[FFmpeg-devel] [PATCH] avutil/pixdesc: add av_warn_unused_result to av_pix_fmt_get_chroma_sub_sample

[Michael Niedermayer]

On Wed, Oct 28, 2015 at 11:03:33PM -0400, Ganesh Ajjanagadde wrote:
> On Fri, Oct 16, 2015 at 5:17 PM, Ganesh Ajjanagadde <gajjanag at mit.edu> wrote:
> > On Fri, Oct 16, 2015 at 11:39 AM, Michael Niedermayer
> > <michael at niedermayer.cc> wrote:
> >> On Thu, Oct 15, 2015 at 07:20:30PM -0400, Ganesh Ajjanagadde wrote:
> >>> This will trigger a bunch of warnings (rightfully so). This API has been
> >>> abused, see the Doxygen comment above for what to do if the error code
> >>> is not meant to be checked.
> >>>
> >>> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
> >>> ---
> >>>  libavutil/pixdesc.h | 1 +
> >>>  1 file changed, 1 insertion(+)
> >>>
> >>> diff --git a/libavutil/pixdesc.h b/libavutil/pixdesc.h
> >>> index a6056fe..975fbf2 100644
> >>> --- a/libavutil/pixdesc.h
> >>> +++ b/libavutil/pixdesc.h
> >>> @@ -297,6 +297,7 @@ enum AVPixelFormat av_pix_fmt_desc_get_id(const AVPixFmtDescriptor *desc);
> >>>   *
> >>>   * @return 0 on success, AVERROR(ENOSYS) on invalid or unknown pixel format
> >>>   */
> >>> +av_warn_unused_result
> >>>  int av_pix_fmt_get_chroma_sub_sample(enum AVPixelFormat pix_fmt,
> >>>                                       int *h_shift, int *v_shift);
> >>
> >> if the caller knows the pixel format is valid (and non hw accel) then
> >> there is no need to check the return code
> >> in many cases this is true, like a decoder that set the pix_fmt itself
> >> it can be sure all possible values are valid
> >
> > See the Doxygen right above (this is why I pointed to it in the commit
> > message) - you are right, but for such "guaranteed safety" usage there
> > is a different API in avcodec. It seems to have been created precisely
> > for this purpose.
> 
> ping; you don't find the above reasoning satisfying?

avcodec_get_chroma_sub_sample() is part of libavcodec,
av_pix_fmt_get_chroma_sub_sample is part of libavutil

any code not depending on libavcodec cannot use
avcodec_get_chroma_sub_sample(), an example might be filters in
libavfilter which dont otherwise depend on libavcodec

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Freedom in capitalist society always remains about the same as it was in
ancient Greek republics: Freedom for slave owners. -- Vladimir Lenin
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