[FFmpeg-trac] #7997(avcodec:closed): undefined-behavior at libavcodec/proresenc_anatoliy.c
FFmpeg
trac at avcodec.org
Thu Jan 9 16:47:55 EET 2020
#7997: undefined-behavior at libavcodec/proresenc_anatoliy.c
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Reporter: Suhwan | Owner:
Type: defect | Status: closed
Priority: normal | Component: avcodec
Version: git-master | Resolution: fixed
Keywords: ubsan | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Changes (by mkver):
* component: undetermined => avcodec
Comment:
Replying to [comment:3 Balling]:
> Fixed in 198081efb7c7343349f0a7acc836f001c511e990
>
> You know, you cannot right shift negative values as well?
That's not true: Right shifting negative values (by a nonnegative value
that is less than the width of the (promoted) left operand) is
implementation-defined and FFmpeg requires this to use sign-extension (see
[https://ffmpeg.org/developer.html#C-language-features here]). That's also
why UBSan doesn't complain about the right shift.
In contrast, left shifting of negative values is undefined.
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Ticket URL: <https://trac.ffmpeg.org/ticket/7997#comment:4>
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