On Sat, Jul 13, 2024 at 04:44:03PM +0200, epira...@gmail.com wrote:
> On 13 Jul 2024, at 2:47, Andreas Rheinhardt wrote:
>
> > Marvin Scholz:
> >> ---
> >> libavutil/avassert.h | 12 ++++++++++++
> >> 1 file changed, 12 insertions(+)
> >>
> >> diff --git a/libavutil/avassert.h b/libavutil/avassert.h
> >> index 1895fb7551..cdab912fe4 100644
> >> --- a/libavutil/avassert.h
> >> +++ b/libavutil/avassert.h
> >> @@ -75,4 +75,16 @@
> >> */
> >> void av_assert0_fpu(void);
> >>
> >> +/**
> >> + * Assert this can not be reached
> >> + */
> >> +#if AV_HAS_BUILTIN(__builtin_unreachable)
> >> +#define av_assert_unreachable() do { \
> >> + av_assert2(0); \
> >> + __builtin_unreachable(); \
> >> +} while (0)
> >> +#else
> >> +#define av_assert_unreachable() av_assert2(0)
> >> +#endif
> >> +
> >> #endif /* AVUTIL_AVASSERT_H */
> >>
> >> base-commit: 85706f5136cf7c88f95843b2634dd3f7d7d2cb6d
> >
> > You are not the first one with this idea:
> > https://ffmpeg.org/pipermail/ffmpeg-devel/2024-May/328116.html
> > But Michael Niedermayer thinks that adding a new macro instead of
> > directly reusing av_assert is more complicated.
> >
> Oh I did not notice that one, thanks…
>
> I definitely think an av_assert_unreachable() is clearer than
> av_assert0(!"reached") too, obviously, else I would not propose it.
>
> (Somewhat proven by these two cases fixed by the patch where we use
> av_assert1/2(0) variants which then result in the compiler not knowing
> these are unreachable cases when the assert is not enabled.)
>
> If this approach is rejected, I can submit a version that uses
> av_assert0(!"reached“).I think you look at this from the wrong side We have 3 levels of assert() and we have one threshold to decide how much we want to check at runtime what we do NOT have is a threshold at what we want the compiler to assume teh statment is true And here this av_assert1(0) is not assumed true and not checked at runtime so the compiler thinks this is reachable I think the solution is to add this 2nd threshold so we can gloablly use av_assert*() for optimization This should remove the warning with no changes to the code thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB The greatest way to live with honor in this world is to be what we pretend to be. -- Socrates
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