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

[Alexey Samsonov]

Reverted, sorry about the noise.

On Thu, Dec 4, 2014 at 2:58 PM, David Blaikie <dblaikie at gmail.com> wrote:

>
>
> On Thu, Dec 4, 2014 at 2:45 PM, Alexey Samsonov <vonosmas at gmail.com>
> wrote:
>
>> 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);
>>
>
> llvm/src/include/llvm/ADT/StringMap.h:185:48: error: offset of on
> non-standard-layout type 'llvm::StringMapEntry<llvm::MDString>'
> [-Werror,-Winvalid-offsetof]
>     char *Ptr = reinterpret_cast<char *>(&V) - offsetof(StringMapEntry,
> second);
>                                                ^
>  ~~~~~~
>
>
>>      return *reinterpret_cast<StringMapEntry*>(Ptr);
>>    }
>>    static const StringMapEntry &GetStringMapEntryFromValue(const ValueTy
>> &V) {
>>
>>
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>
>


-- 
Alexey Samsonov
vonosmas at gmail.com
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