[llvm] r255258 - Avoid undefined behavior when vector is empty.

[Rafael Espíndola via llvm-commits]

On 13 December 2015 at 19:13, David Blaikie <dblaikie at gmail.com> wrote:
>
>
> On Thu, Dec 10, 2015 at 8:35 AM, Rafael Espindola via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
>>
>> Author: rafael
>> Date: Thu Dec 10 10:35:06 2015
>> New Revision: 255258
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=255258&view=rev
>> Log:
>> Avoid undefined behavior when vector is empty.
>>
>> Found by ubsan.
>>
>> Modified:
>>     llvm/trunk/include/llvm/ADT/SetVector.h
>>     llvm/trunk/lib/Linker/LinkModules.cpp
>>
>> Modified: llvm/trunk/include/llvm/ADT/SetVector.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/SetVector.h?rev=255258&r1=255257&r2=255258&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/include/llvm/ADT/SetVector.h (original)
>> +++ llvm/trunk/include/llvm/ADT/SetVector.h Thu Dec 10 10:35:06 2015
>> @@ -58,6 +58,8 @@ public:
>>      insert(Start, End);
>>    }
>>
>> +  ArrayRef<T> getArrayRef() const { return vector_; }
>> +
>>    /// \brief Determine if the SetVector is empty or not.
>>    bool empty() const {
>>      return vector_.empty();
>>
>> Modified: llvm/trunk/lib/Linker/LinkModules.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Linker/LinkModules.cpp?rev=255258&r1=255257&r2=255258&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/Linker/LinkModules.cpp (original)
>> +++ llvm/trunk/lib/Linker/LinkModules.cpp Thu Dec 10 10:35:06 2015
>> @@ -772,8 +772,7 @@ bool ModuleLinker::run() {
>>        Internalize.insert(GV->getName());
>>    }
>>
>> -  if (Mover.move(SrcM,
>> -                 makeArrayRef(&*ValuesToLink.begin(),
>> ValuesToLink.size()),
>
>
> Isn't vector already implicitly convertible to ArrayRef? (I guess there's
> something else at work heer - 'move' is a function template & has weird arg
> deduction issues? something else?)

ValuesToLink is a SetVector which is not implicitly convertible to
ArrayRef. Should it be?

Cheers,
Rafael