1 files changed, 8 insertions, 5 deletions
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());
 }