[FFmpeg-devel] [PATCH] avcodec/snowenc: fix discarded const warning

Ganesh Ajjanagadde gajjanag at mit.edu
Sun Sep 20 21:19:40 CEST 2015

On Sun, Sep 20, 2015 at 2:14 PM, Nicolas George <george at nsup.org> wrote:
> Le jour du Labour, an CCXXIII, Ganesh Ajjanagadde a écrit :
>> This fixes a -Wdiscarded-qualifiers in e.g
>> http://fate.ffmpeg.org/log.cgi?time=20150919093218&log=compile&slot=x86_64-archlinux-gcc-ddebug.
>> It is quite clear from the code that the discard of constness was deliberate,
>> so the cast should be fine.
> It may have been deliberate, but is it right? Unless I am missing somewhere
> like last time, the codec is modifying a memory location that could be
> read-only, according to the const flag on the function parameter. It will
> probably never happen because of how we manage AVFrame allocation, but it is
> not satisfactory.
> If codecs are authorized to modify basic properties of the input frame, then
> const should be removed on the declaration of the encode_frame() method. If
> not, then snowenc should be changed to avoid doing it; that last solution
> seems not very complicated at a quick glance, just use a separate variable
> for quality.

Perhaps I am being pessimistic, but there is also pic->pict_type in
addition to pic->quality. I think it is best to wait to see if Michael
has anything to say on this topic; snow is his brainchild after all.

> Regards,
> --
>   Nicolas George
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