[FFmpeg-devel] [PATCH] Fix potential av_find_opt() crash if context is NULL

Michael Niedermayer michaelni
Sun Nov 9 13:36:39 CET 2008

On Sun, Nov 09, 2008 at 12:48:37PM +0100, Stefano Sabatini wrote:
> On date Thursday 2008-10-30 23:07:29 +0100, Michael Niedermayer encoded:
> > On Thu, Oct 30, 2008 at 09:05:32PM +0100, Stefano Sabatini wrote:
> [...]
> > > OK, but then we should check for its nullness every time we access to
> > > it in cmdline.c, since that's generic code and from there we can't
> > > know if sws_opts has been initialized or not, same consideration for
> > > avformat_opts and avcodec_opts.
> > > 
> > > *Or*, we can change the semantics of av_find_opt() (micro bump) to
> > > make it accept a NULL, for which solution I have a slight preference.
> > 
> > i disagree, its all fine as it is, NULL is not allowed and that should be
> > clear from the docs,
> > the avfilter patch is broken its the onle thing that need fixing.
> I'll try to explain myself better...
> av*_opts and swscale_opts are declared and defined (as NULL) in
> cmdutils.c, applications linking to it have to define them to
> something different from NULL or they will crash when calling
> opt_default().
> Patching libavfilter-soc would mean in this case something like the
> following in cmdutils.c:
>     if(!o)
>         o = av_set_string2(sws_opts, opt, arg, 1);
> #endif
> which I think it's just plain wrong, since cmdutils.o should be
> application agnostic, and there is no reason for which we shouldn't
> look in sws_opts simply because CONFIG_AVFILTER is set.

there is NO sws_opts when avfilter is in use! The variable does NOT exist
Thats simply because the corresponding command line option does NOT exist
when avfilter is enabled.


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Democracy is the form of government in which you can choose your dictator
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