PR33902: Invalidate line number cache when adding more text to existing buffer.

This led to crashes as the line number cache would report a bogus line number
for a line of code, and we'd try to find a nonexistent column within the line
when printing diagnostics.

llvm-svn: 309503

1 files changed, 8 insertions, 0 deletions

diff --git a/clang/lib/Lex/ScratchBuffer.cpp b/clang/lib/Lex/ScratchBuffer.cpp
index cd8a27e76c2..e0f3966fce4 100644
--- a/clang/lib/Lex/ScratchBuffer.cpp
+++ b/clang/lib/Lex/ScratchBuffer.cpp
@@ -35,6 +35,14 @@ SourceLocation ScratchBuffer::getToken(const char *Buf, unsigned Len,
                                        const char *&DestPtr) {
   if (BytesUsed+Len+2 > ScratchBufSize)
     AllocScratchBuffer(Len+2);
+  else {
+    // Clear out the source line cache if it's already been computed.
+    // FIXME: Allow this to be incrementally extended.
+    auto *ContentCache = const_cast<SrcMgr::ContentCache *>(
+        SourceMgr.getSLocEntry(SourceMgr.getFileID(BufferStartLoc))
+                 .getFile().getContentCache());
+    ContentCache->SourceLineCache = nullptr;
+  }
 
   // Prefix the token with a \n, so that it looks like it is the first thing on
   // its own virtual line in caret diagnostics.