Thilo Borgmann: > Am 16.06.22 um 12:13 schrieb Andreas Rheinhardt: >> Thilo Borgmann: >>> diff --git a/libavcodec/dovi_rpu.c b/libavcodec/dovi_rpu.c >>> index a87562c8a3..833ce9e705 100644 >>> --- a/libavcodec/dovi_rpu.c >>> +++ b/libavcodec/dovi_rpu.c >>> @@ -153,7 +153,7 @@ static inline uint64_t get_ue_coef(GetBitContext >>> *gb, const AVDOVIRpuDataHeader >>> case RPU_COEFF_FIXED: >>> ipart = get_ue_golomb_long(gb); >>> fpart.u32 = get_bits_long(gb, hdr->coef_log2_denom); >>> - return (ipart << hdr->coef_log2_denom) + fpart.u32; >>> + return ipart * (1 << hdr->coef_log2_denom) + fpart.u32; >>> case RPU_COEFF_FLOAT: >>> fpart.u32 = get_bits_long(gb, 32); >>> @@ -172,7 +172,7 @@ static inline int64_t get_se_coef(GetBitContext >>> *gb, const AVDOVIRpuDataHeader * >>> case RPU_COEFF_FIXED: >>> ipart = get_se_golomb_long(gb); >>> fpart.u32 = get_bits_long(gb, hdr->coef_log2_denom); >>> - return (ipart << hdr->coef_log2_denom) + fpart.u32; >>> + return ipart * (1 << hdr->coef_log2_denom) + fpart.u32; >>> case RPU_COEFF_FLOAT: >>> fpart.u32 = get_bits_long(gb, 32); >> >> coef_log2_denom can be in the range 13..32. This means that 1 << >> hdr->coef_log2_denom can be UB (namely if coef_log2_denom is 31 or 32 >> for ordinary 32 bit ints); this time it is not UB that happens to work >> as expected, because 1 << 32 will be 0 or 1 (depending upon the system) >> and not 2^32. In case of get_ue_coef() this actually adds UB to >> otherwise fine code. > > So 1LL it needs to be, not? Am I still missing something? >
This version should not add new UB. I btw don't get why you are changing get_ue_coef() at all: It's fine as-is; consistency should only trump when the choice is between several equally good alternatives which is IMO not true here. (The reason that C makes left shifts of negative values UB is because of non-two's complement systems, so it is unfortunate for a project like FFmpeg that requires two's complement that it has to workaround this restriction by using a * (1 << b).) - Andreas _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
