On Wed, Oct 28, 2015 at 10:48:14PM -0400, Ganesh Ajjanagadde wrote: > This ensures that no undefined behavior is invoked, while retaining > identical return values in all cases and at no loss of performance > (identical asm on clang and gcc). > Essentially, this patch exchanges undefined behavior with implementation > defined behavior, a strict improvement. > > Rationale: > 1. The ideal solution is to have the return type a uint64_t. This > unfortunately requires an API change. > 2. The only pathological behavior happens if both arguments are > INT64_MIN, to the best of my knowledge. In such a case, the > implementation defined behavior is invoked in the sense that UINT64_MAX > is interpreted as INT64_MIN, which any reasonable implementation will > do. In any case, any usage where both arguments are INT64_MIN is a > fuzzer anyway. > 3. Alternatives of checking, etc require branching and lose performance > for no concrete gain - no client cares about av_gcd's actual value when > both args are INT64_MIN. Even if it did, on sane platforms (e.g all the > ones FFmpeg cares about), it produces a correct gcd, namely INT64_MIN. > > Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com> > --- > libavutil/mathematics.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-)
LGTM [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Let us carefully observe those good qualities wherein our enemies excel us and endeavor to excel them, by avoiding what is faulty, and imitating what is excellent in them. -- Plutarch
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