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

[Rafael Espíndola via llvm-commits]

Sorry, but I don't see toArrayRef anywhere.

Cheers,
Rafael


On 14 December 2015 at 19:38, David Blaikie <dblaikie at gmail.com> wrote:
> Ah, I just hit that myself while working on the type units in llvm-dwp.
>
> SetVector does have toArrayRef which is probably the better option than what
> you have (what you have there would be UB if the container is empty, for
> example).
>
> But yeah, I wouldn't mind if SetVector just had an "operator ArrayRef<T>".
> That seems reasonable, unambiguous, obvious goodness.
>
> On Tue, Dec 15, 2015 at 5:27 AM, Rafael Espíndola
> <rafael.espindola at gmail.com> wrote:
>>
>> 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
>
>