[FFmpeg-devel] [PATCH] configure: add check_feature_test_macro for exp10, exp10f

[Ganesh Ajjanagadde]

On Thu, Dec 24, 2015 at 9:55 AM, Nicolas George <george at nsup.org> wrote:
> Le quartidi 4 nivôse, an CCXXIV, Ganesh Ajjanagadde a écrit :
>> exp10 and exp10f need _GNU_SOURCE. check_mathfunc only tests if the
>> function is available, and not whether it is locked or unlocked via
>> _GNU_SOURCE.
>>
>> This adds some support to configure to test for _GNU_SOURCE and
>> accordingly report the existence of exp10, exp10f.
>
> I do not think this is a good solution. IMHO, the correct way would be to
> detect if the function has a prototype. It could probably be done by trying
> to cast it to int: if it is not declared, it will fail.

The prototype checking is already done above via check_mathfunc, which
follows your idea. The trouble is that check_ld succeeds with/without
GNU_SOURCE, hence the issue reported by Michael. However, the function
can only be used if GNU_SOURCE has been defined.

>
> Regards,
>
> --
>   Nicolas George