Fix undefined memory management found by Clang's sanitizers.

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

1 files changed, 6 insertions, 4 deletions

diff --git a/src/google/protobuf/text_format.cc b/src/google/protobuf/text_format.cc
index 2ea97785..eed2a768 100644
--- a/src/google/protobuf/text_format.cc
+++ b/src/google/protobuf/text_format.cc
@@ -1244,10 +1244,12 @@ class TextFormat::Printer::TextGenerator
     while (size > buffer_size_) {
       // Data exceeds space in the buffer.  Copy what we can and request a
       // new buffer.
-      memcpy(buffer_, data, buffer_size_);
-      data += buffer_size_;
-      size -= buffer_size_;
-      void* void_buffer;
+      if (buffer_size_ > 0) {
+        memcpy(buffer_, data, buffer_size_);
+        data += buffer_size_;
+        size -= buffer_size_;
+      }
+      void* void_buffer = NULL;
       failed_ = !output_->Next(&void_buffer, &buffer_size_);
       if (failed_) return;
       buffer_ = reinterpret_cast<char*>(void_buffer);