[FFmpeg-devel] [PATCH] Enhance ffmpeg.c:opt_default()

Michael Niedermayer michaelni
Sun Nov 30 23:27:50 CET 2008

On Sun, Nov 30, 2008 at 10:27:01PM +0100, Stefano Sabatini wrote:
> On date Sunday 2008-11-30 21:02:43 +0100, Michael Niedermayer encoded:
> > On Sun, Nov 30, 2008 at 08:22:35PM +0100, Stefano Sabatini wrote:
> [...]
> > > The current semantics of av_set_string2() is to return NULL if the
> > > option hasn't been found *or* if the value wasn't valid, so there is
> > > currently no way to distinguish the two cases (which is the reason of
> > > the patchset).
> > > 
> > > I think that if the function *finds* the option but can't set the
> > > value because the value isn't valid, it is still a good idea to return
> > > the option found, at least it seems better because this way we're
> > > providing more information to the invoker.
> > 
> > the problem iam having with this is when the "user" doesnt care about the
> > error message and thus passes NULL.
> > At that point he cant find out if the call succeeded
> He can always do:
> AVOption *o = av_set_string3(..., error, error_size);
> if (o && !error)
>    ...
> (yes this way he's forced to pass a non-NULL error...).
> On the other hand if he wants to know for whatever reason if the
> option was found and doesn't care to know if the value has been set or
> not he can do it in just one step.
> But I won't insist on this if you prefer the other way.

what about just returning an index into the
AVOption array and a negative value to indicate exactly which error happened?
(thats just an idea, i dont know how this would look in code so maybe it
 ends up ugly ...)

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I hate to see young programmers poisoned by the kind of thinking
Ulrich Drepper puts forward since it is simply too narrow -- Roman Shaposhnik
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