[FFmpeg-devel] [PATCH] lavu/libm: add copysign hack

[Ganesh Ajjanagadde]

On Sat, Dec 19, 2015 at 11:05 AM, Hendrik Leppkes <h.leppkes at gmail.com> wrote:
> On Sat, Dec 19, 2015 at 6:54 PM, Ganesh Ajjanagadde
> <gajjanagadde at gmail.com> wrote:
>> On Sat, Dec 19, 2015 at 8:06 AM, Ganesh Ajjanagadde
>> <gajjanagadde at gmail.com> wrote:
>>> On Sat, Dec 19, 2015 at 6:26 AM, Ronald S. Bultje <rsbultje at gmail.com> wrote:
>>>> Hi,
>>>>
>>>> On Fri, Dec 18, 2015 at 3:47 PM, Ganesh Ajjanagadde <gajjanagadde at gmail.com>
>>>> wrote:
>>>>>
>>>>> On Fri, Dec 18, 2015 at 12:41 PM, Ronald S. Bultje <rsbultje at gmail.com>
>>>>> wrote:
>>>>> > Hi,
>>>>> >
>>>>> > On Fri, Dec 18, 2015 at 2:18 PM, Ganesh Ajjanagadde
>>>>> > <gajjanagadde at gmail.com>
>>>>> > wrote:
>>>>> >>
>>>>> >> For systems with broken libms.
>>>>> >> Tested with NAN, -NAN, INFINITY, -INFINITY, +/-x for regular double x
>>>>> >> and
>>>>> >> combinations of these.
>>>>> >>
>>>>> >> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
>>>>> >> ---
>>>>> >>  configure        | 2 +-
>>>>> >>  libavutil/libm.h | 9 +++++++++
>>>>> >>  2 files changed, 10 insertions(+), 1 deletion(-)
>>>>> >>
>>>>> >> diff --git a/configure b/configure
>>>>> >> index 123d1df..7917386 100755
>>>>> >> --- a/configure
>>>>> >> +++ b/configure
>>>>> >> @@ -2852,7 +2852,7 @@ cropdetect_filter_deps="gpl"
>>>>> >>  delogo_filter_deps="gpl"
>>>>> >>  deshake_filter_select="pixelutils"
>>>>> >>  drawtext_filter_deps="libfreetype"
>>>>> >> -dynaudnorm_filter_deps="copysign erf"
>>>>> >> +dynaudnorm_filter_deps="erf"
>>>>> >>  ebur128_filter_deps="gpl"
>>>>> >>  eq_filter_deps="gpl"
>>>>> >>  fftfilt_filter_deps="avcodec"
>>>>> >> diff --git a/libavutil/libm.h b/libavutil/libm.h
>>>>> >> index 6d8bd68..637de19 100644
>>>>> >> --- a/libavutil/libm.h
>>>>> >> +++ b/libavutil/libm.h
>>>>> >> @@ -62,6 +62,15 @@ static av_always_inline float cbrtf(float x)
>>>>> >>  }
>>>>> >>  #endif
>>>>> >>
>>>>> >> +#if !HAVE_COPYSIGN
>>>>> >> +static av_always_inline double copysign(double x, double y)
>>>>> >> +{
>>>>> >> +    uint64_t vx = av_double2int(x);
>>>>> >> +    uint64_t vy = av_double2int(y);
>>>>> >> +    return av_int2double((vx & 0x7fffffffffffffff) | (vy &
>>>>> >> 0x8000000000000000));
>>>>> >> +}
>>>>> >> +#endif
>>>>> >
>>>>> >
>>>>> > Don't these need type suffixes (e.g. UINT64_C(val)) on some systems?
>>>>>
>>>>> I believe not, see
>>>>> http://en.cppreference.com/w/cpp/language/integer_literal
>>>>
>>>>
>>>> That document confirms that it is indeed legal for a compiler to read the
>>>> given literal on a 32bit or windows 64bit system as a 32bit max value, and
>>>> your literals don't fit in 32bit.
>>>
>>> How, the standard clearly says that the literal will be in the type
>>> int < unsigned int < long int < unsigned long int < long long int <
>>> unsigned long long int, wherever it first fits, and this is also clear
>>> from the link I sent.
>>>
>>> long long is at least 64 bits. I can't speak about broken
>>> compilers/environments that lack long long.
>>
>> This turns out to be the heart of the matter; as usual, Microsoft's
>> toolchain is fundamentally broken:
>> https://stackoverflow.com/questions/25626022/how-should-a-64-bit-integer-literal-be-represented-in-c.
>>
>
> Its behavior would appear to be valid C90 on Windows, since long int
> is 32-bit on that platform (which C90 calls for using, not long long)

Yes, I meant broken wrt C99 (as seen in the link), which most of our
platforms have and use. Basically, I meant that their C99 support is
half-baked and broken (of course not news).

>
> - Hendrik
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