()) {
-      if (extendee_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        extendee_->clear();
-      }
+      extendee_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     if (has_default_value()) {
-      if (default_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        default_value_->clear();
-      }
+      default_value_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     oneof_index_ = 0;
   }
@@ -2685,7 +2915,9 @@ void FieldDescriptorProto::Clear() {
     if (options_ != NULL) options_->::google::protobuf::FieldOptions::Clear();
   }
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool FieldDescriptorProto::MergePartialFromCodedStream(
@@ -2706,7 +2938,7 @@ bool FieldDescriptorProto::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->name().data(), this->name().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "name");
+            "google.protobuf.FieldDescriptorProto.name");
         } else {
           goto handle_unusual;
         }
@@ -2723,7 +2955,7 @@ bool FieldDescriptorProto::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->extendee().data(), this->extendee().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "extendee");
+            "google.protobuf.FieldDescriptorProto.extendee");
         } else {
           goto handle_unusual;
         }
@@ -2795,7 +3027,7 @@ bool FieldDescriptorProto::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->type_name().data(), this->type_name().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "type_name");
+            "google.protobuf.FieldDescriptorProto.type_name");
         } else {
           goto handle_unusual;
         }
@@ -2812,7 +3044,7 @@ bool FieldDescriptorProto::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->default_value().data(), this->default_value().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "default_value");
+            "google.protobuf.FieldDescriptorProto.default_value");
         } else {
           goto handle_unusual;
         }
@@ -2878,7 +3110,7 @@ void FieldDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.FieldDescriptorProto.name");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       1, this->name(), output);
   }
@@ -2888,7 +3120,7 @@ void FieldDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->extendee().data(), this->extendee().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "extendee");
+      "google.protobuf.FieldDescriptorProto.extendee");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       2, this->extendee(), output);
   }
@@ -2915,7 +3147,7 @@ void FieldDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->type_name().data(), this->type_name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "type_name");
+      "google.protobuf.FieldDescriptorProto.type_name");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       6, this->type_name(), output);
   }
@@ -2925,7 +3157,7 @@ void FieldDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->default_value().data(), this->default_value().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "default_value");
+      "google.protobuf.FieldDescriptorProto.default_value");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       7, this->default_value(), output);
   }
@@ -2941,7 +3173,7 @@ void FieldDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormatLite::WriteInt32(9, this->oneof_index(), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -2956,7 +3188,7 @@ void FieldDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.FieldDescriptorProto.name");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         1, this->name(), target);
@@ -2967,7 +3199,7 @@ void FieldDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->extendee().data(), this->extendee().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "extendee");
+      "google.protobuf.FieldDescriptorProto.extendee");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         2, this->extendee(), target);
@@ -2995,7 +3227,7 @@ void FieldDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->type_name().data(), this->type_name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "type_name");
+      "google.protobuf.FieldDescriptorProto.type_name");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         6, this->type_name(), target);
@@ -3006,7 +3238,7 @@ void FieldDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->default_value().data(), this->default_value().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "default_value");
+      "google.protobuf.FieldDescriptorProto.default_value");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         7, this->default_value(), target);
@@ -3024,7 +3256,7 @@ void FieldDescriptorProto::SerializeWithCachedSizes(
     target = ::google::protobuf::internal::WireFormatLite::WriteInt32ToArray(9, this->oneof_index(), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -3035,7 +3267,7 @@ void FieldDescriptorProto::SerializeWithCachedSizes(
 int FieldDescriptorProto::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
+  if (_has_bits_[0 / 32] & 255) {
     // optional string name = 1;
     if (has_name()) {
       total_size += 1 +
@@ -3091,16 +3323,14 @@ int FieldDescriptorProto::ByteSize() const {
     }
 
   }
-  if (_has_bits_[8 / 32] & (0xffu << (8 % 32))) {
-    // optional .google.protobuf.FieldOptions options = 8;
-    if (has_options()) {
-      total_size += 1 +
-        ::google::protobuf::internal::WireFormatLite::MessageSizeNoVirtual(
-          this->options());
-    }
-
+  // optional .google.protobuf.FieldOptions options = 8;
+  if (has_options()) {
+    total_size += 1 +
+      ::google::protobuf::internal::WireFormatLite::MessageSizeNoVirtual(
+        this->options());
   }
-  if (!unknown_fields().empty()) {
+
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -3156,7 +3386,9 @@ void FieldDescriptorProto::MergeFrom(const FieldDescriptorProto& from) {
       mutable_options()->::google::protobuf::FieldOptions::MergeFrom(from.options());
     }
   }
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void FieldDescriptorProto::CopyFrom(const ::google::protobuf::Message& from) {
@@ -3180,20 +3412,34 @@ bool FieldDescriptorProto::IsInitialized() const {
 }
 
 void FieldDescriptorProto::Swap(FieldDescriptorProto* other) {
-  if (other != this) {
-    std::swap(name_, other->name_);
-    std::swap(number_, other->number_);
-    std::swap(label_, other->label_);
-    std::swap(type_, other->type_);
-    std::swap(type_name_, other->type_name_);
-    std::swap(extendee_, other->extendee_);
-    std::swap(default_value_, other->default_value_);
-    std::swap(oneof_index_, other->oneof_index_);
-    std::swap(options_, other->options_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
-  }
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    FieldDescriptorProto temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
+  }
+}
+void FieldDescriptorProto::UnsafeArenaSwap(FieldDescriptorProto* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void FieldDescriptorProto::InternalSwap(FieldDescriptorProto* other) {
+  name_.Swap(&other->name_);
+  std::swap(number_, other->number_);
+  std::swap(label_, other->label_);
+  std::swap(type_, other->type_);
+  type_name_.Swap(&other->type_name_);
+  extendee_.Swap(&other->extendee_);
+  default_value_.Swap(&other->default_value_);
+  std::swap(oneof_index_, other->oneof_index_);
+  std::swap(options_, other->options_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
 }
 
 ::google::protobuf::Metadata FieldDescriptorProto::GetMetadata() const {
@@ -3212,16 +3458,25 @@ const int OneofDescriptorProto::kNameFieldNumber;
 #endif  // !_MSC_VER
 
 OneofDescriptorProto::OneofDescriptorProto()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.OneofDescriptorProto)
 }
 
+OneofDescriptorProto::OneofDescriptorProto(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.OneofDescriptorProto)
+}
+
 void OneofDescriptorProto::InitAsDefaultInstance() {
 }
 
 OneofDescriptorProto::OneofDescriptorProto(const OneofDescriptorProto& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.OneofDescriptorProto)
@@ -3230,7 +3485,7 @@ OneofDescriptorProto::OneofDescriptorProto(const OneofDescriptorProto& from)
 void OneofDescriptorProto::SharedCtor() {
   ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  name_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
 
@@ -3240,13 +3495,21 @@ OneofDescriptorProto::~OneofDescriptorProto() {
 }
 
 void OneofDescriptorProto::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
+  name_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   if (this != default_instance_) {
   }
 }
 
+void OneofDescriptorProto::ArenaDtor(void* object) {
+  OneofDescriptorProto* _this = reinterpret_cast< OneofDescriptorProto* >(object);
+  (void)_this;
+}
+void OneofDescriptorProto::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void OneofDescriptorProto::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -3264,18 +3527,18 @@ const OneofDescriptorProto& OneofDescriptorProto::default_instance() {
 
 OneofDescriptorProto* OneofDescriptorProto::default_instance_ = NULL;
 
-OneofDescriptorProto* OneofDescriptorProto::New() const {
-  return new OneofDescriptorProto;
+OneofDescriptorProto* OneofDescriptorProto::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<OneofDescriptorProto>(arena);
 }
 
 void OneofDescriptorProto::Clear() {
   if (has_name()) {
-    if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-      name_->clear();
-    }
+    name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   }
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool OneofDescriptorProto::MergePartialFromCodedStream(
@@ -3296,7 +3559,7 @@ bool OneofDescriptorProto::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->name().data(), this->name().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "name");
+            "google.protobuf.OneofDescriptorProto.name");
         } else {
           goto handle_unusual;
         }
@@ -3334,12 +3597,12 @@ void OneofDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.OneofDescriptorProto.name");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       1, this->name(), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -3354,13 +3617,13 @@ void OneofDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.OneofDescriptorProto.name");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         1, this->name(), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -3371,16 +3634,14 @@ void OneofDescriptorProto::SerializeWithCachedSizes(
 int OneofDescriptorProto::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
-    // optional string name = 1;
-    if (has_name()) {
-      total_size += 1 +
-        ::google::protobuf::internal::WireFormatLite::StringSize(
-          this->name());
-    }
-
+  // optional string name = 1;
+  if (has_name()) {
+    total_size += 1 +
+      ::google::protobuf::internal::WireFormatLite::StringSize(
+        this->name());
   }
-  if (!unknown_fields().empty()) {
+
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -3410,7 +3671,9 @@ void OneofDescriptorProto::MergeFrom(const OneofDescriptorProto& from) {
       set_name(from.name());
     }
   }
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void OneofDescriptorProto::CopyFrom(const ::google::protobuf::Message& from) {
@@ -3431,13 +3694,27 @@ bool OneofDescriptorProto::IsInitialized() const {
 }
 
 void OneofDescriptorProto::Swap(OneofDescriptorProto* other) {
-  if (other != this) {
-    std::swap(name_, other->name_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    OneofDescriptorProto temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void OneofDescriptorProto::UnsafeArenaSwap(OneofDescriptorProto* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void OneofDescriptorProto::InternalSwap(OneofDescriptorProto* other) {
+  name_.Swap(&other->name_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+}
 
 ::google::protobuf::Metadata OneofDescriptorProto::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -3457,17 +3734,27 @@ const int EnumDescriptorProto::kOptionsFieldNumber;
 #endif  // !_MSC_VER
 
 EnumDescriptorProto::EnumDescriptorProto()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.EnumDescriptorProto)
 }
 
+EnumDescriptorProto::EnumDescriptorProto(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena),
+  value_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.EnumDescriptorProto)
+}
+
 void EnumDescriptorProto::InitAsDefaultInstance() {
   options_ = const_cast< ::google::protobuf::EnumOptions*>(&::google::protobuf::EnumOptions::default_instance());
 }
 
 EnumDescriptorProto::EnumDescriptorProto(const EnumDescriptorProto& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.EnumDescriptorProto)
@@ -3476,7 +3763,7 @@ EnumDescriptorProto::EnumDescriptorProto(const EnumDescriptorProto& from)
 void EnumDescriptorProto::SharedCtor() {
   ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  name_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   options_ = NULL;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
@@ -3487,14 +3774,22 @@ EnumDescriptorProto::~EnumDescriptorProto() {
 }
 
 void EnumDescriptorProto::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
+  name_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   if (this != default_instance_) {
     delete options_;
   }
 }
 
+void EnumDescriptorProto::ArenaDtor(void* object) {
+  EnumDescriptorProto* _this = reinterpret_cast< EnumDescriptorProto* >(object);
+  (void)_this;
+}
+void EnumDescriptorProto::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void EnumDescriptorProto::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -3512,16 +3807,14 @@ const EnumDescriptorProto& EnumDescriptorProto::default_instance() {
 
 EnumDescriptorProto* EnumDescriptorProto::default_instance_ = NULL;
 
-EnumDescriptorProto* EnumDescriptorProto::New() const {
-  return new EnumDescriptorProto;
+EnumDescriptorProto* EnumDescriptorProto::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<EnumDescriptorProto>(arena);
 }
 
 void EnumDescriptorProto::Clear() {
   if (_has_bits_[0 / 32] & 5) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        name_->clear();
-      }
+      name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     if (has_options()) {
       if (options_ != NULL) options_->::google::protobuf::EnumOptions::Clear();
@@ -3529,7 +3822,9 @@ void EnumDescriptorProto::Clear() {
   }
   value_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool EnumDescriptorProto::MergePartialFromCodedStream(
@@ -3550,7 +3845,7 @@ bool EnumDescriptorProto::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->name().data(), this->name().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "name");
+            "google.protobuf.EnumDescriptorProto.name");
         } else {
           goto handle_unusual;
         }
@@ -3615,7 +3910,7 @@ void EnumDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.EnumDescriptorProto.name");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       1, this->name(), output);
   }
@@ -3632,7 +3927,7 @@ void EnumDescriptorProto::SerializeWithCachedSizes(
       3, this->options(), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -3647,7 +3942,7 @@ void EnumDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.EnumDescriptorProto.name");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         1, this->name(), target);
@@ -3667,7 +3962,7 @@ void EnumDescriptorProto::SerializeWithCachedSizes(
         3, this->options(), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -3678,7 +3973,7 @@ void EnumDescriptorProto::SerializeWithCachedSizes(
 int EnumDescriptorProto::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
+  if (_has_bits_[0 / 32] & 5) {
     // optional string name = 1;
     if (has_name()) {
       total_size += 1 +
@@ -3702,7 +3997,7 @@ int EnumDescriptorProto::ByteSize() const {
         this->value(i));
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -3736,7 +4031,9 @@ void EnumDescriptorProto::MergeFrom(const EnumDescriptorProto& from) {
       mutable_options()->::google::protobuf::EnumOptions::MergeFrom(from.options());
     }
   }
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void EnumDescriptorProto::CopyFrom(const ::google::protobuf::Message& from) {
@@ -3761,15 +4058,29 @@ bool EnumDescriptorProto::IsInitialized() const {
 }
 
 void EnumDescriptorProto::Swap(EnumDescriptorProto* other) {
-  if (other != this) {
-    std::swap(name_, other->name_);
-    value_.Swap(&other->value_);
-    std::swap(options_, other->options_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    EnumDescriptorProto temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void EnumDescriptorProto::UnsafeArenaSwap(EnumDescriptorProto* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void EnumDescriptorProto::InternalSwap(EnumDescriptorProto* other) {
+  name_.Swap(&other->name_);
+  value_.UnsafeArenaSwap(&other->value_);
+  std::swap(options_, other->options_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+}
 
 ::google::protobuf::Metadata EnumDescriptorProto::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -3789,17 +4100,26 @@ const int EnumValueDescriptorProto::kOptionsFieldNumber;
 #endif  // !_MSC_VER
 
 EnumValueDescriptorProto::EnumValueDescriptorProto()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.EnumValueDescriptorProto)
 }
 
+EnumValueDescriptorProto::EnumValueDescriptorProto(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.EnumValueDescriptorProto)
+}
+
 void EnumValueDescriptorProto::InitAsDefaultInstance() {
   options_ = const_cast< ::google::protobuf::EnumValueOptions*>(&::google::protobuf::EnumValueOptions::default_instance());
 }
 
 EnumValueDescriptorProto::EnumValueDescriptorProto(const EnumValueDescriptorProto& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.EnumValueDescriptorProto)
@@ -3808,7 +4128,7 @@ EnumValueDescriptorProto::EnumValueDescriptorProto(const EnumValueDescriptorProt
 void EnumValueDescriptorProto::SharedCtor() {
   ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  name_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   number_ = 0;
   options_ = NULL;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
@@ -3820,14 +4140,22 @@ EnumValueDescriptorProto::~EnumValueDescriptorProto() {
 }
 
 void EnumValueDescriptorProto::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
+  name_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   if (this != default_instance_) {
     delete options_;
   }
 }
 
+void EnumValueDescriptorProto::ArenaDtor(void* object) {
+  EnumValueDescriptorProto* _this = reinterpret_cast< EnumValueDescriptorProto* >(object);
+  (void)_this;
+}
+void EnumValueDescriptorProto::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void EnumValueDescriptorProto::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -3845,16 +4173,14 @@ const EnumValueDescriptorProto& EnumValueDescriptorProto::default_instance() {
 
 EnumValueDescriptorProto* EnumValueDescriptorProto::default_instance_ = NULL;
 
-EnumValueDescriptorProto* EnumValueDescriptorProto::New() const {
-  return new EnumValueDescriptorProto;
+EnumValueDescriptorProto* EnumValueDescriptorProto::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<EnumValueDescriptorProto>(arena);
 }
 
 void EnumValueDescriptorProto::Clear() {
   if (_has_bits_[0 / 32] & 7) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        name_->clear();
-      }
+      name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     number_ = 0;
     if (has_options()) {
@@ -3862,7 +4188,9 @@ void EnumValueDescriptorProto::Clear() {
     }
   }
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool EnumValueDescriptorProto::MergePartialFromCodedStream(
@@ -3883,7 +4211,7 @@ bool EnumValueDescriptorProto::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->name().data(), this->name().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "name");
+            "google.protobuf.EnumValueDescriptorProto.name");
         } else {
           goto handle_unusual;
         }
@@ -3949,7 +4277,7 @@ void EnumValueDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.EnumValueDescriptorProto.name");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       1, this->name(), output);
   }
@@ -3965,7 +4293,7 @@ void EnumValueDescriptorProto::SerializeWithCachedSizes(
       3, this->options(), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -3980,7 +4308,7 @@ void EnumValueDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.EnumValueDescriptorProto.name");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         1, this->name(), target);
@@ -3998,7 +4326,7 @@ void EnumValueDescriptorProto::SerializeWithCachedSizes(
         3, this->options(), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -4009,7 +4337,7 @@ void EnumValueDescriptorProto::SerializeWithCachedSizes(
 int EnumValueDescriptorProto::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
+  if (_has_bits_[0 / 32] & 7) {
     // optional string name = 1;
     if (has_name()) {
       total_size += 1 +
@@ -4032,7 +4360,7 @@ int EnumValueDescriptorProto::ByteSize() const {
     }
 
   }
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -4068,7 +4396,9 @@ void EnumValueDescriptorProto::MergeFrom(const EnumValueDescriptorProto& from) {
       mutable_options()->::google::protobuf::EnumValueOptions::MergeFrom(from.options());
     }
   }
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void EnumValueDescriptorProto::CopyFrom(const ::google::protobuf::Message& from) {
@@ -4092,15 +4422,29 @@ bool EnumValueDescriptorProto::IsInitialized() const {
 }
 
 void EnumValueDescriptorProto::Swap(EnumValueDescriptorProto* other) {
-  if (other != this) {
-    std::swap(name_, other->name_);
-    std::swap(number_, other->number_);
-    std::swap(options_, other->options_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    EnumValueDescriptorProto temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void EnumValueDescriptorProto::UnsafeArenaSwap(EnumValueDescriptorProto* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void EnumValueDescriptorProto::InternalSwap(EnumValueDescriptorProto* other) {
+  name_.Swap(&other->name_);
+  std::swap(number_, other->number_);
+  std::swap(options_, other->options_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+}
 
 ::google::protobuf::Metadata EnumValueDescriptorProto::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -4120,17 +4464,27 @@ const int ServiceDescriptorProto::kOptionsFieldNumber;
 #endif  // !_MSC_VER
 
 ServiceDescriptorProto::ServiceDescriptorProto()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.ServiceDescriptorProto)
 }
 
+ServiceDescriptorProto::ServiceDescriptorProto(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena),
+  method_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.ServiceDescriptorProto)
+}
+
 void ServiceDescriptorProto::InitAsDefaultInstance() {
   options_ = const_cast< ::google::protobuf::ServiceOptions*>(&::google::protobuf::ServiceOptions::default_instance());
 }
 
 ServiceDescriptorProto::ServiceDescriptorProto(const ServiceDescriptorProto& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.ServiceDescriptorProto)
@@ -4139,7 +4493,7 @@ ServiceDescriptorProto::ServiceDescriptorProto(const ServiceDescriptorProto& fro
 void ServiceDescriptorProto::SharedCtor() {
   ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  name_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   options_ = NULL;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
@@ -4150,14 +4504,22 @@ ServiceDescriptorProto::~ServiceDescriptorProto() {
 }
 
 void ServiceDescriptorProto::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
+  name_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   if (this != default_instance_) {
     delete options_;
   }
 }
 
+void ServiceDescriptorProto::ArenaDtor(void* object) {
+  ServiceDescriptorProto* _this = reinterpret_cast< ServiceDescriptorProto* >(object);
+  (void)_this;
+}
+void ServiceDescriptorProto::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void ServiceDescriptorProto::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -4175,16 +4537,14 @@ const ServiceDescriptorProto& ServiceDescriptorProto::default_instance() {
 
 ServiceDescriptorProto* ServiceDescriptorProto::default_instance_ = NULL;
 
-ServiceDescriptorProto* ServiceDescriptorProto::New() const {
-  return new ServiceDescriptorProto;
+ServiceDescriptorProto* ServiceDescriptorProto::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<ServiceDescriptorProto>(arena);
 }
 
 void ServiceDescriptorProto::Clear() {
   if (_has_bits_[0 / 32] & 5) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        name_->clear();
-      }
+      name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     if (has_options()) {
       if (options_ != NULL) options_->::google::protobuf::ServiceOptions::Clear();
@@ -4192,7 +4552,9 @@ void ServiceDescriptorProto::Clear() {
   }
   method_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool ServiceDescriptorProto::MergePartialFromCodedStream(
@@ -4213,7 +4575,7 @@ bool ServiceDescriptorProto::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->name().data(), this->name().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "name");
+            "google.protobuf.ServiceDescriptorProto.name");
         } else {
           goto handle_unusual;
         }
@@ -4278,7 +4640,7 @@ void ServiceDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.ServiceDescriptorProto.name");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       1, this->name(), output);
   }
@@ -4295,7 +4657,7 @@ void ServiceDescriptorProto::SerializeWithCachedSizes(
       3, this->options(), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -4310,7 +4672,7 @@ void ServiceDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.ServiceDescriptorProto.name");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         1, this->name(), target);
@@ -4330,7 +4692,7 @@ void ServiceDescriptorProto::SerializeWithCachedSizes(
         3, this->options(), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -4341,7 +4703,7 @@ void ServiceDescriptorProto::SerializeWithCachedSizes(
 int ServiceDescriptorProto::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
+  if (_has_bits_[0 / 32] & 5) {
     // optional string name = 1;
     if (has_name()) {
       total_size += 1 +
@@ -4365,7 +4727,7 @@ int ServiceDescriptorProto::ByteSize() const {
         this->method(i));
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -4399,7 +4761,9 @@ void ServiceDescriptorProto::MergeFrom(const ServiceDescriptorProto& from) {
       mutable_options()->::google::protobuf::ServiceOptions::MergeFrom(from.options());
     }
   }
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void ServiceDescriptorProto::CopyFrom(const ::google::protobuf::Message& from) {
@@ -4424,15 +4788,29 @@ bool ServiceDescriptorProto::IsInitialized() const {
 }
 
 void ServiceDescriptorProto::Swap(ServiceDescriptorProto* other) {
-  if (other != this) {
-    std::swap(name_, other->name_);
-    method_.Swap(&other->method_);
-    std::swap(options_, other->options_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    ServiceDescriptorProto temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void ServiceDescriptorProto::UnsafeArenaSwap(ServiceDescriptorProto* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void ServiceDescriptorProto::InternalSwap(ServiceDescriptorProto* other) {
+  name_.Swap(&other->name_);
+  method_.UnsafeArenaSwap(&other->method_);
+  std::swap(options_, other->options_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+}
 
 ::google::protobuf::Metadata ServiceDescriptorProto::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -4453,17 +4831,26 @@ const int MethodDescriptorProto::kOptionsFieldNumber;
 #endif  // !_MSC_VER
 
 MethodDescriptorProto::MethodDescriptorProto()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.MethodDescriptorProto)
 }
 
+MethodDescriptorProto::MethodDescriptorProto(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.MethodDescriptorProto)
+}
+
 void MethodDescriptorProto::InitAsDefaultInstance() {
   options_ = const_cast< ::google::protobuf::MethodOptions*>(&::google::protobuf::MethodOptions::default_instance());
 }
 
 MethodDescriptorProto::MethodDescriptorProto(const MethodDescriptorProto& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.MethodDescriptorProto)
@@ -4472,9 +4859,9 @@ MethodDescriptorProto::MethodDescriptorProto(const MethodDescriptorProto& from)
 void MethodDescriptorProto::SharedCtor() {
   ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
-  name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-  input_type_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-  output_type_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  name_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  input_type_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  output_type_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   options_ = NULL;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
@@ -4485,20 +4872,24 @@ MethodDescriptorProto::~MethodDescriptorProto() {
 }
 
 void MethodDescriptorProto::SharedDtor() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
-  }
-  if (input_type_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete input_type_;
-  }
-  if (output_type_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete output_type_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
+  name_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+  input_type_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+  output_type_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   if (this != default_instance_) {
     delete options_;
   }
 }
 
+void MethodDescriptorProto::ArenaDtor(void* object) {
+  MethodDescriptorProto* _this = reinterpret_cast< MethodDescriptorProto* >(object);
+  (void)_this;
+}
+void MethodDescriptorProto::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void MethodDescriptorProto::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -4516,33 +4907,29 @@ const MethodDescriptorProto& MethodDescriptorProto::default_instance() {
 
 MethodDescriptorProto* MethodDescriptorProto::default_instance_ = NULL;
 
-MethodDescriptorProto* MethodDescriptorProto::New() const {
-  return new MethodDescriptorProto;
+MethodDescriptorProto* MethodDescriptorProto::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<MethodDescriptorProto>(arena);
 }
 
 void MethodDescriptorProto::Clear() {
   if (_has_bits_[0 / 32] & 15) {
     if (has_name()) {
-      if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        name_->clear();
-      }
+      name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     if (has_input_type()) {
-      if (input_type_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        input_type_->clear();
-      }
+      input_type_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     if (has_output_type()) {
-      if (output_type_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        output_type_->clear();
-      }
+      output_type_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     if (has_options()) {
       if (options_ != NULL) options_->::google::protobuf::MethodOptions::Clear();
     }
   }
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool MethodDescriptorProto::MergePartialFromCodedStream(
@@ -4563,7 +4950,7 @@ bool MethodDescriptorProto::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->name().data(), this->name().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "name");
+            "google.protobuf.MethodDescriptorProto.name");
         } else {
           goto handle_unusual;
         }
@@ -4580,7 +4967,7 @@ bool MethodDescriptorProto::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->input_type().data(), this->input_type().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "input_type");
+            "google.protobuf.MethodDescriptorProto.input_type");
         } else {
           goto handle_unusual;
         }
@@ -4597,7 +4984,7 @@ bool MethodDescriptorProto::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->output_type().data(), this->output_type().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "output_type");
+            "google.protobuf.MethodDescriptorProto.output_type");
         } else {
           goto handle_unusual;
         }
@@ -4648,7 +5035,7 @@ void MethodDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.MethodDescriptorProto.name");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       1, this->name(), output);
   }
@@ -4658,7 +5045,7 @@ void MethodDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->input_type().data(), this->input_type().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "input_type");
+      "google.protobuf.MethodDescriptorProto.input_type");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       2, this->input_type(), output);
   }
@@ -4668,7 +5055,7 @@ void MethodDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->output_type().data(), this->output_type().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "output_type");
+      "google.protobuf.MethodDescriptorProto.output_type");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       3, this->output_type(), output);
   }
@@ -4679,7 +5066,7 @@ void MethodDescriptorProto::SerializeWithCachedSizes(
       4, this->options(), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -4694,7 +5081,7 @@ void MethodDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name().data(), this->name().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name");
+      "google.protobuf.MethodDescriptorProto.name");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         1, this->name(), target);
@@ -4705,7 +5092,7 @@ void MethodDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->input_type().data(), this->input_type().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "input_type");
+      "google.protobuf.MethodDescriptorProto.input_type");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         2, this->input_type(), target);
@@ -4716,7 +5103,7 @@ void MethodDescriptorProto::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->output_type().data(), this->output_type().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "output_type");
+      "google.protobuf.MethodDescriptorProto.output_type");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         3, this->output_type(), target);
@@ -4729,7 +5116,7 @@ void MethodDescriptorProto::SerializeWithCachedSizes(
         4, this->options(), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -4740,7 +5127,7 @@ void MethodDescriptorProto::SerializeWithCachedSizes(
 int MethodDescriptorProto::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
+  if (_has_bits_[0 / 32] & 15) {
     // optional string name = 1;
     if (has_name()) {
       total_size += 1 +
@@ -4770,7 +5157,7 @@ int MethodDescriptorProto::ByteSize() const {
     }
 
   }
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -4809,7 +5196,9 @@ void MethodDescriptorProto::MergeFrom(const MethodDescriptorProto& from) {
       mutable_options()->::google::protobuf::MethodOptions::MergeFrom(from.options());
     }
   }
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void MethodDescriptorProto::CopyFrom(const ::google::protobuf::Message& from) {
@@ -4833,16 +5222,30 @@ bool MethodDescriptorProto::IsInitialized() const {
 }
 
 void MethodDescriptorProto::Swap(MethodDescriptorProto* other) {
-  if (other != this) {
-    std::swap(name_, other->name_);
-    std::swap(input_type_, other->input_type_);
-    std::swap(output_type_, other->output_type_);
-    std::swap(options_, other->options_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    MethodDescriptorProto temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void MethodDescriptorProto::UnsafeArenaSwap(MethodDescriptorProto* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void MethodDescriptorProto::InternalSwap(MethodDescriptorProto* other) {
+  name_.Swap(&other->name_);
+  input_type_.Swap(&other->input_type_);
+  output_type_.Swap(&other->output_type_);
+  std::swap(options_, other->options_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+}
 
 ::google::protobuf::Metadata MethodDescriptorProto::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -4894,16 +5297,26 @@ const int FileOptions::kUninterpretedOptionFieldNumber;
 #endif  // !_MSC_VER
 
 FileOptions::FileOptions()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.FileOptions)
 }
 
+FileOptions::FileOptions(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _extensions_(arena), _internal_metadata_(arena),
+  uninterpreted_option_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.FileOptions)
+}
+
 void FileOptions::InitAsDefaultInstance() {
 }
 
 FileOptions::FileOptions(const FileOptions& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.FileOptions)
@@ -4912,13 +5325,13 @@ FileOptions::FileOptions(const FileOptions& from)
 void FileOptions::SharedCtor() {
   ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
-  java_package_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-  java_outer_classname_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  java_package_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  java_outer_classname_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   java_multiple_files_ = false;
   java_generate_equals_and_hash_ = false;
   java_string_check_utf8_ = false;
   optimize_for_ = 1;
-  go_package_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  go_package_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   cc_generic_services_ = false;
   java_generic_services_ = false;
   py_generic_services_ = false;
@@ -4932,19 +5345,23 @@ FileOptions::~FileOptions() {
 }
 
 void FileOptions::SharedDtor() {
-  if (java_package_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete java_package_;
-  }
-  if (java_outer_classname_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete java_outer_classname_;
-  }
-  if (go_package_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete go_package_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
+  java_package_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+  java_outer_classname_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+  go_package_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   if (this != default_instance_) {
   }
 }
 
+void FileOptions::ArenaDtor(void* object) {
+  FileOptions* _this = reinterpret_cast< FileOptions* >(object);
+  (void)_this;
+}
+void FileOptions::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void FileOptions::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -4962,8 +5379,8 @@ const FileOptions& FileOptions::default_instance() {
 
 FileOptions* FileOptions::default_instance_ = NULL;
 
-FileOptions* FileOptions::New() const {
-  return new FileOptions;
+FileOptions* FileOptions::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<FileOptions>(arena);
 }
 
 void FileOptions::Clear() {
@@ -4981,20 +5398,14 @@ void FileOptions::Clear() {
   if (_has_bits_[0 / 32] & 255) {
     ZR_(java_multiple_files_, cc_generic_services_);
     if (has_java_package()) {
-      if (java_package_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        java_package_->clear();
-      }
+      java_package_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     if (has_java_outer_classname()) {
-      if (java_outer_classname_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        java_outer_classname_->clear();
-      }
+      java_outer_classname_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     optimize_for_ = 1;
     if (has_go_package()) {
-      if (go_package_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        go_package_->clear();
-      }
+      go_package_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
   }
   ZR_(java_generic_services_, deprecated_);
@@ -5004,7 +5415,9 @@ void FileOptions::Clear() {
 
   uninterpreted_option_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool FileOptions::MergePartialFromCodedStream(
@@ -5025,7 +5438,7 @@ bool FileOptions::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->java_package().data(), this->java_package().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "java_package");
+            "google.protobuf.FileOptions.java_package");
         } else {
           goto handle_unusual;
         }
@@ -5042,7 +5455,7 @@ bool FileOptions::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->java_outer_classname().data(), this->java_outer_classname().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "java_outer_classname");
+            "google.protobuf.FileOptions.java_outer_classname");
         } else {
           goto handle_unusual;
         }
@@ -5094,7 +5507,7 @@ bool FileOptions::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->go_package().data(), this->go_package().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "go_package");
+            "google.protobuf.FileOptions.go_package");
         } else {
           goto handle_unusual;
         }
@@ -5241,7 +5654,7 @@ void FileOptions::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->java_package().data(), this->java_package().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "java_package");
+      "google.protobuf.FileOptions.java_package");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       1, this->java_package(), output);
   }
@@ -5251,7 +5664,7 @@ void FileOptions::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->java_outer_classname().data(), this->java_outer_classname().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "java_outer_classname");
+      "google.protobuf.FileOptions.java_outer_classname");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       8, this->java_outer_classname(), output);
   }
@@ -5272,7 +5685,7 @@ void FileOptions::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->go_package().data(), this->go_package().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "go_package");
+      "google.protobuf.FileOptions.go_package");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       11, this->go_package(), output);
   }
@@ -5317,7 +5730,7 @@ void FileOptions::SerializeWithCachedSizes(
   _extensions_.SerializeWithCachedSizes(
       1000, 536870912, output);
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -5332,7 +5745,7 @@ void FileOptions::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->java_package().data(), this->java_package().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "java_package");
+      "google.protobuf.FileOptions.java_package");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         1, this->java_package(), target);
@@ -5343,7 +5756,7 @@ void FileOptions::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->java_outer_classname().data(), this->java_outer_classname().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "java_outer_classname");
+      "google.protobuf.FileOptions.java_outer_classname");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         8, this->java_outer_classname(), target);
@@ -5365,7 +5778,7 @@ void FileOptions::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->go_package().data(), this->go_package().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "go_package");
+      "google.protobuf.FileOptions.go_package");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         11, this->go_package(), target);
@@ -5412,7 +5825,7 @@ void FileOptions::SerializeWithCachedSizes(
   target = _extensions_.SerializeWithCachedSizesToArray(
       1000, 536870912, target);
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -5423,7 +5836,7 @@ void FileOptions::SerializeWithCachedSizes(
 int FileOptions::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
+  if (_has_bits_[0 / 32] & 255) {
     // optional string java_package = 1;
     if (has_java_package()) {
       total_size += 1 +
@@ -5472,7 +5885,7 @@ int FileOptions::ByteSize() const {
     }
 
   }
-  if (_has_bits_[8 / 32] & (0xffu << (8 % 32))) {
+  if (_has_bits_[8 / 32] & 1792) {
     // optional bool java_generic_services = 17 [default = false];
     if (has_java_generic_services()) {
       total_size += 2 + 1;
@@ -5499,7 +5912,7 @@ int FileOptions::ByteSize() const {
 
   total_size += _extensions_.ByteSize();
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -5563,7 +5976,9 @@ void FileOptions::MergeFrom(const FileOptions& from) {
     }
   }
   _extensions_.MergeFrom(from._extensions_);
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void FileOptions::CopyFrom(const ::google::protobuf::Message& from) {
@@ -5586,24 +6001,38 @@ bool FileOptions::IsInitialized() const {
 }
 
 void FileOptions::Swap(FileOptions* other) {
-  if (other != this) {
-    std::swap(java_package_, other->java_package_);
-    std::swap(java_outer_classname_, other->java_outer_classname_);
-    std::swap(java_multiple_files_, other->java_multiple_files_);
-    std::swap(java_generate_equals_and_hash_, other->java_generate_equals_and_hash_);
-    std::swap(java_string_check_utf8_, other->java_string_check_utf8_);
-    std::swap(optimize_for_, other->optimize_for_);
-    std::swap(go_package_, other->go_package_);
-    std::swap(cc_generic_services_, other->cc_generic_services_);
-    std::swap(java_generic_services_, other->java_generic_services_);
-    std::swap(py_generic_services_, other->py_generic_services_);
-    std::swap(deprecated_, other->deprecated_);
-    uninterpreted_option_.Swap(&other->uninterpreted_option_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
-    _extensions_.Swap(&other->_extensions_);
-  }
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    FileOptions temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
+  }
+}
+void FileOptions::UnsafeArenaSwap(FileOptions* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void FileOptions::InternalSwap(FileOptions* other) {
+  java_package_.Swap(&other->java_package_);
+  java_outer_classname_.Swap(&other->java_outer_classname_);
+  std::swap(java_multiple_files_, other->java_multiple_files_);
+  std::swap(java_generate_equals_and_hash_, other->java_generate_equals_and_hash_);
+  std::swap(java_string_check_utf8_, other->java_string_check_utf8_);
+  std::swap(optimize_for_, other->optimize_for_);
+  go_package_.Swap(&other->go_package_);
+  std::swap(cc_generic_services_, other->cc_generic_services_);
+  std::swap(java_generic_services_, other->java_generic_services_);
+  std::swap(py_generic_services_, other->py_generic_services_);
+  std::swap(deprecated_, other->deprecated_);
+  uninterpreted_option_.UnsafeArenaSwap(&other->uninterpreted_option_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+  _extensions_.Swap(&other->_extensions_);
 }
 
 ::google::protobuf::Metadata FileOptions::GetMetadata() const {
@@ -5621,20 +6050,31 @@ void FileOptions::Swap(FileOptions* other) {
 const int MessageOptions::kMessageSetWireFormatFieldNumber;
 const int MessageOptions::kNoStandardDescriptorAccessorFieldNumber;
 const int MessageOptions::kDeprecatedFieldNumber;
+const int MessageOptions::kMapEntryFieldNumber;
 const int MessageOptions::kUninterpretedOptionFieldNumber;
 #endif  // !_MSC_VER
 
 MessageOptions::MessageOptions()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.MessageOptions)
 }
 
+MessageOptions::MessageOptions(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _extensions_(arena), _internal_metadata_(arena),
+  uninterpreted_option_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.MessageOptions)
+}
+
 void MessageOptions::InitAsDefaultInstance() {
 }
 
 MessageOptions::MessageOptions(const MessageOptions& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.MessageOptions)
@@ -5645,6 +6085,7 @@ void MessageOptions::SharedCtor() {
   message_set_wire_format_ = false;
   no_standard_descriptor_accessor_ = false;
   deprecated_ = false;
+  map_entry_ = false;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
 
@@ -5654,10 +6095,20 @@ MessageOptions::~MessageOptions() {
 }
 
 void MessageOptions::SharedDtor() {
+  if (GetArenaNoVirtual() != NULL) {
+    return;
+  }
+
   if (this != default_instance_) {
   }
 }
 
+void MessageOptions::ArenaDtor(void* object) {
+  MessageOptions* _this = reinterpret_cast< MessageOptions* >(object);
+  (void)_this;
+}
+void MessageOptions::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void MessageOptions::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -5675,8 +6126,8 @@ const MessageOptions& MessageOptions::default_instance() {
 
 MessageOptions* MessageOptions::default_instance_ = NULL;
 
-MessageOptions* MessageOptions::New() const {
-  return new MessageOptions;
+MessageOptions* MessageOptions::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<MessageOptions>(arena);
 }
 
 void MessageOptions::Clear() {
@@ -5691,14 +6142,16 @@ void MessageOptions::Clear() {
     ::memset(&first, 0, n);                                \
   } while (0)
 
-  ZR_(message_set_wire_format_, deprecated_);
+  ZR_(message_set_wire_format_, map_entry_);
 
 #undef OFFSET_OF_FIELD_
 #undef ZR_
 
   uninterpreted_option_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool MessageOptions::MergePartialFromCodedStream(
@@ -5751,6 +6204,21 @@ bool MessageOptions::MergePartialFromCodedStream(
         } else {
           goto handle_unusual;
         }
+        if (input->ExpectTag(56)) goto parse_map_entry;
+        break;
+      }
+
+      // optional bool map_entry = 7;
+      case 7: {
+        if (tag == 56) {
+         parse_map_entry:
+          DO_((::google::protobuf::internal::WireFormatLite::ReadPrimitive<
+                   bool, ::google::protobuf::internal::WireFormatLite::TYPE_BOOL>(
+                 input, &map_entry_)));
+          set_has_map_entry();
+        } else {
+          goto handle_unusual;
+        }
         if (input->ExpectTag(7994)) goto parse_uninterpreted_option;
         break;
       }
@@ -5814,6 +6282,11 @@ void MessageOptions::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormatLite::WriteBool(3, this->deprecated(), output);
   }
 
+  // optional bool map_entry = 7;
+  if (has_map_entry()) {
+    ::google::protobuf::internal::WireFormatLite::WriteBool(7, this->map_entry(), output);
+  }
+
   // repeated .google.protobuf.UninterpretedOption uninterpreted_option = 999;
   for (int i = 0; i < this->uninterpreted_option_size(); i++) {
     ::google::protobuf::internal::WireFormatLite::WriteMessageMaybeToArray(
@@ -5824,7 +6297,7 @@ void MessageOptions::SerializeWithCachedSizes(
   _extensions_.SerializeWithCachedSizes(
       1000, 536870912, output);
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -5849,6 +6322,11 @@ void MessageOptions::SerializeWithCachedSizes(
     target = ::google::protobuf::internal::WireFormatLite::WriteBoolToArray(3, this->deprecated(), target);
   }
 
+  // optional bool map_entry = 7;
+  if (has_map_entry()) {
+    target = ::google::protobuf::internal::WireFormatLite::WriteBoolToArray(7, this->map_entry(), target);
+  }
+
   // repeated .google.protobuf.UninterpretedOption uninterpreted_option = 999;
   for (int i = 0; i < this->uninterpreted_option_size(); i++) {
     target = ::google::protobuf::internal::WireFormatLite::
@@ -5860,7 +6338,7 @@ void MessageOptions::SerializeWithCachedSizes(
   target = _extensions_.SerializeWithCachedSizesToArray(
       1000, 536870912, target);
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -5871,7 +6349,7 @@ void MessageOptions::SerializeWithCachedSizes(
 int MessageOptions::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
+  if (_has_bits_[0 / 32] & 15) {
     // optional bool message_set_wire_format = 1 [default = false];
     if (has_message_set_wire_format()) {
       total_size += 1 + 1;
@@ -5887,6 +6365,11 @@ int MessageOptions::ByteSize() const {
       total_size += 1 + 1;
     }
 
+    // optional bool map_entry = 7;
+    if (has_map_entry()) {
+      total_size += 1 + 1;
+    }
+
   }
   // repeated .google.protobuf.UninterpretedOption uninterpreted_option = 999;
   total_size += 2 * this->uninterpreted_option_size();
@@ -5898,7 +6381,7 @@ int MessageOptions::ByteSize() const {
 
   total_size += _extensions_.ByteSize();
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -5934,9 +6417,14 @@ void MessageOptions::MergeFrom(const MessageOptions& from) {
     if (from.has_deprecated()) {
       set_deprecated(from.deprecated());
     }
+    if (from.has_map_entry()) {
+      set_map_entry(from.map_entry());
+    }
   }
   _extensions_.MergeFrom(from._extensions_);
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void MessageOptions::CopyFrom(const ::google::protobuf::Message& from) {
@@ -5959,17 +6447,32 @@ bool MessageOptions::IsInitialized() const {
 }
 
 void MessageOptions::Swap(MessageOptions* other) {
-  if (other != this) {
-    std::swap(message_set_wire_format_, other->message_set_wire_format_);
-    std::swap(no_standard_descriptor_accessor_, other->no_standard_descriptor_accessor_);
-    std::swap(deprecated_, other->deprecated_);
-    uninterpreted_option_.Swap(&other->uninterpreted_option_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
-    _extensions_.Swap(&other->_extensions_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    MessageOptions temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void MessageOptions::UnsafeArenaSwap(MessageOptions* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void MessageOptions::InternalSwap(MessageOptions* other) {
+  std::swap(message_set_wire_format_, other->message_set_wire_format_);
+  std::swap(no_standard_descriptor_accessor_, other->no_standard_descriptor_accessor_);
+  std::swap(deprecated_, other->deprecated_);
+  std::swap(map_entry_, other->map_entry_);
+  uninterpreted_option_.UnsafeArenaSwap(&other->uninterpreted_option_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+  _extensions_.Swap(&other->_extensions_);
+}
 
 ::google::protobuf::Metadata MessageOptions::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -6010,35 +6513,42 @@ const int FieldOptions::kCtypeFieldNumber;
 const int FieldOptions::kPackedFieldNumber;
 const int FieldOptions::kLazyFieldNumber;
 const int FieldOptions::kDeprecatedFieldNumber;
-const int FieldOptions::kExperimentalMapKeyFieldNumber;
 const int FieldOptions::kWeakFieldNumber;
 const int FieldOptions::kUninterpretedOptionFieldNumber;
 #endif  // !_MSC_VER
 
 FieldOptions::FieldOptions()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.FieldOptions)
 }
 
+FieldOptions::FieldOptions(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _extensions_(arena), _internal_metadata_(arena),
+  uninterpreted_option_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.FieldOptions)
+}
+
 void FieldOptions::InitAsDefaultInstance() {
 }
 
 FieldOptions::FieldOptions(const FieldOptions& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.FieldOptions)
 }
 
 void FieldOptions::SharedCtor() {
-  ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
   ctype_ = 0;
   packed_ = false;
   lazy_ = false;
   deprecated_ = false;
-  experimental_map_key_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   weak_ = false;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
@@ -6049,13 +6559,20 @@ FieldOptions::~FieldOptions() {
 }
 
 void FieldOptions::SharedDtor() {
-  if (experimental_map_key_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete experimental_map_key_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
   if (this != default_instance_) {
   }
 }
 
+void FieldOptions::ArenaDtor(void* object) {
+  FieldOptions* _this = reinterpret_cast< FieldOptions* >(object);
+  (void)_this;
+}
+void FieldOptions::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void FieldOptions::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -6073,8 +6590,8 @@ const FieldOptions& FieldOptions::default_instance() {
 
 FieldOptions* FieldOptions::default_instance_ = NULL;
 
-FieldOptions* FieldOptions::New() const {
-  return new FieldOptions;
+FieldOptions* FieldOptions::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<FieldOptions>(arena);
 }
 
 void FieldOptions::Clear() {
@@ -6089,13 +6606,8 @@ void FieldOptions::Clear() {
     ::memset(&first, 0, n);                                \
   } while (0)
 
-  if (_has_bits_[0 / 32] & 63) {
+  if (_has_bits_[0 / 32] & 31) {
     ZR_(ctype_, weak_);
-    if (has_experimental_map_key()) {
-      if (experimental_map_key_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        experimental_map_key_->clear();
-      }
-    }
   }
 
 #undef OFFSET_OF_FIELD_
@@ -6103,7 +6615,9 @@ void FieldOptions::Clear() {
 
   uninterpreted_option_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool FieldOptions::MergePartialFromCodedStream(
@@ -6176,23 +6690,6 @@ bool FieldOptions::MergePartialFromCodedStream(
         } else {
           goto handle_unusual;
         }
-        if (input->ExpectTag(74)) goto parse_experimental_map_key;
-        break;
-      }
-
-      // optional string experimental_map_key = 9;
-      case 9: {
-        if (tag == 74) {
-         parse_experimental_map_key:
-          DO_(::google::protobuf::internal::WireFormatLite::ReadString(
-                input, this->mutable_experimental_map_key()));
-          ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
-            this->experimental_map_key().data(), this->experimental_map_key().length(),
-            ::google::protobuf::internal::WireFormat::PARSE,
-            "experimental_map_key");
-        } else {
-          goto handle_unusual;
-        }
         if (input->ExpectTag(80)) goto parse_weak;
         break;
       }
@@ -6277,16 +6774,6 @@ void FieldOptions::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormatLite::WriteBool(5, this->lazy(), output);
   }
 
-  // optional string experimental_map_key = 9;
-  if (has_experimental_map_key()) {
-    ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
-      this->experimental_map_key().data(), this->experimental_map_key().length(),
-      ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "experimental_map_key");
-    ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
-      9, this->experimental_map_key(), output);
-  }
-
   // optional bool weak = 10 [default = false];
   if (has_weak()) {
     ::google::protobuf::internal::WireFormatLite::WriteBool(10, this->weak(), output);
@@ -6302,7 +6789,7 @@ void FieldOptions::SerializeWithCachedSizes(
   _extensions_.SerializeWithCachedSizes(
       1000, 536870912, output);
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -6333,17 +6820,6 @@ void FieldOptions::SerializeWithCachedSizes(
     target = ::google::protobuf::internal::WireFormatLite::WriteBoolToArray(5, this->lazy(), target);
   }
 
-  // optional string experimental_map_key = 9;
-  if (has_experimental_map_key()) {
-    ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
-      this->experimental_map_key().data(), this->experimental_map_key().length(),
-      ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "experimental_map_key");
-    target =
-      ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
-        9, this->experimental_map_key(), target);
-  }
-
   // optional bool weak = 10 [default = false];
   if (has_weak()) {
     target = ::google::protobuf::internal::WireFormatLite::WriteBoolToArray(10, this->weak(), target);
@@ -6360,7 +6836,7 @@ void FieldOptions::SerializeWithCachedSizes(
   target = _extensions_.SerializeWithCachedSizesToArray(
       1000, 536870912, target);
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -6371,7 +6847,7 @@ void FieldOptions::SerializeWithCachedSizes(
 int FieldOptions::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
+  if (_has_bits_[0 / 32] & 31) {
     // optional .google.protobuf.FieldOptions.CType ctype = 1 [default = STRING];
     if (has_ctype()) {
       total_size += 1 +
@@ -6393,13 +6869,6 @@ int FieldOptions::ByteSize() const {
       total_size += 1 + 1;
     }
 
-    // optional string experimental_map_key = 9;
-    if (has_experimental_map_key()) {
-      total_size += 1 +
-        ::google::protobuf::internal::WireFormatLite::StringSize(
-          this->experimental_map_key());
-    }
-
     // optional bool weak = 10 [default = false];
     if (has_weak()) {
       total_size += 1 + 1;
@@ -6416,7 +6885,7 @@ int FieldOptions::ByteSize() const {
 
   total_size += _extensions_.ByteSize();
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -6455,15 +6924,14 @@ void FieldOptions::MergeFrom(const FieldOptions& from) {
     if (from.has_deprecated()) {
       set_deprecated(from.deprecated());
     }
-    if (from.has_experimental_map_key()) {
-      set_experimental_map_key(from.experimental_map_key());
-    }
     if (from.has_weak()) {
       set_weak(from.weak());
     }
   }
   _extensions_.MergeFrom(from._extensions_);
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void FieldOptions::CopyFrom(const ::google::protobuf::Message& from) {
@@ -6486,19 +6954,32 @@ bool FieldOptions::IsInitialized() const {
 }
 
 void FieldOptions::Swap(FieldOptions* other) {
-  if (other != this) {
-    std::swap(ctype_, other->ctype_);
-    std::swap(packed_, other->packed_);
-    std::swap(lazy_, other->lazy_);
-    std::swap(deprecated_, other->deprecated_);
-    std::swap(experimental_map_key_, other->experimental_map_key_);
-    std::swap(weak_, other->weak_);
-    uninterpreted_option_.Swap(&other->uninterpreted_option_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
-    _extensions_.Swap(&other->_extensions_);
-  }
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    FieldOptions temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
+  }
+}
+void FieldOptions::UnsafeArenaSwap(FieldOptions* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void FieldOptions::InternalSwap(FieldOptions* other) {
+  std::swap(ctype_, other->ctype_);
+  std::swap(packed_, other->packed_);
+  std::swap(lazy_, other->lazy_);
+  std::swap(deprecated_, other->deprecated_);
+  std::swap(weak_, other->weak_);
+  uninterpreted_option_.UnsafeArenaSwap(&other->uninterpreted_option_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+  _extensions_.Swap(&other->_extensions_);
 }
 
 ::google::protobuf::Metadata FieldOptions::GetMetadata() const {
@@ -6519,16 +7000,26 @@ const int EnumOptions::kUninterpretedOptionFieldNumber;
 #endif  // !_MSC_VER
 
 EnumOptions::EnumOptions()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.EnumOptions)
 }
 
+EnumOptions::EnumOptions(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _extensions_(arena), _internal_metadata_(arena),
+  uninterpreted_option_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.EnumOptions)
+}
+
 void EnumOptions::InitAsDefaultInstance() {
 }
 
 EnumOptions::EnumOptions(const EnumOptions& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.EnumOptions)
@@ -6547,10 +7038,20 @@ EnumOptions::~EnumOptions() {
 }
 
 void EnumOptions::SharedDtor() {
+  if (GetArenaNoVirtual() != NULL) {
+    return;
+  }
+
   if (this != default_instance_) {
   }
 }
 
+void EnumOptions::ArenaDtor(void* object) {
+  EnumOptions* _this = reinterpret_cast< EnumOptions* >(object);
+  (void)_this;
+}
+void EnumOptions::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void EnumOptions::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -6568,8 +7069,8 @@ const EnumOptions& EnumOptions::default_instance() {
 
 EnumOptions* EnumOptions::default_instance_ = NULL;
 
-EnumOptions* EnumOptions::New() const {
-  return new EnumOptions;
+EnumOptions* EnumOptions::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<EnumOptions>(arena);
 }
 
 void EnumOptions::Clear() {
@@ -6591,7 +7092,9 @@ void EnumOptions::Clear() {
 
   uninterpreted_option_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool EnumOptions::MergePartialFromCodedStream(
@@ -6697,7 +7200,7 @@ void EnumOptions::SerializeWithCachedSizes(
   _extensions_.SerializeWithCachedSizes(
       1000, 536870912, output);
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -6728,7 +7231,7 @@ void EnumOptions::SerializeWithCachedSizes(
   target = _extensions_.SerializeWithCachedSizesToArray(
       1000, 536870912, target);
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -6739,7 +7242,7 @@ void EnumOptions::SerializeWithCachedSizes(
 int EnumOptions::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
+  if (_has_bits_[0 / 32] & 3) {
     // optional bool allow_alias = 2;
     if (has_allow_alias()) {
       total_size += 1 + 1;
@@ -6761,7 +7264,7 @@ int EnumOptions::ByteSize() const {
 
   total_size += _extensions_.ByteSize();
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -6796,7 +7299,9 @@ void EnumOptions::MergeFrom(const EnumOptions& from) {
     }
   }
   _extensions_.MergeFrom(from._extensions_);
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void EnumOptions::CopyFrom(const ::google::protobuf::Message& from) {
@@ -6819,16 +7324,30 @@ bool EnumOptions::IsInitialized() const {
 }
 
 void EnumOptions::Swap(EnumOptions* other) {
-  if (other != this) {
-    std::swap(allow_alias_, other->allow_alias_);
-    std::swap(deprecated_, other->deprecated_);
-    uninterpreted_option_.Swap(&other->uninterpreted_option_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
-    _extensions_.Swap(&other->_extensions_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    EnumOptions temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void EnumOptions::UnsafeArenaSwap(EnumOptions* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void EnumOptions::InternalSwap(EnumOptions* other) {
+  std::swap(allow_alias_, other->allow_alias_);
+  std::swap(deprecated_, other->deprecated_);
+  uninterpreted_option_.UnsafeArenaSwap(&other->uninterpreted_option_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+  _extensions_.Swap(&other->_extensions_);
+}
 
 ::google::protobuf::Metadata EnumOptions::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -6847,16 +7366,26 @@ const int EnumValueOptions::kUninterpretedOptionFieldNumber;
 #endif  // !_MSC_VER
 
 EnumValueOptions::EnumValueOptions()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.EnumValueOptions)
 }
 
+EnumValueOptions::EnumValueOptions(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _extensions_(arena), _internal_metadata_(arena),
+  uninterpreted_option_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.EnumValueOptions)
+}
+
 void EnumValueOptions::InitAsDefaultInstance() {
 }
 
 EnumValueOptions::EnumValueOptions(const EnumValueOptions& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.EnumValueOptions)
@@ -6874,10 +7403,20 @@ EnumValueOptions::~EnumValueOptions() {
 }
 
 void EnumValueOptions::SharedDtor() {
+  if (GetArenaNoVirtual() != NULL) {
+    return;
+  }
+
   if (this != default_instance_) {
   }
 }
 
+void EnumValueOptions::ArenaDtor(void* object) {
+  EnumValueOptions* _this = reinterpret_cast< EnumValueOptions* >(object);
+  (void)_this;
+}
+void EnumValueOptions::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void EnumValueOptions::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -6895,8 +7434,8 @@ const EnumValueOptions& EnumValueOptions::default_instance() {
 
 EnumValueOptions* EnumValueOptions::default_instance_ = NULL;
 
-EnumValueOptions* EnumValueOptions::New() const {
-  return new EnumValueOptions;
+EnumValueOptions* EnumValueOptions::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<EnumValueOptions>(arena);
 }
 
 void EnumValueOptions::Clear() {
@@ -6904,7 +7443,9 @@ void EnumValueOptions::Clear() {
   deprecated_ = false;
   uninterpreted_option_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool EnumValueOptions::MergePartialFromCodedStream(
@@ -6990,7 +7531,7 @@ void EnumValueOptions::SerializeWithCachedSizes(
   _extensions_.SerializeWithCachedSizes(
       1000, 536870912, output);
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -7016,7 +7557,7 @@ void EnumValueOptions::SerializeWithCachedSizes(
   target = _extensions_.SerializeWithCachedSizesToArray(
       1000, 536870912, target);
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -7027,13 +7568,11 @@ void EnumValueOptions::SerializeWithCachedSizes(
 int EnumValueOptions::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
-    // optional bool deprecated = 1 [default = false];
-    if (has_deprecated()) {
-      total_size += 1 + 1;
-    }
-
+  // optional bool deprecated = 1 [default = false];
+  if (has_deprecated()) {
+    total_size += 1 + 1;
   }
+
   // repeated .google.protobuf.UninterpretedOption uninterpreted_option = 999;
   total_size += 2 * this->uninterpreted_option_size();
   for (int i = 0; i < this->uninterpreted_option_size(); i++) {
@@ -7044,7 +7583,7 @@ int EnumValueOptions::ByteSize() const {
 
   total_size += _extensions_.ByteSize();
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -7076,7 +7615,9 @@ void EnumValueOptions::MergeFrom(const EnumValueOptions& from) {
     }
   }
   _extensions_.MergeFrom(from._extensions_);
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void EnumValueOptions::CopyFrom(const ::google::protobuf::Message& from) {
@@ -7099,15 +7640,29 @@ bool EnumValueOptions::IsInitialized() const {
 }
 
 void EnumValueOptions::Swap(EnumValueOptions* other) {
-  if (other != this) {
-    std::swap(deprecated_, other->deprecated_);
-    uninterpreted_option_.Swap(&other->uninterpreted_option_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
-    _extensions_.Swap(&other->_extensions_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    EnumValueOptions temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void EnumValueOptions::UnsafeArenaSwap(EnumValueOptions* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void EnumValueOptions::InternalSwap(EnumValueOptions* other) {
+  std::swap(deprecated_, other->deprecated_);
+  uninterpreted_option_.UnsafeArenaSwap(&other->uninterpreted_option_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+  _extensions_.Swap(&other->_extensions_);
+}
 
 ::google::protobuf::Metadata EnumValueOptions::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -7126,16 +7681,26 @@ const int ServiceOptions::kUninterpretedOptionFieldNumber;
 #endif  // !_MSC_VER
 
 ServiceOptions::ServiceOptions()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.ServiceOptions)
 }
 
+ServiceOptions::ServiceOptions(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _extensions_(arena), _internal_metadata_(arena),
+  uninterpreted_option_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.ServiceOptions)
+}
+
 void ServiceOptions::InitAsDefaultInstance() {
 }
 
 ServiceOptions::ServiceOptions(const ServiceOptions& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.ServiceOptions)
@@ -7153,10 +7718,20 @@ ServiceOptions::~ServiceOptions() {
 }
 
 void ServiceOptions::SharedDtor() {
+  if (GetArenaNoVirtual() != NULL) {
+    return;
+  }
+
   if (this != default_instance_) {
   }
 }
 
+void ServiceOptions::ArenaDtor(void* object) {
+  ServiceOptions* _this = reinterpret_cast< ServiceOptions* >(object);
+  (void)_this;
+}
+void ServiceOptions::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void ServiceOptions::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -7174,8 +7749,8 @@ const ServiceOptions& ServiceOptions::default_instance() {
 
 ServiceOptions* ServiceOptions::default_instance_ = NULL;
 
-ServiceOptions* ServiceOptions::New() const {
-  return new ServiceOptions;
+ServiceOptions* ServiceOptions::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<ServiceOptions>(arena);
 }
 
 void ServiceOptions::Clear() {
@@ -7183,7 +7758,9 @@ void ServiceOptions::Clear() {
   deprecated_ = false;
   uninterpreted_option_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool ServiceOptions::MergePartialFromCodedStream(
@@ -7269,7 +7846,7 @@ void ServiceOptions::SerializeWithCachedSizes(
   _extensions_.SerializeWithCachedSizes(
       1000, 536870912, output);
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -7295,7 +7872,7 @@ void ServiceOptions::SerializeWithCachedSizes(
   target = _extensions_.SerializeWithCachedSizesToArray(
       1000, 536870912, target);
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -7306,13 +7883,11 @@ void ServiceOptions::SerializeWithCachedSizes(
 int ServiceOptions::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
-    // optional bool deprecated = 33 [default = false];
-    if (has_deprecated()) {
-      total_size += 2 + 1;
-    }
-
+  // optional bool deprecated = 33 [default = false];
+  if (has_deprecated()) {
+    total_size += 2 + 1;
   }
+
   // repeated .google.protobuf.UninterpretedOption uninterpreted_option = 999;
   total_size += 2 * this->uninterpreted_option_size();
   for (int i = 0; i < this->uninterpreted_option_size(); i++) {
@@ -7323,7 +7898,7 @@ int ServiceOptions::ByteSize() const {
 
   total_size += _extensions_.ByteSize();
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -7355,7 +7930,9 @@ void ServiceOptions::MergeFrom(const ServiceOptions& from) {
     }
   }
   _extensions_.MergeFrom(from._extensions_);
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void ServiceOptions::CopyFrom(const ::google::protobuf::Message& from) {
@@ -7378,15 +7955,29 @@ bool ServiceOptions::IsInitialized() const {
 }
 
 void ServiceOptions::Swap(ServiceOptions* other) {
-  if (other != this) {
-    std::swap(deprecated_, other->deprecated_);
-    uninterpreted_option_.Swap(&other->uninterpreted_option_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
-    _extensions_.Swap(&other->_extensions_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    ServiceOptions temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void ServiceOptions::UnsafeArenaSwap(ServiceOptions* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void ServiceOptions::InternalSwap(ServiceOptions* other) {
+  std::swap(deprecated_, other->deprecated_);
+  uninterpreted_option_.UnsafeArenaSwap(&other->uninterpreted_option_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+  _extensions_.Swap(&other->_extensions_);
+}
 
 ::google::protobuf::Metadata ServiceOptions::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -7405,16 +7996,26 @@ const int MethodOptions::kUninterpretedOptionFieldNumber;
 #endif  // !_MSC_VER
 
 MethodOptions::MethodOptions()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.MethodOptions)
 }
 
+MethodOptions::MethodOptions(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _extensions_(arena), _internal_metadata_(arena),
+  uninterpreted_option_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.MethodOptions)
+}
+
 void MethodOptions::InitAsDefaultInstance() {
 }
 
 MethodOptions::MethodOptions(const MethodOptions& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.MethodOptions)
@@ -7432,10 +8033,20 @@ MethodOptions::~MethodOptions() {
 }
 
 void MethodOptions::SharedDtor() {
+  if (GetArenaNoVirtual() != NULL) {
+    return;
+  }
+
   if (this != default_instance_) {
   }
 }
 
+void MethodOptions::ArenaDtor(void* object) {
+  MethodOptions* _this = reinterpret_cast< MethodOptions* >(object);
+  (void)_this;
+}
+void MethodOptions::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void MethodOptions::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -7453,8 +8064,8 @@ const MethodOptions& MethodOptions::default_instance() {
 
 MethodOptions* MethodOptions::default_instance_ = NULL;
 
-MethodOptions* MethodOptions::New() const {
-  return new MethodOptions;
+MethodOptions* MethodOptions::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<MethodOptions>(arena);
 }
 
 void MethodOptions::Clear() {
@@ -7462,7 +8073,9 @@ void MethodOptions::Clear() {
   deprecated_ = false;
   uninterpreted_option_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool MethodOptions::MergePartialFromCodedStream(
@@ -7548,7 +8161,7 @@ void MethodOptions::SerializeWithCachedSizes(
   _extensions_.SerializeWithCachedSizes(
       1000, 536870912, output);
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -7574,7 +8187,7 @@ void MethodOptions::SerializeWithCachedSizes(
   target = _extensions_.SerializeWithCachedSizesToArray(
       1000, 536870912, target);
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -7585,13 +8198,11 @@ void MethodOptions::SerializeWithCachedSizes(
 int MethodOptions::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
-    // optional bool deprecated = 33 [default = false];
-    if (has_deprecated()) {
-      total_size += 2 + 1;
-    }
-
+  // optional bool deprecated = 33 [default = false];
+  if (has_deprecated()) {
+    total_size += 2 + 1;
   }
+
   // repeated .google.protobuf.UninterpretedOption uninterpreted_option = 999;
   total_size += 2 * this->uninterpreted_option_size();
   for (int i = 0; i < this->uninterpreted_option_size(); i++) {
@@ -7602,7 +8213,7 @@ int MethodOptions::ByteSize() const {
 
   total_size += _extensions_.ByteSize();
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -7634,7 +8245,9 @@ void MethodOptions::MergeFrom(const MethodOptions& from) {
     }
   }
   _extensions_.MergeFrom(from._extensions_);
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void MethodOptions::CopyFrom(const ::google::protobuf::Message& from) {
@@ -7657,15 +8270,29 @@ bool MethodOptions::IsInitialized() const {
 }
 
 void MethodOptions::Swap(MethodOptions* other) {
-  if (other != this) {
-    std::swap(deprecated_, other->deprecated_);
-    uninterpreted_option_.Swap(&other->uninterpreted_option_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
-    _extensions_.Swap(&other->_extensions_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    MethodOptions temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void MethodOptions::UnsafeArenaSwap(MethodOptions* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void MethodOptions::InternalSwap(MethodOptions* other) {
+  std::swap(deprecated_, other->deprecated_);
+  uninterpreted_option_.UnsafeArenaSwap(&other->uninterpreted_option_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+  _extensions_.Swap(&other->_extensions_);
+}
 
 ::google::protobuf::Metadata MethodOptions::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -7684,16 +8311,25 @@ const int UninterpretedOption_NamePart::kIsExtensionFieldNumber;
 #endif  // !_MSC_VER
 
 UninterpretedOption_NamePart::UninterpretedOption_NamePart()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.UninterpretedOption.NamePart)
 }
 
+UninterpretedOption_NamePart::UninterpretedOption_NamePart(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.UninterpretedOption.NamePart)
+}
+
 void UninterpretedOption_NamePart::InitAsDefaultInstance() {
 }
 
 UninterpretedOption_NamePart::UninterpretedOption_NamePart(const UninterpretedOption_NamePart& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.UninterpretedOption.NamePart)
@@ -7702,7 +8338,7 @@ UninterpretedOption_NamePart::UninterpretedOption_NamePart(const UninterpretedOp
 void UninterpretedOption_NamePart::SharedCtor() {
   ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
-  name_part_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  name_part_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   is_extension_ = false;
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
@@ -7713,13 +8349,21 @@ UninterpretedOption_NamePart::~UninterpretedOption_NamePart() {
 }
 
 void UninterpretedOption_NamePart::SharedDtor() {
-  if (name_part_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_part_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
+  name_part_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   if (this != default_instance_) {
   }
 }
 
+void UninterpretedOption_NamePart::ArenaDtor(void* object) {
+  UninterpretedOption_NamePart* _this = reinterpret_cast< UninterpretedOption_NamePart* >(object);
+  (void)_this;
+}
+void UninterpretedOption_NamePart::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void UninterpretedOption_NamePart::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -7737,21 +8381,21 @@ const UninterpretedOption_NamePart& UninterpretedOption_NamePart::default_instan
 
 UninterpretedOption_NamePart* UninterpretedOption_NamePart::default_instance_ = NULL;
 
-UninterpretedOption_NamePart* UninterpretedOption_NamePart::New() const {
-  return new UninterpretedOption_NamePart;
+UninterpretedOption_NamePart* UninterpretedOption_NamePart::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<UninterpretedOption_NamePart>(arena);
 }
 
 void UninterpretedOption_NamePart::Clear() {
   if (_has_bits_[0 / 32] & 3) {
     if (has_name_part()) {
-      if (name_part_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        name_part_->clear();
-      }
+      name_part_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     is_extension_ = false;
   }
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool UninterpretedOption_NamePart::MergePartialFromCodedStream(
@@ -7772,7 +8416,7 @@ bool UninterpretedOption_NamePart::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->name_part().data(), this->name_part().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "name_part");
+            "google.protobuf.UninterpretedOption.NamePart.name_part");
         } else {
           goto handle_unusual;
         }
@@ -7825,7 +8469,7 @@ void UninterpretedOption_NamePart::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name_part().data(), this->name_part().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name_part");
+      "google.protobuf.UninterpretedOption.NamePart.name_part");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       1, this->name_part(), output);
   }
@@ -7835,7 +8479,7 @@ void UninterpretedOption_NamePart::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormatLite::WriteBool(2, this->is_extension(), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -7850,7 +8494,7 @@ void UninterpretedOption_NamePart::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->name_part().data(), this->name_part().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "name_part");
+      "google.protobuf.UninterpretedOption.NamePart.name_part");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         1, this->name_part(), target);
@@ -7861,7 +8505,7 @@ void UninterpretedOption_NamePart::SerializeWithCachedSizes(
     target = ::google::protobuf::internal::WireFormatLite::WriteBoolToArray(2, this->is_extension(), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -7869,24 +8513,39 @@ void UninterpretedOption_NamePart::SerializeWithCachedSizes(
   return target;
 }
 
+int UninterpretedOption_NamePart::RequiredFieldsByteSizeFallback() const {
+  int total_size = 0;
+
+  if (has_name_part()) {
+    // required string name_part = 1;
+    total_size += 1 +
+      ::google::protobuf::internal::WireFormatLite::StringSize(
+        this->name_part());
+  }
+
+  if (has_is_extension()) {
+    // required bool is_extension = 2;
+    total_size += 1 + 1;
+  }
+
+  return total_size;
+}
 int UninterpretedOption_NamePart::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[0 / 32] & (0xffu << (0 % 32))) {
+  if (((_has_bits_[0] & 0x00000003) ^ 0x00000003) == 0) {  // All required fields are present.
     // required string name_part = 1;
-    if (has_name_part()) {
-      total_size += 1 +
-        ::google::protobuf::internal::WireFormatLite::StringSize(
-          this->name_part());
-    }
+    total_size += 1 +
+      ::google::protobuf::internal::WireFormatLite::StringSize(
+        this->name_part());
 
     // required bool is_extension = 2;
-    if (has_is_extension()) {
-      total_size += 1 + 1;
-    }
+    total_size += 1 + 1;
 
+  } else {
+    total_size += RequiredFieldsByteSizeFallback();
   }
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -7919,7 +8578,9 @@ void UninterpretedOption_NamePart::MergeFrom(const UninterpretedOption_NamePart&
       set_is_extension(from.is_extension());
     }
   }
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void UninterpretedOption_NamePart::CopyFrom(const ::google::protobuf::Message& from) {
@@ -7941,14 +8602,28 @@ bool UninterpretedOption_NamePart::IsInitialized() const {
 }
 
 void UninterpretedOption_NamePart::Swap(UninterpretedOption_NamePart* other) {
-  if (other != this) {
-    std::swap(name_part_, other->name_part_);
-    std::swap(is_extension_, other->is_extension_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    UninterpretedOption_NamePart temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void UninterpretedOption_NamePart::UnsafeArenaSwap(UninterpretedOption_NamePart* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void UninterpretedOption_NamePart::InternalSwap(UninterpretedOption_NamePart* other) {
+  name_part_.Swap(&other->name_part_);
+  std::swap(is_extension_, other->is_extension_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+}
 
 ::google::protobuf::Metadata UninterpretedOption_NamePart::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -7972,16 +8647,26 @@ const int UninterpretedOption::kAggregateValueFieldNumber;
 #endif  // !_MSC_VER
 
 UninterpretedOption::UninterpretedOption()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.UninterpretedOption)
 }
 
+UninterpretedOption::UninterpretedOption(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena),
+  name_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.UninterpretedOption)
+}
+
 void UninterpretedOption::InitAsDefaultInstance() {
 }
 
 UninterpretedOption::UninterpretedOption(const UninterpretedOption& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.UninterpretedOption)
@@ -7990,12 +8675,12 @@ UninterpretedOption::UninterpretedOption(const UninterpretedOption& from)
 void UninterpretedOption::SharedCtor() {
   ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
-  identifier_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  identifier_value_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   positive_int_value_ = GOOGLE_ULONGLONG(0);
   negative_int_value_ = GOOGLE_LONGLONG(0);
   double_value_ = 0;
-  string_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-  aggregate_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  string_value_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  aggregate_value_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
 
@@ -8005,19 +8690,23 @@ UninterpretedOption::~UninterpretedOption() {
 }
 
 void UninterpretedOption::SharedDtor() {
-  if (identifier_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete identifier_value_;
-  }
-  if (string_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete string_value_;
-  }
-  if (aggregate_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete aggregate_value_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
+  identifier_value_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+  string_value_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+  aggregate_value_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   if (this != default_instance_) {
   }
 }
 
+void UninterpretedOption::ArenaDtor(void* object) {
+  UninterpretedOption* _this = reinterpret_cast< UninterpretedOption* >(object);
+  (void)_this;
+}
+void UninterpretedOption::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void UninterpretedOption::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -8035,8 +8724,8 @@ const UninterpretedOption& UninterpretedOption::default_instance() {
 
 UninterpretedOption* UninterpretedOption::default_instance_ = NULL;
 
-UninterpretedOption* UninterpretedOption::New() const {
-  return new UninterpretedOption;
+UninterpretedOption* UninterpretedOption::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<UninterpretedOption>(arena);
 }
 
 void UninterpretedOption::Clear() {
@@ -8053,19 +8742,13 @@ void UninterpretedOption::Clear() {
   if (_has_bits_[0 / 32] & 126) {
     ZR_(positive_int_value_, double_value_);
     if (has_identifier_value()) {
-      if (identifier_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        identifier_value_->clear();
-      }
+      identifier_value_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     if (has_string_value()) {
-      if (string_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        string_value_->clear();
-      }
+      string_value_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     if (has_aggregate_value()) {
-      if (aggregate_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        aggregate_value_->clear();
-      }
+      aggregate_value_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
   }
 
@@ -8074,7 +8757,9 @@ void UninterpretedOption::Clear() {
 
   name_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool UninterpretedOption::MergePartialFromCodedStream(
@@ -8110,7 +8795,7 @@ bool UninterpretedOption::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->identifier_value().data(), this->identifier_value().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "identifier_value");
+            "google.protobuf.UninterpretedOption.identifier_value");
         } else {
           goto handle_unusual;
         }
@@ -8185,7 +8870,7 @@ bool UninterpretedOption::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->aggregate_value().data(), this->aggregate_value().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "aggregate_value");
+            "google.protobuf.UninterpretedOption.aggregate_value");
         } else {
           goto handle_unusual;
         }
@@ -8229,7 +8914,7 @@ void UninterpretedOption::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->identifier_value().data(), this->identifier_value().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "identifier_value");
+      "google.protobuf.UninterpretedOption.identifier_value");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       3, this->identifier_value(), output);
   }
@@ -8260,12 +8945,12 @@ void UninterpretedOption::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->aggregate_value().data(), this->aggregate_value().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "aggregate_value");
+      "google.protobuf.UninterpretedOption.aggregate_value");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       8, this->aggregate_value(), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -8287,7 +8972,7 @@ void UninterpretedOption::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->identifier_value().data(), this->identifier_value().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "identifier_value");
+      "google.protobuf.UninterpretedOption.identifier_value");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         3, this->identifier_value(), target);
@@ -8320,13 +9005,13 @@ void UninterpretedOption::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->aggregate_value().data(), this->aggregate_value().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "aggregate_value");
+      "google.protobuf.UninterpretedOption.aggregate_value");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         8, this->aggregate_value(), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -8337,7 +9022,7 @@ void UninterpretedOption::SerializeWithCachedSizes(
 int UninterpretedOption::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[1 / 32] & (0xffu << (1 % 32))) {
+  if (_has_bits_[1 / 32] & 126) {
     // optional string identifier_value = 3;
     if (has_identifier_value()) {
       total_size += 1 +
@@ -8387,7 +9072,7 @@ int UninterpretedOption::ByteSize() const {
         this->name(i));
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -8433,7 +9118,9 @@ void UninterpretedOption::MergeFrom(const UninterpretedOption& from) {
       set_aggregate_value(from.aggregate_value());
     }
   }
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void UninterpretedOption::CopyFrom(const ::google::protobuf::Message& from) {
@@ -8455,18 +9142,32 @@ bool UninterpretedOption::IsInitialized() const {
 }
 
 void UninterpretedOption::Swap(UninterpretedOption* other) {
-  if (other != this) {
-    name_.Swap(&other->name_);
-    std::swap(identifier_value_, other->identifier_value_);
-    std::swap(positive_int_value_, other->positive_int_value_);
-    std::swap(negative_int_value_, other->negative_int_value_);
-    std::swap(double_value_, other->double_value_);
-    std::swap(string_value_, other->string_value_);
-    std::swap(aggregate_value_, other->aggregate_value_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
-  }
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    UninterpretedOption temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
+  }
+}
+void UninterpretedOption::UnsafeArenaSwap(UninterpretedOption* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void UninterpretedOption::InternalSwap(UninterpretedOption* other) {
+  name_.UnsafeArenaSwap(&other->name_);
+  identifier_value_.Swap(&other->identifier_value_);
+  std::swap(positive_int_value_, other->positive_int_value_);
+  std::swap(negative_int_value_, other->negative_int_value_);
+  std::swap(double_value_, other->double_value_);
+  string_value_.Swap(&other->string_value_);
+  aggregate_value_.Swap(&other->aggregate_value_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
 }
 
 ::google::protobuf::Metadata UninterpretedOption::GetMetadata() const {
@@ -8488,16 +9189,27 @@ const int SourceCodeInfo_Location::kTrailingCommentsFieldNumber;
 #endif  // !_MSC_VER
 
 SourceCodeInfo_Location::SourceCodeInfo_Location()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.SourceCodeInfo.Location)
 }
 
+SourceCodeInfo_Location::SourceCodeInfo_Location(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena),
+  path_(arena),
+  span_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.SourceCodeInfo.Location)
+}
+
 void SourceCodeInfo_Location::InitAsDefaultInstance() {
 }
 
 SourceCodeInfo_Location::SourceCodeInfo_Location(const SourceCodeInfo_Location& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.SourceCodeInfo.Location)
@@ -8506,8 +9218,8 @@ SourceCodeInfo_Location::SourceCodeInfo_Location(const SourceCodeInfo_Location&
 void SourceCodeInfo_Location::SharedCtor() {
   ::google::protobuf::internal::GetEmptyString();
   _cached_size_ = 0;
-  leading_comments_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-  trailing_comments_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  leading_comments_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+  trailing_comments_.UnsafeSetDefault(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
 }
 
@@ -8517,16 +9229,22 @@ SourceCodeInfo_Location::~SourceCodeInfo_Location() {
 }
 
 void SourceCodeInfo_Location::SharedDtor() {
-  if (leading_comments_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete leading_comments_;
-  }
-  if (trailing_comments_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete trailing_comments_;
+  if (GetArenaNoVirtual() != NULL) {
+    return;
   }
+
+  leading_comments_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+  trailing_comments_.Destroy(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   if (this != default_instance_) {
   }
 }
 
+void SourceCodeInfo_Location::ArenaDtor(void* object) {
+  SourceCodeInfo_Location* _this = reinterpret_cast< SourceCodeInfo_Location* >(object);
+  (void)_this;
+}
+void SourceCodeInfo_Location::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void SourceCodeInfo_Location::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -8544,27 +9262,25 @@ const SourceCodeInfo_Location& SourceCodeInfo_Location::default_instance() {
 
 SourceCodeInfo_Location* SourceCodeInfo_Location::default_instance_ = NULL;
 
-SourceCodeInfo_Location* SourceCodeInfo_Location::New() const {
-  return new SourceCodeInfo_Location;
+SourceCodeInfo_Location* SourceCodeInfo_Location::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<SourceCodeInfo_Location>(arena);
 }
 
 void SourceCodeInfo_Location::Clear() {
   if (_has_bits_[0 / 32] & 12) {
     if (has_leading_comments()) {
-      if (leading_comments_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        leading_comments_->clear();
-      }
+      leading_comments_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
     if (has_trailing_comments()) {
-      if (trailing_comments_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-        trailing_comments_->clear();
-      }
+      trailing_comments_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
     }
   }
   path_.Clear();
   span_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool SourceCodeInfo_Location::MergePartialFromCodedStream(
@@ -8621,7 +9337,7 @@ bool SourceCodeInfo_Location::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->leading_comments().data(), this->leading_comments().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "leading_comments");
+            "google.protobuf.SourceCodeInfo.Location.leading_comments");
         } else {
           goto handle_unusual;
         }
@@ -8638,7 +9354,7 @@ bool SourceCodeInfo_Location::MergePartialFromCodedStream(
           ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
             this->trailing_comments().data(), this->trailing_comments().length(),
             ::google::protobuf::internal::WireFormat::PARSE,
-            "trailing_comments");
+            "google.protobuf.SourceCodeInfo.Location.trailing_comments");
         } else {
           goto handle_unusual;
         }
@@ -8696,7 +9412,7 @@ void SourceCodeInfo_Location::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->leading_comments().data(), this->leading_comments().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "leading_comments");
+      "google.protobuf.SourceCodeInfo.Location.leading_comments");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       3, this->leading_comments(), output);
   }
@@ -8706,12 +9422,12 @@ void SourceCodeInfo_Location::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->trailing_comments().data(), this->trailing_comments().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "trailing_comments");
+      "google.protobuf.SourceCodeInfo.Location.trailing_comments");
     ::google::protobuf::internal::WireFormatLite::WriteStringMaybeAliased(
       4, this->trailing_comments(), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -8754,7 +9470,7 @@ void SourceCodeInfo_Location::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->leading_comments().data(), this->leading_comments().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "leading_comments");
+      "google.protobuf.SourceCodeInfo.Location.leading_comments");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         3, this->leading_comments(), target);
@@ -8765,13 +9481,13 @@ void SourceCodeInfo_Location::SerializeWithCachedSizes(
     ::google::protobuf::internal::WireFormat::VerifyUTF8StringNamedField(
       this->trailing_comments().data(), this->trailing_comments().length(),
       ::google::protobuf::internal::WireFormat::SERIALIZE,
-      "trailing_comments");
+      "google.protobuf.SourceCodeInfo.Location.trailing_comments");
     target =
       ::google::protobuf::internal::WireFormatLite::WriteStringToArray(
         4, this->trailing_comments(), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -8782,7 +9498,7 @@ void SourceCodeInfo_Location::SerializeWithCachedSizes(
 int SourceCodeInfo_Location::ByteSize() const {
   int total_size = 0;
 
-  if (_has_bits_[2 / 32] & (0xffu << (2 % 32))) {
+  if (_has_bits_[2 / 32] & 12) {
     // optional string leading_comments = 3;
     if (has_leading_comments()) {
       total_size += 1 +
@@ -8832,7 +9548,7 @@ int SourceCodeInfo_Location::ByteSize() const {
     total_size += data_size;
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -8867,7 +9583,9 @@ void SourceCodeInfo_Location::MergeFrom(const SourceCodeInfo_Location& from) {
       set_trailing_comments(from.trailing_comments());
     }
   }
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void SourceCodeInfo_Location::CopyFrom(const ::google::protobuf::Message& from) {
@@ -8888,16 +9606,30 @@ bool SourceCodeInfo_Location::IsInitialized() const {
 }
 
 void SourceCodeInfo_Location::Swap(SourceCodeInfo_Location* other) {
-  if (other != this) {
-    path_.Swap(&other->path_);
-    span_.Swap(&other->span_);
-    std::swap(leading_comments_, other->leading_comments_);
-    std::swap(trailing_comments_, other->trailing_comments_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    SourceCodeInfo_Location temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
   }
 }
+void SourceCodeInfo_Location::UnsafeArenaSwap(SourceCodeInfo_Location* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void SourceCodeInfo_Location::InternalSwap(SourceCodeInfo_Location* other) {
+  path_.UnsafeArenaSwap(&other->path_);
+  span_.UnsafeArenaSwap(&other->span_);
+  leading_comments_.Swap(&other->leading_comments_);
+  trailing_comments_.Swap(&other->trailing_comments_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
+}
 
 ::google::protobuf::Metadata SourceCodeInfo_Location::GetMetadata() const {
   protobuf_AssignDescriptorsOnce();
@@ -8915,16 +9647,26 @@ const int SourceCodeInfo::kLocationFieldNumber;
 #endif  // !_MSC_VER
 
 SourceCodeInfo::SourceCodeInfo()
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message() , _internal_metadata_(NULL)  {
   SharedCtor();
   // @@protoc_insertion_point(constructor:google.protobuf.SourceCodeInfo)
 }
 
+SourceCodeInfo::SourceCodeInfo(::google::protobuf::Arena* arena)
+  : ::google::protobuf::Message(),
+  _internal_metadata_(arena),
+  location_(arena) {
+  SharedCtor();
+  RegisterArenaDtor(arena);
+  // @@protoc_insertion_point(arena_constructor:google.protobuf.SourceCodeInfo)
+}
+
 void SourceCodeInfo::InitAsDefaultInstance() {
 }
 
 SourceCodeInfo::SourceCodeInfo(const SourceCodeInfo& from)
-  : ::google::protobuf::Message() {
+  : ::google::protobuf::Message(),
+    _internal_metadata_(NULL) {
   SharedCtor();
   MergeFrom(from);
   // @@protoc_insertion_point(copy_constructor:google.protobuf.SourceCodeInfo)
@@ -8941,10 +9683,20 @@ SourceCodeInfo::~SourceCodeInfo() {
 }
 
 void SourceCodeInfo::SharedDtor() {
+  if (GetArenaNoVirtual() != NULL) {
+    return;
+  }
+
   if (this != default_instance_) {
   }
 }
 
+void SourceCodeInfo::ArenaDtor(void* object) {
+  SourceCodeInfo* _this = reinterpret_cast< SourceCodeInfo* >(object);
+  (void)_this;
+}
+void SourceCodeInfo::RegisterArenaDtor(::google::protobuf::Arena* arena) {
+}
 void SourceCodeInfo::SetCachedSize(int size) const {
   GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();
   _cached_size_ = size;
@@ -8962,14 +9714,16 @@ const SourceCodeInfo& SourceCodeInfo::default_instance() {
 
 SourceCodeInfo* SourceCodeInfo::default_instance_ = NULL;
 
-SourceCodeInfo* SourceCodeInfo::New() const {
-  return new SourceCodeInfo;
+SourceCodeInfo* SourceCodeInfo::New(::google::protobuf::Arena* arena) const {
+  return ::google::protobuf::Arena::CreateMessage<SourceCodeInfo>(arena);
 }
 
 void SourceCodeInfo::Clear() {
   location_.Clear();
   ::memset(_has_bits_, 0, sizeof(_has_bits_));
-  mutable_unknown_fields()->Clear();
+  if (_internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->Clear();
+  }
 }
 
 bool SourceCodeInfo::MergePartialFromCodedStream(
@@ -9027,7 +9781,7 @@ void SourceCodeInfo::SerializeWithCachedSizes(
       1, this->location(i), output);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     ::google::protobuf::internal::WireFormat::SerializeUnknownFields(
         unknown_fields(), output);
   }
@@ -9044,7 +9798,7 @@ void SourceCodeInfo::SerializeWithCachedSizes(
         1, this->location(i), target);
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     target = ::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(
         unknown_fields(), target);
   }
@@ -9063,7 +9817,7 @@ int SourceCodeInfo::ByteSize() const {
         this->location(i));
   }
 
-  if (!unknown_fields().empty()) {
+  if (_internal_metadata_.have_unknown_fields()) {
     total_size +=
       ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(
         unknown_fields());
@@ -9089,7 +9843,9 @@ void SourceCodeInfo::MergeFrom(const ::google::protobuf::Message& from) {
 void SourceCodeInfo::MergeFrom(const SourceCodeInfo& from) {
   GOOGLE_CHECK_NE(&from, this);
   location_.MergeFrom(from.location_);
-  mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  if (from._internal_metadata_.have_unknown_fields()) {
+    mutable_unknown_fields()->MergeFrom(from.unknown_fields());
+  }
 }
 
 void SourceCodeInfo::CopyFrom(const ::google::protobuf::Message& from) {
@@ -9110,12 +9866,26 @@ bool SourceCodeInfo::IsInitialized() const {
 }
 
 void SourceCodeInfo::Swap(SourceCodeInfo* other) {
-  if (other != this) {
-    location_.Swap(&other->location_);
-    std::swap(_has_bits_[0], other->_has_bits_[0]);
-    _unknown_fields_.Swap(&other->_unknown_fields_);
-    std::swap(_cached_size_, other->_cached_size_);
-  }
+  if (other == this) return;
+  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    SourceCodeInfo temp;
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->CopyFrom(temp);
+  }
+}
+void SourceCodeInfo::UnsafeArenaSwap(SourceCodeInfo* other) {
+  if (other == this) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
+}
+void SourceCodeInfo::InternalSwap(SourceCodeInfo* other) {
+  location_.UnsafeArenaSwap(&other->location_);
+  std::swap(_has_bits_[0], other->_has_bits_[0]);
+  _internal_metadata_.Swap(&other->_internal_metadata_);
+  std::swap(_cached_size_, other->_cached_size_);
 }
 
 ::google::protobuf::Metadata SourceCodeInfo::GetMetadata() const {
diff --git a/src/google/protobuf/descriptor.pb.h b/src/google/protobuf/descriptor.pb.h
index dd721be9..295b53f3 100644
--- a/src/google/protobuf/descriptor.pb.h
+++ b/src/google/protobuf/descriptor.pb.h
@@ -5,6 +5,7 @@
 #define PROTOBUF_google_2fprotobuf_2fdescriptor_2eproto__INCLUDED
 
 #include <string>
+#include <stdint.h>
 
 #include <google/protobuf/stubs/common.h>
 
@@ -19,7 +20,10 @@
 #error regenerate this file with a newer version of protoc.
 #endif
 
+#include <google/protobuf/arena.h>
+#include <google/protobuf/arenastring.h>
 #include <google/protobuf/generated_message_util.h>
+#include <google/protobuf/metadata.h>
 #include <google/protobuf/message.h>
 #include <google/protobuf/repeated_field.h>
 #include <google/protobuf/extension_set.h>
@@ -167,21 +171,28 @@ class LIBPROTOBUF_EXPORT FileDescriptorSet : public ::google::protobuf::Message
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const FileDescriptorSet& default_instance();
 
+  void UnsafeArenaSwap(FileDescriptorSet* other);
   void Swap(FileDescriptorSet* other);
 
   // implements Message ----------------------------------------------
 
-  FileDescriptorSet* New() const;
+  inline FileDescriptorSet* New() const { return New(NULL); }
+
+  FileDescriptorSet* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const FileDescriptorSet& from);
@@ -200,7 +211,21 @@ class LIBPROTOBUF_EXPORT FileDescriptorSet : public ::google::protobuf::Message
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(FileDescriptorSet* other);
+  protected:
+  explicit FileDescriptorSet(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -222,8 +247,10 @@ class LIBPROTOBUF_EXPORT FileDescriptorSet : public ::google::protobuf::Message
   // @@protoc_insertion_point(class_scope:google.protobuf.FileDescriptorSet)
  private:
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::FileDescriptorProto > file_;
@@ -249,21 +276,28 @@ class LIBPROTOBUF_EXPORT FileDescriptorProto : public ::google::protobuf::Messag
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const FileDescriptorProto& default_instance();
 
+  void UnsafeArenaSwap(FileDescriptorProto* other);
   void Swap(FileDescriptorProto* other);
 
   // implements Message ----------------------------------------------
 
-  FileDescriptorProto* New() const;
+  inline FileDescriptorProto* New() const { return New(NULL); }
+
+  FileDescriptorProto* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const FileDescriptorProto& from);
@@ -282,7 +316,21 @@ class LIBPROTOBUF_EXPORT FileDescriptorProto : public ::google::protobuf::Messag
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(FileDescriptorProto* other);
+  protected:
+  explicit FileDescriptorProto(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -300,6 +348,9 @@ class LIBPROTOBUF_EXPORT FileDescriptorProto : public ::google::protobuf::Messag
   inline ::std::string* mutable_name();
   inline ::std::string* release_name();
   inline void set_allocated_name(::std::string* name);
+  inline ::std::string* unsafe_arena_release_name();
+  inline void unsafe_arena_set_allocated_name(
+      ::std::string* name);
 
   // optional string package = 2;
   inline bool has_package() const;
@@ -312,6 +363,9 @@ class LIBPROTOBUF_EXPORT FileDescriptorProto : public ::google::protobuf::Messag
   inline ::std::string* mutable_package();
   inline ::std::string* release_package();
   inline void set_allocated_package(::std::string* package);
+  inline ::std::string* unsafe_arena_release_package();
+  inline void unsafe_arena_set_allocated_package(
+      ::std::string* package);
 
   // repeated string dependency = 3;
   inline int dependency_size() const;
@@ -409,6 +463,9 @@ class LIBPROTOBUF_EXPORT FileDescriptorProto : public ::google::protobuf::Messag
   inline ::google::protobuf::FileOptions* mutable_options();
   inline ::google::protobuf::FileOptions* release_options();
   inline void set_allocated_options(::google::protobuf::FileOptions* options);
+  inline ::google::protobuf::FileOptions* unsafe_arena_release_options();
+  inline void unsafe_arena_set_allocated_options(
+      ::google::protobuf::FileOptions* options);
 
   // optional .google.protobuf.SourceCodeInfo source_code_info = 9;
   inline bool has_source_code_info() const;
@@ -418,6 +475,24 @@ class LIBPROTOBUF_EXPORT FileDescriptorProto : public ::google::protobuf::Messag
   inline ::google::protobuf::SourceCodeInfo* mutable_source_code_info();
   inline ::google::protobuf::SourceCodeInfo* release_source_code_info();
   inline void set_allocated_source_code_info(::google::protobuf::SourceCodeInfo* source_code_info);
+  inline ::google::protobuf::SourceCodeInfo* unsafe_arena_release_source_code_info();
+  inline void unsafe_arena_set_allocated_source_code_info(
+      ::google::protobuf::SourceCodeInfo* source_code_info);
+
+  // optional string syntax = 12;
+  inline bool has_syntax() const;
+  inline void clear_syntax();
+  static const int kSyntaxFieldNumber = 12;
+  inline const ::std::string& syntax() const;
+  inline void set_syntax(const ::std::string& value);
+  inline void set_syntax(const char* value);
+  inline void set_syntax(const char* value, size_t size);
+  inline ::std::string* mutable_syntax();
+  inline ::std::string* release_syntax();
+  inline void set_allocated_syntax(::std::string* syntax);
+  inline ::std::string* unsafe_arena_release_syntax();
+  inline void unsafe_arena_set_allocated_syntax(
+      ::std::string* syntax);
 
   // @@protoc_insertion_point(class_scope:google.protobuf.FileDescriptorProto)
  private:
@@ -429,13 +504,17 @@ class LIBPROTOBUF_EXPORT FileDescriptorProto : public ::google::protobuf::Messag
   inline void clear_has_options();
   inline void set_has_source_code_info();
   inline void clear_has_source_code_info();
+  inline void set_has_syntax();
+  inline void clear_has_syntax();
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
-  ::std::string* name_;
-  ::std::string* package_;
+  ::google::protobuf::internal::ArenaStringPtr name_;
+  ::google::protobuf::internal::ArenaStringPtr package_;
   ::google::protobuf::RepeatedPtrField< ::std::string> dependency_;
   ::google::protobuf::RepeatedField< ::google::protobuf::int32 > public_dependency_;
   ::google::protobuf::RepeatedField< ::google::protobuf::int32 > weak_dependency_;
@@ -445,6 +524,7 @@ class LIBPROTOBUF_EXPORT FileDescriptorProto : public ::google::protobuf::Messag
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::FieldDescriptorProto > extension_;
   ::google::protobuf::FileOptions* options_;
   ::google::protobuf::SourceCodeInfo* source_code_info_;
+  ::google::protobuf::internal::ArenaStringPtr syntax_;
   friend void LIBPROTOBUF_EXPORT protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_ShutdownFile_google_2fprotobuf_2fdescriptor_2eproto();
@@ -467,21 +547,28 @@ class LIBPROTOBUF_EXPORT DescriptorProto_ExtensionRange : public ::google::proto
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const DescriptorProto_ExtensionRange& default_instance();
 
+  void UnsafeArenaSwap(DescriptorProto_ExtensionRange* other);
   void Swap(DescriptorProto_ExtensionRange* other);
 
   // implements Message ----------------------------------------------
 
-  DescriptorProto_ExtensionRange* New() const;
+  inline DescriptorProto_ExtensionRange* New() const { return New(NULL); }
+
+  DescriptorProto_ExtensionRange* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const DescriptorProto_ExtensionRange& from);
@@ -500,7 +587,21 @@ class LIBPROTOBUF_EXPORT DescriptorProto_ExtensionRange : public ::google::proto
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(DescriptorProto_ExtensionRange* other);
+  protected:
+  explicit DescriptorProto_ExtensionRange(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -528,8 +629,10 @@ class LIBPROTOBUF_EXPORT DescriptorProto_ExtensionRange : public ::google::proto
   inline void set_has_end();
   inline void clear_has_end();
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
   ::google::protobuf::int32 start_;
@@ -556,21 +659,28 @@ class LIBPROTOBUF_EXPORT DescriptorProto : public ::google::protobuf::Message {
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const DescriptorProto& default_instance();
 
+  void UnsafeArenaSwap(DescriptorProto* other);
   void Swap(DescriptorProto* other);
 
   // implements Message ----------------------------------------------
 
-  DescriptorProto* New() const;
+  inline DescriptorProto* New() const { return New(NULL); }
+
+  DescriptorProto* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const DescriptorProto& from);
@@ -589,7 +699,21 @@ class LIBPROTOBUF_EXPORT DescriptorProto : public ::google::protobuf::Message {
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(DescriptorProto* other);
+  protected:
+  explicit DescriptorProto(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -609,6 +733,9 @@ class LIBPROTOBUF_EXPORT DescriptorProto : public ::google::protobuf::Message {
   inline ::std::string* mutable_name();
   inline ::std::string* release_name();
   inline void set_allocated_name(::std::string* name);
+  inline ::std::string* unsafe_arena_release_name();
+  inline void unsafe_arena_set_allocated_name(
+      ::std::string* name);
 
   // repeated .google.protobuf.FieldDescriptorProto field = 2;
   inline int field_size() const;
@@ -690,6 +817,9 @@ class LIBPROTOBUF_EXPORT DescriptorProto : public ::google::protobuf::Message {
   inline ::google::protobuf::MessageOptions* mutable_options();
   inline ::google::protobuf::MessageOptions* release_options();
   inline void set_allocated_options(::google::protobuf::MessageOptions* options);
+  inline ::google::protobuf::MessageOptions* unsafe_arena_release_options();
+  inline void unsafe_arena_set_allocated_options(
+      ::google::protobuf::MessageOptions* options);
 
   // @@protoc_insertion_point(class_scope:google.protobuf.DescriptorProto)
  private:
@@ -698,11 +828,13 @@ class LIBPROTOBUF_EXPORT DescriptorProto : public ::google::protobuf::Message {
   inline void set_has_options();
   inline void clear_has_options();
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
-  ::std::string* name_;
+  ::google::protobuf::internal::ArenaStringPtr name_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::FieldDescriptorProto > field_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::FieldDescriptorProto > extension_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::DescriptorProto > nested_type_;
@@ -732,21 +864,28 @@ class LIBPROTOBUF_EXPORT FieldDescriptorProto : public ::google::protobuf::Messa
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const FieldDescriptorProto& default_instance();
 
+  void UnsafeArenaSwap(FieldDescriptorProto* other);
   void Swap(FieldDescriptorProto* other);
 
   // implements Message ----------------------------------------------
 
-  FieldDescriptorProto* New() const;
+  inline FieldDescriptorProto* New() const { return New(NULL); }
+
+  FieldDescriptorProto* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const FieldDescriptorProto& from);
@@ -765,7 +904,21 @@ class LIBPROTOBUF_EXPORT FieldDescriptorProto : public ::google::protobuf::Messa
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(FieldDescriptorProto* other);
+  protected:
+  explicit FieldDescriptorProto(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -848,6 +1001,9 @@ class LIBPROTOBUF_EXPORT FieldDescriptorProto : public ::google::protobuf::Messa
   inline ::std::string* mutable_name();
   inline ::std::string* release_name();
   inline void set_allocated_name(::std::string* name);
+  inline ::std::string* unsafe_arena_release_name();
+  inline void unsafe_arena_set_allocated_name(
+      ::std::string* name);
 
   // optional int32 number = 3;
   inline bool has_number() const;
@@ -881,6 +1037,9 @@ class LIBPROTOBUF_EXPORT FieldDescriptorProto : public ::google::protobuf::Messa
   inline ::std::string* mutable_type_name();
   inline ::std::string* release_type_name();
   inline void set_allocated_type_name(::std::string* type_name);
+  inline ::std::string* unsafe_arena_release_type_name();
+  inline void unsafe_arena_set_allocated_type_name(
+      ::std::string* type_name);
 
   // optional string extendee = 2;
   inline bool has_extendee() const;
@@ -893,6 +1052,9 @@ class LIBPROTOBUF_EXPORT FieldDescriptorProto : public ::google::protobuf::Messa
   inline ::std::string* mutable_extendee();
   inline ::std::string* release_extendee();
   inline void set_allocated_extendee(::std::string* extendee);
+  inline ::std::string* unsafe_arena_release_extendee();
+  inline void unsafe_arena_set_allocated_extendee(
+      ::std::string* extendee);
 
   // optional string default_value = 7;
   inline bool has_default_value() const;
@@ -905,6 +1067,9 @@ class LIBPROTOBUF_EXPORT FieldDescriptorProto : public ::google::protobuf::Messa
   inline ::std::string* mutable_default_value();
   inline ::std::string* release_default_value();
   inline void set_allocated_default_value(::std::string* default_value);
+  inline ::std::string* unsafe_arena_release_default_value();
+  inline void unsafe_arena_set_allocated_default_value(
+      ::std::string* default_value);
 
   // optional int32 oneof_index = 9;
   inline bool has_oneof_index() const;
@@ -921,6 +1086,9 @@ class LIBPROTOBUF_EXPORT FieldDescriptorProto : public ::google::protobuf::Messa
   inline ::google::protobuf::FieldOptions* mutable_options();
   inline ::google::protobuf::FieldOptions* release_options();
   inline void set_allocated_options(::google::protobuf::FieldOptions* options);
+  inline ::google::protobuf::FieldOptions* unsafe_arena_release_options();
+  inline void unsafe_arena_set_allocated_options(
+      ::google::protobuf::FieldOptions* options);
 
   // @@protoc_insertion_point(class_scope:google.protobuf.FieldDescriptorProto)
  private:
@@ -943,18 +1111,20 @@ class LIBPROTOBUF_EXPORT FieldDescriptorProto : public ::google::protobuf::Messa
   inline void set_has_options();
   inline void clear_has_options();
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
-  ::std::string* name_;
+  ::google::protobuf::internal::ArenaStringPtr name_;
   ::google::protobuf::int32 number_;
   int label_;
-  ::std::string* type_name_;
-  ::std::string* extendee_;
+  ::google::protobuf::internal::ArenaStringPtr type_name_;
+  ::google::protobuf::internal::ArenaStringPtr extendee_;
   int type_;
   ::google::protobuf::int32 oneof_index_;
-  ::std::string* default_value_;
+  ::google::protobuf::internal::ArenaStringPtr default_value_;
   ::google::protobuf::FieldOptions* options_;
   friend void LIBPROTOBUF_EXPORT protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto();
@@ -978,21 +1148,28 @@ class LIBPROTOBUF_EXPORT OneofDescriptorProto : public ::google::protobuf::Messa
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const OneofDescriptorProto& default_instance();
 
+  void UnsafeArenaSwap(OneofDescriptorProto* other);
   void Swap(OneofDescriptorProto* other);
 
   // implements Message ----------------------------------------------
 
-  OneofDescriptorProto* New() const;
+  inline OneofDescriptorProto* New() const { return New(NULL); }
+
+  OneofDescriptorProto* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const OneofDescriptorProto& from);
@@ -1011,7 +1188,21 @@ class LIBPROTOBUF_EXPORT OneofDescriptorProto : public ::google::protobuf::Messa
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(OneofDescriptorProto* other);
+  protected:
+  explicit OneofDescriptorProto(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -1029,17 +1220,22 @@ class LIBPROTOBUF_EXPORT OneofDescriptorProto : public ::google::protobuf::Messa
   inline ::std::string* mutable_name();
   inline ::std::string* release_name();
   inline void set_allocated_name(::std::string* name);
+  inline ::std::string* unsafe_arena_release_name();
+  inline void unsafe_arena_set_allocated_name(
+      ::std::string* name);
 
   // @@protoc_insertion_point(class_scope:google.protobuf.OneofDescriptorProto)
  private:
   inline void set_has_name();
   inline void clear_has_name();
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
-  ::std::string* name_;
+  ::google::protobuf::internal::ArenaStringPtr name_;
   friend void LIBPROTOBUF_EXPORT protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_ShutdownFile_google_2fprotobuf_2fdescriptor_2eproto();
@@ -1062,21 +1258,28 @@ class LIBPROTOBUF_EXPORT EnumDescriptorProto : public ::google::protobuf::Messag
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const EnumDescriptorProto& default_instance();
 
+  void UnsafeArenaSwap(EnumDescriptorProto* other);
   void Swap(EnumDescriptorProto* other);
 
   // implements Message ----------------------------------------------
 
-  EnumDescriptorProto* New() const;
+  inline EnumDescriptorProto* New() const { return New(NULL); }
+
+  EnumDescriptorProto* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const EnumDescriptorProto& from);
@@ -1095,7 +1298,21 @@ class LIBPROTOBUF_EXPORT EnumDescriptorProto : public ::google::protobuf::Messag
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(EnumDescriptorProto* other);
+  protected:
+  explicit EnumDescriptorProto(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -1113,6 +1330,9 @@ class LIBPROTOBUF_EXPORT EnumDescriptorProto : public ::google::protobuf::Messag
   inline ::std::string* mutable_name();
   inline ::std::string* release_name();
   inline void set_allocated_name(::std::string* name);
+  inline ::std::string* unsafe_arena_release_name();
+  inline void unsafe_arena_set_allocated_name(
+      ::std::string* name);
 
   // repeated .google.protobuf.EnumValueDescriptorProto value = 2;
   inline int value_size() const;
@@ -1134,6 +1354,9 @@ class LIBPROTOBUF_EXPORT EnumDescriptorProto : public ::google::protobuf::Messag
   inline ::google::protobuf::EnumOptions* mutable_options();
   inline ::google::protobuf::EnumOptions* release_options();
   inline void set_allocated_options(::google::protobuf::EnumOptions* options);
+  inline ::google::protobuf::EnumOptions* unsafe_arena_release_options();
+  inline void unsafe_arena_set_allocated_options(
+      ::google::protobuf::EnumOptions* options);
 
   // @@protoc_insertion_point(class_scope:google.protobuf.EnumDescriptorProto)
  private:
@@ -1142,11 +1365,13 @@ class LIBPROTOBUF_EXPORT EnumDescriptorProto : public ::google::protobuf::Messag
   inline void set_has_options();
   inline void clear_has_options();
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
-  ::std::string* name_;
+  ::google::protobuf::internal::ArenaStringPtr name_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::EnumValueDescriptorProto > value_;
   ::google::protobuf::EnumOptions* options_;
   friend void LIBPROTOBUF_EXPORT protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto();
@@ -1171,21 +1396,28 @@ class LIBPROTOBUF_EXPORT EnumValueDescriptorProto : public ::google::protobuf::M
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const EnumValueDescriptorProto& default_instance();
 
+  void UnsafeArenaSwap(EnumValueDescriptorProto* other);
   void Swap(EnumValueDescriptorProto* other);
 
   // implements Message ----------------------------------------------
 
-  EnumValueDescriptorProto* New() const;
+  inline EnumValueDescriptorProto* New() const { return New(NULL); }
+
+  EnumValueDescriptorProto* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const EnumValueDescriptorProto& from);
@@ -1204,7 +1436,21 @@ class LIBPROTOBUF_EXPORT EnumValueDescriptorProto : public ::google::protobuf::M
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(EnumValueDescriptorProto* other);
+  protected:
+  explicit EnumValueDescriptorProto(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -1222,6 +1468,9 @@ class LIBPROTOBUF_EXPORT EnumValueDescriptorProto : public ::google::protobuf::M
   inline ::std::string* mutable_name();
   inline ::std::string* release_name();
   inline void set_allocated_name(::std::string* name);
+  inline ::std::string* unsafe_arena_release_name();
+  inline void unsafe_arena_set_allocated_name(
+      ::std::string* name);
 
   // optional int32 number = 2;
   inline bool has_number() const;
@@ -1238,6 +1487,9 @@ class LIBPROTOBUF_EXPORT EnumValueDescriptorProto : public ::google::protobuf::M
   inline ::google::protobuf::EnumValueOptions* mutable_options();
   inline ::google::protobuf::EnumValueOptions* release_options();
   inline void set_allocated_options(::google::protobuf::EnumValueOptions* options);
+  inline ::google::protobuf::EnumValueOptions* unsafe_arena_release_options();
+  inline void unsafe_arena_set_allocated_options(
+      ::google::protobuf::EnumValueOptions* options);
 
   // @@protoc_insertion_point(class_scope:google.protobuf.EnumValueDescriptorProto)
  private:
@@ -1248,11 +1500,13 @@ class LIBPROTOBUF_EXPORT EnumValueDescriptorProto : public ::google::protobuf::M
   inline void set_has_options();
   inline void clear_has_options();
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
-  ::std::string* name_;
+  ::google::protobuf::internal::ArenaStringPtr name_;
   ::google::protobuf::EnumValueOptions* options_;
   ::google::protobuf::int32 number_;
   friend void LIBPROTOBUF_EXPORT protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto();
@@ -1277,21 +1531,28 @@ class LIBPROTOBUF_EXPORT ServiceDescriptorProto : public ::google::protobuf::Mes
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const ServiceDescriptorProto& default_instance();
 
+  void UnsafeArenaSwap(ServiceDescriptorProto* other);
   void Swap(ServiceDescriptorProto* other);
 
   // implements Message ----------------------------------------------
 
-  ServiceDescriptorProto* New() const;
+  inline ServiceDescriptorProto* New() const { return New(NULL); }
+
+  ServiceDescriptorProto* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const ServiceDescriptorProto& from);
@@ -1310,7 +1571,21 @@ class LIBPROTOBUF_EXPORT ServiceDescriptorProto : public ::google::protobuf::Mes
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(ServiceDescriptorProto* other);
+  protected:
+  explicit ServiceDescriptorProto(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -1328,6 +1603,9 @@ class LIBPROTOBUF_EXPORT ServiceDescriptorProto : public ::google::protobuf::Mes
   inline ::std::string* mutable_name();
   inline ::std::string* release_name();
   inline void set_allocated_name(::std::string* name);
+  inline ::std::string* unsafe_arena_release_name();
+  inline void unsafe_arena_set_allocated_name(
+      ::std::string* name);
 
   // repeated .google.protobuf.MethodDescriptorProto method = 2;
   inline int method_size() const;
@@ -1349,6 +1627,9 @@ class LIBPROTOBUF_EXPORT ServiceDescriptorProto : public ::google::protobuf::Mes
   inline ::google::protobuf::ServiceOptions* mutable_options();
   inline ::google::protobuf::ServiceOptions* release_options();
   inline void set_allocated_options(::google::protobuf::ServiceOptions* options);
+  inline ::google::protobuf::ServiceOptions* unsafe_arena_release_options();
+  inline void unsafe_arena_set_allocated_options(
+      ::google::protobuf::ServiceOptions* options);
 
   // @@protoc_insertion_point(class_scope:google.protobuf.ServiceDescriptorProto)
  private:
@@ -1357,11 +1638,13 @@ class LIBPROTOBUF_EXPORT ServiceDescriptorProto : public ::google::protobuf::Mes
   inline void set_has_options();
   inline void clear_has_options();
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
-  ::std::string* name_;
+  ::google::protobuf::internal::ArenaStringPtr name_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::MethodDescriptorProto > method_;
   ::google::protobuf::ServiceOptions* options_;
   friend void LIBPROTOBUF_EXPORT protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto();
@@ -1386,21 +1669,28 @@ class LIBPROTOBUF_EXPORT MethodDescriptorProto : public ::google::protobuf::Mess
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const MethodDescriptorProto& default_instance();
 
+  void UnsafeArenaSwap(MethodDescriptorProto* other);
   void Swap(MethodDescriptorProto* other);
 
   // implements Message ----------------------------------------------
 
-  MethodDescriptorProto* New() const;
+  inline MethodDescriptorProto* New() const { return New(NULL); }
+
+  MethodDescriptorProto* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const MethodDescriptorProto& from);
@@ -1419,7 +1709,21 @@ class LIBPROTOBUF_EXPORT MethodDescriptorProto : public ::google::protobuf::Mess
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(MethodDescriptorProto* other);
+  protected:
+  explicit MethodDescriptorProto(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -1437,6 +1741,9 @@ class LIBPROTOBUF_EXPORT MethodDescriptorProto : public ::google::protobuf::Mess
   inline ::std::string* mutable_name();
   inline ::std::string* release_name();
   inline void set_allocated_name(::std::string* name);
+  inline ::std::string* unsafe_arena_release_name();
+  inline void unsafe_arena_set_allocated_name(
+      ::std::string* name);
 
   // optional string input_type = 2;
   inline bool has_input_type() const;
@@ -1449,6 +1756,9 @@ class LIBPROTOBUF_EXPORT MethodDescriptorProto : public ::google::protobuf::Mess
   inline ::std::string* mutable_input_type();
   inline ::std::string* release_input_type();
   inline void set_allocated_input_type(::std::string* input_type);
+  inline ::std::string* unsafe_arena_release_input_type();
+  inline void unsafe_arena_set_allocated_input_type(
+      ::std::string* input_type);
 
   // optional string output_type = 3;
   inline bool has_output_type() const;
@@ -1461,6 +1771,9 @@ class LIBPROTOBUF_EXPORT MethodDescriptorProto : public ::google::protobuf::Mess
   inline ::std::string* mutable_output_type();
   inline ::std::string* release_output_type();
   inline void set_allocated_output_type(::std::string* output_type);
+  inline ::std::string* unsafe_arena_release_output_type();
+  inline void unsafe_arena_set_allocated_output_type(
+      ::std::string* output_type);
 
   // optional .google.protobuf.MethodOptions options = 4;
   inline bool has_options() const;
@@ -1470,6 +1783,9 @@ class LIBPROTOBUF_EXPORT MethodDescriptorProto : public ::google::protobuf::Mess
   inline ::google::protobuf::MethodOptions* mutable_options();
   inline ::google::protobuf::MethodOptions* release_options();
   inline void set_allocated_options(::google::protobuf::MethodOptions* options);
+  inline ::google::protobuf::MethodOptions* unsafe_arena_release_options();
+  inline void unsafe_arena_set_allocated_options(
+      ::google::protobuf::MethodOptions* options);
 
   // @@protoc_insertion_point(class_scope:google.protobuf.MethodDescriptorProto)
  private:
@@ -1482,13 +1798,15 @@ class LIBPROTOBUF_EXPORT MethodDescriptorProto : public ::google::protobuf::Mess
   inline void set_has_options();
   inline void clear_has_options();
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
-  ::std::string* name_;
-  ::std::string* input_type_;
-  ::std::string* output_type_;
+  ::google::protobuf::internal::ArenaStringPtr name_;
+  ::google::protobuf::internal::ArenaStringPtr input_type_;
+  ::google::protobuf::internal::ArenaStringPtr output_type_;
   ::google::protobuf::MethodOptions* options_;
   friend void LIBPROTOBUF_EXPORT protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto();
@@ -1512,21 +1830,28 @@ class LIBPROTOBUF_EXPORT FileOptions : public ::google::protobuf::Message {
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const FileOptions& default_instance();
 
+  void UnsafeArenaSwap(FileOptions* other);
   void Swap(FileOptions* other);
 
   // implements Message ----------------------------------------------
 
-  FileOptions* New() const;
+  inline FileOptions* New() const { return New(NULL); }
+
+  FileOptions* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const FileOptions& from);
@@ -1545,7 +1870,21 @@ class LIBPROTOBUF_EXPORT FileOptions : public ::google::protobuf::Message {
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(FileOptions* other);
+  protected:
+  explicit FileOptions(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -1588,6 +1927,9 @@ class LIBPROTOBUF_EXPORT FileOptions : public ::google::protobuf::Message {
   inline ::std::string* mutable_java_package();
   inline ::std::string* release_java_package();
   inline void set_allocated_java_package(::std::string* java_package);
+  inline ::std::string* unsafe_arena_release_java_package();
+  inline void unsafe_arena_set_allocated_java_package(
+      ::std::string* java_package);
 
   // optional string java_outer_classname = 8;
   inline bool has_java_outer_classname() const;
@@ -1600,6 +1942,9 @@ class LIBPROTOBUF_EXPORT FileOptions : public ::google::protobuf::Message {
   inline ::std::string* mutable_java_outer_classname();
   inline ::std::string* release_java_outer_classname();
   inline void set_allocated_java_outer_classname(::std::string* java_outer_classname);
+  inline ::std::string* unsafe_arena_release_java_outer_classname();
+  inline void unsafe_arena_set_allocated_java_outer_classname(
+      ::std::string* java_outer_classname);
 
   // optional bool java_multiple_files = 10 [default = false];
   inline bool has_java_multiple_files() const;
@@ -1640,6 +1985,9 @@ class LIBPROTOBUF_EXPORT FileOptions : public ::google::protobuf::Message {
   inline ::std::string* mutable_go_package();
   inline ::std::string* release_go_package();
   inline void set_allocated_go_package(::std::string* go_package);
+  inline ::std::string* unsafe_arena_release_go_package();
+  inline void unsafe_arena_set_allocated_go_package(
+      ::std::string* go_package);
 
   // optional bool cc_generic_services = 16 [default = false];
   inline bool has_cc_generic_services() const;
@@ -1709,18 +2057,20 @@ class LIBPROTOBUF_EXPORT FileOptions : public ::google::protobuf::Message {
 
   ::google::protobuf::internal::ExtensionSet _extensions_;
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
-  ::std::string* java_package_;
-  ::std::string* java_outer_classname_;
+  ::google::protobuf::internal::ArenaStringPtr java_package_;
+  ::google::protobuf::internal::ArenaStringPtr java_outer_classname_;
   bool java_multiple_files_;
   bool java_generate_equals_and_hash_;
   bool java_string_check_utf8_;
   bool cc_generic_services_;
   int optimize_for_;
-  ::std::string* go_package_;
+  ::google::protobuf::internal::ArenaStringPtr go_package_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::UninterpretedOption > uninterpreted_option_;
   bool java_generic_services_;
   bool py_generic_services_;
@@ -1747,21 +2097,28 @@ class LIBPROTOBUF_EXPORT MessageOptions : public ::google::protobuf::Message {
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const MessageOptions& default_instance();
 
+  void UnsafeArenaSwap(MessageOptions* other);
   void Swap(MessageOptions* other);
 
   // implements Message ----------------------------------------------
 
-  MessageOptions* New() const;
+  inline MessageOptions* New() const { return New(NULL); }
+
+  MessageOptions* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const MessageOptions& from);
@@ -1780,7 +2137,21 @@ class LIBPROTOBUF_EXPORT MessageOptions : public ::google::protobuf::Message {
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(MessageOptions* other);
+  protected:
+  explicit MessageOptions(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -1808,6 +2179,13 @@ class LIBPROTOBUF_EXPORT MessageOptions : public ::google::protobuf::Message {
   inline bool deprecated() const;
   inline void set_deprecated(bool value);
 
+  // optional bool map_entry = 7;
+  inline bool has_map_entry() const;
+  inline void clear_map_entry();
+  static const int kMapEntryFieldNumber = 7;
+  inline bool map_entry() const;
+  inline void set_map_entry(bool value);
+
   // repeated .google.protobuf.UninterpretedOption uninterpreted_option = 999;
   inline int uninterpreted_option_size() const;
   inline void clear_uninterpreted_option();
@@ -1829,17 +2207,22 @@ class LIBPROTOBUF_EXPORT MessageOptions : public ::google::protobuf::Message {
   inline void clear_has_no_standard_descriptor_accessor();
   inline void set_has_deprecated();
   inline void clear_has_deprecated();
+  inline void set_has_map_entry();
+  inline void clear_has_map_entry();
 
   ::google::protobuf::internal::ExtensionSet _extensions_;
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::UninterpretedOption > uninterpreted_option_;
   bool message_set_wire_format_;
   bool no_standard_descriptor_accessor_;
   bool deprecated_;
+  bool map_entry_;
   friend void LIBPROTOBUF_EXPORT protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_ShutdownFile_google_2fprotobuf_2fdescriptor_2eproto();
@@ -1862,21 +2245,28 @@ class LIBPROTOBUF_EXPORT FieldOptions : public ::google::protobuf::Message {
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const FieldOptions& default_instance();
 
+  void UnsafeArenaSwap(FieldOptions* other);
   void Swap(FieldOptions* other);
 
   // implements Message ----------------------------------------------
 
-  FieldOptions* New() const;
+  inline FieldOptions* New() const { return New(NULL); }
+
+  FieldOptions* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const FieldOptions& from);
@@ -1895,7 +2285,21 @@ class LIBPROTOBUF_EXPORT FieldOptions : public ::google::protobuf::Message {
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(FieldOptions* other);
+  protected:
+  explicit FieldOptions(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -1955,18 +2359,6 @@ class LIBPROTOBUF_EXPORT FieldOptions : public ::google::protobuf::Message {
   inline bool deprecated() const;
   inline void set_deprecated(bool value);
 
-  // optional string experimental_map_key = 9;
-  inline bool has_experimental_map_key() const;
-  inline void clear_experimental_map_key();
-  static const int kExperimentalMapKeyFieldNumber = 9;
-  inline const ::std::string& experimental_map_key() const;
-  inline void set_experimental_map_key(const ::std::string& value);
-  inline void set_experimental_map_key(const char* value);
-  inline void set_experimental_map_key(const char* value, size_t size);
-  inline ::std::string* mutable_experimental_map_key();
-  inline ::std::string* release_experimental_map_key();
-  inline void set_allocated_experimental_map_key(::std::string* experimental_map_key);
-
   // optional bool weak = 10 [default = false];
   inline bool has_weak() const;
   inline void clear_weak();
@@ -1997,15 +2389,15 @@ class LIBPROTOBUF_EXPORT FieldOptions : public ::google::protobuf::Message {
   inline void clear_has_lazy();
   inline void set_has_deprecated();
   inline void clear_has_deprecated();
-  inline void set_has_experimental_map_key();
-  inline void clear_has_experimental_map_key();
   inline void set_has_weak();
   inline void clear_has_weak();
 
   ::google::protobuf::internal::ExtensionSet _extensions_;
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
   int ctype_;
@@ -2013,7 +2405,6 @@ class LIBPROTOBUF_EXPORT FieldOptions : public ::google::protobuf::Message {
   bool lazy_;
   bool deprecated_;
   bool weak_;
-  ::std::string* experimental_map_key_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::UninterpretedOption > uninterpreted_option_;
   friend void LIBPROTOBUF_EXPORT protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto();
@@ -2037,21 +2428,28 @@ class LIBPROTOBUF_EXPORT EnumOptions : public ::google::protobuf::Message {
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const EnumOptions& default_instance();
 
+  void UnsafeArenaSwap(EnumOptions* other);
   void Swap(EnumOptions* other);
 
   // implements Message ----------------------------------------------
 
-  EnumOptions* New() const;
+  inline EnumOptions* New() const { return New(NULL); }
+
+  EnumOptions* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const EnumOptions& from);
@@ -2070,7 +2468,21 @@ class LIBPROTOBUF_EXPORT EnumOptions : public ::google::protobuf::Message {
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(EnumOptions* other);
+  protected:
+  explicit EnumOptions(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -2113,8 +2525,10 @@ class LIBPROTOBUF_EXPORT EnumOptions : public ::google::protobuf::Message {
 
   ::google::protobuf::internal::ExtensionSet _extensions_;
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::UninterpretedOption > uninterpreted_option_;
@@ -2142,21 +2556,28 @@ class LIBPROTOBUF_EXPORT EnumValueOptions : public ::google::protobuf::Message {
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const EnumValueOptions& default_instance();
 
+  void UnsafeArenaSwap(EnumValueOptions* other);
   void Swap(EnumValueOptions* other);
 
   // implements Message ----------------------------------------------
 
-  EnumValueOptions* New() const;
+  inline EnumValueOptions* New() const { return New(NULL); }
+
+  EnumValueOptions* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const EnumValueOptions& from);
@@ -2175,7 +2596,21 @@ class LIBPROTOBUF_EXPORT EnumValueOptions : public ::google::protobuf::Message {
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(EnumValueOptions* other);
+  protected:
+  explicit EnumValueOptions(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -2209,8 +2644,10 @@ class LIBPROTOBUF_EXPORT EnumValueOptions : public ::google::protobuf::Message {
 
   ::google::protobuf::internal::ExtensionSet _extensions_;
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::UninterpretedOption > uninterpreted_option_;
@@ -2237,21 +2674,28 @@ class LIBPROTOBUF_EXPORT ServiceOptions : public ::google::protobuf::Message {
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const ServiceOptions& default_instance();
 
+  void UnsafeArenaSwap(ServiceOptions* other);
   void Swap(ServiceOptions* other);
 
   // implements Message ----------------------------------------------
 
-  ServiceOptions* New() const;
+  inline ServiceOptions* New() const { return New(NULL); }
+
+  ServiceOptions* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const ServiceOptions& from);
@@ -2270,7 +2714,21 @@ class LIBPROTOBUF_EXPORT ServiceOptions : public ::google::protobuf::Message {
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(ServiceOptions* other);
+  protected:
+  explicit ServiceOptions(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -2304,8 +2762,10 @@ class LIBPROTOBUF_EXPORT ServiceOptions : public ::google::protobuf::Message {
 
   ::google::protobuf::internal::ExtensionSet _extensions_;
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::UninterpretedOption > uninterpreted_option_;
@@ -2332,21 +2792,28 @@ class LIBPROTOBUF_EXPORT MethodOptions : public ::google::protobuf::Message {
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const MethodOptions& default_instance();
 
+  void UnsafeArenaSwap(MethodOptions* other);
   void Swap(MethodOptions* other);
 
   // implements Message ----------------------------------------------
 
-  MethodOptions* New() const;
+  inline MethodOptions* New() const { return New(NULL); }
+
+  MethodOptions* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const MethodOptions& from);
@@ -2365,7 +2832,21 @@ class LIBPROTOBUF_EXPORT MethodOptions : public ::google::protobuf::Message {
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(MethodOptions* other);
+  protected:
+  explicit MethodOptions(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -2399,8 +2880,10 @@ class LIBPROTOBUF_EXPORT MethodOptions : public ::google::protobuf::Message {
 
   ::google::protobuf::internal::ExtensionSet _extensions_;
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::UninterpretedOption > uninterpreted_option_;
@@ -2427,21 +2910,28 @@ class LIBPROTOBUF_EXPORT UninterpretedOption_NamePart : public ::google::protobu
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const UninterpretedOption_NamePart& default_instance();
 
+  void UnsafeArenaSwap(UninterpretedOption_NamePart* other);
   void Swap(UninterpretedOption_NamePart* other);
 
   // implements Message ----------------------------------------------
 
-  UninterpretedOption_NamePart* New() const;
+  inline UninterpretedOption_NamePart* New() const { return New(NULL); }
+
+  UninterpretedOption_NamePart* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const UninterpretedOption_NamePart& from);
@@ -2460,7 +2950,21 @@ class LIBPROTOBUF_EXPORT UninterpretedOption_NamePart : public ::google::protobu
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(UninterpretedOption_NamePart* other);
+  protected:
+  explicit UninterpretedOption_NamePart(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -2478,6 +2982,9 @@ class LIBPROTOBUF_EXPORT UninterpretedOption_NamePart : public ::google::protobu
   inline ::std::string* mutable_name_part();
   inline ::std::string* release_name_part();
   inline void set_allocated_name_part(::std::string* name_part);
+  inline ::std::string* unsafe_arena_release_name_part();
+  inline void unsafe_arena_set_allocated_name_part(
+      ::std::string* name_part);
 
   // required bool is_extension = 2;
   inline bool has_is_extension() const;
@@ -2493,11 +3000,16 @@ class LIBPROTOBUF_EXPORT UninterpretedOption_NamePart : public ::google::protobu
   inline void set_has_is_extension();
   inline void clear_has_is_extension();
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
+  // helper for ByteSize()
+  int RequiredFieldsByteSizeFallback() const;
 
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
-  ::std::string* name_part_;
+  ::google::protobuf::internal::ArenaStringPtr name_part_;
   bool is_extension_;
   friend void LIBPROTOBUF_EXPORT protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto();
@@ -2521,21 +3033,28 @@ class LIBPROTOBUF_EXPORT UninterpretedOption : public ::google::protobuf::Messag
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const UninterpretedOption& default_instance();
 
+  void UnsafeArenaSwap(UninterpretedOption* other);
   void Swap(UninterpretedOption* other);
 
   // implements Message ----------------------------------------------
 
-  UninterpretedOption* New() const;
+  inline UninterpretedOption* New() const { return New(NULL); }
+
+  UninterpretedOption* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const UninterpretedOption& from);
@@ -2554,7 +3073,21 @@ class LIBPROTOBUF_EXPORT UninterpretedOption : public ::google::protobuf::Messag
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(UninterpretedOption* other);
+  protected:
+  explicit UninterpretedOption(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -2586,6 +3119,9 @@ class LIBPROTOBUF_EXPORT UninterpretedOption : public ::google::protobuf::Messag
   inline ::std::string* mutable_identifier_value();
   inline ::std::string* release_identifier_value();
   inline void set_allocated_identifier_value(::std::string* identifier_value);
+  inline ::std::string* unsafe_arena_release_identifier_value();
+  inline void unsafe_arena_set_allocated_identifier_value(
+      ::std::string* identifier_value);
 
   // optional uint64 positive_int_value = 4;
   inline bool has_positive_int_value() const;
@@ -2619,6 +3155,9 @@ class LIBPROTOBUF_EXPORT UninterpretedOption : public ::google::protobuf::Messag
   inline ::std::string* mutable_string_value();
   inline ::std::string* release_string_value();
   inline void set_allocated_string_value(::std::string* string_value);
+  inline ::std::string* unsafe_arena_release_string_value();
+  inline void unsafe_arena_set_allocated_string_value(
+      ::std::string* string_value);
 
   // optional string aggregate_value = 8;
   inline bool has_aggregate_value() const;
@@ -2631,6 +3170,9 @@ class LIBPROTOBUF_EXPORT UninterpretedOption : public ::google::protobuf::Messag
   inline ::std::string* mutable_aggregate_value();
   inline ::std::string* release_aggregate_value();
   inline void set_allocated_aggregate_value(::std::string* aggregate_value);
+  inline ::std::string* unsafe_arena_release_aggregate_value();
+  inline void unsafe_arena_set_allocated_aggregate_value(
+      ::std::string* aggregate_value);
 
   // @@protoc_insertion_point(class_scope:google.protobuf.UninterpretedOption)
  private:
@@ -2647,17 +3189,19 @@ class LIBPROTOBUF_EXPORT UninterpretedOption : public ::google::protobuf::Messag
   inline void set_has_aggregate_value();
   inline void clear_has_aggregate_value();
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::UninterpretedOption_NamePart > name_;
-  ::std::string* identifier_value_;
+  ::google::protobuf::internal::ArenaStringPtr identifier_value_;
   ::google::protobuf::uint64 positive_int_value_;
   ::google::protobuf::int64 negative_int_value_;
   double double_value_;
-  ::std::string* string_value_;
-  ::std::string* aggregate_value_;
+  ::google::protobuf::internal::ArenaStringPtr string_value_;
+  ::google::protobuf::internal::ArenaStringPtr aggregate_value_;
   friend void LIBPROTOBUF_EXPORT protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_ShutdownFile_google_2fprotobuf_2fdescriptor_2eproto();
@@ -2680,21 +3224,28 @@ class LIBPROTOBUF_EXPORT SourceCodeInfo_Location : public ::google::protobuf::Me
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const SourceCodeInfo_Location& default_instance();
 
+  void UnsafeArenaSwap(SourceCodeInfo_Location* other);
   void Swap(SourceCodeInfo_Location* other);
 
   // implements Message ----------------------------------------------
 
-  SourceCodeInfo_Location* New() const;
+  inline SourceCodeInfo_Location* New() const { return New(NULL); }
+
+  SourceCodeInfo_Location* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const SourceCodeInfo_Location& from);
@@ -2713,7 +3264,21 @@ class LIBPROTOBUF_EXPORT SourceCodeInfo_Location : public ::google::protobuf::Me
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(SourceCodeInfo_Location* other);
+  protected:
+  explicit SourceCodeInfo_Location(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -2755,6 +3320,9 @@ class LIBPROTOBUF_EXPORT SourceCodeInfo_Location : public ::google::protobuf::Me
   inline ::std::string* mutable_leading_comments();
   inline ::std::string* release_leading_comments();
   inline void set_allocated_leading_comments(::std::string* leading_comments);
+  inline ::std::string* unsafe_arena_release_leading_comments();
+  inline void unsafe_arena_set_allocated_leading_comments(
+      ::std::string* leading_comments);
 
   // optional string trailing_comments = 4;
   inline bool has_trailing_comments() const;
@@ -2767,6 +3335,9 @@ class LIBPROTOBUF_EXPORT SourceCodeInfo_Location : public ::google::protobuf::Me
   inline ::std::string* mutable_trailing_comments();
   inline ::std::string* release_trailing_comments();
   inline void set_allocated_trailing_comments(::std::string* trailing_comments);
+  inline ::std::string* unsafe_arena_release_trailing_comments();
+  inline void unsafe_arena_set_allocated_trailing_comments(
+      ::std::string* trailing_comments);
 
   // @@protoc_insertion_point(class_scope:google.protobuf.SourceCodeInfo.Location)
  private:
@@ -2775,16 +3346,18 @@ class LIBPROTOBUF_EXPORT SourceCodeInfo_Location : public ::google::protobuf::Me
   inline void set_has_trailing_comments();
   inline void clear_has_trailing_comments();
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
   ::google::protobuf::RepeatedField< ::google::protobuf::int32 > path_;
   mutable int _path_cached_byte_size_;
   ::google::protobuf::RepeatedField< ::google::protobuf::int32 > span_;
   mutable int _span_cached_byte_size_;
-  ::std::string* leading_comments_;
-  ::std::string* trailing_comments_;
+  ::google::protobuf::internal::ArenaStringPtr leading_comments_;
+  ::google::protobuf::internal::ArenaStringPtr trailing_comments_;
   friend void LIBPROTOBUF_EXPORT protobuf_AddDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_AssignDesc_google_2fprotobuf_2fdescriptor_2eproto();
   friend void protobuf_ShutdownFile_google_2fprotobuf_2fdescriptor_2eproto();
@@ -2807,21 +3380,28 @@ class LIBPROTOBUF_EXPORT SourceCodeInfo : public ::google::protobuf::Message {
   }
 
   inline const ::google::protobuf::UnknownFieldSet& unknown_fields() const {
-    return _unknown_fields_;
+    return _internal_metadata_.unknown_fields();
   }
 
   inline ::google::protobuf::UnknownFieldSet* mutable_unknown_fields() {
-    return &_unknown_fields_;
+    return _internal_metadata_.mutable_unknown_fields();
   }
 
+  inline ::google::protobuf::Arena* GetArena() const { return GetArenaNoVirtual(); }
+  inline void* GetMaybeArenaPointer() const {
+    return MaybeArenaPtr();
+  }
   static const ::google::protobuf::Descriptor* descriptor();
   static const SourceCodeInfo& default_instance();
 
+  void UnsafeArenaSwap(SourceCodeInfo* other);
   void Swap(SourceCodeInfo* other);
 
   // implements Message ----------------------------------------------
 
-  SourceCodeInfo* New() const;
+  inline SourceCodeInfo* New() const { return New(NULL); }
+
+  SourceCodeInfo* New(::google::protobuf::Arena* arena) const;
   void CopyFrom(const ::google::protobuf::Message& from);
   void MergeFrom(const ::google::protobuf::Message& from);
   void CopyFrom(const SourceCodeInfo& from);
@@ -2840,7 +3420,21 @@ class LIBPROTOBUF_EXPORT SourceCodeInfo : public ::google::protobuf::Message {
   void SharedCtor();
   void SharedDtor();
   void SetCachedSize(int size) const;
+  void InternalSwap(SourceCodeInfo* other);
+  protected:
+  explicit SourceCodeInfo(::google::protobuf::Arena* arena);
+  private:
+  static void ArenaDtor(void* object);
+  inline void RegisterArenaDtor(::google::protobuf::Arena* arena);
+  private:
+  inline ::google::protobuf::Arena* GetArenaNoVirtual() const {
+    return _internal_metadata_.arena();
+  }
+  inline void* MaybeArenaPtr() const {
+    return _internal_metadata_.raw_arena_ptr();
+  }
   public:
+
   ::google::protobuf::Metadata GetMetadata() const;
 
   // nested types ----------------------------------------------------
@@ -2864,8 +3458,10 @@ class LIBPROTOBUF_EXPORT SourceCodeInfo : public ::google::protobuf::Message {
   // @@protoc_insertion_point(class_scope:google.protobuf.SourceCodeInfo)
  private:
 
-  ::google::protobuf::UnknownFieldSet _unknown_fields_;
-
+  ::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;
+  friend class ::google::protobuf::Arena;
+  typedef void InternalArenaConstructable_;
+  typedef void DestructorSkippable_;
   ::google::protobuf::uint32 _has_bits_[1];
   mutable int _cached_size_;
   ::google::protobuf::RepeatedPtrField< ::google::protobuf::SourceCodeInfo_Location > location_;
@@ -2928,68 +3524,67 @@ inline void FileDescriptorProto::clear_has_name() {
   _has_bits_[0] &= ~0x00000001u;
 }
 inline void FileDescriptorProto::clear_name() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_->clear();
-  }
+  name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_name();
 }
 inline const ::std::string& FileDescriptorProto::name() const {
   // @@protoc_insertion_point(field_get:google.protobuf.FileDescriptorProto.name)
-  return *name_;
+  return name_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void FileDescriptorProto::set_name(const ::std::string& value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.FileDescriptorProto.name)
 }
 inline void FileDescriptorProto::set_name(const char* value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.FileDescriptorProto.name)
 }
-inline void FileDescriptorProto::set_name(const char* value, size_t size) {
+inline void FileDescriptorProto::set_name(const char* value,
+    size_t size) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(reinterpret_cast<const char*>(value), size);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.FileDescriptorProto.name)
 }
 inline ::std::string* FileDescriptorProto::mutable_name() {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.FileDescriptorProto.name)
-  return name_;
+  return name_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* FileDescriptorProto::release_name() {
   clear_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = name_;
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return name_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* FileDescriptorProto::unsafe_arena_release_name() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_name();
+  return name_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void FileDescriptorProto::set_allocated_name(::std::string* name) {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
+  if (name != NULL) {
+    set_has_name();
+  } else {
+    clear_has_name();
   }
-  if (name) {
+  name_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), name,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.FileDescriptorProto.name)
+}
+inline void FileDescriptorProto::unsafe_arena_set_allocated_name(
+    ::std::string* name) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (name != NULL) {
     set_has_name();
-    name_ = name;
   } else {
     clear_has_name();
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_name();
+  name_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      name, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.FileDescriptorProto.name)
 }
 
@@ -3004,68 +3599,67 @@ inline void FileDescriptorProto::clear_has_package() {
   _has_bits_[0] &= ~0x00000002u;
 }
 inline void FileDescriptorProto::clear_package() {
-  if (package_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    package_->clear();
-  }
+  package_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_package();
 }
 inline const ::std::string& FileDescriptorProto::package() const {
   // @@protoc_insertion_point(field_get:google.protobuf.FileDescriptorProto.package)
-  return *package_;
+  return package_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void FileDescriptorProto::set_package(const ::std::string& value) {
   set_has_package();
-  if (package_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    package_ = new ::std::string;
-  }
-  package_->assign(value);
+  package_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.FileDescriptorProto.package)
 }
 inline void FileDescriptorProto::set_package(const char* value) {
   set_has_package();
-  if (package_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    package_ = new ::std::string;
-  }
-  package_->assign(value);
+  package_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.FileDescriptorProto.package)
 }
-inline void FileDescriptorProto::set_package(const char* value, size_t size) {
+inline void FileDescriptorProto::set_package(const char* value,
+    size_t size) {
   set_has_package();
-  if (package_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    package_ = new ::std::string;
-  }
-  package_->assign(reinterpret_cast<const char*>(value), size);
+  package_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.FileDescriptorProto.package)
 }
 inline ::std::string* FileDescriptorProto::mutable_package() {
   set_has_package();
-  if (package_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    package_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.FileDescriptorProto.package)
-  return package_;
+  return package_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* FileDescriptorProto::release_package() {
   clear_has_package();
-  if (package_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = package_;
-    package_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return package_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* FileDescriptorProto::unsafe_arena_release_package() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_package();
+  return package_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void FileDescriptorProto::set_allocated_package(::std::string* package) {
-  if (package_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete package_;
+  if (package != NULL) {
+    set_has_package();
+  } else {
+    clear_has_package();
   }
-  if (package) {
+  package_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), package,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.FileDescriptorProto.package)
+}
+inline void FileDescriptorProto::unsafe_arena_set_allocated_package(
+    ::std::string* package) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (package != NULL) {
     set_has_package();
-    package_ = package;
   } else {
     clear_has_package();
-    package_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_package();
+  package_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      package, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.FileDescriptorProto.package)
 }
 
@@ -3323,18 +3917,53 @@ inline const ::google::protobuf::FileOptions& FileDescriptorProto::options() con
 }
 inline ::google::protobuf::FileOptions* FileDescriptorProto::mutable_options() {
   set_has_options();
-  if (options_ == NULL) options_ = new ::google::protobuf::FileOptions;
+  if (options_ == NULL) {
+    options_ = ::google::protobuf::Arena::CreateMessage< ::google::protobuf::FileOptions >(
+        GetArenaNoVirtual());
+  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.FileDescriptorProto.options)
   return options_;
 }
 inline ::google::protobuf::FileOptions* FileDescriptorProto::release_options() {
   clear_has_options();
+  if (GetArenaNoVirtual() != NULL) {
+    if (options_ == NULL) {
+      return NULL;
+    } else {
+      ::google::protobuf::FileOptions* temp = new ::google::protobuf::FileOptions;
+      temp->MergeFrom(*options_);
+      options_ = NULL;
+      return temp;
+    }
+  } else {
+    ::google::protobuf::FileOptions* temp = options_;
+    options_ = NULL;
+    return temp;
+  }
+}
+inline ::google::protobuf::FileOptions* FileDescriptorProto::unsafe_arena_release_options() {
+  clear_has_options();
   ::google::protobuf::FileOptions* temp = options_;
   options_ = NULL;
   return temp;
 }
 inline void FileDescriptorProto::set_allocated_options(::google::protobuf::FileOptions* options) {
-  delete options_;
+  if (GetArenaNoVirtual() == NULL) {
+    delete options_;
+  }
+  if (options != NULL) {
+    if (GetArenaNoVirtual() != NULL && 
+        ::google::protobuf::Arena::GetArena(options) == NULL) {
+      GetArenaNoVirtual()->Own(options);
+    } else if (GetArenaNoVirtual() !=
+               ::google::protobuf::Arena::GetArena(options)) {
+      ::google::protobuf::FileOptions* new_options = 
+            ::google::protobuf::Arena::CreateMessage< ::google::protobuf::FileOptions >(
+            GetArenaNoVirtual());
+      new_options->CopyFrom(*options);
+      options = new_options;
+    }
+  }
   options_ = options;
   if (options) {
     set_has_options();
@@ -3343,6 +3972,19 @@ inline void FileDescriptorProto::set_allocated_options(::google::protobuf::FileO
   }
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.FileDescriptorProto.options)
 }
+inline void FileDescriptorProto::unsafe_arena_set_allocated_options(
+    ::google::protobuf::FileOptions* options) {
+  if (GetArenaNoVirtual() == NULL) {
+    delete options_;
+  }
+  options_ = options;
+  if (options) {
+    set_has_options();
+  } else {
+    clear_has_options();
+  }
+  // @@protoc_insertion_point(field_unsafe_arena_set_allocated:google.protobuf.FileDescriptorProto.options)
+}
 
 // optional .google.protobuf.SourceCodeInfo source_code_info = 9;
 inline bool FileDescriptorProto::has_source_code_info() const {
@@ -3364,18 +4006,53 @@ inline const ::google::protobuf::SourceCodeInfo& FileDescriptorProto::source_cod
 }
 inline ::google::protobuf::SourceCodeInfo* FileDescriptorProto::mutable_source_code_info() {
   set_has_source_code_info();
-  if (source_code_info_ == NULL) source_code_info_ = new ::google::protobuf::SourceCodeInfo;
+  if (source_code_info_ == NULL) {
+    source_code_info_ = ::google::protobuf::Arena::CreateMessage< ::google::protobuf::SourceCodeInfo >(
+        GetArenaNoVirtual());
+  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.FileDescriptorProto.source_code_info)
   return source_code_info_;
 }
 inline ::google::protobuf::SourceCodeInfo* FileDescriptorProto::release_source_code_info() {
   clear_has_source_code_info();
+  if (GetArenaNoVirtual() != NULL) {
+    if (source_code_info_ == NULL) {
+      return NULL;
+    } else {
+      ::google::protobuf::SourceCodeInfo* temp = new ::google::protobuf::SourceCodeInfo;
+      temp->MergeFrom(*source_code_info_);
+      source_code_info_ = NULL;
+      return temp;
+    }
+  } else {
+    ::google::protobuf::SourceCodeInfo* temp = source_code_info_;
+    source_code_info_ = NULL;
+    return temp;
+  }
+}
+inline ::google::protobuf::SourceCodeInfo* FileDescriptorProto::unsafe_arena_release_source_code_info() {
+  clear_has_source_code_info();
   ::google::protobuf::SourceCodeInfo* temp = source_code_info_;
   source_code_info_ = NULL;
   return temp;
 }
 inline void FileDescriptorProto::set_allocated_source_code_info(::google::protobuf::SourceCodeInfo* source_code_info) {
-  delete source_code_info_;
+  if (GetArenaNoVirtual() == NULL) {
+    delete source_code_info_;
+  }
+  if (source_code_info != NULL) {
+    if (GetArenaNoVirtual() != NULL && 
+        ::google::protobuf::Arena::GetArena(source_code_info) == NULL) {
+      GetArenaNoVirtual()->Own(source_code_info);
+    } else if (GetArenaNoVirtual() !=
+               ::google::protobuf::Arena::GetArena(source_code_info)) {
+      ::google::protobuf::SourceCodeInfo* new_source_code_info = 
+            ::google::protobuf::Arena::CreateMessage< ::google::protobuf::SourceCodeInfo >(
+            GetArenaNoVirtual());
+      new_source_code_info->CopyFrom(*source_code_info);
+      source_code_info = new_source_code_info;
+    }
+  }
   source_code_info_ = source_code_info;
   if (source_code_info) {
     set_has_source_code_info();
@@ -3384,6 +4061,94 @@ inline void FileDescriptorProto::set_allocated_source_code_info(::google::protob
   }
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.FileDescriptorProto.source_code_info)
 }
+inline void FileDescriptorProto::unsafe_arena_set_allocated_source_code_info(
+    ::google::protobuf::SourceCodeInfo* source_code_info) {
+  if (GetArenaNoVirtual() == NULL) {
+    delete source_code_info_;
+  }
+  source_code_info_ = source_code_info;
+  if (source_code_info) {
+    set_has_source_code_info();
+  } else {
+    clear_has_source_code_info();
+  }
+  // @@protoc_insertion_point(field_unsafe_arena_set_allocated:google.protobuf.FileDescriptorProto.source_code_info)
+}
+
+// optional string syntax = 12;
+inline bool FileDescriptorProto::has_syntax() const {
+  return (_has_bits_[0] & 0x00000800u) != 0;
+}
+inline void FileDescriptorProto::set_has_syntax() {
+  _has_bits_[0] |= 0x00000800u;
+}
+inline void FileDescriptorProto::clear_has_syntax() {
+  _has_bits_[0] &= ~0x00000800u;
+}
+inline void FileDescriptorProto::clear_syntax() {
+  syntax_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+  clear_has_syntax();
+}
+inline const ::std::string& FileDescriptorProto::syntax() const {
+  // @@protoc_insertion_point(field_get:google.protobuf.FileDescriptorProto.syntax)
+  return syntax_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
+}
+inline void FileDescriptorProto::set_syntax(const ::std::string& value) {
+  set_has_syntax();
+  syntax_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set:google.protobuf.FileDescriptorProto.syntax)
+}
+inline void FileDescriptorProto::set_syntax(const char* value) {
+  set_has_syntax();
+  syntax_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_char:google.protobuf.FileDescriptorProto.syntax)
+}
+inline void FileDescriptorProto::set_syntax(const char* value,
+    size_t size) {
+  set_has_syntax();
+  syntax_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_pointer:google.protobuf.FileDescriptorProto.syntax)
+}
+inline ::std::string* FileDescriptorProto::mutable_syntax() {
+  set_has_syntax();
+  // @@protoc_insertion_point(field_mutable:google.protobuf.FileDescriptorProto.syntax)
+  return syntax_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* FileDescriptorProto::release_syntax() {
+  clear_has_syntax();
+  return syntax_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* FileDescriptorProto::unsafe_arena_release_syntax() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_syntax();
+  return syntax_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
+}
+inline void FileDescriptorProto::set_allocated_syntax(::std::string* syntax) {
+  if (syntax != NULL) {
+    set_has_syntax();
+  } else {
+    clear_has_syntax();
+  }
+  syntax_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), syntax,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.FileDescriptorProto.syntax)
+}
+inline void FileDescriptorProto::unsafe_arena_set_allocated_syntax(
+    ::std::string* syntax) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (syntax != NULL) {
+    set_has_syntax();
+  } else {
+    clear_has_syntax();
+  }
+  set_has_syntax();
+  syntax_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      syntax, GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.FileDescriptorProto.syntax)
+}
 
 // -------------------------------------------------------------------
 
@@ -3452,68 +4217,67 @@ inline void DescriptorProto::clear_has_name() {
   _has_bits_[0] &= ~0x00000001u;
 }
 inline void DescriptorProto::clear_name() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_->clear();
-  }
+  name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_name();
 }
 inline const ::std::string& DescriptorProto::name() const {
   // @@protoc_insertion_point(field_get:google.protobuf.DescriptorProto.name)
-  return *name_;
+  return name_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void DescriptorProto::set_name(const ::std::string& value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.DescriptorProto.name)
 }
 inline void DescriptorProto::set_name(const char* value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.DescriptorProto.name)
 }
-inline void DescriptorProto::set_name(const char* value, size_t size) {
+inline void DescriptorProto::set_name(const char* value,
+    size_t size) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(reinterpret_cast<const char*>(value), size);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.DescriptorProto.name)
 }
 inline ::std::string* DescriptorProto::mutable_name() {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.DescriptorProto.name)
-  return name_;
+  return name_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* DescriptorProto::release_name() {
   clear_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = name_;
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return name_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* DescriptorProto::unsafe_arena_release_name() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_name();
+  return name_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void DescriptorProto::set_allocated_name(::std::string* name) {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
+  if (name != NULL) {
+    set_has_name();
+  } else {
+    clear_has_name();
   }
-  if (name) {
+  name_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), name,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.DescriptorProto.name)
+}
+inline void DescriptorProto::unsafe_arena_set_allocated_name(
+    ::std::string* name) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (name != NULL) {
     set_has_name();
-    name_ = name;
   } else {
     clear_has_name();
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_name();
+  name_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      name, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.DescriptorProto.name)
 }
 
@@ -3717,18 +4481,53 @@ inline const ::google::protobuf::MessageOptions& DescriptorProto::options() cons
 }
 inline ::google::protobuf::MessageOptions* DescriptorProto::mutable_options() {
   set_has_options();
-  if (options_ == NULL) options_ = new ::google::protobuf::MessageOptions;
+  if (options_ == NULL) {
+    options_ = ::google::protobuf::Arena::CreateMessage< ::google::protobuf::MessageOptions >(
+        GetArenaNoVirtual());
+  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.DescriptorProto.options)
   return options_;
 }
 inline ::google::protobuf::MessageOptions* DescriptorProto::release_options() {
   clear_has_options();
+  if (GetArenaNoVirtual() != NULL) {
+    if (options_ == NULL) {
+      return NULL;
+    } else {
+      ::google::protobuf::MessageOptions* temp = new ::google::protobuf::MessageOptions;
+      temp->MergeFrom(*options_);
+      options_ = NULL;
+      return temp;
+    }
+  } else {
+    ::google::protobuf::MessageOptions* temp = options_;
+    options_ = NULL;
+    return temp;
+  }
+}
+inline ::google::protobuf::MessageOptions* DescriptorProto::unsafe_arena_release_options() {
+  clear_has_options();
   ::google::protobuf::MessageOptions* temp = options_;
   options_ = NULL;
   return temp;
 }
 inline void DescriptorProto::set_allocated_options(::google::protobuf::MessageOptions* options) {
-  delete options_;
+  if (GetArenaNoVirtual() == NULL) {
+    delete options_;
+  }
+  if (options != NULL) {
+    if (GetArenaNoVirtual() != NULL && 
+        ::google::protobuf::Arena::GetArena(options) == NULL) {
+      GetArenaNoVirtual()->Own(options);
+    } else if (GetArenaNoVirtual() !=
+               ::google::protobuf::Arena::GetArena(options)) {
+      ::google::protobuf::MessageOptions* new_options = 
+            ::google::protobuf::Arena::CreateMessage< ::google::protobuf::MessageOptions >(
+            GetArenaNoVirtual());
+      new_options->CopyFrom(*options);
+      options = new_options;
+    }
+  }
   options_ = options;
   if (options) {
     set_has_options();
@@ -3737,6 +4536,19 @@ inline void DescriptorProto::set_allocated_options(::google::protobuf::MessageOp
   }
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.DescriptorProto.options)
 }
+inline void DescriptorProto::unsafe_arena_set_allocated_options(
+    ::google::protobuf::MessageOptions* options) {
+  if (GetArenaNoVirtual() == NULL) {
+    delete options_;
+  }
+  options_ = options;
+  if (options) {
+    set_has_options();
+  } else {
+    clear_has_options();
+  }
+  // @@protoc_insertion_point(field_unsafe_arena_set_allocated:google.protobuf.DescriptorProto.options)
+}
 
 // -------------------------------------------------------------------
 
@@ -3753,68 +4565,67 @@ inline void FieldDescriptorProto::clear_has_name() {
   _has_bits_[0] &= ~0x00000001u;
 }
 inline void FieldDescriptorProto::clear_name() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_->clear();
-  }
+  name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_name();
 }
 inline const ::std::string& FieldDescriptorProto::name() const {
   // @@protoc_insertion_point(field_get:google.protobuf.FieldDescriptorProto.name)
-  return *name_;
+  return name_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void FieldDescriptorProto::set_name(const ::std::string& value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.FieldDescriptorProto.name)
 }
 inline void FieldDescriptorProto::set_name(const char* value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.FieldDescriptorProto.name)
 }
-inline void FieldDescriptorProto::set_name(const char* value, size_t size) {
+inline void FieldDescriptorProto::set_name(const char* value,
+    size_t size) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(reinterpret_cast<const char*>(value), size);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.FieldDescriptorProto.name)
 }
 inline ::std::string* FieldDescriptorProto::mutable_name() {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.FieldDescriptorProto.name)
-  return name_;
+  return name_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* FieldDescriptorProto::release_name() {
   clear_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = name_;
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return name_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* FieldDescriptorProto::unsafe_arena_release_name() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_name();
+  return name_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void FieldDescriptorProto::set_allocated_name(::std::string* name) {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
+  if (name != NULL) {
+    set_has_name();
+  } else {
+    clear_has_name();
   }
-  if (name) {
+  name_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), name,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.FieldDescriptorProto.name)
+}
+inline void FieldDescriptorProto::unsafe_arena_set_allocated_name(
+    ::std::string* name) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (name != NULL) {
     set_has_name();
-    name_ = name;
   } else {
     clear_has_name();
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_name();
+  name_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      name, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.FieldDescriptorProto.name)
 }
 
@@ -3903,68 +4714,67 @@ inline void FieldDescriptorProto::clear_has_type_name() {
   _has_bits_[0] &= ~0x00000010u;
 }
 inline void FieldDescriptorProto::clear_type_name() {
-  if (type_name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    type_name_->clear();
-  }
+  type_name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_type_name();
 }
 inline const ::std::string& FieldDescriptorProto::type_name() const {
   // @@protoc_insertion_point(field_get:google.protobuf.FieldDescriptorProto.type_name)
-  return *type_name_;
+  return type_name_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void FieldDescriptorProto::set_type_name(const ::std::string& value) {
   set_has_type_name();
-  if (type_name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    type_name_ = new ::std::string;
-  }
-  type_name_->assign(value);
+  type_name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.FieldDescriptorProto.type_name)
 }
 inline void FieldDescriptorProto::set_type_name(const char* value) {
   set_has_type_name();
-  if (type_name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    type_name_ = new ::std::string;
-  }
-  type_name_->assign(value);
+  type_name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.FieldDescriptorProto.type_name)
 }
-inline void FieldDescriptorProto::set_type_name(const char* value, size_t size) {
+inline void FieldDescriptorProto::set_type_name(const char* value,
+    size_t size) {
   set_has_type_name();
-  if (type_name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    type_name_ = new ::std::string;
-  }
-  type_name_->assign(reinterpret_cast<const char*>(value), size);
+  type_name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.FieldDescriptorProto.type_name)
 }
 inline ::std::string* FieldDescriptorProto::mutable_type_name() {
   set_has_type_name();
-  if (type_name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    type_name_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.FieldDescriptorProto.type_name)
-  return type_name_;
+  return type_name_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* FieldDescriptorProto::release_type_name() {
   clear_has_type_name();
-  if (type_name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = type_name_;
-    type_name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return type_name_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* FieldDescriptorProto::unsafe_arena_release_type_name() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_type_name();
+  return type_name_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void FieldDescriptorProto::set_allocated_type_name(::std::string* type_name) {
-  if (type_name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete type_name_;
+  if (type_name != NULL) {
+    set_has_type_name();
+  } else {
+    clear_has_type_name();
   }
-  if (type_name) {
+  type_name_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), type_name,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.FieldDescriptorProto.type_name)
+}
+inline void FieldDescriptorProto::unsafe_arena_set_allocated_type_name(
+    ::std::string* type_name) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (type_name != NULL) {
     set_has_type_name();
-    type_name_ = type_name;
   } else {
     clear_has_type_name();
-    type_name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_type_name();
+  type_name_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      type_name, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.FieldDescriptorProto.type_name)
 }
 
@@ -3979,68 +4789,67 @@ inline void FieldDescriptorProto::clear_has_extendee() {
   _has_bits_[0] &= ~0x00000020u;
 }
 inline void FieldDescriptorProto::clear_extendee() {
-  if (extendee_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    extendee_->clear();
-  }
+  extendee_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_extendee();
 }
 inline const ::std::string& FieldDescriptorProto::extendee() const {
   // @@protoc_insertion_point(field_get:google.protobuf.FieldDescriptorProto.extendee)
-  return *extendee_;
+  return extendee_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void FieldDescriptorProto::set_extendee(const ::std::string& value) {
   set_has_extendee();
-  if (extendee_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    extendee_ = new ::std::string;
-  }
-  extendee_->assign(value);
+  extendee_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.FieldDescriptorProto.extendee)
 }
 inline void FieldDescriptorProto::set_extendee(const char* value) {
   set_has_extendee();
-  if (extendee_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    extendee_ = new ::std::string;
-  }
-  extendee_->assign(value);
+  extendee_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.FieldDescriptorProto.extendee)
 }
-inline void FieldDescriptorProto::set_extendee(const char* value, size_t size) {
+inline void FieldDescriptorProto::set_extendee(const char* value,
+    size_t size) {
   set_has_extendee();
-  if (extendee_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    extendee_ = new ::std::string;
-  }
-  extendee_->assign(reinterpret_cast<const char*>(value), size);
+  extendee_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.FieldDescriptorProto.extendee)
 }
 inline ::std::string* FieldDescriptorProto::mutable_extendee() {
   set_has_extendee();
-  if (extendee_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    extendee_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.FieldDescriptorProto.extendee)
-  return extendee_;
+  return extendee_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* FieldDescriptorProto::release_extendee() {
   clear_has_extendee();
-  if (extendee_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = extendee_;
-    extendee_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return extendee_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* FieldDescriptorProto::unsafe_arena_release_extendee() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_extendee();
+  return extendee_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void FieldDescriptorProto::set_allocated_extendee(::std::string* extendee) {
-  if (extendee_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete extendee_;
+  if (extendee != NULL) {
+    set_has_extendee();
+  } else {
+    clear_has_extendee();
   }
-  if (extendee) {
+  extendee_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), extendee,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.FieldDescriptorProto.extendee)
+}
+inline void FieldDescriptorProto::unsafe_arena_set_allocated_extendee(
+    ::std::string* extendee) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (extendee != NULL) {
     set_has_extendee();
-    extendee_ = extendee;
   } else {
     clear_has_extendee();
-    extendee_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_extendee();
+  extendee_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      extendee, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.FieldDescriptorProto.extendee)
 }
 
@@ -4055,68 +4864,67 @@ inline void FieldDescriptorProto::clear_has_default_value() {
   _has_bits_[0] &= ~0x00000040u;
 }
 inline void FieldDescriptorProto::clear_default_value() {
-  if (default_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    default_value_->clear();
-  }
+  default_value_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_default_value();
 }
 inline const ::std::string& FieldDescriptorProto::default_value() const {
   // @@protoc_insertion_point(field_get:google.protobuf.FieldDescriptorProto.default_value)
-  return *default_value_;
+  return default_value_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void FieldDescriptorProto::set_default_value(const ::std::string& value) {
   set_has_default_value();
-  if (default_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    default_value_ = new ::std::string;
-  }
-  default_value_->assign(value);
+  default_value_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.FieldDescriptorProto.default_value)
 }
 inline void FieldDescriptorProto::set_default_value(const char* value) {
   set_has_default_value();
-  if (default_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    default_value_ = new ::std::string;
-  }
-  default_value_->assign(value);
+  default_value_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.FieldDescriptorProto.default_value)
 }
-inline void FieldDescriptorProto::set_default_value(const char* value, size_t size) {
+inline void FieldDescriptorProto::set_default_value(const char* value,
+    size_t size) {
   set_has_default_value();
-  if (default_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    default_value_ = new ::std::string;
-  }
-  default_value_->assign(reinterpret_cast<const char*>(value), size);
+  default_value_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.FieldDescriptorProto.default_value)
 }
 inline ::std::string* FieldDescriptorProto::mutable_default_value() {
   set_has_default_value();
-  if (default_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    default_value_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.FieldDescriptorProto.default_value)
-  return default_value_;
+  return default_value_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* FieldDescriptorProto::release_default_value() {
   clear_has_default_value();
-  if (default_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = default_value_;
-    default_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return default_value_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* FieldDescriptorProto::unsafe_arena_release_default_value() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_default_value();
+  return default_value_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void FieldDescriptorProto::set_allocated_default_value(::std::string* default_value) {
-  if (default_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete default_value_;
+  if (default_value != NULL) {
+    set_has_default_value();
+  } else {
+    clear_has_default_value();
   }
-  if (default_value) {
+  default_value_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), default_value,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.FieldDescriptorProto.default_value)
+}
+inline void FieldDescriptorProto::unsafe_arena_set_allocated_default_value(
+    ::std::string* default_value) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (default_value != NULL) {
     set_has_default_value();
-    default_value_ = default_value;
   } else {
     clear_has_default_value();
-    default_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_default_value();
+  default_value_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      default_value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.FieldDescriptorProto.default_value)
 }
 
@@ -4164,18 +4972,53 @@ inline const ::google::protobuf::FieldOptions& FieldDescriptorProto::options() c
 }
 inline ::google::protobuf::FieldOptions* FieldDescriptorProto::mutable_options() {
   set_has_options();
-  if (options_ == NULL) options_ = new ::google::protobuf::FieldOptions;
+  if (options_ == NULL) {
+    options_ = ::google::protobuf::Arena::CreateMessage< ::google::protobuf::FieldOptions >(
+        GetArenaNoVirtual());
+  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.FieldDescriptorProto.options)
   return options_;
 }
 inline ::google::protobuf::FieldOptions* FieldDescriptorProto::release_options() {
   clear_has_options();
+  if (GetArenaNoVirtual() != NULL) {
+    if (options_ == NULL) {
+      return NULL;
+    } else {
+      ::google::protobuf::FieldOptions* temp = new ::google::protobuf::FieldOptions;
+      temp->MergeFrom(*options_);
+      options_ = NULL;
+      return temp;
+    }
+  } else {
+    ::google::protobuf::FieldOptions* temp = options_;
+    options_ = NULL;
+    return temp;
+  }
+}
+inline ::google::protobuf::FieldOptions* FieldDescriptorProto::unsafe_arena_release_options() {
+  clear_has_options();
   ::google::protobuf::FieldOptions* temp = options_;
   options_ = NULL;
   return temp;
 }
 inline void FieldDescriptorProto::set_allocated_options(::google::protobuf::FieldOptions* options) {
-  delete options_;
+  if (GetArenaNoVirtual() == NULL) {
+    delete options_;
+  }
+  if (options != NULL) {
+    if (GetArenaNoVirtual() != NULL && 
+        ::google::protobuf::Arena::GetArena(options) == NULL) {
+      GetArenaNoVirtual()->Own(options);
+    } else if (GetArenaNoVirtual() !=
+               ::google::protobuf::Arena::GetArena(options)) {
+      ::google::protobuf::FieldOptions* new_options = 
+            ::google::protobuf::Arena::CreateMessage< ::google::protobuf::FieldOptions >(
+            GetArenaNoVirtual());
+      new_options->CopyFrom(*options);
+      options = new_options;
+    }
+  }
   options_ = options;
   if (options) {
     set_has_options();
@@ -4184,6 +5027,19 @@ inline void FieldDescriptorProto::set_allocated_options(::google::protobuf::Fiel
   }
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.FieldDescriptorProto.options)
 }
+inline void FieldDescriptorProto::unsafe_arena_set_allocated_options(
+    ::google::protobuf::FieldOptions* options) {
+  if (GetArenaNoVirtual() == NULL) {
+    delete options_;
+  }
+  options_ = options;
+  if (options) {
+    set_has_options();
+  } else {
+    clear_has_options();
+  }
+  // @@protoc_insertion_point(field_unsafe_arena_set_allocated:google.protobuf.FieldDescriptorProto.options)
+}
 
 // -------------------------------------------------------------------
 
@@ -4200,68 +5056,67 @@ inline void OneofDescriptorProto::clear_has_name() {
   _has_bits_[0] &= ~0x00000001u;
 }
 inline void OneofDescriptorProto::clear_name() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_->clear();
-  }
+  name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_name();
 }
 inline const ::std::string& OneofDescriptorProto::name() const {
   // @@protoc_insertion_point(field_get:google.protobuf.OneofDescriptorProto.name)
-  return *name_;
+  return name_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void OneofDescriptorProto::set_name(const ::std::string& value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.OneofDescriptorProto.name)
 }
 inline void OneofDescriptorProto::set_name(const char* value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.OneofDescriptorProto.name)
 }
-inline void OneofDescriptorProto::set_name(const char* value, size_t size) {
+inline void OneofDescriptorProto::set_name(const char* value,
+    size_t size) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(reinterpret_cast<const char*>(value), size);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.OneofDescriptorProto.name)
 }
 inline ::std::string* OneofDescriptorProto::mutable_name() {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.OneofDescriptorProto.name)
-  return name_;
+  return name_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* OneofDescriptorProto::release_name() {
   clear_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = name_;
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return name_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* OneofDescriptorProto::unsafe_arena_release_name() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_name();
+  return name_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void OneofDescriptorProto::set_allocated_name(::std::string* name) {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
+  if (name != NULL) {
+    set_has_name();
+  } else {
+    clear_has_name();
   }
-  if (name) {
+  name_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), name,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.OneofDescriptorProto.name)
+}
+inline void OneofDescriptorProto::unsafe_arena_set_allocated_name(
+    ::std::string* name) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (name != NULL) {
     set_has_name();
-    name_ = name;
   } else {
     clear_has_name();
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_name();
+  name_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      name, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.OneofDescriptorProto.name)
 }
 
@@ -4280,68 +5135,67 @@ inline void EnumDescriptorProto::clear_has_name() {
   _has_bits_[0] &= ~0x00000001u;
 }
 inline void EnumDescriptorProto::clear_name() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_->clear();
-  }
+  name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_name();
 }
 inline const ::std::string& EnumDescriptorProto::name() const {
   // @@protoc_insertion_point(field_get:google.protobuf.EnumDescriptorProto.name)
-  return *name_;
+  return name_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void EnumDescriptorProto::set_name(const ::std::string& value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.EnumDescriptorProto.name)
 }
 inline void EnumDescriptorProto::set_name(const char* value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.EnumDescriptorProto.name)
 }
-inline void EnumDescriptorProto::set_name(const char* value, size_t size) {
+inline void EnumDescriptorProto::set_name(const char* value,
+    size_t size) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(reinterpret_cast<const char*>(value), size);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.EnumDescriptorProto.name)
 }
 inline ::std::string* EnumDescriptorProto::mutable_name() {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.EnumDescriptorProto.name)
-  return name_;
+  return name_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* EnumDescriptorProto::release_name() {
   clear_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = name_;
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return name_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* EnumDescriptorProto::unsafe_arena_release_name() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_name();
+  return name_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void EnumDescriptorProto::set_allocated_name(::std::string* name) {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
+  if (name != NULL) {
+    set_has_name();
+  } else {
+    clear_has_name();
   }
-  if (name) {
+  name_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), name,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.EnumDescriptorProto.name)
+}
+inline void EnumDescriptorProto::unsafe_arena_set_allocated_name(
+    ::std::string* name) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (name != NULL) {
     set_has_name();
-    name_ = name;
   } else {
     clear_has_name();
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_name();
+  name_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      name, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.EnumDescriptorProto.name)
 }
 
@@ -4395,18 +5249,53 @@ inline const ::google::protobuf::EnumOptions& EnumDescriptorProto::options() con
 }
 inline ::google::protobuf::EnumOptions* EnumDescriptorProto::mutable_options() {
   set_has_options();
-  if (options_ == NULL) options_ = new ::google::protobuf::EnumOptions;
+  if (options_ == NULL) {
+    options_ = ::google::protobuf::Arena::CreateMessage< ::google::protobuf::EnumOptions >(
+        GetArenaNoVirtual());
+  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.EnumDescriptorProto.options)
   return options_;
 }
 inline ::google::protobuf::EnumOptions* EnumDescriptorProto::release_options() {
   clear_has_options();
+  if (GetArenaNoVirtual() != NULL) {
+    if (options_ == NULL) {
+      return NULL;
+    } else {
+      ::google::protobuf::EnumOptions* temp = new ::google::protobuf::EnumOptions;
+      temp->MergeFrom(*options_);
+      options_ = NULL;
+      return temp;
+    }
+  } else {
+    ::google::protobuf::EnumOptions* temp = options_;
+    options_ = NULL;
+    return temp;
+  }
+}
+inline ::google::protobuf::EnumOptions* EnumDescriptorProto::unsafe_arena_release_options() {
+  clear_has_options();
   ::google::protobuf::EnumOptions* temp = options_;
   options_ = NULL;
   return temp;
 }
 inline void EnumDescriptorProto::set_allocated_options(::google::protobuf::EnumOptions* options) {
-  delete options_;
+  if (GetArenaNoVirtual() == NULL) {
+    delete options_;
+  }
+  if (options != NULL) {
+    if (GetArenaNoVirtual() != NULL && 
+        ::google::protobuf::Arena::GetArena(options) == NULL) {
+      GetArenaNoVirtual()->Own(options);
+    } else if (GetArenaNoVirtual() !=
+               ::google::protobuf::Arena::GetArena(options)) {
+      ::google::protobuf::EnumOptions* new_options = 
+            ::google::protobuf::Arena::CreateMessage< ::google::protobuf::EnumOptions >(
+            GetArenaNoVirtual());
+      new_options->CopyFrom(*options);
+      options = new_options;
+    }
+  }
   options_ = options;
   if (options) {
     set_has_options();
@@ -4415,6 +5304,19 @@ inline void EnumDescriptorProto::set_allocated_options(::google::protobuf::EnumO
   }
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.EnumDescriptorProto.options)
 }
+inline void EnumDescriptorProto::unsafe_arena_set_allocated_options(
+    ::google::protobuf::EnumOptions* options) {
+  if (GetArenaNoVirtual() == NULL) {
+    delete options_;
+  }
+  options_ = options;
+  if (options) {
+    set_has_options();
+  } else {
+    clear_has_options();
+  }
+  // @@protoc_insertion_point(field_unsafe_arena_set_allocated:google.protobuf.EnumDescriptorProto.options)
+}
 
 // -------------------------------------------------------------------
 
@@ -4431,68 +5333,67 @@ inline void EnumValueDescriptorProto::clear_has_name() {
   _has_bits_[0] &= ~0x00000001u;
 }
 inline void EnumValueDescriptorProto::clear_name() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_->clear();
-  }
+  name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_name();
 }
 inline const ::std::string& EnumValueDescriptorProto::name() const {
   // @@protoc_insertion_point(field_get:google.protobuf.EnumValueDescriptorProto.name)
-  return *name_;
+  return name_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void EnumValueDescriptorProto::set_name(const ::std::string& value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.EnumValueDescriptorProto.name)
 }
 inline void EnumValueDescriptorProto::set_name(const char* value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.EnumValueDescriptorProto.name)
 }
-inline void EnumValueDescriptorProto::set_name(const char* value, size_t size) {
+inline void EnumValueDescriptorProto::set_name(const char* value,
+    size_t size) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(reinterpret_cast<const char*>(value), size);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.EnumValueDescriptorProto.name)
 }
 inline ::std::string* EnumValueDescriptorProto::mutable_name() {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.EnumValueDescriptorProto.name)
-  return name_;
+  return name_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* EnumValueDescriptorProto::release_name() {
   clear_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = name_;
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return name_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* EnumValueDescriptorProto::unsafe_arena_release_name() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_name();
+  return name_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void EnumValueDescriptorProto::set_allocated_name(::std::string* name) {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
+  if (name != NULL) {
+    set_has_name();
+  } else {
+    clear_has_name();
   }
-  if (name) {
+  name_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), name,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.EnumValueDescriptorProto.name)
+}
+inline void EnumValueDescriptorProto::unsafe_arena_set_allocated_name(
+    ::std::string* name) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (name != NULL) {
     set_has_name();
-    name_ = name;
   } else {
     clear_has_name();
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_name();
+  name_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      name, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.EnumValueDescriptorProto.name)
 }
 
@@ -4540,18 +5441,53 @@ inline const ::google::protobuf::EnumValueOptions& EnumValueDescriptorProto::opt
 }
 inline ::google::protobuf::EnumValueOptions* EnumValueDescriptorProto::mutable_options() {
   set_has_options();
-  if (options_ == NULL) options_ = new ::google::protobuf::EnumValueOptions;
+  if (options_ == NULL) {
+    options_ = ::google::protobuf::Arena::CreateMessage< ::google::protobuf::EnumValueOptions >(
+        GetArenaNoVirtual());
+  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.EnumValueDescriptorProto.options)
   return options_;
 }
 inline ::google::protobuf::EnumValueOptions* EnumValueDescriptorProto::release_options() {
   clear_has_options();
+  if (GetArenaNoVirtual() != NULL) {
+    if (options_ == NULL) {
+      return NULL;
+    } else {
+      ::google::protobuf::EnumValueOptions* temp = new ::google::protobuf::EnumValueOptions;
+      temp->MergeFrom(*options_);
+      options_ = NULL;
+      return temp;
+    }
+  } else {
+    ::google::protobuf::EnumValueOptions* temp = options_;
+    options_ = NULL;
+    return temp;
+  }
+}
+inline ::google::protobuf::EnumValueOptions* EnumValueDescriptorProto::unsafe_arena_release_options() {
+  clear_has_options();
   ::google::protobuf::EnumValueOptions* temp = options_;
   options_ = NULL;
   return temp;
 }
 inline void EnumValueDescriptorProto::set_allocated_options(::google::protobuf::EnumValueOptions* options) {
-  delete options_;
+  if (GetArenaNoVirtual() == NULL) {
+    delete options_;
+  }
+  if (options != NULL) {
+    if (GetArenaNoVirtual() != NULL && 
+        ::google::protobuf::Arena::GetArena(options) == NULL) {
+      GetArenaNoVirtual()->Own(options);
+    } else if (GetArenaNoVirtual() !=
+               ::google::protobuf::Arena::GetArena(options)) {
+      ::google::protobuf::EnumValueOptions* new_options = 
+            ::google::protobuf::Arena::CreateMessage< ::google::protobuf::EnumValueOptions >(
+            GetArenaNoVirtual());
+      new_options->CopyFrom(*options);
+      options = new_options;
+    }
+  }
   options_ = options;
   if (options) {
     set_has_options();
@@ -4560,6 +5496,19 @@ inline void EnumValueDescriptorProto::set_allocated_options(::google::protobuf::
   }
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.EnumValueDescriptorProto.options)
 }
+inline void EnumValueDescriptorProto::unsafe_arena_set_allocated_options(
+    ::google::protobuf::EnumValueOptions* options) {
+  if (GetArenaNoVirtual() == NULL) {
+    delete options_;
+  }
+  options_ = options;
+  if (options) {
+    set_has_options();
+  } else {
+    clear_has_options();
+  }
+  // @@protoc_insertion_point(field_unsafe_arena_set_allocated:google.protobuf.EnumValueDescriptorProto.options)
+}
 
 // -------------------------------------------------------------------
 
@@ -4576,68 +5525,67 @@ inline void ServiceDescriptorProto::clear_has_name() {
   _has_bits_[0] &= ~0x00000001u;
 }
 inline void ServiceDescriptorProto::clear_name() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_->clear();
-  }
+  name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_name();
 }
 inline const ::std::string& ServiceDescriptorProto::name() const {
   // @@protoc_insertion_point(field_get:google.protobuf.ServiceDescriptorProto.name)
-  return *name_;
+  return name_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void ServiceDescriptorProto::set_name(const ::std::string& value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.ServiceDescriptorProto.name)
 }
 inline void ServiceDescriptorProto::set_name(const char* value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.ServiceDescriptorProto.name)
 }
-inline void ServiceDescriptorProto::set_name(const char* value, size_t size) {
+inline void ServiceDescriptorProto::set_name(const char* value,
+    size_t size) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(reinterpret_cast<const char*>(value), size);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.ServiceDescriptorProto.name)
 }
 inline ::std::string* ServiceDescriptorProto::mutable_name() {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.ServiceDescriptorProto.name)
-  return name_;
+  return name_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* ServiceDescriptorProto::release_name() {
   clear_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = name_;
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return name_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* ServiceDescriptorProto::unsafe_arena_release_name() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_name();
+  return name_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void ServiceDescriptorProto::set_allocated_name(::std::string* name) {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
+  if (name != NULL) {
+    set_has_name();
+  } else {
+    clear_has_name();
   }
-  if (name) {
+  name_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), name,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.ServiceDescriptorProto.name)
+}
+inline void ServiceDescriptorProto::unsafe_arena_set_allocated_name(
+    ::std::string* name) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (name != NULL) {
     set_has_name();
-    name_ = name;
   } else {
     clear_has_name();
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_name();
+  name_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      name, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.ServiceDescriptorProto.name)
 }
 
@@ -4691,18 +5639,53 @@ inline const ::google::protobuf::ServiceOptions& ServiceDescriptorProto::options
 }
 inline ::google::protobuf::ServiceOptions* ServiceDescriptorProto::mutable_options() {
   set_has_options();
-  if (options_ == NULL) options_ = new ::google::protobuf::ServiceOptions;
+  if (options_ == NULL) {
+    options_ = ::google::protobuf::Arena::CreateMessage< ::google::protobuf::ServiceOptions >(
+        GetArenaNoVirtual());
+  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.ServiceDescriptorProto.options)
   return options_;
 }
 inline ::google::protobuf::ServiceOptions* ServiceDescriptorProto::release_options() {
   clear_has_options();
+  if (GetArenaNoVirtual() != NULL) {
+    if (options_ == NULL) {
+      return NULL;
+    } else {
+      ::google::protobuf::ServiceOptions* temp = new ::google::protobuf::ServiceOptions;
+      temp->MergeFrom(*options_);
+      options_ = NULL;
+      return temp;
+    }
+  } else {
+    ::google::protobuf::ServiceOptions* temp = options_;
+    options_ = NULL;
+    return temp;
+  }
+}
+inline ::google::protobuf::ServiceOptions* ServiceDescriptorProto::unsafe_arena_release_options() {
+  clear_has_options();
   ::google::protobuf::ServiceOptions* temp = options_;
   options_ = NULL;
   return temp;
 }
 inline void ServiceDescriptorProto::set_allocated_options(::google::protobuf::ServiceOptions* options) {
-  delete options_;
+  if (GetArenaNoVirtual() == NULL) {
+    delete options_;
+  }
+  if (options != NULL) {
+    if (GetArenaNoVirtual() != NULL && 
+        ::google::protobuf::Arena::GetArena(options) == NULL) {
+      GetArenaNoVirtual()->Own(options);
+    } else if (GetArenaNoVirtual() !=
+               ::google::protobuf::Arena::GetArena(options)) {
+      ::google::protobuf::ServiceOptions* new_options = 
+            ::google::protobuf::Arena::CreateMessage< ::google::protobuf::ServiceOptions >(
+            GetArenaNoVirtual());
+      new_options->CopyFrom(*options);
+      options = new_options;
+    }
+  }
   options_ = options;
   if (options) {
     set_has_options();
@@ -4711,6 +5694,19 @@ inline void ServiceDescriptorProto::set_allocated_options(::google::protobuf::Se
   }
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.ServiceDescriptorProto.options)
 }
+inline void ServiceDescriptorProto::unsafe_arena_set_allocated_options(
+    ::google::protobuf::ServiceOptions* options) {
+  if (GetArenaNoVirtual() == NULL) {
+    delete options_;
+  }
+  options_ = options;
+  if (options) {
+    set_has_options();
+  } else {
+    clear_has_options();
+  }
+  // @@protoc_insertion_point(field_unsafe_arena_set_allocated:google.protobuf.ServiceDescriptorProto.options)
+}
 
 // -------------------------------------------------------------------
 
@@ -4727,68 +5723,67 @@ inline void MethodDescriptorProto::clear_has_name() {
   _has_bits_[0] &= ~0x00000001u;
 }
 inline void MethodDescriptorProto::clear_name() {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_->clear();
-  }
+  name_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_name();
 }
 inline const ::std::string& MethodDescriptorProto::name() const {
   // @@protoc_insertion_point(field_get:google.protobuf.MethodDescriptorProto.name)
-  return *name_;
+  return name_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void MethodDescriptorProto::set_name(const ::std::string& value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.MethodDescriptorProto.name)
 }
 inline void MethodDescriptorProto::set_name(const char* value) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(value);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.MethodDescriptorProto.name)
 }
-inline void MethodDescriptorProto::set_name(const char* value, size_t size) {
+inline void MethodDescriptorProto::set_name(const char* value,
+    size_t size) {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
-  name_->assign(reinterpret_cast<const char*>(value), size);
+  name_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.MethodDescriptorProto.name)
 }
 inline ::std::string* MethodDescriptorProto::mutable_name() {
   set_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.MethodDescriptorProto.name)
-  return name_;
+  return name_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* MethodDescriptorProto::release_name() {
   clear_has_name();
-  if (name_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = name_;
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return name_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* MethodDescriptorProto::unsafe_arena_release_name() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_name();
+  return name_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void MethodDescriptorProto::set_allocated_name(::std::string* name) {
-  if (name_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_;
+  if (name != NULL) {
+    set_has_name();
+  } else {
+    clear_has_name();
   }
-  if (name) {
+  name_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), name,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.MethodDescriptorProto.name)
+}
+inline void MethodDescriptorProto::unsafe_arena_set_allocated_name(
+    ::std::string* name) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (name != NULL) {
     set_has_name();
-    name_ = name;
   } else {
     clear_has_name();
-    name_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_name();
+  name_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      name, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.MethodDescriptorProto.name)
 }
 
@@ -4803,68 +5798,67 @@ inline void MethodDescriptorProto::clear_has_input_type() {
   _has_bits_[0] &= ~0x00000002u;
 }
 inline void MethodDescriptorProto::clear_input_type() {
-  if (input_type_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    input_type_->clear();
-  }
+  input_type_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_input_type();
 }
 inline const ::std::string& MethodDescriptorProto::input_type() const {
   // @@protoc_insertion_point(field_get:google.protobuf.MethodDescriptorProto.input_type)
-  return *input_type_;
+  return input_type_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void MethodDescriptorProto::set_input_type(const ::std::string& value) {
   set_has_input_type();
-  if (input_type_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    input_type_ = new ::std::string;
-  }
-  input_type_->assign(value);
+  input_type_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.MethodDescriptorProto.input_type)
 }
 inline void MethodDescriptorProto::set_input_type(const char* value) {
   set_has_input_type();
-  if (input_type_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    input_type_ = new ::std::string;
-  }
-  input_type_->assign(value);
+  input_type_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.MethodDescriptorProto.input_type)
 }
-inline void MethodDescriptorProto::set_input_type(const char* value, size_t size) {
+inline void MethodDescriptorProto::set_input_type(const char* value,
+    size_t size) {
   set_has_input_type();
-  if (input_type_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    input_type_ = new ::std::string;
-  }
-  input_type_->assign(reinterpret_cast<const char*>(value), size);
+  input_type_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.MethodDescriptorProto.input_type)
 }
 inline ::std::string* MethodDescriptorProto::mutable_input_type() {
   set_has_input_type();
-  if (input_type_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    input_type_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.MethodDescriptorProto.input_type)
-  return input_type_;
+  return input_type_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* MethodDescriptorProto::release_input_type() {
   clear_has_input_type();
-  if (input_type_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = input_type_;
-    input_type_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return input_type_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* MethodDescriptorProto::unsafe_arena_release_input_type() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_input_type();
+  return input_type_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void MethodDescriptorProto::set_allocated_input_type(::std::string* input_type) {
-  if (input_type_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete input_type_;
+  if (input_type != NULL) {
+    set_has_input_type();
+  } else {
+    clear_has_input_type();
   }
-  if (input_type) {
+  input_type_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), input_type,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.MethodDescriptorProto.input_type)
+}
+inline void MethodDescriptorProto::unsafe_arena_set_allocated_input_type(
+    ::std::string* input_type) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (input_type != NULL) {
     set_has_input_type();
-    input_type_ = input_type;
   } else {
     clear_has_input_type();
-    input_type_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_input_type();
+  input_type_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      input_type, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.MethodDescriptorProto.input_type)
 }
 
@@ -4879,68 +5873,67 @@ inline void MethodDescriptorProto::clear_has_output_type() {
   _has_bits_[0] &= ~0x00000004u;
 }
 inline void MethodDescriptorProto::clear_output_type() {
-  if (output_type_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    output_type_->clear();
-  }
+  output_type_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_output_type();
 }
 inline const ::std::string& MethodDescriptorProto::output_type() const {
   // @@protoc_insertion_point(field_get:google.protobuf.MethodDescriptorProto.output_type)
-  return *output_type_;
+  return output_type_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void MethodDescriptorProto::set_output_type(const ::std::string& value) {
   set_has_output_type();
-  if (output_type_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    output_type_ = new ::std::string;
-  }
-  output_type_->assign(value);
+  output_type_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.MethodDescriptorProto.output_type)
 }
 inline void MethodDescriptorProto::set_output_type(const char* value) {
   set_has_output_type();
-  if (output_type_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    output_type_ = new ::std::string;
-  }
-  output_type_->assign(value);
+  output_type_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.MethodDescriptorProto.output_type)
 }
-inline void MethodDescriptorProto::set_output_type(const char* value, size_t size) {
+inline void MethodDescriptorProto::set_output_type(const char* value,
+    size_t size) {
   set_has_output_type();
-  if (output_type_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    output_type_ = new ::std::string;
-  }
-  output_type_->assign(reinterpret_cast<const char*>(value), size);
+  output_type_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.MethodDescriptorProto.output_type)
 }
 inline ::std::string* MethodDescriptorProto::mutable_output_type() {
   set_has_output_type();
-  if (output_type_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    output_type_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.MethodDescriptorProto.output_type)
-  return output_type_;
+  return output_type_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* MethodDescriptorProto::release_output_type() {
   clear_has_output_type();
-  if (output_type_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = output_type_;
-    output_type_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return output_type_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* MethodDescriptorProto::unsafe_arena_release_output_type() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_output_type();
+  return output_type_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void MethodDescriptorProto::set_allocated_output_type(::std::string* output_type) {
-  if (output_type_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete output_type_;
+  if (output_type != NULL) {
+    set_has_output_type();
+  } else {
+    clear_has_output_type();
   }
-  if (output_type) {
+  output_type_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), output_type,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.MethodDescriptorProto.output_type)
+}
+inline void MethodDescriptorProto::unsafe_arena_set_allocated_output_type(
+    ::std::string* output_type) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (output_type != NULL) {
     set_has_output_type();
-    output_type_ = output_type;
   } else {
     clear_has_output_type();
-    output_type_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_output_type();
+  output_type_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      output_type, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.MethodDescriptorProto.output_type)
 }
 
@@ -4964,18 +5957,53 @@ inline const ::google::protobuf::MethodOptions& MethodDescriptorProto::options()
 }
 inline ::google::protobuf::MethodOptions* MethodDescriptorProto::mutable_options() {
   set_has_options();
-  if (options_ == NULL) options_ = new ::google::protobuf::MethodOptions;
+  if (options_ == NULL) {
+    options_ = ::google::protobuf::Arena::CreateMessage< ::google::protobuf::MethodOptions >(
+        GetArenaNoVirtual());
+  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.MethodDescriptorProto.options)
   return options_;
 }
 inline ::google::protobuf::MethodOptions* MethodDescriptorProto::release_options() {
   clear_has_options();
+  if (GetArenaNoVirtual() != NULL) {
+    if (options_ == NULL) {
+      return NULL;
+    } else {
+      ::google::protobuf::MethodOptions* temp = new ::google::protobuf::MethodOptions;
+      temp->MergeFrom(*options_);
+      options_ = NULL;
+      return temp;
+    }
+  } else {
+    ::google::protobuf::MethodOptions* temp = options_;
+    options_ = NULL;
+    return temp;
+  }
+}
+inline ::google::protobuf::MethodOptions* MethodDescriptorProto::unsafe_arena_release_options() {
+  clear_has_options();
   ::google::protobuf::MethodOptions* temp = options_;
   options_ = NULL;
   return temp;
 }
 inline void MethodDescriptorProto::set_allocated_options(::google::protobuf::MethodOptions* options) {
-  delete options_;
+  if (GetArenaNoVirtual() == NULL) {
+    delete options_;
+  }
+  if (options != NULL) {
+    if (GetArenaNoVirtual() != NULL && 
+        ::google::protobuf::Arena::GetArena(options) == NULL) {
+      GetArenaNoVirtual()->Own(options);
+    } else if (GetArenaNoVirtual() !=
+               ::google::protobuf::Arena::GetArena(options)) {
+      ::google::protobuf::MethodOptions* new_options = 
+            ::google::protobuf::Arena::CreateMessage< ::google::protobuf::MethodOptions >(
+            GetArenaNoVirtual());
+      new_options->CopyFrom(*options);
+      options = new_options;
+    }
+  }
   options_ = options;
   if (options) {
     set_has_options();
@@ -4984,6 +6012,19 @@ inline void MethodDescriptorProto::set_allocated_options(::google::protobuf::Met
   }
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.MethodDescriptorProto.options)
 }
+inline void MethodDescriptorProto::unsafe_arena_set_allocated_options(
+    ::google::protobuf::MethodOptions* options) {
+  if (GetArenaNoVirtual() == NULL) {
+    delete options_;
+  }
+  options_ = options;
+  if (options) {
+    set_has_options();
+  } else {
+    clear_has_options();
+  }
+  // @@protoc_insertion_point(field_unsafe_arena_set_allocated:google.protobuf.MethodDescriptorProto.options)
+}
 
 // -------------------------------------------------------------------
 
@@ -5000,68 +6041,67 @@ inline void FileOptions::clear_has_java_package() {
   _has_bits_[0] &= ~0x00000001u;
 }
 inline void FileOptions::clear_java_package() {
-  if (java_package_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    java_package_->clear();
-  }
+  java_package_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_java_package();
 }
 inline const ::std::string& FileOptions::java_package() const {
   // @@protoc_insertion_point(field_get:google.protobuf.FileOptions.java_package)
-  return *java_package_;
+  return java_package_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void FileOptions::set_java_package(const ::std::string& value) {
   set_has_java_package();
-  if (java_package_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    java_package_ = new ::std::string;
-  }
-  java_package_->assign(value);
+  java_package_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.FileOptions.java_package)
 }
 inline void FileOptions::set_java_package(const char* value) {
   set_has_java_package();
-  if (java_package_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    java_package_ = new ::std::string;
-  }
-  java_package_->assign(value);
+  java_package_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.FileOptions.java_package)
 }
-inline void FileOptions::set_java_package(const char* value, size_t size) {
+inline void FileOptions::set_java_package(const char* value,
+    size_t size) {
   set_has_java_package();
-  if (java_package_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    java_package_ = new ::std::string;
-  }
-  java_package_->assign(reinterpret_cast<const char*>(value), size);
+  java_package_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.FileOptions.java_package)
 }
 inline ::std::string* FileOptions::mutable_java_package() {
   set_has_java_package();
-  if (java_package_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    java_package_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.FileOptions.java_package)
-  return java_package_;
+  return java_package_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* FileOptions::release_java_package() {
   clear_has_java_package();
-  if (java_package_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = java_package_;
-    java_package_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return java_package_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* FileOptions::unsafe_arena_release_java_package() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_java_package();
+  return java_package_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void FileOptions::set_allocated_java_package(::std::string* java_package) {
-  if (java_package_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete java_package_;
+  if (java_package != NULL) {
+    set_has_java_package();
+  } else {
+    clear_has_java_package();
   }
-  if (java_package) {
+  java_package_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), java_package,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.FileOptions.java_package)
+}
+inline void FileOptions::unsafe_arena_set_allocated_java_package(
+    ::std::string* java_package) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (java_package != NULL) {
     set_has_java_package();
-    java_package_ = java_package;
   } else {
     clear_has_java_package();
-    java_package_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_java_package();
+  java_package_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      java_package, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.FileOptions.java_package)
 }
 
@@ -5076,68 +6116,67 @@ inline void FileOptions::clear_has_java_outer_classname() {
   _has_bits_[0] &= ~0x00000002u;
 }
 inline void FileOptions::clear_java_outer_classname() {
-  if (java_outer_classname_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    java_outer_classname_->clear();
-  }
+  java_outer_classname_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_java_outer_classname();
 }
 inline const ::std::string& FileOptions::java_outer_classname() const {
   // @@protoc_insertion_point(field_get:google.protobuf.FileOptions.java_outer_classname)
-  return *java_outer_classname_;
+  return java_outer_classname_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void FileOptions::set_java_outer_classname(const ::std::string& value) {
   set_has_java_outer_classname();
-  if (java_outer_classname_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    java_outer_classname_ = new ::std::string;
-  }
-  java_outer_classname_->assign(value);
+  java_outer_classname_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.FileOptions.java_outer_classname)
 }
 inline void FileOptions::set_java_outer_classname(const char* value) {
   set_has_java_outer_classname();
-  if (java_outer_classname_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    java_outer_classname_ = new ::std::string;
-  }
-  java_outer_classname_->assign(value);
+  java_outer_classname_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.FileOptions.java_outer_classname)
 }
-inline void FileOptions::set_java_outer_classname(const char* value, size_t size) {
+inline void FileOptions::set_java_outer_classname(const char* value,
+    size_t size) {
   set_has_java_outer_classname();
-  if (java_outer_classname_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    java_outer_classname_ = new ::std::string;
-  }
-  java_outer_classname_->assign(reinterpret_cast<const char*>(value), size);
+  java_outer_classname_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.FileOptions.java_outer_classname)
 }
 inline ::std::string* FileOptions::mutable_java_outer_classname() {
   set_has_java_outer_classname();
-  if (java_outer_classname_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    java_outer_classname_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.FileOptions.java_outer_classname)
-  return java_outer_classname_;
+  return java_outer_classname_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* FileOptions::release_java_outer_classname() {
   clear_has_java_outer_classname();
-  if (java_outer_classname_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = java_outer_classname_;
-    java_outer_classname_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return java_outer_classname_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* FileOptions::unsafe_arena_release_java_outer_classname() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_java_outer_classname();
+  return java_outer_classname_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void FileOptions::set_allocated_java_outer_classname(::std::string* java_outer_classname) {
-  if (java_outer_classname_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete java_outer_classname_;
+  if (java_outer_classname != NULL) {
+    set_has_java_outer_classname();
+  } else {
+    clear_has_java_outer_classname();
   }
-  if (java_outer_classname) {
+  java_outer_classname_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), java_outer_classname,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.FileOptions.java_outer_classname)
+}
+inline void FileOptions::unsafe_arena_set_allocated_java_outer_classname(
+    ::std::string* java_outer_classname) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (java_outer_classname != NULL) {
     set_has_java_outer_classname();
-    java_outer_classname_ = java_outer_classname;
   } else {
     clear_has_java_outer_classname();
-    java_outer_classname_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_java_outer_classname();
+  java_outer_classname_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      java_outer_classname, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.FileOptions.java_outer_classname)
 }
 
@@ -5249,68 +6288,67 @@ inline void FileOptions::clear_has_go_package() {
   _has_bits_[0] &= ~0x00000040u;
 }
 inline void FileOptions::clear_go_package() {
-  if (go_package_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    go_package_->clear();
-  }
+  go_package_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_go_package();
 }
 inline const ::std::string& FileOptions::go_package() const {
   // @@protoc_insertion_point(field_get:google.protobuf.FileOptions.go_package)
-  return *go_package_;
+  return go_package_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void FileOptions::set_go_package(const ::std::string& value) {
   set_has_go_package();
-  if (go_package_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    go_package_ = new ::std::string;
-  }
-  go_package_->assign(value);
+  go_package_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.FileOptions.go_package)
 }
 inline void FileOptions::set_go_package(const char* value) {
   set_has_go_package();
-  if (go_package_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    go_package_ = new ::std::string;
-  }
-  go_package_->assign(value);
+  go_package_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.FileOptions.go_package)
 }
-inline void FileOptions::set_go_package(const char* value, size_t size) {
+inline void FileOptions::set_go_package(const char* value,
+    size_t size) {
   set_has_go_package();
-  if (go_package_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    go_package_ = new ::std::string;
-  }
-  go_package_->assign(reinterpret_cast<const char*>(value), size);
+  go_package_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.FileOptions.go_package)
 }
 inline ::std::string* FileOptions::mutable_go_package() {
   set_has_go_package();
-  if (go_package_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    go_package_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.FileOptions.go_package)
-  return go_package_;
+  return go_package_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* FileOptions::release_go_package() {
   clear_has_go_package();
-  if (go_package_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = go_package_;
-    go_package_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return go_package_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* FileOptions::unsafe_arena_release_go_package() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_go_package();
+  return go_package_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void FileOptions::set_allocated_go_package(::std::string* go_package) {
-  if (go_package_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete go_package_;
+  if (go_package != NULL) {
+    set_has_go_package();
+  } else {
+    clear_has_go_package();
   }
-  if (go_package) {
+  go_package_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), go_package,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.FileOptions.go_package)
+}
+inline void FileOptions::unsafe_arena_set_allocated_go_package(
+    ::std::string* go_package) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (go_package != NULL) {
     set_has_go_package();
-    go_package_ = go_package;
   } else {
     clear_has_go_package();
-    go_package_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_go_package();
+  go_package_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      go_package, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.FileOptions.go_package)
 }
 
@@ -5516,6 +6554,30 @@ inline void MessageOptions::set_deprecated(bool value) {
   // @@protoc_insertion_point(field_set:google.protobuf.MessageOptions.deprecated)
 }
 
+// optional bool map_entry = 7;
+inline bool MessageOptions::has_map_entry() const {
+  return (_has_bits_[0] & 0x00000008u) != 0;
+}
+inline void MessageOptions::set_has_map_entry() {
+  _has_bits_[0] |= 0x00000008u;
+}
+inline void MessageOptions::clear_has_map_entry() {
+  _has_bits_[0] &= ~0x00000008u;
+}
+inline void MessageOptions::clear_map_entry() {
+  map_entry_ = false;
+  clear_has_map_entry();
+}
+inline bool MessageOptions::map_entry() const {
+  // @@protoc_insertion_point(field_get:google.protobuf.MessageOptions.map_entry)
+  return map_entry_;
+}
+inline void MessageOptions::set_map_entry(bool value) {
+  set_has_map_entry();
+  map_entry_ = value;
+  // @@protoc_insertion_point(field_set:google.protobuf.MessageOptions.map_entry)
+}
+
 // repeated .google.protobuf.UninterpretedOption uninterpreted_option = 999;
 inline int MessageOptions::uninterpreted_option_size() const {
   return uninterpreted_option_.size();
@@ -5647,91 +6709,15 @@ inline void FieldOptions::set_deprecated(bool value) {
   // @@protoc_insertion_point(field_set:google.protobuf.FieldOptions.deprecated)
 }
 
-// optional string experimental_map_key = 9;
-inline bool FieldOptions::has_experimental_map_key() const {
-  return (_has_bits_[0] & 0x00000010u) != 0;
-}
-inline void FieldOptions::set_has_experimental_map_key() {
-  _has_bits_[0] |= 0x00000010u;
-}
-inline void FieldOptions::clear_has_experimental_map_key() {
-  _has_bits_[0] &= ~0x00000010u;
-}
-inline void FieldOptions::clear_experimental_map_key() {
-  if (experimental_map_key_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    experimental_map_key_->clear();
-  }
-  clear_has_experimental_map_key();
-}
-inline const ::std::string& FieldOptions::experimental_map_key() const {
-  // @@protoc_insertion_point(field_get:google.protobuf.FieldOptions.experimental_map_key)
-  return *experimental_map_key_;
-}
-inline void FieldOptions::set_experimental_map_key(const ::std::string& value) {
-  set_has_experimental_map_key();
-  if (experimental_map_key_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    experimental_map_key_ = new ::std::string;
-  }
-  experimental_map_key_->assign(value);
-  // @@protoc_insertion_point(field_set:google.protobuf.FieldOptions.experimental_map_key)
-}
-inline void FieldOptions::set_experimental_map_key(const char* value) {
-  set_has_experimental_map_key();
-  if (experimental_map_key_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    experimental_map_key_ = new ::std::string;
-  }
-  experimental_map_key_->assign(value);
-  // @@protoc_insertion_point(field_set_char:google.protobuf.FieldOptions.experimental_map_key)
-}
-inline void FieldOptions::set_experimental_map_key(const char* value, size_t size) {
-  set_has_experimental_map_key();
-  if (experimental_map_key_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    experimental_map_key_ = new ::std::string;
-  }
-  experimental_map_key_->assign(reinterpret_cast<const char*>(value), size);
-  // @@protoc_insertion_point(field_set_pointer:google.protobuf.FieldOptions.experimental_map_key)
-}
-inline ::std::string* FieldOptions::mutable_experimental_map_key() {
-  set_has_experimental_map_key();
-  if (experimental_map_key_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    experimental_map_key_ = new ::std::string;
-  }
-  // @@protoc_insertion_point(field_mutable:google.protobuf.FieldOptions.experimental_map_key)
-  return experimental_map_key_;
-}
-inline ::std::string* FieldOptions::release_experimental_map_key() {
-  clear_has_experimental_map_key();
-  if (experimental_map_key_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = experimental_map_key_;
-    experimental_map_key_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
-}
-inline void FieldOptions::set_allocated_experimental_map_key(::std::string* experimental_map_key) {
-  if (experimental_map_key_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete experimental_map_key_;
-  }
-  if (experimental_map_key) {
-    set_has_experimental_map_key();
-    experimental_map_key_ = experimental_map_key;
-  } else {
-    clear_has_experimental_map_key();
-    experimental_map_key_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-  }
-  // @@protoc_insertion_point(field_set_allocated:google.protobuf.FieldOptions.experimental_map_key)
-}
-
 // optional bool weak = 10 [default = false];
 inline bool FieldOptions::has_weak() const {
-  return (_has_bits_[0] & 0x00000020u) != 0;
+  return (_has_bits_[0] & 0x00000010u) != 0;
 }
 inline void FieldOptions::set_has_weak() {
-  _has_bits_[0] |= 0x00000020u;
+  _has_bits_[0] |= 0x00000010u;
 }
 inline void FieldOptions::clear_has_weak() {
-  _has_bits_[0] &= ~0x00000020u;
+  _has_bits_[0] &= ~0x00000010u;
 }
 inline void FieldOptions::clear_weak() {
   weak_ = false;
@@ -6048,68 +7034,67 @@ inline void UninterpretedOption_NamePart::clear_has_name_part() {
   _has_bits_[0] &= ~0x00000001u;
 }
 inline void UninterpretedOption_NamePart::clear_name_part() {
-  if (name_part_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_part_->clear();
-  }
+  name_part_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_name_part();
 }
 inline const ::std::string& UninterpretedOption_NamePart::name_part() const {
   // @@protoc_insertion_point(field_get:google.protobuf.UninterpretedOption.NamePart.name_part)
-  return *name_part_;
+  return name_part_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void UninterpretedOption_NamePart::set_name_part(const ::std::string& value) {
   set_has_name_part();
-  if (name_part_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_part_ = new ::std::string;
-  }
-  name_part_->assign(value);
+  name_part_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.UninterpretedOption.NamePart.name_part)
 }
 inline void UninterpretedOption_NamePart::set_name_part(const char* value) {
   set_has_name_part();
-  if (name_part_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_part_ = new ::std::string;
-  }
-  name_part_->assign(value);
+  name_part_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.UninterpretedOption.NamePart.name_part)
 }
-inline void UninterpretedOption_NamePart::set_name_part(const char* value, size_t size) {
+inline void UninterpretedOption_NamePart::set_name_part(const char* value,
+    size_t size) {
   set_has_name_part();
-  if (name_part_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_part_ = new ::std::string;
-  }
-  name_part_->assign(reinterpret_cast<const char*>(value), size);
+  name_part_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.UninterpretedOption.NamePart.name_part)
 }
 inline ::std::string* UninterpretedOption_NamePart::mutable_name_part() {
   set_has_name_part();
-  if (name_part_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    name_part_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.UninterpretedOption.NamePart.name_part)
-  return name_part_;
+  return name_part_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* UninterpretedOption_NamePart::release_name_part() {
   clear_has_name_part();
-  if (name_part_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = name_part_;
-    name_part_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return name_part_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* UninterpretedOption_NamePart::unsafe_arena_release_name_part() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_name_part();
+  return name_part_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void UninterpretedOption_NamePart::set_allocated_name_part(::std::string* name_part) {
-  if (name_part_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete name_part_;
+  if (name_part != NULL) {
+    set_has_name_part();
+  } else {
+    clear_has_name_part();
   }
-  if (name_part) {
+  name_part_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), name_part,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.UninterpretedOption.NamePart.name_part)
+}
+inline void UninterpretedOption_NamePart::unsafe_arena_set_allocated_name_part(
+    ::std::string* name_part) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (name_part != NULL) {
     set_has_name_part();
-    name_part_ = name_part;
   } else {
     clear_has_name_part();
-    name_part_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_name_part();
+  name_part_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      name_part, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.UninterpretedOption.NamePart.name_part)
 }
 
@@ -6182,68 +7167,67 @@ inline void UninterpretedOption::clear_has_identifier_value() {
   _has_bits_[0] &= ~0x00000002u;
 }
 inline void UninterpretedOption::clear_identifier_value() {
-  if (identifier_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    identifier_value_->clear();
-  }
+  identifier_value_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_identifier_value();
 }
 inline const ::std::string& UninterpretedOption::identifier_value() const {
   // @@protoc_insertion_point(field_get:google.protobuf.UninterpretedOption.identifier_value)
-  return *identifier_value_;
+  return identifier_value_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void UninterpretedOption::set_identifier_value(const ::std::string& value) {
   set_has_identifier_value();
-  if (identifier_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    identifier_value_ = new ::std::string;
-  }
-  identifier_value_->assign(value);
+  identifier_value_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.UninterpretedOption.identifier_value)
 }
 inline void UninterpretedOption::set_identifier_value(const char* value) {
   set_has_identifier_value();
-  if (identifier_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    identifier_value_ = new ::std::string;
-  }
-  identifier_value_->assign(value);
+  identifier_value_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.UninterpretedOption.identifier_value)
 }
-inline void UninterpretedOption::set_identifier_value(const char* value, size_t size) {
+inline void UninterpretedOption::set_identifier_value(const char* value,
+    size_t size) {
   set_has_identifier_value();
-  if (identifier_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    identifier_value_ = new ::std::string;
-  }
-  identifier_value_->assign(reinterpret_cast<const char*>(value), size);
+  identifier_value_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.UninterpretedOption.identifier_value)
 }
 inline ::std::string* UninterpretedOption::mutable_identifier_value() {
   set_has_identifier_value();
-  if (identifier_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    identifier_value_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.UninterpretedOption.identifier_value)
-  return identifier_value_;
+  return identifier_value_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* UninterpretedOption::release_identifier_value() {
   clear_has_identifier_value();
-  if (identifier_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = identifier_value_;
-    identifier_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return identifier_value_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* UninterpretedOption::unsafe_arena_release_identifier_value() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_identifier_value();
+  return identifier_value_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void UninterpretedOption::set_allocated_identifier_value(::std::string* identifier_value) {
-  if (identifier_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete identifier_value_;
+  if (identifier_value != NULL) {
+    set_has_identifier_value();
+  } else {
+    clear_has_identifier_value();
   }
-  if (identifier_value) {
+  identifier_value_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), identifier_value,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.UninterpretedOption.identifier_value)
+}
+inline void UninterpretedOption::unsafe_arena_set_allocated_identifier_value(
+    ::std::string* identifier_value) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (identifier_value != NULL) {
     set_has_identifier_value();
-    identifier_value_ = identifier_value;
   } else {
     clear_has_identifier_value();
-    identifier_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_identifier_value();
+  identifier_value_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      identifier_value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.UninterpretedOption.identifier_value)
 }
 
@@ -6330,68 +7314,67 @@ inline void UninterpretedOption::clear_has_string_value() {
   _has_bits_[0] &= ~0x00000020u;
 }
 inline void UninterpretedOption::clear_string_value() {
-  if (string_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    string_value_->clear();
-  }
+  string_value_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_string_value();
 }
 inline const ::std::string& UninterpretedOption::string_value() const {
   // @@protoc_insertion_point(field_get:google.protobuf.UninterpretedOption.string_value)
-  return *string_value_;
+  return string_value_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void UninterpretedOption::set_string_value(const ::std::string& value) {
   set_has_string_value();
-  if (string_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    string_value_ = new ::std::string;
-  }
-  string_value_->assign(value);
+  string_value_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.UninterpretedOption.string_value)
 }
 inline void UninterpretedOption::set_string_value(const char* value) {
   set_has_string_value();
-  if (string_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    string_value_ = new ::std::string;
-  }
-  string_value_->assign(value);
+  string_value_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.UninterpretedOption.string_value)
 }
-inline void UninterpretedOption::set_string_value(const void* value, size_t size) {
+inline void UninterpretedOption::set_string_value(const void* value,
+    size_t size) {
   set_has_string_value();
-  if (string_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    string_value_ = new ::std::string;
-  }
-  string_value_->assign(reinterpret_cast<const char*>(value), size);
+  string_value_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.UninterpretedOption.string_value)
 }
 inline ::std::string* UninterpretedOption::mutable_string_value() {
   set_has_string_value();
-  if (string_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    string_value_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.UninterpretedOption.string_value)
-  return string_value_;
+  return string_value_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* UninterpretedOption::release_string_value() {
   clear_has_string_value();
-  if (string_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = string_value_;
-    string_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return string_value_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* UninterpretedOption::unsafe_arena_release_string_value() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_string_value();
+  return string_value_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void UninterpretedOption::set_allocated_string_value(::std::string* string_value) {
-  if (string_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete string_value_;
+  if (string_value != NULL) {
+    set_has_string_value();
+  } else {
+    clear_has_string_value();
   }
-  if (string_value) {
+  string_value_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), string_value,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.UninterpretedOption.string_value)
+}
+inline void UninterpretedOption::unsafe_arena_set_allocated_string_value(
+    ::std::string* string_value) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (string_value != NULL) {
     set_has_string_value();
-    string_value_ = string_value;
   } else {
     clear_has_string_value();
-    string_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_string_value();
+  string_value_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      string_value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.UninterpretedOption.string_value)
 }
 
@@ -6406,68 +7389,67 @@ inline void UninterpretedOption::clear_has_aggregate_value() {
   _has_bits_[0] &= ~0x00000040u;
 }
 inline void UninterpretedOption::clear_aggregate_value() {
-  if (aggregate_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    aggregate_value_->clear();
-  }
+  aggregate_value_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_aggregate_value();
 }
 inline const ::std::string& UninterpretedOption::aggregate_value() const {
   // @@protoc_insertion_point(field_get:google.protobuf.UninterpretedOption.aggregate_value)
-  return *aggregate_value_;
+  return aggregate_value_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void UninterpretedOption::set_aggregate_value(const ::std::string& value) {
   set_has_aggregate_value();
-  if (aggregate_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    aggregate_value_ = new ::std::string;
-  }
-  aggregate_value_->assign(value);
+  aggregate_value_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.UninterpretedOption.aggregate_value)
 }
 inline void UninterpretedOption::set_aggregate_value(const char* value) {
   set_has_aggregate_value();
-  if (aggregate_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    aggregate_value_ = new ::std::string;
-  }
-  aggregate_value_->assign(value);
+  aggregate_value_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.UninterpretedOption.aggregate_value)
 }
-inline void UninterpretedOption::set_aggregate_value(const char* value, size_t size) {
+inline void UninterpretedOption::set_aggregate_value(const char* value,
+    size_t size) {
   set_has_aggregate_value();
-  if (aggregate_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    aggregate_value_ = new ::std::string;
-  }
-  aggregate_value_->assign(reinterpret_cast<const char*>(value), size);
+  aggregate_value_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.UninterpretedOption.aggregate_value)
 }
 inline ::std::string* UninterpretedOption::mutable_aggregate_value() {
   set_has_aggregate_value();
-  if (aggregate_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    aggregate_value_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.UninterpretedOption.aggregate_value)
-  return aggregate_value_;
+  return aggregate_value_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* UninterpretedOption::release_aggregate_value() {
   clear_has_aggregate_value();
-  if (aggregate_value_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = aggregate_value_;
-    aggregate_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return aggregate_value_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* UninterpretedOption::unsafe_arena_release_aggregate_value() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_aggregate_value();
+  return aggregate_value_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void UninterpretedOption::set_allocated_aggregate_value(::std::string* aggregate_value) {
-  if (aggregate_value_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete aggregate_value_;
+  if (aggregate_value != NULL) {
+    set_has_aggregate_value();
+  } else {
+    clear_has_aggregate_value();
   }
-  if (aggregate_value) {
+  aggregate_value_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), aggregate_value,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.UninterpretedOption.aggregate_value)
+}
+inline void UninterpretedOption::unsafe_arena_set_allocated_aggregate_value(
+    ::std::string* aggregate_value) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (aggregate_value != NULL) {
     set_has_aggregate_value();
-    aggregate_value_ = aggregate_value;
   } else {
     clear_has_aggregate_value();
-    aggregate_value_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_aggregate_value();
+  aggregate_value_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      aggregate_value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.UninterpretedOption.aggregate_value)
 }
 
@@ -6546,68 +7528,67 @@ inline void SourceCodeInfo_Location::clear_has_leading_comments() {
   _has_bits_[0] &= ~0x00000004u;
 }
 inline void SourceCodeInfo_Location::clear_leading_comments() {
-  if (leading_comments_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    leading_comments_->clear();
-  }
+  leading_comments_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_leading_comments();
 }
 inline const ::std::string& SourceCodeInfo_Location::leading_comments() const {
   // @@protoc_insertion_point(field_get:google.protobuf.SourceCodeInfo.Location.leading_comments)
-  return *leading_comments_;
+  return leading_comments_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void SourceCodeInfo_Location::set_leading_comments(const ::std::string& value) {
   set_has_leading_comments();
-  if (leading_comments_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    leading_comments_ = new ::std::string;
-  }
-  leading_comments_->assign(value);
+  leading_comments_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.SourceCodeInfo.Location.leading_comments)
 }
 inline void SourceCodeInfo_Location::set_leading_comments(const char* value) {
   set_has_leading_comments();
-  if (leading_comments_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    leading_comments_ = new ::std::string;
-  }
-  leading_comments_->assign(value);
+  leading_comments_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.SourceCodeInfo.Location.leading_comments)
 }
-inline void SourceCodeInfo_Location::set_leading_comments(const char* value, size_t size) {
+inline void SourceCodeInfo_Location::set_leading_comments(const char* value,
+    size_t size) {
   set_has_leading_comments();
-  if (leading_comments_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    leading_comments_ = new ::std::string;
-  }
-  leading_comments_->assign(reinterpret_cast<const char*>(value), size);
+  leading_comments_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.SourceCodeInfo.Location.leading_comments)
 }
 inline ::std::string* SourceCodeInfo_Location::mutable_leading_comments() {
   set_has_leading_comments();
-  if (leading_comments_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    leading_comments_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.SourceCodeInfo.Location.leading_comments)
-  return leading_comments_;
+  return leading_comments_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* SourceCodeInfo_Location::release_leading_comments() {
   clear_has_leading_comments();
-  if (leading_comments_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = leading_comments_;
-    leading_comments_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return leading_comments_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* SourceCodeInfo_Location::unsafe_arena_release_leading_comments() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_leading_comments();
+  return leading_comments_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void SourceCodeInfo_Location::set_allocated_leading_comments(::std::string* leading_comments) {
-  if (leading_comments_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete leading_comments_;
+  if (leading_comments != NULL) {
+    set_has_leading_comments();
+  } else {
+    clear_has_leading_comments();
   }
-  if (leading_comments) {
+  leading_comments_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), leading_comments,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.SourceCodeInfo.Location.leading_comments)
+}
+inline void SourceCodeInfo_Location::unsafe_arena_set_allocated_leading_comments(
+    ::std::string* leading_comments) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (leading_comments != NULL) {
     set_has_leading_comments();
-    leading_comments_ = leading_comments;
   } else {
     clear_has_leading_comments();
-    leading_comments_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_leading_comments();
+  leading_comments_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      leading_comments, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.SourceCodeInfo.Location.leading_comments)
 }
 
@@ -6622,68 +7603,67 @@ inline void SourceCodeInfo_Location::clear_has_trailing_comments() {
   _has_bits_[0] &= ~0x00000008u;
 }
 inline void SourceCodeInfo_Location::clear_trailing_comments() {
-  if (trailing_comments_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    trailing_comments_->clear();
-  }
+  trailing_comments_.ClearToEmpty(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
   clear_has_trailing_comments();
 }
 inline const ::std::string& SourceCodeInfo_Location::trailing_comments() const {
   // @@protoc_insertion_point(field_get:google.protobuf.SourceCodeInfo.Location.trailing_comments)
-  return *trailing_comments_;
+  return trailing_comments_.Get(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
 }
 inline void SourceCodeInfo_Location::set_trailing_comments(const ::std::string& value) {
   set_has_trailing_comments();
-  if (trailing_comments_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    trailing_comments_ = new ::std::string;
-  }
-  trailing_comments_->assign(value);
+  trailing_comments_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), value, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set:google.protobuf.SourceCodeInfo.Location.trailing_comments)
 }
 inline void SourceCodeInfo_Location::set_trailing_comments(const char* value) {
   set_has_trailing_comments();
-  if (trailing_comments_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    trailing_comments_ = new ::std::string;
-  }
-  trailing_comments_->assign(value);
+  trailing_comments_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(value),
+              GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_char:google.protobuf.SourceCodeInfo.Location.trailing_comments)
 }
-inline void SourceCodeInfo_Location::set_trailing_comments(const char* value, size_t size) {
+inline void SourceCodeInfo_Location::set_trailing_comments(const char* value,
+    size_t size) {
   set_has_trailing_comments();
-  if (trailing_comments_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    trailing_comments_ = new ::std::string;
-  }
-  trailing_comments_->assign(reinterpret_cast<const char*>(value), size);
+  trailing_comments_.Set(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), ::std::string(
+      reinterpret_cast<const char*>(value), size), GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_pointer:google.protobuf.SourceCodeInfo.Location.trailing_comments)
 }
 inline ::std::string* SourceCodeInfo_Location::mutable_trailing_comments() {
   set_has_trailing_comments();
-  if (trailing_comments_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    trailing_comments_ = new ::std::string;
-  }
   // @@protoc_insertion_point(field_mutable:google.protobuf.SourceCodeInfo.Location.trailing_comments)
-  return trailing_comments_;
+  return trailing_comments_.Mutable(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
 }
 inline ::std::string* SourceCodeInfo_Location::release_trailing_comments() {
   clear_has_trailing_comments();
-  if (trailing_comments_ == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    return NULL;
-  } else {
-    ::std::string* temp = trailing_comments_;
-    trailing_comments_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
-    return temp;
-  }
+  return trailing_comments_.Release(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), GetArenaNoVirtual());
+}
+inline ::std::string* SourceCodeInfo_Location::unsafe_arena_release_trailing_comments() {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  clear_has_trailing_comments();
+  return trailing_comments_.UnsafeArenaRelease(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      GetArenaNoVirtual());
 }
 inline void SourceCodeInfo_Location::set_allocated_trailing_comments(::std::string* trailing_comments) {
-  if (trailing_comments_ != &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
-    delete trailing_comments_;
+  if (trailing_comments != NULL) {
+    set_has_trailing_comments();
+  } else {
+    clear_has_trailing_comments();
   }
-  if (trailing_comments) {
+  trailing_comments_.SetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(), trailing_comments,
+      GetArenaNoVirtual());
+  // @@protoc_insertion_point(field_set_allocated:google.protobuf.SourceCodeInfo.Location.trailing_comments)
+}
+inline void SourceCodeInfo_Location::unsafe_arena_set_allocated_trailing_comments(
+    ::std::string* trailing_comments) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() != NULL);
+  if (trailing_comments != NULL) {
     set_has_trailing_comments();
-    trailing_comments_ = trailing_comments;
   } else {
     clear_has_trailing_comments();
-    trailing_comments_ = const_cast< ::std::string*>(&::google::protobuf::internal::GetEmptyStringAlreadyInited());
   }
+  set_has_trailing_comments();
+  trailing_comments_.UnsafeArenaSetAllocated(&::google::protobuf::internal::GetEmptyStringAlreadyInited(),
+      trailing_comments, GetArenaNoVirtual());
   // @@protoc_insertion_point(field_set_allocated:google.protobuf.SourceCodeInfo.Location.trailing_comments)
 }
 
@@ -6752,8 +7732,8 @@ inline const EnumDescriptor* GetEnumDescriptor< ::google::protobuf::FieldOptions
   return ::google::protobuf::FieldOptions_CType_descriptor();
 }
 
-}  // namespace google
 }  // namespace protobuf
+}  // namespace google
 #endif  // SWIG
 
 // @@protoc_insertion_point(global_scope)
diff --git a/src/google/protobuf/descriptor.proto b/src/google/protobuf/descriptor.proto
index a753601f..f30f4df5 100644
--- a/src/google/protobuf/descriptor.proto
+++ b/src/google/protobuf/descriptor.proto
@@ -37,6 +37,7 @@
 // without any other information (e.g. without reading its imports).
 
 
+syntax = "proto2";
 
 package google.protobuf;
 option java_package = "com.google.protobuf";
@@ -74,10 +75,14 @@ message FileDescriptorProto {
   optional FileOptions options = 8;
 
   // This field contains optional information about the original source code.
-  // You may safely remove this entire field whithout harming runtime
+  // You may safely remove this entire field without harming runtime
   // functionality of the descriptors -- the information is needed only by
   // development tools.
   optional SourceCodeInfo source_code_info = 9;
+
+  // The syntax of the proto file.
+  // The supported values are "proto2" and "proto3".
+  optional string syntax = 12;
 }
 
 // Describes a message type.
@@ -306,7 +311,10 @@ message FileOptions {
   optional OptimizeMode optimize_for = 9 [default=SPEED];
 
   // Sets the Go package where structs generated from this .proto will be
-  // placed.  There is no default.
+  // placed. If omitted, the Go package will be derived from the following:
+  //   - The basename of the package import path, if provided.
+  //   - Otherwise, the package statement in the .proto file, if present.
+  //   - Otherwise, the basename of the .proto file, without extension.
   optional string go_package = 11;
 
 
@@ -315,7 +323,7 @@ message FileOptions {
   // are not specific to any particular RPC system.  They are generated by the
   // main code generators in each language (without additional plugins).
   // Generic services were the only kind of service generation supported by
-  // early versions of proto2.
+  // early versions of google.protobuf.
   //
   // Generic services are now considered deprecated in favor of using plugins
   // that generate code specific to your particular RPC system.  Therefore,
@@ -371,6 +379,29 @@ message MessageOptions {
   // this is a formalization for deprecating messages.
   optional bool deprecated = 3 [default=false];
 
+  // Whether the message is an automatically generated map entry type for the
+  // maps field.
+  //
+  // For maps fields:
+  //     map<KeyType, ValueType> map_field = 1;
+  // The parsed descriptor looks like:
+  //     message MapFieldEntry {
+  //         option map_entry = true;
+  //         optional KeyType key = 1;
+  //         optional ValueType value = 2;
+  //     }
+  //     repeated MapFieldEntry map_field = 1;
+  //
+  // Implementations may choose not to generate the map_entry=true message, but
+  // use a native map in the target language to hold the keys and values.
+  // The reflection APIs in such implementions still need to work as
+  // if the field is a repeated message field.
+  //
+  // NOTE: Do not set the option in .proto files. Always use the maps syntax
+  // instead. The option should only be implicitly set by the proto compiler
+  // parser.
+  optional bool map_entry = 7;
+
   // The parser stores options it doesn't recognize here. See above.
   repeated UninterpretedOption uninterpreted_option = 999;
 
@@ -436,20 +467,6 @@ message FieldOptions {
   // is a formalization for deprecating fields.
   optional bool deprecated = 3 [default=false];
 
-  // EXPERIMENTAL.  DO NOT USE.
-  // For "map" fields, the name of the field in the enclosed type that
-  // is the key for this map.  For example, suppose we have:
-  //   message Item {
-  //     required string name = 1;
-  //     required string value = 2;
-  //   }
-  //   message Config {
-  //     repeated Item items = 1 [experimental_map_key="name"];
-  //   }
-  // In this situation, the map key for Item will be set to "name".
-  // TODO: Fully-implement this, then remove the "experimental_" prefix.
-  optional string experimental_map_key = 9;
-
   // For Google-internal migration only. Do not use.
   optional bool weak = 10 [default=false];
 
diff --git a/src/google/protobuf/descriptor_pb2_test.py b/src/google/protobuf/descriptor_pb2_test.py
index 48a0d48a..c5a8d8a2 100644
--- a/src/google/protobuf/descriptor_pb2_test.py
+++ b/src/google/protobuf/descriptor_pb2_test.py
@@ -33,14 +33,14 @@
 # Verify that prebuild and checkedin version of descriptor_pb2.py is up to date.
 
 from google3.pyglib import resources
-import unittest
+from google.apputils import basetest
 
 _DESC = 'google3/net/proto2/proto/descriptor_pb2.'
 _OLD = _DESC + 'py-prebuilt'
 _NEW = _DESC + 'compiled'
 
 
-class PregeneratedFileChanged(unittest.TestCase):
+class PregeneratedFileChanged(basetest.TestCase):
 
   def testSameText(self):
     generated = resources.GetResource(_NEW)
@@ -51,4 +51,4 @@ class PregeneratedFileChanged(unittest.TestCase):
         'regnerate a new version of %s and add it to your CL' % _OLD)
 
 if __name__ == '__main__':
-  unittest.main()
+  basetest.main()
diff --git a/src/google/protobuf/descriptor_unittest.cc b/src/google/protobuf/descriptor_unittest.cc
index ac96160c..3e6de803 100644
--- a/src/google/protobuf/descriptor_unittest.cc
+++ b/src/google/protobuf/descriptor_unittest.cc
@@ -360,6 +360,34 @@ TEST_F(FileDescriptorTest, BuildAgain) {
   EXPECT_TRUE(pool_.BuildFile(file) == NULL);
 }
 
+TEST_F(FileDescriptorTest, Syntax) {
+  FileDescriptorProto proto;
+  proto.set_name("foo");
+  // Enable the test when we also populate the syntax for proto2.
+#if 0
+  {
+    proto.set_syntax("proto2");
+    DescriptorPool pool;
+    const FileDescriptor* file = pool.BuildFile(proto);
+    EXPECT_TRUE(file != NULL);
+    EXPECT_EQ(FileDescriptor::SYNTAX_PROTO2, file->syntax());
+    FileDescriptorProto other;
+    file->CopyTo(&other);
+    EXPECT_EQ("proto2", other.syntax());
+  }
+#endif
+  {
+    proto.set_syntax("proto3");
+    DescriptorPool pool;
+    const FileDescriptor* file = pool.BuildFile(proto);
+    EXPECT_TRUE(file != NULL);
+    EXPECT_EQ(FileDescriptor::SYNTAX_PROTO3, file->syntax());
+    FileDescriptorProto other;
+    file->CopyTo(&other);
+    EXPECT_EQ("proto3", other.syntax());
+  }
+}
+
 // ===================================================================
 
 // Test simple flat messages and fields.
@@ -2157,6 +2185,12 @@ TEST_P(AllowUnknownDependenciesTest, PlaceholderFile) {
   // Placeholder files should not be findable.
   EXPECT_EQ(bar_file_, pool_->FindFileByName(bar_file_->name()));
   EXPECT_TRUE(pool_->FindFileByName(baz_file->name()) == NULL);
+
+  // Copy*To should not crash for placeholder files.
+  FileDescriptorProto baz_file_proto;
+  baz_file->CopyTo(&baz_file_proto);
+  baz_file->CopySourceCodeInfoTo(&baz_file_proto);
+  EXPECT_FALSE(baz_file_proto.has_source_code_info());
 }
 
 TEST_P(AllowUnknownDependenciesTest, PlaceholderTypes) {
@@ -4736,6 +4770,553 @@ TEST_F(ValidationErrorTest, UnusedImportWarning) {
     "}");
 }
 
+namespace {
+void FillValidMapEntry(FileDescriptorProto* file_proto) {
+  ASSERT_TRUE(TextFormat::ParseFromString(
+      "name: 'foo.proto' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  field { "
+      "    name: 'foo_map' number: 1 label:LABEL_REPEATED "
+      "    type_name: 'FooMapEntry' "
+      "  } "
+      "  nested_type { "
+      "    name: 'FooMapEntry' "
+      "    options {  map_entry: true } "
+      "    field { "
+      "      name: 'key' number: 1 type:TYPE_INT32 label:LABEL_OPTIONAL "
+      "    } "
+      "    field { "
+      "      name: 'value' number: 2 type:TYPE_INT32 label:LABEL_OPTIONAL "
+      "    } "
+      "  } "
+      "} "
+      "message_type { "
+      "  name: 'Bar' "
+      "  extension_range { start: 1 end: 10 }"
+      "} ",
+      file_proto));
+}
+static const char* kMapEntryErrorMessage =
+    "foo.proto: Foo.foo_map: OTHER: map_entry should not be set explicitly. "
+    "Use map<KeyType, ValueType> instead.\n";
+static const char* kMapEntryKeyTypeErrorMessage =
+    "foo.proto: Foo.foo_map: TYPE: Key in map fields cannot be float/double, "
+    "bytes or message types.\n";
+
+}  // namespace
+
+TEST_F(ValidationErrorTest, MapEntryBase) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  BuildFile(file_proto.DebugString());
+}
+
+TEST_F(ValidationErrorTest, MapEntryExtensionRange) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "extension_range { "
+      "  start: 10 end: 20 "
+      "} ",
+      file_proto.mutable_message_type(0)->mutable_nested_type(0));
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryExtension) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "extension { "
+      "  name: 'foo_ext' extendee: '.Bar' number: 5"
+      "} ",
+      file_proto.mutable_message_type(0)->mutable_nested_type(0));
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryNestedType) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "nested_type { "
+      "  name: 'Bar' "
+      "} ",
+      file_proto.mutable_message_type(0)->mutable_nested_type(0));
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryEnumTypes) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "enum_type { "
+      "  name: 'BarEnum' "
+      "  value { name: 'BAR_BAR' number:0 } "
+      "} ",
+      file_proto.mutable_message_type(0)->mutable_nested_type(0));
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryExtraField) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "field { "
+      "  name: 'other_field' "
+      "  label: LABEL_OPTIONAL "
+      "  type: TYPE_INT32 "
+      "  number: 3 "
+      "} ",
+      file_proto.mutable_message_type(0)->mutable_nested_type(0));
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryMessageName) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  file_proto.mutable_message_type(0)->mutable_nested_type(0)->set_name(
+      "OtherMapEntry");
+  file_proto.mutable_message_type(0)->mutable_field(0)->set_type_name(
+      "OtherMapEntry");
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryNoneRepeatedMapEntry) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  file_proto.mutable_message_type(0)->mutable_field(0)->set_label(
+      FieldDescriptorProto::LABEL_OPTIONAL);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryDifferentContainingType) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  // Move the nested MapEntry message into the top level, which should not pass
+  // the validation.
+  file_proto.mutable_message_type()->AddAllocated(
+      file_proto.mutable_message_type(0)->mutable_nested_type()->ReleaseLast());
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryKeyName) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key = file_proto.mutable_message_type(0)
+      ->mutable_nested_type(0)
+      ->mutable_field(0);
+  key->set_name("Key");
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryKeyLabel) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key = file_proto.mutable_message_type(0)
+      ->mutable_nested_type(0)
+      ->mutable_field(0);
+  key->set_label(FieldDescriptorProto::LABEL_REQUIRED);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryKeyNumber) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key = file_proto.mutable_message_type(0)
+      ->mutable_nested_type(0)
+      ->mutable_field(0);
+  key->set_number(3);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryValueName) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* value = file_proto.mutable_message_type(0)
+      ->mutable_nested_type(0)
+      ->mutable_field(1);
+  value->set_name("Value");
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryValueLabel) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* value = file_proto.mutable_message_type(0)
+      ->mutable_nested_type(0)
+      ->mutable_field(1);
+  value->set_label(FieldDescriptorProto::LABEL_REQUIRED);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryValueNumber) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* value = file_proto.mutable_message_type(0)
+      ->mutable_nested_type(0)
+      ->mutable_field(1);
+  value->set_number(3);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryKeyTypeFloat) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key = file_proto.mutable_message_type(0)
+      ->mutable_nested_type(0)
+      ->mutable_field(0);
+  key->set_type(FieldDescriptorProto::TYPE_FLOAT);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryKeyTypeErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryKeyTypeDouble) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key = file_proto.mutable_message_type(0)
+      ->mutable_nested_type(0)
+      ->mutable_field(0);
+  key->set_type(FieldDescriptorProto::TYPE_DOUBLE);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryKeyTypeErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryKeyTypeBytes) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key = file_proto.mutable_message_type(0)
+      ->mutable_nested_type(0)
+      ->mutable_field(0);
+  key->set_type(FieldDescriptorProto::TYPE_BYTES);
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryKeyTypeErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryKeyTypeEnum) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key = file_proto.mutable_message_type(0)
+      ->mutable_nested_type(0)
+      ->mutable_field(0);
+  key->clear_type();
+  key->set_type_name("BarEnum");
+  EnumDescriptorProto* enum_proto = file_proto.add_enum_type();
+  enum_proto->set_name("BarEnum");
+  EnumValueDescriptorProto* enum_value_proto = enum_proto->add_value();
+  enum_value_proto->set_name("BAR_VALUE0");
+  enum_value_proto->set_number(0);
+  BuildFileWithErrors(file_proto.DebugString(),
+                      "foo.proto: Foo.foo_map: TYPE: Key in map fields cannot "
+                      "be enum types.\n");
+  // Enum keys are not allowed in proto3 as well.
+  // Get rid of extensions for proto3 to make it proto3 compatible.
+  file_proto.mutable_message_type()->RemoveLast();
+  file_proto.set_syntax("proto3");
+  BuildFileWithErrors(file_proto.DebugString(),
+                      "foo.proto: Foo.foo_map: TYPE: Key in map fields cannot "
+                      "be enum types.\n");
+}
+
+
+TEST_F(ValidationErrorTest, MapEntryKeyTypeMessage) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  FieldDescriptorProto* key = file_proto.mutable_message_type(0)
+      ->mutable_nested_type(0)
+      ->mutable_field(0);
+  key->clear_type();
+  key->set_type_name(".Bar");
+  BuildFileWithErrors(file_proto.DebugString(), kMapEntryKeyTypeErrorMessage);
+}
+
+TEST_F(ValidationErrorTest, MapEntryConflictsWithField) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "field { "
+      "  name: 'FooMapEntry' "
+      "  type: TYPE_INT32 "
+      "  label: LABEL_OPTIONAL "
+      "  number: 100 "
+      "}",
+      file_proto.mutable_message_type(0));
+  BuildFileWithErrors(
+      file_proto.DebugString(),
+      "foo.proto: Foo.FooMapEntry: NAME: \"FooMapEntry\" is already defined in "
+      "\"Foo\".\n"
+      "foo.proto: Foo.foo_map: TYPE: \"FooMapEntry\" is not defined.\n"
+      "foo.proto: Foo: NAME: Expanded map entry type FooMapEntry conflicts "
+      "with an existing field.\n");
+}
+
+TEST_F(ValidationErrorTest, MapEntryConflictsWithMessage) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "nested_type { "
+      "  name: 'FooMapEntry' "
+      "}",
+      file_proto.mutable_message_type(0));
+  BuildFileWithErrors(
+      file_proto.DebugString(),
+      "foo.proto: Foo.FooMapEntry: NAME: \"FooMapEntry\" is already defined in "
+      "\"Foo\".\n"
+      "foo.proto: Foo: NAME: Expanded map entry type FooMapEntry conflicts "
+      "with an existing nested message type.\n");
+}
+
+TEST_F(ValidationErrorTest, MapEntryConflictsWithEnum) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "enum_type { "
+      "  name: 'FooMapEntry' "
+      "  value { name: 'ENTRY_FOO' number: 0 }"
+      "}",
+      file_proto.mutable_message_type(0));
+  BuildFileWithErrors(
+      file_proto.DebugString(),
+      "foo.proto: Foo.FooMapEntry: NAME: \"FooMapEntry\" is already defined in "
+      "\"Foo\".\n"
+      "foo.proto: Foo: NAME: Expanded map entry type FooMapEntry conflicts "
+      "with an existing enum type.\n");
+}
+
+TEST_F(ValidationErrorTest, MapEntryConflictsWithOneof) {
+  FileDescriptorProto file_proto;
+  FillValidMapEntry(&file_proto);
+  TextFormat::MergeFromString(
+      "oneof_decl { "
+      "  name: 'FooMapEntry' "
+      "}"
+      "field { "
+      "  name: 'int_field' "
+      "  type: TYPE_INT32 "
+      "  label: LABEL_OPTIONAL "
+      "  oneof_index: 0 "
+      "  number: 100 "
+      "} ",
+      file_proto.mutable_message_type(0));
+  BuildFileWithErrors(
+      file_proto.DebugString(),
+      "foo.proto: Foo.FooMapEntry: NAME: \"FooMapEntry\" is already defined in "
+      "\"Foo\".\n"
+      "foo.proto: Foo.foo_map: TYPE: \"FooMapEntry\" is not defined.\n"
+      "foo.proto: Foo: NAME: Expanded map entry type FooMapEntry conflicts "
+      "with an existing oneof type.\n");
+}
+
+TEST_F(ValidationErrorTest, Proto3RequiredFields) {
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  field { name:'foo' number:1 label:LABEL_REQUIRED type:TYPE_INT32 } "
+      "}",
+      "foo.proto: Foo.foo: OTHER: Required fields are not allowed in "
+      "proto3.\n");
+
+  // applied to nested types as well.
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  nested_type { "
+      "    name : 'Bar' "
+      "    field { name:'bar' number:1 label:LABEL_REQUIRED type:TYPE_INT32 } "
+      "  } "
+      "}",
+      "foo.proto: Foo.Bar.bar: OTHER: Required fields are not allowed in "
+      "proto3.\n");
+
+  // optional and repeated fields are OK.
+  BuildFile(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  field { name:'foo' number:1 label:LABEL_OPTIONAL type:TYPE_INT32 } "
+      "  field { name:'bar' number:2 label:LABEL_REPEATED type:TYPE_INT32 } "
+      "}");
+}
+
+TEST_F(ValidationErrorTest, ValidateProto3DefaultValue) {
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  field { name:'foo' number:1 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "          default_value: '1' }"
+      "}",
+      "foo.proto: Foo.foo: OTHER: Explicit default values are not allowed in "
+      "proto3.\n");
+
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  nested_type { "
+      "    name : 'Bar' "
+      "    field { name:'bar' number:1 label:LABEL_OPTIONAL type:TYPE_INT32 "
+      "            default_value: '1' }"
+      "  } "
+      "}",
+      "foo.proto: Foo.Bar.bar: OTHER: Explicit default values are not allowed "
+      "in proto3.\n");
+}
+
+TEST_F(ValidationErrorTest, ValidateProto3ExtensionRange) {
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  field { name:'foo' number:1 label:LABEL_OPTIONAL type:TYPE_INT32 } "
+      "  extension_range { start:10 end:100 } "
+      "}",
+      "foo.proto: Foo: OTHER: Extension ranges are not allowed in "
+      "proto3.\n");
+
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  nested_type { "
+      "    name : 'Bar' "
+      "    field { name:'bar' number:1 label:LABEL_OPTIONAL type:TYPE_INT32 } "
+      "    extension_range { start:10 end:100 } "
+      "  } "
+      "}",
+      "foo.proto: Foo.Bar: OTHER: Extension ranges are not allowed in "
+      "proto3.\n");
+}
+
+TEST_F(ValidationErrorTest, ValidateProto3MessageSetWireFormat) {
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  options { message_set_wire_format: true } "
+      "}",
+      "foo.proto: Foo: OTHER: MessageSet is not supported "
+      "in proto3.\n");
+}
+
+TEST_F(ValidationErrorTest, ValidateProto3Enum) {
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "enum_type { "
+      "  name: 'FooEnum' "
+      "  value { name: 'FOO_FOO' number:1 } "
+      "}",
+      "foo.proto: FooEnum: OTHER: The first enum value must be "
+      "zero in proto3.\n");
+
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "  enum_type { "
+      "    name: 'FooEnum' "
+      "    value { name: 'FOO_FOO' number:1 } "
+      "  } "
+      "}",
+      "foo.proto: Foo.FooEnum: OTHER: The first enum value must be "
+      "zero in proto3.\n");
+
+  // valid case.
+  BuildFile(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "enum_type { "
+      "  name: 'FooEnum' "
+      "  value { name: 'FOO_FOO' number:0 } "
+      "}");
+}
+
+TEST_F(ValidationErrorTest, ValidateProto3LiteRuntime) {
+  // Lite runtime is not supported in proto3.
+  BuildFileWithErrors(
+      "name: 'foo.proto' "
+      "syntax: 'proto3' "
+      "options { "
+      "  optimize_for: LITE_RUNTIME "
+      "} ",
+      "foo.proto: foo.proto: OTHER: Lite runtime is not supported "
+      "in proto3.\n");
+}
+
+
+TEST_F(ValidationErrorTest, ValidateProto3EnumFromProto2) {
+  // Define an enum in a proto2 file.
+  BuildFile(
+      "name: 'foo.proto' "
+      "package: 'foo' "
+      "syntax: 'proto2' "
+      "enum_type { "
+      "  name: 'FooEnum' "
+      "  value { name: 'DEFAULT_OPTION' number:0 } "
+      "}");
+
+  // Now try to refer to it. (All tests in the fixture use the same pool, so we
+  // can refer to the enum above in this definition.)
+  BuildFileWithErrors(
+      "name: 'bar.proto' "
+      "dependency: 'foo.proto' "
+      "syntax: 'proto3' "
+      "message_type { "
+      "  name: 'Foo' "
+      "    field { name:'bar' number:1 label:LABEL_OPTIONAL type:TYPE_ENUM "
+      "            type_name: 'foo.FooEnum' }"
+      "}",
+      "bar.proto: Foo.bar: TYPE: Enum type \"foo.FooEnum\" is not a proto3 "
+      "enum, but is used in \"Foo\" which is a proto3 message type.\n");
+}
+
+TEST_F(ValidationErrorTest, ValidateProto3Extension) {
+  // Valid for options.
+  DescriptorPool pool;
+  FileDescriptorProto file_proto;
+  // Add "google/protobuf/descriptor.proto".
+  FileDescriptorProto::descriptor()->file()->CopyTo(&file_proto);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != NULL);
+  // Add "foo.proto":
+  //   import "google/protobuf/descriptor.proto";
+  //   extend google.protobuf.FieldOptions {
+  //     optional int32 option1 = 1000;
+  //   }
+  file_proto.Clear();
+  file_proto.set_name("foo.proto");
+  file_proto.set_syntax("proto3");
+  file_proto.add_dependency("google/protobuf/descriptor.proto");
+  AddExtension(&file_proto, "google.protobuf.FieldOptions", "option1", 1000,
+               FieldDescriptorProto::LABEL_OPTIONAL,
+               FieldDescriptorProto::TYPE_INT32);
+  ASSERT_TRUE(pool.BuildFile(file_proto) != NULL);
+
+  // Copy and change the package of the descriptor.proto
+  BuildFile(
+      "name: 'google.protobuf.proto' "
+      "syntax: 'proto2' "
+      "message_type { "
+      "  name: 'Container' extension_range { start: 1 end: 1000 } "
+      "}");
+  BuildFileWithErrors(
+      "name: 'bar.proto' "
+      "syntax: 'proto3' "
+      "dependency: 'google.protobuf.proto' "
+      "extension { "
+      "  name: 'bar' number: 1 label: LABEL_OPTIONAL type: TYPE_INT32 "
+      "  extendee: 'Container' "
+      "}",
+      "bar.proto: bar: OTHER: Extensions in proto3 are only allowed for "
+      "defining options.\n");
+}
 
 // ===================================================================
 // DescriptorDatabase
diff --git a/src/google/protobuf/drop_unknown_fields_test.cc b/src/google/protobuf/drop_unknown_fields_test.cc
new file mode 100644
index 00000000..2a672c7a
--- /dev/null
+++ b/src/google/protobuf/drop_unknown_fields_test.cc
@@ -0,0 +1,88 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+
+#include <google/protobuf/unittest_drop_unknown_fields.pb.h>
+#include <google/protobuf/dynamic_message.h>
+#include <gtest/gtest.h>
+
+namespace google {
+using unittest_drop_unknown_fields::Foo;
+using unittest_drop_unknown_fields::FooWithExtraFields;
+
+namespace protobuf {
+
+TEST(DropUnknownFieldsTest, GeneratedMessage) {
+  FooWithExtraFields foo_with_extra_fields;
+  foo_with_extra_fields.set_int32_value(1);
+  foo_with_extra_fields.set_enum_value(FooWithExtraFields::QUX);
+  foo_with_extra_fields.set_extra_int32_value(2);
+
+  Foo foo;
+  ASSERT_TRUE(foo.ParseFromString(foo_with_extra_fields.SerializeAsString()));
+  EXPECT_EQ(1, foo.int32_value());
+  EXPECT_EQ(static_cast<int>(FooWithExtraFields::QUX),
+            static_cast<int>(foo.enum_value()));
+  // We don't generate unknown field accessors but the UnknownFieldSet is
+  // still exposed through reflection API.
+  EXPECT_TRUE(foo.GetReflection()->GetUnknownFields(foo).empty());
+
+  ASSERT_TRUE(foo_with_extra_fields.ParseFromString(foo.SerializeAsString()));
+  EXPECT_EQ(1, foo_with_extra_fields.int32_value());
+  EXPECT_EQ(FooWithExtraFields::QUX, foo_with_extra_fields.enum_value());
+  // The "extra_int32_value" field should be lost.
+  EXPECT_EQ(0, foo_with_extra_fields.extra_int32_value());
+}
+
+TEST(DropUnknownFieldsTest, DynamicMessage) {
+  FooWithExtraFields foo_with_extra_fields;
+  foo_with_extra_fields.set_int32_value(1);
+  foo_with_extra_fields.set_enum_value(FooWithExtraFields::QUX);
+  foo_with_extra_fields.set_extra_int32_value(2);
+
+  google::protobuf::DynamicMessageFactory factory;
+  scoped_ptr<google::protobuf::Message> foo(
+      factory.GetPrototype(Foo::descriptor())->New());
+  ASSERT_TRUE(foo->ParseFromString(foo_with_extra_fields.SerializeAsString()));
+  EXPECT_TRUE(foo->GetReflection()->GetUnknownFields(*foo).empty());
+
+  ASSERT_TRUE(foo_with_extra_fields.ParseFromString(foo->SerializeAsString()));
+  EXPECT_EQ(1, foo_with_extra_fields.int32_value());
+  EXPECT_EQ(FooWithExtraFields::QUX, foo_with_extra_fields.enum_value());
+  // The "extra_int32_value" field should be lost.
+  EXPECT_EQ(0, foo_with_extra_fields.extra_int32_value());
+}
+
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/dynamic_message.cc b/src/google/protobuf/dynamic_message.cc
index 4cca9869..db1dd4d3 100644
--- a/src/google/protobuf/dynamic_message.cc
+++ b/src/google/protobuf/dynamic_message.cc
@@ -72,6 +72,7 @@
 #include <google/protobuf/descriptor.pb.h>
 #include <google/protobuf/generated_message_util.h>
 #include <google/protobuf/generated_message_reflection.h>
+#include <google/protobuf/arenastring.h>
 #include <google/protobuf/reflection_ops.h>
 #include <google/protobuf/repeated_field.h>
 #include <google/protobuf/extension_set.h>
@@ -85,6 +86,8 @@ using internal::ExtensionSet;
 using internal::GeneratedMessageReflection;
 
 
+using internal::ArenaStringPtr;
+
 // ===================================================================
 // Some helper tables and functions...
 
@@ -131,7 +134,7 @@ int FieldSpaceUsed(const FieldDescriptor* field) {
         switch (field->options().ctype()) {
           default:  // TODO(kenton):  Support other string reps.
           case FieldOptions::STRING:
-            return sizeof(string*);
+            return sizeof(ArenaStringPtr);
         }
         break;
     }
@@ -162,7 +165,7 @@ int OneofFieldSpaceUsed(const FieldDescriptor* field) {
       switch (field->options().ctype()) {
         default:
         case FieldOptions::STRING:
-          return sizeof(string*);
+          return sizeof(ArenaStringPtr);
       }
       break;
   }
@@ -236,6 +239,8 @@ class DynamicMessage : public Message {
   // implements Message ----------------------------------------------
 
   Message* New() const;
+  Message* New(::google::protobuf::Arena* arena) const;
+  ::google::protobuf::Arena* GetArena() const { return NULL; };
 
   int GetCachedSize() const;
   void SetCachedSize(int size) const;
@@ -245,6 +250,8 @@ class DynamicMessage : public Message {
 
  private:
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(DynamicMessage);
+  DynamicMessage(const TypeInfo* type_info, ::google::protobuf::Arena* arena);
+  void SharedCtor();
 
   inline bool is_prototype() const {
     return type_info_->prototype == this ||
@@ -261,7 +268,6 @@ class DynamicMessage : public Message {
   }
 
   const TypeInfo* type_info_;
-
   // TODO(kenton):  Make this an atomic<int> when C++ supports it.
   mutable int cached_byte_size_;
 };
@@ -269,6 +275,17 @@ class DynamicMessage : public Message {
 DynamicMessage::DynamicMessage(const TypeInfo* type_info)
   : type_info_(type_info),
     cached_byte_size_(0) {
+  SharedCtor();
+}
+
+DynamicMessage::DynamicMessage(const TypeInfo* type_info,
+                               ::google::protobuf::Arena* arena)
+  : type_info_(type_info),
+    cached_byte_size_(0) {
+  SharedCtor();
+}
+
+void DynamicMessage::SharedCtor() {
   // We need to call constructors for various fields manually and set
   // default values where appropriate.  We use placement new to call
   // constructors.  If you haven't heard of placement new, I suggest Googling
@@ -330,15 +347,17 @@ DynamicMessage::DynamicMessage(const TypeInfo* type_info)
           default:  // TODO(kenton):  Support other string reps.
           case FieldOptions::STRING:
             if (!field->is_repeated()) {
+              const string* default_value;
               if (is_prototype()) {
-                new(field_ptr) const string*(&field->default_value_string());
+                default_value = &field->default_value_string();
               } else {
-                string* default_value =
-                  *reinterpret_cast<string* const*>(
+                default_value =
+                  &(reinterpret_cast<const ArenaStringPtr*>(
                     type_info_->prototype->OffsetToPointer(
-                      type_info_->offsets[i]));
-                new(field_ptr) string*(default_value);
+                      type_info_->offsets[i]))->Get(NULL));
               }
+              ArenaStringPtr* asp = new(field_ptr) ArenaStringPtr();
+              asp->UnsafeSetDefault(default_value);
             } else {
               new(field_ptr) RepeatedPtrField<string>();
             }
@@ -390,9 +409,15 @@ DynamicMessage::~DynamicMessage() {
         if (field->cpp_type() == FieldDescriptor::CPPTYPE_STRING) {
           switch (field->options().ctype()) {
             default:
-            case FieldOptions::STRING:
-              delete *reinterpret_cast<string**>(field_ptr);
+            case FieldOptions::STRING: {
+              const ::std::string* default_value =
+                  &(reinterpret_cast<const ArenaStringPtr*>(
+                      type_info_->prototype->OffsetToPointer(
+                          type_info_->offsets[i]))->Get(NULL));
+              reinterpret_cast<ArenaStringPtr*>(field_ptr)->Destroy(default_value,
+                                                                    NULL);
               break;
+            }
           }
         } else if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
             delete *reinterpret_cast<Message**>(field_ptr);
@@ -440,10 +465,12 @@ DynamicMessage::~DynamicMessage() {
       switch (field->options().ctype()) {
         default:  // TODO(kenton):  Support other string reps.
         case FieldOptions::STRING: {
-          string* ptr = *reinterpret_cast<string**>(field_ptr);
-          if (ptr != &field->default_value_string()) {
-            delete ptr;
-          }
+          const ::std::string* default_value =
+              &(reinterpret_cast<const ArenaStringPtr*>(
+                  type_info_->prototype->OffsetToPointer(
+                      type_info_->offsets[i]))->Get(NULL));
+          reinterpret_cast<ArenaStringPtr*>(field_ptr)->Destroy(default_value,
+                                                                NULL);
           break;
         }
       }
@@ -492,6 +519,16 @@ Message* DynamicMessage::New() const {
   return new(new_base) DynamicMessage(type_info_);
 }
 
+Message* DynamicMessage::New(::google::protobuf::Arena* arena) const {
+  if (arena != NULL) {
+    Message* message = New();
+    arena->Own(message);
+    return message;
+  } else {
+    return New();
+  }
+}
+
 int DynamicMessage::GetCachedSize() const {
   return cached_byte_size_;
 }
@@ -672,7 +709,8 @@ const Message* DynamicMessageFactory::GetPrototypeNoLock(
             type_info->oneof_case_offset,
             type_info->pool,
             this,
-            type_info->size));
+            type_info->size,
+            -1 /* arena_offset */));
   } else {
     type_info->reflection.reset(
         new GeneratedMessageReflection(
@@ -684,7 +722,8 @@ const Message* DynamicMessageFactory::GetPrototypeNoLock(
             type_info->extensions_offset,
             type_info->pool,
             this,
-            type_info->size));
+            type_info->size,
+            -1 /* arena_offset */));
   }
   // Cross link prototypes.
   prototype->CrossLinkPrototypes();
@@ -723,12 +762,8 @@ void DynamicMessageFactory::ConstructDefaultOneofInstance(
           switch (field->options().ctype()) {
             default:
             case FieldOptions::STRING:
-              if (field->has_default_value()) {
-                new(field_ptr) const string*(&field->default_value_string());
-              } else {
-                new(field_ptr) string*(
-                    const_cast<string*>(&internal::GetEmptyString()));
-              }
+              ArenaStringPtr* asp = new (field_ptr) ArenaStringPtr();
+              asp->UnsafeSetDefault(&field->default_value_string());
               break;
           }
           break;
diff --git a/src/google/protobuf/dynamic_message.h b/src/google/protobuf/dynamic_message.h
index 10ed7005..1e947e6d 100644
--- a/src/google/protobuf/dynamic_message.h
+++ b/src/google/protobuf/dynamic_message.h
@@ -39,6 +39,9 @@
 #define GOOGLE_PROTOBUF_DYNAMIC_MESSAGE_H__
 
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 
 #include <google/protobuf/message.h>
 #include <google/protobuf/stubs/common.h>
diff --git a/src/google/protobuf/dynamic_message_unittest.cc b/src/google/protobuf/dynamic_message_unittest.cc
index a1c1661b..6353ecbf 100644
--- a/src/google/protobuf/dynamic_message_unittest.cc
+++ b/src/google/protobuf/dynamic_message_unittest.cc
@@ -226,5 +226,13 @@ TEST_F(DynamicMessageTest, SpaceUsed) {
   EXPECT_LT(initial_space_used, message->SpaceUsed());
 }
 
+TEST_F(DynamicMessageTest, Arena) {
+  Arena arena;
+  Message* message = prototype_->New(&arena);
+  (void)message;  // avoid unused-variable error.
+  // Return without freeing: should not leak.
+}
+
+
 }  // namespace protobuf
 }  // namespace google
diff --git a/src/google/protobuf/extension_set.cc b/src/google/protobuf/extension_set.cc
index 274554b5..d6ebe4c3 100644
--- a/src/google/protobuf/extension_set.cc
+++ b/src/google/protobuf/extension_set.cc
@@ -174,12 +174,21 @@ void ExtensionSet::RegisterMessageExtension(const MessageLite* containing_type,
 // ===================================================================
 // Constructors and basic methods.
 
-ExtensionSet::ExtensionSet() {}
+ExtensionSet::ExtensionSet(::google::protobuf::Arena* arena) : arena_(arena) {
+  if (arena_ != NULL) {
+    arena_->OwnDestructor(&extensions_);
+  }
+}
+
+ExtensionSet::ExtensionSet() : arena_(NULL) {}
 
 ExtensionSet::~ExtensionSet() {
-  for (map<int, Extension>::iterator iter = extensions_.begin();
-       iter != extensions_.end(); ++iter) {
-    iter->second.Free();
+  // Deletes all allocated extensions.
+  if (arena_ == NULL) {
+    for (map<int, Extension>::iterator iter = extensions_.begin();
+         iter != extensions_.end(); ++iter) {
+      iter->second.Free();
+    }
   }
 }
 
@@ -301,7 +310,8 @@ void ExtensionSet::Add##CAMELCASE(int number, FieldType type,                  \
     GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_##UPPERCASE); \
     extension->is_repeated = true;                                             \
     extension->is_packed = packed;                                             \
-    extension->repeated_##LOWERCASE##_value = new RepeatedField<LOWERCASE>();  \
+    extension->repeated_##LOWERCASE##_value =                                  \
+      Arena::Create<RepeatedField<LOWERCASE> >(arena_, arena_);                \
   } else {                                                                     \
     GOOGLE_DCHECK_TYPE(*extension, REPEATED, UPPERCASE);                              \
     GOOGLE_DCHECK_EQ(extension->is_packed, packed);                                   \
@@ -345,34 +355,44 @@ void* ExtensionSet::MutableRawRepeatedField(int number, FieldType field_type,
     switch (WireFormatLite::FieldTypeToCppType(
         static_cast<WireFormatLite::FieldType>(field_type))) {
       case WireFormatLite::CPPTYPE_INT32:
-        extension->repeated_int32_value = new RepeatedField<int32>();
+        extension->repeated_int32_value =
+            Arena::Create<RepeatedField<int32> >(arena_, arena_);
         break;
       case WireFormatLite::CPPTYPE_INT64:
-        extension->repeated_int64_value = new RepeatedField<int64>();
+        extension->repeated_int64_value =
+            Arena::Create<RepeatedField<int64> >(arena_, arena_);
         break;
       case WireFormatLite::CPPTYPE_UINT32:
-        extension->repeated_uint32_value = new RepeatedField<uint32>();
+        extension->repeated_uint32_value =
+            Arena::Create<RepeatedField<uint32> >(arena_, arena_);
         break;
       case WireFormatLite::CPPTYPE_UINT64:
-        extension->repeated_uint64_value = new RepeatedField<uint64>();
+        extension->repeated_uint64_value =
+            Arena::Create<RepeatedField<uint64> >(arena_, arena_);
         break;
       case WireFormatLite::CPPTYPE_DOUBLE:
-        extension->repeated_double_value = new RepeatedField<double>();
+        extension->repeated_double_value =
+            Arena::Create<RepeatedField<double> >(arena_, arena_);
         break;
       case WireFormatLite::CPPTYPE_FLOAT:
-        extension->repeated_float_value = new RepeatedField<float>();
+        extension->repeated_float_value =
+            Arena::Create<RepeatedField<float> >(arena_, arena_);
         break;
       case WireFormatLite::CPPTYPE_BOOL:
-        extension->repeated_bool_value = new RepeatedField<bool>();
+        extension->repeated_bool_value =
+            Arena::Create<RepeatedField<bool> >(arena_, arena_);
         break;
       case WireFormatLite::CPPTYPE_ENUM:
-        extension->repeated_enum_value = new RepeatedField<int>();
+        extension->repeated_enum_value =
+            Arena::Create<RepeatedField<int> >(arena_, arena_);
         break;
       case WireFormatLite::CPPTYPE_STRING:
-        extension->repeated_string_value = new RepeatedPtrField< ::std::string>();
+        extension->repeated_string_value =
+            Arena::Create<RepeatedPtrField< ::std::string> >(arena_, arena_);
         break;
       case WireFormatLite::CPPTYPE_MESSAGE:
-        extension->repeated_message_value = new RepeatedPtrField<MessageLite>();
+        extension->repeated_message_value =
+            Arena::Create<RepeatedPtrField<MessageLite> >(arena_, arena_);
         break;
     }
   }
@@ -444,7 +464,8 @@ void ExtensionSet::AddEnum(int number, FieldType type,
     GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_ENUM);
     extension->is_repeated = true;
     extension->is_packed = packed;
-    extension->repeated_enum_value = new RepeatedField<int>();
+    extension->repeated_enum_value =
+        Arena::Create<RepeatedField<int> >(arena_, arena_);
   } else {
     GOOGLE_DCHECK_TYPE(*extension, REPEATED, ENUM);
     GOOGLE_DCHECK_EQ(extension->is_packed, packed);
@@ -474,7 +495,7 @@ string* ExtensionSet::MutableString(int number, FieldType type,
     extension->type = type;
     GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_STRING);
     extension->is_repeated = false;
-    extension->string_value = new string;
+    extension->string_value = Arena::Create<string>(arena_);
   } else {
     GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, STRING);
   }
@@ -504,7 +525,8 @@ string* ExtensionSet::AddString(int number, FieldType type,
     GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_STRING);
     extension->is_repeated = true;
     extension->is_packed = false;
-    extension->repeated_string_value = new RepeatedPtrField<string>();
+    extension->repeated_string_value =
+        Arena::Create<RepeatedPtrField<string> >(arena_, arena_);
   } else {
     GOOGLE_DCHECK_TYPE(*extension, REPEATED, STRING);
   }
@@ -544,7 +566,7 @@ MessageLite* ExtensionSet::MutableMessage(int number, FieldType type,
     GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_MESSAGE);
     extension->is_repeated = false;
     extension->is_lazy = false;
-    extension->message_value = prototype.New();
+    extension->message_value = prototype.New(arena_);
     extension->is_cleared = false;
     return extension->message_value;
   } else {
@@ -576,14 +598,32 @@ void ExtensionSet::SetAllocatedMessage(int number, FieldType type,
     GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_MESSAGE);
     extension->is_repeated = false;
     extension->is_lazy = false;
-    extension->message_value = message;
+    if (message->GetArena() == arena_) {
+      extension->message_value = message;
+    } else {
+      extension->message_value = message->New(arena_);
+      extension->message_value->CheckTypeAndMergeFrom(*message);
+      if (message->GetArena() == NULL) {
+        delete message;
+      }
+    }
   } else {
     GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, MESSAGE);
     if (extension->is_lazy) {
       extension->lazymessage_value->SetAllocatedMessage(message);
     } else {
-      delete extension->message_value;
-      extension->message_value = message;
+      if (arena_ == NULL) {
+        delete extension->message_value;
+      }
+      if (message->GetArena() == arena_) {
+        extension->message_value = message;
+      } else {
+        extension->message_value = message->New(arena_);
+        extension->message_value->CheckTypeAndMergeFrom(*message);
+        if (message->GetArena() == NULL) {
+          delete message;
+        }
+      }
     }
   }
   extension->is_cleared = false;
@@ -600,7 +640,39 @@ MessageLite* ExtensionSet::ReleaseMessage(int number,
     MessageLite* ret = NULL;
     if (iter->second.is_lazy) {
       ret = iter->second.lazymessage_value->ReleaseMessage(prototype);
-      delete iter->second.lazymessage_value;
+      if (arena_ == NULL) {
+        delete iter->second.lazymessage_value;
+      }
+    } else {
+      if (arena_ == NULL) {
+        ret = iter->second.message_value;
+      } else {
+        // ReleaseMessage() always returns a heap-allocated message, and we are
+        // on an arena, so we need to make a copy of this message to return.
+        ret = (iter->second.message_value)->New();
+        ret->CheckTypeAndMergeFrom(*iter->second.message_value);
+      }
+    }
+    extensions_.erase(number);
+    return ret;
+  }
+}
+
+MessageLite* ExtensionSet::UnsafeArenaReleaseMessage(
+    int number, const MessageLite& prototype) {
+  map<int, Extension>::iterator iter = extensions_.find(number);
+  if (iter == extensions_.end()) {
+    // Not present.  Return NULL.
+    return NULL;
+  } else {
+    GOOGLE_DCHECK_TYPE(iter->second, OPTIONAL, MESSAGE);
+    MessageLite* ret = NULL;
+    if (iter->second.is_lazy) {
+      ret =
+        iter->second.lazymessage_value->UnsafeArenaReleaseMessage(prototype);
+      if (arena_ == NULL) {
+        delete iter->second.lazymessage_value;
+      }
     } else {
       ret = iter->second.message_value;
     }
@@ -637,7 +709,7 @@ MessageLite* ExtensionSet::AddMessage(int number, FieldType type,
     GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_MESSAGE);
     extension->is_repeated = true;
     extension->repeated_message_value =
-      new RepeatedPtrField<MessageLite>();
+        Arena::Create<RepeatedPtrField<MessageLite> >(arena_, arena_);
   } else {
     GOOGLE_DCHECK_TYPE(*extension, REPEATED, MESSAGE);
   }
@@ -647,7 +719,7 @@ MessageLite* ExtensionSet::AddMessage(int number, FieldType type,
   MessageLite* result = extension->repeated_message_value
       ->AddFromCleared<GenericTypeHandler<MessageLite> >();
   if (result == NULL) {
-    result = prototype.New();
+    result = prototype.New(arena_);
     extension->repeated_message_value->AddAllocated(result);
   }
   return result;
@@ -765,138 +837,142 @@ void ExtensionSet::MergeFrom(const ExtensionSet& other) {
   for (map<int, Extension>::const_iterator iter = other.extensions_.begin();
        iter != other.extensions_.end(); ++iter) {
     const Extension& other_extension = iter->second;
+    InternalExtensionMergeFrom(iter->first, other_extension);
+  }
+}
 
-    if (other_extension.is_repeated) {
-      Extension* extension;
-      bool is_new = MaybeNewExtension(iter->first, other_extension.descriptor,
-                                      &extension);
-      if (is_new) {
-        // Extension did not already exist in set.
-        extension->type = other_extension.type;
-        extension->is_packed = other_extension.is_packed;
-        extension->is_repeated = true;
-      } else {
-        GOOGLE_DCHECK_EQ(extension->type, other_extension.type);
-        GOOGLE_DCHECK_EQ(extension->is_packed, other_extension.is_packed);
-        GOOGLE_DCHECK(extension->is_repeated);
-      }
+void ExtensionSet::InternalExtensionMergeFrom(
+  int number, const Extension& other_extension) {
+  if (other_extension.is_repeated) {
+    Extension* extension;
+    bool is_new = MaybeNewExtension(number, other_extension.descriptor,
+                                    &extension);
+    if (is_new) {
+      // Extension did not already exist in set.
+      extension->type = other_extension.type;
+      extension->is_packed = other_extension.is_packed;
+      extension->is_repeated = true;
+    } else {
+      GOOGLE_DCHECK_EQ(extension->type, other_extension.type);
+      GOOGLE_DCHECK_EQ(extension->is_packed, other_extension.is_packed);
+      GOOGLE_DCHECK(extension->is_repeated);
+    }
 
-      switch (cpp_type(other_extension.type)) {
-#define HANDLE_TYPE(UPPERCASE, LOWERCASE, REPEATED_TYPE)             \
-        case WireFormatLite::CPPTYPE_##UPPERCASE:                    \
-          if (is_new) {                                              \
-            extension->repeated_##LOWERCASE##_value =                \
-              new REPEATED_TYPE;                                     \
-          }                                                          \
-          extension->repeated_##LOWERCASE##_value->MergeFrom(        \
-            *other_extension.repeated_##LOWERCASE##_value);          \
-          break;
+    switch (cpp_type(other_extension.type)) {
+#define HANDLE_TYPE(UPPERCASE, LOWERCASE, REPEATED_TYPE)                    \
+      case WireFormatLite::CPPTYPE_##UPPERCASE:                             \
+        if (is_new) {                                                       \
+          extension->repeated_##LOWERCASE##_value =                         \
+            Arena::Create<REPEATED_TYPE >(arena_, arena_);                  \
+        }                                                                   \
+        extension->repeated_##LOWERCASE##_value->MergeFrom(                 \
+          *other_extension.repeated_##LOWERCASE##_value);                   \
+        break;
 
-        HANDLE_TYPE(  INT32,   int32, RepeatedField   <  int32>);
-        HANDLE_TYPE(  INT64,   int64, RepeatedField   <  int64>);
-        HANDLE_TYPE( UINT32,  uint32, RepeatedField   < uint32>);
-        HANDLE_TYPE( UINT64,  uint64, RepeatedField   < uint64>);
-        HANDLE_TYPE(  FLOAT,   float, RepeatedField   <  float>);
-        HANDLE_TYPE( DOUBLE,  double, RepeatedField   < double>);
-        HANDLE_TYPE(   BOOL,    bool, RepeatedField   <   bool>);
-        HANDLE_TYPE(   ENUM,    enum, RepeatedField   <    int>);
-        HANDLE_TYPE( STRING,  string, RepeatedPtrField< string>);
+      HANDLE_TYPE(  INT32,   int32, RepeatedField   <  int32>);
+      HANDLE_TYPE(  INT64,   int64, RepeatedField   <  int64>);
+      HANDLE_TYPE( UINT32,  uint32, RepeatedField   < uint32>);
+      HANDLE_TYPE( UINT64,  uint64, RepeatedField   < uint64>);
+      HANDLE_TYPE(  FLOAT,   float, RepeatedField   <  float>);
+      HANDLE_TYPE( DOUBLE,  double, RepeatedField   < double>);
+      HANDLE_TYPE(   BOOL,    bool, RepeatedField   <   bool>);
+      HANDLE_TYPE(   ENUM,    enum, RepeatedField   <    int>);
+      HANDLE_TYPE( STRING,  string, RepeatedPtrField< string>);
 #undef HANDLE_TYPE
 
-        case WireFormatLite::CPPTYPE_MESSAGE:
-          if (is_new) {
-            extension->repeated_message_value =
-              new RepeatedPtrField<MessageLite>();
-          }
-          // We can't call RepeatedPtrField<MessageLite>::MergeFrom() because
-          // it would attempt to allocate new objects.
-          RepeatedPtrField<MessageLite>* other_repeated_message =
-              other_extension.repeated_message_value;
-          for (int i = 0; i < other_repeated_message->size(); i++) {
-            const MessageLite& other_message = other_repeated_message->Get(i);
-            MessageLite* target = extension->repeated_message_value
-                     ->AddFromCleared<GenericTypeHandler<MessageLite> >();
-            if (target == NULL) {
-              target = other_message.New();
-              extension->repeated_message_value->AddAllocated(target);
-            }
-            target->CheckTypeAndMergeFrom(other_message);
+      case WireFormatLite::CPPTYPE_MESSAGE:
+        if (is_new) {
+          extension->repeated_message_value =
+              Arena::Create<RepeatedPtrField<MessageLite> >(arena_, arena_);
+        }
+        // We can't call RepeatedPtrField<MessageLite>::MergeFrom() because
+        // it would attempt to allocate new objects.
+        RepeatedPtrField<MessageLite>* other_repeated_message =
+            other_extension.repeated_message_value;
+        for (int i = 0; i < other_repeated_message->size(); i++) {
+          const MessageLite& other_message = other_repeated_message->Get(i);
+          MessageLite* target = extension->repeated_message_value
+                   ->AddFromCleared<GenericTypeHandler<MessageLite> >();
+          if (target == NULL) {
+            target = other_message.New(arena_);
+            extension->repeated_message_value->AddAllocated(target);
           }
+          target->CheckTypeAndMergeFrom(other_message);
+        }
+        break;
+    }
+  } else {
+    if (!other_extension.is_cleared) {
+      switch (cpp_type(other_extension.type)) {
+#define HANDLE_TYPE(UPPERCASE, LOWERCASE, CAMELCASE)                       \
+        case WireFormatLite::CPPTYPE_##UPPERCASE:                          \
+          Set##CAMELCASE(number, other_extension.type,                     \
+                         other_extension.LOWERCASE##_value,                \
+                         other_extension.descriptor);                      \
           break;
-      }
-    } else {
-      if (!other_extension.is_cleared) {
-        switch (cpp_type(other_extension.type)) {
-#define HANDLE_TYPE(UPPERCASE, LOWERCASE, CAMELCASE)                         \
-          case WireFormatLite::CPPTYPE_##UPPERCASE:                          \
-            Set##CAMELCASE(iter->first, other_extension.type,                \
-                           other_extension.LOWERCASE##_value,                \
-                           other_extension.descriptor);                      \
-            break;
-
-          HANDLE_TYPE( INT32,  int32,  Int32);
-          HANDLE_TYPE( INT64,  int64,  Int64);
-          HANDLE_TYPE(UINT32, uint32, UInt32);
-          HANDLE_TYPE(UINT64, uint64, UInt64);
-          HANDLE_TYPE( FLOAT,  float,  Float);
-          HANDLE_TYPE(DOUBLE, double, Double);
-          HANDLE_TYPE(  BOOL,   bool,   Bool);
-          HANDLE_TYPE(  ENUM,   enum,   Enum);
+
+        HANDLE_TYPE( INT32,  int32,  Int32);
+        HANDLE_TYPE( INT64,  int64,  Int64);
+        HANDLE_TYPE(UINT32, uint32, UInt32);
+        HANDLE_TYPE(UINT64, uint64, UInt64);
+        HANDLE_TYPE( FLOAT,  float,  Float);
+        HANDLE_TYPE(DOUBLE, double, Double);
+        HANDLE_TYPE(  BOOL,   bool,   Bool);
+        HANDLE_TYPE(  ENUM,   enum,   Enum);
 #undef HANDLE_TYPE
-          case WireFormatLite::CPPTYPE_STRING:
-            SetString(iter->first, other_extension.type,
-                      *other_extension.string_value,
-                      other_extension.descriptor);
-            break;
-          case WireFormatLite::CPPTYPE_MESSAGE: {
-            Extension* extension;
-            bool is_new = MaybeNewExtension(iter->first,
-                                            other_extension.descriptor,
-                                            &extension);
-            if (is_new) {
-              extension->type = other_extension.type;
-              extension->is_packed = other_extension.is_packed;
-              extension->is_repeated = false;
-              if (other_extension.is_lazy) {
-                extension->is_lazy = true;
-                extension->lazymessage_value =
-                    other_extension.lazymessage_value->New();
+        case WireFormatLite::CPPTYPE_STRING:
+          SetString(number, other_extension.type,
+                    *other_extension.string_value,
+                    other_extension.descriptor);
+          break;
+        case WireFormatLite::CPPTYPE_MESSAGE: {
+          Extension* extension;
+          bool is_new = MaybeNewExtension(number,
+                                          other_extension.descriptor,
+                                          &extension);
+          if (is_new) {
+            extension->type = other_extension.type;
+            extension->is_packed = other_extension.is_packed;
+            extension->is_repeated = false;
+            if (other_extension.is_lazy) {
+              extension->is_lazy = true;
+              extension->lazymessage_value =
+                  other_extension.lazymessage_value->New(arena_);
+              extension->lazymessage_value->MergeFrom(
+                  *other_extension.lazymessage_value);
+            } else {
+              extension->is_lazy = false;
+              extension->message_value =
+                  other_extension.message_value->New(arena_);
+              extension->message_value->CheckTypeAndMergeFrom(
+                  *other_extension.message_value);
+            }
+          } else {
+            GOOGLE_DCHECK_EQ(extension->type, other_extension.type);
+            GOOGLE_DCHECK_EQ(extension->is_packed,other_extension.is_packed);
+            GOOGLE_DCHECK(!extension->is_repeated);
+            if (other_extension.is_lazy) {
+              if (extension->is_lazy) {
                 extension->lazymessage_value->MergeFrom(
                     *other_extension.lazymessage_value);
               } else {
-                extension->is_lazy = false;
-                extension->message_value =
-                    other_extension.message_value->New();
                 extension->message_value->CheckTypeAndMergeFrom(
-                    *other_extension.message_value);
+                    other_extension.lazymessage_value->GetMessage(
+                        *extension->message_value));
               }
             } else {
-              GOOGLE_DCHECK_EQ(extension->type, other_extension.type);
-              GOOGLE_DCHECK_EQ(extension->is_packed,other_extension.is_packed);
-              GOOGLE_DCHECK(!extension->is_repeated);
-              if (other_extension.is_lazy) {
-                if (extension->is_lazy) {
-                  extension->lazymessage_value->MergeFrom(
-                      *other_extension.lazymessage_value);
-                } else {
-                  extension->message_value->CheckTypeAndMergeFrom(
-                      other_extension.lazymessage_value->GetMessage(
-                          *extension->message_value));
-                }
+              if (extension->is_lazy) {
+                extension->lazymessage_value->MutableMessage(
+                    *other_extension.message_value)->CheckTypeAndMergeFrom(
+                        *other_extension.message_value);
               } else {
-                if (extension->is_lazy) {
-                  extension->lazymessage_value->MutableMessage(
-                      *other_extension.message_value)->CheckTypeAndMergeFrom(
-                          *other_extension.message_value);
-                } else {
-                  extension->message_value->CheckTypeAndMergeFrom(
-                      *other_extension.message_value);
-                }
+                extension->message_value->CheckTypeAndMergeFrom(
+                    *other_extension.message_value);
               }
             }
-            extension->is_cleared = false;
-            break;
           }
+          extension->is_cleared = false;
+          break;
         }
       }
     }
@@ -904,7 +980,19 @@ void ExtensionSet::MergeFrom(const ExtensionSet& other) {
 }
 
 void ExtensionSet::Swap(ExtensionSet* x) {
-  extensions_.swap(x->extensions_);
+  if (GetArenaNoVirtual() == x->GetArenaNoVirtual()) {
+    extensions_.swap(x->extensions_);
+  } else {
+    // TODO(cfallin, rohananil): We maybe able to optimize a case where we are
+    // swapping from heap to arena-allocated extension set, by just Own()'ing
+    // the extensions.
+    ExtensionSet extension_set;
+    extension_set.MergeFrom(*x);
+    x->Clear();
+    x->MergeFrom(*this);
+    Clear();
+    MergeFrom(extension_set);
+  }
 }
 
 void ExtensionSet::SwapExtension(ExtensionSet* other,
@@ -920,18 +1008,42 @@ void ExtensionSet::SwapExtension(ExtensionSet* other,
 
   if (this_iter != extensions_.end() &&
       other_iter != other->extensions_.end()) {
-    std::swap(this_iter->second, other_iter->second);
+    if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+      using std::swap;
+      swap(this_iter->second, other_iter->second);
+    } else {
+      // TODO(cfallin, rohananil): We could further optimize these cases,
+      // especially avoid creation of ExtensionSet, and move MergeFrom logic
+      // into Extensions itself (which takes arena as an argument).
+      // We do it this way to reuse the copy-across-arenas logic already
+      // implemented in ExtensionSet's MergeFrom.
+      ExtensionSet temp;
+      temp.InternalExtensionMergeFrom(number, other_iter->second);
+      map<int, Extension>::iterator temp_iter = temp.extensions_.find(number);
+      other_iter->second.Clear();
+      other->InternalExtensionMergeFrom(number, this_iter->second);
+      this_iter->second.Clear();
+      InternalExtensionMergeFrom(number, temp_iter->second);
+    }
     return;
   }
 
   if (this_iter == extensions_.end()) {
-    extensions_.insert(make_pair(number, other_iter->second));
+    if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+      extensions_.insert(make_pair(number, other_iter->second));
+    } else {
+      InternalExtensionMergeFrom(number, other_iter->second);
+    }
     other->extensions_.erase(number);
     return;
   }
 
   if (other_iter == other->extensions_.end()) {
-    other->extensions_.insert(make_pair(number, this_iter->second));
+    if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
+      other->extensions_.insert(make_pair(number, this_iter->second));
+    } else {
+      other->InternalExtensionMergeFrom(number, this_iter->second);
+    }
     extensions_.erase(number);
     return;
   }
@@ -1223,7 +1335,7 @@ bool ExtensionSet::MaybeNewExtension(int number,
                                      const FieldDescriptor* descriptor,
                                      Extension** result) {
   pair<map<int, Extension>::iterator, bool> insert_result =
-      extensions_.insert(make_pair(number, Extension()));
+    extensions_.insert(make_pair(number, Extension()));
   *result = &insert_result.first->second;
   (*result)->descriptor = descriptor;
   return insert_result.second;
@@ -1554,6 +1666,8 @@ int ExtensionSet::Extension::GetSize() const {
   return 0;
 }
 
+// This function deletes all allocated objects. This function should be only
+// called if the Extension was created with an arena.
 void ExtensionSet::Extension::Free() {
   if (is_repeated) {
     switch (cpp_type(type)) {
diff --git a/src/google/protobuf/extension_set.h b/src/google/protobuf/extension_set.h
index d6fc45df..6d6702b3 100644
--- a/src/google/protobuf/extension_set.h
+++ b/src/google/protobuf/extension_set.h
@@ -51,6 +51,7 @@
 namespace google {
 
 namespace protobuf {
+  class Arena;
   class Descriptor;                                    // descriptor.h
   class FieldDescriptor;                               // descriptor.h
   class DescriptorPool;                                // descriptor.h
@@ -157,6 +158,7 @@ class MessageSetFieldSkipper;
 class LIBPROTOBUF_EXPORT ExtensionSet {
  public:
   ExtensionSet();
+  explicit ExtensionSet(::google::protobuf::Arena* arena);
   ~ExtensionSet();
 
   // These are called at startup by protocol-compiler-generated code to
@@ -261,9 +263,13 @@ class LIBPROTOBUF_EXPORT ExtensionSet {
                            const FieldDescriptor* descriptor,
                            MessageLite* message);
   MessageLite* ReleaseMessage(int number, const MessageLite& prototype);
+  MessageLite* UnsafeArenaReleaseMessage(
+      int number, const MessageLite& prototype);
+
   MessageLite* ReleaseMessage(const FieldDescriptor* descriptor,
                               MessageFactory* factory);
 #undef desc
+  ::google::protobuf::Arena* GetArenaNoVirtual() const { return arena_; }
 
   // repeated fields -------------------------------------------------
 
@@ -421,12 +427,14 @@ class LIBPROTOBUF_EXPORT ExtensionSet {
     LazyMessageExtension() {}
     virtual ~LazyMessageExtension() {}
 
-    virtual LazyMessageExtension* New() const = 0;
+    virtual LazyMessageExtension* New(::google::protobuf::Arena* arena) const = 0;
     virtual const MessageLite& GetMessage(
         const MessageLite& prototype) const = 0;
     virtual MessageLite* MutableMessage(const MessageLite& prototype) = 0;
     virtual void SetAllocatedMessage(MessageLite *message) = 0;
     virtual MessageLite* ReleaseMessage(const MessageLite& prototype) = 0;
+    virtual MessageLite* UnsafeArenaReleaseMessage(
+        const MessageLite& prototype) = 0;
 
     virtual bool IsInitialized() const = 0;
     virtual int ByteSize() const = 0;
@@ -524,6 +532,9 @@ class LIBPROTOBUF_EXPORT ExtensionSet {
   };
 
 
+  // Merges existing Extension from other_extension
+  void InternalExtensionMergeFrom(int number, const Extension& other_extension);
+
   // Returns true and fills field_number and extension if extension is found.
   // Note to support packed repeated field compatibility, it also fills whether
   // the tag on wire is packed, which can be different from
@@ -569,7 +580,6 @@ class LIBPROTOBUF_EXPORT ExtensionSet {
                            ExtensionFinder* extension_finder,
                            MessageSetFieldSkipper* field_skipper);
 
-
   // Hack:  RepeatedPtrFieldBase declares ExtensionSet as a friend.  This
   //   friendship should automatically extend to ExtensionSet::Extension, but
   //   unfortunately some older compilers (e.g. GCC 3.4.4) do not implement this
@@ -587,7 +597,7 @@ class LIBPROTOBUF_EXPORT ExtensionSet {
   // for 100 elements or more.  Also, we want AppendToList() to order fields
   // by field number.
   std::map<int, Extension> extensions_;
-
+  ::google::protobuf::Arena* arena_;
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ExtensionSet);
 };
 
diff --git a/src/google/protobuf/extension_set_heavy.cc b/src/google/protobuf/extension_set_heavy.cc
index eae4d574..5f4ca1c3 100644
--- a/src/google/protobuf/extension_set_heavy.cc
+++ b/src/google/protobuf/extension_set_heavy.cc
@@ -169,7 +169,7 @@ MessageLite* ExtensionSet::MutableMessage(const FieldDescriptor* descriptor,
     const MessageLite* prototype =
         factory->GetPrototype(descriptor->message_type());
     extension->is_lazy = false;
-    extension->message_value = prototype->New();
+    extension->message_value = prototype->New(arena_);
     extension->is_cleared = false;
     return extension->message_value;
   } else {
@@ -196,9 +196,16 @@ MessageLite* ExtensionSet::ReleaseMessage(const FieldDescriptor* descriptor,
     if (iter->second.is_lazy) {
       ret = iter->second.lazymessage_value->ReleaseMessage(
           *factory->GetPrototype(descriptor->message_type()));
-      delete iter->second.lazymessage_value;
+      if (arena_ == NULL) {
+        delete iter->second.lazymessage_value;
+      }
     } else {
-      ret = iter->second.message_value;
+      if (arena_ != NULL) {
+        ret = (iter->second.message_value)->New();
+        ret->CheckTypeAndMergeFrom(*(iter->second.message_value));
+      } else {
+        ret = iter->second.message_value;
+      }
     }
     extensions_.erase(descriptor->number());
     return ret;
@@ -213,7 +220,7 @@ MessageLite* ExtensionSet::AddMessage(const FieldDescriptor* descriptor,
     GOOGLE_DCHECK_EQ(cpp_type(extension->type), FieldDescriptor::CPPTYPE_MESSAGE);
     extension->is_repeated = true;
     extension->repeated_message_value =
-      new RepeatedPtrField<MessageLite>();
+        ::google::protobuf::Arena::Create<RepeatedPtrField<MessageLite> >(arena_, arena_);
   } else {
     GOOGLE_DCHECK_TYPE(*extension, REPEATED, MESSAGE);
   }
@@ -230,7 +237,7 @@ MessageLite* ExtensionSet::AddMessage(const FieldDescriptor* descriptor,
     } else {
       prototype = &extension->repeated_message_value->Get(0);
     }
-    result = prototype->New();
+    result = prototype->New(arena_);
     extension->repeated_message_value->AddAllocated(result);
   }
   return result;
diff --git a/src/google/protobuf/extension_set_unittest.cc b/src/google/protobuf/extension_set_unittest.cc
index 8a00bafd..b9d07353 100644
--- a/src/google/protobuf/extension_set_unittest.cc
+++ b/src/google/protobuf/extension_set_unittest.cc
@@ -37,6 +37,7 @@
 #include <google/protobuf/unittest_mset.pb.h>
 #include <google/protobuf/test_util.h>
 #include <google/protobuf/descriptor.pb.h>
+#include <google/protobuf/arena.h>
 #include <google/protobuf/descriptor.h>
 #include <google/protobuf/dynamic_message.h>
 #include <google/protobuf/wire_format.h>
@@ -319,6 +320,117 @@ TEST(ExtensionSetTest, SwapExtensionBothFull) {
   TestUtil::ExpectAllExtensionsSet(message2);
 }
 
+TEST(ExtensionSetTest, ArenaSetAllExtension) {
+  ::google::protobuf::Arena arena1;
+  unittest::TestAllExtensions* message1 =
+      ::google::protobuf::Arena::CreateMessage<unittest::TestAllExtensions>(&arena1);
+  TestUtil::SetAllExtensions(message1);
+  TestUtil::ExpectAllExtensionsSet(*message1);
+}
+
+TEST(ExtensionSetTest, ArenaCopyConstructor) {
+  ::google::protobuf::Arena arena1;
+  unittest::TestAllExtensions* message1 =
+      ::google::protobuf::Arena::CreateMessage<unittest::TestAllExtensions>(&arena1);
+  TestUtil::SetAllExtensions(message1);
+  unittest::TestAllExtensions message2(*message1);
+  arena1.Reset();
+  TestUtil::ExpectAllExtensionsSet(message2);
+}
+
+TEST(ExtensionSetTest, ArenaMergeFrom) {
+  ::google::protobuf::Arena arena1;
+  unittest::TestAllExtensions* message1 =
+      ::google::protobuf::Arena::CreateMessage<unittest::TestAllExtensions>(&arena1);
+  TestUtil::SetAllExtensions(message1);
+  unittest::TestAllExtensions message2;
+  message2.MergeFrom(*message1);
+  arena1.Reset();
+  TestUtil::ExpectAllExtensionsSet(message2);
+}
+
+TEST(ExtensionSetTest, ArenaSetAllocatedMessageAndRelease) {
+  ::google::protobuf::Arena arena;
+  unittest::TestAllExtensions* message =
+      ::google::protobuf::Arena::CreateMessage<unittest::TestAllExtensions>(&arena);
+  EXPECT_FALSE(message->HasExtension(
+      unittest::optional_foreign_message_extension));
+  // Add a extension using SetAllocatedExtension
+  unittest::ForeignMessage* foreign_message = new unittest::ForeignMessage();
+  message->SetAllocatedExtension(unittest::optional_foreign_message_extension,
+                                 foreign_message);
+  // foreign_message is copied underneath, as foreign_message is on heap
+  // and extension_set is on an arena.
+  EXPECT_NE(foreign_message,
+            message->MutableExtension(
+                unittest::optional_foreign_message_extension));
+
+  // Underlying message is copied, and returned.
+  unittest::ForeignMessage* released_message = message->ReleaseExtension(
+      unittest::optional_foreign_message_extension);
+  delete released_message;
+  EXPECT_FALSE(message->HasExtension(
+      unittest::optional_foreign_message_extension));
+}
+
+TEST(ExtensionSetTest, SwapExtensionBothFullWithArena) {
+  ::google::protobuf::Arena arena1;
+  scoped_ptr<google::protobuf::Arena> arena2(new ::google::protobuf::Arena());
+
+  unittest::TestAllExtensions* message1 =
+      Arena::CreateMessage<unittest::TestAllExtensions>(&arena1);
+  unittest::TestAllExtensions* message2 =
+      Arena::CreateMessage<unittest::TestAllExtensions>(arena2.get());
+
+  TestUtil::SetAllExtensions(message1);
+  TestUtil::SetAllExtensions(message2);
+  message1->SetExtension(unittest::optional_int32_extension, 1);
+  message2->SetExtension(unittest::optional_int32_extension, 2);
+  message1->Swap(message2);
+  EXPECT_EQ(2, message1->GetExtension(unittest::optional_int32_extension));
+  EXPECT_EQ(1, message2->GetExtension(unittest::optional_int32_extension));
+  // Re-set the original values so ExpectAllExtensionsSet is happy.
+  message1->SetExtension(unittest::optional_int32_extension, 101);
+  message2->SetExtension(unittest::optional_int32_extension, 101);
+  TestUtil::ExpectAllExtensionsSet(*message1);
+  TestUtil::ExpectAllExtensionsSet(*message2);
+  arena2.reset(NULL);
+  TestUtil::ExpectAllExtensionsSet(*message1);
+  // Test corner cases, when one is empty and other is not.
+  ::google::protobuf::Arena arena3, arena4;
+
+  unittest::TestAllExtensions* message3 =
+      Arena::CreateMessage<unittest::TestAllExtensions>(&arena3);
+  unittest::TestAllExtensions* message4 =
+      Arena::CreateMessage<unittest::TestAllExtensions>(&arena4);
+  TestUtil::SetAllExtensions(message3);
+  message3->Swap(message4);
+  arena3.Reset();
+  TestUtil::ExpectAllExtensionsSet(*message4);
+}
+
+TEST(ExtensionSetTest, SwapFieldsOfExtensionBothFullWithArena) {
+  google::protobuf::Arena arena1;
+  google::protobuf::Arena* arena2 = new ::google::protobuf::Arena();
+
+  unittest::TestAllExtensions* message1 =
+      Arena::CreateMessage<unittest::TestAllExtensions>(&arena1);
+  unittest::TestAllExtensions* message2 =
+      Arena::CreateMessage<unittest::TestAllExtensions>(arena2);
+
+  TestUtil::SetAllExtensions(message1);
+  TestUtil::SetAllExtensions(message2);
+
+  const Reflection* reflection = message1->GetReflection();
+  vector<const FieldDescriptor*> fields;
+  reflection->ListFields(*message1, &fields);
+  reflection->SwapFields(message1, message2, fields);
+  TestUtil::ExpectAllExtensionsSet(*message1);
+  TestUtil::ExpectAllExtensionsSet(*message2);
+  delete arena2;
+  TestUtil::ExpectAllExtensionsSet(*message1);
+}
+
 TEST(ExtensionSetTest, SwapExtensionWithSelf) {
   unittest::TestAllExtensions message1;
 
diff --git a/src/google/protobuf/generated_message_reflection.cc b/src/google/protobuf/generated_message_reflection.cc
index 536de7d9..ea97aebc 100644
--- a/src/google/protobuf/generated_message_reflection.cc
+++ b/src/google/protobuf/generated_message_reflection.cc
@@ -74,6 +74,19 @@ const string& NameOfEnum(const EnumDescriptor* descriptor, int value) {
   return (d == NULL ? GetEmptyString() : d->name());
 }
 
+namespace {
+inline bool SupportsArenas(const Descriptor* descriptor) {
+  // In open-source release we enable arena support by default but as we also
+  // down-integrate descriptor.pb.(h|cc) from our internal code base which
+  // hasn't enabled arena support yet, here we need to be able to handle both
+  // cases for descriptor protos.
+  if (!Arena::is_arena_constructable<FileDescriptorProto>::type::value) {
+    return descriptor->name() != "google/protobuf/descriptor.proto";
+  }
+  return true;
+}
+}  // anonymous namespace
+
 // ===================================================================
 // Helpers for reporting usage errors (e.g. trying to use GetInt32() on
 // a string field).
@@ -177,13 +190,15 @@ GeneratedMessageReflection::GeneratedMessageReflection(
     int extensions_offset,
     const DescriptorPool* descriptor_pool,
     MessageFactory* factory,
-    int object_size)
+    int object_size,
+    int arena_offset)
   : descriptor_       (descriptor),
     default_instance_ (default_instance),
     offsets_          (offsets),
     has_bits_offset_  (has_bits_offset),
     unknown_fields_offset_(unknown_fields_offset),
     extensions_offset_(extensions_offset),
+    arena_offset_     (arena_offset),
     object_size_      (object_size),
     descriptor_pool_  ((descriptor_pool == NULL) ?
                          DescriptorPool::generated_pool() :
@@ -202,7 +217,8 @@ GeneratedMessageReflection::GeneratedMessageReflection(
     int oneof_case_offset,
     const DescriptorPool* descriptor_pool,
     MessageFactory* factory,
-    int object_size)
+    int object_size,
+    int arena_offset)
   : descriptor_       (descriptor),
     default_instance_ (default_instance),
     default_oneof_instance_ (default_oneof_instance),
@@ -211,6 +227,7 @@ GeneratedMessageReflection::GeneratedMessageReflection(
     oneof_case_offset_(oneof_case_offset),
     unknown_fields_offset_(unknown_fields_offset),
     extensions_offset_(extensions_offset),
+    arena_offset_     (arena_offset),
     object_size_      (object_size),
     descriptor_pool_  ((descriptor_pool == NULL) ?
                          DescriptorPool::generated_pool() :
@@ -220,14 +237,39 @@ GeneratedMessageReflection::GeneratedMessageReflection(
 
 GeneratedMessageReflection::~GeneratedMessageReflection() {}
 
+namespace {
+UnknownFieldSet* empty_unknown_field_set_ = NULL;
+GOOGLE_PROTOBUF_DECLARE_ONCE(empty_unknown_field_set_once_);
+
+void InitEmptyUnknownFieldSet() {
+  empty_unknown_field_set_ = new UnknownFieldSet;
+}
+
+const UnknownFieldSet& GetEmptyUnknownFieldSet() {
+  ::google::protobuf::GoogleOnceInit(&empty_unknown_field_set_once_, &InitEmptyUnknownFieldSet);
+  return *empty_unknown_field_set_;
+}
+}  // namespace
+
 const UnknownFieldSet& GeneratedMessageReflection::GetUnknownFields(
     const Message& message) const {
+  if (descriptor_->file()->syntax() == FileDescriptor::SYNTAX_PROTO3) {
+    return GetEmptyUnknownFieldSet();
+  }
+  if (unknown_fields_offset_ == kUnknownFieldSetInMetadata) {
+    return GetInternalMetadataWithArena(message).unknown_fields();
+  }
   const void* ptr = reinterpret_cast<const uint8*>(&message) +
                     unknown_fields_offset_;
   return *reinterpret_cast<const UnknownFieldSet*>(ptr);
 }
+
 UnknownFieldSet* GeneratedMessageReflection::MutableUnknownFields(
     Message* message) const {
+  if (unknown_fields_offset_ == kUnknownFieldSetInMetadata) {
+    return MutableInternalMetadataWithArena(message)->
+        mutable_unknown_fields();
+  }
   void* ptr = reinterpret_cast<uint8*>(message) + unknown_fields_offset_;
   return reinterpret_cast<UnknownFieldSet*>(ptr);
 }
@@ -303,12 +345,13 @@ int GeneratedMessageReflection::SpaceUsed(const Message& message) const {
           switch (field->options().ctype()) {
             default:  // TODO(kenton):  Support other string reps.
             case FieldOptions::STRING: {
-              const string* ptr = GetField<const string*>(message, field);
-
               // Initially, the string points to the default value stored in
               // the prototype. Only count the string if it has been changed
               // from the default value.
-              const string* default_ptr = DefaultRaw<const string*>(field);
+              const string* default_ptr =
+                  &DefaultRaw<ArenaStringPtr>(field).Get(NULL);
+              const string* ptr =
+                  &GetField<ArenaStringPtr>(message, field).Get(default_ptr);
 
               if (ptr != default_ptr) {
                 // string fields are represented by just a pointer, so also
@@ -363,8 +406,9 @@ void GeneratedMessageReflection::SwapField(
 
       case FieldDescriptor::CPPTYPE_STRING:
       case FieldDescriptor::CPPTYPE_MESSAGE:
-        MutableRaw<RepeatedPtrFieldBase>(message1, field)->Swap(
-            MutableRaw<RepeatedPtrFieldBase>(message2, field));
+        MutableRaw<RepeatedPtrFieldBase>(message1, field)->
+            Swap<GenericTypeHandler<google::protobuf::Message> >(
+              MutableRaw<RepeatedPtrFieldBase>(message2, field));
         break;
 
       default:
@@ -396,8 +440,8 @@ void GeneratedMessageReflection::SwapField(
         switch (field->options().ctype()) {
           default:  // TODO(kenton):  Support other string reps.
           case FieldOptions::STRING:
-            std::swap(*MutableRaw<string*>(message1, field),
-                      *MutableRaw<string*>(message2, field));
+            MutableRaw<ArenaStringPtr>(message1, field)->Swap(
+                MutableRaw<ArenaStringPtr>(message2, field));
             break;
         }
         break;
@@ -549,12 +593,29 @@ void GeneratedMessageReflection::Swap(
     << "\").  Note that the exact same class is required; not just the same "
        "descriptor.";
 
-  uint32* has_bits1 = MutableHasBits(message1);
-  uint32* has_bits2 = MutableHasBits(message2);
-  int has_bits_size = (descriptor_->field_count() + 31) / 32;
+  // Check that both messages are in the same arena (or both on the heap). We
+  // need to copy all data if not, due to ownership semantics.
+  if (GetArena(message1) != GetArena(message2)) {
+    // Slow copy path.
+    // Use our arena as temp space, if available.
+    Message* temp = message1->New(GetArena(message1));
+    temp->MergeFrom(*message1);
+    message1->CopyFrom(*message2);
+    message2->CopyFrom(*temp);
+    if (GetArena(message1) == NULL) {
+      delete temp;
+    }
+    return;
+  }
+
+  if (has_bits_offset_ != -1) {
+    uint32* has_bits1 = MutableHasBits(message1);
+    uint32* has_bits2 = MutableHasBits(message2);
+    int has_bits_size = (descriptor_->field_count() + 31) / 32;
 
-  for (int i = 0; i < has_bits_size; i++) {
-    std::swap(has_bits1[i], has_bits2[i]);
+    for (int i = 0; i < has_bits_size; i++) {
+      std::swap(has_bits1[i], has_bits2[i]);
+    }
   }
 
   for (int i = 0; i < descriptor_->field_count(); i++) {
@@ -715,17 +776,13 @@ void GeneratedMessageReflection::ClearField(
         case FieldDescriptor::CPPTYPE_STRING: {
           switch (field->options().ctype()) {
             default:  // TODO(kenton):  Support other string reps.
-            case FieldOptions::STRING:
-              const string* default_ptr = DefaultRaw<const string*>(field);
-              string** value = MutableRaw<string*>(message, field);
-              if (*value != default_ptr) {
-                if (field->has_default_value()) {
-                  (*value)->assign(field->default_value_string());
-                } else {
-                  (*value)->clear();
-                }
-              }
+            case FieldOptions::STRING: {
+              const string* default_ptr =
+                  &DefaultRaw<ArenaStringPtr>(field).Get(NULL);
+              MutableRaw<ArenaStringPtr>(message, field)->Destroy(default_ptr,
+                  GetArena(message));
               break;
+            }
           }
           break;
         }
@@ -994,8 +1051,11 @@ string GeneratedMessageReflection::GetString(
   } else {
     switch (field->options().ctype()) {
       default:  // TODO(kenton):  Support other string reps.
-      case FieldOptions::STRING:
-        return *GetField<const string*>(message, field);
+      case FieldOptions::STRING: {
+        const string* default_ptr =
+            &DefaultRaw<ArenaStringPtr>(field).Get(NULL);
+        return GetField<ArenaStringPtr>(message, field).Get(default_ptr);
+      }
     }
 
     GOOGLE_LOG(FATAL) << "Can't get here.";
@@ -1013,8 +1073,11 @@ const string& GeneratedMessageReflection::GetStringReference(
   } else {
     switch (field->options().ctype()) {
       default:  // TODO(kenton):  Support other string reps.
-      case FieldOptions::STRING:
-        return *GetField<const string*>(message, field);
+      case FieldOptions::STRING: {
+        const string* default_ptr =
+            &DefaultRaw<ArenaStringPtr>(field).Get(NULL);
+        return GetField<ArenaStringPtr>(message, field).Get(default_ptr);
+      }
     }
 
     GOOGLE_LOG(FATAL) << "Can't get here.";
@@ -1034,16 +1097,15 @@ void GeneratedMessageReflection::SetString(
     switch (field->options().ctype()) {
       default:  // TODO(kenton):  Support other string reps.
       case FieldOptions::STRING: {
+        const string* default_ptr =
+            &DefaultRaw<ArenaStringPtr>(field).Get(NULL);
         if (field->containing_oneof() && !HasOneofField(*message, field)) {
           ClearOneof(message, field->containing_oneof());
-          *MutableField<string*>(message, field) = new string;
-        }
-        string** ptr = MutableField<string*>(message, field);
-        if (*ptr == DefaultRaw<const string*>(field)) {
-          *ptr = new string(value);
-        } else {
-          (*ptr)->assign(value);
+          MutableField<ArenaStringPtr>(message, field)->UnsafeSetDefault(
+              default_ptr);
         }
+        MutableField<ArenaStringPtr>(message, field)->Set(default_ptr,
+            value, GetArena(message));
         break;
       }
     }
@@ -1125,42 +1187,80 @@ void GeneratedMessageReflection::AddString(
 
 // -------------------------------------------------------------------
 
+inline bool CreateUnknownEnumValues(const FileDescriptor* file) {
+  return file->syntax() == FileDescriptor::SYNTAX_PROTO3;
+}
+
 const EnumValueDescriptor* GeneratedMessageReflection::GetEnum(
     const Message& message, const FieldDescriptor* field) const {
-  USAGE_CHECK_ALL(GetEnum, SINGULAR, ENUM);
+  // Usage checked by GetEnumValue.
+  int value = GetEnumValue(message, field);
+  return field->enum_type()->FindValueByNumberCreatingIfUnknown(value);
+}
+
+int GeneratedMessageReflection::GetEnumValue(
+    const Message& message, const FieldDescriptor* field) const {
+  USAGE_CHECK_ALL(GetEnumValue, SINGULAR, ENUM);
 
-  int value;
+  int32 value;
   if (field->is_extension()) {
     value = GetExtensionSet(message).GetEnum(
       field->number(), field->default_value_enum()->number());
   } else {
     value = GetField<int>(message, field);
   }
-  const EnumValueDescriptor* result =
-    field->enum_type()->FindValueByNumber(value);
-  GOOGLE_CHECK(result != NULL) << "Value " << value << " is not valid for field "
-                        << field->full_name() << " of type "
-                        << field->enum_type()->full_name() << ".";
-  return result;
+  return value;
 }
 
 void GeneratedMessageReflection::SetEnum(
     Message* message, const FieldDescriptor* field,
     const EnumValueDescriptor* value) const {
-  USAGE_CHECK_ALL(SetEnum, SINGULAR, ENUM);
+  // Usage checked by SetEnumValue.
   USAGE_CHECK_ENUM_VALUE(SetEnum);
+  SetEnumValueInternal(message, field, value->number());
+}
+
+void GeneratedMessageReflection::SetEnumValue(
+    Message* message, const FieldDescriptor* field,
+    int value) const {
+  USAGE_CHECK_ALL(SetEnumValue, SINGULAR, ENUM);
+  if (!CreateUnknownEnumValues(descriptor_->file())) {
+    // Check that the value is valid if we don't support direct storage of
+    // unknown enum values.
+    const EnumValueDescriptor* value_desc =
+        field->enum_type()->FindValueByNumber(value);
+    if (value_desc == NULL) {
+      GOOGLE_LOG(DFATAL) << "SetEnumValue accepts only valid integer values: value "
+                  << value << " unexpected for field " << field->full_name();
+      // In production builds, DFATAL will not terminate the program, so we have
+      // to do something reasonable: just set the default value.
+      value = field->default_value_enum()->number();
+    }
+  }
+  SetEnumValueInternal(message, field, value);
+}
 
+void GeneratedMessageReflection::SetEnumValueInternal(
+    Message* message, const FieldDescriptor* field,
+    int value) const {
   if (field->is_extension()) {
     MutableExtensionSet(message)->SetEnum(field->number(), field->type(),
-                                          value->number(), field);
+                                          value, field);
   } else {
-    SetField<int>(message, field, value->number());
+    SetField<int>(message, field, value);
   }
 }
 
 const EnumValueDescriptor* GeneratedMessageReflection::GetRepeatedEnum(
     const Message& message, const FieldDescriptor* field, int index) const {
-  USAGE_CHECK_ALL(GetRepeatedEnum, REPEATED, ENUM);
+  // Usage checked by GetRepeatedEnumValue.
+  int value = GetRepeatedEnumValue(message, field, index);
+  return field->enum_type()->FindValueByNumberCreatingIfUnknown(value);
+}
+
+int GeneratedMessageReflection::GetRepeatedEnumValue(
+    const Message& message, const FieldDescriptor* field, int index) const {
+  USAGE_CHECK_ALL(GetRepeatedEnumValue, REPEATED, ENUM);
 
   int value;
   if (field->is_extension()) {
@@ -1168,41 +1268,89 @@ const EnumValueDescriptor* GeneratedMessageReflection::GetRepeatedEnum(
   } else {
     value = GetRepeatedField<int>(message, field, index);
   }
-  const EnumValueDescriptor* result =
-    field->enum_type()->FindValueByNumber(value);
-  GOOGLE_CHECK(result != NULL) << "Value " << value << " is not valid for field "
-                        << field->full_name() << " of type "
-                        << field->enum_type()->full_name() << ".";
-  return result;
+  return value;
 }
 
 void GeneratedMessageReflection::SetRepeatedEnum(
     Message* message,
     const FieldDescriptor* field, int index,
     const EnumValueDescriptor* value) const {
-  USAGE_CHECK_ALL(SetRepeatedEnum, REPEATED, ENUM);
+  // Usage checked by SetRepeatedEnumValue.
   USAGE_CHECK_ENUM_VALUE(SetRepeatedEnum);
+  SetRepeatedEnumValueInternal(message, field, index, value->number());
+}
 
+void GeneratedMessageReflection::SetRepeatedEnumValue(
+    Message* message,
+    const FieldDescriptor* field, int index,
+    int value) const {
+  USAGE_CHECK_ALL(SetRepeatedEnum, REPEATED, ENUM);
+  if (!CreateUnknownEnumValues(descriptor_->file())) {
+    // Check that the value is valid if we don't support direct storage of
+    // unknown enum values.
+    const EnumValueDescriptor* value_desc =
+        field->enum_type()->FindValueByNumber(value);
+    if (value_desc == NULL) {
+      GOOGLE_LOG(DFATAL) << "SetRepeatedEnumValue accepts only valid integer values: "
+                  << "value " << value << " unexpected for field "
+                  << field->full_name();
+      // In production builds, DFATAL will not terminate the program, so we have
+      // to do something reasonable: just set the default value.
+      value = field->default_value_enum()->number();
+    }
+  }
+  SetRepeatedEnumValueInternal(message, field, index, value);
+}
+
+void GeneratedMessageReflection::SetRepeatedEnumValueInternal(
+    Message* message,
+    const FieldDescriptor* field, int index,
+    int value) const {
   if (field->is_extension()) {
     MutableExtensionSet(message)->SetRepeatedEnum(
-      field->number(), index, value->number());
+      field->number(), index, value);
   } else {
-    SetRepeatedField<int>(message, field, index, value->number());
+    SetRepeatedField<int>(message, field, index, value);
   }
 }
 
 void GeneratedMessageReflection::AddEnum(
     Message* message, const FieldDescriptor* field,
     const EnumValueDescriptor* value) const {
-  USAGE_CHECK_ALL(AddEnum, REPEATED, ENUM);
+  // Usage checked by AddEnumValue.
   USAGE_CHECK_ENUM_VALUE(AddEnum);
+  AddEnumValueInternal(message, field, value->number());
+}
 
+void GeneratedMessageReflection::AddEnumValue(
+    Message* message, const FieldDescriptor* field,
+    int value) const {
+  USAGE_CHECK_ALL(AddEnum, REPEATED, ENUM);
+  if (!CreateUnknownEnumValues(descriptor_->file())) {
+    // Check that the value is valid if we don't support direct storage of
+    // unknown enum values.
+    const EnumValueDescriptor* value_desc =
+        field->enum_type()->FindValueByNumber(value);
+    if (value_desc == NULL) {
+      GOOGLE_LOG(DFATAL) << "AddEnumValue accepts only valid integer values: value "
+                  << value << " unexpected for field " << field->full_name();
+      // In production builds, DFATAL will not terminate the program, so we have
+      // to do something reasonable: just set the default value.
+      value = field->default_value_enum()->number();
+    }
+  }
+  AddEnumValueInternal(message, field, value);
+}
+
+void GeneratedMessageReflection::AddEnumValueInternal(
+    Message* message, const FieldDescriptor* field,
+    int value) const {
   if (field->is_extension()) {
     MutableExtensionSet(message)->AddEnum(field->number(), field->type(),
                                           field->options().packed(),
-                                          value->number(), field);
+                                          value, field);
   } else {
-    AddField<int>(message, field, value->number());
+    AddField<int>(message, field, value);
   }
 }
 
@@ -1246,7 +1394,7 @@ Message* GeneratedMessageReflection::MutableMessage(
         ClearOneof(message, field->containing_oneof());
         result_holder = MutableField<Message*>(message, field);
         const Message* default_message = DefaultRaw<const Message*>(field);
-        *result_holder = default_message->New();
+        *result_holder = default_message->New(message->GetArena());
       }
     } else {
       SetBit(message, field);
@@ -1254,14 +1402,14 @@ Message* GeneratedMessageReflection::MutableMessage(
 
     if (*result_holder == NULL) {
       const Message* default_message = DefaultRaw<const Message*>(field);
-      *result_holder = default_message->New();
+      *result_holder = default_message->New(message->GetArena());
     }
     result = *result_holder;
     return result;
   }
 }
 
-void GeneratedMessageReflection::SetAllocatedMessage(
+void GeneratedMessageReflection::UnsafeArenaSetAllocatedMessage(
     Message* message,
     Message* sub_message,
     const FieldDescriptor* field) const {
@@ -1288,12 +1436,42 @@ void GeneratedMessageReflection::SetAllocatedMessage(
       SetBit(message, field);
     }
     Message** sub_message_holder = MutableRaw<Message*>(message, field);
-    delete *sub_message_holder;
+    if (GetArena(message) == NULL) {
+      delete *sub_message_holder;
+    }
     *sub_message_holder = sub_message;
   }
 }
 
-Message* GeneratedMessageReflection::ReleaseMessage(
+void GeneratedMessageReflection::SetAllocatedMessage(
+    Message* message,
+    Message* sub_message,
+    const FieldDescriptor* field) const {
+  // If message and sub-message are in different memory ownership domains
+  // (different arenas, or one is on heap and one is not), then we may need to
+  // do a copy.
+  if (sub_message != NULL &&
+      sub_message->GetArena() != message->GetArena()) {
+    if (sub_message->GetArena() == NULL && message->GetArena() != NULL) {
+      // Case 1: parent is on an arena and child is heap-allocated. We can add
+      // the child to the arena's Own() list to free on arena destruction, then
+      // set our pointer.
+      message->GetArena()->Own(sub_message);
+      UnsafeArenaSetAllocatedMessage(message, sub_message, field);
+    } else {
+      // Case 2: all other cases. We need to make a copy. MutableMessage() will
+      // either get the existing message object, or instantiate a new one as
+      // appropriate w.r.t. our arena.
+      Message* sub_message_copy = MutableMessage(message, field);
+      sub_message_copy->CopyFrom(*sub_message);
+    }
+  } else {
+    // Same memory ownership domains.
+    UnsafeArenaSetAllocatedMessage(message, sub_message, field);
+  }
+}
+
+Message* GeneratedMessageReflection::UnsafeArenaReleaseMessage(
     Message* message,
     const FieldDescriptor* field,
     MessageFactory* factory) const {
@@ -1320,6 +1498,19 @@ Message* GeneratedMessageReflection::ReleaseMessage(
   }
 }
 
+Message* GeneratedMessageReflection::ReleaseMessage(
+    Message* message,
+    const FieldDescriptor* field,
+    MessageFactory* factory) const {
+  Message* released = UnsafeArenaReleaseMessage(message, field, factory);
+  if (GetArena(message) != NULL && released != NULL) {
+    Message* copy_from_arena = released->New();
+    copy_from_arena->CopyFrom(*released);
+    released = copy_from_arena;
+  }
+  return released;
+}
+
 const Message& GeneratedMessageReflection::GetRepeatedMessage(
     const Message& message, const FieldDescriptor* field, int index) const {
   USAGE_CHECK_ALL(GetRepeatedMessage, REPEATED, MESSAGE);
@@ -1371,8 +1562,11 @@ Message* GeneratedMessageReflection::AddMessage(
       } else {
         prototype = &repeated->Get<GenericTypeHandler<Message> >(0);
       }
-      result = prototype->New();
-      repeated->AddAllocated<GenericTypeHandler<Message> >(result);
+      result = prototype->New(message->GetArena());
+      // We can guarantee here that repeated and result are either both heap
+      // allocated or arena owned. So it is safe to call the unsafe version
+      // of AddAllocated.
+      repeated->UnsafeArenaAddAllocated<GenericTypeHandler<Message> >(result);
     }
     return result;
   }
@@ -1445,6 +1639,10 @@ const FieldDescriptor* GeneratedMessageReflection::FindKnownExtensionByNumber(
   return descriptor_pool_->FindExtensionByNumber(descriptor_, number);
 }
 
+bool GeneratedMessageReflection::SupportsUnknownEnumValues() const {
+  return CreateUnknownEnumValues(descriptor_->file());
+}
+
 // ===================================================================
 // Some private helpers.
 
@@ -1487,11 +1685,17 @@ inline const Type& GeneratedMessageReflection::DefaultRaw(
 
 inline const uint32* GeneratedMessageReflection::GetHasBits(
     const Message& message) const {
+  if (has_bits_offset_ == -1) {  // proto3 with no has-bits.
+    return NULL;
+  }
   const void* ptr = reinterpret_cast<const uint8*>(&message) + has_bits_offset_;
   return reinterpret_cast<const uint32*>(ptr);
 }
 inline uint32* GeneratedMessageReflection::MutableHasBits(
     Message* message) const {
+  if (has_bits_offset_ == -1) {
+    return NULL;
+  }
   void* ptr = reinterpret_cast<uint8*>(message) + has_bits_offset_;
   return reinterpret_cast<uint32*>(ptr);
 }
@@ -1525,25 +1729,113 @@ inline ExtensionSet* GeneratedMessageReflection::MutableExtensionSet(
   return reinterpret_cast<ExtensionSet*>(ptr);
 }
 
+inline Arena* GeneratedMessageReflection::GetArena(Message* message) const {
+  if (arena_offset_ == kNoArenaPointer) {
+    return NULL;
+  }
+
+  if (unknown_fields_offset_ == kUnknownFieldSetInMetadata) {
+    // zero-overhead arena pointer overloading UnknownFields
+    return GetInternalMetadataWithArena(*message).arena();
+  }
+
+  // Baseline case: message class has a dedicated arena pointer.
+  void* ptr = reinterpret_cast<uint8*>(message) + arena_offset_;
+  return *reinterpret_cast<Arena**>(ptr);
+}
+
+inline const InternalMetadataWithArena&
+GeneratedMessageReflection::GetInternalMetadataWithArena(
+    const Message& message) const {
+  const void* ptr = reinterpret_cast<const uint8*>(&message) + arena_offset_;
+  return *reinterpret_cast<const InternalMetadataWithArena*>(ptr);
+}
+
+inline InternalMetadataWithArena*
+GeneratedMessageReflection::MutableInternalMetadataWithArena(
+    Message* message) const {
+  void* ptr = reinterpret_cast<uint8*>(message) + arena_offset_;
+  return reinterpret_cast<InternalMetadataWithArena*>(ptr);
+}
+
 // Simple accessors for manipulating has_bits_.
 inline bool GeneratedMessageReflection::HasBit(
     const Message& message, const FieldDescriptor* field) const {
+  if (has_bits_offset_ == -1) {
+    // proto3: no has-bits. All fields present except messages, which are
+    // present only if their message-field pointer is non-NULL.
+    if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
+      return GetRaw<const Message*>(message, field) != NULL;
+    } else {
+      // Non-message field (and non-oneof, since that was handled in HasField()
+      // before calling us), and singular (again, checked in HasField). So, this
+      // field must be a scalar.
+
+      // Scalar primitive (numeric or string/bytes) fields are present if
+      // their value is non-zero (numeric) or non-empty (string/bytes).  N.B.:
+      // we must use this definition here, rather than the "scalar fields
+      // always present" in the proto3 docs, because MergeFrom() semantics
+      // require presence as "present on wire", and reflection-based merge
+      // (which uses HasField()) needs to be consistent with this.
+      switch (field->cpp_type()) {
+        case FieldDescriptor::CPPTYPE_STRING:
+          switch (field->options().ctype()) {
+            default: {
+              const string* default_ptr =
+                  &DefaultRaw<ArenaStringPtr>(field).Get(NULL);
+              return GetField<ArenaStringPtr>(message, field).Get(
+                  default_ptr).size() > 0;
+            }
+          }
+          return false;
+        case FieldDescriptor::CPPTYPE_BOOL:
+          return GetRaw<bool>(message, field) != false;
+        case FieldDescriptor::CPPTYPE_INT32:
+          return GetRaw<int32>(message, field) != 0;
+        case FieldDescriptor::CPPTYPE_INT64:
+          return GetRaw<int64>(message, field) != 0;
+        case FieldDescriptor::CPPTYPE_UINT32:
+          return GetRaw<uint32>(message, field) != 0;
+        case FieldDescriptor::CPPTYPE_UINT64:
+          return GetRaw<uint64>(message, field) != 0;
+        case FieldDescriptor::CPPTYPE_FLOAT:
+          return GetRaw<float>(message, field) != 0.0;
+        case FieldDescriptor::CPPTYPE_DOUBLE:
+          return GetRaw<double>(message, field) != 0.0;
+        case FieldDescriptor::CPPTYPE_ENUM:
+          return GetRaw<int>(message, field) != 0;
+        case FieldDescriptor::CPPTYPE_MESSAGE:
+          // handled above; avoid warning
+          GOOGLE_LOG(FATAL) << "Reached impossible case in HasBit().";
+          break;
+      }
+    }
+  }
   return GetHasBits(message)[field->index() / 32] &
     (1 << (field->index() % 32));
 }
 
 inline void GeneratedMessageReflection::SetBit(
     Message* message, const FieldDescriptor* field) const {
+  if (has_bits_offset_ == -1) {
+    return;
+  }
   MutableHasBits(message)[field->index() / 32] |= (1 << (field->index() % 32));
 }
 
 inline void GeneratedMessageReflection::ClearBit(
     Message* message, const FieldDescriptor* field) const {
+  if (has_bits_offset_ == -1) {
+    return;
+  }
   MutableHasBits(message)[field->index() / 32] &= ~(1 << (field->index() % 32));
 }
 
 inline void GeneratedMessageReflection::SwapBit(
     Message* message1, Message* message2, const FieldDescriptor* field) const {
+  if (has_bits_offset_ == -1) {
+    return;
+  }
   bool temp_has_bit = HasBit(*message1, field);
   if (HasBit(*message2, field)) {
     SetBit(message1, field);
@@ -1591,9 +1883,13 @@ inline void GeneratedMessageReflection::ClearOneof(
       case FieldDescriptor::CPPTYPE_STRING: {
         switch (field->options().ctype()) {
           default:  // TODO(kenton):  Support other string reps.
-          case FieldOptions::STRING:
-            delete *MutableRaw<string*>(message, field);
+          case FieldOptions::STRING: {
+            const string* default_ptr =
+                &DefaultRaw<ArenaStringPtr>(field).Get(NULL);
+            MutableField<ArenaStringPtr>(message, field)->
+                Destroy(default_ptr, GetArena(message));
             break;
+          }
         }
         break;
       }
@@ -1678,6 +1974,32 @@ inline Type* GeneratedMessageReflection::AddField(
   return repeated->Add();
 }
 
+MessageFactory* GeneratedMessageReflection::GetMessageFactory() const {
+  return message_factory_;
+}
+
+void* GeneratedMessageReflection::RepeatedFieldData(
+    Message* message, const FieldDescriptor* field,
+    FieldDescriptor::CppType cpp_type,
+    const Descriptor* message_type) const {
+  GOOGLE_CHECK(field->is_repeated());
+  GOOGLE_CHECK(field->cpp_type() == cpp_type ||
+        (field->cpp_type() == FieldDescriptor::CPPTYPE_ENUM &&
+         cpp_type == FieldDescriptor::CPPTYPE_INT32))
+      << "The type parameter T in RepeatedFieldRef<T> API doesn't match "
+      << "the actual field type (for enums T should be the generated enum "
+      << "type or int32).";
+  if (message_type != NULL) {
+    GOOGLE_CHECK_EQ(message_type, field->message_type());
+  }
+  if (field->is_extension()) {
+    return MutableExtensionSet(message)->MutableRawRepeatedField(
+        field->number(), field->type(), field->is_packed(), field);
+  } else {
+    return reinterpret_cast<uint8*>(message) + offsets_[field->index()];
+  }
+}
+
 }  // namespace internal
 }  // namespace protobuf
 }  // namespace google
diff --git a/src/google/protobuf/generated_message_reflection.h b/src/google/protobuf/generated_message_reflection.h
index b6671ad0..afdfd435 100644
--- a/src/google/protobuf/generated_message_reflection.h
+++ b/src/google/protobuf/generated_message_reflection.h
@@ -45,6 +45,7 @@
 // is released to components.
 #include <google/protobuf/generated_enum_reflection.h>
 #include <google/protobuf/message.h>
+#include <google/protobuf/metadata.h>
 #include <google/protobuf/unknown_field_set.h>
 
 
@@ -134,7 +135,8 @@ class LIBPROTOBUF_EXPORT GeneratedMessageReflection : public Reflection {
                              int extensions_offset,
                              const DescriptorPool* pool,
                              MessageFactory* factory,
-                             int object_size);
+                             int object_size,
+                             int arena_offset);
 
   // Similar with the construction above. Call this construction if the
   // message has oneof definition.
@@ -170,7 +172,8 @@ class LIBPROTOBUF_EXPORT GeneratedMessageReflection : public Reflection {
                              int oneof_case_offset,
                              const DescriptorPool* pool,
                              MessageFactory* factory,
-                             int object_size);
+                             int object_size,
+                             int arena_offset);
   ~GeneratedMessageReflection();
 
   // implements Reflection -------------------------------------------
@@ -217,6 +220,8 @@ class LIBPROTOBUF_EXPORT GeneratedMessageReflection : public Reflection {
                                    string* scratch) const;
   const EnumValueDescriptor* GetEnum(const Message& message,
                                      const FieldDescriptor* field) const;
+  int GetEnumValue(const Message& message,
+                   const FieldDescriptor* field) const;
   const Message& GetMessage(const Message& message,
                             const FieldDescriptor* field,
                             MessageFactory* factory = NULL) const;
@@ -245,6 +250,8 @@ class LIBPROTOBUF_EXPORT GeneratedMessageReflection : public Reflection {
                  const string& value) const;
   void SetEnum  (Message* message, const FieldDescriptor* field,
                  const EnumValueDescriptor* value) const;
+  void SetEnumValue(Message* message, const FieldDescriptor* field,
+                    int value) const;
   Message* MutableMessage(Message* message, const FieldDescriptor* field,
                           MessageFactory* factory = NULL) const;
   void SetAllocatedMessage(Message* message,
@@ -275,6 +282,9 @@ class LIBPROTOBUF_EXPORT GeneratedMessageReflection : public Reflection {
   const EnumValueDescriptor* GetRepeatedEnum(const Message& message,
                                              const FieldDescriptor* field,
                                              int index) const;
+  int GetRepeatedEnumValue(const Message& message,
+                           const FieldDescriptor* field,
+                           int index) const;
   const Message& GetRepeatedMessage(const Message& message,
                                     const FieldDescriptor* field,
                                     int index) const;
@@ -299,6 +309,8 @@ class LIBPROTOBUF_EXPORT GeneratedMessageReflection : public Reflection {
                          const string& value) const;
   void SetRepeatedEnum(Message* message, const FieldDescriptor* field,
                        int index, const EnumValueDescriptor* value) const;
+  void SetRepeatedEnumValue(Message* message, const FieldDescriptor* field,
+                            int index, int value) const;
   // Get a mutable pointer to a field with a message type.
   Message* MutableRepeatedMessage(Message* message,
                                   const FieldDescriptor* field,
@@ -323,17 +335,42 @@ class LIBPROTOBUF_EXPORT GeneratedMessageReflection : public Reflection {
   void AddEnum(Message* message,
                const FieldDescriptor* field,
                const EnumValueDescriptor* value) const;
+  void AddEnumValue(Message* message,
+                    const FieldDescriptor* field,
+                    int value) const;
   Message* AddMessage(Message* message, const FieldDescriptor* field,
                       MessageFactory* factory = NULL) const;
 
   const FieldDescriptor* FindKnownExtensionByName(const string& name) const;
   const FieldDescriptor* FindKnownExtensionByNumber(int number) const;
 
+  bool SupportsUnknownEnumValues() const;
+
+  // This value for arena_offset_ indicates that there is no arena pointer in
+  // this message (e.g., old generated code).
+  static const int kNoArenaPointer = -1;
+
+  // This value for unknown_field_offset_ indicates that there is no
+  // UnknownFieldSet in this message, and that instead, we are using the
+  // Zero-Overhead Arena Pointer trick. When this is the case, arena_offset_
+  // actually indexes to an InternalMetadataWithArena instance, which can return
+  // either an arena pointer or an UnknownFieldSet or both. It is never the case
+  // that unknown_field_offset_ == kUnknownFieldSetInMetadata && arena_offset_
+  // == kNoArenaPointer.
+  static const int kUnknownFieldSetInMetadata = -1;
+
  protected:
   virtual void* MutableRawRepeatedField(
       Message* message, const FieldDescriptor* field, FieldDescriptor::CppType,
       int ctype, const Descriptor* desc) const;
 
+  virtual MessageFactory* GetMessageFactory() const;
+
+  virtual void* RepeatedFieldData(
+      Message* message, const FieldDescriptor* field,
+      FieldDescriptor::CppType cpp_type,
+      const Descriptor* message_type) const;
+
  private:
   friend class GeneratedMessage;
 
@@ -350,6 +387,7 @@ class LIBPROTOBUF_EXPORT GeneratedMessageReflection : public Reflection {
   int oneof_case_offset_;
   int unknown_fields_offset_;
   int extensions_offset_;
+  int arena_offset_;
   int object_size_;
 
   const DescriptorPool* descriptor_pool_;
@@ -376,6 +414,11 @@ class LIBPROTOBUF_EXPORT GeneratedMessageReflection : public Reflection {
       const OneofDescriptor* oneof_descriptor) const;
   inline const ExtensionSet& GetExtensionSet(const Message& message) const;
   inline ExtensionSet* MutableExtensionSet(Message* message) const;
+  inline Arena* GetArena(Message* message) const;
+  inline const internal::InternalMetadataWithArena&
+      GetInternalMetadataWithArena(const Message& message) const;
+  inline internal::InternalMetadataWithArena*
+      MutableInternalMetadataWithArena(Message* message) const;
 
   inline bool HasBit(const Message& message,
                      const FieldDescriptor* field) const;
@@ -438,6 +481,28 @@ class LIBPROTOBUF_EXPORT GeneratedMessageReflection : public Reflection {
 
   int GetExtensionNumberOrDie(const Descriptor* type) const;
 
+  // Internal versions of EnumValue API perform no checking. Called after checks
+  // by public methods.
+  void SetEnumValueInternal(Message* message,
+                            const FieldDescriptor* field,
+                            int value) const;
+  void SetRepeatedEnumValueInternal(Message* message,
+                                    const FieldDescriptor* field,
+                                    int index,
+                                    int value) const;
+  void AddEnumValueInternal(Message* message,
+                            const FieldDescriptor* field,
+                            int value) const;
+
+
+  Message* UnsafeArenaReleaseMessage(Message* message,
+                                     const FieldDescriptor* field,
+                                     MessageFactory* factory = NULL) const;
+
+  void UnsafeArenaSetAllocatedMessage(Message* message,
+                                      Message* sub_message,
+                                      const FieldDescriptor* field) const;
+
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(GeneratedMessageReflection);
 };
 
diff --git a/src/google/protobuf/io/coded_stream.cc b/src/google/protobuf/io/coded_stream.cc
index 53449755..df88205c 100644
--- a/src/google/protobuf/io/coded_stream.cc
+++ b/src/google/protobuf/io/coded_stream.cc
@@ -40,8 +40,10 @@
 
 #include <google/protobuf/io/coded_stream_inl.h>
 #include <algorithm>
+#include <utility>
 #include <limits.h>
 #include <google/protobuf/io/zero_copy_stream.h>
+#include <google/protobuf/arena.h>
 #include <google/protobuf/stubs/common.h>
 #include <google/protobuf/stubs/stl_util.h>
 
@@ -149,6 +151,19 @@ void CodedInputStream::PopLimit(Limit limit) {
   legitimate_message_end_ = false;
 }
 
+std::pair<CodedInputStream::Limit, int>
+CodedInputStream::IncrementRecursionDepthAndPushLimit(int byte_limit) {
+  return make_pair(PushLimit(byte_limit), --recursion_budget_);
+}
+
+bool CodedInputStream::DecrementRecursionDepthAndPopLimit(Limit limit) {
+  bool result = ConsumedEntireMessage();
+  PopLimit(limit);
+  GOOGLE_DCHECK_LT(recursion_budget_, recursion_limit_);
+  ++recursion_budget_;
+  return result;
+}
+
 int CodedInputStream::BytesUntilLimit() const {
   if (current_limit_ == INT_MAX) return -1;
   int current_position = CurrentPosition();
diff --git a/src/google/protobuf/io/coded_stream.h b/src/google/protobuf/io/coded_stream.h
index 775c6067..b9c30fa3 100644
--- a/src/google/protobuf/io/coded_stream.h
+++ b/src/google/protobuf/io/coded_stream.h
@@ -110,6 +110,7 @@
 #define GOOGLE_PROTOBUF_IO_CODED_STREAM_H__
 
 #include <string>
+#include <utility>
 #ifdef _MSC_VER
   #if defined(_M_IX86) && \
       !defined(PROTOBUF_DISABLE_LITTLE_ENDIAN_OPT_FOR_TEST)
@@ -129,8 +130,8 @@
 #endif
 #include <google/protobuf/stubs/common.h>
 
-
 namespace google {
+
 namespace protobuf {
 
 class DescriptorPool;
@@ -388,6 +389,23 @@ class LIBPROTOBUF_EXPORT CodedInputStream {
   // Decrements the recursion depth.
   void DecrementRecursionDepth();
 
+  // Shorthand for make_pair(PushLimit(byte_limit), --recursion_budget_).
+  // Using this can reduce code size and complexity in some cases.  The caller
+  // is expected to check that the second part of the result is non-negative (to
+  // bail out if the depth of recursion is too high) and, if all is well, to
+  // later pass the first part of the result to PopLimit() or similar.
+  std::pair<CodedInputStream::Limit, int> IncrementRecursionDepthAndPushLimit(
+      int byte_limit);
+
+  // Helper that is equivalent to: {
+  //  bool result = ConsumedEntireMessage();
+  //  PopLimit(limit);
+  //  DecrementRecursionDepth();
+  //  return result; }
+  // Using this can reduce code size and complexity in some cases.
+  // Do not use unless the current recursion depth is greater than zero.
+  bool DecrementRecursionDepthAndPopLimit(Limit limit);
+
   // Extension Registry ----------------------------------------------
   // ADVANCED USAGE:  99.9% of people can ignore this section.
   //
@@ -470,9 +488,9 @@ class LIBPROTOBUF_EXPORT CodedInputStream {
  private:
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CodedInputStream);
 
-  ZeroCopyInputStream* input_;
   const uint8* buffer_;
   const uint8* buffer_end_;     // pointer to the end of the buffer.
+  ZeroCopyInputStream* input_;
   int total_bytes_read_;  // total bytes read from input_, including
                           // the current buffer
 
@@ -513,9 +531,10 @@ class LIBPROTOBUF_EXPORT CodedInputStream {
   // If -2: Internal: Limit has been reached, print full size when destructing.
   int total_bytes_warning_threshold_;
 
-  // Current recursion depth, controlled by IncrementRecursionDepth() and
-  // DecrementRecursionDepth().
-  int recursion_depth_;
+  // Current recursion budget, controlled by IncrementRecursionDepth() and
+  // similar.  Starts at recursion_limit_ and goes down: if this reaches
+  // -1 we are over budget.
+  int recursion_budget_;
   // Recursion depth limit, set by SetRecursionLimit().
   int recursion_limit_;
 
@@ -1132,16 +1151,17 @@ inline void CodedOutputStream::Advance(int amount) {
 }
 
 inline void CodedInputStream::SetRecursionLimit(int limit) {
+  recursion_budget_ += limit - recursion_limit_;
   recursion_limit_ = limit;
 }
 
 inline bool CodedInputStream::IncrementRecursionDepth() {
-  ++recursion_depth_;
-  return recursion_depth_ <= recursion_limit_;
+  --recursion_budget_;
+  return recursion_budget_ >= 0;
 }
 
 inline void CodedInputStream::DecrementRecursionDepth() {
-  if (recursion_depth_ > 0) --recursion_depth_;
+  if (recursion_budget_ < recursion_limit_) ++recursion_budget_;
 }
 
 inline void CodedInputStream::SetExtensionRegistry(const DescriptorPool* pool,
@@ -1163,9 +1183,9 @@ inline int CodedInputStream::BufferSize() const {
 }
 
 inline CodedInputStream::CodedInputStream(ZeroCopyInputStream* input)
-  : input_(input),
-    buffer_(NULL),
+  : buffer_(NULL),
     buffer_end_(NULL),
+    input_(input),
     total_bytes_read_(0),
     overflow_bytes_(0),
     last_tag_(0),
@@ -1175,7 +1195,7 @@ inline CodedInputStream::CodedInputStream(ZeroCopyInputStream* input)
     buffer_size_after_limit_(0),
     total_bytes_limit_(kDefaultTotalBytesLimit),
     total_bytes_warning_threshold_(kDefaultTotalBytesWarningThreshold),
-    recursion_depth_(0),
+    recursion_budget_(default_recursion_limit_),
     recursion_limit_(default_recursion_limit_),
     extension_pool_(NULL),
     extension_factory_(NULL) {
@@ -1184,9 +1204,9 @@ inline CodedInputStream::CodedInputStream(ZeroCopyInputStream* input)
 }
 
 inline CodedInputStream::CodedInputStream(const uint8* buffer, int size)
-  : input_(NULL),
-    buffer_(buffer),
+  : buffer_(buffer),
     buffer_end_(buffer + size),
+    input_(NULL),
     total_bytes_read_(size),
     overflow_bytes_(0),
     last_tag_(0),
@@ -1196,7 +1216,7 @@ inline CodedInputStream::CodedInputStream(const uint8* buffer, int size)
     buffer_size_after_limit_(0),
     total_bytes_limit_(kDefaultTotalBytesLimit),
     total_bytes_warning_threshold_(kDefaultTotalBytesWarningThreshold),
-    recursion_depth_(0),
+    recursion_budget_(default_recursion_limit_),
     recursion_limit_(default_recursion_limit_),
     extension_pool_(NULL),
     extension_factory_(NULL) {
diff --git a/src/google/protobuf/io/coded_stream_inl.h b/src/google/protobuf/io/coded_stream_inl.h
index 88c14cab..cd8d1746 100644
--- a/src/google/protobuf/io/coded_stream_inl.h
+++ b/src/google/protobuf/io/coded_stream_inl.h
@@ -36,6 +36,7 @@
 #ifndef GOOGLE_PROTOBUF_IO_CODED_STREAM_INL_H__
 #define GOOGLE_PROTOBUF_IO_CODED_STREAM_INL_H__
 
+#include <google/protobuf/stubs/common.h>
 #include <google/protobuf/io/coded_stream.h>
 #include <google/protobuf/io/zero_copy_stream_impl_lite.h>
 #include <string>
@@ -51,10 +52,12 @@ inline bool CodedInputStream::InternalReadStringInline(string* buffer,
 
   if (BufferSize() >= size) {
     STLStringResizeUninitialized(buffer, size);
-    // When buffer is empty, string_as_array(buffer) will return NULL but memcpy
-    // requires non-NULL pointers even when size is 0. Hench this check.
-    if (size > 0) {
-      memcpy(mutable_string_data(buffer), buffer_, size);
+    std::pair<char*, bool> z = as_string_data(buffer);
+    if (z.second) {
+      // Oddly enough, memcpy() requires its first two args to be non-NULL even
+      // if we copy 0 bytes.  So, we have ensured that z.first is non-NULL here.
+      GOOGLE_DCHECK(z.first != NULL);
+      memcpy(z.first, buffer_, size);
       Advance(size);
     }
     return true;
diff --git a/src/google/protobuf/io/coded_stream_unittest.cc b/src/google/protobuf/io/coded_stream_unittest.cc
index f4cb5ea1..bbe5e399 100644
--- a/src/google/protobuf/io/coded_stream_unittest.cc
+++ b/src/google/protobuf/io/coded_stream_unittest.cc
@@ -144,6 +144,7 @@ uint8 CodedStreamTest::buffer_[CodedStreamTest::kBufferSize];
 // checks.
 const int kBlockSizes[] = {1, 2, 3, 5, 7, 13, 32, 1024};
 
+
 // -------------------------------------------------------------------
 // Varint tests.
 
diff --git a/src/google/protobuf/io/gzip_stream.cc b/src/google/protobuf/io/gzip_stream.cc
index ee286961..e6037863 100644
--- a/src/google/protobuf/io/gzip_stream.cc
+++ b/src/google/protobuf/io/gzip_stream.cc
@@ -48,7 +48,7 @@ static const int kDefaultBufferSize = 65536;
 
 GzipInputStream::GzipInputStream(
     ZeroCopyInputStream* sub_stream, Format format, int buffer_size)
-    : format_(format), sub_stream_(sub_stream), zerror_(Z_OK) {
+    : format_(format), sub_stream_(sub_stream), zerror_(Z_OK), byte_count_(0) {
   zcontext_.zalloc = Z_NULL;
   zcontext_.zfree = Z_NULL;
   zcontext_.opaque = Z_NULL;
@@ -134,6 +134,7 @@ bool GzipInputStream::Next(const void** data, int* size) {
     if (zcontext_.next_out != NULL) {
       // sub_stream_ may have concatenated streams to follow
       zerror_ = inflateEnd(&zcontext_);
+      byte_count_ += zcontext_.total_out;
       if (zerror_ != Z_OK) {
         return false;
       }
@@ -178,8 +179,12 @@ bool GzipInputStream::Skip(int count) {
   return ok;
 }
 int64 GzipInputStream::ByteCount() const {
-  return zcontext_.total_out +
-    (((uintptr_t)zcontext_.next_out) - ((uintptr_t)output_position_));
+  int64 ret = byte_count_ + zcontext_.total_out;
+  if (zcontext_.next_out != NULL && output_position_ != NULL) {
+    ret += reinterpret_cast<uintptr_t>(zcontext_.next_out) -
+           reinterpret_cast<uintptr_t>(output_position_);
+  }
+  return ret;
 }
 
 // =========================================================================
diff --git a/src/google/protobuf/io/gzip_stream.h b/src/google/protobuf/io/gzip_stream.h
index c7ccc260..82445000 100644
--- a/src/google/protobuf/io/gzip_stream.h
+++ b/src/google/protobuf/io/gzip_stream.h
@@ -99,6 +99,7 @@ class LIBPROTOBUF_EXPORT GzipInputStream : public ZeroCopyInputStream {
   void* output_buffer_;
   void* output_position_;
   size_t output_buffer_length_;
+  int64 byte_count_;
 
   int Inflate(int flush);
   void DoNextOutput(const void** data, int* size);
diff --git a/src/google/protobuf/io/printer.cc b/src/google/protobuf/io/printer.cc
index c8df4177..e621ba1d 100644
--- a/src/google/protobuf/io/printer.cc
+++ b/src/google/protobuf/io/printer.cc
@@ -142,6 +142,19 @@ void Printer::Print(const char* text,
   Print(vars, text);
 }
 
+void Printer::Print(const char* text,
+                    const char* variable1, const string& value1,
+                    const char* variable2, const string& value2,
+                    const char* variable3, const string& value3,
+                    const char* variable4, const string& value4) {
+  map<string, string> vars;
+  vars[variable1] = value1;
+  vars[variable2] = value2;
+  vars[variable3] = value3;
+  vars[variable4] = value4;
+  Print(vars, text);
+}
+
 void Printer::Indent() {
   indent_ += "  ";
 }
diff --git a/src/google/protobuf/io/printer.h b/src/google/protobuf/io/printer.h
index f06cbf2f..92ce3409 100644
--- a/src/google/protobuf/io/printer.h
+++ b/src/google/protobuf/io/printer.h
@@ -86,6 +86,11 @@ class LIBPROTOBUF_EXPORT Printer {
   void Print(const char* text, const char* variable1, const string& value1,
                                const char* variable2, const string& value2,
                                const char* variable3, const string& value3);
+  // Like the first Print(), except the substitutions are given as parameters.
+  void Print(const char* text, const char* variable1, const string& value1,
+                               const char* variable2, const string& value2,
+                               const char* variable3, const string& value3,
+                               const char* variable4, const string& value4);
   // TODO(kenton):  Overloaded versions with more variables?  Three seems
   //   to be enough.
 
diff --git a/src/google/protobuf/io/zero_copy_stream_impl_lite.cc b/src/google/protobuf/io/zero_copy_stream_impl_lite.cc
index 58aff0e2..97b73b88 100644
--- a/src/google/protobuf/io/zero_copy_stream_impl_lite.cc
+++ b/src/google/protobuf/io/zero_copy_stream_impl_lite.cc
@@ -37,6 +37,7 @@
 #include <algorithm>
 #include <limits>
 
+#include <google/protobuf/stubs/casts.h>
 #include <google/protobuf/stubs/common.h>
 #include <google/protobuf/stubs/stl_util.h>
 
diff --git a/src/google/protobuf/io/zero_copy_stream_impl_lite.h b/src/google/protobuf/io/zero_copy_stream_impl_lite.h
index e18da72c..a517161d 100644
--- a/src/google/protobuf/io/zero_copy_stream_impl_lite.h
+++ b/src/google/protobuf/io/zero_copy_stream_impl_lite.h
@@ -334,6 +334,18 @@ class LIBPROTOBUF_EXPORT CopyingOutputStreamAdaptor : public ZeroCopyOutputStrea
 
 // ===================================================================
 
+// mutable_string_data() and as_string_data() are workarounds to improve
+// the performance of writing new data to an existing string.  Unfortunately
+// the methods provided by the string class are suboptimal, and using memcpy()
+// is mildly annoying because it requires its pointer args to be non-NULL even
+// if we ask it to copy 0 bytes.  Furthermore, string_as_array() has the
+// property that it always returns NULL if its arg is the empty string, exactly
+// what we want to avoid if we're using it in conjunction with memcpy()!
+// With C++11, the desired memcpy() boils down to memcpy(..., &(*s)[0], size),
+// where s is a string*.  Without C++11, &(*s)[0] is not guaranteed to be safe,
+// so we use string_as_array(), and live with the extra logic that tests whether
+// *s is empty.
+
 // Return a pointer to mutable characters underlying the given string.  The
 // return value is valid until the next time the string is resized.  We
 // trust the caller to treat the return value as an array of length s->size().
@@ -347,6 +359,19 @@ inline char* mutable_string_data(string* s) {
 #endif
 }
 
+// as_string_data(s) is equivalent to
+//  ({ char* p = mutable_string_data(s); make_pair(p, p != NULL); })
+// Sometimes it's faster: in some scenarios p cannot be NULL, and then the
+// code can avoid that check.
+inline std::pair<char*, bool> as_string_data(string* s) {
+  char *p = mutable_string_data(s);
+#ifdef LANG_CXX11
+  return make_pair(p, true);
+#else
+  return make_pair(p, p != NULL);
+#endif
+}
+
 }  // namespace io
 }  // namespace protobuf
 
diff --git a/src/google/protobuf/io/zero_copy_stream_unittest.cc b/src/google/protobuf/io/zero_copy_stream_unittest.cc
index bf978cc8..dd3d1285 100644
--- a/src/google/protobuf/io/zero_copy_stream_unittest.cc
+++ b/src/google/protobuf/io/zero_copy_stream_unittest.cc
@@ -656,6 +656,43 @@ TEST_F(IoTest, TwoSessionWriteGzip) {
   delete [] temp_buffer;
   delete [] buffer;
 }
+
+TEST_F(IoTest, GzipInputByteCountAfterClosed) {
+  string golden = "abcdefghijklmnopqrstuvwxyz";
+  string compressed = Compress(golden, GzipOutputStream::Options());
+
+  for (int i = 0; i < kBlockSizeCount; i++) {
+    ArrayInputStream arr_input(compressed.data(), compressed.size(),
+                               kBlockSizes[i]);
+    GzipInputStream gz_input(&arr_input);
+    const void* buffer;
+    int size;
+    while (gz_input.Next(&buffer, &size)) {
+      EXPECT_LE(gz_input.ByteCount(), golden.size());
+    }
+    EXPECT_EQ(golden.size(), gz_input.ByteCount());
+  }
+}
+
+TEST_F(IoTest, GzipInputByteCountAfterClosedConcatenatedStreams) {
+  string golden1 = "abcdefghijklmnopqrstuvwxyz";
+  string golden2 = "the quick brown fox jumps over the lazy dog";
+  const size_t total_size = golden1.size() + golden2.size();
+  string compressed = Compress(golden1, GzipOutputStream::Options()) +
+                      Compress(golden2, GzipOutputStream::Options());
+
+  for (int i = 0; i < kBlockSizeCount; i++) {
+    ArrayInputStream arr_input(compressed.data(), compressed.size(),
+                               kBlockSizes[i]);
+    GzipInputStream gz_input(&arr_input);
+    const void* buffer;
+    int size;
+    while (gz_input.Next(&buffer, &size)) {
+      EXPECT_LE(gz_input.ByteCount(), total_size);
+    }
+    EXPECT_EQ(total_size, gz_input.ByteCount());
+  }
+}
 #endif
 
 // There is no string input, only string output.  Also, it doesn't support
diff --git a/src/google/protobuf/message.cc b/src/google/protobuf/message.cc
index 1324ed9b..aab00fdf 100644
--- a/src/google/protobuf/message.cc
+++ b/src/google/protobuf/message.cc
@@ -40,6 +40,7 @@
 
 #include <google/protobuf/stubs/common.h>
 #include <google/protobuf/stubs/once.h>
+#include <google/protobuf/reflection_internal.h>
 #include <google/protobuf/io/coded_stream.h>
 #include <google/protobuf/io/zero_copy_stream_impl.h>
 #include <google/protobuf/descriptor.pb.h>
@@ -49,6 +50,7 @@
 #include <google/protobuf/wire_format.h>
 #include <google/protobuf/stubs/strutil.h>
 #include <google/protobuf/stubs/map_util.h>
+#include <google/protobuf/stubs/singleton.h>
 #include <google/protobuf/stubs/stl_util.h>
 
 namespace google {
@@ -222,6 +224,38 @@ void* Reflection::MutableRawRepeatedString(
 }
 
 
+// Default EnumValue API implementations. Real reflection implementations should
+// override these. However, there are several legacy implementations that do
+// not, and cannot easily be changed at the same time as the Reflection API, so
+// we provide these for now.
+// TODO: Remove these once all Reflection implementations are updated.
+int Reflection::GetEnumValue(const Message& message,
+                             const FieldDescriptor* field) const {
+  GOOGLE_LOG(FATAL) << "Unimplemented EnumValue API.";
+  return 0;
+}
+void Reflection::SetEnumValue(Message* message,
+                  const FieldDescriptor* field,
+                  int value) const {
+  GOOGLE_LOG(FATAL) << "Unimplemented EnumValue API.";
+}
+int Reflection::GetRepeatedEnumValue(
+    const Message& message,
+    const FieldDescriptor* field, int index) const {
+  GOOGLE_LOG(FATAL) << "Unimplemented EnumValue API.";
+  return 0;
+}
+void Reflection::SetRepeatedEnumValue(Message* message,
+                                  const FieldDescriptor* field, int index,
+                                  int value) const {
+  GOOGLE_LOG(FATAL) << "Unimplemented EnumValue API.";
+}
+void Reflection::AddEnumValue(Message* message,
+                  const FieldDescriptor* field,
+                  int value) const {
+  GOOGLE_LOG(FATAL) << "Unimplemented EnumValue API.";
+}
+
 // =============================================================================
 // MessageFactory
 
@@ -354,5 +388,60 @@ void MessageFactory::InternalRegisterGeneratedMessage(
 }
 
 
+MessageFactory* Reflection::GetMessageFactory() const {
+  GOOGLE_LOG(FATAL) << "Not implemented.";
+  return NULL;
+}
+
+void* Reflection::RepeatedFieldData(
+    Message* message, const FieldDescriptor* field,
+    FieldDescriptor::CppType cpp_type,
+    const Descriptor* message_type) const {
+  GOOGLE_LOG(FATAL) << "Not implemented.";
+  return NULL;
+}
+
+namespace internal {
+RepeatedFieldAccessor::~RepeatedFieldAccessor() {
+}
+}  // namespace internal
+
+const internal::RepeatedFieldAccessor* Reflection::RepeatedFieldAccessor(
+    const FieldDescriptor* field) const {
+  GOOGLE_CHECK(field->is_repeated());
+  switch (field->cpp_type()) {
+#define HANDLE_PRIMITIVE_TYPE(TYPE, type) \
+    case FieldDescriptor::CPPTYPE_ ## TYPE: \
+      return internal::Singleton<internal::RepeatedFieldPrimitiveAccessor<type> >::get();
+    HANDLE_PRIMITIVE_TYPE(INT32, int32)
+    HANDLE_PRIMITIVE_TYPE(UINT32, uint32)
+    HANDLE_PRIMITIVE_TYPE(INT64, int64)
+    HANDLE_PRIMITIVE_TYPE(UINT64, uint64)
+    HANDLE_PRIMITIVE_TYPE(FLOAT, float)
+    HANDLE_PRIMITIVE_TYPE(DOUBLE, double)
+    HANDLE_PRIMITIVE_TYPE(BOOL, bool)
+    HANDLE_PRIMITIVE_TYPE(ENUM, int32)
+#undef HANDLE_PRIMITIVE_TYPE
+    case FieldDescriptor::CPPTYPE_STRING:
+      switch (field->options().ctype()) {
+        default:
+        case FieldOptions::STRING:
+          return internal::Singleton<internal::RepeatedPtrFieldStringAccessor>::get();
+      }
+      break;
+    case FieldDescriptor::CPPTYPE_MESSAGE:
+      return internal::Singleton<internal::RepeatedPtrFieldMessageAccessor>::get();
+  }
+  GOOGLE_LOG(FATAL) << "Should not reach here.";
+  return NULL;
+}
+
+namespace internal {
+// Macro defined in repeated_field.h. We can only define the Message-specific
+// GenericTypeHandler specializations here because we depend on Message, which
+// is not part of proto2-lite hence is not available in repeated_field.h.
+DEFINE_SPECIALIZATIONS_FOR_BASE_PROTO_TYPES_NOINLINE(Message);
+}  // namespace internal
+
 }  // namespace protobuf
 }  // namespace google
diff --git a/src/google/protobuf/message.h b/src/google/protobuf/message.h
index 67d45493..1d8f2499 100644
--- a/src/google/protobuf/message.h
+++ b/src/google/protobuf/message.h
@@ -112,8 +112,10 @@
 
 #include <iosfwd>
 #include <string>
+#include <google/protobuf/stubs/type_traits.h>
 #include <vector>
 
+#include <google/protobuf/arena.h>
 #include <google/protobuf/message_lite.h>
 
 #include <google/protobuf/stubs/common.h>
@@ -121,6 +123,7 @@
 
 
 #define GOOGLE_PROTOBUF_HAS_ONEOF
+#define GOOGLE_PROTOBUF_HAS_ARENAS
 
 namespace google {
 namespace protobuf {
@@ -174,6 +177,17 @@ class LIBPROTOBUF_EXPORT Message : public MessageLite {
   // for return-type covariance.)
   virtual Message* New() const = 0;
 
+  // Construct a new instance on the arena. Ownership is passed to the caller
+  // if arena is a NULL. Default implementation allows for API compatibility
+  // during the Arena transition.
+  virtual Message* New(::google::protobuf::Arena* arena) const {
+    Message* message = New();
+    if (arena != NULL) {
+      arena->Own(message);
+    }
+    return message;
+  }
+
   // Make this message into a copy of the given message.  The given message
   // must have the same descriptor, but need not necessarily be the same class.
   // By default this is just implemented as "Clear(); MergeFrom(from);".
@@ -313,6 +327,20 @@ class LIBPROTOBUF_EXPORT Message : public MessageLite {
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Message);
 };
 
+namespace internal {
+// Forward-declare interfaces used to implement RepeatedFieldRef.
+// These are protobuf internals that users shouldn't care about.
+class RepeatedFieldAccessor;
+}  // namespace internal
+
+// Forward-declare RepeatedFieldRef templates. The second type parameter is
+// used for SFINAE tricks. Users should ignore it.
+template<typename T, typename Enable = void>
+class RepeatedFieldRef;
+
+template<typename T, typename Enable = void>
+class MutableRepeatedFieldRef;
+
 // This interface contains methods that can be used to dynamically access
 // and modify the fields of a protocol message.  Their semantics are
 // similar to the accessors the protocol compiler generates.
@@ -361,12 +389,15 @@ class LIBPROTOBUF_EXPORT Reflection {
 
   // Get the UnknownFieldSet for the message.  This contains fields which
   // were seen when the Message was parsed but were not recognized according
-  // to the Message's definition.
+  // to the Message's definition. For proto3 protos, this method will always
+  // return an empty UnknownFieldSet.
   virtual const UnknownFieldSet& GetUnknownFields(
       const Message& message) const = 0;
   // Get a mutable pointer to the UnknownFieldSet for the message.  This
   // contains fields which were seen when the Message was parsed but were not
-  // recognized according to the Message's definition.
+  // recognized according to the Message's definition. For proto3 protos, this
+  // method will return a valid mutable UnknownFieldSet pointer but modifying
+  // it won't affect the serialized bytes of the message.
   virtual UnknownFieldSet* MutableUnknownFields(Message* message) const = 0;
 
   // Estimate the amount of memory used by the message object.
@@ -385,7 +416,7 @@ class LIBPROTOBUF_EXPORT Reflection {
   virtual void ClearField(Message* message,
                           const FieldDescriptor* field) const = 0;
 
-  // Check if the oneof is set. Returns ture if any field in oneof
+  // Check if the oneof is set. Returns true if any field in oneof
   // is set, false otherwise.
   // TODO(jieluo) - make it pure virtual after updating all
   // the subclasses.
@@ -464,6 +495,15 @@ class LIBPROTOBUF_EXPORT Reflection {
                            const FieldDescriptor* field) const = 0;
   virtual const EnumValueDescriptor* GetEnum(
       const Message& message, const FieldDescriptor* field) const = 0;
+
+  // GetEnumValue() returns an enum field's value as an integer rather than
+  // an EnumValueDescriptor*. If the integer value does not correspond to a
+  // known value descriptor, a new value descriptor is created. (Such a value
+  // will only be present when the new unknown-enum-value semantics are enabled
+  // for a message.)
+  virtual int GetEnumValue(
+      const Message& message, const FieldDescriptor* field) const;
+
   // See MutableMessage() for the meaning of the "factory" parameter.
   virtual const Message& GetMessage(const Message& message,
                                     const FieldDescriptor* field,
@@ -512,6 +552,14 @@ class LIBPROTOBUF_EXPORT Reflection {
   virtual void SetEnum  (Message* message,
                          const FieldDescriptor* field,
                          const EnumValueDescriptor* value) const = 0;
+  // Set an enum field's value with an integer rather than EnumValueDescriptor.
+  // If the value does not correspond to a known enum value, either behavior is
+  // undefined (for proto2 messages), or the value is accepted silently for
+  // messages with new unknown-enum-value semantics.
+  virtual void SetEnumValue(Message* message,
+                            const FieldDescriptor* field,
+                            int value) const;
+
   // Get a mutable pointer to a field with a message type.  If a MessageFactory
   // is provided, it will be used to construct instances of the sub-message;
   // otherwise, the default factory is used.  If the field is an extension that
@@ -574,6 +622,14 @@ class LIBPROTOBUF_EXPORT Reflection {
   virtual const EnumValueDescriptor* GetRepeatedEnum(
       const Message& message,
       const FieldDescriptor* field, int index) const = 0;
+  // GetRepeatedEnumValue() returns an enum field's value as an integer rather
+  // than an EnumValueDescriptor*. If the integer value does not correspond to a
+  // known value descriptor, a new value descriptor is created. (Such a value
+  // will only be present when the new unknown-enum-value semantics are enabled
+  // for a message.)
+  virtual int GetRepeatedEnumValue(
+      const Message& message,
+      const FieldDescriptor* field, int index) const;
   virtual const Message& GetRepeatedMessage(
       const Message& message,
       const FieldDescriptor* field, int index) const = 0;
@@ -614,6 +670,13 @@ class LIBPROTOBUF_EXPORT Reflection {
   virtual void SetRepeatedEnum(Message* message,
                                const FieldDescriptor* field, int index,
                                const EnumValueDescriptor* value) const = 0;
+  // Set an enum field's value with an integer rather than EnumValueDescriptor.
+  // If the value does not correspond to a known enum value, either behavior is
+  // undefined (for proto2 messages), or the value is accepted silently for
+  // messages with new unknown-enum-value semantics.
+  virtual void SetRepeatedEnumValue(Message* message,
+                                    const FieldDescriptor* field, int index,
+                                    int value) const;
   // Get a mutable pointer to an element of a repeated field with a message
   // type.
   virtual Message* MutableRepeatedMessage(
@@ -643,12 +706,57 @@ class LIBPROTOBUF_EXPORT Reflection {
   virtual void AddEnum  (Message* message,
                          const FieldDescriptor* field,
                          const EnumValueDescriptor* value) const = 0;
+  // Set an enum field's value with an integer rather than EnumValueDescriptor.
+  // If the value does not correspond to a known enum value, either behavior is
+  // undefined (for proto2 messages), or the value is accepted silently for
+  // messages with new unknown-enum-value semantics.
+  virtual void AddEnumValue(Message* message,
+                            const FieldDescriptor* field,
+                            int value) const;
   // See MutableMessage() for comments on the "factory" parameter.
   virtual Message* AddMessage(Message* message,
                               const FieldDescriptor* field,
                               MessageFactory* factory = NULL) const = 0;
 
 
+  // Get a RepeatedFieldRef object that can be used to read the underlying
+  // repeated field. The type parameter T must be set according to the
+  // field's cpp type. The following table shows the mapping from cpp type
+  // to acceptable T.
+  //
+  //   field->cpp_type()      T
+  //   CPPTYPE_INT32        int32
+  //   CPPTYPE_UINT32       uint32
+  //   CPPTYPE_INT64        int64
+  //   CPPTYPE_UINT64       uint64
+  //   CPPTYPE_DOUBLE       double
+  //   CPPTYPE_FLOAT        float
+  //   CPPTYPE_BOOL         bool
+  //   CPPTYPE_ENUM         generated enum type or int32
+  //   CPPTYPE_STRING       string
+  //   CPPTYPE_MESSAGE      generated message type or google::protobuf::Message
+  //
+  // A RepeatedFieldRef object can be copied and the resulted object will point
+  // to the same repeated field in the same message. The object can be used as
+  // long as the message is not destroyed.
+  //
+  // Note that to use this method users need to include the header file
+  // "google/protobuf/reflection.h" (which defines the RepeatedFieldRef
+  // class templates).
+  template<typename T>
+  RepeatedFieldRef<T> GetRepeatedFieldRef(
+      const Message& message, const FieldDescriptor* field) const;
+
+  // Like GetRepeatedFieldRef() but return an object that can also be used
+  // manipulate the underlying repeated field.
+  template<typename T>
+  MutableRepeatedFieldRef<T> GetMutableRepeatedFieldRef(
+      Message* message, const FieldDescriptor* field) const;
+
+  // DEPRECATED. Please use Get(Mutable)RepeatedFieldRef() for repeated field
+  // access. The following repeated field accesors will be removed in the
+  // future.
+  //
   // Repeated field accessors  -------------------------------------------------
   // The methods above, e.g. GetRepeatedInt32(msg, fd, index), provide singular
   // access to the data in a RepeatedField.  The methods below provide aggregate
@@ -659,22 +767,30 @@ class LIBPROTOBUF_EXPORT Reflection {
   //
   // Usage example: my_doubs = refl->GetRepeatedField<double>(msg, fd);
 
+  // DEPRECATED. Please use GetRepeatedFieldRef().
+  //
   // for T = Cord and all protobuf scalar types except enums.
   template<typename T>
   const RepeatedField<T>& GetRepeatedField(
       const Message&, const FieldDescriptor*) const;
 
+  // DEPRECATED. Please use GetMutableRepeatedFieldRef().
+  //
   // for T = Cord and all protobuf scalar types except enums.
   template<typename T>
   RepeatedField<T>* MutableRepeatedField(
       Message*, const FieldDescriptor*) const;
 
+  // DEPRECATED. Please use GetRepeatedFieldRef().
+  //
   // for T = string, google::protobuf::internal::StringPieceField
   //         google::protobuf::Message & descendants.
   template<typename T>
   const RepeatedPtrField<T>& GetRepeatedPtrField(
       const Message&, const FieldDescriptor*) const;
 
+  // DEPRECATED. Please use GetMutableRepeatedFieldRef().
+  //
   // for T = string, google::protobuf::internal::StringPieceField
   //         google::protobuf::Message & descendants.
   template<typename T>
@@ -693,6 +809,39 @@ class LIBPROTOBUF_EXPORT Reflection {
   virtual const FieldDescriptor* FindKnownExtensionByNumber(
       int number) const = 0;
 
+  // Feature Flags -------------------------------------------------------------
+
+  // Does this message support storing arbitrary integer values in enum fields?
+  // If |true|, GetEnumValue/SetEnumValue and associated repeated-field versions
+  // take arbitrary integer values, and the legacy GetEnum() getter will
+  // dynamically create an EnumValueDescriptor for any integer value without
+  // one. If |false|, setting an unknown enum value via the integer-based
+  // setters results in undefined behavior (in practice, GOOGLE_DCHECK-fails).
+  //
+  // Generic code that uses reflection to handle messages with enum fields
+  // should check this flag before using the integer-based setter, and either
+  // downgrade to a compatible value or use the UnknownFieldSet if not. For
+  // example:
+  //
+  // int new_value = GetValueFromApplicationLogic();
+  // if (reflection->SupportsUnknownEnumValues()) {
+  //     reflection->SetEnumValue(message, field, new_value);
+  // } else {
+  //     if (field_descriptor->enum_type()->
+  //             FindValueByNumver(new_value) != NULL) {
+  //         reflection->SetEnumValue(message, field, new_value);
+  //     } else if (emit_unknown_enum_values) {
+  //         reflection->MutableUnknownFields(message)->AddVarint(
+  //             field->number(),
+  //             new_value);
+  //     } else {
+  //         // convert value to a compatible/default value.
+  //         new_value = CompatibleDowngrade(new_value);
+  //         reflection->SetEnumValue(message, field, new_value);
+  //     }
+  // }
+  virtual bool SupportsUnknownEnumValues() const { return false; }
+
   // ---------------------------------------------------------------------------
 
  protected:
@@ -705,7 +854,38 @@ class LIBPROTOBUF_EXPORT Reflection {
       Message* message, const FieldDescriptor* field, FieldDescriptor::CppType,
       int ctype, const Descriptor* message_type) const = 0;
 
+  virtual MessageFactory* GetMessageFactory() const;
+
+  // The following methods are used to implement (Mutable)RepeatedFieldRef.
+  // A Ref object will store a raw pointer to the repeated field data (obtained
+  // from RepeatedFieldData()) and a pointer to a Accessor (obtained from
+  // RepeatedFieldAccessor) which will be used to access the raw data.
+  //
+  // TODO(xiaofeng): Make these methods pure-virtual.
+
+  // Returns a raw pointer to the repeated field
+  //
+  // "cpp_type" and "message_type" are decuded from the type parameter T passed
+  // to Get(Mutable)RepeatedFieldRef. If T is a generated message type,
+  // "message_type" should be set to its descriptor. Otherwise "message_type"
+  // should be set to NULL. Implementations of this method should check whether
+  // "cpp_type"/"message_type" is consistent with the actual type of the field.
+  virtual void* RepeatedFieldData(
+      Message* message, const FieldDescriptor* field,
+      FieldDescriptor::CppType cpp_type,
+      const Descriptor* message_type) const;
+
+  // The returned pointer should point to a singleton instance which implements
+  // the RepeatedFieldAccessor interface.
+  virtual const internal::RepeatedFieldAccessor* RepeatedFieldAccessor(
+      const FieldDescriptor* field) const;
+
  private:
+  template<typename T, typename Enable>
+  friend class RepeatedFieldRef;
+  template<typename T, typename Enable>
+  friend class MutableRepeatedFieldRef;
+
   // Special version for specialized implementations of string.  We can't call
   // MutableRawRepeatedField directly here because we don't have access to
   // FieldOptions::* which are defined in descriptor.pb.h.  Including that
@@ -859,7 +1039,6 @@ inline RepeatedPtrField<PB>* Reflection::MutableRepeatedPtrField(
           FieldDescriptor::CPPTYPE_MESSAGE, -1,
           PB::default_instance().GetDescriptor()));
 }
-
 }  // namespace protobuf
 
 }  // namespace google
diff --git a/src/google/protobuf/message_lite.cc b/src/google/protobuf/message_lite.cc
index 14cdc91f..63be0e9b 100644
--- a/src/google/protobuf/message_lite.cc
+++ b/src/google/protobuf/message_lite.cc
@@ -34,6 +34,7 @@
 //  Sanjay Ghemawat, Jeff Dean, and others.
 
 #include <google/protobuf/message_lite.h>
+#include <google/protobuf/arena.h>
 #include <string>
 #include <google/protobuf/stubs/common.h>
 #include <google/protobuf/io/coded_stream.h>
@@ -153,6 +154,15 @@ bool InlineParsePartialFromArray(const void* data, int size,
 
 }  // namespace
 
+
+MessageLite* MessageLite::New(::google::protobuf::Arena* arena) const {
+  MessageLite* message = New();
+  if (arena != NULL) {
+    arena->Own(message);
+  }
+  return message;
+}
+
 bool MessageLite::MergeFromCodedStream(io::CodedInputStream* input) {
   return InlineMergeFromCodedStream(input, this);
 }
@@ -233,6 +243,12 @@ bool MessageLite::SerializeToCodedStream(io::CodedOutputStream* output) const {
 bool MessageLite::SerializePartialToCodedStream(
     io::CodedOutputStream* output) const {
   const int size = ByteSize();  // Force size to be cached.
+  if (size < 0) {
+    // Messages >2G cannot be serialized due to overflow computing ByteSize.
+    GOOGLE_LOG(ERROR) << "Error computing ByteSize (possible overflow?).";
+    return false;
+  }
+
   uint8* buffer = output->GetDirectBufferForNBytesAndAdvance(size);
   if (buffer != NULL) {
     uint8* end = SerializeWithCachedSizesToArray(buffer);
@@ -277,6 +293,12 @@ bool MessageLite::AppendToString(string* output) const {
 bool MessageLite::AppendPartialToString(string* output) const {
   int old_size = output->size();
   int byte_size = ByteSize();
+  if (byte_size < 0) {
+    // Messages >2G cannot be serialized due to overflow computing ByteSize.
+    GOOGLE_LOG(ERROR) << "Error computing ByteSize (possible overflow?).";
+    return false;
+  }
+
   STLStringResizeUninitialized(output, old_size + byte_size);
   uint8* start =
       reinterpret_cast<uint8*>(io::mutable_string_data(output) + old_size);
diff --git a/src/google/protobuf/message_lite.h b/src/google/protobuf/message_lite.h
index 027cabf9..106982cc 100644
--- a/src/google/protobuf/message_lite.h
+++ b/src/google/protobuf/message_lite.h
@@ -43,7 +43,7 @@
 
 namespace google {
 namespace protobuf {
-
+  class Arena;
 namespace io {
   class CodedInputStream;
   class CodedOutputStream;
@@ -88,6 +88,27 @@ class LIBPROTOBUF_EXPORT MessageLite {
   // caller.
   virtual MessageLite* New() const = 0;
 
+  // Construct a new instance on the arena. Ownership is passed to the caller
+  // if arena is a NULL. Default implementation for backwards compatibility.
+  virtual MessageLite* New(::google::protobuf::Arena* arena) const;
+
+  // Get the arena, if any, associated with this message. Virtual method
+  // required for generic operations but most arena-related operations should
+  // use the GetArenaNoVirtual() generated-code method. Default implementation
+  // to reduce code size by avoiding the need for per-type implementations when
+  // types do not implement arena support.
+  virtual ::google::protobuf::Arena* GetArena() const { return NULL; }
+
+  // Get a pointer that may be equal to this message's arena, or may not be. If
+  // the value returned by this method is equal to some arena pointer, then this
+  // message is on that arena; however, if this message is on some arena, this
+  // method may or may not return that arena's pointer. As a tradeoff, this
+  // method may be more efficient than GetArena(). The intent is to allow
+  // underlying representations that use e.g. tagged pointers to sometimes store
+  // the arena pointer directly, and sometimes in a more indirect way, and allow
+  // a fastpath comparison against the arena pointer when it's easy to obtain.
+  virtual void* GetMaybeArenaPointer() const { return GetArena(); }
+
   // Clear all fields of the message and set them to their default values.
   // Clear() avoids freeing memory, assuming that any memory allocated
   // to hold parts of the message will be needed again to hold the next
diff --git a/src/google/protobuf/message_unittest.cc b/src/google/protobuf/message_unittest.cc
index a5f339f1..ebfb4321 100644
--- a/src/google/protobuf/message_unittest.cc
+++ b/src/google/protobuf/message_unittest.cc
@@ -242,6 +242,25 @@ TEST(MessageTest, CheckOverflow) {
 
 #endif  // PROTOBUF_HAS_DEATH_TEST
 
+namespace {
+
+class NegativeByteSize : public unittest::TestRequired {
+ public:
+  virtual int ByteSize() const { return -1; }
+};
+
+}  // namespace
+
+TEST(MessageTest, SerializationFailsOnNegativeByteSize) {
+  NegativeByteSize message;
+  string string_output;
+  EXPECT_FALSE(message.AppendPartialToString(&string_output));
+
+  io::ArrayOutputStream coded_raw_output(NULL, 100);
+  io::CodedOutputStream coded_output(&coded_raw_output);
+  EXPECT_FALSE(message.SerializePartialToCodedStream(&coded_output));
+}
+
 TEST(MessageTest, BypassInitializationCheckOnSerialize) {
   unittest::TestRequired message;
   io::ArrayOutputStream raw_output(NULL, 0);
diff --git a/src/google/protobuf/metadata.h b/src/google/protobuf/metadata.h
new file mode 100644
index 00000000..30b2a6ee
--- /dev/null
+++ b/src/google/protobuf/metadata.h
@@ -0,0 +1,164 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This header file defines an internal class that encapsulates internal message
+// metadata (Unknown-field set, Arena pointer, ...) and allows its
+// representation to be made more space-efficient via various optimizations.
+//
+// Note that this is distinct from google::protobuf::Metadata, which encapsulates
+// Descriptor and Reflection pointers.
+
+#ifndef GOOGLE_PROTOBUF_METADATA_H__
+#define GOOGLE_PROTOBUF_METADATA_H__
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/arena.h>
+#include <google/protobuf/unknown_field_set.h>
+
+namespace google {
+namespace protobuf {
+namespace internal {
+
+// This is the representation for messages that support arena allocation. It
+// uses a tagged pointer to either store the Arena pointer, if there are no
+// unknown fields, or a pointer to a block of memory with both the Arena pointer
+// and the UnknownFieldSet, if there are unknown fields. This optimization
+// allows for "zero-overhead" storage of the Arena pointer, relative to the
+// above baseline implementation.
+//
+// The tagged pointer uses the LSB to disambiguate cases, and uses bit 0 == 0 to
+// indicate an arena pointer and bit 0 == 1 to indicate a UFS+Arena-container
+// pointer.
+class LIBPROTOBUF_EXPORT InternalMetadataWithArena {
+ public:
+  InternalMetadataWithArena() : ptr_(NULL) {}
+  explicit InternalMetadataWithArena(Arena* arena)
+      : ptr_ (arena) {}
+
+  ~InternalMetadataWithArena() {
+    if (have_unknown_fields() && arena() == NULL) {
+      delete PtrValue<Container>();
+    }
+    ptr_ = NULL;
+  }
+
+  inline const UnknownFieldSet& unknown_fields() const
+      GOOGLE_ATTRIBUTE_ALWAYS_INLINE {
+    if (GOOGLE_PREDICT_FALSE(have_unknown_fields())) {
+      return PtrValue<Container>()->unknown_fields_;
+    } else {
+      return *UnknownFieldSet::default_instance();
+    }
+  }
+
+  inline UnknownFieldSet* mutable_unknown_fields() GOOGLE_ATTRIBUTE_ALWAYS_INLINE {
+    if (GOOGLE_PREDICT_TRUE(have_unknown_fields())) {
+      return &PtrValue<Container>()->unknown_fields_;
+    } else {
+      return mutable_unknown_fields_slow();
+    }
+  }
+
+  inline Arena* arena() const GOOGLE_ATTRIBUTE_ALWAYS_INLINE {
+    if (GOOGLE_PREDICT_FALSE(have_unknown_fields())) {
+      return PtrValue<Container>()->arena_;
+    } else {
+      return PtrValue<Arena>();
+    }
+  }
+
+  inline bool have_unknown_fields() const GOOGLE_ATTRIBUTE_ALWAYS_INLINE {
+    return PtrTag() == kTagContainer;
+  }
+
+  inline void Swap(InternalMetadataWithArena* other) GOOGLE_ATTRIBUTE_ALWAYS_INLINE {
+    // Semantics here are that we swap only the unknown fields, not the arena
+    // pointer. We cannot simply swap ptr_ with other->ptr_ because we need to
+    // maintain our own arena ptr. Also, our ptr_ and other's ptr_ may be in
+    // different states (direct arena pointer vs. container with UFS) so we
+    // cannot simply swap ptr_ and then restore the arena pointers. We reuse
+    // UFS's swap implementation instead.
+    if (have_unknown_fields() || other->have_unknown_fields()) {
+      mutable_unknown_fields()->Swap(other->mutable_unknown_fields());
+    }
+  }
+
+  inline void* raw_arena_ptr() const GOOGLE_ATTRIBUTE_ALWAYS_INLINE {
+    return ptr_;
+  }
+
+ private:
+  void* ptr_;
+
+  // Tagged pointer implementation.
+  enum {
+    // ptr_ is an Arena*.
+    kTagArena = 0,
+    // ptr_ is a Container*.
+    kTagContainer = 1,
+  };
+  static const intptr_t kPtrTagMask = 1;
+  static const intptr_t kPtrValueMask = ~kPtrTagMask;
+
+  // Accessors for pointer tag and pointer value.
+  inline int PtrTag() const GOOGLE_ATTRIBUTE_ALWAYS_INLINE {
+    return reinterpret_cast<intptr_t>(ptr_) & kPtrTagMask;
+  }
+
+  template<typename T> T* PtrValue() const {
+    return reinterpret_cast<T*>(
+        reinterpret_cast<intptr_t>(ptr_) & kPtrValueMask);
+  }
+
+  // If ptr_'s tag is kTagContainer, it points to an instance of this struct.
+  struct Container {
+    UnknownFieldSet unknown_fields_;
+    Arena* arena_;
+  };
+
+  UnknownFieldSet* mutable_unknown_fields_slow() GOOGLE_ATTRIBUTE_NOINLINE {
+    Arena* my_arena = arena();
+    Container* container = Arena::Create<Container>(my_arena);
+    ptr_ = reinterpret_cast<void*>(
+        reinterpret_cast<intptr_t>(container) | kTagContainer);
+    container->arena_ = my_arena;
+    return &(container->unknown_fields_);
+  }
+};
+
+// Temporary compatibility typedef. Remove once this is released in components
+// and upb CL is submitted.
+typedef InternalMetadataWithArena InternalMetadata;
+
+}  // namespace internal
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_METADATA_H__
diff --git a/src/google/protobuf/new_delete_capture.cc b/src/google/protobuf/new_delete_capture.cc
new file mode 100644
index 00000000..baf42ffe
--- /dev/null
+++ b/src/google/protobuf/new_delete_capture.cc
@@ -0,0 +1,121 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This file exists for testing allocation behavior when using arenas by hooking
+// new/delete. It is a copy of //experimental/mvels/util/new_delete_capture.cc.
+
+#include <google/protobuf/new_delete_capture.h>
+
+#include <pthread.h>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/malloc_hook.h>
+#include <google/protobuf/stubs/spinlock.h>
+
+namespace google {
+namespace {
+
+pthread_t gthread;
+protobuf_unittest::NewDeleteCapture *ghooked_instance = NULL;
+SpinLock gspinlock(base::LINKER_INITIALIZED);
+
+}  // namespace
+
+namespace protobuf_unittest {
+
+NewDeleteCapture::NewDeleteCapture()
+    : alloc_count_(0),
+      alloc_size_(0),
+      alloc_ptr_(NULL),
+      free_count_(0),
+      free_ptr_(NULL) {}
+
+NewDeleteCapture::~NewDeleteCapture() { Unhook(); }
+
+void NewDeleteCapture::Reset() {
+  alloc_count_ = 0;
+  alloc_size_ = 0;
+  free_count_ = 0;
+  alloc_ptr_ = NULL;
+  free_ptr_ = NULL;
+}
+
+bool NewDeleteCapture::Hook(bool reset) {
+  SpinLockHolder spinlock(&gspinlock);
+  if (ghooked_instance != this) {
+    GOOGLE_CHECK(ghooked_instance == NULL)
+        << " NewDeleteCapture can have only 1 active instance";
+    GOOGLE_CHECK(MallocHook::AddNewHook(NewHook));
+    GOOGLE_CHECK(MallocHook::AddDeleteHook(DeleteHook));
+    gthread = pthread_self();
+    ghooked_instance = this;
+    if (reset) {
+      Reset();
+    }
+    return true;
+  }
+  return false;
+}
+
+bool NewDeleteCapture::Unhook() {
+  SpinLockHolder spinlock(&gspinlock);
+  if (ghooked_instance == this) {
+    gthread = pthread_t();
+    ghooked_instance = NULL;
+    GOOGLE_CHECK(MallocHook::RemoveDeleteHook(DeleteHook));
+    GOOGLE_CHECK(MallocHook::RemoveNewHook(NewHook));
+    return true;
+  }
+  return false;
+}
+
+void NewDeleteCapture::NewHook(const void *ptr, size_t size) {
+  SpinLockHolder spinlock(&gspinlock);
+  if (gthread == pthread_self()) {
+    auto &rthis = *ghooked_instance;
+    if (++rthis.alloc_count_ == 1) {
+      rthis.alloc_size_ = size;
+      rthis.alloc_ptr_ = ptr;
+    }
+  }
+}
+
+void NewDeleteCapture::DeleteHook(const void *ptr) {
+  SpinLockHolder spinlock(&gspinlock);
+  if (gthread == pthread_self()) {
+    auto &rthis = *ghooked_instance;
+    if (++rthis.free_count_ == 1) {
+      rthis.free_ptr_ = ptr;
+    }
+  }
+}
+
+}  // namespace protobuf_unittest
+}  // namespace google
diff --git a/src/google/protobuf/new_delete_capture.h b/src/google/protobuf/new_delete_capture.h
new file mode 100644
index 00000000..4ab550cd
--- /dev/null
+++ b/src/google/protobuf/new_delete_capture.h
@@ -0,0 +1,175 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This file exists for testing allocation behavior when using arenas by hooking
+// new/delete. It is a copy of //experimental/mvels/util/new_delete_capture.h.
+//
+// Copyright 2014 Google Inc.
+//
+// Author: Martijn Vels
+//
+// A simple class that captures memory allocations and deletes.
+//
+// This class is private to //strings and only intended to be used inside
+// unit tests. It uses the MallocHook functionality to capture memory
+// allocation and delete operations performed by the thread that activated
+// a hook on a specific instance.
+//
+// The class  captures the following information:
+// - Total allocation count (new, malloc(), etc).
+// - Total delete count (delete, free(), etc).
+// - The size and returned pointer for the first memory allocation.
+// - The pointer for the first delete operation.
+//
+// The latter 2 infos (size and pointer of first new/delete) are usefull in
+// cases where you can closely scope a Hook() / Unhook sequence around a
+// specific piece of code where you expect no more than 1 pair of new / delete
+// operations.
+//
+// Sample usage where we expect a single unique alloc / free:
+//
+//   NewDeleteCapture capture_alloc;
+//   const void *ptr;
+//   {
+//     capture_alloc.Hook();
+//     MyAllocationClass my_instance(size);
+//     capture_alloc.Unhook();
+//
+//     ptr = my_instance.ptr();
+//     GOOGLE_CHECK_EQ(1, capture_alloc.alloc_count());
+//     GOOGLE_CHECK_EQ(0, capture_alloc.free_count());
+//     GOOGLE_CHECK_EQ(size, capture_alloc.alloc_size());
+//     GOOGLE_CHECK_EQ(ptr, capture_alloc.alloc_ptr());
+//
+//     capture_alloc.Hook();
+//   }
+//   capture_alloc.Unhook();
+//   GOOGLE_CHECK_EQ(1, capture_alloc.alloc_count());
+//   GOOGLE_CHECK_EQ(1, capture_alloc.free_count());
+//   GOOGLE_CHECK_EQ(ptr, capture_alloc.free_ptr());
+//
+// You can only have one NewDeleteCapture instance active at the time. It is
+// total valid to have many instances in different threads, but only one
+// instance can have a hook active.
+//
+// Legal:
+//
+//   NewDeleteCapture capture_alloc1;
+//   NewDeleteCapture capture_alloc2;
+//   const void *ptr;
+//   {
+//     capture_alloc1.Hook();
+//     MyAllocationClass my_instance(size);
+//     capture_alloc1.Unhook();
+//
+//     capture_alloc2.Hook();
+//     my_instance.reset(size);
+//     capture_alloc2.Unhook();
+//   }
+//
+// Illegal:
+//
+//   NewDeleteCapture capture_alloc1;
+//   NewDeleteCapture capture_alloc2;
+//   const void *ptr;
+//   {
+//     capture_alloc1.Hook();
+//     MyAllocationClass my_instance(size);
+//
+//     capture_alloc2.Hook();
+//     my_instance.reset(size);
+//
+//     capture_alloc1.Unhook();
+//     capture_alloc2.Unhook();
+//   }
+//
+#ifndef GOOGLE_PROTOBUF_NEW_DELETE_CAPTURE_H__
+#define GOOGLE_PROTOBUF_NEW_DELETE_CAPTURE_H__
+
+#include <stddef.h>
+
+namespace google {
+namespace protobuf_unittest {
+
+class NewDeleteCapture {
+ public:
+  // Creates a new inactive capture instance
+  NewDeleteCapture();
+
+  // Destroys this capture instance. Active hooks are automatically removed.
+  ~NewDeleteCapture();
+
+  // Activates a hook on this instance. If reset is true (the default), all
+  // internal counters will be reset to 0.
+  // Returns true if the hook was activated, false if this instance already
+  // owned the hook.
+  // Requires no other instance owning the hook (check fails)
+  bool Hook(bool reset = true);
+
+  // De-activate the hook on this instance.
+  // Returns true if the hook was removed, false if this instance did not own
+  // the hook.
+  bool Unhook();
+
+  // Resets all counters to 0
+  void Reset();
+
+  // Returns the total number of allocations (new, malloc(), etc)
+  size_t alloc_count() const { return alloc_count_; }
+
+  // Returns the total number of deletes (delete, free(), etc)
+  size_t free_count() const { return free_count_; }
+
+  // Returns the size of the first observed allocation
+  size_t alloc_size() const { return alloc_size_; }
+
+  // Returns the allocated ptr of the first observed allocation
+  const void *alloc_ptr() const { return alloc_ptr_; }
+
+  // Returns the ptr of the first observed delete
+  const void* free_ptr() const { return free_ptr_; }
+
+ private:
+  static void NewHook(const void *ptr, size_t size);
+  static void DeleteHook(const void *ptr);
+
+ private:
+  size_t alloc_count_;
+  size_t alloc_size_;
+  const void *alloc_ptr_;
+
+  size_t free_count_;
+  const void *free_ptr_;
+};
+
+}  // namespace protobuf_unittest
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_NEW_DELETE_CAPTURE_H__
diff --git a/src/google/protobuf/no_field_presence_test.cc b/src/google/protobuf/no_field_presence_test.cc
new file mode 100644
index 00000000..f248327c
--- /dev/null
+++ b/src/google/protobuf/no_field_presence_test.cc
@@ -0,0 +1,526 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <string>
+
+#include <google/protobuf/unittest_no_field_presence.pb.h>
+#include <google/protobuf/unittest.pb.h>
+#include <google/protobuf/descriptor.pb.h>
+#include <google/protobuf/descriptor.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace {
+
+// Helper: checks that all fields have default (zero/empty) values.
+void CheckDefaultValues(
+    const proto2_nofieldpresence_unittest::TestAllTypes& m) {
+  EXPECT_EQ(0, m.optional_int32());
+  EXPECT_EQ(0, m.optional_int64());
+  EXPECT_EQ(0, m.optional_uint32());
+  EXPECT_EQ(0, m.optional_uint64());
+  EXPECT_EQ(0, m.optional_sint32());
+  EXPECT_EQ(0, m.optional_sint64());
+  EXPECT_EQ(0, m.optional_fixed32());
+  EXPECT_EQ(0, m.optional_fixed64());
+  EXPECT_EQ(0, m.optional_sfixed32());
+  EXPECT_EQ(0, m.optional_sfixed64());
+  EXPECT_EQ(0, m.optional_float());
+  EXPECT_EQ(0, m.optional_double());
+  EXPECT_EQ(false, m.optional_bool());
+  EXPECT_EQ(0, m.optional_string().size());
+  EXPECT_EQ(0, m.optional_bytes().size());
+
+  EXPECT_EQ(false, m.has_optional_nested_message());
+  // accessor for message fields returns default instance when not present
+  EXPECT_EQ(0, m.optional_nested_message().bb());
+  EXPECT_EQ(false, m.has_optional_proto2_message());
+  // Embedded proto2 messages still have proto2 semantics, e.g. non-zero default
+  // values. Here the submessage is not present but its accessor returns the
+  // default instance.
+  EXPECT_EQ(41, m.optional_proto2_message().default_int32());
+  EXPECT_EQ(false, m.has_optional_foreign_message());
+  EXPECT_EQ(proto2_nofieldpresence_unittest::TestAllTypes_NestedEnum_FOO,
+            m.optional_nested_enum());
+  EXPECT_EQ(proto2_nofieldpresence_unittest::FOREIGN_FOO,
+            m.optional_foreign_enum());
+
+
+  EXPECT_EQ(0, m.repeated_int32_size());
+  EXPECT_EQ(0, m.repeated_int64_size());
+  EXPECT_EQ(0, m.repeated_uint32_size());
+  EXPECT_EQ(0, m.repeated_uint64_size());
+  EXPECT_EQ(0, m.repeated_sint32_size());
+  EXPECT_EQ(0, m.repeated_sint64_size());
+  EXPECT_EQ(0, m.repeated_fixed32_size());
+  EXPECT_EQ(0, m.repeated_fixed64_size());
+  EXPECT_EQ(0, m.repeated_sfixed32_size());
+  EXPECT_EQ(0, m.repeated_sfixed64_size());
+  EXPECT_EQ(0, m.repeated_float_size());
+  EXPECT_EQ(0, m.repeated_double_size());
+  EXPECT_EQ(0, m.repeated_bool_size());
+  EXPECT_EQ(0, m.repeated_string_size());
+  EXPECT_EQ(0, m.repeated_bytes_size());
+  EXPECT_EQ(0, m.repeated_nested_message_size());
+  EXPECT_EQ(0, m.repeated_foreign_message_size());
+  EXPECT_EQ(0, m.repeated_proto2_message_size());
+  EXPECT_EQ(0, m.repeated_nested_enum_size());
+  EXPECT_EQ(0, m.repeated_foreign_enum_size());
+  EXPECT_EQ(0, m.repeated_lazy_message_size());
+  EXPECT_EQ(proto2_nofieldpresence_unittest::TestAllTypes::ONEOF_FIELD_NOT_SET,
+            m.oneof_field_case());
+}
+
+void FillValues(proto2_nofieldpresence_unittest::TestAllTypes* m) {
+  m->set_optional_int32(100);
+  m->set_optional_int64(101);
+  m->set_optional_uint32(102);
+  m->set_optional_uint64(103);
+  m->set_optional_sint32(104);
+  m->set_optional_sint64(105);
+  m->set_optional_fixed32(106);
+  m->set_optional_fixed64(107);
+  m->set_optional_sfixed32(108);
+  m->set_optional_sfixed64(109);
+  m->set_optional_float(110.0);
+  m->set_optional_double(111.0);
+  m->set_optional_bool(true);
+  m->set_optional_string("asdf");
+  m->set_optional_bytes("jkl;");
+  m->mutable_optional_nested_message()->set_bb(42);
+  m->mutable_optional_foreign_message()->set_c(43);
+  m->mutable_optional_proto2_message()->set_optional_int32(44);
+  m->set_optional_nested_enum(
+      proto2_nofieldpresence_unittest::TestAllTypes_NestedEnum_BAZ);
+  m->set_optional_foreign_enum(
+      proto2_nofieldpresence_unittest::FOREIGN_BAZ);
+  m->mutable_optional_lazy_message()->set_bb(45);
+  m->add_repeated_int32(100);
+  m->add_repeated_int64(101);
+  m->add_repeated_uint32(102);
+  m->add_repeated_uint64(103);
+  m->add_repeated_sint32(104);
+  m->add_repeated_sint64(105);
+  m->add_repeated_fixed32(106);
+  m->add_repeated_fixed64(107);
+  m->add_repeated_sfixed32(108);
+  m->add_repeated_sfixed64(109);
+  m->add_repeated_float(110.0);
+  m->add_repeated_double(111.0);
+  m->add_repeated_bool(true);
+  m->add_repeated_string("asdf");
+  m->add_repeated_bytes("jkl;");
+  m->add_repeated_nested_message()->set_bb(46);
+  m->add_repeated_foreign_message()->set_c(47);
+  m->add_repeated_proto2_message()->set_optional_int32(48);
+  m->add_repeated_nested_enum(
+      proto2_nofieldpresence_unittest::TestAllTypes_NestedEnum_BAZ);
+  m->add_repeated_foreign_enum(
+      proto2_nofieldpresence_unittest::FOREIGN_BAZ);
+  m->add_repeated_lazy_message()->set_bb(49);
+
+  m->set_oneof_uint32(1);
+  m->mutable_oneof_nested_message()->set_bb(50);
+  m->set_oneof_string("test");  // only this one remains set
+}
+
+void CheckNonDefaultValues(
+const proto2_nofieldpresence_unittest::TestAllTypes& m) {
+  EXPECT_EQ(100, m.optional_int32());
+  EXPECT_EQ(101, m.optional_int64());
+  EXPECT_EQ(102, m.optional_uint32());
+  EXPECT_EQ(103, m.optional_uint64());
+  EXPECT_EQ(104, m.optional_sint32());
+  EXPECT_EQ(105, m.optional_sint64());
+  EXPECT_EQ(106, m.optional_fixed32());
+  EXPECT_EQ(107, m.optional_fixed64());
+  EXPECT_EQ(108, m.optional_sfixed32());
+  EXPECT_EQ(109, m.optional_sfixed64());
+  EXPECT_EQ(110.0, m.optional_float());
+  EXPECT_EQ(111.0, m.optional_double());
+  EXPECT_EQ(true, m.optional_bool());
+  EXPECT_EQ("asdf", m.optional_string());
+  EXPECT_EQ("jkl;", m.optional_bytes());
+  EXPECT_EQ(true, m.has_optional_nested_message());
+  EXPECT_EQ(42, m.optional_nested_message().bb());
+  EXPECT_EQ(true, m.has_optional_foreign_message());
+  EXPECT_EQ(43, m.optional_foreign_message().c());
+  EXPECT_EQ(true, m.has_optional_proto2_message());
+  EXPECT_EQ(44, m.optional_proto2_message().optional_int32());
+  EXPECT_EQ(proto2_nofieldpresence_unittest::TestAllTypes_NestedEnum_BAZ,
+            m.optional_nested_enum());
+  EXPECT_EQ(proto2_nofieldpresence_unittest::FOREIGN_BAZ,
+            m.optional_foreign_enum());
+  EXPECT_EQ(true, m.has_optional_lazy_message());
+  EXPECT_EQ(45, m.optional_lazy_message().bb());
+
+  EXPECT_EQ(1, m.repeated_int32_size());
+  EXPECT_EQ(100, m.repeated_int32(0));
+  EXPECT_EQ(1, m.repeated_int64_size());
+  EXPECT_EQ(101, m.repeated_int64(0));
+  EXPECT_EQ(1, m.repeated_uint32_size());
+  EXPECT_EQ(102, m.repeated_uint32(0));
+  EXPECT_EQ(1, m.repeated_uint64_size());
+  EXPECT_EQ(103, m.repeated_uint64(0));
+  EXPECT_EQ(1, m.repeated_sint32_size());
+  EXPECT_EQ(104, m.repeated_sint32(0));
+  EXPECT_EQ(1, m.repeated_sint64_size());
+  EXPECT_EQ(105, m.repeated_sint64(0));
+  EXPECT_EQ(1, m.repeated_fixed32_size());
+  EXPECT_EQ(106, m.repeated_fixed32(0));
+  EXPECT_EQ(1, m.repeated_fixed64_size());
+  EXPECT_EQ(107, m.repeated_fixed64(0));
+  EXPECT_EQ(1, m.repeated_sfixed32_size());
+  EXPECT_EQ(108, m.repeated_sfixed32(0));
+  EXPECT_EQ(1, m.repeated_sfixed64_size());
+  EXPECT_EQ(109, m.repeated_sfixed64(0));
+  EXPECT_EQ(1, m.repeated_float_size());
+  EXPECT_EQ(110.0, m.repeated_float(0));
+  EXPECT_EQ(1, m.repeated_double_size());
+  EXPECT_EQ(111.0, m.repeated_double(0));
+  EXPECT_EQ(1, m.repeated_bool_size());
+  EXPECT_EQ(true, m.repeated_bool(0));
+  EXPECT_EQ(1, m.repeated_string_size());
+  EXPECT_EQ("asdf", m.repeated_string(0));
+  EXPECT_EQ(1, m.repeated_bytes_size());
+  EXPECT_EQ("jkl;", m.repeated_bytes(0));
+  EXPECT_EQ(1, m.repeated_nested_message_size());
+  EXPECT_EQ(46, m.repeated_nested_message(0).bb());
+  EXPECT_EQ(1, m.repeated_foreign_message_size());
+  EXPECT_EQ(47, m.repeated_foreign_message(0).c());
+  EXPECT_EQ(1, m.repeated_proto2_message_size());
+  EXPECT_EQ(48, m.repeated_proto2_message(0).optional_int32());
+  EXPECT_EQ(1, m.repeated_nested_enum_size());
+  EXPECT_EQ(proto2_nofieldpresence_unittest::TestAllTypes_NestedEnum_BAZ,
+            m.repeated_nested_enum(0));
+  EXPECT_EQ(1, m.repeated_foreign_enum_size());
+  EXPECT_EQ(proto2_nofieldpresence_unittest::FOREIGN_BAZ,
+            m.repeated_foreign_enum(0));
+  EXPECT_EQ(1, m.repeated_lazy_message_size());
+  EXPECT_EQ(49, m.repeated_lazy_message(0).bb());
+
+  EXPECT_EQ(proto2_nofieldpresence_unittest::TestAllTypes::kOneofString,
+            m.oneof_field_case());
+  EXPECT_EQ("test", m.oneof_string());
+}
+
+TEST(NoFieldPresenceTest, BasicMessageTest) {
+  proto2_nofieldpresence_unittest::TestAllTypes message;
+  // Check default values, fill all fields, check values. We just want to
+  // exercise the basic getters/setter paths here to make sure no
+  // field-presence-related changes broke these.
+  CheckDefaultValues(message);
+  FillValues(&message);
+  CheckNonDefaultValues(message);
+
+  // Clear() should be equivalent to getting a freshly-constructed message.
+  message.Clear();
+  CheckDefaultValues(message);
+}
+
+TEST(NoFieldPresenceTest, MessageFieldPresenceTest) {
+  // check that presence still works properly for message fields.
+  proto2_nofieldpresence_unittest::TestAllTypes message;
+  EXPECT_EQ(false, message.has_optional_nested_message());
+  // Getter should fetch default instance, and not cause the field to become
+  // present.
+  EXPECT_EQ(0, message.optional_nested_message().bb());
+  EXPECT_EQ(false, message.has_optional_nested_message());
+  message.mutable_optional_nested_message()->set_bb(42);
+  EXPECT_EQ(true, message.has_optional_nested_message());
+  message.clear_optional_nested_message();
+  EXPECT_EQ(false, message.has_optional_nested_message());
+
+  // Likewise for a lazy message field.
+  EXPECT_EQ(false, message.has_optional_lazy_message());
+  // Getter should fetch default instance, and not cause the field to become
+  // present.
+  EXPECT_EQ(0, message.optional_lazy_message().bb());
+  EXPECT_EQ(false, message.has_optional_lazy_message());
+  message.mutable_optional_lazy_message()->set_bb(42);
+  EXPECT_EQ(true, message.has_optional_lazy_message());
+  message.clear_optional_lazy_message();
+  EXPECT_EQ(false, message.has_optional_lazy_message());
+}
+
+TEST(NoFieldPresenceTest, ReflectionHasFieldTest) {
+  // check that HasField reports true on all scalar fields. Check that it
+  // behaves properly for message fields.
+
+  proto2_nofieldpresence_unittest::TestAllTypes message;
+  const google::protobuf::Reflection* r = message.GetReflection();
+  const google::protobuf::Descriptor* desc = message.GetDescriptor();
+
+  // Check initial state: scalars not present (due to need to be consistent with
+  // MergeFrom()), message fields not present, oneofs not present.
+  for (int i = 0; i < desc->field_count(); i++) {
+    const google::protobuf::FieldDescriptor* field = desc->field(i);
+    if (field->is_repeated()) continue;
+    EXPECT_EQ(false, r->HasField(message, field));
+  }
+
+  // Fill all fields, expect everything to report true (check oneofs below).
+  FillValues(&message);
+  for (int i = 0; i < desc->field_count(); i++) {
+    const google::protobuf::FieldDescriptor* field = desc->field(i);
+    if (field->is_repeated() || field->containing_oneof()) {
+      continue;
+    }
+    if (field->options().ctype() != google::protobuf::FieldOptions::STRING) {
+      continue;
+    }
+    EXPECT_EQ(true, r->HasField(message, field));
+  }
+
+  message.Clear();
+
+  // Check zero/empty-means-not-present semantics.
+  const google::protobuf::FieldDescriptor* field_int32 = desc->FindFieldByName(
+      "optional_int32");
+  const google::protobuf::FieldDescriptor* field_double = desc->FindFieldByName(
+      "optional_double");
+  const google::protobuf::FieldDescriptor* field_string = desc->FindFieldByName(
+      "optional_string");
+
+  EXPECT_EQ(false, r->HasField(message, field_int32));
+  EXPECT_EQ(false, r->HasField(message, field_double));
+  EXPECT_EQ(false, r->HasField(message, field_string));
+
+  message.set_optional_int32(42);
+  EXPECT_EQ(true, r->HasField(message, field_int32));
+  message.set_optional_int32(0);
+  EXPECT_EQ(false, r->HasField(message, field_int32));
+
+  message.set_optional_double(42.0);
+  EXPECT_EQ(true, r->HasField(message, field_double));
+  message.set_optional_double(0.0);
+  EXPECT_EQ(false, r->HasField(message, field_double));
+
+  message.set_optional_string("test");
+  EXPECT_EQ(true, r->HasField(message, field_string));
+  message.set_optional_string("");
+  EXPECT_EQ(false, r->HasField(message, field_string));
+}
+
+TEST(NoFieldPresenceTest, HasFieldOneofsTest) {
+  // check that HasField behaves properly for oneofs.
+  proto2_nofieldpresence_unittest::TestAllTypes message;
+
+  const google::protobuf::Reflection* r = message.GetReflection();
+  const google::protobuf::Descriptor* desc = message.GetDescriptor();
+  const google::protobuf::FieldDescriptor* desc_oneof_uint32 =
+      desc->FindFieldByName("oneof_uint32");
+  const google::protobuf::FieldDescriptor* desc_oneof_nested_message =
+      desc->FindFieldByName("oneof_nested_message");
+  const google::protobuf::FieldDescriptor* desc_oneof_string =
+      desc->FindFieldByName("oneof_string");
+  GOOGLE_CHECK_NOTNULL(desc_oneof_uint32);
+  GOOGLE_CHECK_NOTNULL(desc_oneof_nested_message);
+  GOOGLE_CHECK_NOTNULL(desc_oneof_string);
+
+  EXPECT_EQ(false, r->HasField(message, desc_oneof_uint32));
+  EXPECT_EQ(false, r->HasField(message, desc_oneof_nested_message));
+  EXPECT_EQ(false, r->HasField(message, desc_oneof_string));
+
+  message.set_oneof_string("test");
+  EXPECT_EQ(false, r->HasField(message, desc_oneof_uint32));
+  EXPECT_EQ(false, r->HasField(message, desc_oneof_nested_message));
+  EXPECT_EQ(true, r->HasField(message, desc_oneof_string));
+  message.mutable_oneof_nested_message()->set_bb(42);
+  EXPECT_EQ(false, r->HasField(message, desc_oneof_uint32));
+  EXPECT_EQ(true, r->HasField(message, desc_oneof_nested_message));
+  EXPECT_EQ(false, r->HasField(message, desc_oneof_string));
+
+  message.Clear();
+  EXPECT_EQ(false, r->HasField(message, desc_oneof_uint32));
+  EXPECT_EQ(false, r->HasField(message, desc_oneof_nested_message));
+  EXPECT_EQ(false, r->HasField(message, desc_oneof_string));
+}
+
+TEST(NoFieldPresenceTest, DontSerializeDefaultValuesTest) {
+  // check that serialized data contains only non-zero numeric fields/non-empty
+  // string/byte fields.
+  proto2_nofieldpresence_unittest::TestAllTypes message;
+  string output;
+
+  // All default values -> no output.
+  message.SerializeToString(&output);
+  EXPECT_EQ(0, output.size());
+
+  // Zero values -> still no output.
+  message.set_optional_int32(0);
+  message.set_optional_int64(0);
+  message.set_optional_uint32(0);
+  message.set_optional_uint64(0);
+  message.set_optional_sint32(0);
+  message.set_optional_sint64(0);
+  message.set_optional_fixed32(0);
+  message.set_optional_fixed64(0);
+  message.set_optional_sfixed32(0);
+  message.set_optional_sfixed64(0);
+  message.set_optional_float(0);
+  message.set_optional_double(0);
+  message.set_optional_bool(0);
+  message.set_optional_string("");
+  message.set_optional_bytes("");
+  message.set_optional_nested_enum(
+      proto2_nofieldpresence_unittest::TestAllTypes_NestedEnum_FOO);  // first enum entry
+  message.set_optional_foreign_enum(
+      proto2_nofieldpresence_unittest::FOREIGN_FOO);  // first enum entry
+
+  message.SerializeToString(&output);
+  EXPECT_EQ(0, output.size());
+
+  message.set_optional_int32(1);
+  message.SerializeToString(&output);
+  EXPECT_EQ(2, output.size());
+  EXPECT_EQ("\x08\x01", output);
+
+  message.set_optional_int32(0);
+  message.SerializeToString(&output);
+  EXPECT_EQ(0, output.size());
+}
+
+TEST(NoFieldPresenceTest, MergeFromIfNonzeroTest) {
+  // check that MergeFrom copies if nonzero/nondefault only.
+  proto2_nofieldpresence_unittest::TestAllTypes source;
+  proto2_nofieldpresence_unittest::TestAllTypes dest;
+
+  dest.set_optional_int32(42);
+  dest.set_optional_string("test");
+  source.set_optional_int32(0);
+  source.set_optional_string("");
+  // MergeFrom() copies only if present in serialization, i.e., non-zero.
+  dest.MergeFrom(source);
+  EXPECT_EQ(42, dest.optional_int32());
+  EXPECT_EQ("test", dest.optional_string());
+
+  source.set_optional_int32(84);
+  source.set_optional_string("test2");
+  dest.MergeFrom(source);
+  EXPECT_EQ(84, dest.optional_int32());
+  EXPECT_EQ("test2", dest.optional_string());
+}
+
+TEST(NoFieldPresenceTest, IsInitializedTest) {
+  // Check that IsInitialized works properly.
+  proto2_nofieldpresence_unittest::TestProto2Required message;
+
+  EXPECT_EQ(true, message.IsInitialized());
+  message.mutable_proto2()->set_a(1);
+  EXPECT_EQ(false, message.IsInitialized());
+  message.mutable_proto2()->set_b(1);
+  EXPECT_EQ(false, message.IsInitialized());
+  message.mutable_proto2()->set_c(1);
+  EXPECT_EQ(true, message.IsInitialized());
+}
+
+TEST(NoFieldPresenceTest, LazyMessageFieldHasBit) {
+  // Check that has-bit interaction with lazy message works (has-bit before and
+  // after lazy decode).
+  proto2_nofieldpresence_unittest::TestAllTypes message;
+  const google::protobuf::Reflection* r = message.GetReflection();
+  const google::protobuf::Descriptor* desc = message.GetDescriptor();
+  const google::protobuf::FieldDescriptor* field = desc->FindFieldByName(
+      "optional_lazy_message");
+  GOOGLE_CHECK_NOTNULL(field);
+
+  EXPECT_EQ(false, message.has_optional_lazy_message());
+  EXPECT_EQ(false, r->HasField(message, field));
+
+  message.mutable_optional_lazy_message()->set_bb(42);
+  EXPECT_EQ(true, message.has_optional_lazy_message());
+  EXPECT_EQ(true, r->HasField(message, field));
+
+  // Serialize and parse with a new message object so that lazy field on new
+  // object is in unparsed state.
+  string output;
+  message.SerializeToString(&output);
+  proto2_nofieldpresence_unittest::TestAllTypes message2;
+  message2.ParseFromString(output);
+
+  EXPECT_EQ(true, message2.has_optional_lazy_message());
+  EXPECT_EQ(true, r->HasField(message2, field));
+
+  // Access field to force lazy parse.
+  EXPECT_EQ(42, message.optional_lazy_message().bb());
+  EXPECT_EQ(true, message2.has_optional_lazy_message());
+  EXPECT_EQ(true, r->HasField(message2, field));
+}
+
+TEST(NoFieldPresenceTest, OneofPresence) {
+  proto2_nofieldpresence_unittest::TestAllTypes message;
+  // oneof fields still have field presence -- ensure that this goes on the wire
+  // even though its value is the empty string.
+  message.set_oneof_string("");
+  string serialized;
+  message.SerializeToString(&serialized);
+  // Tag: 113 --> tag is (113 << 3) | 2 (length delimited) = 906
+  // varint: 0x8a 0x07
+  // Length: 0x00
+  EXPECT_EQ(3, serialized.size());
+  EXPECT_EQ(static_cast<char>(0x8a), serialized.at(0));
+  EXPECT_EQ(static_cast<char>(0x07), serialized.at(1));
+  EXPECT_EQ(static_cast<char>(0x00), serialized.at(2));
+
+  message.Clear();
+  EXPECT_TRUE(message.ParseFromString(serialized));
+  EXPECT_EQ(proto2_nofieldpresence_unittest::TestAllTypes::kOneofString,
+            message.oneof_field_case());
+
+  // Also test int32 and enum fields.
+  message.Clear();
+  message.set_oneof_uint32(0);  // would not go on wire if ordinary field.
+  message.SerializeToString(&serialized);
+  EXPECT_EQ(3, serialized.size());
+  EXPECT_TRUE(message.ParseFromString(serialized));
+  EXPECT_EQ(proto2_nofieldpresence_unittest::TestAllTypes::kOneofUint32,
+            message.oneof_field_case());
+
+  message.Clear();
+  message.set_oneof_enum(proto2_nofieldpresence_unittest::
+                         TestAllTypes_NestedEnum_FOO);  // default value.
+  message.SerializeToString(&serialized);
+  EXPECT_EQ(3, serialized.size());
+  EXPECT_TRUE(message.ParseFromString(serialized));
+  EXPECT_EQ(proto2_nofieldpresence_unittest::TestAllTypes::kOneofEnum,
+            message.oneof_field_case());
+
+  message.Clear();
+  message.set_oneof_string("test");
+  message.clear_oneof_string();
+  EXPECT_EQ(0, message.ByteSize());
+}
+
+}  // namespace
+}  // namespace protobuf
+
+}  // namespace google
diff --git a/src/google/protobuf/preserve_unknown_enum_test.cc b/src/google/protobuf/preserve_unknown_enum_test.cc
new file mode 100644
index 00000000..e988a5cb
--- /dev/null
+++ b/src/google/protobuf/preserve_unknown_enum_test.cc
@@ -0,0 +1,230 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/unittest.pb.h>
+#include <google/protobuf/unittest_preserve_unknown_enum.pb.h>
+#include <google/protobuf/dynamic_message.h>
+#include <google/protobuf/descriptor.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace {
+
+void FillMessage(
+    proto2_preserve_unknown_enum_unittest::MyMessagePlusExtra* message) {
+  message->set_e(
+      proto2_preserve_unknown_enum_unittest::E_EXTRA);
+  message->add_repeated_e(
+      proto2_preserve_unknown_enum_unittest::E_EXTRA);
+  message->add_repeated_packed_e(
+      proto2_preserve_unknown_enum_unittest::E_EXTRA);
+  message->set_oneof_e_1(
+      proto2_preserve_unknown_enum_unittest::E_EXTRA);
+}
+
+void CheckMessage(
+    const proto2_preserve_unknown_enum_unittest::MyMessagePlusExtra& message) {
+  EXPECT_EQ(proto2_preserve_unknown_enum_unittest::E_EXTRA,
+            message.e());
+  EXPECT_EQ(1, message.repeated_e_size());
+  EXPECT_EQ(proto2_preserve_unknown_enum_unittest::E_EXTRA,
+            message.repeated_e(0));
+  EXPECT_EQ(1, message.repeated_packed_e_size());
+  EXPECT_EQ(proto2_preserve_unknown_enum_unittest::E_EXTRA,
+            message.repeated_packed_e(0));
+  EXPECT_EQ(proto2_preserve_unknown_enum_unittest::E_EXTRA,
+            message.oneof_e_1());
+}
+
+void CheckMessage(
+    const proto2_preserve_unknown_enum_unittest::MyMessage& message) {
+  EXPECT_EQ(static_cast<int>(
+              proto2_preserve_unknown_enum_unittest::E_EXTRA),
+            static_cast<int>(message.e()));
+  EXPECT_EQ(1, message.repeated_e_size());
+  EXPECT_EQ(static_cast<int>(
+              proto2_preserve_unknown_enum_unittest::E_EXTRA),
+            static_cast<int>(message.repeated_e(0)));
+  EXPECT_EQ(1, message.repeated_packed_e_size());
+  EXPECT_EQ(static_cast<int>(
+              proto2_preserve_unknown_enum_unittest::E_EXTRA),
+            static_cast<int>(message.repeated_packed_e(0)));
+  EXPECT_EQ(static_cast<int>(
+              proto2_preserve_unknown_enum_unittest::E_EXTRA),
+            static_cast<int>(message.oneof_e_1()));
+}
+
+}  // anonymous namespace
+
+// Test that parsing preserves an unknown value in the enum field and does not
+// punt it to the UnknownFieldSet.
+TEST(PreserveUnknownEnumTest, PreserveParseAndSerialize) {
+  proto2_preserve_unknown_enum_unittest::MyMessagePlusExtra orig_message;
+  FillMessage(&orig_message);
+  string serialized;
+  orig_message.SerializeToString(&serialized);
+
+  proto2_preserve_unknown_enum_unittest::MyMessage message;
+  EXPECT_EQ(true, message.ParseFromString(serialized));
+  CheckMessage(message);
+
+  serialized.clear();
+  message.SerializeToString(&serialized);
+  EXPECT_EQ(true, orig_message.ParseFromString(serialized));
+  CheckMessage(orig_message);
+}
+
+// Test that reflection based implementation also keeps unknown enum values and
+// doesn't put them into UnknownFieldSet.
+TEST(PreserveUnknownEnumTest, PreserveParseAndSerializeDynamicMessage) {
+  proto2_preserve_unknown_enum_unittest::MyMessagePlusExtra orig_message;
+  FillMessage(&orig_message);
+  string serialized = orig_message.SerializeAsString();
+
+  google::protobuf::DynamicMessageFactory factory;
+  scoped_ptr<google::protobuf::Message> message(factory.GetPrototype(
+      proto2_preserve_unknown_enum_unittest::MyMessage::descriptor())->New());
+  EXPECT_EQ(true, message->ParseFromString(serialized));
+  message->DiscardUnknownFields();
+
+  serialized = message->SerializeAsString();
+  EXPECT_EQ(true, orig_message.ParseFromString(serialized));
+  CheckMessage(orig_message);
+}
+
+// Test that reflection provides EnumValueDescriptors for unknown values.
+TEST(PreserveUnknownEnumTest, DynamicEnumValueDescriptors) {
+  proto2_preserve_unknown_enum_unittest::MyMessagePlusExtra orig_message;
+  FillMessage(&orig_message);
+  string serialized;
+  orig_message.SerializeToString(&serialized);
+
+  proto2_preserve_unknown_enum_unittest::MyMessage message;
+  EXPECT_EQ(true, message.ParseFromString(serialized));
+  CheckMessage(message);
+
+  const google::protobuf::Reflection* r = message.GetReflection();
+  const google::protobuf::Descriptor* d = message.GetDescriptor();
+  const google::protobuf::FieldDescriptor* field = d->FindFieldByName("e");
+
+  // This should dynamically create an EnumValueDescriptor.
+  const google::protobuf::EnumValueDescriptor* enum_value = r->GetEnum(message, field);
+  EXPECT_EQ(enum_value->number(),
+            static_cast<int>(proto2_preserve_unknown_enum_unittest::E_EXTRA));
+
+  // Fetching value for a second time should return the same pointer.
+  const google::protobuf::EnumValueDescriptor* enum_value_second =
+      r->GetEnum(message, field);
+  EXPECT_EQ(enum_value, enum_value_second);
+
+  // Check the repeated case too.
+  const google::protobuf::FieldDescriptor* repeated_field =
+      d->FindFieldByName("repeated_e");
+  enum_value = r->GetRepeatedEnum(message, repeated_field, 0);
+  EXPECT_EQ(enum_value->number(),
+            static_cast<int>(proto2_preserve_unknown_enum_unittest::E_EXTRA));
+  // Should reuse the same EnumValueDescriptor, even for a different field.
+  EXPECT_EQ(enum_value, enum_value_second);
+
+  // We should be able to use the returned value descriptor to set a value on
+  // another message.
+  google::protobuf::Message* m = message.New();
+  r->SetEnum(m, field, enum_value);
+  EXPECT_EQ(enum_value, r->GetEnum(*m, field));
+  delete m;
+}
+
+// Test that the new integer-based enum reflection API works.
+TEST(PreserveUnknownEnumTest, IntegerEnumReflectionAPI) {
+  proto2_preserve_unknown_enum_unittest::MyMessage message;
+  const google::protobuf::Reflection* r = message.GetReflection();
+  const google::protobuf::Descriptor* d = message.GetDescriptor();
+
+  const google::protobuf::FieldDescriptor* singular_field = d->FindFieldByName("e");
+  const google::protobuf::FieldDescriptor* repeated_field =
+      d->FindFieldByName("repeated_e");
+
+  r->SetEnumValue(&message, singular_field, 42);
+  EXPECT_EQ(42, r->GetEnumValue(message, singular_field));
+  r->AddEnumValue(&message, repeated_field, 42);
+  r->AddEnumValue(&message, repeated_field, 42);
+  EXPECT_EQ(42, r->GetRepeatedEnumValue(message, repeated_field, 0));
+  r->SetRepeatedEnumValue(&message, repeated_field, 1, 84);
+  EXPECT_EQ(84, r->GetRepeatedEnumValue(message, repeated_field, 1));
+  const google::protobuf::EnumValueDescriptor* enum_value = r->GetEnum(message,
+                                                             singular_field);
+  EXPECT_EQ(42, enum_value->number());
+}
+
+// Test that the EnumValue API works properly for proto2 messages as well.
+TEST(PreserveUnknownEnumTest, Proto2CatchesUnknownValues) {
+  protobuf_unittest::TestAllTypes message;  // proto2 message
+  const google::protobuf::Reflection* r = message.GetReflection();
+  const google::protobuf::Descriptor* d = message.GetDescriptor();
+  const google::protobuf::FieldDescriptor* singular_field =
+      d->FindFieldByName("optional_nested_enum");
+  const google::protobuf::FieldDescriptor* repeated_field =
+      d->FindFieldByName("repeated_nested_enum");
+  // Add one element to the repeated field so that we can test
+  // SetRepeatedEnumValue.
+  const google::protobuf::EnumValueDescriptor* enum_value =
+      repeated_field->enum_type()->FindValueByName("BAR");
+  EXPECT_TRUE(enum_value != NULL);
+  r->AddEnum(&message, repeated_field, enum_value);
+
+  // Enum-field integer-based setters GOOGLE_DCHECK-fail on invalid values, in order to
+  // remain consistent with proto2 generated code.
+  EXPECT_DEBUG_DEATH({
+    r->SetEnumValue(&message, singular_field, 4242);
+    r->GetEnum(message, singular_field)->number();
+  }, "SetEnumValue accepts only valid integer values");
+  EXPECT_DEBUG_DEATH({
+    r->SetRepeatedEnumValue(&message, repeated_field, 0, 4242);
+    r->GetRepeatedEnum(message, repeated_field, 0);
+  }, "SetRepeatedEnumValue accepts only valid integer values");
+  EXPECT_DEBUG_DEATH({
+    r->AddEnumValue(&message, repeated_field, 4242);
+    r->GetRepeatedEnum(message, repeated_field, 1);
+  }, "AddEnumValue accepts only valid integer values");
+}
+
+TEST(PreserveUnknownEnumTest, SupportsUnknownEnumValuesAPI) {
+  protobuf_unittest::TestAllTypes proto2_message;
+  proto2_preserve_unknown_enum_unittest::MyMessage new_message;
+
+  const google::protobuf::Reflection* proto2_reflection = proto2_message.GetReflection();
+  const google::protobuf::Reflection* new_reflection = new_message.GetReflection();
+
+  EXPECT_FALSE(proto2_reflection->SupportsUnknownEnumValues());
+  EXPECT_TRUE(new_reflection->SupportsUnknownEnumValues());
+}
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/proto3_arena_unittest.cc b/src/google/protobuf/proto3_arena_unittest.cc
new file mode 100644
index 00000000..123e21ab
--- /dev/null
+++ b/src/google/protobuf/proto3_arena_unittest.cc
@@ -0,0 +1,185 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <string>
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <vector>
+
+#include <google/protobuf/test_util.h>
+#include <google/protobuf/unittest.pb.h>
+#include <google/protobuf/unittest_proto3_arena.pb.h>
+#include <google/protobuf/arena.h>
+#include <google/protobuf/testing/googletest.h>
+#include <gtest/gtest.h>
+
+namespace google {
+using proto3_arena_unittest::TestAllTypes;
+
+namespace protobuf {
+namespace {
+// We selectively set/check a few representative fields rather than all fields
+// as this test is only expected to cover the basics of arena support.
+void SetAllFields(TestAllTypes* m) {
+  m->set_optional_int32(100);
+  m->set_optional_string("asdf");
+  m->set_optional_bytes("jkl;");
+  m->mutable_optional_nested_message()->set_bb(42);
+  m->mutable_optional_foreign_message()->set_c(43);
+  m->set_optional_nested_enum(
+      proto3_arena_unittest::TestAllTypes_NestedEnum_BAZ);
+  m->set_optional_foreign_enum(
+      proto3_arena_unittest::FOREIGN_BAZ);
+  m->mutable_optional_lazy_message()->set_bb(45);
+  m->add_repeated_int32(100);
+  m->add_repeated_string("asdf");
+  m->add_repeated_bytes("jkl;");
+  m->add_repeated_nested_message()->set_bb(46);
+  m->add_repeated_foreign_message()->set_c(47);
+  m->add_repeated_nested_enum(
+      proto3_arena_unittest::TestAllTypes_NestedEnum_BAZ);
+  m->add_repeated_foreign_enum(
+      proto3_arena_unittest::FOREIGN_BAZ);
+  m->add_repeated_lazy_message()->set_bb(49);
+
+  m->set_oneof_uint32(1);
+  m->mutable_oneof_nested_message()->set_bb(50);
+  m->set_oneof_string("test");  // only this one remains set
+}
+
+void ExpectAllFieldsSet(const TestAllTypes& m) {
+  EXPECT_EQ(100, m.optional_int32());
+  EXPECT_EQ("asdf", m.optional_string());
+  EXPECT_EQ("jkl;", m.optional_bytes());
+  EXPECT_EQ(true, m.has_optional_nested_message());
+  EXPECT_EQ(42, m.optional_nested_message().bb());
+  EXPECT_EQ(true, m.has_optional_foreign_message());
+  EXPECT_EQ(43, m.optional_foreign_message().c());
+  EXPECT_EQ(proto3_arena_unittest::TestAllTypes_NestedEnum_BAZ,
+            m.optional_nested_enum());
+  EXPECT_EQ(proto3_arena_unittest::FOREIGN_BAZ,
+            m.optional_foreign_enum());
+  EXPECT_EQ(true, m.has_optional_lazy_message());
+  EXPECT_EQ(45, m.optional_lazy_message().bb());
+
+  EXPECT_EQ(1, m.repeated_int32_size());
+  EXPECT_EQ(100, m.repeated_int32(0));
+  EXPECT_EQ(1, m.repeated_string_size());
+  EXPECT_EQ("asdf", m.repeated_string(0));
+  EXPECT_EQ(1, m.repeated_bytes_size());
+  EXPECT_EQ("jkl;", m.repeated_bytes(0));
+  EXPECT_EQ(1, m.repeated_nested_message_size());
+  EXPECT_EQ(46, m.repeated_nested_message(0).bb());
+  EXPECT_EQ(1, m.repeated_foreign_message_size());
+  EXPECT_EQ(47, m.repeated_foreign_message(0).c());
+  EXPECT_EQ(1, m.repeated_nested_enum_size());
+  EXPECT_EQ(proto3_arena_unittest::TestAllTypes_NestedEnum_BAZ,
+            m.repeated_nested_enum(0));
+  EXPECT_EQ(1, m.repeated_foreign_enum_size());
+  EXPECT_EQ(proto3_arena_unittest::FOREIGN_BAZ,
+            m.repeated_foreign_enum(0));
+  EXPECT_EQ(1, m.repeated_lazy_message_size());
+  EXPECT_EQ(49, m.repeated_lazy_message(0).bb());
+
+  EXPECT_EQ(proto3_arena_unittest::TestAllTypes::kOneofString,
+            m.oneof_field_case());
+  EXPECT_EQ("test", m.oneof_string());
+}
+
+// In this file we only test some basic functionalities of arena support in
+// proto3 and expect the arena support to be fully tested in proto2 unittests
+// because proto3 shares most code with proto2.
+
+TEST(ArenaTest, Parsing) {
+  TestAllTypes original;
+  SetAllFields(&original);
+
+  Arena arena;
+  TestAllTypes* arena_message = Arena::CreateMessage<TestAllTypes>(&arena);
+  arena_message->ParseFromString(original.SerializeAsString());
+  ExpectAllFieldsSet(*arena_message);
+}
+
+TEST(ArenaTest, UnknownFields) {
+  TestAllTypes original;
+  SetAllFields(&original);
+
+  Arena arena;
+  TestAllTypes* arena_message = Arena::CreateMessage<TestAllTypes>(&arena);
+  arena_message->ParseFromString(original.SerializeAsString());
+  ExpectAllFieldsSet(*arena_message);
+
+  // In proto3 we can still get a pointer to the UnknownFieldSet through
+  // reflection API.
+  UnknownFieldSet* unknown_fields =
+      arena_message->GetReflection()->MutableUnknownFields(arena_message);
+  // We can modify this UnknownFieldSet.
+  unknown_fields->AddVarint(1, 2);
+  // But the change will never will serialized back.
+  ASSERT_EQ(original.ByteSize(), arena_message->ByteSize());
+  ASSERT_TRUE(
+      arena_message->GetReflection()->GetUnknownFields(*arena_message).empty());
+}
+
+TEST(ArenaTest, Swap) {
+  Arena arena1;
+  Arena arena2;
+
+  // Test Swap().
+  TestAllTypes* arena1_message = Arena::CreateMessage<TestAllTypes>(&arena1);
+  TestAllTypes* arena2_message = Arena::CreateMessage<TestAllTypes>(&arena2);
+  arena1_message->Swap(arena2_message);
+  EXPECT_EQ(&arena1, arena1_message->GetArena());
+  EXPECT_EQ(&arena2, arena2_message->GetArena());
+}
+
+TEST(ArenaTest, SetAllocatedMessage) {
+  Arena arena;
+  TestAllTypes *arena_message = Arena::CreateMessage<TestAllTypes>(&arena);
+  TestAllTypes::NestedMessage* nested = new TestAllTypes::NestedMessage;
+  nested->set_bb(118);
+  arena_message->set_allocated_optional_nested_message(nested);
+  EXPECT_EQ(118, arena_message->optional_nested_message().bb());
+}
+
+TEST(ArenaTest, ReleaseMessage) {
+  Arena arena;
+  TestAllTypes* arena_message = Arena::CreateMessage<TestAllTypes>(&arena);
+  arena_message->mutable_optional_nested_message()->set_bb(118);
+  scoped_ptr<TestAllTypes::NestedMessage> nested(
+      arena_message->release_optional_nested_message());
+  EXPECT_EQ(118, nested->bb());
+}
+
+}  // namespace
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/proto_cast.h b/src/google/protobuf/proto_cast.h
new file mode 100644
index 00000000..e25c219f
--- /dev/null
+++ b/src/google/protobuf/proto_cast.h
@@ -0,0 +1,58 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_PROTO_CAST_H__
+#define GOOGLE_PROTOBUF_UTIL_PROTO_CAST_H__
+
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+
+// proto_cast<> is used to simulate over-the-wire conversion of one
+// proto message into another.  This is primarily useful for unit tests
+// which validate the version-compatibility semantics of protobufs.
+// Usage is similar to C++-style typecasts:
+//
+// OldMessage old_message = /*...*/;
+// NewMessage new_message = proto_cast<NewMessage>(old_message);
+namespace google {
+template<typename NewProto,
+         typename OldProto>
+NewProto proto_cast(const OldProto& old_proto) {
+  string wire_format;
+  GOOGLE_CHECK(old_proto.SerializeToString(&wire_format));
+
+  NewProto new_proto;
+  GOOGLE_CHECK(new_proto.ParseFromString(wire_format));
+  return new_proto;
+}
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_PROTO_CAST_H__
diff --git a/src/google/protobuf/proto_cast_test.cc b/src/google/protobuf/proto_cast_test.cc
new file mode 100644
index 00000000..eb101eb6
--- /dev/null
+++ b/src/google/protobuf/proto_cast_test.cc
@@ -0,0 +1,60 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/proto_cast.h>
+
+#include <google/protobuf/util/unknown_enum_test.pb.h>
+#include <gtest/gtest.h>
+#include <google/protobuf/testing/gmock.h>
+
+namespace google {
+using google::protobuf::util::UpRevision;
+using google::protobuf::util::DownRevision;
+
+namespace {
+
+TEST(ProtoCastTest, V2KnownValue) {
+  UpRevision sender;
+  sender.set_value(UpRevision::NONDEFAULT_VALUE);
+
+  DownRevision receiver = proto_cast<DownRevision>(sender);
+  ASSERT_EQ(DownRevision::NONDEFAULT_VALUE, receiver.value());
+}
+
+TEST(ProtoCastTest, V2UnknownValue) {
+  UpRevision sender;
+  sender.set_value(UpRevision::NEW_VALUE);
+
+  DownRevision receiver = proto_cast<DownRevision>(sender);
+  ASSERT_EQ(DownRevision::DEFAULT_VALUE, receiver.value());
+}
+
+}  // namespace
+}  // namespace google
diff --git a/src/google/protobuf/reflection.h b/src/google/protobuf/reflection.h
new file mode 100644
index 00000000..17d89a18
--- /dev/null
+++ b/src/google/protobuf/reflection.h
@@ -0,0 +1,306 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This header defines the RepeatedFieldRef class template used to access
+// repeated fields with protobuf reflection API.
+#ifndef GOOGLE_PROTOBUF_REFLECTION_H__
+#define GOOGLE_PROTOBUF_REFLECTION_H__
+
+#include <google/protobuf/message.h>
+
+namespace google {
+namespace protobuf {
+namespace internal {
+template<typename T, typename Enable = void>
+struct RefTypeTraits;
+}  // namespace internal
+
+template<typename T>
+RepeatedFieldRef<T> Reflection::GetRepeatedFieldRef(
+    const Message& message, const FieldDescriptor* field) const {
+  return RepeatedFieldRef<T>(message, field);
+}
+
+template<typename T>
+MutableRepeatedFieldRef<T> Reflection::GetMutableRepeatedFieldRef(
+    Message* message, const FieldDescriptor* field) const {
+  return MutableRepeatedFieldRef<T>(message, field);
+}
+
+// RepeatedFieldRef definition for non-message types.
+template<typename T>
+class RepeatedFieldRef<
+    T, typename internal::enable_if<!internal::is_base_of<Message, T>::value>::type> {
+  typedef typename internal::RefTypeTraits<T>::iterator IteratorType;
+  typedef typename internal::RefTypeTraits<T>::AccessorType AccessorType;
+
+ public:
+  bool empty() const {
+    return accessor_->IsEmpty(data_);
+  }
+  int size() const {
+    return accessor_->Size(data_);
+  }
+  T Get(int index) const {
+    return accessor_->template Get<T>(data_, index);
+  }
+
+  typedef IteratorType iterator;
+  typedef IteratorType const_iterator;
+  iterator begin() const {
+    return iterator(data_, accessor_, true);
+  }
+  iterator end() const {
+    return iterator(data_, accessor_, false);
+  }
+
+ private:
+  friend class Reflection;
+  RepeatedFieldRef(
+      const Message& message,
+      const FieldDescriptor* field) {
+    const Reflection* reflection = message.GetReflection();
+    data_ = reflection->RepeatedFieldData(
+        const_cast<Message*>(&message), field,
+        internal::RefTypeTraits<T>::cpp_type, NULL);
+    accessor_ = reflection->RepeatedFieldAccessor(field);
+  }
+
+  const void* data_;
+  const AccessorType* accessor_;
+};
+
+// MutableRepeatedFieldRef definition for non-message types.
+template<typename T>
+class MutableRepeatedFieldRef<
+    T, typename internal::enable_if<!internal::is_base_of<Message, T>::value>::type> {
+  typedef typename internal::RefTypeTraits<T>::AccessorType AccessorType;
+
+ public:
+  bool empty() const {
+    return accessor_->IsEmpty(data_);
+  }
+  int size() const {
+    return accessor_->Size(data_);
+  }
+  T Get(int index) const {
+    return accessor_->template Get<T>(data_, index);
+  }
+
+  void Set(int index, const T& value) const {
+    accessor_->template Set<T>(data_, index, value);
+  }
+  void Add(const T& value) const {
+    accessor_->template Add<T>(data_, value);
+  }
+  void RemoveLast() const {
+    accessor_->RemoveLast(data_);
+  }
+  void SwapElements(int index1, int index2) const {
+    accessor_->SwapElements(data_, index1, index2);
+  }
+  void Clear() const {
+    accessor_->Clear(data_);
+  }
+
+  void Swap(const MutableRepeatedFieldRef& other) const {
+    accessor_->Swap(data_, other.accessor_, other.data_);
+  }
+
+  template<typename Container>
+  void MergeFrom(const Container& container) const {
+    typedef typename Container::const_iterator Iterator;
+    for (Iterator it = container.begin(); it != container.end(); ++it) {
+      Add(*it);
+    }
+  }
+  template<typename Container>
+  void CopyFrom(const Container& container) const {
+    Clear();
+    MergeFrom(container);
+  }
+
+ private:
+  friend class Reflection;
+  MutableRepeatedFieldRef(
+      Message* message,
+      const FieldDescriptor* field) {
+    const Reflection* reflection = message->GetReflection();
+    data_ = reflection->RepeatedFieldData(
+        message, field, internal::RefTypeTraits<T>::cpp_type, NULL);
+    accessor_ = reflection->RepeatedFieldAccessor(field);
+  }
+
+  void* data_;
+  const AccessorType* accessor_;
+};
+
+// RepeatedFieldRef definition for message types.
+template<typename T>
+class RepeatedFieldRef<
+    T, typename internal::enable_if<internal::is_base_of<Message, T>::value>::type> {
+  typedef typename internal::RefTypeTraits<T>::iterator IteratorType;
+  typedef typename internal::RefTypeTraits<T>::AccessorType AccessorType;
+
+ public:
+  bool empty() const {
+    return accessor_->IsEmpty(data_);
+  }
+  int size() const {
+    return accessor_->Size(data_);
+  }
+  // This method returns a reference to the underlying message object if it
+  // exists. If a message object doesn't exist (e.g., data stored in serialized
+  // form), scratch_space will be filled with the data and a reference to it
+  // will be returned.
+  //
+  // Example:
+  //   RepeatedFieldRef<Message> h = ...
+  //   unique_ptr<Message> scratch_space(h.NewMessage());
+  //   const Message& item = h.Get(index, scratch_space.get());
+  const T& Get(int index, T* scratch_space) const {
+    return *static_cast<const T*>(accessor_->Get(data_, index, scratch_space));
+  }
+  // Create a new message of the same type as the messages stored in this
+  // repeated field. Caller takes ownership of the returned object.
+  T* NewMessage() const {
+    return static_cast<T*>(default_instance_->New());
+  }
+
+  typedef IteratorType iterator;
+  typedef IteratorType const_iterator;
+  iterator begin() const {
+    return iterator(data_, accessor_, true, NewMessage());
+  }
+  iterator end() const {
+    return iterator(data_, accessor_, false, NewMessage());
+  }
+
+ private:
+  friend class Reflection;
+  RepeatedFieldRef(
+      const Message& message,
+      const FieldDescriptor* field) {
+    const Reflection* reflection = message.GetReflection();
+    data_ = reflection->RepeatedFieldData(
+        const_cast<Message*>(&message), field,
+        internal::RefTypeTraits<T>::cpp_type,
+        internal::RefTypeTraits<T>::GetMessageFieldDescriptor());
+    accessor_ = reflection->RepeatedFieldAccessor(field);
+    default_instance_ =
+        reflection->GetMessageFactory()->GetPrototype(field->message_type());
+  }
+
+  const void* data_;
+  const AccessorType* accessor_;
+  const Message* default_instance_;
+};
+
+// MutableRepeatedFieldRef definition for non-message types.
+template<typename T>
+class MutableRepeatedFieldRef<
+    T, typename internal::enable_if<internal::is_base_of<Message, T>::value>::type> {
+  typedef typename internal::RefTypeTraits<T>::AccessorType AccessorType;
+
+ public:
+  bool empty() const {
+    return accessor_->IsEmpty(data_);
+  }
+  int size() const {
+    return accessor_->Size(data_);
+  }
+  // See comments for RepeatedFieldRef<Message>::Get()
+  const T& Get(int index, T* scratch_space) const {
+    return *static_cast<const T*>(accessor_->Get(data_, index, scratch_space));
+  }
+  // Create a new message of the same type as the messages stored in this
+  // repeated field. Caller takes ownership of the returned object.
+  T* NewMessage() const {
+    return static_cast<T*>(default_instance_->New());
+  }
+
+  void Set(int index, const T& value) const {
+    accessor_->Set(data_, index, &value);
+  }
+  void Add(const T& value) const {
+    accessor_->Add(data_, &value);
+  }
+  void RemoveLast() const {
+    accessor_->RemoveLast(data_);
+  }
+  void SwapElements(int index1, int index2) const {
+    accessor_->SwapElements(data_, index1, index2);
+  }
+  void Clear() const {
+    accessor_->Clear(data_);
+  }
+
+  void Swap(const MutableRepeatedFieldRef& other) const {
+    accessor_->Swap(data_, other.accessor_, other.data_);
+  }
+
+  template<typename Container>
+  void MergeFrom(const Container& container) const {
+    typedef typename Container::const_iterator Iterator;
+    for (Iterator it = container.begin(); it != container.end(); ++it) {
+      Add(*it);
+    }
+  }
+  template<typename Container>
+  void CopyFrom(const Container& container) const {
+    Clear();
+    MergeFrom(container);
+  }
+
+ private:
+  friend class Reflection;
+  MutableRepeatedFieldRef(
+      Message* message,
+      const FieldDescriptor* field) {
+    const Reflection* reflection = message->GetReflection();
+    data_ = reflection->RepeatedFieldData(
+        message, field, internal::RefTypeTraits<T>::cpp_type,
+        internal::RefTypeTraits<T>::GetMessageFieldDescriptor());
+    accessor_ = reflection->RepeatedFieldAccessor(field);
+    default_instance_ =
+        reflection->GetMessageFactory()->GetPrototype(field->message_type());
+  }
+
+  void* data_;
+  const AccessorType* accessor_;
+  const Message* default_instance_;
+};
+}  // namespace protobuf
+}  // namespace google
+
+// Implementation details for (Mutable)RepeatedFieldRef.
+#include <google/protobuf/repeated_field_reflection.h>
+
+#endif  // GOOGLE_PROTOBUF_REFLECTION_H__
diff --git a/src/google/protobuf/reflection_internal.h b/src/google/protobuf/reflection_internal.h
new file mode 100644
index 00000000..e25e193c
--- /dev/null
+++ b/src/google/protobuf/reflection_internal.h
@@ -0,0 +1,310 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_REFLECTION_INTERNAL_H__
+#define GOOGLE_PROTOBUF_REFLECTION_INTERNAL_H__
+
+#include <google/protobuf/reflection.h>
+#include <google/protobuf/repeated_field.h>
+
+namespace google {
+namespace protobuf {
+namespace internal {
+// A base class for RepeatedFieldAccessor implementations that can support
+// random-access efficiently. All iterator methods delegates the work to
+// corresponding random-access methods.
+class RandomAccessRepeatedFieldAccessor : public RepeatedFieldAccessor {
+ public:
+  virtual ~RandomAccessRepeatedFieldAccessor() {}
+
+  virtual Iterator* BeginIterator(const Field* data) const {
+    return PositionToIterator(0);
+  }
+  virtual Iterator* EndIterator(const Field* data) const {
+    return PositionToIterator(this->Size(data));
+  }
+  virtual Iterator* CopyIterator(const Field* data,
+                                 const Iterator* iterator) const {
+    return const_cast<Iterator*>(iterator);
+  }
+  virtual Iterator* AdvanceIterator(const Field* data,
+                                    Iterator* iterator) const {
+    return PositionToIterator(IteratorToPosition(iterator) + 1);
+  }
+  virtual bool EqualsIterator(const Field* data,
+                              const Iterator* a,
+                              const Iterator* b) const {
+    return a == b;
+  }
+  virtual void DeleteIterator(const Field* data, Iterator* iterator) const {
+  }
+  virtual const Value* GetIteratorValue(const Field* data,
+                                        const Iterator* iterator,
+                                        Value* scratch_space) const {
+    return Get(data, static_cast<int>(IteratorToPosition(iterator)),
+               scratch_space);
+  }
+
+ private:
+  static intptr_t IteratorToPosition(const Iterator* iterator) {
+    return reinterpret_cast<intptr_t>(iterator);
+  }
+  static Iterator* PositionToIterator(intptr_t position) {
+    return reinterpret_cast<Iterator*>(position);
+  }
+};
+
+// Base class for RepeatedFieldAccessor implementations that manipulates
+// RepeatedField<T>.
+template<typename T>
+class RepeatedFieldWrapper : public RandomAccessRepeatedFieldAccessor {
+ public:
+  RepeatedFieldWrapper() {}
+  virtual ~RepeatedFieldWrapper() {}
+  virtual bool IsEmpty(const Field* data) const {
+    return GetRepeatedField(data)->empty();
+  }
+  virtual int Size(const Field* data) const {
+    return GetRepeatedField(data)->size();
+  }
+  virtual const Value* Get(const Field* data, int index,
+                          Value* scratch_space) const {
+    return ConvertFromT(GetRepeatedField(data)->Get(index), scratch_space);
+  }
+  virtual void Clear(Field* data) const {
+    MutableRepeatedField(data)->Clear();
+  }
+  virtual void Set(Field* data, int index, const Value* value) const {
+    MutableRepeatedField(data)->Set(index, ConvertToT(value));
+  }
+  virtual void Add(Field* data, const Value* value) const {
+    MutableRepeatedField(data)->Add(ConvertToT(value));
+  }
+  virtual void RemoveLast(Field* data) const {
+    MutableRepeatedField(data)->RemoveLast();
+  }
+  virtual void SwapElements(Field* data, int index1, int index2) const {
+    MutableRepeatedField(data)->SwapElements(index1, index2);
+  }
+
+ protected:
+  typedef RepeatedField<T> RepeatedFieldType;
+  static const RepeatedFieldType* GetRepeatedField(const Field* data) {
+    return reinterpret_cast<const RepeatedFieldType*>(data);
+  }
+  static RepeatedFieldType* MutableRepeatedField(Field* data) {
+    return reinterpret_cast<RepeatedFieldType*>(data);
+  }
+
+  // Convert an object recevied by this accessor to an object to be stored in
+  // the underlying RepeatedField.
+  virtual T ConvertToT(const Value* value) const = 0;
+
+  // Convert an object stored in RepeatedPtrField to an object that will be
+  // returned by this accessor. If the two objects have the same type (true
+  // for string fields with ctype=STRING), a pointer to the source object can
+  // be returned directly. Otherwise, data should be copied from value to
+  // scratch_space and scratch_space should be returned.
+  virtual const Value* ConvertFromT(const T& value,
+                                    Value* scratch_space) const = 0;
+};
+
+// Base class for RepeatedFieldAccessor implementations that manipulates
+// RepeatedPtrField<T>.
+template<typename T>
+class RepeatedPtrFieldWrapper : public RandomAccessRepeatedFieldAccessor {
+ public:
+  RepeatedPtrFieldWrapper() {}
+  virtual ~RepeatedPtrFieldWrapper() {}
+  virtual bool IsEmpty(const Field* data) const {
+    return GetRepeatedField(data)->empty();
+  }
+  virtual int Size(const Field* data) const {
+    return GetRepeatedField(data)->size();
+  }
+  virtual const Value* Get(const Field* data, int index,
+                           Value* scratch_space) const {
+    return ConvertFromT(GetRepeatedField(data)->Get(index), scratch_space);
+  }
+  virtual void Clear(Field* data) const {
+    MutableRepeatedField(data)->Clear();
+  }
+  virtual void Set(Field* data, int index, const Value* value) const {
+    ConvertToT(value, MutableRepeatedField(data)->Mutable(index));
+  }
+  virtual void Add(Field* data, const Value* value) const {
+    T* allocated = New(value);
+    ConvertToT(value, allocated);
+    MutableRepeatedField(data)->AddAllocated(allocated);
+  }
+  virtual void RemoveLast(Field* data) const {
+    MutableRepeatedField(data)->RemoveLast();
+  }
+  virtual void SwapElements(Field* data, int index1, int index2) const {
+    MutableRepeatedField(data)->SwapElements(index1, index2);
+  }
+
+ protected:
+  typedef RepeatedPtrField<T> RepeatedFieldType;
+  static const RepeatedFieldType* GetRepeatedField(const Field* data) {
+    return reinterpret_cast<const RepeatedFieldType*>(data);
+  }
+  static RepeatedFieldType* MutableRepeatedField(Field* data) {
+    return reinterpret_cast<RepeatedFieldType*>(data);
+  }
+
+  // Create a new T instance. For repeated message fields, T can be specified
+  // as google::protobuf::Message so we can't use "new T()" directly. In that case, value
+  // should be a message of the same type (it's ensured by the caller) and a
+  // new message object will be created using it.
+  virtual T* New(const Value* value) const = 0;
+
+  // Convert an object received by this accessor to an object that will be
+  // stored in the underlying RepeatedPtrField.
+  virtual void ConvertToT(const Value* value, T* result) const = 0;
+
+  // Convert an object stored in RepeatedPtrField to an object that will be
+  // returned by this accessor. If the two objects have the same type (true
+  // for string fields with ctype=STRING), a pointer to the source object can
+  // be returned directly. Otherwise, data should be copied from value to
+  // scratch_space and scratch_space should be returned.
+  virtual const Value* ConvertFromT(const T& value,
+                                    Value* scratch_space) const = 0;
+};
+
+// Default implementations of RepeatedFieldAccessor for primitive types.
+template<typename T>
+class RepeatedFieldPrimitiveAccessor : public RepeatedFieldWrapper<T> {
+  typedef void Field;
+  typedef void Value;
+  using RepeatedFieldWrapper<T>::MutableRepeatedField;
+
+ public:
+  RepeatedFieldPrimitiveAccessor() {}
+  virtual ~RepeatedFieldPrimitiveAccessor() {}
+  virtual void Swap(
+      Field* data,
+      const internal::RepeatedFieldAccessor* other_mutator,
+      Field* other_data) const {
+    // Currently RepeatedFieldPrimitiveAccessor is the only implementation of
+    // RepeatedFieldAccessor for primitive types. As we are using singletons
+    // for these accessors, here "other_mutator" must be "this".
+    GOOGLE_CHECK(this == other_mutator);
+    MutableRepeatedField(data)->Swap(MutableRepeatedField(other_data));
+  }
+
+ protected:
+  virtual T ConvertToT(const Value* value) const {
+    return *static_cast<const T*>(value);
+  }
+  virtual const Value* ConvertFromT(const T& value,
+                                    Value* scratch_space) const {
+    return static_cast<const Value*>(&value);
+  }
+};
+
+// Default implementation of RepeatedFieldAccessor for string fields with
+// ctype=STRING.
+class RepeatedPtrFieldStringAccessor : public RepeatedPtrFieldWrapper<string> {
+  typedef void Field;
+  typedef void Value;
+  using RepeatedFieldAccessor::Add;
+
+ public:
+  RepeatedPtrFieldStringAccessor() {}
+  virtual ~RepeatedPtrFieldStringAccessor() {}
+  virtual void Swap(
+      Field* data,
+      const internal::RepeatedFieldAccessor* other_mutator,
+      Field* other_data) const {
+    if (this == other_mutator) {
+      MutableRepeatedField(data)->Swap(MutableRepeatedField(other_data));
+    } else {
+      RepeatedPtrField<string> tmp;
+      tmp.Swap(MutableRepeatedField(data));
+      int other_size = other_mutator->Size(other_data);
+      for (int i = 0; i < other_size; ++i) {
+        Add<string>(data, other_mutator->Get<string>(other_data, i));
+      }
+      int size = Size(data);
+      other_mutator->Clear(other_data);
+      for (int i = 0; i < size; ++i) {
+        other_mutator->Add<string>(other_data, tmp.Get(i));
+      }
+    }
+  }
+
+ protected:
+  virtual string* New(const Value*) const {
+    return new string();
+  }
+  virtual void ConvertToT(const Value* value, string* result) const {
+    *result = *static_cast<const string*>(value);
+  }
+  virtual const Value* ConvertFromT(const string& value,
+                                    Value* scratch_space) const {
+    return static_cast<const Value*>(&value);
+  }
+};
+
+
+class RepeatedPtrFieldMessageAccessor
+    : public RepeatedPtrFieldWrapper<Message> {
+  typedef void Field;
+  typedef void Value;
+
+ public:
+  RepeatedPtrFieldMessageAccessor() {}
+  virtual ~RepeatedPtrFieldMessageAccessor() {}
+  virtual void Swap(
+      Field* data,
+      const internal::RepeatedFieldAccessor* other_mutator,
+      Field* other_data) const {
+    GOOGLE_CHECK(this == other_mutator);
+    MutableRepeatedField(data)->Swap(MutableRepeatedField(other_data));
+  }
+
+ protected:
+  virtual Message* New(const Value* value) const {
+    return static_cast<const Message*>(value)->New();
+  }
+  virtual void ConvertToT(const Value* value, Message* result) const {
+    result->CopyFrom(*static_cast<const Message*>(value));
+  }
+  virtual const Value* ConvertFromT(const Message& value,
+                                    Value* scratch_space) const {
+    return static_cast<const Value*>(&value);
+  }
+};
+}  // namespace internal
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_REFLECTION_INTERNAL_H__
diff --git a/src/google/protobuf/repeated_field.cc b/src/google/protobuf/repeated_field.cc
index b400732f..e5aedadc 100644
--- a/src/google/protobuf/repeated_field.cc
+++ b/src/google/protobuf/repeated_field.cc
@@ -42,42 +42,52 @@ namespace protobuf {
 
 namespace internal {
 
-void RepeatedPtrFieldBase::Reserve(int new_size) {
-  if (total_size_ >= new_size) return;
-
-  void** old_elements = elements_;
-  total_size_ = max(kMinRepeatedFieldAllocationSize,
-                    max(total_size_ * 2, new_size));
-  elements_ = new void*[total_size_];
-  if (old_elements != NULL) {
-    memcpy(elements_, old_elements, allocated_size_ * sizeof(elements_[0]));
-    delete [] old_elements;
+void** RepeatedPtrFieldBase::InternalExtend(int extend_amount) {
+  int new_size = current_size_ + extend_amount;
+  if (total_size_ >= new_size) {
+    // N.B.: rep_ is non-NULL because extend_amount is always > 0, hence
+    // total_size must be non-zero since it is lower-bounded by new_size.
+    return &rep_->elements[current_size_];
+  }
+  Rep* old_rep = rep_;
+  Arena* arena = GetArenaNoVirtual();
+  new_size = max(kMinRepeatedFieldAllocationSize,
+                 max(total_size_ * 2, new_size));
+  if (arena == NULL) {
+    rep_ = reinterpret_cast<Rep*>(
+        new char[kRepHeaderSize + sizeof(old_rep->elements[0])*new_size]);
+  } else {
+    rep_ = reinterpret_cast<Rep*>(
+        ::google::protobuf::Arena::CreateArray<char>(arena,
+            kRepHeaderSize + sizeof(old_rep->elements[0])*new_size));
+  }
+  total_size_ = new_size;
+  if (old_rep && old_rep->allocated_size > 0) {
+    memcpy(rep_->elements, old_rep->elements,
+           old_rep->allocated_size * sizeof(rep_->elements[0]));
+    rep_->allocated_size = old_rep->allocated_size;
+  } else {
+    rep_->allocated_size = 0;
+  }
+  if (arena == NULL) {
+    delete [] reinterpret_cast<char*>(old_rep);
   }
+  return &rep_->elements[current_size_];
 }
 
-void RepeatedPtrFieldBase::Swap(RepeatedPtrFieldBase* other) {
-  if (this == other) return;
-  void** swap_elements       = elements_;
-  int    swap_current_size   = current_size_;
-  int    swap_allocated_size = allocated_size_;
-  int    swap_total_size     = total_size_;
-
-  elements_       = other->elements_;
-  current_size_   = other->current_size_;
-  allocated_size_ = other->allocated_size_;
-  total_size_     = other->total_size_;
-
-  other->elements_       = swap_elements;
-  other->current_size_   = swap_current_size;
-  other->allocated_size_ = swap_allocated_size;
-  other->total_size_     = swap_total_size;
+void RepeatedPtrFieldBase::Reserve(int new_size) {
+  if (new_size > current_size_) {
+    InternalExtend(new_size - current_size_);
+  }
 }
 
-string* StringTypeHandlerBase::New() {
-  return new string;
-}
-void StringTypeHandlerBase::Delete(string* value) {
-  delete value;
+void RepeatedPtrFieldBase::CloseGap(int start, int num) {
+  if (rep_ == NULL) return;
+  // Close up a gap of "num" elements starting at offset "start".
+  for (int i = start + num; i < rep_->allocated_size; ++i)
+    rep_->elements[i - num] = rep_->elements[i];
+  current_size_ -= num;
+  rep_->allocated_size -= num;
 }
 
 }  // namespace internal
diff --git a/src/google/protobuf/repeated_field.h b/src/google/protobuf/repeated_field.h
index 816ea684..c21ba97f 100644
--- a/src/google/protobuf/repeated_field.h
+++ b/src/google/protobuf/repeated_field.h
@@ -53,8 +53,10 @@
 
 #include <string>
 #include <iterator>
+#include <google/protobuf/stubs/casts.h>
 #include <google/protobuf/stubs/common.h>
 #include <google/protobuf/stubs/type_traits.h>
+#include <google/protobuf/arena.h>
 #include <google/protobuf/generated_message_util.h>
 #include <google/protobuf/message_lite.h>
 
@@ -104,6 +106,7 @@ template <typename Element>
 class RepeatedField {
  public:
   RepeatedField();
+  explicit RepeatedField(Arena* arena);
   RepeatedField(const RepeatedField& other);
   template <typename Iter>
   RepeatedField(Iter begin, const Iter& end);
@@ -153,9 +156,16 @@ class RepeatedField {
   Element* mutable_data();
   const Element* data() const;
 
-  // Swap entire contents with "other".
+  // Swap entire contents with "other". If they are separate arenas then, copies
+  // data between each other.
   void Swap(RepeatedField* other);
 
+  // Swap entire contents with "other". Should be called only if the caller can
+  // guarantee that both repeated fields are on the same arena or are on the
+  // heap. Swapping between different arenas is disallowed and caught by a
+  // GOOGLE_DCHECK (see API docs for details).
+  void UnsafeArenaSwap(RepeatedField* other);
+
   // Swap two elements.
   void SwapElements(int index1, int index2);
 
@@ -172,8 +182,10 @@ class RepeatedField {
 
   iterator begin();
   const_iterator begin() const;
+  const_iterator cbegin() const;
   iterator end();
   const_iterator end() const;
+  const_iterator cend() const;
 
   // Reverse iterator support
   typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
@@ -195,20 +207,60 @@ class RepeatedField {
   // sizeof(*this)
   int SpaceUsedExcludingSelf() const;
 
+  // Remove the element referenced by position.
+  iterator erase(const_iterator position);
+
+  // Remove the elements in the range [first, last).
+  iterator erase(const_iterator first, const_iterator last);
+
+  // Get the Arena on which this RepeatedField stores its elements.
+  ::google::protobuf::Arena* GetArena() const {
+    return GetArenaNoVirtual();
+  }
+
  private:
   static const int kInitialSize = 0;
-
-  Element* elements_;
-  int      current_size_;
-  int      total_size_;
+  // A note on the representation here (see also comment below for
+  // RepeatedPtrFieldBase's struct Rep):
+  //
+  // We maintain the same sizeof(RepeatedField) as before we added arena support
+  // so that we do not degrade performance by bloating memory usage. Directly
+  // adding an arena_ element to RepeatedField is quite costly. By using
+  // indirection in this way, we keep the same size when the RepeatedField is
+  // empty (common case), and add only an 8-byte header to the elements array
+  // when non-empty. We make sure to place the size fields directly in the
+  // RepeatedField class to avoid costly cache misses due to the indirection.
+  int current_size_;
+  int total_size_;
+  struct Rep {
+    Arena* arena;
+    Element  elements[1];
+  };
+  // Why not sizeof(Rep) - sizeof(Element)? Because this is not accurate w.r.t.
+  // trailing padding on the struct -- e.g. if Element is int, this would yield
+  // 12 on x86-64, not 8 as we want.
+  static const size_t kRepHeaderSize = sizeof(Arena*);
+  // Contains arena ptr and the elements array. We also keep the invariant that
+  // if rep_ is NULL, then arena is NULL.
+  Rep* rep_;
+
+  friend class Arena;
+  typedef void InternalArenaConstructable_;
 
   // Move the contents of |from| into |to|, possibly clobbering |from| in the
   // process.  For primitive types this is just a memcpy(), but it could be
   // specialized for non-primitive types to, say, swap each element instead.
-  void MoveArray(Element to[], Element from[], int size);
+  void MoveArray(Element* to, Element* from, int size);
 
   // Copy the elements of |from| into |to|.
-  void CopyArray(Element to[], const Element from[], int size);
+  void CopyArray(Element* to, const Element* from, int size);
+
+  inline void InternalSwap(RepeatedField* other);
+
+  // Internal helper expected by Arena methods.
+  inline Arena* GetArenaNoVirtual() const {
+    return (rep_ == NULL) ? NULL : rep_->arena;
+  }
 };
 
 namespace internal {
@@ -225,13 +277,48 @@ namespace internal {
 template <typename Element,
           bool HasTrivialCopy = has_trivial_copy<Element>::value>
 struct ElementCopier {
-  void operator()(Element to[], const Element from[], int array_size);
+  void operator()(Element* to, const Element* from, int array_size);
 };
 
 }  // namespace internal
 
 namespace internal {
 
+// type-traits helper for RepeatedPtrFieldBase: we only want to invoke
+// arena-related "copy if on different arena" behavior if the necessary methods
+// exist on the contained type. In particular, we rely on MergeFrom() existing
+// as a general proxy for the fact that a copy will work, and we also provide a
+// specific override for string*.
+template<typename T>
+struct TypeImplementsMergeBehavior {
+  typedef char HasMerge;
+  typedef long HasNoMerge;
+
+  // We accept either of:
+  // - void MergeFrom(const T& other)
+  // - bool MergeFrom(const T& other)
+  //
+  // We mangle these names a bit to avoid compatibility issues in 'unclean'
+  // include environments that may have, e.g., "#define test ..." (yes, this
+  // exists).
+  template<typename U, typename RetType, RetType (U::*)(const U& arg)>
+      struct CheckType;
+  template<typename U> static HasMerge Check(
+      CheckType<U, void, &U::MergeFrom>*);
+  template<typename U> static HasMerge Check(
+      CheckType<U, bool, &U::MergeFrom>*);
+  template<typename U> static HasNoMerge Check(...);
+
+  // Resovles to either google::protobuf::internal::true_type or google::protobuf::internal::false_type.
+  typedef google::protobuf::internal::integral_constant<bool,
+               (sizeof(Check<T>(0)) == sizeof(HasMerge))> type;
+};
+
+template<>
+struct TypeImplementsMergeBehavior< ::std::string > {
+  typedef google::protobuf::internal::true_type type;
+};
+
 // This is the common base class for RepeatedPtrFields.  It deals only in void*
 // pointers.  Users should not use this interface directly.
 //
@@ -267,6 +354,8 @@ class LIBPROTOBUF_EXPORT RepeatedPtrFieldBase {
   friend class LIBPROTOBUF_EXPORT upb::google_opensource::GMR_Handlers;
 
   RepeatedPtrFieldBase();
+  explicit RepeatedPtrFieldBase(::google::protobuf::Arena* arena);
+  ~RepeatedPtrFieldBase() {}
 
   // Must be called from destructor.
   template <typename TypeHandler>
@@ -280,7 +369,10 @@ class LIBPROTOBUF_EXPORT RepeatedPtrFieldBase {
   template <typename TypeHandler>
   typename TypeHandler::Type* Mutable(int index);
   template <typename TypeHandler>
-  typename TypeHandler::Type* Add();
+  void Delete(int index);
+  template <typename TypeHandler>
+  typename TypeHandler::Type* Add(typename TypeHandler::Type* prototype = NULL);
+
   template <typename TypeHandler>
   void RemoveLast();
   template <typename TypeHandler>
@@ -290,13 +382,7 @@ class LIBPROTOBUF_EXPORT RepeatedPtrFieldBase {
   template <typename TypeHandler>
   void CopyFrom(const RepeatedPtrFieldBase& other);
 
-  void CloseGap(int start, int num) {
-    // Close up a gap of "num" elements starting at offset "start".
-    for (int i = start + num; i < allocated_size_; ++i)
-      elements_[i - num] = elements_[i];
-    current_size_ -= num;
-    allocated_size_ -= num;
-  }
+  void CloseGap(int start, int num);
 
   void Reserve(int new_size);
 
@@ -311,7 +397,8 @@ class LIBPROTOBUF_EXPORT RepeatedPtrFieldBase {
   template <typename TypeHandler>
   const typename TypeHandler::Type* const* data() const;
 
-  void Swap(RepeatedPtrFieldBase* other);
+  template <typename TypeHandler>
+  inline void Swap(RepeatedPtrFieldBase* other) GOOGLE_ATTRIBUTE_ALWAYS_INLINE;
 
   void SwapElements(int index1, int index2);
 
@@ -325,10 +412,25 @@ class LIBPROTOBUF_EXPORT RepeatedPtrFieldBase {
   template <typename TypeHandler>
   typename TypeHandler::Type* AddFromCleared();
 
+  template<typename TypeHandler>
+  void AddAllocated(typename TypeHandler::Type* value) {
+    typename TypeImplementsMergeBehavior<typename TypeHandler::Type>::type t;
+    AddAllocatedInternal<TypeHandler>(value, t);
+  }
+
   template <typename TypeHandler>
-  void AddAllocated(typename TypeHandler::Type* value);
+  void UnsafeArenaAddAllocated(typename TypeHandler::Type* value);
+
   template <typename TypeHandler>
-  typename TypeHandler::Type* ReleaseLast();
+  typename TypeHandler::Type* ReleaseLast() {
+    typename TypeImplementsMergeBehavior<typename TypeHandler::Type>::type t;
+    return ReleaseLastInternal<TypeHandler>(t);
+  }
+
+  // Releases last element and returns it, but does not do out-of-arena copy.
+  // And just returns the raw pointer to the contained element in the arena.
+  template <typename TypeHandler>
+  typename TypeHandler::Type* UnsafeArenaReleaseLast();
 
   int ClearedCount() const;
   template <typename TypeHandler>
@@ -336,13 +438,61 @@ class LIBPROTOBUF_EXPORT RepeatedPtrFieldBase {
   template <typename TypeHandler>
   typename TypeHandler::Type* ReleaseCleared();
 
+ protected:
+  inline void InternalSwap(RepeatedPtrFieldBase* other);
+
+  template <typename TypeHandler>
+  void AddAllocatedInternal(typename TypeHandler::Type* value,
+                            google::protobuf::internal::true_type);
+  template <typename TypeHandler>
+  void AddAllocatedInternal(typename TypeHandler::Type* value,
+                            google::protobuf::internal::false_type);
+
+  template <typename TypeHandler>
+  void AddAllocatedSlowWithCopy(typename TypeHandler::Type* value,
+                                Arena* value_arena,
+                                Arena* my_arena)
+      GOOGLE_ATTRIBUTE_NOINLINE;
+  template <typename TypeHandler>
+  void AddAllocatedSlowWithoutCopy(typename TypeHandler::Type* value)
+      GOOGLE_ATTRIBUTE_NOINLINE;
+
+  template <typename TypeHandler>
+  typename TypeHandler::Type* ReleaseLastInternal(google::protobuf::internal::true_type);
+  template <typename TypeHandler>
+  typename TypeHandler::Type* ReleaseLastInternal(google::protobuf::internal::false_type);
+
+  template<typename TypeHandler>
+  inline void SwapFallback(RepeatedPtrFieldBase* other) GOOGLE_ATTRIBUTE_NOINLINE;
+
+  inline Arena* GetArenaNoVirtual() const {
+    return arena_;
+  }
+
  private:
   static const int kInitialSize = 0;
-
-  void** elements_;
+  // A few notes on internal representation:
+  //
+  // We use an indirected approach, with struct Rep, to keep
+  // sizeof(RepeatedPtrFieldBase) equivalent to what it was before arena support
+  // was added, namely, 3 8-byte machine words on x86-64. An instance of Rep is
+  // allocated only when the repeated field is non-empty, and it is a
+  // dynamically-sized struct (the header is directly followed by elements[]).
+  // We place arena_ and current_size_ directly in the object to avoid cache
+  // misses due to the indirection, because these fields are checked frequently.
+  // Placing all fields directly in the RepeatedPtrFieldBase instance costs
+  // significant performance for memory-sensitive workloads.
+  Arena* arena_;
   int    current_size_;
-  int    allocated_size_;
   int    total_size_;
+  struct Rep {
+    int    allocated_size;
+    void*  elements[1];
+  };
+  static const size_t kRepHeaderSize = sizeof(Rep) - sizeof(void*);
+  // Contains arena ptr and the elements array. We also keep the invariant that
+  // if rep_ is NULL, then arena is NULL.
+  Rep* rep_;
 
   template <typename TypeHandler>
   static inline typename TypeHandler::Type* cast(void* element) {
@@ -353,6 +503,22 @@ class LIBPROTOBUF_EXPORT RepeatedPtrFieldBase {
     return reinterpret_cast<const typename TypeHandler::Type*>(element);
   }
 
+  // Non-templated inner function to avoid code duplication. Takes a function
+  // pointer to the type-specific (templated) inner allocate/merge loop.
+  void MergeFromInternal(
+      const RepeatedPtrFieldBase& other,
+      void (RepeatedPtrFieldBase::*inner_loop)(void**, void**, int, int));
+
+  template<typename TypeHandler>
+  void MergeFromInnerLoop(
+      void** our_elems, void** other_elems, int length, int already_allocated);
+
+  // Internal helper: extend array space if necessary to contain |extend_amount|
+  // more elements, and return a pointer to the element immediately following
+  // the old list of elements.  This interface factors out common behavior from
+  // Reserve() and MergeFrom() to reduce code size. |extend_amount| must be > 0.
+  void** InternalExtend(int extend_amount);
+
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(RepeatedPtrFieldBase);
 };
 
@@ -360,22 +526,98 @@ template <typename GenericType>
 class GenericTypeHandler {
  public:
   typedef GenericType Type;
-  static GenericType* New() { return new GenericType; }
-  static void Delete(GenericType* value) { delete value; }
-  static void Clear(GenericType* value) { value->Clear(); }
-  static void Merge(const GenericType& from, GenericType* to) {
+  static inline GenericType* New(Arena* arena) {
+    return ::google::protobuf::Arena::CreateMaybeMessage<Type>(
+        arena, static_cast<GenericType*>(0));
+  }
+  // We force NewFromPrototype() and Delete() to be non-inline to reduce code
+  // size: else, several other methods get inlined copies of message types'
+  // constructors and destructors. Note that the GOOGLE_ATTRIBUTE_NOINLINE macro
+  // requires the 'inline' storage class here, which is somewhat confusing, but
+  // the compiler does the right thing.
+  static inline GenericType* NewFromPrototype(const GenericType* prototype,
+                                              ::google::protobuf::Arena* arena = NULL)
+    GOOGLE_ATTRIBUTE_NOINLINE {
+    return New(arena);
+  }
+  static inline void Delete(GenericType* value, Arena* arena)
+    GOOGLE_ATTRIBUTE_NOINLINE {
+    if (arena == NULL) {
+      delete value;
+    }
+  }
+  static inline ::google::protobuf::Arena* GetArena(GenericType* value) {
+    return ::google::protobuf::Arena::GetArena<Type>(value);
+  }
+  static inline void* GetMaybeArenaPointer(GenericType* value) {
+    return ::google::protobuf::Arena::GetArena<Type>(value);
+  }
+
+  static inline void Clear(GenericType* value) { value->Clear(); }
+  static inline void Merge(const GenericType& from, GenericType* to)
+      GOOGLE_ATTRIBUTE_NOINLINE {
     to->MergeFrom(from);
   }
-  static int SpaceUsed(const GenericType& value) { return value.SpaceUsed(); }
-  static const Type& default_instance() { return Type::default_instance(); }
+  static inline int SpaceUsed(const GenericType& value) {
+    return value.SpaceUsed();
+  }
+  static inline const Type& default_instance() {
+    return Type::default_instance();
+  }
 };
 
+// Macros for specializing GenericTypeHandler for base proto types, these are
+// are defined here, to allow inlining them at their callsites.
+#define DEFINE_SPECIALIZATIONS_FOR_BASE_PROTO_TYPES(Inline, TypeName)          \
+    template<> \
+    Inline TypeName* GenericTypeHandler<TypeName>::NewFromPrototype(           \
+        const TypeName* prototype, google::protobuf::Arena* arena) {                     \
+      return prototype->New(arena);                                            \
+    }                                                                          \
+    template<> \
+    Inline google::protobuf::Arena* GenericTypeHandler<TypeName>::GetArena(              \
+        TypeName* value) {                                                     \
+      return value->GetArena();                                                \
+    }                                                                          \
+    template<>                                                                 \
+    Inline void* GenericTypeHandler<TypeName>::GetMaybeArenaPointer(           \
+        TypeName* value) {                                                     \
+      return value->GetMaybeArenaPointer();                                    \
+    }
+#define DEFINE_SPECIALIZATIONS_FOR_BASE_PROTO_TYPES_NOINLINE(TypeName)         \
+    DEFINE_SPECIALIZATIONS_FOR_BASE_PROTO_TYPES(, TypeName)
+
+// Implements GenericTypeHandler specialization required by RepeatedPtrFields
+// to work with MessageLite type.
 template <>
 inline void GenericTypeHandler<MessageLite>::Merge(
     const MessageLite& from, MessageLite* to) {
   to->CheckTypeAndMergeFrom(from);
 }
 
+DEFINE_SPECIALIZATIONS_FOR_BASE_PROTO_TYPES(inline, MessageLite);
+
+// Declarations of the specialization as we cannot define them here, as the
+// header that defines ProtocolMessage depends on types defined in this header.
+#define DECLARE_SPECIALIZATIONS_FOR_BASE_PROTO_TYPES(TypeName)                 \
+    template<>                                                                 \
+    TypeName* GenericTypeHandler<TypeName>::NewFromPrototype(                  \
+        const TypeName* prototype, google::protobuf::Arena* arena);                      \
+    template<>                                                                 \
+    google::protobuf::Arena* GenericTypeHandler<TypeName>::GetArena(                     \
+        TypeName* value);                                                      \
+    template<>                                                                 \
+    void* GenericTypeHandler<TypeName>::GetMaybeArenaPointer(                  \
+        TypeName* value);
+
+// Message specialization bodies defined in message.cc. This split is necessary
+// to allow proto2-lite (which includes this header) to be independent of
+// Message.
+DECLARE_SPECIALIZATIONS_FOR_BASE_PROTO_TYPES(Message);
+
+
+#undef DECLARE_SPECIALIZATIONS_FOR_BASE_CLASSES
+
 template <>
 inline const MessageLite& GenericTypeHandler<MessageLite>::default_instance() {
   // Yes, the behavior of the code is undefined, but this function is only
@@ -406,11 +648,28 @@ inline const Message& GenericTypeHandler<Message>::default_instance() {
 class LIBPROTOBUF_EXPORT StringTypeHandlerBase {
  public:
   typedef string Type;
-  static string* New();
-  static void Delete(string* value);
-  static void Clear(string* value) { value->clear(); }
-  static void Merge(const string& from, string* to) { *to = from; }
-  static const Type& default_instance() {
+
+  static inline string* New(Arena* arena) {
+    return Arena::Create<string>(arena);
+  }
+  static inline string* NewFromPrototype(const string*,
+                                         ::google::protobuf::Arena* arena) {
+    return New(arena);
+  }
+  static inline ::google::protobuf::Arena* GetArena(string*) {
+    return NULL;
+  }
+  static inline void* GetMaybeArenaPointer(string* value) {
+    return NULL;
+  }
+  static inline void Delete(string* value, Arena* arena) {
+    if (arena == NULL) {
+      delete value;
+    }
+  }
+  static inline void Clear(string* value) { value->clear(); }
+  static inline void Merge(const string& from, string* to) { *to = from; }
+  static inline const Type& default_instance() {
     return ::google::protobuf::internal::GetEmptyString();
   }
 };
@@ -431,6 +690,8 @@ template <typename Element>
 class RepeatedPtrField : public internal::RepeatedPtrFieldBase {
  public:
   RepeatedPtrField();
+  explicit RepeatedPtrField(::google::protobuf::Arena* arena);
+
   RepeatedPtrField(const RepeatedPtrField& other);
   template <typename Iter>
   RepeatedPtrField(Iter begin, const Iter& end);
@@ -470,9 +731,16 @@ class RepeatedPtrField : public internal::RepeatedPtrFieldBase {
   Element** mutable_data();
   const Element* const* data() const;
 
-  // Swap entire contents with "other".
+  // Swap entire contents with "other". If they are on separate arenas, then
+  // copies data.
   void Swap(RepeatedPtrField* other);
 
+  // Swap entire contents with "other". Caller should guarantee that either both
+  // fields are on the same arena or both are on the heap. Swapping between
+  // different arenas with this function is disallowed and is caught via
+  // GOOGLE_DCHECK.
+  void UnsafeArenaSwap(RepeatedPtrField* other);
+
   // Swap two elements.
   void SwapElements(int index1, int index2);
 
@@ -489,8 +757,10 @@ class RepeatedPtrField : public internal::RepeatedPtrFieldBase {
 
   iterator begin();
   const_iterator begin() const;
+  const_iterator cbegin() const;
   iterator end();
   const_iterator end() const;
+  const_iterator cend() const;
 
   // Reverse iterator support
   typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
@@ -529,11 +799,36 @@ class RepeatedPtrField : public internal::RepeatedPtrFieldBase {
 
   // Add an already-allocated object, passing ownership to the
   // RepeatedPtrField.
+  //
+  // Note that some special behavior occurs with respect to arenas:
+  //
+  //   (i) if this field holds submessages, the new submessage will be copied if
+  //   the original is in an arena and this RepeatedPtrField is either in a
+  //   different arena, or on the heap.
+  //   (ii) if this field holds strings, the passed-in string *must* be
+  //   heap-allocated, not arena-allocated. There is no way to dynamically check
+  //   this at runtime, so User Beware.
   void AddAllocated(Element* value);
+
   // Remove the last element and return it, passing ownership to the caller.
   // Requires:  size() > 0
+  //
+  // If this RepeatedPtrField is on an arena, an object copy is required to pass
+  // ownership back to the user (for compatible semantics). Use
+  // UnsafeArenaReleaseLast() if this behavior is undesired.
   Element* ReleaseLast();
 
+  // Add an already-allocated object, skipping arena-ownership checks. The user
+  // must guarantee that the given object is in the same arena as this
+  // RepeatedPtrField.
+  void UnsafeArenaAddAllocated(Element* value);
+
+  // Remove the last element and return it.  Works only when operating on an
+  // arena. The returned pointer is to the original object in the arena, hence
+  // has the arena's lifetime.
+  // Requires:  current_size_ > 0
+  Element* UnsafeArenaReleaseLast();
+
   // Extract elements with indices in the range "[start .. start+num-1]".
   // The caller assumes ownership of the extracted elements and is responsible
   // for deleting them when they are no longer needed.
@@ -543,8 +838,20 @@ class RepeatedPtrField : public internal::RepeatedPtrFieldBase {
   // to perform any further operations (like deletion) on these elements.
   // Caution: implementation also moves elements with indices [start+num ..].
   // Calling this routine inside a loop can cause quadratic behavior.
+  //
+  // Memory copying behavior is identical to ReleaseLast(), described above: if
+  // this RepeatedPtrField is on an arena, an object copy is performed for each
+  // returned element, so that all returned element pointers are to
+  // heap-allocated copies. If this copy is not desired, the user should call
+  // UnsafeArenaExtractSubrange().
   void ExtractSubrange(int start, int num, Element** elements);
 
+  // Identical to ExtractSubrange() described above, except that when this
+  // repeated field is on an arena, no object copies are performed. Instead, the
+  // raw object pointers are returned. Thus, if on an arena, the returned
+  // objects must not be freed, because they will not be heap-allocated objects.
+  void UnsafeArenaExtractSubrange(int start, int num, Element** elements);
+
   // When elements are removed by calls to RemoveLast() or Clear(), they
   // are not actually freed.  Instead, they are cleared and kept so that
   // they can be reused later.  This can save lots of CPU time when
@@ -559,12 +866,30 @@ class RepeatedPtrField : public internal::RepeatedPtrFieldBase {
   // Add an element to the pool of cleared objects, passing ownership to
   // the RepeatedPtrField.  The element must be cleared prior to calling
   // this method.
+  //
+  // This method cannot be called when the repeated field is on an arena or when
+  // |value| is; both cases will trigger a GOOGLE_DCHECK-failure.
   void AddCleared(Element* value);
   // Remove a single element from the cleared pool and return it, passing
   // ownership to the caller.  The element is guaranteed to be cleared.
   // Requires:  ClearedCount() > 0
+  //
+  //
+  // This method cannot be called when the repeated field is on an arena; doing
+  // so will trigger a GOOGLE_DCHECK-failure.
   Element* ReleaseCleared();
 
+  // Remove the element referenced by position.
+  iterator erase(const_iterator position);
+
+  // Removes the elements in the range [first, last).
+  iterator erase(const_iterator first, const_iterator last);
+
+  // Gets the arena on which this RepeatedPtrField stores its elements.
+  ::google::protobuf::Arena* GetArena() const {
+    return GetArenaNoVirtual();
+  }
+
  protected:
   // Note:  RepeatedPtrField SHOULD NOT be subclassed by users.  We only
   //   subclass it in one place as a hack for compatibility with proto1.  The
@@ -572,31 +897,61 @@ class RepeatedPtrField : public internal::RepeatedPtrFieldBase {
   //   methods on RepeatedPtrFieldBase.
   class TypeHandler;
 
+  // Internal arena accessor expected by helpers in Arena.
+  inline Arena* GetArenaNoVirtual() const;
+
+ private:
+  // Implementations for ExtractSubrange(). The copying behavior must be
+  // included only if the type supports the necessary operations (e.g.,
+  // MergeFrom()), so we must resolve this at compile time. ExtractSubrange()
+  // uses SFINAE to choose one of the below implementations.
+  void ExtractSubrangeInternal(int start, int num, Element** elements,
+                               google::protobuf::internal::true_type);
+  void ExtractSubrangeInternal(int start, int num, Element** elements,
+                               google::protobuf::internal::false_type);
+
+  friend class Arena;
+  typedef void InternalArenaConstructable_;
+
 };
 
 // implementation ====================================================
 
 template <typename Element>
 inline RepeatedField<Element>::RepeatedField()
-  : elements_(NULL),
-    current_size_(0),
-    total_size_(kInitialSize) {
+  : current_size_(0),
+    total_size_(0),
+    rep_(NULL) {
+}
+
+template <typename Element>
+inline RepeatedField<Element>::RepeatedField(Arena* arena)
+  : current_size_(0),
+    total_size_(0),
+    rep_(NULL) {
+ // In case arena is NULL, then we do not create rep_, as code has an invariant
+ // `rep_ == NULL then arena == NULL`.
+ if (arena != NULL) {
+  rep_ = reinterpret_cast<Rep*>(
+      ::google::protobuf::Arena::CreateArray<char>(arena, kRepHeaderSize));
+  rep_->arena = arena;
+ }
 }
 
 template <typename Element>
 inline RepeatedField<Element>::RepeatedField(const RepeatedField& other)
-  : elements_(NULL),
-    current_size_(0),
-    total_size_(kInitialSize) {
+  : current_size_(0),
+    total_size_(0),
+    rep_(NULL) {
   CopyFrom(other);
 }
 
 template <typename Element>
 template <typename Iter>
-inline RepeatedField<Element>::RepeatedField(Iter begin, const Iter& end)
-  : elements_(NULL),
-    current_size_(0),
-    total_size_(kInitialSize) {
+RepeatedField<Element>::RepeatedField(Iter begin, const Iter& end)
+  : current_size_(0),
+    total_size_(0),
+    rep_(NULL) {
   int reserve = internal::CalculateReserve(begin, end);
   if (reserve != -1) {
     Reserve(reserve);
@@ -612,7 +967,20 @@ inline RepeatedField<Element>::RepeatedField(Iter begin, const Iter& end)
 
 template <typename Element>
 RepeatedField<Element>::~RepeatedField() {
-  delete [] elements_;
+  // See explanation in Reserve(): we need to invoke destructors here for the
+  // case that Element has a non-trivial destructor. If Element has a trivial
+  // destructor (for example, if it's a primitive type, like int32), this entire
+  // loop will be removed by the optimizer.
+  if (rep_ != NULL) {
+    Element* e = &rep_->elements[0];
+    Element* limit = &rep_->elements[total_size_];
+    for (; e < limit; e++) {
+      e->Element::~Element();
+    }
+    if (rep_->arena == NULL) {
+      delete[] reinterpret_cast<char*>(rep_);
+    }
+  }
 }
 
 template <typename Element>
@@ -640,22 +1008,23 @@ inline int RepeatedField<Element>::Capacity() const {
 
 template<typename Element>
 inline void RepeatedField<Element>::AddAlreadyReserved(const Element& value) {
-  GOOGLE_DCHECK_LT(size(), Capacity());
-  elements_[current_size_++] = value;
+  GOOGLE_DCHECK_LT(current_size_, total_size_);
+  rep_->elements[current_size_++] = value;
 }
 
 template<typename Element>
 inline Element* RepeatedField<Element>::AddAlreadyReserved() {
-  GOOGLE_DCHECK_LT(size(), Capacity());
-  return &elements_[current_size_++];
+  GOOGLE_DCHECK_LT(current_size_, total_size_);
+  return &rep_->elements[current_size_++];
 }
 
 template<typename Element>
 inline void RepeatedField<Element>::Resize(int new_size, const Element& value) {
   GOOGLE_DCHECK_GE(new_size, 0);
-  if (new_size > size()) {
+  if (new_size > current_size_) {
     Reserve(new_size);
-    std::fill(&elements_[current_size_], &elements_[new_size], value);
+    std::fill(&rep_->elements[current_size_],
+              &rep_->elements[new_size], value);
   }
   current_size_ = new_size;
 }
@@ -663,40 +1032,40 @@ inline void RepeatedField<Element>::Resize(int new_size, const Element& value) {
 template <typename Element>
 inline const Element& RepeatedField<Element>::Get(int index) const {
   GOOGLE_DCHECK_GE(index, 0);
-  GOOGLE_DCHECK_LT(index, size());
-  return elements_[index];
+  GOOGLE_DCHECK_LT(index, current_size_);
+  return rep_->elements[index];
 }
 
 template <typename Element>
 inline Element* RepeatedField<Element>::Mutable(int index) {
   GOOGLE_DCHECK_GE(index, 0);
-  GOOGLE_DCHECK_LT(index, size());
-  return elements_ + index;
+  GOOGLE_DCHECK_LT(index, current_size_);
+  return &rep_->elements[index];
 }
 
 template <typename Element>
 inline void RepeatedField<Element>::Set(int index, const Element& value) {
   GOOGLE_DCHECK_GE(index, 0);
-  GOOGLE_DCHECK_LT(index, size());
-  elements_[index] = value;
+  GOOGLE_DCHECK_LT(index, current_size_);
+  rep_->elements[index] = value;
 }
 
 template <typename Element>
 inline void RepeatedField<Element>::Add(const Element& value) {
   if (current_size_ == total_size_) Reserve(total_size_ + 1);
-  elements_[current_size_++] = value;
+  rep_->elements[current_size_++] = value;
 }
 
 template <typename Element>
 inline Element* RepeatedField<Element>::Add() {
   if (current_size_ == total_size_) Reserve(total_size_ + 1);
-  return &elements_[current_size_++];
+  return &rep_->elements[current_size_++];
 }
 
 template <typename Element>
 inline void RepeatedField<Element>::RemoveLast() {
   GOOGLE_DCHECK_GT(current_size_, 0);
-  --current_size_;
+  current_size_--;
 }
 
 template <typename Element>
@@ -704,7 +1073,7 @@ void RepeatedField<Element>::ExtractSubrange(
     int start, int num, Element* elements) {
   GOOGLE_DCHECK_GE(start, 0);
   GOOGLE_DCHECK_GE(num, 0);
-  GOOGLE_DCHECK_LE(start + num, this->size());
+  GOOGLE_DCHECK_LE(start + num, this->current_size_);
 
   // Save the values of the removed elements if requested.
   if (elements != NULL) {
@@ -714,9 +1083,9 @@ void RepeatedField<Element>::ExtractSubrange(
 
   // Slide remaining elements down to fill the gap.
   if (num > 0) {
-    for (int i = start + num; i < this->size(); ++i)
+    for (int i = start + num; i < this->current_size_; ++i)
       this->Set(i - num, this->Get(i));
-    this->Truncate(this->size() - num);
+    this->Truncate(this->current_size_ - num);
   }
 }
 
@@ -730,7 +1099,8 @@ inline void RepeatedField<Element>::MergeFrom(const RepeatedField& other) {
   GOOGLE_CHECK_NE(&other, this);
   if (other.current_size_ != 0) {
     Reserve(current_size_ + other.current_size_);
-    CopyArray(elements_ + current_size_, other.elements_, other.current_size_);
+    CopyArray(rep_->elements + current_size_,
+              other.rep_->elements, other.current_size_);
     current_size_ += other.current_size_;
   }
 }
@@ -743,62 +1113,98 @@ inline void RepeatedField<Element>::CopyFrom(const RepeatedField& other) {
 }
 
 template <typename Element>
+inline typename RepeatedField<Element>::iterator RepeatedField<Element>::erase(
+    const_iterator position) {
+  return erase(position, position + 1);
+}
+
+template <typename Element>
+inline typename RepeatedField<Element>::iterator RepeatedField<Element>::erase(
+    const_iterator first, const_iterator last) {
+  size_type first_offset = first - cbegin();
+  Truncate(std::copy(last, cend(), begin() + first_offset) - cbegin());
+  return begin() + first_offset;
+}
+
+template <typename Element>
 inline Element* RepeatedField<Element>::mutable_data() {
-  return elements_;
+  return rep_ ? rep_->elements : NULL;
 }
 
 template <typename Element>
 inline const Element* RepeatedField<Element>::data() const {
-  return elements_;
+  return rep_ ? rep_->elements : NULL;
 }
 
 
 template <typename Element>
+inline void RepeatedField<Element>::InternalSwap(RepeatedField* other) {
+  std::swap(rep_, other->rep_);
+  std::swap(current_size_, other->current_size_);
+  std::swap(total_size_, other->total_size_);
+}
+
+template <typename Element>
 void RepeatedField<Element>::Swap(RepeatedField* other) {
   if (this == other) return;
-  Element* swap_elements     = elements_;
-  int      swap_current_size = current_size_;
-  int      swap_total_size   = total_size_;
-
-  elements_     = other->elements_;
-  current_size_ = other->current_size_;
-  total_size_   = other->total_size_;
+  if (GetArenaNoVirtual() ==  other->GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    RepeatedField<Element> temp(other->GetArenaNoVirtual());
+    temp.MergeFrom(*this);
+    CopyFrom(*other);
+    other->UnsafeArenaSwap(&temp);
+  }
+}
 
-  other->elements_     = swap_elements;
-  other->current_size_ = swap_current_size;
-  other->total_size_   = swap_total_size;
+template <typename Element>
+void RepeatedField<Element>::UnsafeArenaSwap(RepeatedField* other) {
+  if (this == other) return;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  InternalSwap(other);
 }
 
 template <typename Element>
 void RepeatedField<Element>::SwapElements(int index1, int index2) {
   using std::swap;  // enable ADL with fallback
-  swap(elements_[index1], elements_[index2]);
+  swap(rep_->elements[index1], rep_->elements[index2]);
 }
 
 template <typename Element>
 inline typename RepeatedField<Element>::iterator
 RepeatedField<Element>::begin() {
-  return elements_;
+  return rep_ ? rep_->elements : NULL;
 }
 template <typename Element>
 inline typename RepeatedField<Element>::const_iterator
 RepeatedField<Element>::begin() const {
-  return elements_;
+  return rep_ ? rep_->elements : NULL;
+}
+template <typename Element>
+inline typename RepeatedField<Element>::const_iterator
+RepeatedField<Element>::cbegin() const {
+  return rep_ ? rep_->elements : NULL;
 }
 template <typename Element>
 inline typename RepeatedField<Element>::iterator
 RepeatedField<Element>::end() {
-  return elements_ + current_size_;
+  return rep_ ? rep_->elements + current_size_ : NULL;
 }
 template <typename Element>
 inline typename RepeatedField<Element>::const_iterator
 RepeatedField<Element>::end() const {
-  return elements_ + current_size_;
+  return rep_ ? rep_->elements + current_size_ : NULL;
+}
+template <typename Element>
+inline typename RepeatedField<Element>::const_iterator
+RepeatedField<Element>::cend() const {
+  return rep_ ? rep_->elements + current_size_ : NULL;
 }
 
 template <typename Element>
 inline int RepeatedField<Element>::SpaceUsedExcludingSelf() const {
-  return (elements_ != NULL) ? total_size_ * sizeof(elements_[0]) : 0;
+  return rep_ ?
+      (total_size_ * sizeof(Element) + kRepHeaderSize) : 0;
 }
 
 // Avoid inlining of Reserve(): new, copy, and delete[] lead to a significant
@@ -806,32 +1212,66 @@ inline int RepeatedField<Element>::SpaceUsedExcludingSelf() const {
 template <typename Element>
 void RepeatedField<Element>::Reserve(int new_size) {
   if (total_size_ >= new_size) return;
-
-  Element* old_elements = elements_;
-  total_size_ = max(google::protobuf::internal::kMinRepeatedFieldAllocationSize,
-                    max(total_size_ * 2, new_size));
-  elements_ = new Element[total_size_];
-  if (old_elements != NULL) {
-    MoveArray(elements_, old_elements, current_size_);
-    delete [] old_elements;
+  Rep* old_rep = rep_;
+  Arena* arena = GetArenaNoVirtual();
+  new_size = max(google::protobuf::internal::kMinRepeatedFieldAllocationSize,
+                 max(total_size_ * 2, new_size));
+  if (arena == NULL) {
+    rep_ = reinterpret_cast<Rep*>(
+        new char[kRepHeaderSize + sizeof(Element)*new_size]);
+  } else {
+    rep_ = reinterpret_cast<Rep*>(
+            ::google::protobuf::Arena::CreateArray<char>(arena,
+                kRepHeaderSize + sizeof(Element)*new_size));
+  }
+  rep_->arena = arena;
+  total_size_ = new_size;
+  // Invoke placement-new on newly allocated elements. We shouldn't have to do
+  // this, since Element is supposed to be POD, but a previous version of this
+  // code allocated storage with "new Element[size]" and some code uses
+  // RepeatedField with non-POD types, relying on constructor invocation. If
+  // Element has a trivial constructor (e.g., int32), gcc (tested with -O2)
+  // completely removes this loop because the loop body is empty, so this has no
+  // effect unless its side-effects are required for correctness.
+  // Note that we do this before MoveArray() below because Element's copy
+  // assignment implementation will want an initialized instance first.
+  Element* e = &rep_->elements[0];
+  Element* limit = &rep_->elements[total_size_];
+  for (; e < limit; e++) {
+    new (e) Element();
+  }
+  if (current_size_ > 0) {
+    MoveArray(rep_->elements, old_rep->elements, current_size_);
+  }
+  // Likewise, we need to invoke destructors on the old array. If Element has no
+  // destructor, this loop will disappear.
+  e = &old_rep->elements[0];
+  limit = &old_rep->elements[current_size_];
+  for (; e < limit; e++) {
+    e->Element::~Element();
+  }
+  if (arena == NULL) {
+    delete[] reinterpret_cast<char*>(old_rep);
   }
 }
 
 template <typename Element>
 inline void RepeatedField<Element>::Truncate(int new_size) {
   GOOGLE_DCHECK_LE(new_size, current_size_);
-  current_size_ = new_size;
+  if (current_size_ > 0) {
+    current_size_ = new_size;
+  }
 }
 
 template <typename Element>
 inline void RepeatedField<Element>::MoveArray(
-    Element to[], Element from[], int array_size) {
+  Element* to, Element* from, int array_size) {
   CopyArray(to, from, array_size);
 }
 
 template <typename Element>
 inline void RepeatedField<Element>::CopyArray(
-    Element to[], const Element from[], int array_size) {
+  Element* to, const Element* from, int array_size) {
   internal::ElementCopier<Element>()(to, from, array_size);
 }
 
@@ -839,13 +1279,13 @@ namespace internal {
 
 template <typename Element, bool HasTrivialCopy>
 void ElementCopier<Element, HasTrivialCopy>::operator()(
-    Element to[], const Element from[], int array_size) {
+  Element* to, const Element* from, int array_size) {
   std::copy(from, from + array_size, to);
 }
 
 template <typename Element>
 struct ElementCopier<Element, true> {
-  void operator()(Element to[], const Element from[], int array_size) {
+  void operator()(Element* to, const Element* from, int array_size) {
     memcpy(to, from, array_size * sizeof(Element));
   }
 };
@@ -858,18 +1298,55 @@ struct ElementCopier<Element, true> {
 namespace internal {
 
 inline RepeatedPtrFieldBase::RepeatedPtrFieldBase()
-  : elements_(NULL),
+  : arena_(NULL),
     current_size_(0),
-    allocated_size_(0),
-    total_size_(kInitialSize) {
+    total_size_(0),
+    rep_(NULL) {
+}
+
+inline RepeatedPtrFieldBase::RepeatedPtrFieldBase(::google::protobuf::Arena* arena)
+  : arena_(arena),
+    current_size_(0),
+    total_size_(0),
+    rep_(NULL) {
 }
 
 template <typename TypeHandler>
 void RepeatedPtrFieldBase::Destroy() {
-  for (int i = 0; i < allocated_size_; i++) {
-    TypeHandler::Delete(cast<TypeHandler>(elements_[i]));
+  if (rep_ != NULL) {
+    for (int i = 0; i < rep_->allocated_size; i++) {
+      TypeHandler::Delete(cast<TypeHandler>(rep_->elements[i]), arena_);
+    }
+    if (arena_ == NULL) {
+      delete [] reinterpret_cast<char*>(rep_);
+    }
   }
-  delete [] elements_;
+  rep_ = NULL;
+}
+
+template <typename TypeHandler>
+inline void RepeatedPtrFieldBase::Swap(RepeatedPtrFieldBase* other) {
+  if (other->GetArenaNoVirtual() == GetArenaNoVirtual()) {
+    InternalSwap(other);
+  } else {
+    SwapFallback<TypeHandler>(other);
+  }
+}
+
+template <typename TypeHandler>
+inline void RepeatedPtrFieldBase::SwapFallback(RepeatedPtrFieldBase* other) {
+  GOOGLE_DCHECK(other->GetArenaNoVirtual() != GetArenaNoVirtual());
+
+  // Copy semantics in this case. We try to improve efficiency by placing the
+  // temporary on |other|'s arena so that messages are copied cross-arena only
+  // once, not twice.
+  RepeatedPtrFieldBase temp(other->GetArenaNoVirtual());
+  temp.MergeFrom<TypeHandler>(*this);
+  this->Clear<TypeHandler>();
+  this->MergeFrom<TypeHandler>(*other);
+  other->Clear<TypeHandler>();
+  other->InternalSwap(&temp);
+  temp.Destroy<TypeHandler>();  // Frees rep_ if `other` had no arena.
 }
 
 inline bool RepeatedPtrFieldBase::empty() const {
@@ -884,8 +1361,8 @@ template <typename TypeHandler>
 inline const typename TypeHandler::Type&
 RepeatedPtrFieldBase::Get(int index) const {
   GOOGLE_DCHECK_GE(index, 0);
-  GOOGLE_DCHECK_LT(index, size());
-  return *cast<TypeHandler>(elements_[index]);
+  GOOGLE_DCHECK_LT(index, current_size_);
+  return *cast<TypeHandler>(rep_->elements[index]);
 }
 
 
@@ -893,42 +1370,106 @@ template <typename TypeHandler>
 inline typename TypeHandler::Type*
 RepeatedPtrFieldBase::Mutable(int index) {
   GOOGLE_DCHECK_GE(index, 0);
-  GOOGLE_DCHECK_LT(index, size());
-  return cast<TypeHandler>(elements_[index]);
+  GOOGLE_DCHECK_LT(index, current_size_);
+  return cast<TypeHandler>(rep_->elements[index]);
 }
 
 template <typename TypeHandler>
-inline typename TypeHandler::Type* RepeatedPtrFieldBase::Add() {
-  if (current_size_ < allocated_size_) {
-    return cast<TypeHandler>(elements_[current_size_++]);
-  }
-  if (allocated_size_ == total_size_) Reserve(total_size_ + 1);
-  typename TypeHandler::Type* result = TypeHandler::New();
-  ++allocated_size_;
-  elements_[current_size_++] = result;
+inline void RepeatedPtrFieldBase::Delete(int index) {
+  GOOGLE_DCHECK_GE(index, 0);
+  GOOGLE_DCHECK_LT(index, current_size_);
+  TypeHandler::Delete(cast<TypeHandler>(rep_->elements[index]), arena_);
+}
+
+template <typename TypeHandler>
+inline typename TypeHandler::Type* RepeatedPtrFieldBase::Add(
+    typename TypeHandler::Type* prototype) {
+  if (rep_ != NULL && current_size_ < rep_->allocated_size) {
+    return cast<TypeHandler>(rep_->elements[current_size_++]);
+  }
+  if (!rep_ || rep_->allocated_size == total_size_) {
+    Reserve(total_size_ + 1);
+  }
+  ++rep_->allocated_size;
+  typename TypeHandler::Type* result =
+      TypeHandler::NewFromPrototype(prototype, arena_);
+  rep_->elements[current_size_++] = result;
   return result;
 }
 
 template <typename TypeHandler>
 inline void RepeatedPtrFieldBase::RemoveLast() {
   GOOGLE_DCHECK_GT(current_size_, 0);
-  TypeHandler::Clear(cast<TypeHandler>(elements_[--current_size_]));
+  TypeHandler::Clear(cast<TypeHandler>(rep_->elements[--current_size_]));
 }
 
 template <typename TypeHandler>
 void RepeatedPtrFieldBase::Clear() {
-  for (int i = 0; i < current_size_; i++) {
-    TypeHandler::Clear(cast<TypeHandler>(elements_[i]));
+  const int n = current_size_;
+  GOOGLE_DCHECK_GE(n, 0);
+  if (n > 0) {
+    void* const* elements = raw_data();
+    int i = 0;
+    do {
+      TypeHandler::Clear(cast<TypeHandler>(elements[i++]));
+    } while (i < n);
+    current_size_ = 0;
   }
-  current_size_ = 0;
 }
 
+// To avoid unnecessary code duplication and reduce binary size, we use a
+// layered approach to implementing MergeFrom(). The toplevel method is
+// templated, so we get a small thunk per concrete message type in the binary.
+// This calls a shared implementation with most of the logic, passing a function
+// pointer to another type-specific piece of code that calls the object-allocate
+// and merge handlers.
 template <typename TypeHandler>
 inline void RepeatedPtrFieldBase::MergeFrom(const RepeatedPtrFieldBase& other) {
-  GOOGLE_CHECK_NE(&other, this);
-  Reserve(current_size_ + other.current_size_);
-  for (int i = 0; i < other.current_size_; i++) {
-    TypeHandler::Merge(other.template Get<TypeHandler>(i), Add<TypeHandler>());
+  GOOGLE_DCHECK_NE(&other, this);
+  if (other.current_size_ == 0) return;
+  MergeFromInternal(
+      other, &RepeatedPtrFieldBase::MergeFromInnerLoop<TypeHandler>);
+}
+
+inline void RepeatedPtrFieldBase::MergeFromInternal(
+    const RepeatedPtrFieldBase& other,
+    void (RepeatedPtrFieldBase::*inner_loop)(void**, void**, int, int)) {
+  // Note: wrapper has already guaranteed that other.rep_ != NULL here.
+  int other_size = other.current_size_;
+  void** other_elements = other.rep_->elements;
+  void** new_elements = InternalExtend(other_size);
+  int allocated_elems = rep_->allocated_size - current_size_;
+  (this->*inner_loop)(new_elements, other_elements,
+                      other_size, allocated_elems);
+  current_size_ += other_size;
+  if (rep_->allocated_size < current_size_) {
+    rep_->allocated_size = current_size_;
+  }
+}
+
+// Merges other_elems to our_elems.
+template<typename TypeHandler>
+void RepeatedPtrFieldBase::MergeFromInnerLoop(
+    void** our_elems, void** other_elems, int length, int already_allocated) {
+  // Split into two loops, over ranges [0, allocated) and [allocated, length),
+  // to avoid a branch within the loop.
+  for (int i = 0; i < already_allocated && i < length; i++) {
+    // Already allocated: use existing element.
+    typename TypeHandler::Type* other_elem =
+        reinterpret_cast<typename TypeHandler::Type*>(other_elems[i]);
+    typename TypeHandler::Type* new_elem =
+        reinterpret_cast<typename TypeHandler::Type*>(our_elems[i]);
+    TypeHandler::Merge(*other_elem, new_elem);
+  }
+  Arena* arena = GetArenaNoVirtual();
+  for (int i = already_allocated; i < length; i++) {
+    // Not allocated: alloc a new element first, then merge it.
+    typename TypeHandler::Type* other_elem =
+        reinterpret_cast<typename TypeHandler::Type*>(other_elems[i]);
+    typename TypeHandler::Type* new_elem =
+        TypeHandler::NewFromPrototype(other_elem, arena);
+    TypeHandler::Merge(*other_elem, new_elem);
+    our_elems[i] = new_elem;
   }
 }
 
@@ -944,18 +1485,18 @@ inline int RepeatedPtrFieldBase::Capacity() const {
 }
 
 inline void* const* RepeatedPtrFieldBase::raw_data() const {
-  return elements_;
+  return rep_ ? rep_->elements : NULL;
 }
 
 inline void** RepeatedPtrFieldBase::raw_mutable_data() const {
-  return elements_;
+  return rep_ ? const_cast<void**>(rep_->elements) : NULL;
 }
 
 template <typename TypeHandler>
 inline typename TypeHandler::Type** RepeatedPtrFieldBase::mutable_data() {
   // TODO(kenton):  Breaks C++ aliasing rules.  We should probably remove this
   //   method entirely.
-  return reinterpret_cast<typename TypeHandler::Type**>(elements_);
+  return reinterpret_cast<typename TypeHandler::Type**>(raw_mutable_data());
 }
 
 template <typename TypeHandler>
@@ -963,89 +1504,212 @@ inline const typename TypeHandler::Type* const*
 RepeatedPtrFieldBase::data() const {
   // TODO(kenton):  Breaks C++ aliasing rules.  We should probably remove this
   //   method entirely.
-  return reinterpret_cast<const typename TypeHandler::Type* const*>(elements_);
+  return reinterpret_cast<const typename TypeHandler::Type* const*>(raw_data());
 }
 
 inline void RepeatedPtrFieldBase::SwapElements(int index1, int index2) {
   using std::swap;  // enable ADL with fallback
-  swap(elements_[index1], elements_[index2]);
+  swap(rep_->elements[index1], rep_->elements[index2]);
 }
 
 template <typename TypeHandler>
 inline int RepeatedPtrFieldBase::SpaceUsedExcludingSelf() const {
-  int allocated_bytes =
-      (elements_ != NULL) ? total_size_ * sizeof(elements_[0]) : 0;
-  for (int i = 0; i < allocated_size_; ++i) {
-    allocated_bytes += TypeHandler::SpaceUsed(*cast<TypeHandler>(elements_[i]));
+  int allocated_bytes = total_size_ * sizeof(void*);
+  if (rep_ != NULL) {
+    for (int i = 0; i < rep_->allocated_size; ++i) {
+      allocated_bytes += TypeHandler::SpaceUsed(
+          *cast<TypeHandler>(rep_->elements[i]));
+    }
+    allocated_bytes += kRepHeaderSize;
   }
   return allocated_bytes;
 }
 
 template <typename TypeHandler>
 inline typename TypeHandler::Type* RepeatedPtrFieldBase::AddFromCleared() {
-  if (current_size_ < allocated_size_) {
-    return cast<TypeHandler>(elements_[current_size_++]);
+  if (rep_ != NULL && current_size_ < rep_->allocated_size) {
+    return cast<TypeHandler>(rep_->elements[current_size_++]);
   } else {
     return NULL;
   }
 }
 
+// AddAllocated version that implements arena-safe copying behavior.
 template <typename TypeHandler>
-void RepeatedPtrFieldBase::AddAllocated(
+void RepeatedPtrFieldBase::AddAllocatedInternal(
+    typename TypeHandler::Type* value,
+    google::protobuf::internal::true_type) {
+  Arena* element_arena = reinterpret_cast<Arena*>(
+      TypeHandler::GetMaybeArenaPointer(value));
+  Arena* arena = GetArenaNoVirtual();
+  if (arena == element_arena && rep_ &&
+      rep_->allocated_size < total_size_) {
+    // Fast path: underlying arena representation (tagged pointer) is equal to
+    // our arena pointer, and we can add to array without resizing it (at least
+    // one slot that is not allocated).
+    void** elems = rep_->elements;
+    if (current_size_ < rep_->allocated_size) {
+      // Make space at [current] by moving first allocated element to end of
+      // allocated list.
+      elems[rep_->allocated_size] = elems[current_size_];
+    }
+    elems[current_size_] = value;
+    current_size_ = current_size_ + 1;
+    rep_->allocated_size = rep_->allocated_size + 1;
+    return;
+  } else {
+    AddAllocatedSlowWithCopy<TypeHandler>(
+        value, TypeHandler::GetArena(value), arena);
+  }
+}
+
+// Slowpath handles all cases, copying if necessary.
+template<typename TypeHandler>
+void RepeatedPtrFieldBase::AddAllocatedSlowWithCopy(
+    // Pass value_arena and my_arena to avoid duplicate virtual call (value) or
+    // load (mine).
+    typename TypeHandler::Type* value, Arena* value_arena, Arena* my_arena) {
+  // Ensure that either the value is in the same arena, or if not, we do the
+  // appropriate thing: Own() it (if it's on heap and we're in an arena) or copy
+  // it to our arena/heap (otherwise).
+  if (my_arena != NULL && value_arena == NULL) {
+    my_arena->Own(value);
+  } else if (my_arena != value_arena) {
+    typename TypeHandler::Type* new_value =
+        TypeHandler::NewFromPrototype(value, my_arena);
+    TypeHandler::Merge(*value, new_value);
+    TypeHandler::Delete(value, value_arena);
+    value = new_value;
+  }
+
+  UnsafeArenaAddAllocated<TypeHandler>(value);
+}
+
+// AddAllocated version that does not implement arena-safe copying behavior.
+template <typename TypeHandler>
+void RepeatedPtrFieldBase::AddAllocatedInternal(
+    typename TypeHandler::Type* value,
+    google::protobuf::internal::false_type) {
+  if (rep_ &&  rep_->allocated_size < total_size_) {
+    // Fast path: underlying arena representation (tagged pointer) is equal to
+    // our arena pointer, and we can add to array without resizing it (at least
+    // one slot that is not allocated).
+    void** elems = rep_->elements;
+    if (current_size_ < rep_->allocated_size) {
+      // Make space at [current] by moving first allocated element to end of
+      // allocated list.
+      elems[rep_->allocated_size] = elems[current_size_];
+    }
+    elems[current_size_] = value;
+    current_size_ = current_size_ + 1;
+    ++rep_->allocated_size;
+    return;
+  } else {
+    UnsafeArenaAddAllocated<TypeHandler>(value);
+  }
+}
+
+template <typename TypeHandler>
+void RepeatedPtrFieldBase::UnsafeArenaAddAllocated(
     typename TypeHandler::Type* value) {
   // Make room for the new pointer.
-  if (current_size_ == total_size_) {
+  if (!rep_ || current_size_ == total_size_) {
     // The array is completely full with no cleared objects, so grow it.
     Reserve(total_size_ + 1);
-    ++allocated_size_;
-  } else if (allocated_size_ == total_size_) {
+    ++rep_->allocated_size;
+  } else if (rep_->allocated_size == total_size_) {
     // There is no more space in the pointer array because it contains some
     // cleared objects awaiting reuse.  We don't want to grow the array in this
     // case because otherwise a loop calling AddAllocated() followed by Clear()
     // would leak memory.
-    TypeHandler::Delete(cast<TypeHandler>(elements_[current_size_]));
-  } else if (current_size_ < allocated_size_) {
+    TypeHandler::Delete(
+        cast<TypeHandler>(rep_->elements[current_size_]), arena_);
+  } else if (current_size_ < rep_->allocated_size) {
     // We have some cleared objects.  We don't care about their order, so we
     // can just move the first one to the end to make space.
-    elements_[allocated_size_] = elements_[current_size_];
-    ++allocated_size_;
+    rep_->elements[rep_->allocated_size] = rep_->elements[current_size_];
+    ++rep_->allocated_size;
   } else {
     // There are no cleared objects.
-    ++allocated_size_;
+    ++rep_->allocated_size;
+  }
+
+  rep_->elements[current_size_++] = value;
+}
+
+// ReleaseLast() for types that implement merge/copy behavior.
+template <typename TypeHandler>
+inline typename TypeHandler::Type*
+RepeatedPtrFieldBase::ReleaseLastInternal(google::protobuf::internal::true_type) {
+  // First, release an element.
+  typename TypeHandler::Type* result = UnsafeArenaReleaseLast<TypeHandler>();
+  // Now perform a copy if we're on an arena.
+  Arena* arena = GetArenaNoVirtual();
+  if (arena == NULL) {
+    return result;
+  } else {
+    typename TypeHandler::Type* new_result =
+        TypeHandler::NewFromPrototype(result, NULL);
+    TypeHandler::Merge(*result, new_result);
+    return new_result;
   }
+}
 
-  elements_[current_size_++] = value;
+// ReleaseLast() for types that *do not* implement merge/copy behavior -- this
+// is the same as UnsafeArenaReleaseLast(). Note that we GOOGLE_DCHECK-fail if we're on
+// an arena, since the user really should implement the copy operation in this
+// case.
+template <typename TypeHandler>
+inline typename TypeHandler::Type*
+RepeatedPtrFieldBase::ReleaseLastInternal(google::protobuf::internal::false_type) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() == NULL)
+      << "ReleaseLast() called on a RepeatedPtrField that is on an arena, "
+      << "with a type that does not implement MergeFrom. This is unsafe; "
+      << "please implement MergeFrom for your type.";
+  return UnsafeArenaReleaseLast<TypeHandler>();
 }
 
 template <typename TypeHandler>
-inline typename TypeHandler::Type* RepeatedPtrFieldBase::ReleaseLast() {
+inline typename TypeHandler::Type*
+  RepeatedPtrFieldBase::UnsafeArenaReleaseLast() {
   GOOGLE_DCHECK_GT(current_size_, 0);
   typename TypeHandler::Type* result =
-      cast<TypeHandler>(elements_[--current_size_]);
-  --allocated_size_;
-  if (current_size_ < allocated_size_) {
+      cast<TypeHandler>(rep_->elements[--current_size_]);
+  --rep_->allocated_size;
+  if (current_size_ < rep_->allocated_size) {
     // There are cleared elements on the end; replace the removed element
     // with the last allocated element.
-    elements_[current_size_] = elements_[allocated_size_];
+    rep_->elements[current_size_] = rep_->elements[rep_->allocated_size];
   }
   return result;
 }
 
 inline int RepeatedPtrFieldBase::ClearedCount() const {
-  return allocated_size_ - current_size_;
+  return rep_ ? (rep_->allocated_size - current_size_) : 0;
 }
 
 template <typename TypeHandler>
 inline void RepeatedPtrFieldBase::AddCleared(
     typename TypeHandler::Type* value) {
-  if (allocated_size_ == total_size_) Reserve(total_size_ + 1);
-  elements_[allocated_size_++] = value;
+  GOOGLE_DCHECK(GetArenaNoVirtual() == NULL)
+      << "AddCleared() can only be used on a RepeatedPtrField not on an arena.";
+  GOOGLE_DCHECK(TypeHandler::GetArena(value) == NULL)
+      << "AddCleared() can only accept values not on an arena.";
+  if (!rep_ || rep_->allocated_size == total_size_) {
+    Reserve(total_size_ + 1);
+  }
+  rep_->elements[rep_->allocated_size++] = value;
 }
 
 template <typename TypeHandler>
 inline typename TypeHandler::Type* RepeatedPtrFieldBase::ReleaseCleared() {
-  GOOGLE_DCHECK_GT(allocated_size_, current_size_);
-  return cast<TypeHandler>(elements_[--allocated_size_]);
+  GOOGLE_DCHECK(GetArenaNoVirtual() == NULL)
+      << "ReleaseCleared() can only be used on a RepeatedPtrField not on "
+      << "an arena.";
+  GOOGLE_DCHECK(GetArenaNoVirtual() == NULL);
+  GOOGLE_DCHECK(rep_ != NULL);
+  GOOGLE_DCHECK_GT(rep_->allocated_size, current_size_);
+  return cast<TypeHandler>(rep_->elements[--rep_->allocated_size]);
 }
 
 }  // namespace internal
@@ -1064,12 +1728,17 @@ class RepeatedPtrField<string>::TypeHandler
 
 
 template <typename Element>
-inline RepeatedPtrField<Element>::RepeatedPtrField() {}
+inline RepeatedPtrField<Element>::RepeatedPtrField()
+  : RepeatedPtrFieldBase() {}
+
+template <typename Element>
+inline RepeatedPtrField<Element>::RepeatedPtrField(::google::protobuf::Arena* arena) :
+  RepeatedPtrFieldBase(arena) {}
 
 template <typename Element>
 inline RepeatedPtrField<Element>::RepeatedPtrField(
     const RepeatedPtrField& other)
-    : RepeatedPtrFieldBase() {
+  : RepeatedPtrFieldBase() {
   CopyFrom(other);
 }
 
@@ -1135,14 +1804,25 @@ inline void RepeatedPtrField<Element>::DeleteSubrange(int start, int num) {
   GOOGLE_DCHECK_GE(start, 0);
   GOOGLE_DCHECK_GE(num, 0);
   GOOGLE_DCHECK_LE(start + num, size());
-  for (int i = 0; i < num; ++i)
-    delete RepeatedPtrFieldBase::Mutable<TypeHandler>(start + i);
+  for (int i = 0; i < num; ++i) {
+    RepeatedPtrFieldBase::Delete<TypeHandler>(start + i);
+  }
   ExtractSubrange(start, num, NULL);
 }
 
 template <typename Element>
 inline void RepeatedPtrField<Element>::ExtractSubrange(
     int start, int num, Element** elements) {
+  typename internal::TypeImplementsMergeBehavior<
+      typename TypeHandler::Type>::type t;
+  ExtractSubrangeInternal(start, num, elements, t);
+}
+
+// ExtractSubrange() implementation for types that implement merge/copy
+// behavior.
+template <typename Element>
+inline void RepeatedPtrField<Element>::ExtractSubrangeInternal(
+    int start, int num, Element** elements, google::protobuf::internal::true_type) {
   GOOGLE_DCHECK_GE(start, 0);
   GOOGLE_DCHECK_GE(num, 0);
   GOOGLE_DCHECK_LE(start + num, size());
@@ -1150,8 +1830,55 @@ inline void RepeatedPtrField<Element>::ExtractSubrange(
   if (num > 0) {
     // Save the values of the removed elements if requested.
     if (elements != NULL) {
-      for (int i = 0; i < num; ++i)
+      if (GetArenaNoVirtual() != NULL) {
+        // If we're on an arena, we perform a copy for each element so that the
+        // returned elements are heap-allocated.
+        for (int i = 0; i < num; ++i) {
+          Element* element = RepeatedPtrFieldBase::
+              Mutable<TypeHandler>(i + start);
+          typename TypeHandler::Type* new_value =
+              TypeHandler::NewFromPrototype(element, NULL);
+          TypeHandler::Merge(*element, new_value);
+          elements[i] = new_value;
+        }
+      } else {
+        for (int i = 0; i < num; ++i) {
+          elements[i] = RepeatedPtrFieldBase::Mutable<TypeHandler>(i + start);
+        }
+      }
+    }
+    CloseGap(start, num);
+  }
+}
+
+// ExtractSubrange() implementation for types that do not implement merge/copy
+// behavior.
+template<typename Element>
+inline void RepeatedPtrField<Element>::ExtractSubrangeInternal(
+    int start, int num, Element** elements, google::protobuf::internal::false_type) {
+  // This case is identical to UnsafeArenaExtractSubrange(). However, since
+  // ExtractSubrange() must return heap-allocated objects by contract, and we
+  // cannot fulfill this contract if we are an on arena, we must GOOGLE_DCHECK() that
+  // we are not on an arena.
+  GOOGLE_DCHECK(GetArenaNoVirtual() == NULL)
+      << "ExtractSubrange() when arena is non-NULL is only supported when "
+      << "the Element type supplies a MergeFrom() operation to make copies.";
+  UnsafeArenaExtractSubrange(start, num, elements);
+}
+
+template <typename Element>
+inline void RepeatedPtrField<Element>::UnsafeArenaExtractSubrange(
+    int start, int num, Element** elements) {
+  GOOGLE_DCHECK_GE(start, 0);
+  GOOGLE_DCHECK_GE(num, 0);
+  GOOGLE_DCHECK_LE(start + num, size());
+
+  if (num > 0) {
+    // Save the values of the removed elements if requested.
+    if (elements != NULL) {
+      for (int i = 0; i < num; ++i) {
         elements[i] = RepeatedPtrFieldBase::Mutable<TypeHandler>(i + start);
+      }
     }
     CloseGap(start, num);
   }
@@ -1175,6 +1902,21 @@ inline void RepeatedPtrField<Element>::CopyFrom(
 }
 
 template <typename Element>
+inline typename RepeatedPtrField<Element>::iterator
+RepeatedPtrField<Element>::erase(const_iterator position) {
+  return erase(position, position + 1);
+}
+
+template <typename Element>
+inline typename RepeatedPtrField<Element>::iterator
+RepeatedPtrField<Element>::erase(const_iterator first, const_iterator last) {
+  size_type pos_offset = std::distance(cbegin(), first);
+  size_type last_offset = std::distance(cbegin(), last);
+  DeleteSubrange(pos_offset, last_offset - pos_offset);
+  return begin() + pos_offset;
+}
+
+template <typename Element>
 inline Element** RepeatedPtrField<Element>::mutable_data() {
   return RepeatedPtrFieldBase::mutable_data<TypeHandler>();
 }
@@ -1185,16 +1927,32 @@ inline const Element* const* RepeatedPtrField<Element>::data() const {
 }
 
 template <typename Element>
-void RepeatedPtrField<Element>::Swap(RepeatedPtrField* other) {
-  RepeatedPtrFieldBase::Swap(other);
+inline void RepeatedPtrField<Element>::Swap(RepeatedPtrField* other) {
+  if (this == other)
+    return;
+  RepeatedPtrFieldBase::Swap<TypeHandler>(other);
 }
 
 template <typename Element>
-void RepeatedPtrField<Element>::SwapElements(int index1, int index2) {
+inline void RepeatedPtrField<Element>::UnsafeArenaSwap(
+    RepeatedPtrField* other) {
+  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());
+  if (this == other)
+      return;
+  RepeatedPtrFieldBase::InternalSwap(other);
+}
+
+template <typename Element>
+inline void RepeatedPtrField<Element>::SwapElements(int index1, int index2) {
   RepeatedPtrFieldBase::SwapElements(index1, index2);
 }
 
 template <typename Element>
+inline Arena* RepeatedPtrField<Element>::GetArenaNoVirtual() const {
+  return RepeatedPtrFieldBase::GetArenaNoVirtual();
+}
+
+template <typename Element>
 inline int RepeatedPtrField<Element>::SpaceUsedExcludingSelf() const {
   return RepeatedPtrFieldBase::SpaceUsedExcludingSelf<TypeHandler>();
 }
@@ -1205,10 +1963,19 @@ inline void RepeatedPtrField<Element>::AddAllocated(Element* value) {
 }
 
 template <typename Element>
+inline void RepeatedPtrField<Element>::UnsafeArenaAddAllocated(Element* value) {
+  RepeatedPtrFieldBase::UnsafeArenaAddAllocated<TypeHandler>(value);
+}
+
+template <typename Element>
 inline Element* RepeatedPtrField<Element>::ReleaseLast() {
   return RepeatedPtrFieldBase::ReleaseLast<TypeHandler>();
 }
 
+template <typename Element>
+inline Element* RepeatedPtrField<Element>::UnsafeArenaReleaseLast() {
+  return RepeatedPtrFieldBase::UnsafeArenaReleaseLast<TypeHandler>();
+}
 
 template <typename Element>
 inline int RepeatedPtrField<Element>::ClearedCount() const {
@@ -1423,6 +2190,12 @@ class RepeatedPtrOverPtrsIterator
   VoidPtr* it_;
 };
 
+void RepeatedPtrFieldBase::InternalSwap(RepeatedPtrFieldBase* other) {
+  std::swap(rep_, other->rep_);
+  std::swap(current_size_, other->current_size_);
+  std::swap(total_size_, other->total_size_);
+}
+
 }  // namespace internal
 
 template <typename Element>
@@ -1436,6 +2209,11 @@ RepeatedPtrField<Element>::begin() const {
   return iterator(raw_data());
 }
 template <typename Element>
+inline typename RepeatedPtrField<Element>::const_iterator
+RepeatedPtrField<Element>::cbegin() const {
+  return begin();
+}
+template <typename Element>
 inline typename RepeatedPtrField<Element>::iterator
 RepeatedPtrField<Element>::end() {
   return iterator(raw_data() + size());
@@ -1445,6 +2223,11 @@ inline typename RepeatedPtrField<Element>::const_iterator
 RepeatedPtrField<Element>::end() const {
   return iterator(raw_data() + size());
 }
+template <typename Element>
+inline typename RepeatedPtrField<Element>::const_iterator
+RepeatedPtrField<Element>::cend() const {
+  return end();
+}
 
 template <typename Element>
 inline typename RepeatedPtrField<Element>::pointer_iterator
diff --git a/src/google/protobuf/repeated_field_reflection.h b/src/google/protobuf/repeated_field_reflection.h
new file mode 100644
index 00000000..08dfa7a5
--- /dev/null
+++ b/src/google/protobuf/repeated_field_reflection.h
@@ -0,0 +1,335 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This header file is protobuf internal. Users should not include this
+// file directly.
+#ifndef GOOGLE_PROTOBUF_REPEATED_FIELD_REFLECTION_H__
+#define GOOGLE_PROTOBUF_REPEATED_FIELD_REFLECTION_H__
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+
+namespace google {
+namespace protobuf {
+namespace internal {
+// Interfaces used to implement reflection RepeatedFieldRef API.
+// Reflection::GetRepeatedAccessor() should return a pointer to an singleton
+// object that implements the below interface.
+//
+// This interface passes/returns values using void pointers. The actual type
+// of the value depends on the field's cpp_type. Following is a mapping from
+// cpp_type to the type that should be used in this interface:
+//
+//   field->cpp_type()      T                Actual type of void*
+//   CPPTYPE_INT32        int32                   int32
+//   CPPTYPE_UINT32       uint32                  uint32
+//   CPPTYPE_INT64        int64                   int64
+//   CPPTYPE_UINT64       uint64                  uint64
+//   CPPTYPE_DOUBLE       double                  double
+//   CPPTYPE_FLOAT        float                   float
+//   CPPTYPE_BOOL         bool                    bool
+//   CPPTYPE_ENUM         generated enum type     int32
+//   CPPTYPE_STRING       string                  string
+//   CPPTYPE_MESSAGE      generated message type  google::protobuf::Message
+//                        or google::protobuf::Message
+//
+// Note that for enums we use int32 in the interface.
+//
+// You can map from T to the actual type using RefTypeTraits:
+//   typedef RefTypeTraits<T>::AccessorValueType ActualType;
+class LIBPROTOBUF_EXPORT RepeatedFieldAccessor {
+ public:
+  // Typedefs for clarity.
+  typedef void Field;
+  typedef void Value;
+  typedef void Iterator;
+
+  virtual ~RepeatedFieldAccessor();
+  virtual bool IsEmpty(const Field* data) const = 0;
+  virtual int Size(const Field* data) const = 0;
+  // Depends on the underlying representation of the repeated field, this
+  // method can return a pointer to the underlying object if such an object
+  // exists, or fill the data into scratch_space and return scratch_space.
+  // Callers of this method must ensure scratch_space is a valid pointer
+  // to a mutable object of the correct type.
+  virtual const Value* Get(
+      const Field* data, int index, Value* scratch_space) const = 0;
+
+  virtual void Clear(Field* data) const = 0;
+  virtual void Set(Field* data, int index, const Value* value) const = 0;
+  virtual void Add(Field* data, const Value* value) const = 0;
+  virtual void RemoveLast(Field* data) const = 0;
+  virtual void SwapElements(Field* data, int index1, int index2) const = 0;
+  virtual void Swap(Field* data, const RepeatedFieldAccessor* other_mutator,
+                    Field* other_data) const = 0;
+
+  // Create an iterator that points at the begining of the repeated field.
+  virtual Iterator* BeginIterator(const Field* data) const = 0;
+  // Create an iterator that points at the end of the repeated field.
+  virtual Iterator* EndIterator(const Field* data) const = 0;
+  // Make a copy of an iterator and return the new copy.
+  virtual Iterator* CopyIterator(const Field* data,
+                                 const Iterator* iterator) const = 0;
+  // Move an iterator to point to the next element.
+  virtual Iterator* AdvanceIterator(const Field* data,
+                                    Iterator* iterator) const = 0;
+  // Compare whether two iterators point to the same element.
+  virtual bool EqualsIterator(const Field* data, const Iterator* a,
+                              const Iterator* b) const = 0;
+  // Delete an iterator created by BeginIterator(), EndIterator() and
+  // CopyIterator().
+  virtual void DeleteIterator(const Field* data, Iterator* iterator) const = 0;
+  // Like Get() but for iterators.
+  virtual const Value* GetIteratorValue(const Field* data,
+                                        const Iterator* iterator,
+                                        Value* scratch_space) const = 0;
+
+  // Templated methods that make using this interface easier for non-message
+  // types.
+  template<typename T>
+  T Get(const Field* data, int index) const {
+    typedef typename RefTypeTraits<T>::AccessorValueType ActualType;
+    ActualType scratch_space;
+    return static_cast<T>(
+        *reinterpret_cast<const ActualType*>(
+            Get(data, index, static_cast<Value*>(&scratch_space))));
+  }
+
+  template<typename T, typename ValueType>
+  void Set(Field* data, int index, const ValueType& value) const {
+    typedef typename RefTypeTraits<T>::AccessorValueType ActualType;
+    // In this RepeatedFieldAccessor interface we pass/return data using
+    // raw pointers. Type of the data these raw pointers point to should
+    // be ActualType. Here we have a ValueType object and want a ActualType
+    // pointer. We can't cast a ValueType pointer to an ActualType pointer
+    // directly because their type might be different (for enums ValueType
+    // may be a generated enum type while ActualType is int32). To be safe
+    // we make a copy to get a temporary ActualType object and use it.
+    ActualType tmp = static_cast<ActualType>(value);
+    Set(data, index, static_cast<const Value*>(&tmp));
+  }
+
+  template<typename T, typename ValueType>
+  void Add(Field* data, const ValueType& value) const {
+    typedef typename RefTypeTraits<T>::AccessorValueType ActualType;
+    // In this RepeatedFieldAccessor interface we pass/return data using
+    // raw pointers. Type of the data these raw pointers point to should
+    // be ActualType. Here we have a ValueType object and want a ActualType
+    // pointer. We can't cast a ValueType pointer to an ActualType pointer
+    // directly because their type might be different (for enums ValueType
+    // may be a generated enum type while ActualType is int32). To be safe
+    // we make a copy to get a temporary ActualType object and use it.
+    ActualType tmp = static_cast<ActualType>(value);
+    Add(data, static_cast<const Value*>(&tmp));
+  }
+};
+
+// Implement (Mutable)RepeatedFieldRef::iterator
+template<typename T>
+class RepeatedFieldRefIterator
+    : public std::iterator<std::forward_iterator_tag, T> {
+  typedef typename RefTypeTraits<T>::AccessorValueType AccessorValueType;
+  typedef typename RefTypeTraits<T>::IteratorValueType IteratorValueType;
+  typedef typename RefTypeTraits<T>::IteratorPointerType IteratorPointerType;
+
+ public:
+  // Constructor for non-message fields.
+  RepeatedFieldRefIterator(const void* data,
+                           const RepeatedFieldAccessor* accessor,
+                           bool begin)
+      : data_(data), accessor_(accessor),
+        iterator_(begin ? accessor->BeginIterator(data) :
+                          accessor->EndIterator(data)),
+        scratch_space_(new AccessorValueType) {
+  }
+  // Constructor for message fields.
+  RepeatedFieldRefIterator(const void* data,
+                           const RepeatedFieldAccessor* accessor,
+                           bool begin,
+                           AccessorValueType* scratch_space)
+      : data_(data), accessor_(accessor),
+        iterator_(begin ? accessor->BeginIterator(data) :
+                          accessor->EndIterator(data)),
+        scratch_space_(scratch_space) {
+  }
+  ~RepeatedFieldRefIterator() {
+    accessor_->DeleteIterator(data_, iterator_);
+  }
+  RepeatedFieldRefIterator operator++(int) {
+    RepeatedFieldRefIterator tmp(*this);
+    iterator_ = accessor_->AdvanceIterator(data_, iterator_);
+    return tmp;
+  }
+  RepeatedFieldRefIterator& operator++() {
+    iterator_ = accessor_->AdvanceIterator(data_, iterator_);
+    return *this;
+  }
+  IteratorValueType operator*() const {
+    return static_cast<IteratorValueType>(
+        *static_cast<const AccessorValueType*>(
+            accessor_->GetIteratorValue(
+                data_, iterator_, scratch_space_.get())));
+  }
+  IteratorPointerType operator->() const {
+    return static_cast<IteratorPointerType>(
+        accessor_->GetIteratorValue(
+            data_, iterator_, scratch_space_.get()));
+  }
+  bool operator!=(const RepeatedFieldRefIterator& other) const {
+    assert(data_ == other.data_);
+    assert(accessor_ == other.accessor_);
+    return !accessor_->EqualsIterator(data_, iterator_, other.iterator_);
+  }
+  bool operator==(const RepeatedFieldRefIterator& other) const {
+    return !this->operator!=(other);
+  }
+
+  RepeatedFieldRefIterator(const RepeatedFieldRefIterator& other)
+      : data_(other.data_), accessor_(other.accessor_),
+        iterator_(accessor_->CopyIterator(data_, other.iterator_)) {
+  }
+  RepeatedFieldRefIterator& operator=(const RepeatedFieldRefIterator& other) {
+    if (this != &other) {
+      accessor_->DeleteIterator(data_, iterator_);
+      data_ = other.data_;
+      accessor_ = other.accessor_;
+      iterator_ = accessor_->CopyIterator(data_, other.iterator_);
+    }
+    return *this;
+  }
+
+ protected:
+  const void* data_;
+  const RepeatedFieldAccessor* accessor_;
+  void* iterator_;
+  scoped_ptr<AccessorValueType> scratch_space_;
+};
+
+// TypeTraits that maps the type parameter T of RepeatedFieldRef or
+// MutableRepeatedFieldRef to corresponding iterator type,
+// RepeatedFieldAccessor type, etc.
+template<typename T>
+struct PrimitiveTraits {
+  static const bool is_primitive = false;
+};
+#define DEFINE_PRIMITIVE(TYPE, type) \
+    template<> struct PrimitiveTraits<type> { \
+      static const bool is_primitive = true; \
+      static const FieldDescriptor::CppType cpp_type = \
+          FieldDescriptor::CPPTYPE_ ## TYPE; \
+    };
+DEFINE_PRIMITIVE(INT32, int32)
+DEFINE_PRIMITIVE(UINT32, uint32)
+DEFINE_PRIMITIVE(INT64, int64)
+DEFINE_PRIMITIVE(UINT64, uint64)
+DEFINE_PRIMITIVE(FLOAT, float)
+DEFINE_PRIMITIVE(DOUBLE, double)
+DEFINE_PRIMITIVE(BOOL, bool)
+#undef DEFINE_PRIMITIVE
+
+template<typename T>
+struct RefTypeTraits<
+    T, typename internal::enable_if<PrimitiveTraits<T>::is_primitive>::type> {
+  typedef RepeatedFieldRefIterator<T> iterator;
+  typedef RepeatedFieldAccessor AccessorType;
+  typedef T AccessorValueType;
+  typedef T IteratorValueType;
+  typedef T* IteratorPointerType;
+  static const FieldDescriptor::CppType cpp_type =
+      PrimitiveTraits<T>::cpp_type;
+  static const Descriptor* GetMessageFieldDescriptor() {
+    return NULL;
+  }
+};
+
+template<typename T>
+struct RefTypeTraits<
+    T, typename internal::enable_if<internal::is_enum<T>::value>::type> {
+  typedef RepeatedFieldRefIterator<T> iterator;
+  typedef RepeatedFieldAccessor AccessorType;
+  // We use int32 for repeated enums in RepeatedFieldAccessor.
+  typedef int32 AccessorValueType;
+  typedef T IteratorValueType;
+  typedef int32* IteratorPointerType;
+  static const FieldDescriptor::CppType cpp_type =
+      FieldDescriptor::CPPTYPE_ENUM;
+  static const Descriptor* GetMessageFieldDescriptor() {
+    return NULL;
+  }
+};
+
+template<typename T>
+struct RefTypeTraits<
+    T, typename internal::enable_if<internal::is_same<string, T>::value>::type> {
+  typedef RepeatedFieldRefIterator<T> iterator;
+  typedef RepeatedFieldAccessor AccessorType;
+  typedef string AccessorValueType;
+  typedef string IteratorValueType;
+  typedef string* IteratorPointerType;
+  static const FieldDescriptor::CppType cpp_type =
+      FieldDescriptor::CPPTYPE_STRING;
+  static const Descriptor* GetMessageFieldDescriptor() {
+    return NULL;
+  }
+};
+
+template<typename T>
+struct MessageDescriptorGetter {
+  static const Descriptor* get() {
+    return T::default_instance().GetDescriptor();
+  }
+};
+template<>
+struct MessageDescriptorGetter<Message> {
+  static const Descriptor* get() {
+    return NULL;
+  }
+};
+
+template<typename T>
+struct RefTypeTraits<
+    T, typename internal::enable_if<internal::is_base_of<Message, T>::value>::type> {
+  typedef RepeatedFieldRefIterator<T> iterator;
+  typedef RepeatedFieldAccessor AccessorType;
+  typedef Message AccessorValueType;
+  typedef const T& IteratorValueType;
+  typedef const T* IteratorPointerType;
+  static const FieldDescriptor::CppType cpp_type =
+      FieldDescriptor::CPPTYPE_MESSAGE;
+  static const Descriptor* GetMessageFieldDescriptor() {
+    return MessageDescriptorGetter<T>::get();
+  }
+};
+}  // namespace internal
+}  // namespace protobuf
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_REPEATED_FIELD_REFLECTION_H__
diff --git a/src/google/protobuf/repeated_field_reflection_unittest.cc b/src/google/protobuf/repeated_field_reflection_unittest.cc
index 62833aab..98c864d3 100644
--- a/src/google/protobuf/repeated_field_reflection_unittest.cc
+++ b/src/google/protobuf/repeated_field_reflection_unittest.cc
@@ -33,10 +33,12 @@
 // Test reflection methods for aggregate access to Repeated[Ptr]Fields.
 // This test proto2 methods on a proto2 layout.
 
-#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/casts.h>
 #include <google/protobuf/stubs/stringprintf.h>
+#include <google/protobuf/dynamic_message.h>
 #include <google/protobuf/unittest.pb.h>
 #include <google/protobuf/test_util.h>
+#include <google/protobuf/reflection.h>
 #include <gtest/gtest.h>
 
 namespace google {
@@ -58,7 +60,6 @@ static string StrFunc(int i, int j) {
   return str;
 }
 
-
 TEST(RepeatedFieldReflectionTest, RegularFields) {
   TestAllTypes message;
   const Reflection* refl = message.GetReflection();
@@ -113,7 +114,7 @@ TEST(RepeatedFieldReflectionTest, RegularFields) {
       refl->MutableRepeatedPtrField<Message>(
           &message, fd_repeated_foreign_message);
 
-  // Make sure we can do get and sets through the Repeated[Ptr]Field objects.
+  // Make sure we can do gets and sets through the Repeated[Ptr]Field objects.
   for (int i = 0; i < 10; ++i) {
     // Check gets through const objects.
     EXPECT_EQ(rf_int32.Get(i), Func(i, 1));
@@ -158,8 +159,6 @@ TEST(RepeatedFieldReflectionTest, RegularFields) {
 }
 
 
-
-
 TEST(RepeatedFieldReflectionTest, ExtensionFields) {
   TestAllExtensions extended_message;
   const Reflection* refl = extended_message.GetReflection();
@@ -190,6 +189,515 @@ TEST(RepeatedFieldReflectionTest, ExtensionFields) {
   }
 }
 
+template<typename Ref, typename MessageType, typename ValueType>
+void TestRepeatedFieldRefIterator(
+    const Ref& handle, const MessageType& message,
+    ValueType (MessageType::*GetFunc)(int) const) {
+  int index = 0;
+  for (typename Ref::const_iterator it = handle.begin();
+       it != handle.end(); ++it) {
+    ValueType value = static_cast<ValueType>(*it);
+    EXPECT_EQ((message.*GetFunc)(index), value);
+    ++index;
+  }
+  EXPECT_EQ(handle.size(), index);
+}
+
+TEST(RepeatedFieldReflectionTest, RepeatedFieldRefForRegularFields) {
+  TestAllTypes message;
+  const Reflection* refl = message.GetReflection();
+  const Descriptor* desc = message.GetDescriptor();
+
+  for (int i = 0; i < 10; ++i) {
+    message.add_repeated_int32(Func(i, 1));
+    message.add_repeated_double(Func(i, 2));
+    message.add_repeated_string(StrFunc(i, 5));
+    message.add_repeated_foreign_message()->set_c(Func(i, 6));
+  }
+
+  // Get FieldDescriptors for all the fields of interest.
+  const FieldDescriptor* fd_repeated_int32 =
+      desc->FindFieldByName("repeated_int32");
+  const FieldDescriptor* fd_repeated_double =
+      desc->FindFieldByName("repeated_double");
+  const FieldDescriptor* fd_repeated_string =
+      desc->FindFieldByName("repeated_string");
+  const FieldDescriptor* fd_repeated_foreign_message =
+      desc->FindFieldByName("repeated_foreign_message");
+
+  // Get RepeatedFieldRef objects for all fields of interest.
+  const RepeatedFieldRef<int32> rf_int32 =
+      refl->GetRepeatedFieldRef<int32>(message, fd_repeated_int32);
+  const RepeatedFieldRef<double> rf_double =
+      refl->GetRepeatedFieldRef<double>(message, fd_repeated_double);
+  const RepeatedFieldRef<string> rf_string =
+      refl->GetRepeatedFieldRef<string>(message, fd_repeated_string);
+  const RepeatedFieldRef<ForeignMessage> rf_foreign_message =
+      refl->GetRepeatedFieldRef<ForeignMessage>(
+          message, fd_repeated_foreign_message);
+  const RepeatedFieldRef<Message> rf_message =
+      refl->GetRepeatedFieldRef<Message>(
+          message, fd_repeated_foreign_message);
+
+  // Get MutableRepeatedFieldRef objects for all fields of interest.
+  const MutableRepeatedFieldRef<int32> mrf_int32 =
+      refl->GetMutableRepeatedFieldRef<int32>(&message, fd_repeated_int32);
+  const MutableRepeatedFieldRef<double> mrf_double =
+      refl->GetMutableRepeatedFieldRef<double>(&message, fd_repeated_double);
+  const MutableRepeatedFieldRef<string> mrf_string =
+      refl->GetMutableRepeatedFieldRef<string>(&message, fd_repeated_string);
+  const MutableRepeatedFieldRef<ForeignMessage> mrf_foreign_message =
+      refl->GetMutableRepeatedFieldRef<ForeignMessage>(
+          &message, fd_repeated_foreign_message);
+  const MutableRepeatedFieldRef<Message> mrf_message =
+      refl->GetMutableRepeatedFieldRef<Message>(
+          &message, fd_repeated_foreign_message);
+
+  EXPECT_EQ(message.repeated_int32_size(), rf_int32.size());
+  EXPECT_EQ(message.repeated_int32_size(), mrf_int32.size());
+  EXPECT_EQ(message.repeated_double_size(), rf_double.size());
+  EXPECT_EQ(message.repeated_double_size(), mrf_double.size());
+  EXPECT_EQ(message.repeated_string_size(), rf_string.size());
+  EXPECT_EQ(message.repeated_string_size(), mrf_string.size());
+  EXPECT_EQ(message.repeated_foreign_message_size(),
+            rf_foreign_message.size());
+  EXPECT_EQ(message.repeated_foreign_message_size(),
+            mrf_foreign_message.size());
+  EXPECT_EQ(message.repeated_foreign_message_size(), rf_message.size());
+  EXPECT_EQ(message.repeated_foreign_message_size(), mrf_message.size());
+
+  EXPECT_FALSE(rf_int32.empty());
+  EXPECT_FALSE(mrf_int32.empty());
+  EXPECT_FALSE(rf_double.empty());
+  EXPECT_FALSE(mrf_double.empty());
+  EXPECT_FALSE(rf_string.empty());
+  EXPECT_FALSE(mrf_string.empty());
+  EXPECT_FALSE(rf_foreign_message.empty());
+  EXPECT_FALSE(mrf_foreign_message.empty());
+  EXPECT_FALSE(rf_message.empty());
+  EXPECT_FALSE(mrf_message.empty());
+
+  // Make sure we can do gets and sets through the RepeatedFieldRef objects.
+  for (int i = 0; i < 10; ++i) {
+    // Check gets through const objects.
+    EXPECT_EQ(rf_int32.Get(i), Func(i, 1));
+    EXPECT_EQ(rf_double.Get(i), Func(i, 2));
+    EXPECT_EQ(rf_string.Get(i), StrFunc(i, 5));
+    ForeignMessage scratch_space;
+    EXPECT_EQ(rf_foreign_message.Get(i, &scratch_space).c(), Func(i, 6));
+    EXPECT_EQ(down_cast<const ForeignMessage&>(
+        rf_message.Get(i, &scratch_space)).c(), Func(i, 6));
+
+    // Check gets through mutable objects.
+    EXPECT_EQ(mrf_int32.Get(i), Func(i, 1));
+    EXPECT_EQ(mrf_double.Get(i), Func(i, 2));
+    EXPECT_EQ(mrf_string.Get(i), StrFunc(i, 5));
+    EXPECT_EQ(mrf_foreign_message.Get(i, &scratch_space).c(), Func(i, 6));
+    EXPECT_EQ(down_cast<const ForeignMessage&>(
+        mrf_message.Get(i, &scratch_space)).c(), Func(i, 6));
+
+    // Check sets through mutable objects.
+    mrf_int32.Set(i, Func(i, -1));
+    mrf_double.Set(i, Func(i, -2));
+    mrf_string.Set(i, StrFunc(i, -5));
+    ForeignMessage foreign_message;
+    foreign_message.set_c(Func(i, -6));
+    mrf_foreign_message.Set(i, foreign_message);
+    EXPECT_EQ(message.repeated_int32(i), Func(i, -1));
+    EXPECT_EQ(message.repeated_double(i), Func(i, -2));
+    EXPECT_EQ(message.repeated_string(i), StrFunc(i, -5));
+    EXPECT_EQ(message.repeated_foreign_message(i).c(), Func(i, -6));
+    foreign_message.set_c(Func(i, 7));
+    mrf_message.Set(i, foreign_message);
+    EXPECT_EQ(message.repeated_foreign_message(i).c(), Func(i, 7));
+  }
+
+  // Test iterators.
+  TestRepeatedFieldRefIterator(rf_int32, message,
+                               &TestAllTypes::repeated_int32);
+  TestRepeatedFieldRefIterator(rf_double, message,
+                               &TestAllTypes::repeated_double);
+  TestRepeatedFieldRefIterator(rf_string, message,
+                               &TestAllTypes::repeated_string);
+
+  // Test iterators for message fields.
+  typedef RepeatedFieldRef<ForeignMessage>::iterator MessageIterator;
+  int index = 0;
+  for (MessageIterator it = rf_foreign_message.begin();
+       it != rf_foreign_message.end(); ++it) {
+    EXPECT_EQ(message.repeated_foreign_message(index).c(), it->c());
+    ++index;
+  }
+  EXPECT_EQ(10, index);
+
+  // Test iterator operators that are not ususally used in regular for-loops.
+  // Including: post increment, assign, ==.
+  MessageIterator old_it = rf_foreign_message.begin();
+  MessageIterator new_it = old_it++;
+  EXPECT_FALSE(old_it == new_it);
+  // Check that old_it++ increments old_it once.
+  for (index = 1; old_it != rf_foreign_message.end(); ++old_it, ++index) {
+    EXPECT_EQ(message.repeated_foreign_message(index).c(), old_it->c());
+  }
+  EXPECT_EQ(10, index);
+  // Test assign operator.
+  old_it = new_it;
+  for (index = 0; old_it != rf_foreign_message.end(); ++old_it, ++index) {
+    EXPECT_EQ(message.repeated_foreign_message(index).c(), old_it->c());
+  }
+  EXPECT_EQ(10, index);
+  // Check that the returned value of old_it++ is the one before increment.
+  for (index = 0; new_it != rf_foreign_message.end(); ++new_it, ++index) {
+    EXPECT_EQ(message.repeated_foreign_message(index).c(), new_it->c());
+  }
+  EXPECT_EQ(10, index);
+
+  // Test MutableRepeatedFieldRef::Add()
+  mrf_int32.Add(1234);
+  mrf_double.Add(1234.0);
+  mrf_string.Add("1234");
+  ForeignMessage foreign_message;
+  foreign_message.set_c(1234);
+  mrf_foreign_message.Add(foreign_message);
+  EXPECT_EQ(1234, message.repeated_int32(10));
+  EXPECT_EQ(1234.0, message.repeated_double(10));
+  EXPECT_EQ("1234", message.repeated_string(10));
+  EXPECT_EQ(1234, message.repeated_foreign_message(10).c());
+
+  // Test MutableRepeatedFieldRef::RemoveLast()
+  mrf_int32.RemoveLast();
+  mrf_double.RemoveLast();
+  mrf_string.RemoveLast();
+  mrf_foreign_message.RemoveLast();
+  EXPECT_EQ(10, message.repeated_int32_size());
+  EXPECT_EQ(10, message.repeated_double_size());
+  EXPECT_EQ(10, message.repeated_string_size());
+  EXPECT_EQ(10, message.repeated_foreign_message_size());
+
+  // Test MutableRepeatedFieldRef::SwapElements()
+  mrf_int32.SwapElements(0, 9);
+  mrf_double.SwapElements(0, 9);
+  mrf_string.SwapElements(0, 9);
+  mrf_foreign_message.SwapElements(0, 9);
+  EXPECT_EQ(Func(9, -1), message.repeated_int32(0));
+  EXPECT_EQ(Func(0, -1), message.repeated_int32(9));
+  EXPECT_EQ(Func(9, -2), message.repeated_double(0));
+  EXPECT_EQ(Func(0, -2), message.repeated_double(9));
+  EXPECT_EQ(StrFunc(9, -5), message.repeated_string(0));
+  EXPECT_EQ(StrFunc(0, -5), message.repeated_string(9));
+  EXPECT_EQ(Func(9, 7), message.repeated_foreign_message(0).c());
+  EXPECT_EQ(Func(0, 7), message.repeated_foreign_message(9).c());
+
+  // Test MutableRepeatedFieldRef::Clear()
+  mrf_int32.Clear();
+  mrf_double.Clear();
+  mrf_string.Clear();
+  mrf_foreign_message.Clear();
+  EXPECT_EQ(0, message.repeated_int32_size());
+  EXPECT_EQ(0, message.repeated_double_size());
+  EXPECT_EQ(0, message.repeated_string_size());
+  EXPECT_EQ(0, message.repeated_foreign_message_size());
+
+  // Test (Mutable)RepeatedFieldRef::empty()
+  EXPECT_TRUE(rf_int32.empty());
+  EXPECT_TRUE(mrf_int32.empty());
+  EXPECT_TRUE(rf_double.empty());
+  EXPECT_TRUE(mrf_double.empty());
+  EXPECT_TRUE(rf_string.empty());
+  EXPECT_TRUE(mrf_string.empty());
+  EXPECT_TRUE(rf_foreign_message.empty());
+  EXPECT_TRUE(mrf_foreign_message.empty());
+  EXPECT_TRUE(rf_message.empty());
+  EXPECT_TRUE(mrf_message.empty());
+
+  // Make sure types are checked correctly at runtime.
+  const FieldDescriptor* fd_optional_int32 =
+      desc->FindFieldByName("optional_int32");
+  EXPECT_DEATH(refl->GetRepeatedFieldRef<int32>(
+      message, fd_optional_int32), "");
+  EXPECT_DEATH(refl->GetRepeatedFieldRef<double>(
+      message, fd_repeated_int32), "");
+  EXPECT_DEATH(refl->GetRepeatedFieldRef<TestAllTypes>(
+      message, fd_repeated_foreign_message), "");
+}
+
+TEST(RepeatedFieldReflectionTest, RepeatedFieldRefForEnums) {
+  TestAllTypes message;
+  const Reflection* refl = message.GetReflection();
+  const Descriptor* desc = message.GetDescriptor();
+
+  for (int i = 0; i < 10; ++i) {
+    message.add_repeated_nested_enum(TestAllTypes::BAR);
+  }
+
+  const FieldDescriptor* fd_repeated_nested_enum =
+      desc->FindFieldByName("repeated_nested_enum");
+  const RepeatedFieldRef<TestAllTypes::NestedEnum> enum_ref =
+      refl->GetRepeatedFieldRef<TestAllTypes::NestedEnum>(
+          message, fd_repeated_nested_enum);
+  const MutableRepeatedFieldRef<TestAllTypes::NestedEnum>
+  mutable_enum_ref =
+      refl->GetMutableRepeatedFieldRef<TestAllTypes::NestedEnum>(
+          &message, fd_repeated_nested_enum);
+  const RepeatedFieldRef<int32> int32_ref =
+      refl->GetRepeatedFieldRef<int32>(
+          message, fd_repeated_nested_enum);
+  const MutableRepeatedFieldRef<int32> mutable_int32_ref =
+      refl->GetMutableRepeatedFieldRef<int32>(
+          &message, fd_repeated_nested_enum);
+
+  EXPECT_EQ(message.repeated_nested_enum_size(), enum_ref.size());
+  EXPECT_EQ(message.repeated_nested_enum_size(), mutable_enum_ref.size());
+  EXPECT_EQ(message.repeated_nested_enum_size(), int32_ref.size());
+  EXPECT_EQ(message.repeated_nested_enum_size(), mutable_int32_ref.size());
+
+  EXPECT_FALSE(enum_ref.empty());
+  EXPECT_FALSE(mutable_enum_ref.empty());
+  EXPECT_FALSE(int32_ref.empty());
+  EXPECT_FALSE(mutable_int32_ref.empty());
+
+  for (int i = 0; i < 10; ++i) {
+    EXPECT_EQ(TestAllTypes::BAR, enum_ref.Get(i));
+    EXPECT_EQ(TestAllTypes::BAR, mutable_enum_ref.Get(i));
+    mutable_enum_ref.Set(i, TestAllTypes::BAZ);
+    EXPECT_EQ(TestAllTypes::BAZ, enum_ref.Get(i));
+    EXPECT_EQ(TestAllTypes::BAZ, message.repeated_nested_enum(i));
+
+    message.set_repeated_nested_enum(i, TestAllTypes::BAR);
+    EXPECT_EQ(TestAllTypes::BAR, int32_ref.Get(i));
+    EXPECT_EQ(TestAllTypes::BAR, mutable_int32_ref.Get(i));
+    mutable_int32_ref.Set(i, TestAllTypes::BAZ);
+    EXPECT_EQ(TestAllTypes::BAZ, int32_ref.Get(i));
+    EXPECT_EQ(TestAllTypes::BAZ, message.repeated_nested_enum(i));
+  }
+
+  TestRepeatedFieldRefIterator(enum_ref, message,
+                               &TestAllTypes::repeated_nested_enum);
+  TestRepeatedFieldRefIterator(int32_ref, message,
+                               &TestAllTypes::repeated_nested_enum);
+
+  // Test Add()
+  mutable_enum_ref.Add(TestAllTypes::FOO);
+  EXPECT_EQ(TestAllTypes::FOO, message.repeated_nested_enum(10));
+  mutable_int32_ref.Add(TestAllTypes::BAR);
+  EXPECT_EQ(TestAllTypes::BAR, message.repeated_nested_enum(11));
+
+  // Test RemoveLast()
+  mutable_enum_ref.RemoveLast();
+  EXPECT_EQ(11, message.repeated_nested_enum_size());
+  mutable_int32_ref.RemoveLast();
+  EXPECT_EQ(10, message.repeated_nested_enum_size());
+
+  // Test SwapElements()
+  mutable_enum_ref.Set(0, TestAllTypes::BAR);
+  mutable_enum_ref.Set(9, TestAllTypes::BAZ);
+  mutable_enum_ref.SwapElements(0, 9);
+  EXPECT_EQ(TestAllTypes::BAZ, enum_ref.Get(0));
+  EXPECT_EQ(TestAllTypes::BAR, enum_ref.Get(9));
+  mutable_int32_ref.SwapElements(0, 9);
+  EXPECT_EQ(TestAllTypes::BAR, enum_ref.Get(0));
+  EXPECT_EQ(TestAllTypes::BAZ, enum_ref.Get(9));
+
+  // Test Clear()
+  mutable_enum_ref.Clear();
+  EXPECT_EQ(0, message.repeated_nested_enum_size());
+  mutable_enum_ref.Add(TestAllTypes::FOO);
+  EXPECT_EQ(1, message.repeated_nested_enum_size());
+  mutable_int32_ref.Clear();
+  EXPECT_EQ(0, message.repeated_nested_enum_size());
+
+  // Test empty()
+  EXPECT_TRUE(enum_ref.empty());
+  EXPECT_TRUE(mutable_enum_ref.empty());
+  EXPECT_TRUE(int32_ref.empty());
+  EXPECT_TRUE(mutable_int32_ref.empty());
+}
+
+TEST(RepeatedFieldReflectionTest, RepeatedFieldRefForExtensionFields) {
+  TestAllExtensions extended_message;
+  const Reflection* refl = extended_message.GetReflection();
+  const Descriptor* desc = extended_message.GetDescriptor();
+
+  for (int i = 0; i < 10; ++i) {
+    extended_message.AddExtension(
+        unittest::repeated_int64_extension, Func(i, 1));
+  }
+
+  const FieldDescriptor* fd_repeated_int64_extension =
+      desc->file()->FindExtensionByName("repeated_int64_extension");
+  GOOGLE_CHECK(fd_repeated_int64_extension != NULL);
+
+  const RepeatedFieldRef<int64> rf_int64_extension =
+      refl->GetRepeatedFieldRef<int64>(extended_message,
+                                          fd_repeated_int64_extension);
+
+  const MutableRepeatedFieldRef<int64> mrf_int64_extension =
+      refl->GetMutableRepeatedFieldRef<int64>(&extended_message,
+                                                 fd_repeated_int64_extension);
+
+  for (int i = 0; i < 10; ++i) {
+    EXPECT_EQ(Func(i, 1), rf_int64_extension.Get(i));
+    mrf_int64_extension.Set(i, Func(i, -1));
+    EXPECT_EQ(Func(i, -1),
+        extended_message.GetExtension(unittest::repeated_int64_extension, i));
+  }
+}
+
+
+TEST(RepeatedFieldReflectionTest, RepeatedFieldRefMergeFromAndSwap) {
+  // Set-up message content.
+  TestAllTypes m0, m1, m2;
+  for (int i = 0; i < 10; ++i) {
+    m0.add_repeated_int32(Func(i, 1));
+    m0.add_repeated_double(Func(i, 2));
+    m0.add_repeated_string(StrFunc(i, 5));
+    m0.add_repeated_foreign_message()->set_c(Func(i, 6));
+    m0.add_repeated_nested_enum(TestAllTypes::FOO);
+    m1.add_repeated_int32(Func(i, 11));
+    m1.add_repeated_double(Func(i, 12));
+    m1.add_repeated_string(StrFunc(i, 15));
+    m1.add_repeated_foreign_message()->set_c(Func(i, 16));
+    m1.add_repeated_nested_enum(TestAllTypes::BAR);
+    m2.add_repeated_int32(Func(i, 21));
+    m2.add_repeated_double(Func(i, 22));
+    m2.add_repeated_string(StrFunc(i, 25));
+    m2.add_repeated_foreign_message()->set_c(Func(i, 26));
+    m2.add_repeated_nested_enum(TestAllTypes::BAZ);
+  }
+
+  const Reflection* refl = m0.GetReflection();
+  const Descriptor* desc = m0.GetDescriptor();
+
+  // Get FieldDescriptors for all the fields of interest.
+  const FieldDescriptor* fd_repeated_int32 =
+      desc->FindFieldByName("repeated_int32");
+  const FieldDescriptor* fd_repeated_double =
+      desc->FindFieldByName("repeated_double");
+  const FieldDescriptor* fd_repeated_string =
+      desc->FindFieldByName("repeated_string");
+  const FieldDescriptor* fd_repeated_foreign_message =
+      desc->FindFieldByName("repeated_foreign_message");
+  const FieldDescriptor* fd_repeated_nested_enum =
+      desc->FindFieldByName("repeated_nested_enum");
+
+  // Get MutableRepeatedFieldRef objects for all fields of interest.
+  const MutableRepeatedFieldRef<int32> mrf_int32 =
+      refl->GetMutableRepeatedFieldRef<int32>(&m0, fd_repeated_int32);
+  const MutableRepeatedFieldRef<double> mrf_double =
+      refl->GetMutableRepeatedFieldRef<double>(&m0, fd_repeated_double);
+  const MutableRepeatedFieldRef<string> mrf_string =
+      refl->GetMutableRepeatedFieldRef<string>(&m0, fd_repeated_string);
+  const MutableRepeatedFieldRef<ForeignMessage> mrf_foreign_message =
+      refl->GetMutableRepeatedFieldRef<ForeignMessage>(
+          &m0, fd_repeated_foreign_message);
+  const MutableRepeatedFieldRef<TestAllTypes::NestedEnum>
+  mrf_nested_enum =
+      refl->GetMutableRepeatedFieldRef<TestAllTypes::NestedEnum>(
+          &m0, fd_repeated_nested_enum);
+
+  // Test MutableRepeatedRef::CopyFrom
+  mrf_int32.CopyFrom(
+      refl->GetRepeatedFieldRef<int32>(m1, fd_repeated_int32));
+  mrf_double.CopyFrom(
+      refl->GetRepeatedFieldRef<double>(m1, fd_repeated_double));
+  mrf_string.CopyFrom(
+      refl->GetRepeatedFieldRef<string>(m1, fd_repeated_string));
+  mrf_foreign_message.CopyFrom(
+      refl->GetRepeatedFieldRef<ForeignMessage>(
+          m1, fd_repeated_foreign_message));
+  mrf_nested_enum.CopyFrom(
+      refl->GetRepeatedFieldRef<TestAllTypes::NestedEnum>(
+          m1, fd_repeated_nested_enum));
+  for (int i = 0; i < 10; ++i) {
+    EXPECT_EQ(Func(i, 11), m0.repeated_int32(i));
+    EXPECT_EQ(Func(i, 12), m0.repeated_double(i));
+    EXPECT_EQ(StrFunc(i, 15), m0.repeated_string(i));
+    EXPECT_EQ(Func(i, 16), m0.repeated_foreign_message(i).c());
+    EXPECT_EQ(TestAllTypes::BAR, m0.repeated_nested_enum(i));
+  }
+
+  // Test MutableRepeatedRef::MergeFrom
+  mrf_int32.MergeFrom(
+      refl->GetRepeatedFieldRef<int32>(m2, fd_repeated_int32));
+  mrf_double.MergeFrom(
+      refl->GetRepeatedFieldRef<double>(m2, fd_repeated_double));
+  mrf_string.MergeFrom(
+      refl->GetRepeatedFieldRef<string>(m2, fd_repeated_string));
+  mrf_foreign_message.MergeFrom(
+      refl->GetRepeatedFieldRef<ForeignMessage>(
+          m2, fd_repeated_foreign_message));
+  mrf_nested_enum.MergeFrom(
+      refl->GetRepeatedFieldRef<TestAllTypes::NestedEnum>(
+          m2, fd_repeated_nested_enum));
+  for (int i = 0; i < 10; ++i) {
+    EXPECT_EQ(Func(i, 21), m0.repeated_int32(i + 10));
+    EXPECT_EQ(Func(i, 22), m0.repeated_double(i + 10));
+    EXPECT_EQ(StrFunc(i, 25), m0.repeated_string(i + 10));
+    EXPECT_EQ(Func(i, 26), m0.repeated_foreign_message(i + 10).c());
+    EXPECT_EQ(TestAllTypes::BAZ, m0.repeated_nested_enum(i + 10));
+  }
+
+  // Test MutableRepeatedRef::Swap
+  // Swap between m0 and m2.
+  mrf_int32.Swap(
+      refl->GetMutableRepeatedFieldRef<int32>(&m2, fd_repeated_int32));
+  mrf_double.Swap(
+      refl->GetMutableRepeatedFieldRef<double>(&m2, fd_repeated_double));
+  mrf_string.Swap(
+      refl->GetMutableRepeatedFieldRef<string>(&m2, fd_repeated_string));
+  mrf_foreign_message.Swap(
+      refl->GetMutableRepeatedFieldRef<ForeignMessage>(
+          &m2, fd_repeated_foreign_message));
+  mrf_nested_enum.Swap(
+      refl->GetMutableRepeatedFieldRef<TestAllTypes::NestedEnum>(
+          &m2, fd_repeated_nested_enum));
+  for (int i = 0; i < 10; ++i) {
+    // Check the content of m0.
+    EXPECT_EQ(Func(i, 21), m0.repeated_int32(i));
+    EXPECT_EQ(Func(i, 22), m0.repeated_double(i));
+    EXPECT_EQ(StrFunc(i, 25), m0.repeated_string(i));
+    EXPECT_EQ(Func(i, 26), m0.repeated_foreign_message(i).c());
+    EXPECT_EQ(TestAllTypes::BAZ, m0.repeated_nested_enum(i));
+
+    // Check the content of m2.
+    EXPECT_EQ(Func(i, 11), m2.repeated_int32(i));
+    EXPECT_EQ(Func(i, 12), m2.repeated_double(i));
+    EXPECT_EQ(StrFunc(i, 15), m2.repeated_string(i));
+    EXPECT_EQ(Func(i, 16), m2.repeated_foreign_message(i).c());
+    EXPECT_EQ(TestAllTypes::BAR, m2.repeated_nested_enum(i));
+    EXPECT_EQ(Func(i, 21), m2.repeated_int32(i + 10));
+    EXPECT_EQ(Func(i, 22), m2.repeated_double(i + 10));
+    EXPECT_EQ(StrFunc(i, 25), m2.repeated_string(i + 10));
+    EXPECT_EQ(Func(i, 26), m2.repeated_foreign_message(i + 10).c());
+    EXPECT_EQ(TestAllTypes::BAZ, m2.repeated_nested_enum(i + 10));
+  }
+}
+
+// Test that GetRepeatedFieldRef/MutableRepeatedFieldRef works with
+// DynamicMessage.
+TEST(RepeatedFieldReflectionTest, RepeatedFieldRefDynamicMessage) {
+  // DynamicMessage shares the same memory layout as generated message
+  // and use the same GeneratedMessageReflection code for reflection.
+  // All code paths should already be covered by the other tests for
+  // generated messages. Here we just test one field.
+
+  const Descriptor* desc = TestAllTypes::descriptor();
+  const FieldDescriptor* fd_repeated_int32 =
+      desc->FindFieldByName("repeated_int32");
+
+  DynamicMessageFactory factory;
+  scoped_ptr<Message> dynamic_message(factory.GetPrototype(desc)->New());
+  const Reflection* refl = dynamic_message->GetReflection();
+
+  MutableRepeatedFieldRef<int32> rf_int32 =
+      refl->GetMutableRepeatedFieldRef<int32>(
+          dynamic_message.get(), fd_repeated_int32);
+  rf_int32.Add(1234);
+  EXPECT_EQ(1, refl->FieldSize(*dynamic_message, fd_repeated_int32));
+  EXPECT_EQ(1234, refl->GetRepeatedInt32(*dynamic_message,
+                                         fd_repeated_int32, 0));
+}
+
 }  // namespace
 }  // namespace protobuf
 }  // namespace google
diff --git a/src/google/protobuf/repeated_field_unittest.cc b/src/google/protobuf/repeated_field_unittest.cc
index f4d48f59..9942af50 100644
--- a/src/google/protobuf/repeated_field_unittest.cc
+++ b/src/google/protobuf/repeated_field_unittest.cc
@@ -92,7 +92,8 @@ TEST(RepeatedField, Small) {
 
   EXPECT_TRUE(field.empty());
   EXPECT_EQ(field.size(), 0);
-  int expected_usage = 4 * sizeof(int);
+  // Additional 8 bytes are for 'struct Rep' header.
+  int expected_usage = 4 * sizeof(int) + 8;
   EXPECT_EQ(field.SpaceUsedExcludingSelf(), expected_usage);
 }
 
@@ -295,6 +296,39 @@ TEST(RepeatedField, CopyFromSelf) {
   EXPECT_EQ(3, me.Get(0));
 }
 
+TEST(RepeatedField, Erase) {
+  RepeatedField<int> me;
+  RepeatedField<int>::iterator it = me.erase(me.begin(), me.end());
+  EXPECT_TRUE(me.begin() == it);
+  EXPECT_EQ(0, me.size());
+
+  me.Add(1);
+  me.Add(2);
+  me.Add(3);
+  it = me.erase(me.begin(), me.end());
+  EXPECT_TRUE(me.begin() == it);
+  EXPECT_EQ(0, me.size());
+
+  me.Add(4);
+  me.Add(5);
+  me.Add(6);
+  it = me.erase(me.begin() + 2, me.end());
+  EXPECT_TRUE(me.begin() + 2 == it);
+  EXPECT_EQ(2, me.size());
+  EXPECT_EQ(4, me.Get(0));
+  EXPECT_EQ(5, me.Get(1));
+
+  me.Add(6);
+  me.Add(7);
+  me.Add(8);
+  it = me.erase(me.begin() + 1, me.begin() + 3);
+  EXPECT_TRUE(me.begin() + 1 == it);
+  EXPECT_EQ(3, me.size());
+  EXPECT_EQ(4, me.Get(0));
+  EXPECT_EQ(7, me.Get(1));
+  EXPECT_EQ(8, me.Get(2));
+}
+
 TEST(RepeatedField, CopyConstruct) {
   RepeatedField<int> source;
   source.Add(1);
@@ -741,6 +775,39 @@ TEST(RepeatedPtrField, CopyFromSelf) {
   EXPECT_EQ("1", me.Get(0));
 }
 
+TEST(RepeatedPtrField, Erase) {
+  RepeatedPtrField<string> me;
+  RepeatedPtrField<string>::iterator it = me.erase(me.begin(), me.end());
+  EXPECT_TRUE(me.begin() == it);
+  EXPECT_EQ(0, me.size());
+
+  *me.Add() = "1";
+  *me.Add() = "2";
+  *me.Add() = "3";
+  it = me.erase(me.begin(), me.end());
+  EXPECT_TRUE(me.begin() == it);
+  EXPECT_EQ(0, me.size());
+
+  *me.Add() = "4";
+  *me.Add() = "5";
+  *me.Add() = "6";
+  it = me.erase(me.begin() + 2, me.end());
+  EXPECT_TRUE(me.begin() + 2 == it);
+  EXPECT_EQ(2, me.size());
+  EXPECT_EQ("4", me.Get(0));
+  EXPECT_EQ("5", me.Get(1));
+
+  *me.Add() = "6";
+  *me.Add() = "7";
+  *me.Add() = "8";
+  it = me.erase(me.begin() + 1, me.begin() + 3);
+  EXPECT_TRUE(me.begin() + 1 == it);
+  EXPECT_EQ(3, me.size());
+  EXPECT_EQ("4", me.Get(0));
+  EXPECT_EQ("7", me.Get(1));
+  EXPECT_EQ("8", me.Get(2));
+}
+
 TEST(RepeatedPtrField, CopyConstruct) {
   RepeatedPtrField<string> source;
   source.Add()->assign("1");
diff --git a/src/google/protobuf/stubs/atomic_sequence_num.h b/src/google/protobuf/stubs/atomic_sequence_num.h
new file mode 100644
index 00000000..bb20942f
--- /dev/null
+++ b/src/google/protobuf/stubs/atomic_sequence_num.h
@@ -0,0 +1,54 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2014 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#ifndef GOOGLE_PROTOBUF_ATOMIC_SEQUENCE_NUM_H_
+#define GOOGLE_PROTOBUF_ATOMIC_SEQUENCE_NUM_H_
+
+#include <google/protobuf/stubs/atomicops.h>
+
+namespace google {
+namespace protobuf {
+namespace internal {
+
+class SequenceNumber {
+ public:
+  SequenceNumber() : word_(0) {}
+
+  AtomicWord GetNext() {
+    return NoBarrier_AtomicIncrement(&word_, 1) - 1;
+  }
+ private:
+  AtomicWord word_;
+};
+
+}  // namespace internal
+}  // namespace protobuf
+}  // namespace google
+
+#endif  // GOOGLE_PROTOBUF_ATOMIC_SEQUENCE_NUM_H_
diff --git a/src/google/protobuf/stubs/casts.h b/src/google/protobuf/stubs/casts.h
new file mode 100644
index 00000000..cccf65a1
--- /dev/null
+++ b/src/google/protobuf/stubs/casts.h
@@ -0,0 +1,123 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2014 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_CASTS_H__
+#define GOOGLE_PROTOBUF_CASTS_H__
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/type_traits.h>
+
+namespace google {
+namespace protobuf {
+namespace internal {
+// Use implicit_cast as a safe version of static_cast or const_cast
+// for upcasting in the type hierarchy (i.e. casting a pointer to Foo
+// to a pointer to SuperclassOfFoo or casting a pointer to Foo to
+// a const pointer to Foo).
+// When you use implicit_cast, the compiler checks that the cast is safe.
+// Such explicit implicit_casts are necessary in surprisingly many
+// situations where C++ demands an exact type match instead of an
+// argument type convertable to a target type.
+//
+// The From type can be inferred, so the preferred syntax for using
+// implicit_cast is the same as for static_cast etc.:
+//
+//   implicit_cast<ToType>(expr)
+//
+// implicit_cast would have been part of the C++ standard library,
+// but the proposal was submitted too late.  It will probably make
+// its way into the language in the future.
+template<typename To, typename From>
+inline To implicit_cast(From const &f) {
+  return f;
+}
+
+// When you upcast (that is, cast a pointer from type Foo to type
+// SuperclassOfFoo), it's fine to use implicit_cast<>, since upcasts
+// always succeed.  When you downcast (that is, cast a pointer from
+// type Foo to type SubclassOfFoo), static_cast<> isn't safe, because
+// how do you know the pointer is really of type SubclassOfFoo?  It
+// could be a bare Foo, or of type DifferentSubclassOfFoo.  Thus,
+// when you downcast, you should use this macro.  In debug mode, we
+// use dynamic_cast<> to double-check the downcast is legal (we die
+// if it's not).  In normal mode, we do the efficient static_cast<>
+// instead.  Thus, it's important to test in debug mode to make sure
+// the cast is legal!
+//    This is the only place in the code we should use dynamic_cast<>.
+// In particular, you SHOULDN'T be using dynamic_cast<> in order to
+// do RTTI (eg code like this:
+//    if (dynamic_cast<Subclass1>(foo)) HandleASubclass1Object(foo);
+//    if (dynamic_cast<Subclass2>(foo)) HandleASubclass2Object(foo);
+// You should design the code some other way not to need this.
+
+template<typename To, typename From>     // use like this: down_cast<T*>(foo);
+inline To down_cast(From* f) {                   // so we only accept pointers
+  // Ensures that To is a sub-type of From *.  This test is here only
+  // for compile-time type checking, and has no overhead in an
+  // optimized build at run-time, as it will be optimized away
+  // completely.
+  if (false) {
+    implicit_cast<From*, To>(0);
+  }
+
+#if !defined(NDEBUG) && !defined(GOOGLE_PROTOBUF_NO_RTTI)
+  assert(f == NULL || dynamic_cast<To>(f) != NULL);  // RTTI: debug mode only!
+#endif
+  return static_cast<To>(f);
+}
+
+template<typename To, typename From>    // use like this: down_cast<T&>(foo);
+inline To down_cast(From& f) {
+  typedef typename remove_reference<To>::type* ToAsPointer;
+  // Ensures that To is a sub-type of From *.  This test is here only
+  // for compile-time type checking, and has no overhead in an
+  // optimized build at run-time, as it will be optimized away
+  // completely.
+  if (false) {
+    implicit_cast<From*, ToAsPointer>(0);
+  }
+
+#if !defined(NDEBUG) && !defined(GOOGLE_PROTOBUF_NO_RTTI)
+  // RTTI: debug mode only!
+  assert(dynamic_cast<ToAsPointer>(&f) != NULL);
+#endif
+  return *static_cast<ToAsPointer>(&f);
+}
+
+}  // namespace internal
+
+// We made these internal so that they would show up as such in the docs,
+// but we don't want to stick "internal::" in front of them everywhere.
+using internal::implicit_cast;
+using internal::down_cast;
+
+}  // namespace protobuf
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_CASTS_H__
diff --git a/src/google/protobuf/stubs/common.cc b/src/google/protobuf/stubs/common.cc
index 1e02b228..54e00ccb 100644
--- a/src/google/protobuf/stubs/common.cc
+++ b/src/google/protobuf/stubs/common.cc
@@ -171,6 +171,7 @@ DECLARE_STREAM_OPERATOR(uint         , "%u" )
 DECLARE_STREAM_OPERATOR(long         , "%ld")
 DECLARE_STREAM_OPERATOR(unsigned long, "%lu")
 DECLARE_STREAM_OPERATOR(double       , "%g" )
+DECLARE_STREAM_OPERATOR(void*        , "%p" )
 #undef DECLARE_STREAM_OPERATOR
 
 LogMessage::LogMessage(LogLevel level, const char* filename, int line)
diff --git a/src/google/protobuf/stubs/common.h b/src/google/protobuf/stubs/common.h
index dde48f47..ca7be71f 100644
--- a/src/google/protobuf/stubs/common.h
+++ b/src/google/protobuf/stubs/common.h
@@ -218,6 +218,17 @@ static const uint64 kuint64max = GOOGLE_ULONGLONG(0xFFFFFFFFFFFFFFFF);
 #endif
 #endif
 
+#ifndef GOOGLE_ATTRIBUTE_NOINLINE
+#if defined(__GNUC__) && (__GNUC__ > 3 ||(__GNUC__ == 3 && __GNUC_MINOR__ >= 1))
+// For functions we want to force not inline.
+// Introduced in gcc 3.1.
+#define GOOGLE_ATTRIBUTE_NOINLINE __attribute__ ((noinline))
+#else
+// Other compilers will have to figure it out for themselves.
+#define GOOGLE_ATTRIBUTE_NOINLINE
+#endif
+#endif
+
 #ifndef GOOGLE_ATTRIBUTE_DEPRECATED
 #ifdef __GNUC__
 // If the method/variable/type is used anywhere, produce a warning.
@@ -236,6 +247,15 @@ static const uint64 kuint64max = GOOGLE_ULONGLONG(0xFFFFFFFFFFFFFFFF);
 #endif
 #endif
 
+#ifndef GOOGLE_PREDICT_FALSE
+#ifdef __GNUC__
+// Provided at least since GCC 3.0.
+#define GOOGLE_PREDICT_FALSE(x) (__builtin_expect(!!(x), 1))
+#else
+#define GOOGLE_PREDICT_FALSE
+#endif
+#endif
+
 // Delimits a block of code which may write to memory which is simultaneously
 // written by other threads, but which has been determined to be thread-safe
 // (e.g. because it is an idempotent write).
@@ -246,6 +266,52 @@ static const uint64 kuint64max = GOOGLE_ULONGLONG(0xFFFFFFFFFFFFFFFF);
 #define GOOGLE_SAFE_CONCURRENT_WRITES_END()
 #endif
 
+#define GOOGLE_GUARDED_BY(x)
+
+// x86 and x86-64 can perform unaligned loads/stores directly.
+#if defined(_M_X64) || defined(__x86_64__) || \
+    defined(_M_IX86) || defined(__i386__)
+
+#define GOOGLE_UNALIGNED_LOAD16(_p) (*reinterpret_cast<const uint16 *>(_p))
+#define GOOGLE_UNALIGNED_LOAD32(_p) (*reinterpret_cast<const uint32 *>(_p))
+#define GOOGLE_UNALIGNED_LOAD64(_p) (*reinterpret_cast<const uint64 *>(_p))
+
+#define GOOGLE_UNALIGNED_STORE16(_p, _val) (*reinterpret_cast<uint16 *>(_p) = (_val))
+#define GOOGLE_UNALIGNED_STORE32(_p, _val) (*reinterpret_cast<uint32 *>(_p) = (_val))
+#define GOOGLE_UNALIGNED_STORE64(_p, _val) (*reinterpret_cast<uint64 *>(_p) = (_val))
+
+#else
+inline uint16 GOOGLE_UNALIGNED_LOAD16(const void *p) {
+  uint16 t;
+  memcpy(&t, p, sizeof t);
+  return t;
+}
+
+inline uint32 GOOGLE_UNALIGNED_LOAD32(const void *p) {
+  uint32 t;
+  memcpy(&t, p, sizeof t);
+  return t;
+}
+
+inline uint64 GOOGLE_UNALIGNED_LOAD64(const void *p) {
+  uint64 t;
+  memcpy(&t, p, sizeof t);
+  return t;
+}
+
+inline void GOOGLE_UNALIGNED_STORE16(void *p, uint16 v) {
+  memcpy(p, &v, sizeof v);
+}
+
+inline void GOOGLE_UNALIGNED_STORE32(void *p, uint32 v) {
+  memcpy(p, &v, sizeof v);
+}
+
+inline void GOOGLE_UNALIGNED_STORE64(void *p, uint64 v) {
+  memcpy(p, &v, sizeof v);
+}
+#endif
+
 // ===================================================================
 // from google3/base/basictypes.h
 
@@ -288,71 +354,6 @@ static const uint64 kuint64max = GOOGLE_ULONGLONG(0xFFFFFFFFFFFFFFFF);
   ((sizeof(a) / sizeof(*(a))) / \
    static_cast<size_t>(!(sizeof(a) % sizeof(*(a)))))
 
-namespace internal {
-
-// Use implicit_cast as a safe version of static_cast or const_cast
-// for upcasting in the type hierarchy (i.e. casting a pointer to Foo
-// to a pointer to SuperclassOfFoo or casting a pointer to Foo to
-// a const pointer to Foo).
-// When you use implicit_cast, the compiler checks that the cast is safe.
-// Such explicit implicit_casts are necessary in surprisingly many
-// situations where C++ demands an exact type match instead of an
-// argument type convertable to a target type.
-//
-// The From type can be inferred, so the preferred syntax for using
-// implicit_cast is the same as for static_cast etc.:
-//
-//   implicit_cast<ToType>(expr)
-//
-// implicit_cast would have been part of the C++ standard library,
-// but the proposal was submitted too late.  It will probably make
-// its way into the language in the future.
-template<typename To, typename From>
-inline To implicit_cast(From const &f) {
-  return f;
-}
-
-// When you upcast (that is, cast a pointer from type Foo to type
-// SuperclassOfFoo), it's fine to use implicit_cast<>, since upcasts
-// always succeed.  When you downcast (that is, cast a pointer from
-// type Foo to type SubclassOfFoo), static_cast<> isn't safe, because
-// how do you know the pointer is really of type SubclassOfFoo?  It
-// could be a bare Foo, or of type DifferentSubclassOfFoo.  Thus,
-// when you downcast, you should use this macro.  In debug mode, we
-// use dynamic_cast<> to double-check the downcast is legal (we die
-// if it's not).  In normal mode, we do the efficient static_cast<>
-// instead.  Thus, it's important to test in debug mode to make sure
-// the cast is legal!
-//    This is the only place in the code we should use dynamic_cast<>.
-// In particular, you SHOULDN'T be using dynamic_cast<> in order to
-// do RTTI (eg code like this:
-//    if (dynamic_cast<Subclass1>(foo)) HandleASubclass1Object(foo);
-//    if (dynamic_cast<Subclass2>(foo)) HandleASubclass2Object(foo);
-// You should design the code some other way not to need this.
-
-template<typename To, typename From>     // use like this: down_cast<T*>(foo);
-inline To down_cast(From* f) {                   // so we only accept pointers
-  // Ensures that To is a sub-type of From *.  This test is here only
-  // for compile-time type checking, and has no overhead in an
-  // optimized build at run-time, as it will be optimized away
-  // completely.
-  if (false) {
-    implicit_cast<From*, To>(0);
-  }
-
-#if !defined(NDEBUG) && !defined(GOOGLE_PROTOBUF_NO_RTTI)
-  assert(f == NULL || dynamic_cast<To>(f) != NULL);  // RTTI: debug mode only!
-#endif
-  return static_cast<To>(f);
-}
-
-}  // namespace internal
-
-// We made these internal so that they would show up as such in the docs,
-// but we don't want to stick "internal::" in front of them everywhere.
-using internal::implicit_cast;
-using internal::down_cast;
-
 // The COMPILE_ASSERT macro can be used to verify that a compile time
 // expression is true. For example, you could use it to verify the
 // size of a static array:
@@ -657,6 +658,7 @@ class LIBPROTOBUF_EXPORT LogMessage {
   LogMessage& operator<<(long value);
   LogMessage& operator<<(unsigned long value);
   LogMessage& operator<<(double value);
+  LogMessage& operator<<(void* value);
 
  private:
   friend class LogFinisher;
@@ -731,7 +733,8 @@ T* CheckNotNull(const char* /* file */, int /* line */,
 }
 }  // namespace internal
 #define GOOGLE_CHECK_NOTNULL(A) \
-  internal::CheckNotNull(__FILE__, __LINE__, "'" #A "' must not be NULL", (A))
+  ::google::protobuf::internal::CheckNotNull(\
+      __FILE__, __LINE__, "'" #A "' must not be NULL", (A))
 
 #ifdef NDEBUG
 
diff --git a/src/google/protobuf/stubs/common_unittest.cc b/src/google/protobuf/stubs/common_unittest.cc
index cb892072..7eb4e317 100644
--- a/src/google/protobuf/stubs/common_unittest.cc
+++ b/src/google/protobuf/stubs/common_unittest.cc
@@ -31,6 +31,7 @@
 // Author: kenton@google.com (Kenton Varda)
 
 #include <vector>
+#include <google/protobuf/stubs/casts.h>
 #include <google/protobuf/stubs/common.h>
 #include <google/protobuf/stubs/strutil.h>
 #include <google/protobuf/stubs/substitute.h>
diff --git a/src/google/protobuf/stubs/fastmem.h b/src/google/protobuf/stubs/fastmem.h
new file mode 100644
index 00000000..e553f142
--- /dev/null
+++ b/src/google/protobuf/stubs/fastmem.h
@@ -0,0 +1,153 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2014 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Fast memory copying and comparison routines.
+//   strings::fastmemcmp_inlined() replaces memcmp()
+//   strings::memcpy_inlined() replaces memcpy()
+//   strings::memeq(a, b, n) replaces memcmp(a, b, n) == 0
+//
+// strings::*_inlined() routines are inline versions of the
+// routines exported by this module.  Sometimes using the inlined
+// versions is faster.  Measure before using the inlined versions.
+//
+// Performance measurement:
+//   strings::fastmemcmp_inlined
+//     Analysis: memcmp, fastmemcmp_inlined, fastmemcmp
+//     2012-01-30
+
+#ifndef GOOGLE_PROTOBUF_STUBS_FASTMEM_H_
+#define GOOGLE_PROTOBUF_STUBS_FASTMEM_H_
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <google/protobuf/stubs/common.h>
+
+namespace google {
+namespace protobuf {
+namespace internal {
+
+// Return true if the n bytes at a equal the n bytes at b.
+// The regions are allowed to overlap.
+//
+// The performance is similar to the performance memcmp(), but faster for
+// moderately-sized inputs, or inputs that share a common prefix and differ
+// somewhere in their last 8 bytes. Further optimizations can be added later
+// if it makes sense to do so.:w
+inline bool memeq(const char* a, const char* b, size_t n) {
+  size_t n_rounded_down = n & ~static_cast<size_t>(7);
+  if (GOOGLE_PREDICT_FALSE(n_rounded_down == 0)) {  // n <= 7
+    return memcmp(a, b, n) == 0;
+  }
+  // n >= 8
+  uint64 u = GOOGLE_UNALIGNED_LOAD64(a) ^ GOOGLE_UNALIGNED_LOAD64(b);
+  uint64 v = GOOGLE_UNALIGNED_LOAD64(a + n - 8) ^ GOOGLE_UNALIGNED_LOAD64(b + n - 8);
+  if ((u | v) != 0) {  // The first or last 8 bytes differ.
+    return false;
+  }
+  a += 8;
+  b += 8;
+  n = n_rounded_down - 8;
+  if (n > 128) {
+    // As of 2012, memcmp on x86-64 uses a big unrolled loop with SSE2
+    // instructions, and while we could try to do something faster, it
+    // doesn't seem worth pursuing.
+    return memcmp(a, b, n) == 0;
+  }
+  for (; n >= 16; n -= 16) {
+    uint64 x = GOOGLE_UNALIGNED_LOAD64(a) ^ GOOGLE_UNALIGNED_LOAD64(b);
+    uint64 y = GOOGLE_UNALIGNED_LOAD64(a + 8) ^ GOOGLE_UNALIGNED_LOAD64(b + 8);
+    if ((x | y) != 0) {
+      return false;
+    }
+    a += 16;
+    b += 16;
+  }
+  // n must be 0 or 8 now because it was a multiple of 8 at the top of the loop.
+  return n == 0 || GOOGLE_UNALIGNED_LOAD64(a) == GOOGLE_UNALIGNED_LOAD64(b);
+}
+
+inline int fastmemcmp_inlined(const char *a, const char *b, size_t n) {
+  if (n >= 64) {
+    return memcmp(a, b, n);
+  }
+  const char* a_limit = a + n;
+  while (a + sizeof(uint64) <= a_limit &&
+         GOOGLE_UNALIGNED_LOAD64(a) == GOOGLE_UNALIGNED_LOAD64(b)) {
+    a += sizeof(uint64);
+    b += sizeof(uint64);
+  }
+  if (a + sizeof(uint32) <= a_limit &&
+      GOOGLE_UNALIGNED_LOAD32(a) == GOOGLE_UNALIGNED_LOAD32(b)) {
+    a += sizeof(uint32);
+    b += sizeof(uint32);
+  }
+  while (a < a_limit) {
+    int d = static_cast<uint32>(*a++) - static_cast<uint32>(*b++);
+    if (d) return d;
+  }
+  return 0;
+}
+
+// The standard memcpy operation is slow for variable small sizes.
+// This implementation inlines the optimal realization for sizes 1 to 16.
+// To avoid code bloat don't use it in case of not performance-critical spots,
+// nor when you don't expect very frequent values of size <= 16.
+inline void memcpy_inlined(char *dst, const char *src, size_t size) {
+  // Compiler inlines code with minimal amount of data movement when third
+  // parameter of memcpy is a constant.
+  switch (size) {
+    case  1: memcpy(dst, src, 1); break;
+    case  2: memcpy(dst, src, 2); break;
+    case  3: memcpy(dst, src, 3); break;
+    case  4: memcpy(dst, src, 4); break;
+    case  5: memcpy(dst, src, 5); break;
+    case  6: memcpy(dst, src, 6); break;
+    case  7: memcpy(dst, src, 7); break;
+    case  8: memcpy(dst, src, 8); break;
+    case  9: memcpy(dst, src, 9); break;
+    case 10: memcpy(dst, src, 10); break;
+    case 11: memcpy(dst, src, 11); break;
+    case 12: memcpy(dst, src, 12); break;
+    case 13: memcpy(dst, src, 13); break;
+    case 14: memcpy(dst, src, 14); break;
+    case 15: memcpy(dst, src, 15); break;
+    case 16: memcpy(dst, src, 16); break;
+    default: memcpy(dst, src, size); break;
+  }
+}
+
+}  // namespace internal
+}  // namespace protobuf
+}  // namespace google
+
+#endif  // GOOGLE_PROTOBUF_STUBS_FASTMEM_H_
diff --git a/src/google/protobuf/stubs/singleton.h b/src/google/protobuf/stubs/singleton.h
new file mode 100644
index 00000000..e123e4fe
--- /dev/null
+++ b/src/google/protobuf/stubs/singleton.h
@@ -0,0 +1,64 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2014 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#ifndef GOOGLE_PROTOBUF_STUBS_SINGLETON_H__
+#define GOOGLE_PROTOBUF_STUBS_SINGLETON_H__
+
+#include <google/protobuf/stubs/atomicops.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/once.h>
+
+namespace google {
+namespace protobuf {
+namespace internal {
+template<typename T>
+class Singleton {
+ public:
+  static T* get() {
+    GoogleOnceInit(&once_, &Singleton<T>::Init);
+    return instance_;
+  }
+ private:
+  static void Init() {
+    instance_ = new T();
+  }
+  static ProtobufOnceType once_;
+  static T* instance_;
+};
+
+template<typename T>
+ProtobufOnceType Singleton<T>::once_;
+
+template<typename T>
+T* Singleton<T>::instance_;
+}  // namespace internal
+}  // namespace protobuf
+}  // namespace google
+
+#endif  // GOOGLE_PROTOBUF_STUBS_SINGLETON_H__
diff --git a/src/google/protobuf/stubs/strutil.cc b/src/google/protobuf/stubs/strutil.cc
index a8982593..86d45685 100644
--- a/src/google/protobuf/stubs/strutil.cc
+++ b/src/google/protobuf/stubs/strutil.cc
@@ -94,6 +94,34 @@ void StripString(string* s, const char* remove, char replacewith) {
   }
 }
 
+void StripWhitespace(string* str) {
+  int str_length = str->length();
+
+  // Strip off leading whitespace.
+  int first = 0;
+  while (first < str_length && ascii_isspace(str->at(first))) {
+    ++first;
+  }
+  // If entire string is white space.
+  if (first == str_length) {
+    str->clear();
+    return;
+  }
+  if (first > 0) {
+    str->erase(0, first);
+    str_length -= first;
+  }
+
+  // Strip off trailing whitespace.
+  int last = str_length - 1;
+  while (last >= 0 && ascii_isspace(str->at(last))) {
+    --last;
+  }
+  if (last != (str_length - 1) && last >= 0) {
+    str->erase(last + 1, string::npos);
+  }
+}
+
 // ----------------------------------------------------------------------
 // StringReplace()
 //    Replace the "old" pattern with the "new" pattern in a string,
@@ -1275,5 +1303,33 @@ string ToHex(uint64 num) {
   return string(bufptr, buf + 16 - bufptr);
 }
 
+int GlobalReplaceSubstring(const string& substring,
+                           const string& replacement,
+                           string* s) {
+  GOOGLE_CHECK(s != NULL);
+  if (s->empty() || substring.empty())
+    return 0;
+  string tmp;
+  int num_replacements = 0;
+  int pos = 0;
+  for (int match_pos = s->find(substring.data(), pos, substring.length());
+       match_pos != string::npos;
+       pos = match_pos + substring.length(),
+           match_pos = s->find(substring.data(), pos, substring.length())) {
+    ++num_replacements;
+    // Append the original content before the match.
+    tmp.append(*s, pos, match_pos - pos);
+    // Append the replacement for the match.
+    tmp.append(replacement.begin(), replacement.end());
+  }
+  // Append the content after the last match. If no replacements were made, the
+  // original string is left untouched.
+  if (num_replacements > 0) {
+    tmp.append(*s, pos, s->length() - pos);
+    s->swap(tmp);
+  }
+  return num_replacements;
+}
+
 }  // namespace protobuf
 }  // namespace google
diff --git a/src/google/protobuf/stubs/strutil.h b/src/google/protobuf/stubs/strutil.h
index 4178ac9f..f2e1a944 100644
--- a/src/google/protobuf/stubs/strutil.h
+++ b/src/google/protobuf/stubs/strutil.h
@@ -57,6 +57,8 @@ namespace protobuf {
 //    strings, so locale should not be taken into account.
 // ascii_isdigit()
 //    Like above, but only accepts digits.
+// ascii_isspace()
+//    Check if the character is a space character.
 // ----------------------------------------------------------------------
 
 inline bool ascii_isalnum(char c) {
@@ -69,6 +71,10 @@ inline bool ascii_isdigit(char c) {
   return ('0' <= c && c <= '9');
 }
 
+inline bool ascii_isspace(char c) {
+  return c == ' ';
+}
+
 // ----------------------------------------------------------------------
 // HasPrefixString()
 //    Check if a string begins with a given prefix.
@@ -119,10 +125,15 @@ inline string StripSuffixString(const string& str, const string& suffix) {
 //    in 'remove') with the character 'replacewith'.
 //    Good for keeping html characters or protocol characters (\t) out
 //    of places where they might cause a problem.
+// StripWhitespace
+//    Removes whitespaces from both ends of the given string.
 // ----------------------------------------------------------------------
 LIBPROTOBUF_EXPORT void StripString(string* s, const char* remove,
                                     char replacewith);
 
+LIBPROTOBUF_EXPORT void StripWhitespace(string* s);
+
+
 // ----------------------------------------------------------------------
 // LowerString()
 // UpperString()
@@ -501,6 +512,16 @@ inline string ToString(string a) {
 // StrCat()
 //    These methods join some strings together.
 // ----------------------------------------------------------------------
+template <typename T1, typename T2, typename T3, typename T4, typename T5,
+          typename T6, typename T7>
+string StrCat(
+    const T1& a, const T2& b, const T3& c, const T4& d, const T5& e,
+    const T6& f, const T7& g) {
+  return internal::ToString(a) + internal::ToString(b) +
+      internal::ToString(c) + internal::ToString(d) + internal::ToString(e) +
+      internal::ToString(f) + internal::ToString(g);
+}
+
 template <typename T1, typename T2, typename T3, typename T4, typename T5>
 string StrCat(
     const T1& a, const T2& b, const T3& c, const T4& d, const T5& e) {
@@ -556,6 +577,17 @@ string Join(const Range& components,
 // ----------------------------------------------------------------------
 LIBPROTOBUF_EXPORT string ToHex(uint64 num);
 
+// ----------------------------------------------------------------------
+// GlobalReplaceSubstring()
+//    Replaces all instances of a substring in a string.  Does nothing
+//    if 'substring' is empty.  Returns the number of replacements.
+//
+//    NOTE: The string pieces must not overlap s.
+// ----------------------------------------------------------------------
+LIBPROTOBUF_EXPORT int GlobalReplaceSubstring(const string& substring,
+                                              const string& replacement,
+                                              string* s);
+
 }  // namespace protobuf
 }  // namespace google
 
diff --git a/src/google/protobuf/stubs/type_traits.h b/src/google/protobuf/stubs/type_traits.h
index e41f5e6f..f5365c38 100644
--- a/src/google/protobuf/stubs/type_traits.h
+++ b/src/google/protobuf/stubs/type_traits.h
@@ -35,6 +35,7 @@
 // any changes here, make sure that you're not breaking any platforms.
 //
 // Define a small subset of tr1 type traits. The traits we define are:
+//   enable_if
 //   is_integral
 //   is_floating_point
 //   is_pointer
@@ -60,12 +61,27 @@
 
 #include <utility>                  // For pair
 
+#include <google/protobuf/stubs/common.h>
 #include <google/protobuf/stubs/template_util.h>  // For true_type and false_type
 
 namespace google {
 namespace protobuf {
 namespace internal {
 
+template<typename B, typename D>
+struct is_base_of {
+  typedef char (&yes)[1];
+  typedef char (&no)[2];
+
+  static yes check(const B*);
+  static no check(const void*);
+
+  enum {
+    value = sizeof(check(static_cast<const D*>(NULL))) == sizeof(yes),
+  };
+};
+
+template <bool cond, class T = void> struct enable_if;
 template <class T> struct is_integral;
 template <class T> struct is_floating_point;
 template <class T> struct is_pointer;
@@ -91,6 +107,13 @@ template <class T, class U> struct is_same;
 template <class From, class To> struct is_convertible;
 #endif
 
+// enable_if, equivalent semantics to c++11 std::enable_if, specifically:
+//   "If B is true, the member typedef type shall equal T; otherwise, there
+//    shall be no member typedef type."
+// Specified by 20.9.7.6 [Other transformations]
+
+template<bool cond, class T> struct enable_if { typedef T type; };
+template<class T> struct enable_if<false, T> {};
 // is_integral is false except for the built-in integer types. A
 // cv-qualified type is integral if and only if the underlying type is.
 template <class T> struct is_integral : false_type { };
@@ -144,7 +167,7 @@ template <class T> struct is_pointer<const volatile T> : is_pointer<T> { };
 
 #if !defined(_MSC_VER) && !(defined(__GNUC__) && __GNUC__ <= 3)
 
-namespace internal {
+namespace type_traits_internal {
 
 template <class T> struct is_class_or_union {
   template <class U> static small_ tester(void (U::*)());
@@ -159,7 +182,7 @@ template <bool NotUnum, class T> struct is_enum_impl
 
 template <class T> struct is_enum_impl<true, T> : false_type { };
 
-}  // namespace internal
+}  // namespace type_traits_internal
 
 // Specified by TR1 [4.5.1] primary type categories.
 
@@ -177,12 +200,12 @@ template <class T> struct is_enum_impl<true, T> : false_type { };
 // because it can't be used with some types (e.g. void or classes with
 // inaccessible conversion operators).
 template <class T> struct is_enum
-    : internal::is_enum_impl<
+    : type_traits_internal::is_enum_impl<
           is_same<T, void>::value ||
               is_integral<T>::value ||
               is_floating_point<T>::value ||
               is_reference<T>::value ||
-              internal::is_class_or_union<T>::value,
+              type_traits_internal::is_class_or_union<T>::value,
           T> { };
 
 template <class T> struct is_enum<const T> : is_enum<T> { };
@@ -300,7 +323,7 @@ template<typename T> struct is_same<T, T> : public true_type { };
 
 // Specified by TR1 [4.6] Relationships between types
 #if !defined(_MSC_VER) && !(defined(__GNUC__) && __GNUC__ <= 3)
-namespace internal {
+namespace type_traits_internal {
 
 // This class is an implementation detail for is_convertible, and you
 // don't need to know how it works to use is_convertible. For those
@@ -317,14 +340,14 @@ struct ConvertHelper {
   static big_ Test(...);
   static From Create();
 };
-}  // namespace internal
+}  // namespace type_traits_internal
 
 // Inherits from true_type if From is convertible to To, false_type otherwise.
 template <typename From, typename To>
 struct is_convertible
     : integral_constant<bool,
-                        sizeof(internal::ConvertHelper<From, To>::Test(
-                                  internal::ConvertHelper<From, To>::Create()))
+                        sizeof(type_traits_internal::ConvertHelper<From, To>::Test(
+                                  type_traits_internal::ConvertHelper<From, To>::Create()))
                         == sizeof(small_)> {
 };
 #endif
diff --git a/src/google/protobuf/text_format.cc b/src/google/protobuf/text_format.cc
index 84cdbb57..fd04bef1 100644
--- a/src/google/protobuf/text_format.cc
+++ b/src/google/protobuf/text_format.cc
@@ -50,6 +50,7 @@
 #include <google/protobuf/unknown_field_set.h>
 #include <google/protobuf/descriptor.pb.h>
 #include <google/protobuf/io/tokenizer.h>
+#include <google/protobuf/stubs/stringprintf.h>
 #include <google/protobuf/stubs/strutil.h>
 #include <google/protobuf/stubs/map_util.h>
 #include <google/protobuf/stubs/stl_util.h>
@@ -1583,10 +1584,23 @@ void TextFormat::Printer::PrintFieldValue(
     }
 
     case FieldDescriptor::CPPTYPE_ENUM: {
-      const EnumValueDescriptor *enum_val = field->is_repeated()
-          ? reflection->GetRepeatedEnum(message, field, index)
-          : reflection->GetEnum(message, field);
-      generator.Print(printer->PrintEnum(enum_val->number(), enum_val->name()));
+      int enum_value = field->is_repeated()
+          ? reflection->GetRepeatedEnumValue(message, field, index)
+          : reflection->GetEnumValue(message, field);
+      const EnumValueDescriptor* enum_desc =
+          field->enum_type()->FindValueByNumber(enum_value);
+      if (enum_desc != NULL) {
+        generator.Print(printer->PrintEnum(enum_value, enum_desc->name()));
+      } else {
+        // Ordinarily, enum_desc should not be null, because proto2 has the
+        // invariant that set enum field values must be in-range, but with the
+        // new integer-based API for enums (or the RepeatedField<int> loophole),
+        // it is possible for the user to force an unknown integer value.  So we
+        // simply use the integer value itself as the enum value name in this
+        // case.
+        generator.Print(printer->PrintEnum(enum_value,
+                                           StringPrintf("%d", enum_value)));
+      }
       break;
     }
 
diff --git a/src/google/protobuf/text_format.h b/src/google/protobuf/text_format.h
index 29549410..548962cb 100644
--- a/src/google/protobuf/text_format.h
+++ b/src/google/protobuf/text_format.h
@@ -40,6 +40,9 @@
 
 #include <map>
 #include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
 #include <string>
 #include <vector>
 
diff --git a/src/google/protobuf/unittest.proto b/src/google/protobuf/unittest.proto
index c48cc923..7450fe53 100644
--- a/src/google/protobuf/unittest.proto
+++ b/src/google/protobuf/unittest.proto
@@ -34,6 +34,7 @@
 //
 // A proto file we will use for unit testing.
 
+syntax = "proto2";
 
 // Some generic_services option(s) added automatically.
 // See:  http://go/proto2-generic-services-default
@@ -429,7 +430,7 @@ message TestMutualRecursionB {
 }
 
 // Test that groups have disjoint field numbers from their siblings and
-// parents.  This is NOT possible in proto1; only proto2.  When attempting
+// parents.  This is NOT possible in proto1; only google.protobuf.  When attempting
 // to compile with proto1, this will emit an error; so we only include it
 // in protobuf_unittest_proto.
 message TestDupFieldNumber {                        // NO_PROTO1
@@ -505,6 +506,15 @@ message TestFieldOrderings {
   optional int64 my_int = 1;
   extensions 12 to 100;
   optional float my_float = 101;
+  message NestedMessage {
+    optional int64 oo = 2;
+    // The field name "b" fails to compile in proto1 because it conflicts with
+    // a local variable named "b" in one of the generated methods.  Doh.
+    // This file needs to compile in proto1 to test backwards-compatibility.
+    optional int32 bb = 1;
+  }
+
+  optional NestedMessage optional_nested_message  = 200;
 }
 
 
diff --git a/src/google/protobuf/unittest_arena.proto b/src/google/protobuf/unittest_arena.proto
new file mode 100644
index 00000000..6fdbbe02
--- /dev/null
+++ b/src/google/protobuf/unittest_arena.proto
@@ -0,0 +1,45 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto2";
+
+import "google/protobuf/unittest_no_arena_import.proto";
+
+package proto2_arena_unittest;
+
+
+message NestedMessage {
+  optional int32 d = 1;
+}
+
+message ArenaMessage {
+  repeated NestedMessage  repeated_nested_message = 1;
+  repeated ImportNoArenaNestedMessage  repeated_import_no_arena_message = 2;
+};
diff --git a/src/google/protobuf/unittest_custom_options.proto b/src/google/protobuf/unittest_custom_options.proto
index 0bb12e17..d4d6e869 100644
--- a/src/google/protobuf/unittest_custom_options.proto
+++ b/src/google/protobuf/unittest_custom_options.proto
@@ -32,8 +32,9 @@
 //  Based on original Protocol Buffers design by
 //  Sanjay Ghemawat, Jeff Dean, and others.
 //
-// A proto file used to test the "custom options" feature of proto2.
+// A proto file used to test the "custom options" feature of google.protobuf.
 
+syntax = "proto2";
 
 // Some generic_services option(s) added automatically.
 // See:  http://go/proto2-generic-services-default
diff --git a/src/google/protobuf/unittest_drop_unknown_fields.proto b/src/google/protobuf/unittest_drop_unknown_fields.proto
new file mode 100644
index 00000000..66b31acf
--- /dev/null
+++ b/src/google/protobuf/unittest_drop_unknown_fields.proto
@@ -0,0 +1,55 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package unittest_drop_unknown_fields;
+
+message Foo {
+  enum NestedEnum {
+    FOO = 0;
+    BAR = 1;
+    BAZ = 2;
+  }
+  optional int32 int32_value = 1;
+  optional NestedEnum enum_value = 2;
+}
+
+message FooWithExtraFields {
+  enum NestedEnum {
+    FOO = 0;
+    BAR = 1;
+    BAZ = 2;
+    QUX = 3;
+  }
+  optional int32 int32_value = 1;
+  optional NestedEnum enum_value = 2;
+  optional int32 extra_int32_value = 3;
+}
diff --git a/src/google/protobuf/unittest_embed_optimize_for.proto b/src/google/protobuf/unittest_embed_optimize_for.proto
index ad515131..d8b0f9b9 100644
--- a/src/google/protobuf/unittest_embed_optimize_for.proto
+++ b/src/google/protobuf/unittest_embed_optimize_for.proto
@@ -34,6 +34,7 @@
 //
 // A proto file which imports a proto file that uses optimize_for = CODE_SIZE.
 
+syntax = "proto2";
 import "google/protobuf/unittest_optimize_for.proto";
 
 package protobuf_unittest;
diff --git a/src/google/protobuf/unittest_empty.proto b/src/google/protobuf/unittest_empty.proto
index b7337ef3..36443e7e 100644
--- a/src/google/protobuf/unittest_empty.proto
+++ b/src/google/protobuf/unittest_empty.proto
@@ -35,3 +35,4 @@
 // This file intentionally left blank.  (At one point this wouldn't compile
 // correctly.)
 
+syntax = "proto2";
diff --git a/src/google/protobuf/unittest_enormous_descriptor.proto b/src/google/protobuf/unittest_enormous_descriptor.proto
index 3ba8b419..2250261d 100644
--- a/src/google/protobuf/unittest_enormous_descriptor.proto
+++ b/src/google/protobuf/unittest_enormous_descriptor.proto
@@ -35,6 +35,7 @@
 // A proto file that has an extremely large descriptor.  Used to test that
 // descriptors over 64k don't break the string literal length limit in Java.
 
+syntax = "proto2";
 
 package google.protobuf;
 option java_package = "com.google.protobuf";
diff --git a/src/google/protobuf/unittest_import.proto b/src/google/protobuf/unittest_import.proto
index 38275dc9..c1289e38 100644
--- a/src/google/protobuf/unittest_import.proto
+++ b/src/google/protobuf/unittest_import.proto
@@ -34,6 +34,7 @@
 //
 // A proto file which is imported by unittest.proto to test importing.
 
+syntax = "proto2";
 
 // We don't put this in a package within proto2 because we need to make sure
 // that the generated code doesn't depend on being in the proto2 namespace.
diff --git a/src/google/protobuf/unittest_import_lite.proto b/src/google/protobuf/unittest_import_lite.proto
index 7cee113a..a7afa452 100644
--- a/src/google/protobuf/unittest_import_lite.proto
+++ b/src/google/protobuf/unittest_import_lite.proto
@@ -32,6 +32,7 @@
 //
 // This is like unittest_import.proto but with optimize_for = LITE_RUNTIME.
 
+syntax = "proto2";
 package protobuf_unittest_import;
 
 option optimize_for = LITE_RUNTIME;
diff --git a/src/google/protobuf/unittest_import_public.proto b/src/google/protobuf/unittest_import_public.proto
index e5929cb5..ffaf7736 100644
--- a/src/google/protobuf/unittest_import_public.proto
+++ b/src/google/protobuf/unittest_import_public.proto
@@ -30,6 +30,7 @@
 
 // Author: liujisi@google.com (Pherl Liu)
 
+syntax = "proto2";
 
 package protobuf_unittest_import;
 
diff --git a/src/google/protobuf/unittest_import_public_lite.proto b/src/google/protobuf/unittest_import_public_lite.proto
index e39bdb49..33549c22 100644
--- a/src/google/protobuf/unittest_import_public_lite.proto
+++ b/src/google/protobuf/unittest_import_public_lite.proto
@@ -30,6 +30,7 @@
 
 // Author: liujisi@google.com (Pherl Liu)
 
+syntax = "proto2";
 
 package protobuf_unittest_import;
 
diff --git a/src/google/protobuf/unittest_lite.proto b/src/google/protobuf/unittest_lite.proto
index 30dd67fb..662c0e46 100644
--- a/src/google/protobuf/unittest_lite.proto
+++ b/src/google/protobuf/unittest_lite.proto
@@ -32,6 +32,7 @@
 //
 // This is like unittest.proto but with optimize_for = LITE_RUNTIME.
 
+syntax = "proto2";
 package protobuf_unittest;
 
 import "google/protobuf/unittest_import_lite.proto";
diff --git a/src/google/protobuf/unittest_lite_imports_nonlite.proto b/src/google/protobuf/unittest_lite_imports_nonlite.proto
index 5ef8a06d..132d6a82 100644
--- a/src/google/protobuf/unittest_lite_imports_nonlite.proto
+++ b/src/google/protobuf/unittest_lite_imports_nonlite.proto
@@ -32,6 +32,7 @@
 //
 // Tests that a "lite" message can import a regular message.
 
+syntax = "proto2";
 package protobuf_unittest;
 
 import "google/protobuf/unittest.proto";
diff --git a/src/google/protobuf/unittest_mset.proto b/src/google/protobuf/unittest_mset.proto
index 8fbe7abb..5a07ed12 100644
--- a/src/google/protobuf/unittest_mset.proto
+++ b/src/google/protobuf/unittest_mset.proto
@@ -34,6 +34,7 @@
 //
 // This file contains messages for testing message_set_wire_format.
 
+syntax = "proto2";
 package protobuf_unittest;
 
 option optimize_for = SPEED;
diff --git a/src/google/protobuf/unittest_no_arena.proto b/src/google/protobuf/unittest_no_arena.proto
new file mode 100644
index 00000000..cd7cbbae
--- /dev/null
+++ b/src/google/protobuf/unittest_no_arena.proto
@@ -0,0 +1,199 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: kenton@google.com (Kenton Varda)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// This proto file contains copies of TestAllTypes and friends, but with arena
+// support disabled in code generation. It allows us to test the performance
+// impact against baseline (non-arena) google.protobuf.
+
+syntax = "proto2";
+
+// Some generic_services option(s) added automatically.
+// See:  http://go/proto2-generic-services-default
+option cc_generic_services = true;     // auto-added
+option java_generic_services = true;   // auto-added
+option py_generic_services = true;     // auto-added
+
+import "google/protobuf/unittest_import.proto";
+import "google/protobuf/unittest_arena.proto";
+
+// We don't put this in a package within proto2 because we need to make sure
+// that the generated code doesn't depend on being in the proto2 namespace.
+// In test_util.h we do "using namespace unittest = protobuf_unittest".
+package protobuf_unittest_no_arena;
+
+// Protos optimized for SPEED use a strict superset of the generated code
+// of equivalent ones optimized for CODE_SIZE, so we should optimize all our
+// tests for speed unless explicitly testing code size optimization.
+option optimize_for = SPEED;
+
+option java_outer_classname = "UnittestProto";
+
+// This proto includes every type of field in both singular and repeated
+// forms.
+message TestAllTypes {
+  message NestedMessage {
+    // The field name "b" fails to compile in proto1 because it conflicts with
+    // a local variable named "b" in one of the generated methods.  Doh.
+    // This file needs to compile in proto1 to test backwards-compatibility.
+    optional int32 bb = 1;
+  }
+
+  enum NestedEnum {
+    FOO = 1;
+    BAR = 2;
+    BAZ = 3;
+    NEG = -1;  // Intentionally negative.
+  }
+
+  // Singular
+  optional    int32 optional_int32    =  1;
+  optional    int64 optional_int64    =  2;
+  optional   uint32 optional_uint32   =  3;
+  optional   uint64 optional_uint64   =  4;
+  optional   sint32 optional_sint32   =  5;
+  optional   sint64 optional_sint64   =  6;
+  optional  fixed32 optional_fixed32  =  7;
+  optional  fixed64 optional_fixed64  =  8;
+  optional sfixed32 optional_sfixed32 =  9;
+  optional sfixed64 optional_sfixed64 = 10;
+  optional    float optional_float    = 11;
+  optional   double optional_double   = 12;
+  optional     bool optional_bool     = 13;
+  optional   string optional_string   = 14;
+  optional    bytes optional_bytes    = 15;
+
+  optional group OptionalGroup = 16 {
+    optional int32 a = 17;
+  }
+
+  optional NestedMessage                        optional_nested_message  = 18;
+  optional ForeignMessage                       optional_foreign_message = 19;
+  optional protobuf_unittest_import.ImportMessage optional_import_message  = 20;
+
+  optional NestedEnum                           optional_nested_enum     = 21;
+  optional ForeignEnum                          optional_foreign_enum    = 22;
+  optional protobuf_unittest_import.ImportEnum    optional_import_enum     = 23;
+
+  optional string optional_string_piece = 24 [ctype=STRING_PIECE];
+  optional string optional_cord = 25 [ctype=CORD];
+
+  // Defined in unittest_import_public.proto
+  optional protobuf_unittest_import.PublicImportMessage
+      optional_public_import_message = 26;
+
+  optional NestedMessage optional_lazy_message = 27 [lazy=true];
+
+  // Repeated
+  repeated    int32 repeated_int32    = 31;
+  repeated    int64 repeated_int64    = 32;
+  repeated   uint32 repeated_uint32   = 33;
+  repeated   uint64 repeated_uint64   = 34;
+  repeated   sint32 repeated_sint32   = 35;
+  repeated   sint64 repeated_sint64   = 36;
+  repeated  fixed32 repeated_fixed32  = 37;
+  repeated  fixed64 repeated_fixed64  = 38;
+  repeated sfixed32 repeated_sfixed32 = 39;
+  repeated sfixed64 repeated_sfixed64 = 40;
+  repeated    float repeated_float    = 41;
+  repeated   double repeated_double   = 42;
+  repeated     bool repeated_bool     = 43;
+  repeated   string repeated_string   = 44;
+  repeated    bytes repeated_bytes    = 45;
+
+  repeated group RepeatedGroup = 46 {
+    optional int32 a = 47;
+  }
+
+  repeated NestedMessage                        repeated_nested_message  = 48;
+  repeated ForeignMessage                       repeated_foreign_message = 49;
+  repeated protobuf_unittest_import.ImportMessage repeated_import_message  = 50;
+
+  repeated NestedEnum                           repeated_nested_enum     = 51;
+  repeated ForeignEnum                          repeated_foreign_enum    = 52;
+  repeated protobuf_unittest_import.ImportEnum    repeated_import_enum     = 53;
+
+  repeated string repeated_string_piece = 54 [ctype=STRING_PIECE];
+  repeated string repeated_cord = 55 [ctype=CORD];
+
+  repeated NestedMessage repeated_lazy_message = 57 [lazy=true];
+
+  // Singular with defaults
+  optional    int32 default_int32    = 61 [default =  41    ];
+  optional    int64 default_int64    = 62 [default =  42    ];
+  optional   uint32 default_uint32   = 63 [default =  43    ];
+  optional   uint64 default_uint64   = 64 [default =  44    ];
+  optional   sint32 default_sint32   = 65 [default = -45    ];
+  optional   sint64 default_sint64   = 66 [default =  46    ];
+  optional  fixed32 default_fixed32  = 67 [default =  47    ];
+  optional  fixed64 default_fixed64  = 68 [default =  48    ];
+  optional sfixed32 default_sfixed32 = 69 [default =  49    ];
+  optional sfixed64 default_sfixed64 = 70 [default = -50    ];
+  optional    float default_float    = 71 [default =  51.5  ];
+  optional   double default_double   = 72 [default =  52e3  ];
+  optional     bool default_bool     = 73 [default = true   ];
+  optional   string default_string   = 74 [default = "hello"];
+  optional    bytes default_bytes    = 75 [default = "world"];
+
+  optional NestedEnum  default_nested_enum  = 81 [default = BAR        ];
+  optional ForeignEnum default_foreign_enum = 82 [default = FOREIGN_BAR];
+  optional protobuf_unittest_import.ImportEnum
+      default_import_enum = 83 [default = IMPORT_BAR];
+
+  optional string default_string_piece = 84 [ctype=STRING_PIECE,default="abc"];
+  optional string default_cord = 85 [ctype=CORD,default="123"];
+
+  // For oneof test
+  oneof oneof_field {
+    uint32 oneof_uint32 = 111;
+    NestedMessage oneof_nested_message = 112;
+    string oneof_string = 113;
+    bytes oneof_bytes = 114;
+  }
+}
+
+// Define these after TestAllTypes to make sure the compiler can handle
+// that.
+message ForeignMessage {
+  optional int32 c = 1;
+}
+
+enum ForeignEnum {
+  FOREIGN_FOO = 4;
+  FOREIGN_BAR = 5;
+  FOREIGN_BAZ = 6;
+}
+
+message TestNoArenaMessage {
+  optional proto2_arena_unittest.ArenaMessage arena_message = 1;
+};
diff --git a/src/google/protobuf/unittest_no_arena_import.proto b/src/google/protobuf/unittest_no_arena_import.proto
new file mode 100644
index 00000000..072af49e
--- /dev/null
+++ b/src/google/protobuf/unittest_no_arena_import.proto
@@ -0,0 +1,37 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto2";
+
+package proto2_arena_unittest;
+
+message ImportNoArenaNestedMessage {
+  optional int32 d = 1;
+};
diff --git a/src/google/protobuf/unittest_no_field_presence.proto b/src/google/protobuf/unittest_no_field_presence.proto
new file mode 100644
index 00000000..e04da0ac
--- /dev/null
+++ b/src/google/protobuf/unittest_no_field_presence.proto
@@ -0,0 +1,138 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// A proto file used to test a message type with no explicit field presence.
+
+syntax = "proto3";
+
+// We want to test embedded proto2 messages, so include some proto2 types.
+import "google/protobuf/unittest.proto";
+
+package proto2_nofieldpresence_unittest;
+
+// This proto includes every type of field in both singular and repeated
+// forms.
+message TestAllTypes {
+  message NestedMessage {
+    optional int32 bb = 1;
+  }
+
+  enum NestedEnum {
+    FOO = 0;
+    BAR = 1;
+    BAZ = 2;
+  }
+
+  // Singular
+  // TODO: remove 'optional' labels as soon as CL 69188077 is LGTM'd to make
+  // 'optional' optional.
+  optional    int32 optional_int32    =  1;
+  optional    int64 optional_int64    =  2;
+  optional   uint32 optional_uint32   =  3;
+  optional   uint64 optional_uint64   =  4;
+  optional   sint32 optional_sint32   =  5;
+  optional   sint64 optional_sint64   =  6;
+  optional  fixed32 optional_fixed32  =  7;
+  optional  fixed64 optional_fixed64  =  8;
+  optional sfixed32 optional_sfixed32 =  9;
+  optional sfixed64 optional_sfixed64 = 10;
+  optional    float optional_float    = 11;
+  optional   double optional_double   = 12;
+  optional     bool optional_bool     = 13;
+  optional   string optional_string   = 14;
+  optional    bytes optional_bytes    = 15;
+
+  optional NestedMessage                        optional_nested_message  = 18;
+  optional ForeignMessage                       optional_foreign_message = 19;
+  optional protobuf_unittest.TestAllTypes         optional_proto2_message = 20;
+
+  optional NestedEnum                           optional_nested_enum     = 21;
+  optional ForeignEnum                          optional_foreign_enum    = 22;
+  // N.B.: proto2-enum-type fields not allowed, because their default values
+  // might not be zero.
+  //optional protobuf_unittest.ForeignEnum          optional_proto2_enum     = 23;
+
+  optional string optional_string_piece = 24 [ctype=STRING_PIECE];
+  optional string optional_cord = 25 [ctype=CORD];
+
+  optional NestedMessage optional_lazy_message = 30 [lazy=true];
+
+  // Repeated
+  repeated    int32 repeated_int32    = 31;
+  repeated    int64 repeated_int64    = 32;
+  repeated   uint32 repeated_uint32   = 33;
+  repeated   uint64 repeated_uint64   = 34;
+  repeated   sint32 repeated_sint32   = 35;
+  repeated   sint64 repeated_sint64   = 36;
+  repeated  fixed32 repeated_fixed32  = 37;
+  repeated  fixed64 repeated_fixed64  = 38;
+  repeated sfixed32 repeated_sfixed32 = 39;
+  repeated sfixed64 repeated_sfixed64 = 40;
+  repeated    float repeated_float    = 41;
+  repeated   double repeated_double   = 42;
+  repeated     bool repeated_bool     = 43;
+  repeated   string repeated_string   = 44;
+  repeated    bytes repeated_bytes    = 45;
+
+  repeated NestedMessage                        repeated_nested_message  = 48;
+  repeated ForeignMessage                       repeated_foreign_message = 49;
+  repeated protobuf_unittest.TestAllTypes         repeated_proto2_message  = 50;
+
+  repeated NestedEnum                           repeated_nested_enum     = 51;
+  repeated ForeignEnum                          repeated_foreign_enum    = 52;
+
+  repeated string repeated_string_piece = 54 [ctype=STRING_PIECE];
+  repeated string repeated_cord = 55 [ctype=CORD];
+
+  repeated NestedMessage repeated_lazy_message = 57 [lazy=true];
+
+  oneof oneof_field {
+    uint32 oneof_uint32 = 111;
+    NestedMessage oneof_nested_message = 112;
+    string oneof_string = 113;
+    NestedEnum oneof_enum = 114;
+  }
+}
+
+message TestProto2Required {
+  optional protobuf_unittest.TestRequired proto2 = 1;
+}
+
+// Define these after TestAllTypes to make sure the compiler can handle
+// that.
+message ForeignMessage {
+  optional int32 c = 1;
+}
+
+enum ForeignEnum {
+  FOREIGN_FOO = 0;
+  FOREIGN_BAR = 1;
+  FOREIGN_BAZ = 2;
+}
diff --git a/src/google/protobuf/unittest_no_generic_services.proto b/src/google/protobuf/unittest_no_generic_services.proto
index cf6d16c2..8fc7713c 100644
--- a/src/google/protobuf/unittest_no_generic_services.proto
+++ b/src/google/protobuf/unittest_no_generic_services.proto
@@ -30,6 +30,7 @@
 
 // Author: kenton@google.com (Kenton Varda)
 
+syntax = "proto2";
 package google.protobuf.no_generic_services_test;
 
 
diff --git a/src/google/protobuf/unittest_optimize_for.proto b/src/google/protobuf/unittest_optimize_for.proto
index 9f7b4eea..ee9cc7bd 100644
--- a/src/google/protobuf/unittest_optimize_for.proto
+++ b/src/google/protobuf/unittest_optimize_for.proto
@@ -34,6 +34,7 @@
 //
 // A proto file which uses optimize_for = CODE_SIZE.
 
+syntax = "proto2";
 import "google/protobuf/unittest.proto";
 
 package protobuf_unittest;
diff --git a/src/google/protobuf/unittest_preserve_unknown_enum.proto b/src/google/protobuf/unittest_preserve_unknown_enum.proto
new file mode 100644
index 00000000..ba050d70
--- /dev/null
+++ b/src/google/protobuf/unittest_preserve_unknown_enum.proto
@@ -0,0 +1,66 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package proto2_preserve_unknown_enum_unittest;
+
+enum MyEnum {
+  FOO = 0;
+  BAR = 1;
+  BAZ = 2;
+}
+
+enum MyEnumPlusExtra {
+  E_FOO = 0;
+  E_BAR = 1;
+  E_BAZ = 2;
+  E_EXTRA = 3;
+}
+
+message MyMessage {
+  optional MyEnum e = 1;
+  repeated MyEnum repeated_e = 2;
+  repeated MyEnum repeated_packed_e = 3 [packed=true];
+  oneof o {
+    MyEnum oneof_e_1 = 4;
+    MyEnum oneof_e_2 = 5;
+  }
+}
+
+message MyMessagePlusExtra {
+  optional MyEnumPlusExtra e = 1;
+  repeated MyEnumPlusExtra repeated_e = 2;
+  repeated MyEnumPlusExtra repeated_packed_e = 3 [packed=true];
+  oneof o {
+    MyEnumPlusExtra oneof_e_1 = 4;
+    MyEnumPlusExtra oneof_e_2 = 5;
+  }
+}
diff --git a/src/google/protobuf/unittest_proto3_arena.proto b/src/google/protobuf/unittest_proto3_arena.proto
new file mode 100644
index 00000000..84ec7960
--- /dev/null
+++ b/src/google/protobuf/unittest_proto3_arena.proto
@@ -0,0 +1,143 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+
+import "google/protobuf/unittest_import.proto";
+
+package proto3_arena_unittest;
+
+// This proto includes every type of field in both singular and repeated
+// forms.
+message TestAllTypes {
+  message NestedMessage {
+    // The field name "b" fails to compile in proto1 because it conflicts with
+    // a local variable named "b" in one of the generated methods.  Doh.
+    // This file needs to compile in proto1 to test backwards-compatibility.
+    optional int32 bb = 1;
+  }
+
+  enum NestedEnum {
+    FOO = 0;
+    BAR = 1;
+    BAZ = 2;
+    NEG = -1;  // Intentionally negative.
+  }
+
+  // Singular
+  optional    int32 optional_int32    =  1;
+  optional    int64 optional_int64    =  2;
+  optional   uint32 optional_uint32   =  3;
+  optional   uint64 optional_uint64   =  4;
+  optional   sint32 optional_sint32   =  5;
+  optional   sint64 optional_sint64   =  6;
+  optional  fixed32 optional_fixed32  =  7;
+  optional  fixed64 optional_fixed64  =  8;
+  optional sfixed32 optional_sfixed32 =  9;
+  optional sfixed64 optional_sfixed64 = 10;
+  optional    float optional_float    = 11;
+  optional   double optional_double   = 12;
+  optional     bool optional_bool     = 13;
+  optional   string optional_string   = 14;
+  optional    bytes optional_bytes    = 15;
+
+  optional group OptionalGroup = 16 {
+    optional int32 a = 17;
+  }
+
+  optional NestedMessage                        optional_nested_message  = 18;
+  optional ForeignMessage                       optional_foreign_message = 19;
+  optional protobuf_unittest_import.ImportMessage optional_import_message  = 20;
+
+  optional NestedEnum                           optional_nested_enum     = 21;
+  optional ForeignEnum                          optional_foreign_enum    = 22;
+
+  optional string optional_string_piece = 24 [ctype=STRING_PIECE];
+  optional string optional_cord = 25 [ctype=CORD];
+
+  // Defined in unittest_import_public.proto
+  optional protobuf_unittest_import.PublicImportMessage
+      optional_public_import_message = 26;
+
+  optional NestedMessage optional_lazy_message = 27 [lazy=true];
+
+  // Repeated
+  repeated    int32 repeated_int32    = 31;
+  repeated    int64 repeated_int64    = 32;
+  repeated   uint32 repeated_uint32   = 33;
+  repeated   uint64 repeated_uint64   = 34;
+  repeated   sint32 repeated_sint32   = 35;
+  repeated   sint64 repeated_sint64   = 36;
+  repeated  fixed32 repeated_fixed32  = 37;
+  repeated  fixed64 repeated_fixed64  = 38;
+  repeated sfixed32 repeated_sfixed32 = 39;
+  repeated sfixed64 repeated_sfixed64 = 40;
+  repeated    float repeated_float    = 41;
+  repeated   double repeated_double   = 42;
+  repeated     bool repeated_bool     = 43;
+  repeated   string repeated_string   = 44;
+  repeated    bytes repeated_bytes    = 45;
+
+  repeated group RepeatedGroup = 46 {
+    optional int32 a = 47;
+  }
+
+  repeated NestedMessage                        repeated_nested_message  = 48;
+  repeated ForeignMessage                       repeated_foreign_message = 49;
+  repeated protobuf_unittest_import.ImportMessage repeated_import_message  = 50;
+
+  repeated NestedEnum                           repeated_nested_enum     = 51;
+  repeated ForeignEnum                          repeated_foreign_enum    = 52;
+
+  repeated string repeated_string_piece = 54 [ctype=STRING_PIECE];
+  repeated string repeated_cord = 55 [ctype=CORD];
+
+  repeated NestedMessage repeated_lazy_message = 57 [lazy=true];
+
+  oneof oneof_field {
+    uint32 oneof_uint32 = 111;
+    NestedMessage oneof_nested_message = 112;
+    string oneof_string = 113;
+    bytes oneof_bytes = 114;
+  }
+}
+
+// Define these after TestAllTypes to make sure the compiler can handle
+// that.
+message ForeignMessage {
+  optional int32 c = 1;
+}
+
+enum ForeignEnum {
+  FOREIGN_FOO = 0;
+  FOREIGN_BAR = 1;
+  FOREIGN_BAZ = 2;
+}
diff --git a/src/google/protobuf/unknown_enum_impl.h b/src/google/protobuf/unknown_enum_impl.h
new file mode 100644
index 00000000..fb5380aa
--- /dev/null
+++ b/src/google/protobuf/unknown_enum_impl.h
@@ -0,0 +1,132 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_UNKNOWN_ENUM_IMPL_H__
+#define GOOGLE_PROTOBUF_UTIL_UNKNOWN_ENUM_IMPL_H__
+
+#include <stdlib.h>
+
+#include <google/protobuf/stubs/common.h>
+#include "net/proto/tagmapper.h"
+#include <google/protobuf/bridge/compatibility_mode_support.h>
+
+namespace google {
+namespace protobuf {
+
+// google/protobuf/message.h
+class Message;
+
+namespace util {
+
+// NOTE: You should not call these functions directly.  Instead use either
+// HAS_UNKNOWN_ENUM() or GET_UNKNOWN_ENUM(), defined in the public header.
+// The macro-versions operate in a type-safe manner and behave appropriately
+// for the proto version of the message, whereas these versions assume a
+// specific proto version and allow the caller to pass in any arbitrary integer
+// value as a field number.
+//
+// Returns whether the message has unrecognized the enum value for a given
+// field. It also stores the value into the unknown_value parameter if the
+// function returns true and the pointer is not NULL.
+//
+// In proto2, invalid enum values will be treated as unknown fields. This
+// function checks that case.
+bool HasUnknownEnum(const Message& message, int32 field_number,
+                    int32* unknown_value = nullptr);
+// Same as above, but returns all unknown enums.
+bool GetRepeatedEnumUnknowns(const Message& message, int32 field_number,
+                             vector<int32>* unknown_values = nullptr);
+// In proto1, invalue enum values are stored in the same way as valid enum
+// values.
+// TODO(karner): Delete this once the migration to proto2 is complete.
+bool HasUnknownEnumProto1(const Message& message, int32 field_number,
+                          int32* unknown_value);
+// Same as above, but returns all unknown enums.
+bool GetRepeatedEnumUnknownsProto1(const Message& message, int32 field_number,
+                                   vector<int32>* unknown_values);
+// Invokes the appropriate version based on whether the message is proto1
+// or proto2.
+template <typename T>
+bool HasUnknownEnum_Template(const T& message, int32 field_number,
+                             int32* unknown_value = nullptr) {
+  if (internal::is_base_of<bridge::internal::Proto1CompatibleMessage, T>::value ||
+      !internal::is_base_of<ProtocolMessage, T>::value) {
+    return HasUnknownEnum(message, field_number, unknown_value);
+  } else {
+    return HasUnknownEnumProto1(message, field_number, unknown_value);
+  }
+}
+// Invokes the appropriate version based on whether the message is proto1
+// or proto2.
+template <typename T>
+bool GetRepeatedEnumUnknowns_Template(
+    const T& message, int32 field_number,
+    vector<int32>* unknown_values = nullptr) {
+  if (internal::is_base_of<bridge::internal::Proto1CompatibleMessage, T>::value ||
+      !internal::is_base_of<ProtocolMessage, T>::value) {
+    return GetRepeatedEnumUnknowns(message, field_number, unknown_values);
+  } else {
+    return GetRepeatedEnumUnknownsProto1(message, field_number,
+                                         unknown_values);
+  }
+}
+
+// NOTE: You should not call these functions directly.  Instead use
+// SET_UNKNOWN_ENUM(), defined in the public header.  The macro-versions
+// operate in a type-safe manner and behave appropriately for the proto
+// version of the message, whereas these versions assume a specific proto
+// version and allow the caller to pass in any arbitrary integer value as a
+// field number.
+//
+// Sets the given value in the unknown fields of the message.
+void SetUnknownEnum(Message* message, int32 field_number, int32 unknown_value);
+// In proto1, invalue enum values are stored in the same way as valid enum
+// values.
+// TODO(karner): Delete this once the migration to proto2 is complete.
+void SetUnknownEnumProto1(Message* message, int32 field_number,
+                          int32 unknown_value);
+// Invokes the appropriate version based on whether the message is proto1
+// or proto2.
+template <typename T>
+void SetUnknownEnum_Template(T* message, int32 field_number,
+                             int32 unknown_value) {
+  if (internal::is_base_of<bridge::internal::Proto1CompatibleMessage, T>::value ||
+      !internal::is_base_of<ProtocolMessage, T>::value) {
+    SetUnknownEnum(message, field_number, unknown_value);
+  } else {
+    SetUnknownEnumProto1(message, field_number, unknown_value);
+  }
+}
+
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_UNKNOWN_ENUM_IMPL_H__
diff --git a/src/google/protobuf/unknown_enum_test.proto b/src/google/protobuf/unknown_enum_test.proto
new file mode 100644
index 00000000..caafadcd
--- /dev/null
+++ b/src/google/protobuf/unknown_enum_test.proto
@@ -0,0 +1,61 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Definitions of protos for testing cross-version compatibility.  The
+// UpRevision message acts as if it were a newer version of the DownRevision
+// message.  That is, UpRevision shares all the same fields as DownRevision,
+// but UpRevision can add fields and add enum values.
+syntax = "proto2";
+
+package google.protobuf.util;
+
+
+message DownRevision {
+  enum Enum {
+    DEFAULT_VALUE = 2;
+    NONDEFAULT_VALUE = 3;
+  }
+
+  optional Enum value = 1 [default = DEFAULT_VALUE];
+  repeated Enum values = 2;
+}
+
+message UpRevision {
+  enum Enum {
+    DEFAULT_VALUE = 2;
+    NONDEFAULT_VALUE = 3;
+    NEW_VALUE = 4;
+    NEW_VALUE_2 = 5;
+    NEW_VALUE_3 = 6;
+  }
+
+  optional Enum value = 1 [default = DEFAULT_VALUE];
+  repeated Enum values = 2;
+}
diff --git a/src/google/protobuf/unknown_field_set.cc b/src/google/protobuf/unknown_field_set.cc
index 020a323b..e15280c8 100644
--- a/src/google/protobuf/unknown_field_set.cc
+++ b/src/google/protobuf/unknown_field_set.cc
@@ -44,6 +44,25 @@
 namespace google {
 namespace protobuf {
 
+namespace {
+// This global instance is returned by unknown_fields() on any message class
+// when the object has no unknown fields. This is necessary because we now
+// instantiate the UnknownFieldSet dynamically only when required.
+UnknownFieldSet* default_unknown_field_set_instance_ = NULL;
+
+void InitDefaultUnknownFieldSet() {
+  default_unknown_field_set_instance_ = new UnknownFieldSet();
+}
+
+GOOGLE_PROTOBUF_DECLARE_ONCE(default_unknown_field_set_once_init_);
+}
+
+const UnknownFieldSet* UnknownFieldSet::default_instance() {
+  ::google::protobuf::GoogleOnceInit(&default_unknown_field_set_once_init_,
+                 &InitDefaultUnknownFieldSet);
+  return default_unknown_field_set_instance_;
+}
+
 UnknownFieldSet::UnknownFieldSet()
     : fields_(NULL) {}
 
@@ -53,31 +72,63 @@ UnknownFieldSet::~UnknownFieldSet() {
 }
 
 void UnknownFieldSet::ClearFallback() {
-  GOOGLE_DCHECK(fields_ != NULL);
-  for (int i = 0; i < fields_->size(); i++) {
-    (*fields_)[i].Delete();
+  if (fields_ != NULL) {
+    for (int i = 0; i < fields_->size(); i++) {
+      (*fields_)[i].Delete();
+    }
+    delete fields_;
+    fields_ = NULL;
   }
-  fields_->clear();
 }
 
 void UnknownFieldSet::ClearAndFreeMemory() {
   if (fields_ != NULL) {
     Clear();
-    delete fields_;
-    fields_ = NULL;
+  }
+}
+
+void UnknownFieldSet::InternalMergeFrom(const UnknownFieldSet& other) {
+  int other_field_count = other.field_count();
+  if (other_field_count > 0) {
+    fields_ = new vector<UnknownField>();
+    for (int i = 0; i < other_field_count; i++) {
+      fields_->push_back((*other.fields_)[i]);
+      fields_->back().DeepCopy();
+    }
   }
 }
 
 void UnknownFieldSet::MergeFrom(const UnknownFieldSet& other) {
-  for (int i = 0; i < other.field_count(); i++) {
-    AddField(other.field(i));
+  int other_field_count = other.field_count();
+  if (other_field_count > 0) {
+    if (fields_ == NULL) fields_ = new vector<UnknownField>();
+    for (int i = 0; i < other_field_count; i++) {
+      fields_->push_back((*other.fields_)[i]);
+      fields_->back().DeepCopy();
+    }
   }
 }
 
+// A specialized MergeFrom for performance when we are merging from an UFS that
+// is temporary and can be destroyed in the process.
+void UnknownFieldSet::MergeFromAndDestroy(UnknownFieldSet* other) {
+  int other_field_count = other->field_count();
+  if (other_field_count > 0) {
+    if (fields_ == NULL) fields_ = new vector<UnknownField>();
+    for (int i = 0; i < other_field_count; i++) {
+      fields_->push_back((*other->fields_)[i]);
+      (*other->fields_)[i].Reset();
+    }
+  }
+  delete other->fields_;
+  other->fields_ = NULL;
+}
+
 int UnknownFieldSet::SpaceUsedExcludingSelf() const {
   if (fields_ == NULL) return 0;
 
   int total_size = sizeof(*fields_) + sizeof(UnknownField) * fields_->size();
+
   for (int i = 0; i < fields_->size(); i++) {
     const UnknownField& field = (*fields_)[i];
     switch (field.type()) {
@@ -101,61 +152,60 @@ int UnknownFieldSet::SpaceUsed() const {
 }
 
 void UnknownFieldSet::AddVarint(int number, uint64 value) {
-  if (fields_ == NULL) fields_ = new vector<UnknownField>;
   UnknownField field;
   field.number_ = number;
   field.SetType(UnknownField::TYPE_VARINT);
   field.varint_ = value;
+  if (fields_ == NULL) fields_ = new vector<UnknownField>();
   fields_->push_back(field);
 }
 
 void UnknownFieldSet::AddFixed32(int number, uint32 value) {
-  if (fields_ == NULL) fields_ = new vector<UnknownField>;
   UnknownField field;
   field.number_ = number;
   field.SetType(UnknownField::TYPE_FIXED32);
   field.fixed32_ = value;
+  if (fields_ == NULL) fields_ = new vector<UnknownField>();
   fields_->push_back(field);
 }
 
 void UnknownFieldSet::AddFixed64(int number, uint64 value) {
-  if (fields_ == NULL) fields_ = new vector<UnknownField>;
   UnknownField field;
   field.number_ = number;
   field.SetType(UnknownField::TYPE_FIXED64);
   field.fixed64_ = value;
+  if (fields_ == NULL) fields_ = new vector<UnknownField>();
   fields_->push_back(field);
 }
 
 string* UnknownFieldSet::AddLengthDelimited(int number) {
-  if (fields_ == NULL) fields_ = new vector<UnknownField>;
   UnknownField field;
   field.number_ = number;
   field.SetType(UnknownField::TYPE_LENGTH_DELIMITED);
   field.length_delimited_.string_value_ = new string;
+  if (fields_ == NULL) fields_ = new vector<UnknownField>();
   fields_->push_back(field);
   return field.length_delimited_.string_value_;
 }
 
 
 UnknownFieldSet* UnknownFieldSet::AddGroup(int number) {
-  if (fields_ == NULL) fields_ = new vector<UnknownField>;
   UnknownField field;
   field.number_ = number;
   field.SetType(UnknownField::TYPE_GROUP);
   field.group_ = new UnknownFieldSet;
+  if (fields_ == NULL) fields_ = new vector<UnknownField>();
   fields_->push_back(field);
   return field.group_;
 }
 
 void UnknownFieldSet::AddField(const UnknownField& field) {
-  if (fields_ == NULL) fields_ = new vector<UnknownField>;
+  if (fields_ == NULL) fields_ = new vector<UnknownField>();
   fields_->push_back(field);
   fields_->back().DeepCopy();
 }
 
 void UnknownFieldSet::DeleteSubrange(int start, int num) {
-  GOOGLE_DCHECK(fields_ != NULL);
   // Delete the specified fields.
   for (int i = 0; i < num; ++i) {
     (*fields_)[i + start].Delete();
@@ -168,6 +218,11 @@ void UnknownFieldSet::DeleteSubrange(int start, int num) {
   for (int i = 0; i < num; ++i) {
     fields_->pop_back();
   }
+  if (fields_ && fields_->size() == 0) {
+    // maintain invariant: never hold fields_ if empty.
+    delete fields_;
+    fields_ = NULL;
+  }
 }
 
 void UnknownFieldSet::DeleteByNumber(int number) {
@@ -185,13 +240,18 @@ void UnknownFieldSet::DeleteByNumber(int number) {
     }
   }
   fields_->resize(left);
+  if (left == 0) {
+    // maintain invariant: never hold fields_ if empty.
+    delete fields_;
+    fields_ = NULL;
+  }
 }
 
 bool UnknownFieldSet::MergeFromCodedStream(io::CodedInputStream* input) {
   UnknownFieldSet other;
   if (internal::WireFormat::SkipMessage(input, &other) &&
       input->ConsumedEntireMessage()) {
-    MergeFrom(other);
+    MergeFromAndDestroy(&other);
     return true;
   } else {
     return false;
@@ -227,6 +287,22 @@ void UnknownField::Delete() {
   }
 }
 
+// Reset all owned ptrs, a special function for performance, to avoid double
+// owning the ptrs, when we merge from a temporary UnknownFieldSet objects.
+void UnknownField::Reset() {
+  switch (type()) {
+    case UnknownField::TYPE_LENGTH_DELIMITED:
+      length_delimited_.string_value_ = NULL;
+      break;
+    case UnknownField::TYPE_GROUP: {
+      group_ = NULL;
+      break;
+    }
+    default:
+      break;
+  }
+}
+
 void UnknownField::DeepCopy() {
   switch (type()) {
     case UnknownField::TYPE_LENGTH_DELIMITED:
@@ -234,8 +310,8 @@ void UnknownField::DeepCopy() {
           *length_delimited_.string_value_);
       break;
     case UnknownField::TYPE_GROUP: {
-      UnknownFieldSet* group = new UnknownFieldSet;
-      group->MergeFrom(*group_);
+      UnknownFieldSet* group = new UnknownFieldSet();
+      group->InternalMergeFrom(*group_);
       group_ = group;
       break;
     }
diff --git a/src/google/protobuf/unknown_field_set.h b/src/google/protobuf/unknown_field_set.h
index 31f17e2a..6f7a9fdb 100644
--- a/src/google/protobuf/unknown_field_set.h
+++ b/src/google/protobuf/unknown_field_set.h
@@ -88,6 +88,9 @@ class LIBPROTOBUF_EXPORT UnknownFieldSet {
   // Merge the contents of some other UnknownFieldSet with this one.
   void MergeFrom(const UnknownFieldSet& other);
 
+  // Similar to above, but this function will destroy the contents of other.
+  void MergeFromAndDestroy(UnknownFieldSet* other);
+
   // Swaps the contents of some other UnknownFieldSet with this one.
   inline void Swap(UnknownFieldSet* x);
 
@@ -141,12 +144,22 @@ class LIBPROTOBUF_EXPORT UnknownFieldSet {
     return ParseFromArray(data.data(), static_cast<int>(data.size()));
   }
 
+  static const UnknownFieldSet* default_instance();
  private:
-
+  // For InternalMergeFrom
+  friend class UnknownField;
+  // Merges from other UnknownFieldSet. This method assumes, that this object
+  // is newly created and has fields_ == NULL;
+  void InternalMergeFrom(const UnknownFieldSet& other);
   void ClearFallback();
 
+  // fields_ is either NULL, or a pointer to a vector that is *non-empty*. We
+  // never hold the empty vector because we want the 'do we have any unknown
+  // fields' check to be fast, and avoid a cache miss: the UFS instance gets
+  // embedded in the message object, so 'fields_ != NULL' tests a member
+  // variable hot in the cache, without the need to go touch a vector somewhere
+  // else in memory.
   std::vector<UnknownField>* fields_;
-
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(UnknownFieldSet);
 };
 
@@ -198,6 +211,10 @@ class LIBPROTOBUF_EXPORT UnknownField {
   // If this UnknownField contains a pointer, delete it.
   void Delete();
 
+  // Reset all the underlying pointers to NULL. A special function to be only
+  // used while merging from a temporary UFS.
+  void Reset();
+
   // Make a deep copy of any pointers in this UnknownField.
   void DeepCopy();
 
@@ -222,13 +239,14 @@ class LIBPROTOBUF_EXPORT UnknownField {
 // inline implementations
 
 inline void UnknownFieldSet::Clear() {
-  if (fields_ != NULL) {
+  if (fields_) {
     ClearFallback();
   }
 }
 
 inline bool UnknownFieldSet::empty() const {
-  return fields_ == NULL || fields_->empty();
+  // Invariant: fields_ is never empty if present.
+  return !fields_;
 }
 
 inline void UnknownFieldSet::Swap(UnknownFieldSet* x) {
@@ -236,9 +254,10 @@ inline void UnknownFieldSet::Swap(UnknownFieldSet* x) {
 }
 
 inline int UnknownFieldSet::field_count() const {
-  return (fields_ == NULL) ? 0 : static_cast<int>(fields_->size());
+  return fields_ ? static_cast<int>(fields_->size()) : 0;
 }
 inline const UnknownField& UnknownFieldSet::field(int index) const {
+  GOOGLE_DCHECK(fields_ != NULL);
   return (*fields_)[index];
 }
 inline UnknownField* UnknownFieldSet::mutable_field(int index) {
diff --git a/src/google/protobuf/unknown_field_set_unittest.cc b/src/google/protobuf/unknown_field_set_unittest.cc
index aaaa2e89..6bba8fc7 100644
--- a/src/google/protobuf/unknown_field_set_unittest.cc
+++ b/src/google/protobuf/unknown_field_set_unittest.cc
@@ -482,6 +482,13 @@ TEST_F(UnknownFieldSetTest, UnknownEnumValue) {
   }
 }
 
+TEST_F(UnknownFieldSetTest, SpaceUsedExcludingSelf) {
+  UnknownFieldSet empty;
+  empty.AddVarint(1, 0);
+  EXPECT_EQ(/* vector<UnknownField> */ 24 + /* sizeof(UnknownField) */ 16,
+            empty.SpaceUsedExcludingSelf());
+}
+
 TEST_F(UnknownFieldSetTest, SpaceUsed) {
   unittest::TestEmptyMessage empty_message;
 
diff --git a/src/google/protobuf/wire_format.cc b/src/google/protobuf/wire_format.cc
index 6bdfcd62..f4f02157 100644
--- a/src/google/protobuf/wire_format.cc
+++ b/src/google/protobuf/wire_format.cc
@@ -512,10 +512,15 @@ bool WireFormat::ParseAndMergeField(
           int value;
           if (!WireFormatLite::ReadPrimitive<int, WireFormatLite::TYPE_ENUM>(
                   input, &value)) return false;
-          const EnumValueDescriptor* enum_value =
-              field->enum_type()->FindValueByNumber(value);
-          if (enum_value != NULL) {
-            message_reflection->AddEnum(message, field, enum_value);
+          if (message->GetDescriptor()->file()->syntax() ==
+              FileDescriptor::SYNTAX_PROTO3) {
+            message_reflection->AddEnumValue(message, field, value);
+          } else {
+            const EnumValueDescriptor* enum_value =
+                field->enum_type()->FindValueByNumber(value);
+            if (enum_value != NULL) {
+              message_reflection->AddEnum(message, field, enum_value);
+            }
           }
         }
 
@@ -572,21 +577,31 @@ bool WireFormat::ParseAndMergeField(
         int value;
         if (!WireFormatLite::ReadPrimitive<int, WireFormatLite::TYPE_ENUM>(
                 input, &value)) return false;
-        const EnumValueDescriptor* enum_value =
-          field->enum_type()->FindValueByNumber(value);
-        if (enum_value != NULL) {
+        if (message->GetDescriptor()->file()->syntax() ==
+            FileDescriptor::SYNTAX_PROTO3) {
           if (field->is_repeated()) {
-            message_reflection->AddEnum(message, field, enum_value);
+            message_reflection->AddEnumValue(message, field, value);
           } else {
-            message_reflection->SetEnum(message, field, enum_value);
+            message_reflection->SetEnumValue(message, field, value);
           }
         } else {
-          // The enum value is not one of the known values.  Add it to the
-          // UnknownFieldSet.
-          int64 sign_extended_value = static_cast<int64>(value);
-          message_reflection->MutableUnknownFields(message)
-                            ->AddVarint(WireFormatLite::GetTagFieldNumber(tag),
-                                        sign_extended_value);
+          const EnumValueDescriptor* enum_value =
+              field->enum_type()->FindValueByNumber(value);
+          if (enum_value != NULL) {
+            if (field->is_repeated()) {
+              message_reflection->AddEnum(message, field, enum_value);
+            } else {
+              message_reflection->SetEnum(message, field, enum_value);
+            }
+          } else {
+            // The enum value is not one of the known values.  Add it to the
+            // UnknownFieldSet.
+            int64 sign_extended_value = static_cast<int64>(value);
+            message_reflection->MutableUnknownFields(message)
+                              ->AddVarint(
+                                  WireFormatLite::GetTagFieldNumber(tag),
+                                  sign_extended_value);
+          }
         }
         break;
       }
diff --git a/src/google/protobuf/wire_format_lite.cc b/src/google/protobuf/wire_format_lite.cc
index 8de82784..c80a7050 100644
--- a/src/google/protobuf/wire_format_lite.cc
+++ b/src/google/protobuf/wire_format_lite.cc
@@ -291,7 +291,7 @@ bool WireFormatLite::ReadPackedEnumNoInline(io::CodedInputStream* input,
         int, WireFormatLite::TYPE_ENUM>(input, &value)) {
       return false;
     }
-    if (is_valid(value)) {
+    if (is_valid == NULL || is_valid(value)) {
       values->Add(value);
     }
   }
@@ -451,19 +451,24 @@ void WireFormatLite::WriteMessageMaybeToArray(int field_number,
   }
 }
 
-bool WireFormatLite::ReadString(io::CodedInputStream* input,
-                                string* value) {
-  // String is for UTF-8 text only
+static inline bool ReadBytesToString(io::CodedInputStream* input,
+                                     string* value) GOOGLE_ATTRIBUTE_ALWAYS_INLINE;
+static inline bool ReadBytesToString(io::CodedInputStream* input,
+                                     string* value) {
   uint32 length;
-  if (!input->ReadVarint32(&length)) return false;
-  if (!input->InternalReadStringInline(value, length)) return false;
-  return true;
+  return input->ReadVarint32(&length) &&
+      input->InternalReadStringInline(value, length);
 }
-bool WireFormatLite::ReadBytes(io::CodedInputStream* input,
-                               string* value) {
-  uint32 length;
-  if (!input->ReadVarint32(&length)) return false;
-  return input->InternalReadStringInline(value, length);
+
+bool WireFormatLite::ReadBytes(io::CodedInputStream* input, string* value) {
+  return ReadBytesToString(input, value);
+}
+
+bool WireFormatLite::ReadBytes(io::CodedInputStream* input, string** p) {
+  if (*p == &::google::protobuf::internal::GetEmptyStringAlreadyInited()) {
+    *p = new ::std::string();
+  }
+  return ReadBytesToString(input, *p);
 }
 
 }  // namespace internal
diff --git a/src/google/protobuf/wire_format_lite.h b/src/google/protobuf/wire_format_lite.h
index 21aa4889..acf88ead 100644
--- a/src/google/protobuf/wire_format_lite.h
+++ b/src/google/protobuf/wire_format_lite.h
@@ -292,13 +292,22 @@ class LIBPROTOBUF_EXPORT WireFormatLite {
   static bool ReadPackedPrimitiveNoInline(input, RepeatedField<CType>* value);
 
   // Read a packed enum field. Values for which is_valid() returns false are
-  // dropped.
+  // dropped. If is_valid == NULL, no values are dropped.
   static bool ReadPackedEnumNoInline(input,
                                      bool (*is_valid)(int),
                                      RepeatedField<int>* value);
 
-  static bool ReadString(input, string* value);
-  static bool ReadBytes (input, string* value);
+  // Read a string.  ReadString(..., string* value) requires an existing string.
+  static inline bool ReadString(input, string* value);
+  // ReadString(..., string** p) is internal-only, and should only be called
+  // from generated code. It starts by setting *p to "new string"
+  // if *p == &GetEmptyStringAlreadyInited().  It then invokes
+  // ReadString(input, *p).  This is useful for reducing code size.
+  static inline bool ReadString(input, string** p);
+  // Analogous to ReadString().
+  static bool ReadBytes(input, string* value);
+  static bool ReadBytes(input, string** p);
+
 
   static inline bool ReadGroup  (field_number, input, MessageLite* value);
   static inline bool ReadMessage(input, MessageLite* value);
@@ -654,6 +663,19 @@ inline int64 WireFormatLite::ZigZagDecode64(uint64 n) {
   return (n >> 1) ^ -static_cast<int64>(n & 1);
 }
 
+// String is for UTF-8 text only, but, even so, ReadString() can simply
+// call ReadBytes().
+
+inline bool WireFormatLite::ReadString(io::CodedInputStream* input,
+                                       string* value) {
+  return ReadBytes(input, value);
+}
+
+inline bool WireFormatLite::ReadString(io::CodedInputStream* input,
+                                       string** p) {
+  return ReadBytes(input, p);
+}
+
 }  // namespace internal
 }  // namespace protobuf
 
diff --git a/src/google/protobuf/wire_format_lite_inl.h b/src/google/protobuf/wire_format_lite_inl.h
index feb22540..129fc63f 100644
--- a/src/google/protobuf/wire_format_lite_inl.h
+++ b/src/google/protobuf/wire_format_lite_inl.h
@@ -47,6 +47,7 @@
 #include <google/protobuf/repeated_field.h>
 #include <google/protobuf/wire_format_lite.h>
 #include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/arenastring.h>
 
 
 namespace google {
@@ -426,6 +427,7 @@ bool WireFormatLite::ReadPackedPrimitiveNoInline(io::CodedInputStream* input,
 }
 
 
+
 inline bool WireFormatLite::ReadGroup(int field_number,
                                       io::CodedInputStream* input,
                                       MessageLite* value) {
@@ -442,15 +444,12 @@ inline bool WireFormatLite::ReadMessage(io::CodedInputStream* input,
                                         MessageLite* value) {
   uint32 length;
   if (!input->ReadVarint32(&length)) return false;
-  if (!input->IncrementRecursionDepth()) return false;
-  io::CodedInputStream::Limit limit = input->PushLimit(length);
-  if (!value->MergePartialFromCodedStream(input)) return false;
+  std::pair<io::CodedInputStream::Limit, int> p =
+      input->IncrementRecursionDepthAndPushLimit(length);
+  if (p.second < 0 || !value->MergePartialFromCodedStream(input)) return false;
   // Make sure that parsing stopped when the limit was hit, not at an endgroup
   // tag.
-  if (!input->ConsumedEntireMessage()) return false;
-  input->PopLimit(limit);
-  input->DecrementRecursionDepth();
-  return true;
+  return input->DecrementRecursionDepthAndPopLimit(p.first);
 }
 
 // We name the template parameter something long and extremely unlikely to occur
@@ -483,17 +482,14 @@ inline bool WireFormatLite::ReadMessageNoVirtual(
     io::CodedInputStream* input, MessageType_WorkAroundCppLookupDefect* value) {
   uint32 length;
   if (!input->ReadVarint32(&length)) return false;
-  if (!input->IncrementRecursionDepth()) return false;
-  io::CodedInputStream::Limit limit = input->PushLimit(length);
-  if (!value->
+  std::pair<io::CodedInputStream::Limit, int> p =
+      input->IncrementRecursionDepthAndPushLimit(length);
+  if (p.second < 0 || !value->
       MessageType_WorkAroundCppLookupDefect::MergePartialFromCodedStream(input))
     return false;
   // Make sure that parsing stopped when the limit was hit, not at an endgroup
   // tag.
-  if (!input->ConsumedEntireMessage()) return false;
-  input->PopLimit(limit);
-  input->DecrementRecursionDepth();
-  return true;
+  return input->DecrementRecursionDepthAndPopLimit(p.first);
 }
 
 // ===================================================================
diff --git a/src/google/protobuf/wire_format_unittest.cc b/src/google/protobuf/wire_format_unittest.cc
index 81a024b3..a3062a6a 100644
--- a/src/google/protobuf/wire_format_unittest.cc
+++ b/src/google/protobuf/wire_format_unittest.cc
@@ -980,7 +980,8 @@ TEST_F(Utf8ValidationTest, WriteInvalidUTF8String) {
 #ifdef GOOGLE_PROTOBUF_UTF8_VALIDATION_ENABLED
   ASSERT_EQ(1, errors.size());
   EXPECT_TRUE(StartsWith(errors[0],
-                         "String field 'data' contains invalid UTF-8 data when "
+                         "String field 'protobuf_unittest.OneString.data' "
+                         "contains invalid UTF-8 data when "
                          "serializing a protocol buffer. Use the "
                          "'bytes' type if you intend to send raw bytes."));
 #else
@@ -1003,7 +1004,8 @@ TEST_F(Utf8ValidationTest, ReadInvalidUTF8String) {
 #ifdef GOOGLE_PROTOBUF_UTF8_VALIDATION_ENABLED
   ASSERT_EQ(1, errors.size());
   EXPECT_TRUE(StartsWith(errors[0],
-                         "String field 'data' contains invalid UTF-8 data when "
+                         "String field 'protobuf_unittest.OneString.data' "
+                         "contains invalid UTF-8 data when "
                          "parsing a protocol buffer. Use the "
                          "'bytes' type if you intend to send raw bytes."));