Fix undefined memory management found by Clang's sanitizers.

See https://github.com/google/protobuf/issues/3752 for context.

2 files changed, 6 insertions, 4 deletions

diff --git a/src/google/protobuf/util/json_util.cc b/src/google/protobuf/util/json_util.cc
index c85f1899..ce3569ce 100644
--- a/src/google/protobuf/util/json_util.cc
+++ b/src/google/protobuf/util/json_util.cc
@@ -61,9 +61,11 @@ void ZeroCopyStreamByteSink::Append(const char* bytes, size_t len) {
       buffer_size_ -= len;
       return;
     }
-    memcpy(buffer_, bytes, buffer_size_);
-    bytes += buffer_size_;
-    len -= buffer_size_;
+    if (buffer_size_ > 0) {
+      memcpy(buffer_, bytes, buffer_size_);
+      bytes += buffer_size_;
+      len -= buffer_size_;
+    }
     if (!stream_->Next(&buffer_, &buffer_size_)) {
       // There isn't a way for ByteSink to report errors.
       buffer_size_ = 0;
diff --git a/src/google/protobuf/util/json_util.h b/src/google/protobuf/util/json_util.h
index f4f4380a..dee3ddba 100644
--- a/src/google/protobuf/util/json_util.h
+++ b/src/google/protobuf/util/json_util.h
@@ -179,7 +179,7 @@ namespace internal {
 class LIBPROTOBUF_EXPORT ZeroCopyStreamByteSink : public strings::ByteSink {
  public:
   explicit ZeroCopyStreamByteSink(io::ZeroCopyOutputStream* stream)
-      : stream_(stream), buffer_size_(0) {}
+      : stream_(stream), buffer_(NULL), buffer_size_(0) {}
   ~ZeroCopyStreamByteSink();
 
   virtual void Append(const char* bytes, size_t len);