On Fri, Nov 13, 2015 at 07:38:31AM -0500, Ganesh Ajjanagadde wrote:
> On Fri, Nov 13, 2015 at 6:40 AM, Michael Niedermayer
> <mich...@niedermayer.cc> wrote:
> > On Thu, Nov 12, 2015 at 09:46:04PM -0500, Ganesh Ajjanagadde wrote:
> >> The rationale for this function is reflected in the documentation for
> >> it, and is copied here:
> >>
> >> Clip a double value into the long long amin-amax range.
> >> This function is needed because conversion of floating point to integers
> >> when
> >> it does not fit in the integer's representation does not necessarily
> >> saturate
> >> correctly (usually converted to a cvttsd2si on x86) which saturates numbers
> >> > INT64_MAX to INT64_MIN. The standard marks such conversions as undefined
> >> behavior, allowing this sort of mathematically bogus conversions. This
> >> provides
> >> a safe alternative that is slower obviously but assures safety and better
> >> mathematical behavior.
> >> API:
> >> @param a value to clip
> >> @param amin minimum value of the clip range
> >> @param amax maximum value of the clip range
> >> @return clipped value
> >>
> >> Note that a priori if one can guarantee from the calling side that the
> >> double is in range, it is safe to simply do an explicit/implicit cast,
> >> and that will be far faster. However, otherwise this function should be
> >> used.
> >>
> >> avutil minor version is bumped.
> >>
> >> Reviewed-by: Ronald S. Bultje <rsbul...@gmail.com>
> >> Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com>
> >> ---
> >> libavutil/common.h | 31 +++++++++++++++++++++++++++++++
> >> libavutil/version.h | 4 ++--
> >> 2 files changed, 33 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/libavutil/common.h b/libavutil/common.h
> >> index 6f0f582..4f60e72 100644
> >> --- a/libavutil/common.h
> >> +++ b/libavutil/common.h
> >> @@ -298,6 +298,34 @@ static av_always_inline av_const double
> >> av_clipd_c(double a, double amin, double
> >> else return a;
> >> }
> >>
> >> +/**
> >> + * Clip and convert a double value into the long long amin-amax range.
> >> + * This function is needed because conversion of floating point to
> >> integers when
> >> + * it does not fit in the integer's representation does not necessarily
> >> saturate
> >> + * correctly (usually converted to a cvttsd2si on x86) which saturates
> >> numbers
> >> + * > INT64_MAX to INT64_MIN. The standard marks such conversions as
> >> undefined
> >> + * behavior, allowing this sort of mathematically bogus conversions. This
> >> provides
> >> + * a safe alternative that is slower obviously but assures safety and
> >> better
> >> + * mathematical behavior.
> >> + * @param a value to clip
> >> + * @param amin minimum value of the clip range
> >> + * @param amax maximum value of the clip range
> >> + * @return clipped value
> >> + */
> >> +static av_always_inline av_const int64_t av_rint64_clip_c(double a,
> >> int64_t amin, int64_t amax)
> >> +{
> >> +#if defined(HAVE_AV_CONFIG_H) && defined(ASSERT_LEVEL) && ASSERT_LEVEL >=
> >> 2
> >> + if (amin > amax) abort();
> >> +#endif
> >> + // INT64_MAX+1,INT64_MIN are exactly representable as IEEE doubles
> >> + if (a >= 9223372036854775808.0)
> >> + return INT64_MAX;
> >> + if (a <= INT64_MIN)
> >> + return INT64_MIN;
> >> + // Finally safe to call av_clipd_c
> >> + return (int64_t)av_clipd_c(a, amin, amax);
> >> +}
> >
> > this fails to build here:
>
> Does not get compiled on my machine, that is why I missed this. Very
> strange, stdint is included in this header. Can you tell me what to
> pass to configure in order to reproduce this?i think "--enable-libutvideo" i suspect that any C++ file which includes this might trigger it but i didnt check that [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB The worst form of inequality is to try to make unequal things equal. -- Aristotle
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