[llvm] r223402 - Fix UBSan report in StringMap implementation.

[Alexey Samsonov]

Author: samsonov
Date: Thu Dec  4 16:45:31 2014
New Revision: 223402

URL: http://llvm.org/viewvc/llvm-project?rev=223402&view=rev
Log:
Fix UBSan report in StringMap implementation.

Use offsetof() instead of a member access within null pointer.

Modified:
    llvm/trunk/include/llvm/ADT/StringMap.h

Modified: llvm/trunk/include/llvm/ADT/StringMap.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/StringMap.h?rev=223402&r1=223401&r2=223402&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/StringMap.h (original)
+++ llvm/trunk/include/llvm/ADT/StringMap.h Thu Dec  4 16:45:31 2014
@@ -182,10 +182,7 @@ public:
   /// GetStringMapEntryFromValue - Given a value that is known to be embedded
   /// into a StringMapEntry, return the StringMapEntry itself.
   static StringMapEntry &GetStringMapEntryFromValue(ValueTy &V) {
-    StringMapEntry *EPtr = 0;
-    char *Ptr = reinterpret_cast<char*>(&V) -
-                  (reinterpret_cast<char*>(&EPtr->second) -
-                   reinterpret_cast<char*>(EPtr));
+    char *Ptr = reinterpret_cast<char *>(&V) - offsetof(StringMapEntry, second);
     return *reinterpret_cast<StringMapEntry*>(Ptr);
   }
   static const StringMapEntry &GetStringMapEntryFromValue(const ValueTy &V) {