[FFmpeg-devel] [PATCH 00/15] replace pow(10, x) by exp10(x) across FFmpeg

[Ganesh Ajjanagadde]

On Thu, Dec 24, 2015 at 8:37 AM, Ronald S. Bultje <rsbultje at gmail.com> wrote:
> Hi,
>
> On Wed, Dec 23, 2015 at 7:49 PM, Ganesh Ajjanagadde <gajjanag at mit.edu>
> wrote:
>
>> What I meant was the following (I casually labelled it as ifdef, I
>> meant some preprocessor stuff):
>> #if !HAVE_EXP10 || !(defined(_GNU_SOURCE))
>> ...
>> #endif
>>
>> I have reproduced your issues via a minimal configure line, and the
>> above idea fixes those. Do you see any issues? Of course, there is the
>> theoretical one of a libc (more precisely libm) having exp10 without
>> GNU_SOURCE, but in that case it should just use the fallback.
>
>
> I don't like this as much. In all other instances of any other function
> whatsoever, we just check if the function exists. We should do the same
> thing here. If implemented correctly in configure, #if !HAVE_EXP10 should
> always work. If we can fail to compile when compiling some video filter, we
> can fail alike when testing for the feature in configure.

It is not easy to do via configure, as Michael points out since
GNU_SOURCE may get enabled from pkg-config and other steps in
configure. Basically then this will need to be deferred to a stage way
below in configure, once all cflags have been set to their values.
This will add IMHO greater complexity to configure than the ugly hack
above.

Ultimately, it is a question of which one is preferred. If you still
feel this way, I will delve a bit into configure to see what can be
done.

>
> Ronald
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