[PATCH] Fix unconditional dereference of a WeakVH in CGDebugInfo TypeCache

Reid Kleckner rnk at google.com
Tue Mar 4 10:37:14 PST 2014


Hi dblaikie,

This fails during a clang-cl self-host on Windows on
MachineLoopInfo.cpp.  I don't understand why.  I assume a recent change
caused it, but I haven't isolated which one.  However, this change by
itself appears correct, since the earlier code uses null checks after
WeakVH loads.

http://llvm-reviews.chandlerc.com/D2944

Files:
  lib/CodeGen/CGDebugInfo.cpp

Index: lib/CodeGen/CGDebugInfo.cpp
===================================================================
--- lib/CodeGen/CGDebugInfo.cpp
+++ lib/CodeGen/CGDebugInfo.cpp
@@ -3341,7 +3341,8 @@
   // up the final type in the type cache.
   for (std::vector<void *>::const_iterator RI = RetainedTypes.begin(),
          RE = RetainedTypes.end(); RI != RE; ++RI)
-    DBuilder.retainType(llvm::DIType(cast<llvm::MDNode>(TypeCache[*RI])));
+    if (llvm::Value *V = TypeCache[*RI])
+      DBuilder.retainType(llvm::DIType(cast<llvm::MDNode>(V)));
 
   DBuilder.finalize();
 }
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