[FFmpeg-devel] [PATCH]Avoid non-strict pointer aliasing in kega decoder

[Reimar Döffinger]

Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:

>Reimar Döffinger <Reimar.Doeffinger <at> gmx.de> writes:
>
>> >>> Attached patch fixes the fate failure for icc 13.1 
>> > 
>> >> Apart from that, when I suggested memcpy I meant replacing 
>> >> the whole for loop by a single memcpy, no need to
>> >> copy the pixels one by one.
>> > 
>> > That failed for me with gcc, could you suggest how to do it 
>> > correctly?
>> 
>> What do you mean by 'failed' and what did you try?
>
>With my current patch, the for loop looks like this:
>    for (i = inp_off; i < count + inp_off; i++) {
>        memcpy(&out[2 * outcnt++], &inp[2 * i], 2);
>    }
>
>When I change that to memcpy:
>    memcpy(&out[2 * outcnt], &inp[2 * inp_off], 2 * count);
>    outcnt += count;
>
>I see ugly artefacts.

Maybe inp and out can overlap? Try memmove.
Though that might not be enough, something like our copy_backptr function might be needed.
Probably needs a closer look at the code.