Resubmit "[codeview] Make obj2yaml/yaml2obj support .debug$S..."

This was originally reverted because of some non-deterministic
failures on certain buildbots.  Luckily ASAN eventually caught
this as a stack-use-after-scope, so the fix is included in
this patch.

llvm-svn: 305393

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/DebugInfo/CodeView/DebugStringTableSubsection.cpp b/llvm/lib/DebugInfo/CodeView/DebugStringTableSubsection.cpp
index 6e647c4b976..de02525270c 100644
--- a/llvm/lib/DebugInfo/CodeView/DebugStringTableSubsection.cpp
+++ b/llvm/lib/DebugInfo/CodeView/DebugStringTableSubsection.cpp
@@ -58,6 +58,10 @@ Error DebugStringTableSubsection::commit(BinaryStreamWriter &Writer) const {
   uint32_t Begin = Writer.getOffset();
   uint32_t End = Begin + StringSize;
 
+  // Write a null string at the beginning.
+  if (auto EC = Writer.writeCString(StringRef()))
+    return EC;
+
   for (auto &Pair : Strings) {
     StringRef S = Pair.getKey();
     uint32_t Offset = Begin + Pair.getValue();
@@ -68,6 +72,7 @@ Error DebugStringTableSubsection::commit(BinaryStreamWriter &Writer) const {
   }
 
   Writer.setOffset(End);
+  assert((End - Begin) == StringSize);
   return Error::success();
 }