2 files changed, 14 insertions, 6 deletions
diff --git a/lib/MC/MCAsmStreamer.cpp b/lib/MC/MCAsmStreamer.cpp
index e284e15bca..d4ef3ca826 100644
--- a/lib/MC/MCAsmStreamer.cpp
+++ b/lib/MC/MCAsmStreamer.cpp
@@ -136,6 +136,9 @@ void MCAsmStreamer::AddComment(const Twine &T) {
   T.toVector(CommentToEmit);
   // Each comment goes on its own line.
   CommentToEmit.push_back('\n');
+  
+  // Tell the comment stream that the vector changed underneath it.
+  CommentStream.resync();
 }
 
 void MCAsmStreamer::EmitCommentsAndEOL() {
@@ -158,7 +161,9 @@ void MCAsmStreamer::EmitCommentsAndEOL() {
     Comments = Comments.substr(Position+1);
   } while (!Comments.empty());
   
-  CommentStream.clear();
+  CommentToEmit.clear();
+  // Tell the comment stream that the vector changed underneath it.
+  CommentStream.resync();
 }
 
 
diff --git a/lib/Support/raw_ostream.cpp b/lib/Support/raw_ostream.cpp
index 7cd16c888b..10d7ec0701 100644
--- a/lib/Support/raw_ostream.cpp
+++ b/lib/Support/raw_ostream.cpp
@@ -562,11 +562,14 @@ raw_svector_ostream::~raw_svector_ostream() {
   flush();
 }
 
-/// clear - Flush the stream and clear the underlying vector.
-void raw_svector_ostream::clear() {
-  if (GetNumBytesInBuffer() == 0) flush();
-  
-  OS.clear();
+/// resync - This is called when the SmallVector we're appending to is changed
+/// outside of the raw_svector_ostream's control.  It is only safe to do this
+/// if the raw_svector_ostream has previously been flushed.
+void raw_svector_ostream::resync() {
+  assert(GetNumBytesInBuffer() == 0 && "Didn't flush before mutating vector");
+
+  if (OS.capacity() - OS.size() < 64)
+    OS.reserve(OS.capacity() * 2);
   SetBuffer(OS.end(), OS.capacity() - OS.size());
 }