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

[Stefano Sabatini]

On date Sunday 2008-05-18 15:39:06 +0200, Michael Niedermayer encoded:
> On Sun, May 18, 2008 at 01:44:36AM +0200, Stefano Sabatini wrote:
> > On date Saturday 2008-05-17 19:57:43 +0200, Michael Niedermayer encoded:
[...]
> > > an optional 
> > > av_log(context, AV_LOG_ERROR, error, param, arg, opt.min, opt.max);
> > 
> > In this way you have to know how is made the returned string, boring
> > since you have to document it and not very flexible for example if you
> > want to change the wording of the message thus the ordering of the
> > parameters you break it, furthermore if you want to support more than
> > one message (for example: "The value for '%s' was '%f' which isn't an
> > integer", only two params) it can't work anymore.
> 
> Go read ISO C and POSIX, i could explain how printf() works but ffmpeg-dev
> really isnt the correct place for this, the docs are clear and
> understandable.
[...] 
> > > vs.
> > > 
> > > an optional 
> > > av_log(context, AV_LOG_ERROR, error);
> > > and a mandatory
> > > av_free(error);
> > > 
> > > Honestly i dont see how the first is worse, and of course if someone has a
> > > better idea than these 2 thats welcome as well.
> > 
> > Patches attached corresponding to the second approach, the first one
> > maybe should go in a separate thread.
> 
> patches rejected, we will not malloc error messages, the memleaks alone
> are reason enough why not.

At this point I'm defeated, I can't see any other ways to resolve the
problem but:

1) use av_log to show the error occurred

2) allocate a string containing the error in av_set_strin2() and
mandate the user to free it

If someone can find a solution corresponding to:

3) use a static parametric string containing enough parameter to show
the various possible error messages:
Value '%s' for parameter '%s' out of range
Value '%s' for parameter '%s' is not within %f - %f\n"
Value '%s' for parameter '%s' unparsable: %s\n"
... possibly others to be added in the future

and a method to correctly fill them outside of av_set_string2() (where
for example the parsing error messages isn't accessible anymore) 

I'd be very curious to see it.

Regards.
-- 
FFmpeg = Foolish & Fantastic Multimedia Portable EntanGlement