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

Ganesh Ajjanagadde gajjanag at mit.edu
Thu Dec 24 19:29:20 CET 2015

On Thu, Dec 24, 2015 at 10:12 AM, Nicolas George <george at nsup.org> wrote:
> Le quartidi 4 nivôse, an CCXXIV, Ganesh Ajjanagadde a écrit :
>> The prototype checking is already done above via check_mathfunc, which
>> follows your idea.
> No, it is not done, and especially not the way I suggested.
>>                    The trouble is that check_ld succeeds with/without
>> GNU_SOURCE, hence the issue reported by Michael.
> Exactly: check_mathfunc does not check for a prototype, it checks for an
> implementation.
>>                                                  However, the function
>> can only be used if GNU_SOURCE has been defined.
> Untrue. It can only be used if it has a prototype. As it happens, on YOUR
> libc, it is only defined if _GNU_SOURCE is defined (and that is with an
> underscore), it is just an implementation detail. Another libc could use
> another feature check macro, or declare the function unconditionally.

Sorry, confused the prototype with an implementation.

> The correct way is to check for a prototype, and this can be done as I
> suggested (but there may be better solutions).

Before I rework, to make sure I understand, why don't other math
functions merely test for a prototype as you suggest?

> Regards,
> --
>   Nicolas George
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