[FFmpeg-devel] [PATCH 16/16] avfilter/vsrc_testsrc: Deduplicate options

[Anton Khirnov]

Quoting James Almer (2021-01-04 20:35:30)
> On 1/4/2021 4:29 PM, Nicolas George wrote:
> > Andreas Rheinhardt (12021-01-04):
> >> What enumerating code? It is actually commonplace that options are
> >> shared (you can find examples in libavfilter by using 'git grep -e
> >> define --and -e options'); pointing into other options and thereby
> >> reusing only a part of other options is not common, but I don't really
> >> see why it shouldn't work.
> > 
> > Using #define to de-duplicate the source is fine, of course.
> > 
> > But IIRC pointing to the same array, i.e. de-duplicating in the binary,
> > will lead to the code that enumerate options to loop in some way. I do
> > not remember the details, and I cannot find a commit that talks about
> > it, sorry. Maybe somebody here remembers better?
> > 
> > Regards,
> 
> I recall issues with modules sharing a common AVClass, but different 
> AVClasses sharing a common array of AVOptions seems to be ok.
> See rawdec.h in libavformat, and how ff_raw_options is used in several 
> different demuxer AVClasses.

child_class_next() implementation for AVFormatContext and others assumes
a one-to-one mapping between objects and their AVClasses. But that is
now deprecated and there should be no issues when it's removed.

-- 
Anton Khirnov