[FFmpeg-devel] [PATCH] lavu/libm: add isfinite fallback

[Ganesh Ajjanagadde]

On Wed, Jan 13, 2016 at 8:07 PM, Ronald S. Bultje <rsbultje at gmail.com> wrote:
> Hi,
>
> On Wed, Jan 13, 2016 at 7:48 PM, Ganesh Ajjanagadde <gajjanagadde at gmail.com>
> wrote:
>>
>> On Wed, Jan 13, 2016 at 7:39 PM, Ronald S. Bultje <rsbultje at gmail.com>
>> wrote:
>> > Hi,
>> >
>> > On Wed, Jan 13, 2016 at 7:10 PM, Ganesh Ajjanagadde
>> > <gajjanagadde at gmail.com>
>> > wrote:
>> >>
>> >> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
>> >> ---
>> >>  configure        | 1 +
>> >>  libavutil/libm.h | 4 ++++
>> >>  2 files changed, 5 insertions(+)
>> >>
>> >> diff --git a/configure b/configure
>> >> index 415d939..a3aaa25 100755
>> >> --- a/configure
>> >> +++ b/configure
>> >> @@ -1821,6 +1821,7 @@ MATH_FUNCS="
>> >>      exp2f
>> >>      expf
>> >>      hypot
>> >> +    isfinite
>> >>      isinf
>> >>      isnan
>> >>      ldexpf
>> >> diff --git a/libavutil/libm.h b/libavutil/libm.h
>> >> index bc44dca..f01e5c6 100644
>> >> --- a/libavutil/libm.h
>> >> +++ b/libavutil/libm.h
>> >> @@ -343,6 +343,10 @@ static av_always_inline av_const int
>> >> avpriv_isnan(double x)
>> >>          : avpriv_isnan(x))
>> >>  #endif /* HAVE_ISNAN */
>> >>
>> >> +#if !HAVE_ISFINITE
>> >> +#define isfinite(x) (!(isinf(x) || isnan(x)))
>> >> +#endif /* HAVE_ISFINITE */
>> >
>> >
>> > This will break if you use isfinite(*ptr++) or something obscure like
>> > that.
>>
>> isfinite is a macro, not a function (man isfinite). Your point is
>> still valid though, really it should do a sizeof first (dbl/float),
>> then call a avpriv_isfinitef, avpriv_isfinite. I was being lazy.
>
>
> Does type matter much? Afaik, inf/nan will be maintained between
> float/double/long double.

It is important, see a commit I made earlier: 14ea4151d7c. In
particular, the main issue is that double to float conversion for dbl
outside float range is undefined behavior.

Anyway, it has been pushed. Thanks.

>
> Ronald