[FFmpeg-devel] [RFC] Error code fixes before the Big Bump

[Stefano Sabatini]

Hi,

there are some problems related to error codes which I would like to
fix. They can be fixed only with a coordinated big bump of all the
libav* libraries, so this can be considered a good moment to do this.

The mentioned problems are:

* implement AVERROR_EOF as a libav* specific error code, rather than
  mask the EPIPE POSIX error code which has a different semantics

* implement AVERROR_INVALIDDATA as a libav* specific error code (already
  implemented but it was controversial), and fix the
  AVERROR(EINVAL)/AVERROR_INVALIDDATA conflict

* drop AVERROR_NUMEXPECTED (not very important, but I believe it is a
  too much specific error code, so I'd prefer to replace it with
  AVERROR(EINVAL)

I thought about Michael objection in
http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/105883/focus=107317:

|bumping it to 51 will changes the codes returned by all libs using libavutil
|all of them would need to bump major.
|i dont think this is reasonable, thus we should undo all error redefinitions
|before they become real and debian burns you at the stake

but I don't think this is a real issue (assuming that all the libav*
major versions are bumped at the same time), and this is my argument:

an external library public function should not return an error code
from a libav* library (and thus change behavior if the return code of
libav* changes), but should rather map the libav* error code to a
library-specific error code.

For example we don't have functions which return libfreetype error
codes, but we map them to the corresponding libav* error codes.

Relevant threads:

* AVERROR_EOF replacement first discussion:
http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/105883

* Big bump error codes related discussion:
http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/125963/focus=126000

Comments are welcome.