From d14cacd791ac553b5dfba5f303fc631b42f6e662 Mon Sep 17 00:00:00 2001
From: Petter Strandmark <petter.strandmark@gmail.com>
Date: Fri, 4 May 2018 20:37:03 +0200
Subject: [PATCH] Fix error in Clang UndefinedBehaviorSanitizer

Pointer Arguments to memcpy can not be null in UndefinedBehaviorSanitizer.
In this case, both the memory and the size was zero. This change allows
protoc to run under UndefinedBehaviorSanitizer.
---
 src/google/protobuf/io/printer.cc | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/google/protobuf/io/printer.cc b/src/google/protobuf/io/printer.cc
index 8493268dad..de67cef134 100644
--- a/src/google/protobuf/io/printer.cc
+++ b/src/google/protobuf/io/printer.cc
@@ -350,10 +350,12 @@ void Printer::CopyToBuffer(const char* data, int size) {
   while (size > buffer_size_) {
     // Data exceeds space in the buffer.  Copy what we can and request a
     // new buffer.
-    memcpy(buffer_, data, buffer_size_);
-    offset_ += buffer_size_;
-    data += buffer_size_;
-    size -= buffer_size_;
+    if (buffer_size_ > 0) {
+      memcpy(buffer_, data, buffer_size_);
+      offset_ += buffer_size_;
+      data += buffer_size_;
+      size -= buffer_size_;
+    }
     void* void_buffer;
     failed_ = !output_->Next(&void_buffer, &buffer_size_);
     if (failed_) return;