From 36b525feb03846c09a4dc56afc92a372704e3171 Mon Sep 17 00:00:00 2001
From: Alexey Samsonov <vonosmas@gmail.com>
Date: Thu, 4 Dec 2014 22:45:31 +0000
Subject: [PATCH] Fix UBSan report in StringMap implementation.

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

llvm-svn: 223402
---
 llvm/include/llvm/ADT/StringMap.h | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/llvm/include/llvm/ADT/StringMap.h b/llvm/include/llvm/ADT/StringMap.h
index 2feb2ab0074d..06afe8426919 100644
--- a/llvm/include/llvm/ADT/StringMap.h
+++ b/llvm/include/llvm/ADT/StringMap.h
@@ -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) {