commit 009de5ea7a1913f0b4619cf514787bd52af38c28
Author: Michael Wu <mwu@mozilla.com>
Date:   Thu Sep 24 11:36:08 2015 -0400

    Return an empty string when a symbol isn't mangled

diff --git a/llvm/tools/clang/tools/libclang/CIndex.cpp b/llvm/tools/clang/tools/libclang/CIndex.cpp
index 9fa18d3..1253832 100644
--- a/llvm/tools/clang/tools/libclang/CIndex.cpp
+++ b/llvm/tools/clang/tools/libclang/CIndex.cpp
@@ -3891,6 +3891,10 @@ CXString clang_Cursor_getMangling(CXCursor C) {
   ASTContext &Ctx = ND->getASTContext();
   std::unique_ptr<MangleContext> MC(Ctx.createMangleContext());
 
+  // Don't mangle if we don't need to.
+  if (!MC->shouldMangleCXXName(ND))
+    return cxstring::createEmpty();
+
   std::string FrontendBuf;
   llvm::raw_string_ostream FrontendBufOS(FrontendBuf);
   MC->mangleName(ND, FrontendBufOS);