[FFmpeg-devel] [PATCH] [RFC] avcodec/h264_slice: Duplicate addition to avoid ubsan warning

Ganesh Ajjanagadde gajjanag at mit.edu
Wed Dec 9 15:42:51 CET 2015

On Wed, Dec 9, 2015 at 9:32 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Wed, Dec 09, 2015 at 03:17:26PM +0100, Carl Eugen Hoyos wrote:
>> On Wednesday 09 December 2015 02:08:06 am Michael Niedermayer wrote:
>> > From: Michael Niedermayer <michael at niedermayer.cc>
>> >
>> > Fixes mozilla bug 1230247
>> Does this make the code slower and works around a bug in ubsan?
> i would guess it does or could make the code slower
> i do not know for sure if this is a bug in ubsan or actually undefined,
> i was hoping some language lawyer could clarify that

Unfortunately, atm I think you are our best language lawyer :). I can
look into this after a week if it can help.
All I can say right now is: please be careful if using ubsan,
especially the gcc variant
(https://trac.ffmpeg.org/ticket/4727#comment:8, gave this before as

> [...]
> --
> 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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