On Sun, Nov 20, 2016 at 08:56:15AM -0500, Ronald S. Bultje wrote: > Hi, > > On Sun, Nov 20, 2016 at 6:57 AM, Michael Niedermayer <mich...@niedermayer.cc > > wrote: > > > @@ -131,6 +132,20 @@ static int write_number(void *obj, const AVOption *o, > > void *dst, double num, int > > if (intnum == 1 && d == (double)INT64_MAX) *(int64_t *)dst = > > INT64_MAX; > > else *(int64_t *)dst = > > llrint(d) * intnum; > > break;} > > + case AV_OPT_TYPE_UINT64:{ > > + double d = num / den; > > + // We must special case uint64_t here as llrint() does not > > support values > > + // outside the int64_t range and there is no portable function > > which does > > + // "INT64_MAX + 1ULL" is used as it is representable exactly as > > IEEE double > > + // while INT64_MAX is not > > + if (intnum == 1 && d == (double)UINT64_MAX) { > > + *(int64_t *)dst = UINT64_MAX; > > + } else if (o->max > INT64_MAX + 1ULL && d > INT64_MAX + 1ULL) { > > + *(uint64_t *)dst = (llrint(d - (INT64_MAX + 1ULL)) + > > (INT64_MAX + 1ULL))*intnum; > > + } else { > > + *(int64_t *)dst = llrint(d) * intnum; > > + } > > + break;} > > case AV_OPT_TYPE_FLOAT: > > *(float *)dst = num * intnum / den; > > break; > > > For the stupid, like me: what does this do? More specifically, this seems > an integer codepath, but there is a double in there. Why?
write_number() has a num/den double argument. If this is used to set a uint64_t to UINT64_MAX things fail as double cannot exactly represent UINT64_MAX. (the closest it can represent is "UINT64_MAX + 1" So it needs to be handled as a special case. Otherwise it turns into 0 [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB No human being will ever know the Truth, for even if they happen to say it by chance, they would not even known they had done so. -- Xenophanes
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