Bug#872503: ffmpeg: armhf SIGBUS in ff_diff_pixels_armv6 running winff autopkgtest

[James Cowgill]

Hi,

On 19/08/17 10:36, Carl Eugen Hoyos wrote:
> 2017-08-18 19:17 GMT+02:00 Carl Eugen Hoyos <cehoyos at gmail.com>:
>> 2017-08-18 14:08 GMT+02:00 James Cowgill <jcowgill at debian.org>:
>>> Control: tags -1 upstream
>>
>> (Sorry if I misunderstand: Not sure if I am "upstream")

To clarify, the tag doesn't mean that you are upstream. It means that
this bug is an upstream bug, as opposed to something Debian specific.

>>> Hi,
>>>
>>> On 18/08/17 08:25, Carl Eugen Hoyos wrote:
>>>> Hi!
>>>>
>>>> Is this issue still reproducible with current FFmpeg git head?
>>>
>>> I've just tested and yes it is still reproducible with this commit:
>>
>> Thank you!
>>
>> I will try to test next week on an Android device, feel free to open a
>> ticket on trac.ffmpeg.org - I am not sure how active the arm support
>> is though;-(
> 
> I can reproduce a crash on Android with the following command line:
> $ ffmpeg -i test.avi -cmp dct -an out.flv
> 
> Unfortunately, I was unable to get any useful gdb output and cannot
> verify that I see the same crash you reported:
> I managed to get a core dump and copied it to my build system, but
> Android gdb could not get a backtrace there;-(

Unfortunately as I wrote in the original report, the ARM code reuses the
lr register so you can't get a backtrace from where the code gets the
SIGBUS.

> Could you confirm that this is a regression since 31326143 (ie since
> forever) and is not reproducible with f73a626a?

Yes the code fails in the same place with 31326143 and worlds with
f73a626a, although I don't think the ARM code is at fault here since the
misaligned argument is coming from further up the call chain.

> Since I cannot produce the required gdb output, you will have to open
> a ticket, sorry!

OK. I'll see if the arguments are misaligned on x86 as well first.

Thanks,
James

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