[FFmpeg-devel] [PATCH 4/6] avcodec/jrevdct: Fix UB left shifts of negative numbers

[Andreas Rheinhardt]

Michael Niedermayer:
> On Wed, Sep 28, 2022 at 08:58:16PM +0200, Andreas Rheinhardt wrote:
>> Affected the rv20-1239 FATE test.
>>
>> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
>> ---
>>  libavcodec/jrevdct.c | 38 +++++++++++++++++++-------------------
>>  1 file changed, 19 insertions(+), 19 deletions(-)
> 
> iam a bit surprised this was not spotted long ago but LGTM
> 
> thx
> 

Most of these changes are in ff_j_rev_dct4 which is only used if lowres
== 1; I guess the fuzzer doesn't use lowres which explains why this has
not been found before.

- Andreas