[FFmpeg-devel] [PATCH 2/2] Use gcc/clang builtins for av_sat_(add|sub)_64_c if available.

[James Almer]

On 5/4/2020 3:40 PM, Dale Curtis wrote:
> On Mon, May 4, 2020 at 11:19 AM James Almer <jamrial at gmail.com> wrote:
> 
>> On 5/4/2020 3:09 PM, Dale Curtis wrote:
>>> Bump. I have 5 integer overflow fuzzing issues awaiting our resolution of
>>> this discussion. Thanks.
>>>
>>> - dale
>>
>> What's the first version of clang with support for __builtin_*_overflow?
>> Because with your patch as is (Checking only __clang__), it's very
>> likely old clang builds could be broken. We have things like Clang 3 on
>> FATE right now.
>>
> 
> Clang 10.0 apparently:
> https://clang.llvm.org/docs/LanguageExtensions.html#feature-checking-macros -
> I'm fine with limiting support to where it works though. Attached patch
> does that.
> 
> 
>>
>> Also, does clang-cl define __clang__ and these builtins? Because maybe
>> we could remove that check and just keep the GCC + Intel one. The former
>> should in theory cover Clang builds that are reportedly compatible with
>> GCC >= 5.1
>>
> 
> Yes, clang-cl defines __clang__ and these builtins.
> 
> - dale

Ok, if __has_builtin() works for these then this patch LGTM, but I'd
prefer to first hear Michael's opinion about your reply to his question.