fix a rewriter crash on zero length files.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@50126 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 3 insertions, 1 deletions

diff --git a/include/clang/Rewrite/RewriteRope.h b/include/clang/Rewrite/RewriteRope.h
index 10ce4432ce..963c0715d9 100644
--- a/include/clang/Rewrite/RewriteRope.h
+++ b/include/clang/Rewrite/RewriteRope.h
@@ -204,7 +204,8 @@ public:
   
   void assign(const char *Start, const char *End) {
     clear();
-    Chunks.insert(0, MakeRopeString(Start, End));
+    if (Start != End)
+      Chunks.insert(0, MakeRopeString(Start, End));
   }
   
   void insert(unsigned Offset, const char *Start, const char *End) {
diff --git a/lib/Rewrite/RewriteRope.cpp b/lib/Rewrite/RewriteRope.cpp
index db55aa1cd4..7ee9fcced2 100644
--- a/lib/Rewrite/RewriteRope.cpp
+++ b/lib/Rewrite/RewriteRope.cpp
@@ -741,6 +741,7 @@ void RopePieceBTree::erase(unsigned Offset, unsigned NumBytes) {
 /// allocation instead of doing tons of tiny allocations.
 RopePiece RewriteRope::MakeRopeString(const char *Start, const char *End) {
   unsigned Len = End-Start;
+  assert(Len && "Zero length RopePiece is invalid!");
   
   // If we have space for this string in the current alloc buffer, use it.
   if (AllocOffs+Len <= AllocChunkSize) {