Merge master branch.

85 files changed, 525 insertions, 379 deletions

diff --git a/.gitignore b/.gitignore
index db8a893a..a8de0e54 100644
--- a/.gitignore
+++ b/.gitignore
@@ -53,7 +53,7 @@ src/google/protobuf/util/**/*.pb.h
 *.pyc
 *.egg-info
 *_pb2.py
-python/*.egg
+python/**/*.egg
 python/.eggs/
 python/.tox
 python/build/
@@ -186,3 +186,6 @@ cmake/cmake-build-debug/
 # Common build subdirectories.
 ./.build/
 ./_build/
+
+# Visual Studio 2017
+.vs
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 74d4ea7b..00000000
--- a/.travis.yml
+++ /dev/null
@@ -1,90 +0,0 @@
-# Everything is driven by the test.sh, so the language doesn't really
-# matter, it just controls the default install/script/etc. steps on
-# travis.
-language: cpp
-script: ./tests.sh $CONFIG
-
-# The test matrix is manually built to cover a mix of linux and macOS
-# hosted setups; this lets some extra settings be done specific to each
-# host/language instead of forcing common values on all the tests.
-matrix:
-  include:
-    # -----------------------------------------------------------------
-    # macOS hosted tests for Objective-C
-
-    - os: osx
-      env: CONFIG=objectivec_osx
-      osx_image: xcode9.3
-      language: objective-c
-    # iOS build log was starting to choke travis UI, so split to cover the
-    # Xcode Debug and Release Configurations independently.
-    - os: osx
-      env: CONFIG=objectivec_ios_debug
-      osx_image: xcode9.3
-      language: objective-c
-    - os: osx
-      env: CONFIG=objectivec_ios_release
-      osx_image: xcode9.3
-      language: objective-c
-    - os: osx
-      env: CONFIG=objectivec_cocoapods_integration
-      osx_image: xcode9.3
-      language: objective-c
-
-    # -----------------------------------------------------------------
-    # macOS hosted tests for other languages.
-
-    - os: osx
-      env: CONFIG=cpp
-    - os: osx
-      env: CONFIG=cpp_distcheck
-    - os: osx
-      env: CONFIG=javascript
-    - os: osx
-      env: CONFIG=python
-    - os: osx
-      env: CONFIG=python_cpp
-    - os: osx
-      env: CONFIG=php5.6_mac
-    - os: osx
-      env: CONFIG=php7.0_mac
-
-    # -----------------------------------------------------------------
-    # Linux hosted tests
-
-    # The dotnet environment requires Ubuntu 14.04 or 16.04. This
-    # configuration is effectively an "extra" one, outside the
-    # autogenerated matrix.
-    - os: linux
-      env: CONFIG=csharp
-      language: csharp
-      dist: trusty
-      dotnet: 2.0.3
-      mono: none
-      # Install the .NET Core 1.0 runtime as that's what we test against
-      addons:
-        apt:
-          sources:
-          - sourceline: 'deb [arch=amd64] https://packages.microsoft.com/repos/microsoft-ubuntu-trusty-prod trusty main'
-            key_url: 'https://packages.microsoft.com/keys/microsoft.asc'
-          packages:
-          - dotnet-sharedframework-microsoft.netcore.app-1.0.5
-    # This test is kept on travis because it doesn't play nicely with other
-    # tests on jenkins running in parallel.
-    - os: linux
-      env: CONFIG=cpp_distcheck
-    # The Java compatibility test currently only runs on Linux because it will
-    # fetch pre-built Linux protoc binaries in the test.
-    - os: linux
-      env: CONFIG=java_compatibility
-      sudo: required
-      dist: trusty
-    # The Python compatibility test currently only runs on Linux because it will
-    # fetch pre-built Linux protoc binaries in the test.
-    - os: linux
-      env: CONFIG=python_compatibility
-      sudo: required
-      dist: trusty
-
-notifications:
-  email: false
diff --git a/CHANGES.txt b/CHANGES.txt
index c18c6377..a381084a 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,3 +1,15 @@
+2018-07-27 version 3.6.1 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
+
+  C++
+  * Introduced workaround for Windows issue with std::atomic and std::once_flag
+    initialization (#4777, #4773).
+
+  PHP
+  * Added compatibility with PHP 7.3 (#4898).
+
+  Ruby
+  * Fixed Ruby crash involving Any encoding (#4718).
+
 2018-06-01 version 3.6.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
 
   C++
diff --git a/Protobuf.podspec b/Protobuf.podspec
index b5bb673e..f282f540 100644
--- a/Protobuf.podspec
+++ b/Protobuf.podspec
@@ -5,7 +5,7 @@
 # dependent projects use the :git notation to refer to the library.
 Pod::Spec.new do |s|
   s.name     = 'Protobuf'
-  s.version  = '3.6.0'
+  s.version  = '3.6.1'
   s.summary  = 'Protocol Buffers v.3 runtime library for Objective-C.'
   s.homepage = 'https://github.com/google/protobuf'
   s.license  = '3-Clause BSD License'
diff --git a/benchmarks/Makefile.am b/benchmarks/Makefile.am
index 4bf57026..4f7df646 100644
--- a/benchmarks/Makefile.am
+++ b/benchmarks/Makefile.am
@@ -90,8 +90,7 @@ $(benchmarks_protoc_outputs_proto2_header): protoc_middleman2
 
 initialize_submodule:
 	oldpwd=`pwd`
-	cd $(top_srcdir)/third_party
-	git submodule update --init -r
+	cd $(top_srcdir) && git submodule update --init -r third_party/benchmark
 	cd $(top_srcdir)/third_party/benchmark && cmake -DCMAKE_BUILD_TYPE=Release && make
 	cd $$oldpwd
 	touch initialize_submodule
diff --git a/cmake/tests.cmake b/cmake/tests.cmake
index b77a5ebe..001b4200 100644
--- a/cmake/tests.cmake
+++ b/cmake/tests.cmake
@@ -208,6 +208,13 @@ endif()
 
 if(MINGW)
   set_source_files_properties(${tests_files} PROPERTIES COMPILE_FLAGS "-Wno-narrowing")
+
+  # required for tests on MinGW Win64
+  if (CMAKE_SIZEOF_VOID_P EQUAL 8)
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,--stack,16777216")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wa,-mbig-obj")
+  endif()
+
 endif()
 
 add_executable(tests ${tests_files} ${common_test_files} ${tests_proto_files} ${lite_test_proto_files})
diff --git a/configure.ac b/configure.ac
index 69b3fe30..8e1c308c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -17,7 +17,7 @@ AC_PREREQ(2.59)
 # In the SVN trunk, the version should always be the next anticipated release
 # version with the "-pre" suffix.  (We used to use "-SNAPSHOT" but this pushed
 # the size of one file name in the dist tarfile over the 99-char limit.)
-AC_INIT([Protocol Buffers],[3.6.0],[protobuf@googlegroups.com],[protobuf])
+AC_INIT([Protocol Buffers],[3.6.1],[protobuf@googlegroups.com],[protobuf])
 
 AM_MAINTAINER_MODE([enable])
 
diff --git a/conformance/README.md b/conformance/README.md
index 971fe8f6..a5419bf0 100644
--- a/conformance/README.md
+++ b/conformance/README.md
@@ -1,8 +1,6 @@
 Protocol Buffers - Google's data interchange format
 ===================================================
 
-[![Build Status](https://travis-ci.org/google/protobuf.svg?branch=master)](https://travis-ci.org/google/protobuf)
-
 Copyright 2008 Google Inc.
 
 This directory contains conformance tests for testing completeness and
diff --git a/csharp/Google.Protobuf.Tools.nuspec b/csharp/Google.Protobuf.Tools.nuspec
index 0ba7cc9f..901d5ce9 100644
--- a/csharp/Google.Protobuf.Tools.nuspec
+++ b/csharp/Google.Protobuf.Tools.nuspec
@@ -5,7 +5,7 @@
     <title>Google Protocol Buffers tools</title>
     <summary>Tools for Protocol Buffers - Google's data interchange format.</summary>
     <description>See project site for more info.</description>
-    <version>3.6.0</version>
+    <version>3.6.1</version>
     <authors>Google Inc.</authors>
     <owners>protobuf-packages</owners>
     <licenseUrl>https://github.com/google/protobuf/blob/master/LICENSE</licenseUrl>
diff --git a/csharp/src/Google.Protobuf.Conformance/Conformance.cs b/csharp/src/Google.Protobuf.Conformance/Conformance.cs
index 77284824..6ca52c32 100644
--- a/csharp/src/Google.Protobuf.Conformance/Conformance.cs
+++ b/csharp/src/Google.Protobuf.Conformance/Conformance.cs
@@ -24,22 +24,24 @@ namespace Conformance {
     static ConformanceReflection() {
       byte[] descriptorData = global::System.Convert.FromBase64String(
           string.Concat(
-            "ChFjb25mb3JtYW5jZS5wcm90bxILY29uZm9ybWFuY2UiwAEKEkNvbmZvcm1h",
+            "ChFjb25mb3JtYW5jZS5wcm90bxILY29uZm9ybWFuY2Ui1QEKEkNvbmZvcm1h",
             "bmNlUmVxdWVzdBIaChBwcm90b2J1Zl9wYXlsb2FkGAEgASgMSAASFgoManNv",
             "bl9wYXlsb2FkGAIgASgJSAASOAoXcmVxdWVzdGVkX291dHB1dF9mb3JtYXQY",
             "AyABKA4yFy5jb25mb3JtYW5jZS5XaXJlRm9ybWF0EhQKDG1lc3NhZ2VfdHlw",
-            "ZRgEIAEoCRIbChNpZ25vcmVfdW5rbm93bl9qc29uGAUgASgIQgkKB3BheWxv",
-            "YWQisQEKE0NvbmZvcm1hbmNlUmVzcG9uc2USFQoLcGFyc2VfZXJyb3IYASAB",
-            "KAlIABIZCg9zZXJpYWxpemVfZXJyb3IYBiABKAlIABIXCg1ydW50aW1lX2Vy",
-            "cm9yGAIgASgJSAASGgoQcHJvdG9idWZfcGF5bG9hZBgDIAEoDEgAEhYKDGpz",
-            "b25fcGF5bG9hZBgEIAEoCUgAEhEKB3NraXBwZWQYBSABKAlIAEIICgZyZXN1",
-            "bHQqNQoKV2lyZUZvcm1hdBIPCgtVTlNQRUNJRklFRBAAEgwKCFBST1RPQlVG",
-            "EAESCAoESlNPThACQiEKH2NvbS5nb29nbGUucHJvdG9idWYuY29uZm9ybWFu",
-            "Y2ViBnByb3RvMw=="));
+            "ZRgEIAEoCRIwCg10ZXN0X2NhdGVnb3J5GAUgASgOMhkuY29uZm9ybWFuY2Uu",
+            "VGVzdENhdGVnb3J5QgkKB3BheWxvYWQisQEKE0NvbmZvcm1hbmNlUmVzcG9u",
+            "c2USFQoLcGFyc2VfZXJyb3IYASABKAlIABIZCg9zZXJpYWxpemVfZXJyb3IY",
+            "BiABKAlIABIXCg1ydW50aW1lX2Vycm9yGAIgASgJSAASGgoQcHJvdG9idWZf",
+            "cGF5bG9hZBgDIAEoDEgAEhYKDGpzb25fcGF5bG9hZBgEIAEoCUgAEhEKB3Nr",
+            "aXBwZWQYBSABKAlIAEIICgZyZXN1bHQqNQoKV2lyZUZvcm1hdBIPCgtVTlNQ",
+            "RUNJRklFRBAAEgwKCFBST1RPQlVGEAESCAoESlNPThACKlQKDFRlc3RDYXRl",
+            "Z29yeRIPCgtCSU5BUllfVEVTVBAAEg0KCUpTT05fVEVTVBABEiQKIEpTT05f",
+            "SUdOT1JFX1VOS05PV05fUEFSU0lOR19URVNUEAJCIQofY29tLmdvb2dsZS5w",
+            "cm90b2J1Zi5jb25mb3JtYW5jZWIGcHJvdG8z"));
       descriptor = pbr::FileDescriptor.FromGeneratedCode(descriptorData,
           new pbr::FileDescriptor[] { },
-          new pbr::GeneratedClrTypeInfo(new[] {typeof(global::Conformance.WireFormat), }, new pbr::GeneratedClrTypeInfo[] {
-            new pbr::GeneratedClrTypeInfo(typeof(global::Conformance.ConformanceRequest), global::Conformance.ConformanceRequest.Parser, new[]{ "ProtobufPayload", "JsonPayload", "RequestedOutputFormat", "MessageType", "IgnoreUnknownJson" }, new[]{ "Payload" }, null, null),
+          new pbr::GeneratedClrTypeInfo(new[] {typeof(global::Conformance.WireFormat), typeof(global::Conformance.TestCategory), }, new pbr::GeneratedClrTypeInfo[] {
+            new pbr::GeneratedClrTypeInfo(typeof(global::Conformance.ConformanceRequest), global::Conformance.ConformanceRequest.Parser, new[]{ "ProtobufPayload", "JsonPayload", "RequestedOutputFormat", "MessageType", "TestCategory" }, new[]{ "Payload" }, null, null),
             new pbr::GeneratedClrTypeInfo(typeof(global::Conformance.ConformanceResponse), global::Conformance.ConformanceResponse.Parser, new[]{ "ParseError", "SerializeError", "RuntimeError", "ProtobufPayload", "JsonPayload", "Skipped" }, new[]{ "Result" }, null, null)
           }));
     }
@@ -53,6 +55,25 @@ namespace Conformance {
     [pbr::OriginalName("JSON")] Json = 2,
   }
 
+  public enum TestCategory {
+    /// <summary>
+    /// Test binary wire format.
+    /// </summary>
+    [pbr::OriginalName("BINARY_TEST")] BinaryTest = 0,
+    /// <summary>
+    /// Test json wire format.
+    /// </summary>
+    [pbr::OriginalName("JSON_TEST")] JsonTest = 1,
+    /// <summary>
+    /// Similar to JSON_TEST. However, during parsing json, testee should ignore
+    /// unknown fields. This feature is optional. Each implementation can descide
+    /// whether to support it.  See
+    /// https://developers.google.com/protocol-buffers/docs/proto3#json_options
+    /// for more detail.
+    /// </summary>
+    [pbr::OriginalName("JSON_IGNORE_UNKNOWN_PARSING_TEST")] JsonIgnoreUnknownParsingTest = 2,
+  }
+
   #endregion
 
   #region Messages
@@ -90,7 +111,7 @@ namespace Conformance {
     public ConformanceRequest(ConformanceRequest other) : this() {
       requestedOutputFormat_ = other.requestedOutputFormat_;
       messageType_ = other.messageType_;
-      ignoreUnknownJson_ = other.ignoreUnknownJson_;
+      testCategory_ = other.testCategory_;
       switch (other.PayloadCase) {
         case PayloadOneofCase.ProtobufPayload:
           ProtobufPayload = other.ProtobufPayload;
@@ -160,14 +181,19 @@ namespace Conformance {
       }
     }
 
-    /// <summary>Field number for the "ignore_unknown_json" field.</summary>
-    public const int IgnoreUnknownJsonFieldNumber = 5;
-    private bool ignoreUnknownJson_;
+    /// <summary>Field number for the "test_category" field.</summary>
+    public const int TestCategoryFieldNumber = 5;
+    private global::Conformance.TestCategory testCategory_ = 0;
+    /// <summary>
+    /// Each test is given a specific test category. Some category may need spedific
+    /// support in testee programs. Refer to the defintion of TestCategory for
+    /// more information.
+    /// </summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IgnoreUnknownJson {
-      get { return ignoreUnknownJson_; }
+    public global::Conformance.TestCategory TestCategory {
+      get { return testCategory_; }
       set {
-        ignoreUnknownJson_ = value;
+        testCategory_ = value;
       }
     }
 
@@ -207,7 +233,7 @@ namespace Conformance {
       if (JsonPayload != other.JsonPayload) return false;
       if (RequestedOutputFormat != other.RequestedOutputFormat) return false;
       if (MessageType != other.MessageType) return false;
-      if (IgnoreUnknownJson != other.IgnoreUnknownJson) return false;
+      if (TestCategory != other.TestCategory) return false;
       if (PayloadCase != other.PayloadCase) return false;
       return Equals(_unknownFields, other._unknownFields);
     }
@@ -219,7 +245,7 @@ namespace Conformance {
       if (payloadCase_ == PayloadOneofCase.JsonPayload) hash ^= JsonPayload.GetHashCode();
       if (RequestedOutputFormat != 0) hash ^= RequestedOutputFormat.GetHashCode();
       if (MessageType.Length != 0) hash ^= MessageType.GetHashCode();
-      if (IgnoreUnknownJson != false) hash ^= IgnoreUnknownJson.GetHashCode();
+      if (TestCategory != 0) hash ^= TestCategory.GetHashCode();
       hash ^= (int) payloadCase_;
       if (_unknownFields != null) {
         hash ^= _unknownFields.GetHashCode();
@@ -250,9 +276,9 @@ namespace Conformance {
         output.WriteRawTag(34);
         output.WriteString(MessageType);
       }
-      if (IgnoreUnknownJson != false) {
+      if (TestCategory != 0) {
         output.WriteRawTag(40);
-        output.WriteBool(IgnoreUnknownJson);
+        output.WriteEnum((int) TestCategory);
       }
       if (_unknownFields != null) {
         _unknownFields.WriteTo(output);
@@ -274,8 +300,8 @@ namespace Conformance {
       if (MessageType.Length != 0) {
         size += 1 + pb::CodedOutputStream.ComputeStringSize(MessageType);
       }
-      if (IgnoreUnknownJson != false) {
-        size += 1 + 1;
+      if (TestCategory != 0) {
+        size += 1 + pb::CodedOutputStream.ComputeEnumSize((int) TestCategory);
       }
       if (_unknownFields != null) {
         size += _unknownFields.CalculateSize();
@@ -294,8 +320,8 @@ namespace Conformance {
       if (other.MessageType.Length != 0) {
         MessageType = other.MessageType;
       }
-      if (other.IgnoreUnknownJson != false) {
-        IgnoreUnknownJson = other.IgnoreUnknownJson;
+      if (other.TestCategory != 0) {
+        TestCategory = other.TestCategory;
       }
       switch (other.PayloadCase) {
         case PayloadOneofCase.ProtobufPayload:
@@ -334,7 +360,7 @@ namespace Conformance {
             break;
           }
           case 40: {
-            IgnoreUnknownJson = input.ReadBool();
+            testCategory_ = (global::Conformance.TestCategory) input.ReadEnum();
             break;
           }
         }
diff --git a/csharp/src/Google.Protobuf.Conformance/Program.cs b/csharp/src/Google.Protobuf.Conformance/Program.cs
index 96dc354e..1eac00be 100644
--- a/csharp/src/Google.Protobuf.Conformance/Program.cs
+++ b/csharp/src/Google.Protobuf.Conformance/Program.cs
@@ -87,6 +87,9 @@ namespace Google.Protobuf.Conformance
                 switch (request.PayloadCase)
                 {
                     case ConformanceRequest.PayloadOneofCase.JsonPayload:
+                        if (request.TestCategory == global::Conformance.TestCategory.JsonIgnoreUnknownParsingTest) {
+                            return new ConformanceResponse { Skipped = "CSharp doesn't support skipping unknown fields in json parsing." };
+                        }
                         var parser = new JsonParser(new JsonParser.Settings(20, typeRegistry));
                         message = parser.Parse<ProtobufTestMessages.Proto3.TestAllTypesProto3>(request.JsonPayload);
                         break;
diff --git a/csharp/src/Google.Protobuf/Google.Protobuf.csproj b/csharp/src/Google.Protobuf/Google.Protobuf.csproj
index 46728b72..a056b435 100644
--- a/csharp/src/Google.Protobuf/Google.Protobuf.csproj
+++ b/csharp/src/Google.Protobuf/Google.Protobuf.csproj
@@ -4,7 +4,7 @@
     <Description>C# runtime library for Protocol Buffers - Google's data interchange format.</Description>
     <Copyright>Copyright 2015, Google Inc.</Copyright>
     <AssemblyTitle>Google Protocol Buffers</AssemblyTitle>
-    <VersionPrefix>3.6.0</VersionPrefix>
+    <VersionPrefix>3.6.1</VersionPrefix>
     <Authors>Google Inc.</Authors>
     <TargetFrameworks>netstandard1.0;net45</TargetFrameworks>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
diff --git a/docs/options.md b/docs/options.md
index c9b2290a..529cce5d 100644
--- a/docs/options.md
+++ b/docs/options.md
@@ -184,3 +184,7 @@ with info about your project (name and website) so we can add an entry for you.
 1. API client generators
    * Website: ???
    * Extensions: 1048-1056
+
+1. Netifi Proteus
+   * Website: https://github.com/netifi-proteus
+   * Extensions: 1057
diff --git a/docs/third_party.md b/docs/third_party.md
index 7b0fb2df..f710b51a 100644
--- a/docs/third_party.md
+++ b/docs/third_party.md
@@ -129,6 +129,7 @@ GRPC (http://www.grpc.io/) is Google's RPC implementation for Protocol Buffers.
 * https://github.com/awakesecurity/gRPC-haskell (Haskell)
 * https://github.com/Yeolar/raster (C++)
 * https://github.com/jnordberg/wsrpc (JavaScript Node.js/Browser)
+* https://github.com/ppissias/xsrpcj (Java)
 
 ## Other Utilities
 
diff --git a/java/core/pom.xml b/java/core/pom.xml
index a7d4ea37..0c0fd8ff 100644
--- a/java/core/pom.xml
+++ b/java/core/pom.xml
@@ -6,7 +6,7 @@
   <parent>
     <groupId>com.google.protobuf</groupId>
     <artifactId>protobuf-parent</artifactId>
-    <version>3.6.0</version>
+    <version>3.6.1</version>
   </parent>
 
   <artifactId>protobuf-java</artifactId>
diff --git a/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java b/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java
index 35b31f15..ff670fd8 100644
--- a/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java
+++ b/java/core/src/main/java/com/google/protobuf/GeneratedMessageLite.java
@@ -1406,7 +1406,7 @@ public abstract class GeneratedMessageLite<
 
   /**
    * A serialized (serializable) form of the generated message.  Stores the
-   * message as a class name and a byte array.
+   * message as a class and a byte array.
    */
   protected static final class SerializedForm implements Serializable {
 
@@ -1416,6 +1416,9 @@ public abstract class GeneratedMessageLite<
 
     private static final long serialVersionUID = 0L;
 
+    // since v3.6.1
+    private final Class<?> messageClass;
+    // only included for backwards compatibility before messageClass was added
     private final String messageClassName;
     private final byte[] asBytes;
 
@@ -1424,7 +1427,8 @@ public abstract class GeneratedMessageLite<
      * @param regularForm the message to serialize
      */
     SerializedForm(MessageLite regularForm) {
-      messageClassName = regularForm.getClass().getName();
+      messageClass = regularForm.getClass();
+      messageClassName = messageClass.getName();
       asBytes = regularForm.toByteArray();
     }
 
@@ -1436,7 +1440,7 @@ public abstract class GeneratedMessageLite<
     @SuppressWarnings("unchecked")
     protected Object readResolve() throws ObjectStreamException {
       try {
-        Class<?> messageClass = Class.forName(messageClassName);
+        Class<?> messageClass = resolveMessageClass();
         java.lang.reflect.Field defaultInstanceField =
             messageClass.getDeclaredField("DEFAULT_INSTANCE");
         defaultInstanceField.setAccessible(true);
@@ -1463,7 +1467,7 @@ public abstract class GeneratedMessageLite<
     @Deprecated
     private Object readResolveFallback() throws ObjectStreamException {
       try {
-        Class<?> messageClass = Class.forName(messageClassName);
+        Class<?> messageClass = resolveMessageClass();
         java.lang.reflect.Field defaultInstanceField =
             messageClass.getDeclaredField("defaultInstance");
         defaultInstanceField.setAccessible(true);
@@ -1483,6 +1487,10 @@ public abstract class GeneratedMessageLite<
         throw new RuntimeException("Unable to understand proto buffer", e);
       }
     }
+
+    private Class<?> resolveMessageClass() throws ClassNotFoundException {
+      return messageClass != null ? messageClass : Class.forName(messageClassName);
+    }
   }
 
   /**
diff --git a/java/core/src/test/java/com/google/protobuf/GeneratedMessageTest.java b/java/core/src/test/java/com/google/protobuf/GeneratedMessageTest.java
index a4143cd4..4489dace 100644
--- a/java/core/src/test/java/com/google/protobuf/GeneratedMessageTest.java
+++ b/java/core/src/test/java/com/google/protobuf/GeneratedMessageTest.java
@@ -32,6 +32,7 @@ package com.google.protobuf;
 
 import com.google.protobuf.Descriptors.Descriptor;
 import com.google.protobuf.Descriptors.FieldDescriptor;
+import com.google.protobuf.Int32Value;
 import com.google.protobuf.test.UnittestImport;
 import protobuf_unittest.EnumWithNoOuter;
 import protobuf_unittest.MessageWithNoOuter;
@@ -853,6 +854,75 @@ public class GeneratedMessageTest extends TestCase {
     assertEquals(expected, actual);
   }
 
+  public void testDeserializeWithoutClassField() throws Exception {
+    // serialized form for version <=3.6.0
+    // just includes messageClassName and asBytes
+
+    // Int32Value.newBuilder().setValue(123).build()
+    byte[] int32ValueBytes = new byte[]{
+        -84, -19, 0, 5, 115, 114, 0, 55, 99, 111, 109, 46, 103, 111, 111,
+        103, 108, 101, 46, 112, 114, 111, 116, 111, 98, 117, 102, 46, 71,
+        101, 110, 101, 114, 97, 116, 101, 100, 77, 101, 115, 115, 97, 103,
+        101, 76, 105, 116, 101, 36, 83, 101, 114, 105, 97, 108, 105, 122,
+        101, 100, 70, 111, 114, 109, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 2, 91,
+        0, 7, 97, 115, 66, 121, 116, 101, 115, 116, 0, 2, 91, 66, 76, 0,
+        16, 109, 101, 115, 115, 97, 103, 101, 67, 108, 97, 115, 115, 78,
+        97, 109, 101, 116, 0, 18, 76, 106, 97, 118, 97, 47, 108, 97, 110,
+        103, 47, 83, 116, 114, 105, 110, 103, 59, 120, 112, 117, 114, 0,
+        2, 91, 66, -84, -13, 23, -8, 6, 8, 84, -32, 2, 0, 0, 120, 112, 0,
+        0, 0, 2, 8, 123, 116, 0, 30, 99, 111, 109, 46, 103, 111, 111, 103,
+        108, 101, 46, 112, 114, 111, 116, 111, 98, 117, 102, 46, 73, 110,
+        116, 51, 50, 86, 97, 108, 117, 101
+    };
+
+    ByteArrayInputStream bais = new ByteArrayInputStream(int32ValueBytes);
+    ObjectInputStream in = new ObjectInputStream(bais);
+    Int32Value int32Value = (Int32Value) in.readObject();
+    assertEquals(123, int32Value.getValue());
+  }
+
+  public void testDeserializeWithClassField() throws Exception {
+    // serialized form for version > 3.6.0
+    // includes messageClass, messageClassName (for compatibility), and asBytes
+
+    // Int32Value.newBuilder().setValue(123).build()
+    byte[] int32ValueBytes = new byte[]{
+        -84, -19, 0, 5, 115, 114, 0, 55, 99, 111, 109, 46, 103, 111, 111,
+        103, 108, 101, 46, 112, 114, 111, 116, 111, 98, 117, 102, 46, 71,
+        101, 110, 101, 114, 97, 116, 101, 100, 77, 101, 115, 115, 97, 103,
+        101, 76, 105, 116, 101, 36, 83, 101, 114, 105, 97, 108, 105, 122,
+        101, 100, 70, 111, 114, 109, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 3, 91,
+        0, 7, 97, 115, 66, 121, 116, 101, 115, 116, 0, 2, 91, 66, 76, 0,
+        12, 109, 101, 115, 115, 97, 103, 101, 67, 108, 97, 115, 115, 116,
+        0, 17, 76, 106, 97, 118, 97, 47, 108, 97, 110, 103, 47, 67, 108,
+        97, 115, 115, 59, 76, 0, 16, 109, 101, 115, 115, 97, 103, 101, 67,
+        108, 97, 115, 115, 78, 97, 109, 101, 116, 0, 18, 76, 106, 97, 118,
+        97, 47, 108, 97, 110, 103, 47, 83, 116, 114, 105, 110, 103, 59,
+        120, 112, 117, 114, 0, 2, 91, 66, -84, -13, 23, -8, 6, 8, 84, -32,
+        2, 0, 0, 120, 112, 0, 0, 0, 2, 8, 123, 118, 114, 0, 30, 99, 111,
+        109, 46, 103, 111, 111, 103, 108, 101, 46, 112, 114, 111, 116, 111,
+        98, 117, 102, 46, 73, 110, 116, 51, 50, 86, 97, 108, 117, 101, 0, 0,
+        0, 0, 0, 0, 0, 0, 2, 0, 2, 66, 0, 21, 109, 101, 109, 111, 105, 122,
+        101, 100, 73, 115, 73, 110, 105, 116, 105, 97, 108, 105, 122, 101,
+        100, 73, 0, 6, 118, 97, 108, 117, 101, 95, 120, 114, 0, 38, 99, 111,
+        109, 46, 103, 111, 111, 103, 108, 101, 46, 112, 114, 111, 116, 111,
+        98, 117, 102, 46, 71, 101, 110, 101, 114, 97, 116, 101, 100, 77,
+        101, 115, 115, 97, 103, 101, 86, 51, 0, 0, 0, 0, 0, 0, 0, 1, 2, 0,
+        1, 76, 0, 13, 117, 110, 107, 110, 111, 119, 110, 70, 105, 101, 108,
+        100, 115, 116, 0, 37, 76, 99, 111, 109, 47, 103, 111, 111, 103, 108,
+        101, 47, 112, 114, 111, 116, 111, 98, 117, 102, 47, 85, 110, 107,
+        110, 111, 119, 110, 70, 105, 101, 108, 100, 83, 101, 116, 59, 120,
+        112, 116, 0, 30, 99, 111, 109, 46, 103, 111, 111, 103, 108, 101, 46,
+        112, 114, 111, 116, 111, 98, 117, 102, 46, 73, 110, 116, 51, 50, 86,
+        97, 108, 117, 101
+    };
+
+    ByteArrayInputStream bais = new ByteArrayInputStream(int32ValueBytes);
+    ObjectInputStream in = new ObjectInputStream(bais);
+    Int32Value int32Value = (Int32Value) in.readObject();
+    assertEquals(123, int32Value.getValue());
+  }
+
   public void testEnumValues() {
     assertEquals(TestAllTypes.NestedEnum.BAR_VALUE, TestAllTypes.NestedEnum.BAR.getNumber());
     assertEquals(TestAllTypes.NestedEnum.BAZ_VALUE, TestAllTypes.NestedEnum.BAZ.getNumber());
diff --git a/java/pom.xml b/java/pom.xml
index 35d653b4..6526b650 100644
--- a/java/pom.xml
+++ b/java/pom.xml
@@ -11,7 +11,7 @@
 
   <groupId>com.google.protobuf</groupId>
   <artifactId>protobuf-parent</artifactId>
-  <version>3.6.0</version>
+  <version>3.6.1</version>
   <packaging>pom</packaging>
 
   <name>Protocol Buffers [Parent]</name>
@@ -92,7 +92,7 @@
       <plugins>
         <plugin>
           <artifactId>maven-compiler-plugin</artifactId>
-          <version>3.6.0</version>
+          <version>3.6.1</version>
           <configuration>
             <source>1.7</source>
             <target>1.7</target>
diff --git a/java/util/pom.xml b/java/util/pom.xml
index 8ea4a40d..f175cf15 100644
--- a/java/util/pom.xml
+++ b/java/util/pom.xml
@@ -6,7 +6,7 @@
   <parent>
     <groupId>com.google.protobuf</groupId>
     <artifactId>protobuf-parent</artifactId>
-    <version>3.6.0</version>
+    <version>3.6.1</version>
   </parent>
 
   <artifactId>protobuf-java-util</artifactId>
diff --git a/java/util/src/main/java/com/google/protobuf/util/FieldMaskTree.java b/java/util/src/main/java/com/google/protobuf/util/FieldMaskTree.java
index 7b4facc1..86f56ad9 100644
--- a/java/util/src/main/java/com/google/protobuf/util/FieldMaskTree.java
+++ b/java/util/src/main/java/com/google/protobuf/util/FieldMaskTree.java
@@ -240,7 +240,7 @@ final class FieldMaskTree {
               "Field \""
                   + field.getFullName()
                   + "\" is not a "
-                  + "singluar message field and cannot have sub-fields.");
+                  + "singular message field and cannot have sub-fields.");
           continue;
         }
         if (!source.hasField(field) && !destination.hasField(field)) {
diff --git a/java/util/src/main/java/com/google/protobuf/util/JsonFormat.java b/java/util/src/main/java/com/google/protobuf/util/JsonFormat.java
index 973f1517..955dfd86 100644
--- a/java/util/src/main/java/com/google/protobuf/util/JsonFormat.java
+++ b/java/util/src/main/java/com/google/protobuf/util/JsonFormat.java
@@ -50,6 +50,7 @@ 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.FieldDescriptor.Type;
 import com.google.protobuf.Descriptors.FileDescriptor;
 import com.google.protobuf.Descriptors.OneofDescriptor;
 import com.google.protobuf.DoubleValue;
@@ -1539,7 +1540,11 @@ public class JsonFormat {
         Object key = parseFieldValue(keyField, new JsonPrimitive(entry.getKey()), entryBuilder);
         Object value = parseFieldValue(valueField, entry.getValue(), entryBuilder);
         if (value == null) {
-          throw new InvalidProtocolBufferException("Map value cannot be null.");
+          if(ignoringUnknownFields && valueField.getType() == Type.ENUM) {
+            continue;
+          } else {
+            throw new InvalidProtocolBufferException("Map value cannot be null.");
+          }
         }
         entryBuilder.setField(keyField, key);
         entryBuilder.setField(valueField, value);
@@ -1557,8 +1562,12 @@ public class JsonFormat {
       for (int i = 0; i < array.size(); ++i) {
         Object value = parseFieldValue(field, array.get(i), builder);
         if (value == null) {
-          throw new InvalidProtocolBufferException(
-              "Repeated field elements cannot be null in field: " + field.getFullName());
+          if(ignoringUnknownFields && field.getType() == Type.ENUM) {
+            continue;
+          } else {
+            throw new InvalidProtocolBufferException(
+                  "Repeated field elements cannot be null in field: " + field.getFullName());
+          }
         }
         builder.addRepeatedField(field, value);
       }
@@ -1748,7 +1757,7 @@ public class JsonFormat {
           // an exception later.
         }
 
-        if (result == null) {
+        if (result == null && !ignoringUnknownFields) {
           throw new InvalidProtocolBufferException(
               "Invalid enum value: " + value + " for enum type: " + enumDescriptor.getFullName());
         }
diff --git a/java/util/src/test/java/com/google/protobuf/util/JsonFormatTest.java b/java/util/src/test/java/com/google/protobuf/util/JsonFormatTest.java
index d9bbe587..7637c267 100644
--- a/java/util/src/test/java/com/google/protobuf/util/JsonFormatTest.java
+++ b/java/util/src/test/java/com/google/protobuf/util/JsonFormatTest.java
@@ -161,6 +161,10 @@ public class JsonFormatTest extends TestCase {
     JsonFormat.parser().merge(json, builder);
   }
 
+  private void mergeFromJsonIgnoringUnknownFields(String json, Message.Builder builder) throws IOException {
+    JsonFormat.parser().ignoringUnknownFields().merge(json, builder);
+  }
+
   public void testAllFields() throws Exception {
     TestAllTypes.Builder builder = TestAllTypes.newBuilder();
     setAllFields(builder);
@@ -668,10 +672,22 @@ public class JsonFormatTest extends TestCase {
               + "}",
           builder);
       fail();
+        
     } catch (InvalidProtocolBufferException e) {
       // Exception expected.
     }
   }
+  
+  public void testMapEnumNullValueIsIgnored() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    mergeFromJsonIgnoringUnknownFields(
+        "{\n"
+            + "  \"int32ToEnumMap\": {\"1\": null}\n"
+            + "}",
+        builder);
+      TestMap map = builder.build();
+      assertEquals(0, map.getInt32ToEnumMapMap().entrySet().size());
+ }
 
   public void testParserAcceptNonQuotedObjectKey() throws Exception {
     TestMap.Builder builder = TestMap.newBuilder();
@@ -1172,7 +1188,40 @@ public class JsonFormatTest extends TestCase {
     String json = "{\n" + "  \"unknownField\": \"XXX\"\n" + "}";
     JsonFormat.parser().ignoringUnknownFields().merge(json, builder);
   }
-
+  
+  public void testParserIgnoringUnknownEnums() throws Exception {
+    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
+    String json = "{\n" + "  \"optionalNestedEnum\": \"XXX\"\n" + "}";
+    JsonFormat.parser().ignoringUnknownFields().merge(json, builder);
+    assertEquals(0, builder.getOptionalNestedEnumValue());
+  }
+  
+  public void testUnknownEnumMap() throws Exception {
+    TestMap.Builder builder = TestMap.newBuilder();
+    JsonFormat.parser().ignoringUnknownFields().merge(
+      "{\n"
+      + "  \"int32ToEnumMap\": {1: XXX, 2: FOO}"
+      + "}",
+      builder);
+        
+      assertEquals(NestedEnum.FOO, builder.getInt32ToEnumMapMap().get(2));
+      assertEquals(1, builder.getInt32ToEnumMapMap().size());
+  }
+  
+  public void testRepeatedUnknownEnum() throws Exception {
+    TestAllTypes.Builder builder = TestAllTypes.newBuilder();
+    JsonFormat.parser().ignoringUnknownFields().merge(
+      "{\n"
+      + "  \"repeatedNestedEnum\": [XXX, FOO, BAR, BAZ]"
+      + "}",
+      builder);
+          
+    assertEquals(NestedEnum.FOO, builder.getRepeatedNestedEnum(0));
+    assertEquals(NestedEnum.BAR, builder.getRepeatedNestedEnum(1));
+    assertEquals(NestedEnum.BAZ, builder.getRepeatedNestedEnum(2));
+    assertEquals(3, builder.getRepeatedNestedEnumList().size());
+  }
+  
   public void testParserIntegerEnumValue() throws Exception {
     TestAllTypes.Builder actualBuilder = TestAllTypes.newBuilder();
     mergeFromJson("{\n" + "  \"optionalNestedEnum\": 2\n" + "}", actualBuilder);
diff --git a/js/README.md b/js/README.md
index d8edca37..97fa7e29 100644
--- a/js/README.md
+++ b/js/README.md
@@ -1,7 +1,7 @@
 Protocol Buffers - Google's data interchange format
 ===================================================
 
-[![Build Status](https://travis-ci.org/google/protobuf.svg?branch=master)](https://travis-ci.org/google/protobuf)
+[![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/linux-javascript.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fubuntu%2Fjavascript%2Fcontinuous) [![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/macos-javascript.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fmacos%2Fjavascript%2Fcontinuous)
 
 Copyright 2008 Google Inc.
 
diff --git a/js/package.json b/js/package.json
index 325f2dcc..dd5b6371 100644
--- a/js/package.json
+++ b/js/package.json
@@ -1,6 +1,6 @@
 {
   "name": "google-protobuf",
-  "version": "3.6.0",
+  "version": "3.6.1",
   "description": "Protocol Buffers for JavaScript",
   "main": "google-protobuf.js",
   "files": [
@@ -22,5 +22,5 @@
     "url": "https://github.com/google/protobuf/tree/master/js"
   },
   "author": "Google Protocol Buffers Team",
-  "license" : "BSD-3-Clause"
+  "license": "BSD-3-Clause"
 }
diff --git a/kokoro/release/protoc/linux/build.sh b/kokoro/release/protoc/linux/build.sh
index 6c7049d7..f0cde494 100755
--- a/kokoro/release/protoc/linux/build.sh
+++ b/kokoro/release/protoc/linux/build.sh
@@ -11,6 +11,16 @@ git submodule update --init --recursive
 # Generate the configure script.
 ./autogen.sh
 
+# Cross-build for aarch64 and ppc64le. Note: we do these builds first to avoid
+# file permission issues. The Docker builds will create directories owned by
+# root, which causes problems if we try to add new artifacts to those
+# directories afterward.
+sudo apt install -y g++-aarch64-linux-gnu
+protoc-artifacts/build-protoc.sh linux aarch_64 protoc
+
+sudo apt install -y g++-powerpc64le-linux-gnu
+protoc-artifacts/build-protoc.sh linux ppcle_64 protoc
+
 # Use docker image to build linux artifacts.
 DOCKER_IMAGE_NAME=protobuf/protoc_$(sha1sum protoc-artifacts/Dockerfile | cut -f1 -d " ")
 docker pull $DOCKER_IMAGE_NAME
@@ -28,9 +38,3 @@ docker run -v $(pwd):/var/local/protobuf --rm $DOCKER_IMAGE_NAME \
   echo "Failed to build protoc for linux + x86_32."
   exit 1
 }
-
-# Cross-build for some architectures.
-# TODO(xiaofeng): It currently fails with "machine `aarch64' not recognized"
-# error.
-# sudo apt install -y g++-aarch64-linux-gnu
-# protoc-artifacts/build-protoc.sh linux aarch_64 protoc
diff --git a/objectivec/GPBUnknownField.m b/objectivec/GPBUnknownField.m
index 9d5c97f3..7fa8cade 100644
--- a/objectivec/GPBUnknownField.m
+++ b/objectivec/GPBUnknownField.m
@@ -32,6 +32,7 @@
 
 #import "GPBArray.h"
 #import "GPBCodedOutputStream_PackagePrivate.h"
+#import "GPBUnknownFieldSet.h"
 
 @implementation GPBUnknownField {
  @protected
diff --git a/objectivec/README.md b/objectivec/README.md
index 21ac07d8..528f5472 100644
--- a/objectivec/README.md
+++ b/objectivec/README.md
@@ -1,7 +1,7 @@
 Protocol Buffers - Google's data interchange format
 ===================================================
 
-[![Build Status](https://travis-ci.org/google/protobuf.svg?branch=master)](https://travis-ci.org/google/protobuf)
+[![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/macos-objectivec_cocoapods_integration.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fmacos%2Fobjectivec_cocoapods_integration%2Fcontinuous) [![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/macos-objectivec_ios_debug.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fmacos%2Fobjectivec_ios_debug%2Fcontinuous) [![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/macos-objectivec_ios_release.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fmacos%2Fobjectivec_ios_release%2Fcontinuous) [![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/macos-objectivec_osx.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fmacos%2Fobjectivec_osx%2Fcontinuous)
 
 Copyright 2008 Google Inc.
 
diff --git a/php/README.md b/php/README.md
index 967250a7..e307768d 100644
--- a/php/README.md
+++ b/php/README.md
@@ -17,7 +17,7 @@ generation functionality.
 To use PHP runtime library requires:
 
 - C extension: PHP 5.5, 5.6, or 7.
-- PHP package: PHP 5.5, 5.6 or 7.
+- [PHP package](http://php.net/downloads.php): PHP 5.5, 5.6 or 7.
 
 ## Installation
 
diff --git a/php/composer.json b/php/composer.json
index 34e0447c..20f6a45e 100644
--- a/php/composer.json
+++ b/php/composer.json
@@ -9,13 +9,20 @@
     "php": ">=5.5.0"
   },
   "require-dev": {
-    "phpunit/phpunit": ">=4.8.0"
+    "phpunit/phpunit": "^5|^4.8.0"
   },
   "autoload": {
     "psr-4": {
       "Google\\Protobuf\\": "src/Google/Protobuf",
-      "GPBMetadata\\Google\\Protobuf\\": "src/GPBMetadata/Google/Protobuf",
+      "GPBMetadata\\Google\\Protobuf\\": "src/GPBMetadata/Google/Protobuf"
+    }
+  },
+  "autoload-dev": {
+    "psr-4": {
       "": "tests/generated"
     }
+  },
+  "scripts": {
+    "test": "(cd tests && rm -rf generated && mkdir -p generated && ../../src/protoc --php_out=generated proto/empty/echo.proto proto/test.proto proto/test_include.proto proto/test_no_namespace.proto proto/test_prefix.proto proto/test_php_namespace.proto proto/test_empty_php_namespace.proto proto/test_reserved_enum_lower.proto proto/test_reserved_enum_upper.proto proto/test_reserved_enum_value_lower.proto proto/test_reserved_enum_value_upper.proto proto/test_reserved_message_lower.proto proto/test_reserved_message_upper.proto proto/test_service.proto proto/test_service_namespace.proto proto/test_descriptors.proto) && (cd ../src && ./protoc --php_out=../php/tests/generated -I../php/tests -I. ../php/tests/proto/test_import_descriptor_proto.proto) && vendor/bin/phpunit"
   }
 }
diff --git a/php/ext/google/protobuf/def.c b/php/ext/google/protobuf/def.c
index fa33830b..238a9247 100644
--- a/php/ext/google/protobuf/def.c
+++ b/php/ext/google/protobuf/def.c
@@ -253,7 +253,7 @@ PHP_METHOD(Descriptor, getField) {
 #else
     field_hashtable_value =
         field_descriptor_type->create_object(field_descriptor_type TSRMLS_CC);
-    --GC_REFCOUNT(field_hashtable_value);
+    GC_DELREF(field_hashtable_value);
 #endif
     FieldDescriptor *field_php =
         UNBOX_HASHTABLE_VALUE(FieldDescriptor, field_hashtable_value);
@@ -264,7 +264,7 @@ PHP_METHOD(Descriptor, getField) {
 #if PHP_MAJOR_VERSION < 7
   RETURN_ZVAL(field_hashtable_value, 1, 0);
 #else
-  ++GC_REFCOUNT(field_hashtable_value);
+  GC_ADDREF(field_hashtable_value);
   RETURN_OBJ(field_hashtable_value);
 #endif
 }
@@ -492,7 +492,7 @@ PHP_METHOD(FieldDescriptor, getEnumType) {
 #if PHP_MAJOR_VERSION < 7
   RETURN_ZVAL(desc, 1, 0);
 #else
-  ++GC_REFCOUNT(desc);
+  GC_ADDREF(desc);
   RETURN_OBJ(desc);
 #endif
 }
@@ -512,7 +512,7 @@ PHP_METHOD(FieldDescriptor, getMessageType) {
 #if PHP_MAJOR_VERSION < 7
   RETURN_ZVAL(desc, 1, 0);
 #else
-  ++GC_REFCOUNT(desc);
+  GC_ADDREF(desc);
   RETURN_OBJ(desc);
 #endif
 }
@@ -585,7 +585,7 @@ PHP_METHOD(Oneof, getField) {
 #if PHP_MAJOR_VERSION < 7
   RETURN_ZVAL(field_hashtable_value, 1, 0);
 #else
-  ++GC_REFCOUNT(field_hashtable_value);
+  GC_ADDREF(field_hashtable_value);
   RETURN_OBJ(field_hashtable_value);
 #endif
 }
@@ -703,7 +703,7 @@ PHP_METHOD(DescriptorPool, getGeneratedPool) {
 #if PHP_MAJOR_VERSION < 7
   RETURN_ZVAL(generated_pool_php, 1, 0);
 #else
-  ++GC_REFCOUNT(generated_pool_php);
+  GC_ADDREF(generated_pool_php);
   RETURN_OBJ(generated_pool_php);
 #endif
 }
@@ -713,7 +713,7 @@ PHP_METHOD(InternalDescriptorPool, getGeneratedPool) {
 #if PHP_MAJOR_VERSION < 7
   RETURN_ZVAL(internal_generated_pool_php, 1, 0);
 #else
-  ++GC_REFCOUNT(internal_generated_pool_php);
+  GC_ADDREF(internal_generated_pool_php);
   RETURN_OBJ(internal_generated_pool_php);
 #endif
 }
@@ -1033,7 +1033,7 @@ PHP_METHOD(DescriptorPool, getDescriptorByClassName) {
 #if PHP_MAJOR_VERSION < 7
   RETURN_ZVAL(desc, 1, 0);
 #else
-  ++GC_REFCOUNT(desc);
+  GC_ADDREF(desc);
   RETURN_OBJ(desc);
 #endif
 }
@@ -1070,7 +1070,7 @@ PHP_METHOD(DescriptorPool, getEnumDescriptorByClassName) {
 #if PHP_MAJOR_VERSION < 7
   RETURN_ZVAL(desc, 1, 0);
 #else
-  ++GC_REFCOUNT(desc);
+  GC_ADDREF(desc);
   RETURN_OBJ(desc);
 #endif
 }
diff --git a/php/ext/google/protobuf/encode_decode.c b/php/ext/google/protobuf/encode_decode.c
index 31a345b3..899b99f0 100644
--- a/php/ext/google/protobuf/encode_decode.c
+++ b/php/ext/google/protobuf/encode_decode.c
@@ -577,7 +577,7 @@ static void map_slot_value(upb_fieldtype_t type, const void* from,
       break;
     case UPB_TYPE_MESSAGE:
       *(zend_object**)to = Z_OBJ_P(*(zval**)from);
-      ++GC_REFCOUNT(*(zend_object**)to);
+      GC_ADDREF(*(zend_object**)to);
       break;
 #endif
     default:
diff --git a/php/ext/google/protobuf/map.c b/php/ext/google/protobuf/map.c
index ab8a518a..c5b500b5 100644
--- a/php/ext/google/protobuf/map.c
+++ b/php/ext/google/protobuf/map.c
@@ -192,7 +192,8 @@ static inline void php_proto_map_string_release(void *value) {
 }
 static inline void php_proto_map_object_release(void *value) {
   zend_object* object = *(zend_object**)value;
-  if(--GC_REFCOUNT(object) == 0) {
+  GC_DELREF(object);
+  if(GC_REFCOUNT(object) == 0) {
     zend_objects_store_del(object);
   }
 }
@@ -302,7 +303,8 @@ static bool map_index_unset(Map *intern, const char* keyval, int length) {
         zval_ptr_dtor(upb_value_memory(&old_value));
 #else
         zend_object* object = *(zend_object**)upb_value_memory(&old_value);
-        if(--GC_REFCOUNT(object) == 0) {
+        GC_DELREF(object);
+        if(GC_REFCOUNT(object) == 0) {
           zend_objects_store_del(object);
         }
 #endif
diff --git a/php/ext/google/protobuf/message.c b/php/ext/google/protobuf/message.c
index 76d85ab0..0efe090d 100644
--- a/php/ext/google/protobuf/message.c
+++ b/php/ext/google/protobuf/message.c
@@ -223,13 +223,7 @@ static zval* message_get_property_ptr_ptr(zval* object, zval* member, int type,
 }
 
 static HashTable* message_get_properties(zval* object TSRMLS_DC) {
-  // User cannot get property directly (e.g., $a = $m->a)
-  zend_error(E_USER_ERROR, "Cannot access private properties.");
-#if PHP_MAJOR_VERSION < 7
-  return zend_std_get_properties(object TSRMLS_CC);
-#else
-  return zend_std_get_properties(object);
-#endif
+  return NULL;
 }
 
 static HashTable* message_get_gc(zval* object, CACHED_VALUE** table,
@@ -871,7 +865,11 @@ PHP_PROTO_INIT_ENUMCLASS_START("Google\\Protobuf\\Field\\Cardinality",
   zend_declare_class_constant_long(field_cardinality_type,
                                    "CARDINALITY_REPEATED", 20, 3 TSRMLS_CC);
   const char *alias = "Google\\Protobuf\\Field_Cardinality";
+#if PHP_VERSION_ID < 70300
   zend_register_class_alias_ex(alias, strlen(alias), field_cardinality_type TSRMLS_CC);
+#else
+  zend_register_class_alias_ex(alias, strlen(alias), field_cardinality_type, 1);
+#endif
 PHP_PROTO_INIT_ENUMCLASS_END
 
 // -----------------------------------------------------------------------------
@@ -926,7 +924,11 @@ PHP_PROTO_INIT_ENUMCLASS_START("Google\\Protobuf\\Field\\Kind",
   zend_declare_class_constant_long(field_kind_type,
                                    "TYPE_SINT64", 11, 18 TSRMLS_CC);
   const char *alias = "Google\\Protobuf\\Field_Kind";
+#if PHP_VERSION_ID < 70300
   zend_register_class_alias_ex(alias, strlen(alias), field_kind_type TSRMLS_CC);
+#else
+  zend_register_class_alias_ex(alias, strlen(alias), field_kind_type, 1);
+#endif
 PHP_PROTO_INIT_ENUMCLASS_END
 
 // -----------------------------------------------------------------------------
diff --git a/php/ext/google/protobuf/protobuf.c b/php/ext/google/protobuf/protobuf.c
index da00302f..19cc5efb 100644
--- a/php/ext/google/protobuf/protobuf.c
+++ b/php/ext/google/protobuf/protobuf.c
@@ -104,7 +104,7 @@ void add_def_obj(const void* def, PHP_PROTO_HASHTABLE_VALUE value) {
 #if PHP_MAJOR_VERSION < 7
   Z_ADDREF_P(value);
 #else
-  ++GC_REFCOUNT(value);
+  GC_ADDREF(value);
 #endif
   add_to_table(upb_def_to_php_obj_map, def, value);
 }
@@ -117,7 +117,7 @@ void add_ce_obj(const void* ce, PHP_PROTO_HASHTABLE_VALUE value) {
 #if PHP_MAJOR_VERSION < 7
   Z_ADDREF_P(value);
 #else
-  ++GC_REFCOUNT(value);
+  GC_ADDREF(value);
 #endif
   add_to_table(ce_to_php_obj_map, ce, value);
 }
@@ -134,7 +134,7 @@ void add_proto_obj(const char* proto, PHP_PROTO_HASHTABLE_VALUE value) {
 #if PHP_MAJOR_VERSION < 7
   Z_ADDREF_P(value);
 #else
-  ++GC_REFCOUNT(value);
+  GC_ADDREF(value);
 #endif
   add_to_strtable(proto_to_php_obj_map, proto, strlen(proto), value);
 }
@@ -235,7 +235,8 @@ static PHP_GSHUTDOWN_FUNCTION(protobuf) {
 static void php_proto_hashtable_descriptor_release(zval* value) {
   void* ptr = Z_PTR_P(value);
   zend_object* object = *(zend_object**)ptr;
-  if(--GC_REFCOUNT(object) == 0) {
+  GC_DELREF(object);
+  if(GC_REFCOUNT(object) == 0) {
     zend_objects_store_del(object);
   }
   efree(ptr);
diff --git a/php/ext/google/protobuf/protobuf.h b/php/ext/google/protobuf/protobuf.h
index 3ef4c84b..9cb36dc2 100644
--- a/php/ext/google/protobuf/protobuf.h
+++ b/php/ext/google/protobuf/protobuf.h
@@ -37,7 +37,7 @@
 #include "upb.h"
 
 #define PHP_PROTOBUF_EXTNAME "protobuf"
-#define PHP_PROTOBUF_VERSION "3.6.0"
+#define PHP_PROTOBUF_VERSION "3.6.1"
 
 #define MAX_LENGTH_OF_INT64 20
 #define SIZEOF_INT64 8
@@ -50,6 +50,11 @@
 // PHP7 Wrappers
 // ----------------------------------------------------------------------------
 
+#if PHP_VERSION_ID < 70300
+#define GC_ADDREF(h) ++GC_REFCOUNT(h)
+#define GC_DELREF(h) --GC_REFCOUNT(h)
+#endif
+
 #if PHP_MAJOR_VERSION < 7
 
 #define php_proto_zend_literal const zend_literal*
@@ -500,7 +505,7 @@ static inline int php_proto_zend_hash_get_current_data_ex(HashTable* ht,
   PHP_PROTO_HASHTABLE_VALUE WRAPPED_OBJ;                                    \
   WRAPPED_OBJ = OBJ_CLASS_ENTRY->create_object(OBJ_CLASS_ENTRY);            \
   OBJ = UNBOX_HASHTABLE_VALUE(OBJ_TYPE, WRAPPED_OBJ);                       \
-  --GC_REFCOUNT(WRAPPED_OBJ);
+  GC_DELREF(WRAPPED_OBJ);
 
 #define PHP_PROTO_CE_DECLARE zend_class_entry*
 #define PHP_PROTO_CE_UNREF(ce) (ce)
diff --git a/php/ext/google/protobuf/storage.c b/php/ext/google/protobuf/storage.c
index e7910c85..a60fbe39 100644
--- a/php/ext/google/protobuf/storage.c
+++ b/php/ext/google/protobuf/storage.c
@@ -200,7 +200,7 @@ bool native_slot_set_by_array(upb_fieldtype_t type,
       }
 #else
       DEREF(memory, zval*) = value;
-      ++GC_REFCOUNT(Z_OBJ_P(value));
+      GC_ADDREF(Z_OBJ_P(value));
 #endif
       break;
     }
@@ -251,7 +251,7 @@ bool native_slot_set_by_map(upb_fieldtype_t type, const zend_class_entry* klass,
       }
 #else
       DEREF(memory, zend_object*) = Z_OBJ_P(value);
-      ++GC_REFCOUNT(Z_OBJ_P(value));
+      GC_ADDREF(Z_OBJ_P(value));
 #endif
       break;
     }
@@ -428,7 +428,7 @@ void native_slot_get_by_map_value(upb_fieldtype_t type, const void* memory,
         ZVAL_ZVAL(CACHED_PTR_TO_ZVAL_PTR(cache), value, 1, 0);
       }
 #else
-      ++GC_REFCOUNT(*(zend_object**)memory);
+      GC_ADDREF(*(zend_object**)memory);
       ZVAL_OBJ(cache, *(zend_object**)memory);
 #endif
       return;
diff --git a/php/tests/generated_class_test.php b/php/tests/generated_class_test.php
index 9f20bddc..8bac4e5e 100644
--- a/php/tests/generated_class_test.php
+++ b/php/tests/generated_class_test.php
@@ -1342,4 +1342,17 @@ class GeneratedClassTest extends TestBase
 
         TestUtil::assertTestMessage($m);
     }
+
+    #########################################################
+    # Test message equals.
+    #########################################################
+
+    public function testMessageEquals()
+    {
+        $m = new TestMessage();
+        TestUtil::setTestMessage($m);
+        $n = new TestMessage();
+        TestUtil::setTestMessage($n);
+        $this->assertEquals($m, $n);
+    }
 }
diff --git a/protoc-artifacts/README.md b/protoc-artifacts/README.md
index c25406dd..79fa30b8 100644
--- a/protoc-artifacts/README.md
+++ b/protoc-artifacts/README.md
@@ -119,7 +119,9 @@ target directory layout:
           protoc.exe
         + x86_32
           protoc.exe
-      + macos
+        + aarch_64
+          protoc.exe
+      + osx
         + x86_64
           protoc.exe
         + x86_32
@@ -137,7 +139,7 @@ Use the following command to deploy artifacts for the host platform to a
 staging repository.
 
 ```
-$ mvn clean deploy -P release
+$ mvn deploy -P release
 ```
 
 It creates a new staging repository. Go to
@@ -152,17 +154,19 @@ and upload these zip packages to the download section of the github
 release. For example:
 
 ```
-$ ./build-zip.sh 3.6.0
+$ ./build-zip.sh protoc 3.6.0
 ```
 
-The above command will create 5 zip files:
+The above command will create 7 zip files:
 
 ```
-dist/protoc-3.0.0-beta-4-win32.zip
-dist/protoc-3.0.0-beta-4-osx-x86_32.zip
-dist/protoc-3.0.0-beta-4-osx-x86_64.zip
-dist/protoc-3.0.0-beta-4-linux-x86_32.zip
-dist/protoc-3.0.0-beta-4-linux-x86_64.zip
+dist/protoc-3.6.0-win32.zip
+dist/protoc-3.6.0-osx-x86_32.zip
+dist/protoc-3.6.0-osx-x86_64.zip
+dist/protoc-3.6.0-linux-x86_32.zip
+dist/protoc-3.6.0-linux-x86_64.zip
+dist/protoc-3.6.0-linux-aarch_64.zip
+dist/protoc-3.6.0-linux-ppcle_64.zip
 ```
 
 Before running the script, make sure the artifacts are accessible from:
diff --git a/protoc-artifacts/build-protoc.sh b/protoc-artifacts/build-protoc.sh
index d6a3cfa3..b8d2eb87 100755
--- a/protoc-artifacts/build-protoc.sh
+++ b/protoc-artifacts/build-protoc.sh
@@ -86,6 +86,7 @@ checkArch ()
     format="$(objdump -f "$1" | grep -o "file format .*$" | grep -o "[^ ]*$")"
     echo Format=$format
     if [[ "$OS" == linux ]]; then
+      host_machine="$(uname -m)";
       if [[ "$ARCH" == x86_32 ]]; then
         assertEq $format "elf32-i386" $LINENO
       elif [[ "$ARCH" == x86_64 ]]; then
@@ -93,7 +94,11 @@ checkArch ()
       elif [[ "$ARCH" == aarch_64 ]]; then
         assertEq $format "elf64-little" $LINENO
       elif [[ "$ARCH" == ppcle_64 ]]; then
-        assertEq $format "elf64-powerpcle" $LINENO
+	if [[ $host_machine == ppc64le ]];then
+	  assertEq $format "elf64-powerpcle" $LINENO	
+	else	
+          assertEq $format "elf64-little" $LINENO
+	fi
       else
         fail "Unsupported arch: $ARCH"
       fi
@@ -132,12 +137,16 @@ checkDependencies ()
     dump_cmd='objdump -x '"$1"' | fgrep "DLL Name"'
     white_list="KERNEL32\.dll\|msvcrt\.dll"
   elif [[ "$OS" == linux ]]; then
+    host_machine="$(uname -m)";
     dump_cmd='ldd '"$1"
     if [[ "$ARCH" == x86_32 ]]; then
       white_list="linux-gate\.so\.1\|libpthread\.so\.0\|libm\.so\.6\|libc\.so\.6\|ld-linux\.so\.2"
     elif [[ "$ARCH" == x86_64 ]]; then
       white_list="linux-vdso\.so\.1\|libpthread\.so\.0\|libm\.so\.6\|libc\.so\.6\|ld-linux-x86-64\.so\.2"
     elif [[ "$ARCH" == ppcle_64 ]]; then
+      if [[ $host_machine != ppc64le ]];then      
+        dump_cmd='objdump -p '"$1"' | grep NEEDED'
+      fi
       white_list="linux-vdso64\.so\.1\|libpthread\.so\.0\|libm\.so\.6\|libc\.so\.6\|libz\.so\.1\|ld64\.so\.2"
     elif [[ "$ARCH" == aarch_64 ]]; then
       dump_cmd='objdump -p '"$1"' | grep NEEDED'
@@ -205,6 +214,7 @@ elif [[ "$(uname)" == Linux* ]]; then
       CONFIGURE_ARGS="$CONFIGURE_ARGS --host=aarch64-linux-gnu"
     elif [[ "$ARCH" == ppcle_64 ]]; then
       CXXFLAGS="$CXXFLAGS -m64"
+      CONFIGURE_ARGS="$CONFIGURE_ARGS --host=powerpc64le-linux-gnu"
     else
       fail "Unsupported arch: $ARCH"
     fi
diff --git a/protoc-artifacts/pom.xml b/protoc-artifacts/pom.xml
index 390cd220..55d9e91a 100644
--- a/protoc-artifacts/pom.xml
+++ b/protoc-artifacts/pom.xml
@@ -10,7 +10,7 @@
   </parent>
   <groupId>com.google.protobuf</groupId>
   <artifactId>protoc</artifactId>
-  <version>3.6.0</version>
+  <version>3.6.1</version>
   <packaging>pom</packaging>
   <name>Protobuf Compiler</name>
   <description>
diff --git a/python/README.md b/python/README.md
index 4b48225a..3eb78e56 100644
--- a/python/README.md
+++ b/python/README.md
@@ -1,7 +1,7 @@
 Protocol Buffers - Google's data interchange format
 ===================================================
 
-[![Build Status](https://travis-ci.org/google/protobuf.svg?branch=master)](https://travis-ci.org/google/protobuf)
+[![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/linux-python.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fubuntu%2Fpython%2Fcontinuous) [![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/linux-python_compatibility.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fubuntu%2Fpython_compatibility%2Fcontinuous) [![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/linux-python_cpp.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fubuntu%2Fpython_cpp%2Fcontinuous) [![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/macos-python.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fmacos%2Fpython%2Fcontinuous) [![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/macos-python_cpp.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fmacos%2Fpython_cpp%2Fcontinuous)
 
 Copyright 2008 Google Inc.
 
diff --git a/python/google/protobuf/__init__.py b/python/google/protobuf/__init__.py
index 58a3f040..249e18aa 100755
--- a/python/google/protobuf/__init__.py
+++ b/python/google/protobuf/__init__.py
@@ -30,7 +30,7 @@
 
 # Copyright 2007 Google Inc. All Rights Reserved.
 
-__version__ = '3.6.0'
+__version__ = '3.6.1'
 
 if __name__ != '__main__':
   try:
diff --git a/python/setup.py b/python/setup.py
index 335e9114..5ec4dcbd 100755
--- a/python/setup.py
+++ b/python/setup.py
@@ -185,6 +185,7 @@ if __name__ == '__main__':
         extra_compile_args.append('-Wno-write-strings')
         extra_compile_args.append('-Wno-invalid-offsetof')
         extra_compile_args.append('-Wno-sign-compare')
+        extra_compile_args.append('-std=c++11')
 
     # https://github.com/Theano/Theano/issues/4926
     if sys.platform == 'win32':
@@ -201,12 +202,6 @@ if __name__ == '__main__':
     if "clang" in os.popen('$CC --version 2> /dev/null').read():
       extra_compile_args.append('-Wno-shorten-64-to-32')
 
-    v, _, _ = platform.mac_ver()
-    if v:
-      extra_compile_args.append('-std=c++11')
-    elif os.getenv('KOKORO_BUILD_NUMBER') or os.getenv('KOKORO_BUILD_ID'):
-      extra_compile_args.append('-std=c++11')
-
     if warnings_as_errors in sys.argv:
       extra_compile_args.append('-Werror')
       sys.argv.remove(warnings_as_errors)
diff --git a/ruby/ext/google/protobuf_c/encode_decode.c b/ruby/ext/google/protobuf_c/encode_decode.c
index c7a7aa1a..d5842051 100644
--- a/ruby/ext/google/protobuf_c/encode_decode.c
+++ b/ruby/ext/google/protobuf_c/encode_decode.c
@@ -1109,7 +1109,7 @@ static void putmsg(VALUE msg_rb, const Descriptor* desc,
   TypedData_Get_Struct(msg_rb, MessageHeader, &Message_type, msg);
 
   if (desc != msg->descriptor) {
-    rb_raise(cTypeError,
+    rb_raise(rb_eArgError,
              "The type of given msg is '%s', expect '%s'.",
              upb_msgdef_fullname(msg->descriptor->msgdef),
              upb_msgdef_fullname(desc->msgdef));
diff --git a/ruby/google-protobuf.gemspec b/ruby/google-protobuf.gemspec
index cc7625d4..00a7ff36 100644
--- a/ruby/google-protobuf.gemspec
+++ b/ruby/google-protobuf.gemspec
@@ -1,6 +1,6 @@
 Gem::Specification.new do |s|
   s.name        = "google-protobuf"
-  s.version     = "3.6.0"
+  s.version     = "3.6.1"
   s.licenses    = ["BSD-3-Clause"]
   s.summary     = "Protocol Buffers"
   s.description = "Protocol Buffers are Google's data interchange format."
diff --git a/ruby/tests/encode_decode_test.rb b/ruby/tests/encode_decode_test.rb
index 95c2cfa4..f8b991cd 100644
--- a/ruby/tests/encode_decode_test.rb
+++ b/ruby/tests/encode_decode_test.rb
@@ -86,7 +86,7 @@ class EncodeDecodeTest < Test::Unit::TestCase
   end
 
   def test_encode_wrong_msg
-    e = assert_raise Google::Protobuf::TypeError do
+    e = assert_raise ::ArgumentError do
       m = A::B::C::TestMessage.new(
           :optional_int32 => 1,
       )
diff --git a/src/Makefile.am b/src/Makefile.am
index 9e55261a..af264a95 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -164,7 +164,7 @@ nobase_include_HEADERS =                                         \
 lib_LTLIBRARIES = libprotobuf-lite.la libprotobuf.la libprotoc.la
 
 libprotobuf_lite_la_LIBADD = $(PTHREAD_LIBS)
-libprotobuf_lite_la_LDFLAGS = -version-info 16:0:0 -export-dynamic -no-undefined
+libprotobuf_lite_la_LDFLAGS = -version-info 17:0:0 -export-dynamic -no-undefined
 if HAVE_LD_VERSION_SCRIPT
 libprotobuf_lite_la_LDFLAGS += -Wl,--version-script=$(srcdir)/libprotobuf-lite.map
 EXTRA_libprotobuf_lite_la_DEPENDENCIES = libprotobuf-lite.map
@@ -210,7 +210,7 @@ libprotobuf_lite_la_SOURCES =                                  \
   google/protobuf/io/zero_copy_stream_impl_lite.cc
 
 libprotobuf_la_LIBADD = $(PTHREAD_LIBS)
-libprotobuf_la_LDFLAGS = -version-info 16:0:0 -export-dynamic -no-undefined
+libprotobuf_la_LDFLAGS = -version-info 17:0:0 -export-dynamic -no-undefined
 if HAVE_LD_VERSION_SCRIPT
 libprotobuf_la_LDFLAGS += -Wl,--version-script=$(srcdir)/libprotobuf.map
 EXTRA_libprotobuf_la_DEPENDENCIES = libprotobuf.map
@@ -301,7 +301,7 @@ libprotobuf_la_SOURCES =                                       \
 nodist_libprotobuf_la_SOURCES = $(nodist_libprotobuf_lite_la_SOURCES)
 
 libprotoc_la_LIBADD = $(PTHREAD_LIBS) libprotobuf.la
-libprotoc_la_LDFLAGS = -version-info 16:0:0 -export-dynamic -no-undefined
+libprotoc_la_LDFLAGS = -version-info 17:0:0 -export-dynamic -no-undefined
 if HAVE_LD_VERSION_SCRIPT
 libprotoc_la_LDFLAGS += -Wl,--version-script=$(srcdir)/libprotoc.map
 EXTRA_libprotoc_la_DEPENDENCIES = libprotoc.map
diff --git a/src/README.md b/src/README.md
index 3cbeb3e6..4ca9a02a 100644
--- a/src/README.md
+++ b/src/README.md
@@ -1,7 +1,7 @@
 Protocol Buffers - Google's data interchange format
 ===================================================
 
-[![Build Status](https://travis-ci.org/google/protobuf.svg?branch=master)](https://travis-ci.org/google/protobuf) [![Build status](https://ci.appveyor.com/api/projects/status/73ctee6ua4w2ruin?svg=true)](https://ci.appveyor.com/project/protobuf/protobuf)
+[![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/linux-cpp_distcheck.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fubuntu%2Fcpp_distcheck%2Fcontinuous) [![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/macos-cpp.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fmacos%2Fcpp%2Fcontinuous) [![Build status](https://storage.googleapis.com/protobuf-kokoro-results/status-badge/macos-cpp_distcheck.png)](https://fusion.corp.google.com/projectanalysis/current/KOKORO/prod:protobuf%2Fgithub%2Fmaster%2Fmacos%2Fcpp_distcheck%2Fcontinuous) [![Build status](https://ci.appveyor.com/api/projects/status/73ctee6ua4w2ruin?svg=true)](https://ci.appveyor.com/project/protobuf/protobuf)
 
 Copyright 2008 Google Inc.
 
diff --git a/src/google/protobuf/any.pb.h b/src/google/protobuf/any.pb.h
index a47000c8..60d2e4cc 100644
--- a/src/google/protobuf/any.pb.h
+++ b/src/google/protobuf/any.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3006000 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
+#if 3006001 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/api.pb.h b/src/google/protobuf/api.pb.h
index 38e43dff..cea0ffe1 100644
--- a/src/google/protobuf/api.pb.h
+++ b/src/google/protobuf/api.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3006000 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
+#if 3006001 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/compiler/plugin.pb.h b/src/google/protobuf/compiler/plugin.pb.h
index 8ccdeae2..55569b5e 100644
--- a/src/google/protobuf/compiler/plugin.pb.h
+++ b/src/google/protobuf/compiler/plugin.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3006000 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
+#if 3006001 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/descriptor.pb.h b/src/google/protobuf/descriptor.pb.h
index b7ef7afc..99d66d00 100644
--- a/src/google/protobuf/descriptor.pb.h
+++ b/src/google/protobuf/descriptor.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3006000 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
+#if 3006001 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/duration.pb.h b/src/google/protobuf/duration.pb.h
index fabc5b00..b66e343a 100644
--- a/src/google/protobuf/duration.pb.h
+++ b/src/google/protobuf/duration.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3006000 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
+#if 3006001 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/empty.pb.h b/src/google/protobuf/empty.pb.h
index 13a4ab0b..7d88bb92 100644
--- a/src/google/protobuf/empty.pb.h
+++ b/src/google/protobuf/empty.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3006000 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
+#if 3006001 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/field_mask.pb.h b/src/google/protobuf/field_mask.pb.h
index 1db37eb2..b46d4997 100644
--- a/src/google/protobuf/field_mask.pb.h
+++ b/src/google/protobuf/field_mask.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3006000 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
+#if 3006001 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/source_context.pb.h b/src/google/protobuf/source_context.pb.h
index d6b45155..5d4dae81 100644
--- a/src/google/protobuf/source_context.pb.h
+++ b/src/google/protobuf/source_context.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3006000 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
+#if 3006001 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/struct.pb.h b/src/google/protobuf/struct.pb.h
index 1ccabb08..7ff4465b 100644
--- a/src/google/protobuf/struct.pb.h
+++ b/src/google/protobuf/struct.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3006000 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
+#if 3006001 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/stubs/bytestream.cc b/src/google/protobuf/stubs/bytestream.cc
index f4af6a50..8df2566a 100644
--- a/src/google/protobuf/stubs/bytestream.cc
+++ b/src/google/protobuf/stubs/bytestream.cc
@@ -113,7 +113,7 @@ char* GrowingArrayByteSink::GetBuffer(size_t* nbytes) {
   ShrinkToFit();
   char* b = buf_;
   *nbytes = size_;
-  buf_ = NULL;
+  buf_ = nullptr;
   size_ = capacity_ = 0;
   return b;
 }
diff --git a/src/google/protobuf/stubs/casts.h b/src/google/protobuf/stubs/casts.h
index 35e2dba0..b509f68c 100644
--- a/src/google/protobuf/stubs/casts.h
+++ b/src/google/protobuf/stubs/casts.h
@@ -89,7 +89,7 @@ inline To down_cast(From* f) {                   // so we only accept pointers
   }
 
 #if !defined(NDEBUG) && !defined(GOOGLE_PROTOBUF_NO_RTTI)
-  assert(f == NULL || dynamic_cast<To>(f) != NULL);  // RTTI: debug mode only!
+  assert(f == nullptr || dynamic_cast<To>(f) != nullptr);  // RTTI: debug mode only!
 #endif
   return static_cast<To>(f);
 }
@@ -107,7 +107,7 @@ inline To down_cast(From& f) {
 
 #if !defined(NDEBUG) && !defined(GOOGLE_PROTOBUF_NO_RTTI)
   // RTTI: debug mode only!
-  assert(dynamic_cast<ToAsPointer>(&f) != NULL);
+  assert(dynamic_cast<ToAsPointer>(&f) != nullptr);
 #endif
   return *static_cast<ToAsPointer>(&f);
 }
diff --git a/src/google/protobuf/stubs/common.cc b/src/google/protobuf/stubs/common.cc
index b54fd1c8..4b65eb89 100644
--- a/src/google/protobuf/stubs/common.cc
+++ b/src/google/protobuf/stubs/common.cc
@@ -175,12 +175,12 @@ void NullLogHandler(LogLevel /* level */, const char* /* filename */,
 static LogHandler* log_handler_ = &DefaultLogHandler;
 static int log_silencer_count_ = 0;
 
-static Mutex* log_silencer_count_mutex_ = NULL;
+static Mutex* log_silencer_count_mutex_ = nullptr;
 GOOGLE_PROTOBUF_DECLARE_ONCE(log_silencer_count_init_);
 
 void DeleteLogSilencerCount() {
   delete log_silencer_count_mutex_;
-  log_silencer_count_mutex_ = NULL;
+  log_silencer_count_mutex_ = nullptr;
 }
 void InitLogSilencerCount() {
   log_silencer_count_mutex_ = new Mutex;
@@ -281,9 +281,9 @@ void LogFinisher::operator=(LogMessage& other) {
 LogHandler* SetLogHandler(LogHandler* new_func) {
   LogHandler* old = internal::log_handler_;
   if (old == &internal::NullLogHandler) {
-    old = NULL;
+    old = nullptr;
   }
-  if (new_func == NULL) {
+  if (new_func == nullptr) {
     internal::log_handler_ = &internal::NullLogHandler;
   } else {
     internal::log_handler_ = new_func;
diff --git a/src/google/protobuf/stubs/common.h b/src/google/protobuf/stubs/common.h
index c5256d32..585e0128 100644
--- a/src/google/protobuf/stubs/common.h
+++ b/src/google/protobuf/stubs/common.h
@@ -101,27 +101,27 @@ namespace internal {
 
 // The current version, represented as a single integer to make comparison
 // easier:  major * 10^6 + minor * 10^3 + micro
-#define GOOGLE_PROTOBUF_VERSION 3006000
+#define GOOGLE_PROTOBUF_VERSION 3006001
 
 // A suffix string for alpha, beta or rc releases. Empty for stable releases.
 #define GOOGLE_PROTOBUF_VERSION_SUFFIX ""
 
 // The minimum library version which works with the current version of the
 // headers.
-#define GOOGLE_PROTOBUF_MIN_LIBRARY_VERSION 3006000
+#define GOOGLE_PROTOBUF_MIN_LIBRARY_VERSION 3006001
 
 // The minimum header version which works with the current version of
 // the library.  This constant should only be used by protoc's C++ code
 // generator.
-static const int kMinHeaderVersionForLibrary = 3006000;
+static const int kMinHeaderVersionForLibrary = 3006001;
 
 // The minimum protoc version which works with the current version of the
 // headers.
-#define GOOGLE_PROTOBUF_MIN_PROTOC_VERSION 3006000
+#define GOOGLE_PROTOBUF_MIN_PROTOC_VERSION 3006001
 
 // The minimum header version which works with the current version of
 // protoc.  This constant should only be used in VerifyVersion().
-static const int kMinHeaderVersionForProtoc = 3006000;
+static const int kMinHeaderVersionForProtoc = 3006001;
 
 // Verifies that the headers and libraries are compatible.  Use the macro
 // below to call this.
diff --git a/src/google/protobuf/stubs/common_unittest.cc b/src/google/protobuf/stubs/common_unittest.cc
index 798a2a27..3ce1c49a 100644
--- a/src/google/protobuf/stubs/common_unittest.cc
+++ b/src/google/protobuf/stubs/common_unittest.cc
@@ -100,14 +100,14 @@ TEST(LoggingTest, DefaultLogging) {
 }
 
 TEST(LoggingTest, NullLogging) {
-  LogHandler* old_handler = SetLogHandler(NULL);
+  LogHandler* old_handler = SetLogHandler(nullptr);
 
   CaptureTestStderr();
   GOOGLE_LOG(INFO   ) << "A message.";
   GOOGLE_LOG(WARNING) << "A warning.";
   GOOGLE_LOG(ERROR  ) << "An error.";
 
-  EXPECT_TRUE(SetLogHandler(old_handler) == NULL);
+  EXPECT_TRUE(SetLogHandler(old_handler) == nullptr);
 
   string text = GetCapturedTestStderr();
   EXPECT_EQ("", text);
@@ -179,9 +179,9 @@ class ClosureTest : public testing::Test {
   virtual void SetUp() {
     current_instance_ = this;
     a_ = 0;
-    b_ = NULL;
+    b_ = nullptr;
     c_.clear();
-    permanent_closure_ = NULL;
+    permanent_closure_ = nullptr;
   }
 
   void DeleteClosureInCallback() {
@@ -196,7 +196,7 @@ class ClosureTest : public testing::Test {
   static ClosureTest* current_instance_;
 };
 
-ClosureTest* ClosureTest::current_instance_ = NULL;
+ClosureTest* ClosureTest::current_instance_ = nullptr;
 
 TEST_F(ClosureTest, TestClosureFunction0) {
   Closure* closure = NewCallback(&SetA123Function);
@@ -321,7 +321,7 @@ TEST_F(ClosureTest, TestPermanentClosureFunction2) {
   EXPECT_EQ(789, a_);
   EXPECT_EQ(cstr, b_);
   a_ = 0;
-  b_ = NULL;
+  b_ = nullptr;
   closure->Run();
   EXPECT_EQ(789, a_);
   EXPECT_EQ(cstr, b_);
@@ -338,7 +338,7 @@ TEST_F(ClosureTest, TestPermanentClosureMethod2) {
   EXPECT_EQ(789, a_);
   EXPECT_EQ(cstr, b_);
   a_ = 0;
-  b_ = NULL;
+  b_ = nullptr;
   closure->Run();
   EXPECT_EQ(789, a_);
   EXPECT_EQ(cstr, b_);
diff --git a/src/google/protobuf/stubs/io_win32.cc b/src/google/protobuf/stubs/io_win32.cc
index 4407facb..f00a268f 100644
--- a/src/google/protobuf/stubs/io_win32.cc
+++ b/src/google/protobuf/stubs/io_win32.cc
@@ -91,7 +91,7 @@ struct CharTraits<wchar_t> {
 
 template <typename char_type>
 bool null_or_empty(const char_type* s) {
-  return s == NULL || *s == 0;
+  return s == nullptr || *s == 0;
 }
 
 // Returns true if the path starts with a drive letter, e.g. "c:".
@@ -225,7 +225,7 @@ bool as_windows_path(const char* path, wstring* result) {
 
 
   if (!is_path_absolute(wpath.c_str())) {
-    int size = ::GetCurrentDirectoryW(0, NULL);
+    int size = ::GetCurrentDirectoryW(0, nullptr);
     if (size == 0 && GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
       return false;
     }
@@ -316,17 +316,17 @@ FILE* fopen(const char* path, const char* mode) {
 #ifdef SUPPORT_LONGPATHS
   if (null_or_empty(path)) {
     errno = EINVAL;
-    return NULL;
+    return nullptr;
   }
   wstring wpath;
   if (!as_windows_path(path, &wpath)) {
     errno = ENOENT;
-    return NULL;
+    return nullptr;
   }
   wstring wmode;
   if (!strings::utf8_to_wcs(mode, &wmode)) {
     errno = EINVAL;
-    return NULL;
+    return nullptr;
   }
   return ::_wfopen(wpath.c_str(), wmode.c_str());
 #else
@@ -365,15 +365,15 @@ bool wcs_to_mbs(const WCHAR* s, string* out, bool outUtf8) {
   BOOL usedDefaultChar = FALSE;
   SetLastError(0);
   int size = WideCharToMultiByte(
-      outUtf8 ? CP_UTF8 : CP_ACP, 0, s, -1, NULL, 0, NULL,
-      outUtf8 ? NULL : &usedDefaultChar);
+      outUtf8 ? CP_UTF8 : CP_ACP, 0, s, -1, nullptr, 0, nullptr,
+      outUtf8 ? nullptr : &usedDefaultChar);
   if ((size == 0 && GetLastError() != ERROR_INSUFFICIENT_BUFFER)
       || usedDefaultChar) {
     return false;
   }
   std::unique_ptr<CHAR[]> astr(new CHAR[size]);
   WideCharToMultiByte(
-      outUtf8 ? CP_UTF8 : CP_ACP, 0, s, -1, astr.get(), size, NULL, NULL);
+      outUtf8 ? CP_UTF8 : CP_ACP, 0, s, -1, astr.get(), size, nullptr, nullptr);
   out->assign(astr.get());
   return true;
 }
@@ -386,7 +386,7 @@ bool mbs_to_wcs(const char* s, wstring* out, bool inUtf8) {
 
   SetLastError(0);
   int size =
-      MultiByteToWideChar(inUtf8 ? CP_UTF8 : CP_ACP, 0, s, -1, NULL, 0);
+      MultiByteToWideChar(inUtf8 ? CP_UTF8 : CP_ACP, 0, s, -1, nullptr, 0);
   if (size == 0 && GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
     return false;
   }
diff --git a/src/google/protobuf/stubs/io_win32_unittest.cc b/src/google/protobuf/stubs/io_win32_unittest.cc
index 9085ed91..6c70d461 100644
--- a/src/google/protobuf/stubs/io_win32_unittest.cc
+++ b/src/google/protobuf/stubs/io_win32_unittest.cc
@@ -112,7 +112,7 @@ void StripTrailingSlashes(string* str) {
 }
 
 bool GetEnvVarAsUtf8(const WCHAR* name, string* result) {
-  DWORD size = ::GetEnvironmentVariableW(name, NULL, 0);
+  DWORD size = ::GetEnvironmentVariableW(name, nullptr, 0);
   if (size > 0 && GetLastError() != ERROR_ENVVAR_NOT_FOUND) {
     std::unique_ptr<WCHAR[]> wcs(new WCHAR[size]);
     ::GetEnvironmentVariableW(name, wcs.get(), size);
@@ -128,7 +128,7 @@ bool GetEnvVarAsUtf8(const WCHAR* name, string* result) {
 }
 
 bool GetCwdAsUtf8(string* result) {
-  DWORD size = ::GetCurrentDirectoryW(0, NULL);
+  DWORD size = ::GetCurrentDirectoryW(0, nullptr);
   if (size > 0) {
     std::unique_ptr<WCHAR[]> wcs(new WCHAR[size]);
     ::GetCurrentDirectoryW(size, wcs.get());
@@ -201,7 +201,7 @@ bool IoWin32Test::CreateAllUnder(wstring path) {
   if (path.find(L"\\\\?\\") != 0) {
     path = wstring(L"\\\\?\\") + path;
   }
-  if (::CreateDirectoryW(path.c_str(), NULL) ||
+  if (::CreateDirectoryW(path.c_str(), nullptr) ||
       GetLastError() == ERROR_ALREADY_EXISTS ||
       GetLastError() == ERROR_ACCESS_DENIED) {
     return true;
@@ -210,7 +210,7 @@ bool IoWin32Test::CreateAllUnder(wstring path) {
     size_t pos = path.find_last_of(L'\\');
     if (pos != wstring::npos) {
       wstring parent(path, 0, pos);
-      if (CreateAllUnder(parent) && CreateDirectoryW(path.c_str(), NULL)) {
+      if (CreateAllUnder(parent) && CreateDirectoryW(path.c_str(), nullptr)) {
         return true;
       }
     }
@@ -352,8 +352,8 @@ TEST_F(IoWin32Test, MkdirTestNonAscii) {
 
   // Create a non-ASCII path.
   // Ensure that we can create the directory using SetCurrentDirectoryW.
-  EXPECT_TRUE(CreateDirectoryW((wtest_tmpdir + L"\\1").c_str(), NULL));
-  EXPECT_TRUE(CreateDirectoryW((wtest_tmpdir + L"\\1\\" + kUtf16Text).c_str(), NULL));
+  EXPECT_TRUE(CreateDirectoryW((wtest_tmpdir + L"\\1").c_str(), nullptr));
+  EXPECT_TRUE(CreateDirectoryW((wtest_tmpdir + L"\\1\\" + kUtf16Text).c_str(), nullptr));
   // Ensure that we can create a very similarly named directory using mkdir.
   // We don't attemp to delete and recreate the same directory, because on
   // Windows, deleting files and directories seems to be asynchronous.
@@ -386,7 +386,7 @@ TEST_F(IoWin32Test, ChdirTestNonAscii) {
   wstring wNonAscii(wtest_tmpdir + L"\\" + kUtf16Text);
   string nonAscii;
   EXPECT_TRUE(strings::wcs_to_utf8(wNonAscii.c_str(), &nonAscii));
-  EXPECT_TRUE(CreateDirectoryW(wNonAscii.c_str(), NULL));
+  EXPECT_TRUE(CreateDirectoryW(wNonAscii.c_str(), nullptr));
   WCHAR cwd[MAX_PATH];
   EXPECT_TRUE(GetCurrentDirectoryW(MAX_PATH, cwd));
   // Ensure that we can cd into the path using SetCurrentDirectoryW.
@@ -400,7 +400,7 @@ TEST_F(IoWin32Test, ChdirTestNonAscii) {
 }
 
 TEST_F(IoWin32Test, AsWindowsPathTest) {
-  DWORD size = GetCurrentDirectoryW(0, NULL);
+  DWORD size = GetCurrentDirectoryW(0, nullptr);
   std::unique_ptr<wchar_t[]> cwd_str(new wchar_t[size]);
   EXPECT_GT(GetCurrentDirectoryW(size, cwd_str.get()), 0);
   wstring cwd = wstring(L"\\\\?\\") + cwd_str.get();
diff --git a/src/google/protobuf/stubs/logging.h b/src/google/protobuf/stubs/logging.h
index f69605d9..f7c6d6a8 100644
--- a/src/google/protobuf/stubs/logging.h
+++ b/src/google/protobuf/stubs/logging.h
@@ -162,7 +162,7 @@ namespace internal {
 template<typename T>
 T* CheckNotNull(const char* /* file */, int /* line */,
                 const char* name, T* val) {
-  if (val == NULL) {
+  if (val == nullptr) {
     GOOGLE_LOG(FATAL) << name;
   }
   return val;
@@ -170,7 +170,7 @@ T* CheckNotNull(const char* /* file */, int /* line */,
 }  // namespace internal
 #define GOOGLE_CHECK_NOTNULL(A) \
   ::google::protobuf::internal::CheckNotNull(\
-      __FILE__, __LINE__, "'" #A "' must not be NULL", (A))
+      __FILE__, __LINE__, "'" #A "' must not be nullptr", (A))
 
 #ifdef NDEBUG
 
@@ -208,7 +208,7 @@ typedef void LogHandler(LogLevel level, const char* filename, int line,
 // also help end users figure out a problem.  If you would prefer that
 // these messages be sent somewhere other than stderr, call SetLogHandler()
 // to set your own handler.  This returns the old handler.  Set the handler
-// to NULL to ignore log messages (but see also LogSilencer, below).
+// to nullptr to ignore log messages (but see also LogSilencer, below).
 //
 // Obviously, SetLogHandler is not thread-safe.  You should only call it
 // at initialization time, and probably not from library code.  If you
diff --git a/src/google/protobuf/stubs/map_util.h b/src/google/protobuf/stubs/map_util.h
index 3e6d381f..2313e1f5 100644
--- a/src/google/protobuf/stubs/map_util.h
+++ b/src/google/protobuf/stubs/map_util.h
@@ -131,7 +131,7 @@ FindWithDefault(const Collection& collection,
 }
 
 // Returns a pointer to the const value associated with the given key if it
-// exists, or NULL otherwise.
+// exists, or nullptr otherwise.
 template <class Collection>
 const typename Collection::value_type::second_type*
 FindOrNull(const Collection& collection,
@@ -156,11 +156,11 @@ FindOrNull(Collection& collection,  // NOLINT
 }
 
 // Returns the pointer value associated with the given key. If none is found,
-// NULL is returned. The function is designed to be used with a map of keys to
+// nullptr is returned. The function is designed to be used with a map of keys to
 // pointers.
 //
 // This function does not distinguish between a missing key and a key mapped
-// to a NULL value.
+// to nullptr.
 template <class Collection>
 typename Collection::value_type::second_type
 FindPtrOrNull(const Collection& collection,
@@ -188,7 +188,7 @@ FindPtrOrNull(Collection& collection,  // NOLINT
 }
 
 // Finds the pointer value associated with the given key in a map whose values
-// are linked_ptrs. Returns NULL if key is not found.
+// are linked_ptrs. Returns nullptr if key is not found.
 template <class Collection>
 typename Collection::value_type::second_type::element_type*
 FindLinkedPtrOrNull(const Collection& collection,
@@ -215,7 +215,7 @@ FindLinkedPtrOrDie(const Collection& collection,
 }
 
 // Finds the value associated with the given key and copies it to *value (if not
-// NULL). Returns false if the key was not found, true otherwise.
+// nullptr). Returns false if the key was not found, true otherwise.
 template <class Collection, class Key, class Value>
 bool FindCopy(const Collection& collection,
               const Key& key,
@@ -447,7 +447,7 @@ LookupOrInsertNew(Collection* const collection,
   std::pair<typename Collection::iterator, bool> ret =
       collection->insert(typename Collection::value_type(
           key,
-          static_cast<typename Collection::value_type::second_type>(NULL)));
+          static_cast<typename Collection::value_type::second_type>(nullptr)));
   if (ret.second) {
     ret.first->second = new Element();
   }
@@ -466,7 +466,7 @@ LookupOrInsertNew(Collection* const collection,
   std::pair<typename Collection::iterator, bool> ret =
       collection->insert(typename Collection::value_type(
           key,
-          static_cast<typename Collection::value_type::second_type>(NULL)));
+          static_cast<typename Collection::value_type::second_type>(nullptr)));
   if (ret.second) {
     ret.first->second = new Element(arg);
   }
@@ -612,7 +612,7 @@ bool UpdateReturnCopy(Collection* const collection,
   return false;
 }
 
-// Tries to insert the given key-value pair into the collection. Returns NULL if
+// Tries to insert the given key-value pair into the collection. Returns nullptr if
 // the insert succeeds. Otherwise, returns a pointer to the existing value.
 //
 // This complements UpdateReturnCopy in that it allows to update only after
@@ -625,7 +625,7 @@ InsertOrReturnExisting(Collection* const collection,
                        const typename Collection::value_type& vt) {
   std::pair<typename Collection::iterator, bool> ret = collection->insert(vt);
   if (ret.second) {
-    return NULL;  // Inserted, no existing previous value.
+    return nullptr;  // Inserted, no existing previous value.
   } else {
     return &ret.first->second;  // Return address of already existing value.
   }
@@ -644,7 +644,7 @@ InsertOrReturnExisting(
 
 // Erases the collection item identified by the given key, and returns the value
 // associated with that key. It is assumed that the value (i.e., the
-// mapped_type) is a pointer. Returns NULL if the key was not found in the
+// mapped_type) is a pointer. Returns nullptr if the key was not found in the
 // collection.
 //
 // Examples:
@@ -665,7 +665,7 @@ typename Collection::value_type::second_type EraseKeyReturnValuePtr(
     const typename Collection::value_type::first_type& key) {
   typename Collection::iterator it = collection->find(key);
   if (it == collection->end()) {
-    return NULL;
+    return nullptr;
   }
   typename Collection::value_type::second_type v = it->second;
   collection->erase(it);
@@ -679,7 +679,7 @@ typename Collection::value_type::second_type EraseKeyReturnValuePtr(
 template <class MapContainer, class KeyContainer>
 void InsertKeysFromMap(const MapContainer& map_container,
                        KeyContainer* key_container) {
-  GOOGLE_CHECK(key_container != NULL);
+  GOOGLE_CHECK(key_container != nullptr);
   for (typename MapContainer::const_iterator it = map_container.begin();
        it != map_container.end(); ++it) {
     key_container->insert(it->first);
@@ -693,7 +693,7 @@ void InsertKeysFromMap(const MapContainer& map_container,
 template <class MapContainer, class KeyContainer>
 void AppendKeysFromMap(const MapContainer& map_container,
                        KeyContainer* key_container) {
-  GOOGLE_CHECK(key_container != NULL);
+  GOOGLE_CHECK(key_container != nullptr);
   for (typename MapContainer::const_iterator it = map_container.begin();
        it != map_container.end(); ++it) {
     key_container->push_back(it->first);
@@ -710,7 +710,7 @@ void AppendKeysFromMap(const MapContainer& map_container,
 template <class MapContainer, class KeyType>
 void AppendKeysFromMap(const MapContainer& map_container,
                        std::vector<KeyType>* key_container) {
-  GOOGLE_CHECK(key_container != NULL);
+  GOOGLE_CHECK(key_container != nullptr);
   // We now have the opportunity to call reserve(). Calling reserve() every
   // time is a bad idea for some use cases: libstdc++'s implementation of
   // vector<>::reserve() resizes the vector's backing store to exactly the
@@ -737,7 +737,7 @@ void AppendKeysFromMap(const MapContainer& map_container,
 template <class MapContainer, class ValueContainer>
 void AppendValuesFromMap(const MapContainer& map_container,
                          ValueContainer* value_container) {
-  GOOGLE_CHECK(value_container != NULL);
+  GOOGLE_CHECK(value_container != nullptr);
   for (typename MapContainer::const_iterator it = map_container.begin();
        it != map_container.end(); ++it) {
     value_container->push_back(it->second);
@@ -754,7 +754,7 @@ void AppendValuesFromMap(const MapContainer& map_container,
 template <class MapContainer, class ValueType>
 void AppendValuesFromMap(const MapContainer& map_container,
                          std::vector<ValueType>* value_container) {
-  GOOGLE_CHECK(value_container != NULL);
+  GOOGLE_CHECK(value_container != nullptr);
   // See AppendKeysFromMap for why this is done.
   if (value_container->empty()) {
     value_container->reserve(map_container.size());
diff --git a/src/google/protobuf/stubs/mutex.h b/src/google/protobuf/stubs/mutex.h
index 47edb7a3..2b1aab87 100644
--- a/src/google/protobuf/stubs/mutex.h
+++ b/src/google/protobuf/stubs/mutex.h
@@ -86,12 +86,12 @@ class LIBPROTOBUF_EXPORT MutexLock {
 typedef MutexLock ReaderMutexLock;
 typedef MutexLock WriterMutexLock;
 
-// MutexLockMaybe is like MutexLock, but is a no-op when mu is NULL.
+// MutexLockMaybe is like MutexLock, but is a no-op when mu is nullptr.
 class LIBPROTOBUF_EXPORT MutexLockMaybe {
  public:
   explicit MutexLockMaybe(Mutex *mu) :
-    mu_(mu) { if (this->mu_ != NULL) { this->mu_->Lock(); } }
-  ~MutexLockMaybe() { if (this->mu_ != NULL) { this->mu_->Unlock(); } }
+    mu_(mu) { if (this->mu_ != nullptr) { this->mu_->Lock(); } }
+  ~MutexLockMaybe() { if (this->mu_ != nullptr) { this->mu_->Unlock(); } }
  private:
   Mutex *const mu_;
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MutexLockMaybe);
@@ -109,7 +109,7 @@ class ThreadLocalStorage {
   }
   T* Get() {
     T* result = static_cast<T*>(pthread_getspecific(key_));
-    if (result == NULL) {
+    if (result == nullptr) {
       result = new T();
       pthread_setspecific(key_, result);
     }
diff --git a/src/google/protobuf/stubs/singleton.h b/src/google/protobuf/stubs/singleton.h
index 2e6ccbdb..5f0f4610 100644
--- a/src/google/protobuf/stubs/singleton.h
+++ b/src/google/protobuf/stubs/singleton.h
@@ -45,7 +45,7 @@ class Singleton {
   }
   static void ShutDown() {
     delete instance_;
-    instance_ = NULL;
+    instance_ = nullptr;
   }
  private:
   static void Init() {
@@ -59,7 +59,7 @@ template<typename T>
 ProtobufOnceType Singleton<T>::once_;
 
 template<typename T>
-T* Singleton<T>::instance_ = NULL;
+T* Singleton<T>::instance_ = nullptr;
 }  // namespace internal
 }  // namespace protobuf
 }  // namespace google
diff --git a/src/google/protobuf/stubs/statusor.h b/src/google/protobuf/stubs/statusor.h
index 29f869ad..b1c1e6b4 100644
--- a/src/google/protobuf/stubs/statusor.h
+++ b/src/google/protobuf/stubs/statusor.h
@@ -33,7 +33,7 @@
 // usable value, or an error Status explaining why such a value is
 // not present. To this end, StatusOr<T> does not allow its Status
 // value to be Status::OK. Further, StatusOr<T*> does not allow the
-// contained pointer to be NULL.
+// contained pointer to be nullptr.
 //
 // The primary use-case for StatusOr<T> is as the return value of a
 // function which may fail.
@@ -114,15 +114,15 @@ class StatusOr {
   StatusOr(const Status& status);  // NOLINT
 
   // Construct a new StatusOr with the given value. If T is a plain pointer,
-  // value must not be NULL. After calling this constructor, calls to
+  // value must not be nullptr. After calling this constructor, calls to
   // ValueOrDie() will succeed, and calls to status() will return OK.
   //
   // NOTE: Not explicit - we want to use StatusOr<T> as a return type
   // so it is convenient and sensible to be able to do 'return T()'
   // when when the return type is StatusOr<T>.
   //
-  // REQUIRES: if T is a plain pointer, value != NULL. This requirement is
-  // DCHECKed. In optimized builds, passing a NULL pointer here will have
+  // REQUIRES: if T is a plain pointer, value != nullptr. This requirement is
+  // DCHECKed. In optimized builds, passing a null pointer here will have
   // the effect of passing PosixErrorSpace::EINVAL as a fallback.
   StatusOr(const T& value);  // NOLINT
 
@@ -174,13 +174,13 @@ class LIBPROTOBUF_EXPORT StatusOrHelper {
 
 template<typename T>
 struct StatusOrHelper::Specialize {
-  // For non-pointer T, a reference can never be NULL.
+  // For non-pointer T, a reference can never be nullptr.
   static inline bool IsValueNull(const T& t) { return false; }
 };
 
 template<typename T>
 struct StatusOrHelper::Specialize<T*> {
-  static inline bool IsValueNull(const T* t) { return t == NULL; }
+  static inline bool IsValueNull(const T* t) { return t == nullptr; }
 };
 
 }  // namespace internal
@@ -202,7 +202,7 @@ inline StatusOr<T>::StatusOr(const Status& status) {
 template<typename T>
 inline StatusOr<T>::StatusOr(const T& value) {
   if (internal::StatusOrHelper::Specialize<T>::IsValueNull(value)) {
-    status_ = Status(error::INTERNAL, "NULL is not a vaild argument.");
+    status_ = Status(error::INTERNAL, "nullptr is not a vaild argument.");
   } else {
     status_ = Status::OK;
     value_ = value;
diff --git a/src/google/protobuf/stubs/stl_util.h b/src/google/protobuf/stubs/stl_util.h
index 9e4c82a4..2c265e92 100644
--- a/src/google/protobuf/stubs/stl_util.h
+++ b/src/google/protobuf/stubs/stl_util.h
@@ -82,7 +82,7 @@ inline void STLStringResizeUninitialized(string* s, size_t new_size) {
 // already work on all current implementations.
 inline char* string_as_array(string* str) {
   // DO NOT USE const_cast<char*>(str->data())! See the unittest for why.
-  return str->empty() ? NULL : &*str->begin();
+  return str->empty() ? nullptr : &*str->begin();
 }
 
 // STLDeleteElements() deletes all the elements in an STL container and clears
@@ -90,7 +90,7 @@ inline char* string_as_array(string* str) {
 // hash_set, or any other STL container which defines sensible begin(), end(),
 // and clear() methods.
 //
-// If container is NULL, this function is a no-op.
+// If container is nullptr, this function is a no-op.
 //
 // As an alternative to calling STLDeleteElements() directly, consider
 // ElementDeleter (defined below), which ensures that your container's elements
@@ -104,7 +104,7 @@ void STLDeleteElements(T *container) {
 
 // Given an STL container consisting of (key, value) pairs, STLDeleteValues
 // deletes all the "value" components and clears the container.  Does nothing
-// in the case it's given a NULL pointer.
+// in the case it's given a null pointer.
 
 template <class T>
 void STLDeleteValues(T *v) {
diff --git a/src/google/protobuf/stubs/stringpiece.cc b/src/google/protobuf/stubs/stringpiece.cc
index 989474b7..96a7d3da 100644
--- a/src/google/protobuf/stubs/stringpiece.cc
+++ b/src/google/protobuf/stubs/stringpiece.cc
@@ -115,7 +115,7 @@ stringpiece_ssize_type StringPiece::find(char c, size_type pos) const {
   }
   const char* result = static_cast<const char*>(
       memchr(ptr_ + pos, c, length_ - pos));
-  return result != NULL ? result - ptr_ : npos;
+  return result != nullptr ? result - ptr_ : npos;
 }
 
 stringpiece_ssize_type StringPiece::rfind(StringPiece s, size_type pos) const {
diff --git a/src/google/protobuf/stubs/stringpiece.h b/src/google/protobuf/stubs/stringpiece.h
index c7bdd810..6ab985cc 100644
--- a/src/google/protobuf/stubs/stringpiece.h
+++ b/src/google/protobuf/stubs/stringpiece.h
@@ -76,30 +76,30 @@
 //
 // There are several ways to create a null StringPiece:
 //   StringPiece()
-//   StringPiece(NULL)
-//   StringPiece(NULL, 0)
-// For all of the above, sp.data() == NULL, sp.length() == 0,
+//   StringPiece(nullptr)
+//   StringPiece(nullptr, 0)
+// For all of the above, sp.data() == nullptr, sp.length() == 0,
 // and sp.empty() == true.  Also, if you create a StringPiece with
-// a non-NULL pointer then sp.data() != NULL.  Once created,
-// sp.data() will stay either NULL or not-NULL, except if you call
+// a non-null pointer then sp.data() != nullptr.  Once created,
+// sp.data() will stay either nullptr or not-nullptr, except if you call
 // sp.clear() or sp.set().
 //
-// Thus, you can use StringPiece(NULL) to signal an out-of-band value
+// Thus, you can use StringPiece(nullptr) to signal an out-of-band value
 // that is different from other StringPiece values.  This is similar
-// to the way that const char* p1 = NULL; is different from
+// to the way that const char* p1 = nullptr; is different from
 // const char* p2 = "";.
 //
 // There are many ways to create an empty StringPiece:
 //   StringPiece()
-//   StringPiece(NULL)
-//   StringPiece(NULL, 0)
+//   StringPiece(nullptr)
+//   StringPiece(nullptr, 0)
 //   StringPiece("")
 //   StringPiece("", 0)
 //   StringPiece("abcdef", 0)
 //   StringPiece("abcdef"+6, 0)
 // For all of the above, sp.length() will be 0 and sp.empty() will be true.
-// For some empty StringPiece values, sp.data() will be NULL.
-// For some empty StringPiece values, sp.data() will not be NULL.
+// For some empty StringPiece values, sp.data() will be nullptr.
+// For some empty StringPiece values, sp.data() will not be nullptr.
 //
 // Be careful not to confuse: null StringPiece and empty StringPiece.
 // The set of empty StringPieces properly includes the set of null StringPieces.
@@ -109,20 +109,20 @@
 // All empty StringPiece values compare equal to each other.
 // Even a null StringPieces compares equal to a non-null empty StringPiece:
 //  StringPiece() == StringPiece("", 0)
-//  StringPiece(NULL) == StringPiece("abc", 0)
-//  StringPiece(NULL, 0) == StringPiece("abcdef"+6, 0)
+//  StringPiece(nullptr) == StringPiece("abc", 0)
+//  StringPiece(nullptr, 0) == StringPiece("abcdef"+6, 0)
 //
 // Look carefully at this example:
-//   StringPiece("") == NULL
+//   StringPiece("") == nullptr
 // True or false?  TRUE, because StringPiece::operator== converts
-// the right-hand side from NULL to StringPiece(NULL),
+// the right-hand side from nullptr to StringPiece(nullptr),
 // and then compares two zero-length spans of characters.
 // However, we are working to make this example produce a compile error.
 //
 // Suppose you want to write:
-//   bool TestWhat?(StringPiece sp) { return sp == NULL; }  // BAD
+//   bool TestWhat?(StringPiece sp) { return sp == nullptr; }  // BAD
 // Do not do that.  Write one of these instead:
-//   bool TestNull(StringPiece sp) { return sp.data() == NULL; }
+//   bool TestNull(StringPiece sp) { return sp.data() == nullptr; }
 //   bool TestEmpty(StringPiece sp) { return sp.empty(); }
 // The intent of TestWhat? is unclear.  Did you mean TestNull or TestEmpty?
 // Right now, TestWhat? behaves likes TestEmpty.
@@ -207,11 +207,11 @@ class LIBPROTOBUF_EXPORT StringPiece {
   //
   // Style guide exception granted:
   // http://goto/style-guide-exception-20978288
-  StringPiece() : ptr_(NULL), length_(0) {}
+  StringPiece() : ptr_(nullptr), length_(0) {}
 
   StringPiece(const char* str)  // NOLINT(runtime/explicit)
       : ptr_(str), length_(0) {
-    if (str != NULL) {
+    if (str != nullptr) {
       length_ = CheckedSsizeTFromSizeT(strlen(str));
     }
   }
@@ -248,7 +248,7 @@ class LIBPROTOBUF_EXPORT StringPiece {
   bool empty() const { return length_ == 0; }
 
   void clear() {
-    ptr_ = NULL;
+    ptr_ = nullptr;
     length_ = 0;
   }
 
@@ -260,7 +260,7 @@ class LIBPROTOBUF_EXPORT StringPiece {
 
   void set(const char* str) {
     ptr_ = str;
-    if (str != NULL)
+    if (str != nullptr)
       length_ = CheckedSsizeTFromSizeT(strlen(str));
     else
       length_ = 0;
@@ -309,7 +309,7 @@ class LIBPROTOBUF_EXPORT StringPiece {
   // for a StringPiece be called "as_string()".  We also leave the
   // "as_string()" method defined here for existing code.
   string ToString() const {
-    if (ptr_ == NULL) return string();
+    if (ptr_ == nullptr) return string();
     return string(data(), static_cast<size_type>(size()));
   }
 
diff --git a/src/google/protobuf/stubs/stringpiece_unittest.cc b/src/google/protobuf/stubs/stringpiece_unittest.cc
index a6a87595..d9a32d03 100644
--- a/src/google/protobuf/stubs/stringpiece_unittest.cc
+++ b/src/google/protobuf/stubs/stringpiece_unittest.cc
@@ -46,7 +46,7 @@ TEST(StringPiece, Ctor) {
   {
     // Null.
     StringPiece s10;
-    EXPECT_TRUE(s10.data() == NULL);
+    EXPECT_TRUE(s10.data() == nullptr);
     EXPECT_EQ(0, s10.length());
   }
 
@@ -148,8 +148,8 @@ TEST(StringPiece, ComparisonOperators) {
   EXPECT_EQ(result, StringPiece((x)).compare(StringPiece((y))) op 0)
 
   COMPARE(true, ==, "",   "");
-  COMPARE(true, ==, "", NULL);
-  COMPARE(true, ==, NULL, "");
+  COMPARE(true, ==, "", nullptr);
+  COMPARE(true, ==, nullptr, "");
   COMPARE(true, ==, "a",  "a");
   COMPARE(true, ==, "aa", "aa");
   COMPARE(false, ==, "a",  "");
@@ -253,7 +253,7 @@ TEST(StringPiece, STL1) {
 
   EXPECT_EQ(*d.data(), 'f');
   EXPECT_EQ(d.data()[5], 'r');
-  EXPECT_TRUE(e.data() == NULL);
+  EXPECT_TRUE(e.data() == nullptr);
 
   EXPECT_EQ(*a.begin(), 'a');
   EXPECT_EQ(*(b.begin() + 2), 'c');
@@ -312,7 +312,7 @@ TEST(StringPiece, STL2) {
   d.clear();
   EXPECT_EQ(d.size(), 0);
   EXPECT_TRUE(d.empty());
-  EXPECT_TRUE(d.data() == NULL);
+  EXPECT_TRUE(d.data() == nullptr);
   EXPECT_TRUE(d.begin() == d.end());
 
   EXPECT_EQ(StringPiece::npos, string::npos);
@@ -707,17 +707,17 @@ TEST(StringPiece, Contains) {
   EXPECT_TRUE(!a.contains(d));
 }
 
-TEST(StringPiece, NULLInput) {
+TEST(StringPiece, NullInput) {
   // we used to crash here, but now we don't.
-  StringPiece s(NULL);
-  EXPECT_EQ(s.data(), (const char*)NULL);
+  StringPiece s(nullptr);
+  EXPECT_EQ(s.data(), (const char*)nullptr);
   EXPECT_EQ(s.size(), 0);
 
-  s.set(NULL);
-  EXPECT_EQ(s.data(), (const char*)NULL);
+  s.set(nullptr);
+  EXPECT_EQ(s.data(), (const char*)nullptr);
   EXPECT_EQ(s.size(), 0);
 
-  // .ToString() on a StringPiece with NULL should produce the empty string.
+  // .ToString() on a StringPiece with nullptr should produce the empty string.
   EXPECT_EQ("", s.ToString());
   EXPECT_EQ("", s.as_string());
 }
diff --git a/src/google/protobuf/stubs/stringprintf.cc b/src/google/protobuf/stubs/stringprintf.cc
index d98b9b87..820bfe7f 100644
--- a/src/google/protobuf/stubs/stringprintf.cc
+++ b/src/google/protobuf/stubs/stringprintf.cc
@@ -76,7 +76,7 @@ void StringAppendV(string* dst, const char* format, va_list ap) {
       // Error or MSVC running out of space.  MSVC 8.0 and higher
       // can be asked about space needed with the special idiom below:
       va_copy(backup_ap, ap);
-      result = vsnprintf(NULL, 0, format, backup_ap);
+      result = vsnprintf(nullptr, 0, format, backup_ap);
       va_end(backup_ap);
     }
 
diff --git a/src/google/protobuf/stubs/stringprintf_unittest.cc b/src/google/protobuf/stubs/stringprintf_unittest.cc
index 15895e59..7fcbf500 100644
--- a/src/google/protobuf/stubs/stringprintf_unittest.cc
+++ b/src/google/protobuf/stubs/stringprintf_unittest.cc
@@ -91,7 +91,7 @@ TEST(StringPrintfTest, Multibyte) {
   // out of memory while trying to determine destination buffer size.
   // see b/4194543.
 
-  char* old_locale = setlocale(LC_CTYPE, NULL);
+  char* old_locale = setlocale(LC_CTYPE, nullptr);
   // Push locale with multibyte mode
   setlocale(LC_CTYPE, "en_US.utf8");
 
@@ -120,7 +120,7 @@ TEST(StringPrintfTest, Multibyte) {
 
 TEST(StringPrintfTest, NoMultibyte) {
   // No multibyte handling, but the string contains funny chars.
-  char* old_locale = setlocale(LC_CTYPE, NULL);
+  char* old_locale = setlocale(LC_CTYPE, nullptr);
   setlocale(LC_CTYPE, "POSIX");
   string value = StringPrintf("%.*s", 3, "\375\067s");
   setlocale(LC_CTYPE, old_locale);
diff --git a/src/google/protobuf/stubs/strutil.cc b/src/google/protobuf/stubs/strutil.cc
index 65f22a96..5bf9f2e6 100644
--- a/src/google/protobuf/stubs/strutil.cc
+++ b/src/google/protobuf/stubs/strutil.cc
@@ -87,7 +87,7 @@ void StripString(string* s, const char* remove, char replacewith) {
   const char * str_start = s->c_str();
   const char * str = str_start;
   for (str = strpbrk(str, remove);
-       str != NULL;
+       str != nullptr;
        str = strpbrk(str + 1, remove)) {
     (*s)[str - str_start] = replacewith;
   }
@@ -102,7 +102,7 @@ void ReplaceCharacters(string *s, const char *remove, char replacewith) {
   const char *str_start = s->c_str();
   const char *str = str_start;
   for (str = strpbrk(str, remove);
-       str != NULL;
+       str != nullptr;
        str = strpbrk(str + 1, remove)) {
     (*s)[str - str_start] = replacewith;
   }
@@ -280,7 +280,7 @@ static void JoinStringsIterator(const ITERATOR& start,
                                 const ITERATOR& end,
                                 const char* delim,
                                 string* result) {
-  GOOGLE_CHECK(result != NULL);
+  GOOGLE_CHECK(result != nullptr);
   result->clear();
   int delim_length = strlen(delim);
 
@@ -318,7 +318,7 @@ void JoinStrings(const std::vector<string>& components,
 //    result is truncated to 8 bits.
 //
 //    The second call stores its errors in a supplied string vector.
-//    If the string vector pointer is NULL, it reports the errors with LOG().
+//    If the string vector pointer is nullptr, it reports the errors with LOG().
 // ----------------------------------------------------------------------
 
 #define IS_OCTAL_DIGIT(c) (((c) >= '0') && ((c) <= '7'))
@@ -328,12 +328,12 @@ void JoinStrings(const std::vector<string>& components,
 #define LOG_STRING(LEVEL, VECTOR) GOOGLE_LOG_IF(LEVEL, false)
 
 int UnescapeCEscapeSequences(const char* source, char* dest) {
-  return UnescapeCEscapeSequences(source, dest, NULL);
+  return UnescapeCEscapeSequences(source, dest, nullptr);
 }
 
 int UnescapeCEscapeSequences(const char* source, char* dest,
                              std::vector<string> *errors) {
-  GOOGLE_DCHECK(errors == NULL) << "Error reporting not implemented.";
+  GOOGLE_DCHECK(errors == nullptr) << "Error reporting not implemented.";
 
   char* d = dest;
   const char* p = source;
@@ -458,13 +458,13 @@ int UnescapeCEscapeSequences(const char* source, char* dest,
 //    to be the same.
 //
 //    The second call stores its errors in a supplied string vector.
-//    If the string vector pointer is NULL, it reports the errors with LOG().
+//    If the string vector pointer is nullptr, it reports the errors with LOG().
 //
 //    In the first and second calls, the length of dest is returned. In the
 //    the third call, the new string is returned.
 // ----------------------------------------------------------------------
 int UnescapeCEscapeString(const string& src, string* dest) {
-  return UnescapeCEscapeString(src, dest, NULL);
+  return UnescapeCEscapeString(src, dest, nullptr);
 }
 
 int UnescapeCEscapeString(const string& src, string* dest,
@@ -478,7 +478,7 @@ int UnescapeCEscapeString(const string& src, string* dest,
 
 string UnescapeCEscapeString(const string& src) {
   std::unique_ptr<char[]> unescaped(new char[src.size() + 1]);
-  int len = UnescapeCEscapeSequences(src.c_str(), unescaped.get(), NULL);
+  int len = UnescapeCEscapeSequences(src.c_str(), unescaped.get(), nullptr);
   return string(unescaped.get(), len);
 }
 
@@ -982,7 +982,7 @@ static const char two_ASCII_digits[100][2] = {
 
 char* FastUInt32ToBufferLeft(uint32 u, char* buffer) {
   uint32 digits;
-  const char *ASCII_digits = NULL;
+  const char *ASCII_digits = nullptr;
   // The idea of this implementation is to trim the number of divides to as few
   // as possible by using multiplication and subtraction rather than mod (%),
   // and by outputting two digits at a time rather than one.
@@ -1073,7 +1073,7 @@ char* FastInt32ToBufferLeft(int32 i, char* buffer) {
 
 char* FastUInt64ToBufferLeft(uint64 u64, char* buffer) {
   int digits;
-  const char *ASCII_digits = NULL;
+  const char *ASCII_digits = nullptr;
 
   uint32 u = static_cast<uint32>(u64);
   if (u == u64) return FastUInt32ToBufferLeft(u, buffer);
@@ -1231,7 +1231,7 @@ static inline bool IsValidFloatChar(char c) {
 void DelocalizeRadix(char* buffer) {
   // Fast check:  if the buffer has a normal decimal point, assume no
   // translation is needed.
-  if (strchr(buffer, '.') != NULL) return;
+  if (strchr(buffer, '.') != nullptr) return;
 
   // Find the first unknown character.
   while (IsValidFloatChar(*buffer)) ++buffer;
@@ -1286,7 +1286,7 @@ char* DoubleToBuffer(double value, char* buffer) {
   // of a double.  This long double may have extra bits that make it compare
   // unequal to "value" even though it would be exactly equal if it were
   // truncated to a double.
-  volatile double parsed_value = strtod(buffer, NULL);
+  volatile double parsed_value = strtod(buffer, nullptr);
   if (parsed_value != value) {
     int snprintf_result =
       snprintf(buffer, kDoubleToBufferSize, "%.*g", DBL_DIG+2, value);
@@ -1318,7 +1318,7 @@ inline bool CaseEqual(StringPiece s1, StringPiece s2) {
 }
 
 bool safe_strtob(StringPiece str, bool* value) {
-  GOOGLE_CHECK(value != NULL) << "NULL output boolean given.";
+  GOOGLE_CHECK(value != nullptr) << "nullptr output boolean given.";
   if (CaseEqual(str, "true") || CaseEqual(str, "t") ||
       CaseEqual(str, "yes") || CaseEqual(str, "y") ||
       CaseEqual(str, "1")) {
@@ -1619,7 +1619,7 @@ void StrAppend(string *result,
 int GlobalReplaceSubstring(const string& substring,
                            const string& replacement,
                            string* s) {
-  GOOGLE_CHECK(s != NULL);
+  GOOGLE_CHECK(s != nullptr);
   if (s->empty() || substring.empty())
     return 0;
   string tmp;
@@ -1969,7 +1969,7 @@ int Base64UnescapeInternal(const char *src_param, int szsrc,
 //   for (i = 0; i < 255; i += 8) {
 //     for (j = i; j < i + 8; j++) {
 //       pos = strchr(Base64, j);
-//       if ((pos == NULL) || (j == 0))
+//       if ((pos == nullptr) || (j == 0))
 //         idx = -1;
 //       else
 //         idx = pos - Base64;
diff --git a/src/google/protobuf/stubs/strutil.h b/src/google/protobuf/stubs/strutil.h
index d16ffc34..d6bcbc32 100644
--- a/src/google/protobuf/stubs/strutil.h
+++ b/src/google/protobuf/stubs/strutil.h
@@ -285,7 +285,7 @@ inline string JoinStrings(const std::vector<string>& components,
 //
 //    Errors: In the first form of the call, errors are reported with
 //    LOG(ERROR). The same is true for the second form of the call if
-//    the pointer to the string std::vector is NULL; otherwise, error
+//    the pointer to the string std::vector is nullptr; otherwise, error
 //    messages are stored in the std::vector. In either case, the effect on
 //    the dest array is not defined, but rest of the source will be
 //    processed.
@@ -304,7 +304,7 @@ LIBPROTOBUF_EXPORT int UnescapeCEscapeSequences(const char* source, char* dest,
 //    to be the same.
 //
 //    The second call stores its errors in a supplied string vector.
-//    If the string vector pointer is NULL, it reports the errors with LOG().
+//    If the string vector pointer is nullptr, it reports the errors with LOG().
 //
 //    In the first and second calls, the length of dest is returned. In the
 //    the third call, the new string is returned.
diff --git a/src/google/protobuf/stubs/strutil_unittest.cc b/src/google/protobuf/stubs/strutil_unittest.cc
index 6bf0f598..9460a665 100644
--- a/src/google/protobuf/stubs/strutil_unittest.cc
+++ b/src/google/protobuf/stubs/strutil_unittest.cc
@@ -50,18 +50,18 @@ namespace {
 
 TEST(StringUtilityTest, ImmuneToLocales) {
   // Remember the old locale.
-  char* old_locale_cstr = setlocale(LC_NUMERIC, NULL);
-  ASSERT_TRUE(old_locale_cstr != NULL);
+  char* old_locale_cstr = setlocale(LC_NUMERIC, nullptr);
+  ASSERT_TRUE(old_locale_cstr != nullptr);
   string old_locale = old_locale_cstr;
 
   // Set the locale to "C".
-  ASSERT_TRUE(setlocale(LC_NUMERIC, "C") != NULL);
+  ASSERT_TRUE(setlocale(LC_NUMERIC, "C") != nullptr);
 
   EXPECT_EQ("1.5", SimpleDtoa(1.5));
   EXPECT_EQ("1.5", SimpleFtoa(1.5));
 
-  if (setlocale(LC_NUMERIC, "es_ES") == NULL &&
-      setlocale(LC_NUMERIC, "es_ES.utf8") == NULL) {
+  if (setlocale(LC_NUMERIC, "es_ES") == nullptr &&
+      setlocale(LC_NUMERIC, "es_ES.utf8") == nullptr) {
     // Some systems may not have the desired locale available.
     GOOGLE_LOG(WARNING)
       << "Couldn't set locale to es_ES.  Skipping this test.";
diff --git a/src/google/protobuf/stubs/substitute.cc b/src/google/protobuf/stubs/substitute.cc
index 7194a5b1..1ac9ab45 100644
--- a/src/google/protobuf/stubs/substitute.cc
+++ b/src/google/protobuf/stubs/substitute.cc
@@ -44,7 +44,7 @@ using internal::SubstituteArg;
 // to Substitute().
 static int CountSubstituteArgs(const SubstituteArg* const* args_array) {
   int count = 0;
-  while (args_array[count] != NULL && args_array[count]->size() != -1) {
+  while (args_array[count] != nullptr && args_array[count]->size() != -1) {
     ++count;
   }
   return count;
@@ -71,7 +71,7 @@ void SubstituteAndAppend(
     const SubstituteArg& arg6, const SubstituteArg& arg7,
     const SubstituteArg& arg8, const SubstituteArg& arg9) {
   const SubstituteArg* const args_array[] = {
-    &arg0, &arg1, &arg2, &arg3, &arg4, &arg5, &arg6, &arg7, &arg8, &arg9, NULL
+    &arg0, &arg1, &arg2, &arg3, &arg4, &arg5, &arg6, &arg7, &arg8, &arg9, nullptr
   };
 
   // Determine total size needed.
diff --git a/src/google/protobuf/stubs/substitute.h b/src/google/protobuf/stubs/substitute.h
index 7ee442af..e05ca8d8 100644
--- a/src/google/protobuf/stubs/substitute.h
+++ b/src/google/protobuf/stubs/substitute.h
@@ -93,7 +93,7 @@ class SubstituteArg {
 
   // Indicates that no argument was given.
   inline explicit SubstituteArg()
-    : text_(NULL), size_(-1) {}
+    : text_(nullptr), size_(-1) {}
 
   // Primitives
   // We don't overload for signed and unsigned char because if people are
diff --git a/src/google/protobuf/stubs/time.cc b/src/google/protobuf/stubs/time.cc
index 6def637e..a1e5e1e2 100644
--- a/src/google/protobuf/stubs/time.cc
+++ b/src/google/protobuf/stubs/time.cc
@@ -142,12 +142,12 @@ string FormatNanos(int32 nanos) {
 
 // Parses an integer from a null-terminated char sequence. The method
 // consumes at most "width" chars. Returns a pointer after the consumed
-// integer, or NULL if the data does not start with an integer or the
+// integer, or nullptr if the data does not start with an integer or the
 // integer value does not fall in the range of [min_value, max_value].
 const char* ParseInt(const char* data, int width, int min_value,
                      int max_value, int* result) {
   if (!ascii_isdigit(*data)) {
-    return NULL;
+    return nullptr;
   }
   int value = 0;
   for (int i = 0; i < width; ++i, ++data) {
@@ -161,7 +161,7 @@ const char* ParseInt(const char* data, int width, int min_value,
     *result = value;
     return data;
   } else {
-    return NULL;
+    return nullptr;
   }
 }
 
@@ -169,7 +169,7 @@ const char* ParseInt(const char* data, int width, int min_value,
 // "010" will be parsed to 10000000 nanos.
 const char* ParseNanos(const char* data, int32* nanos) {
   if (!ascii_isdigit(*data)) {
-    return NULL;
+    return nullptr;
   }
   int value = 0;
   int len = 0;
@@ -193,15 +193,15 @@ const char* ParseNanos(const char* data, int32* nanos) {
 const char* ParseTimezoneOffset(const char* data, int64* offset) {
   // Accept format "HH:MM". E.g., "08:00"
   int hour;
-  if ((data = ParseInt(data, 2, 0, 23, &hour)) == NULL) {
-    return NULL;
+  if ((data = ParseInt(data, 2, 0, 23, &hour)) == nullptr) {
+    return nullptr;
   }
   if (*data++ != ':') {
-    return NULL;
+    return nullptr;
   }
   int minute;
-  if ((data = ParseInt(data, 2, 0, 59, &minute)) == NULL) {
-    return NULL;
+  if ((data = ParseInt(data, 2, 0, 59, &minute)) == nullptr) {
+    return nullptr;
   }
   *offset = (hour * 60 + minute) * 60;
   return data;
@@ -264,7 +264,7 @@ bool DateTimeToSeconds(const DateTime& time, int64* seconds) {
 void GetCurrentTime(int64* seconds, int32* nanos) {
   // TODO(xiaofeng): Improve the accuracy of this implementation (or just
   // remove this method from protobuf).
-  *seconds = time(NULL);
+  *seconds = time(nullptr);
   *nanos = 0;
 }
 
@@ -290,37 +290,37 @@ bool ParseTime(const string& value, int64* seconds, int32* nanos) {
   //   With UTC offset: 2015-05-20T13:29:35.120-08:00
 
   // Parse year
-  if ((data = ParseInt(data, 4, 1, 9999, &time.year)) == NULL) {
+  if ((data = ParseInt(data, 4, 1, 9999, &time.year)) == nullptr) {
     return false;
   }
   // Expect '-'
   if (*data++ != '-') return false;
   // Parse month
-  if ((data = ParseInt(data, 2, 1, 12, &time.month)) == NULL) {
+  if ((data = ParseInt(data, 2, 1, 12, &time.month)) == nullptr) {
     return false;
   }
   // Expect '-'
   if (*data++ != '-') return false;
   // Parse day
-  if ((data = ParseInt(data, 2, 1, 31, &time.day)) == NULL) {
+  if ((data = ParseInt(data, 2, 1, 31, &time.day)) == nullptr) {
     return false;
   }
   // Expect 'T'
   if (*data++ != 'T') return false;
   // Parse hour
-  if ((data = ParseInt(data, 2, 0, 23, &time.hour)) == NULL) {
+  if ((data = ParseInt(data, 2, 0, 23, &time.hour)) == nullptr) {
     return false;
   }
   // Expect ':'
   if (*data++ != ':') return false;
   // Parse minute
-  if ((data = ParseInt(data, 2, 0, 59, &time.minute)) == NULL) {
+  if ((data = ParseInt(data, 2, 0, 59, &time.minute)) == nullptr) {
     return false;
   }
   // Expect ':'
   if (*data++ != ':') return false;
   // Parse second
-  if ((data = ParseInt(data, 2, 0, 59, &time.second)) == NULL) {
+  if ((data = ParseInt(data, 2, 0, 59, &time.second)) == nullptr) {
     return false;
   }
   if (!DateTimeToSeconds(time, seconds)) {
@@ -330,7 +330,7 @@ bool ParseTime(const string& value, int64* seconds, int32* nanos) {
   if (*data == '.') {
     ++data;
     // Parse nanoseconds.
-    if ((data = ParseNanos(data, nanos)) == NULL) {
+    if ((data = ParseNanos(data, nanos)) == nullptr) {
       return false;
     }
   } else {
@@ -342,14 +342,14 @@ bool ParseTime(const string& value, int64* seconds, int32* nanos) {
   } else if (*data == '+') {
     ++data;
     int64 offset;
-    if ((data = ParseTimezoneOffset(data, &offset)) == NULL) {
+    if ((data = ParseTimezoneOffset(data, &offset)) == nullptr) {
       return false;
     }
     *seconds -= offset;
   } else if (*data == '-') {
     ++data;
     int64 offset;
-    if ((data = ParseTimezoneOffset(data, &offset)) == NULL) {
+    if ((data = ParseTimezoneOffset(data, &offset)) == nullptr) {
       return false;
     }
     *seconds += offset;
diff --git a/src/google/protobuf/timestamp.pb.h b/src/google/protobuf/timestamp.pb.h
index 2800ecdd..88b22b23 100644
--- a/src/google/protobuf/timestamp.pb.h
+++ b/src/google/protobuf/timestamp.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3006000 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
+#if 3006001 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/type.pb.h b/src/google/protobuf/type.pb.h
index dfecb835..b155a8fd 100644
--- a/src/google/protobuf/type.pb.h
+++ b/src/google/protobuf/type.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3006000 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
+#if 3006001 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/src/google/protobuf/wrappers.pb.h b/src/google/protobuf/wrappers.pb.h
index a7b38162..7e3b7d40 100644
--- a/src/google/protobuf/wrappers.pb.h
+++ b/src/google/protobuf/wrappers.pb.h
@@ -13,7 +13,7 @@
 #error incompatible with your Protocol Buffer headers. Please update
 #error your headers.
 #endif
-#if 3006000 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
+#if 3006001 < GOOGLE_PROTOBUF_MIN_PROTOC_VERSION
 #error This file was generated by an older version of protoc which is
 #error incompatible with your Protocol Buffer headers. Please
 #error regenerate this file with a newer version of protoc.
diff --git a/tests.sh b/tests.sh
index 73be5c1d..5bb8ae39 100755
--- a/tests.sh
+++ b/tests.sh
@@ -507,18 +507,21 @@ build_php7.1() {
   phpunit
   popd
   pushd conformance
-  # TODO(teboring): Add it back
-  # make test_php
+  make test_php
   popd
 }
 
 build_php7.1_c() {
+  ENABLE_CONFORMANCE_TEST=$1
   use_php 7.1
   wget https://phar.phpunit.de/phpunit-5.6.0.phar -O /usr/bin/phpunit
   cd php/tests && /bin/bash ./test.sh 7.1 && cd ../..
-  pushd conformance
-  # make test_php_c
-  popd
+  if [ "$ENABLE_CONFORMANCE_TEST" = "true" ]
+  then
+    pushd conformance
+    make test_php_c
+    popd
+  fi
 }
 
 build_php7.1_zts_c() {
@@ -538,7 +541,7 @@ build_php_all_32() {
   build_php5.5_c
   build_php5.6_c
   build_php7.0_c
-  build_php7.1_c
+  build_php7.1_c $1
   build_php5.5_zts_c
   build_php5.6_zts_c
   build_php7.0_zts_c
@@ -546,7 +549,7 @@ build_php_all_32() {
 }
 
 build_php_all() {
-  build_php_all_32
+  build_php_all_32 true
   build_php_compatibility
 }