[FFmpeg-devel] Request for --disable-deprecated configure option

[Kacper Michajlow]

Hello,

It would be nice to have configure time ability to disable all
`FF_API_*` for testing purposes.

As we know not all code can be marked to emit Wdeprecated.
Specifically #defines doesn't emit any warning and it's easy to miss
such depreciation before it's actually removed.

The breakage of course is not big, but the main issue is that the
current release version of a ffmpeg user won't be compatible with
ffmpeg after API bump, without any period for transition.

--disable-deprecated could be used for testing and ensuring that
(next) API bump goes smoothly. For both ffmpeg and its users.

We have seen breakage in mpv and libplacebo (only when built as
vf_libpalcebo) recently, which would be prevented if we had better
tools to monitor this. For example mpv builds with ffmpeg master on CI
with Werror and Wdeprecated enabled and yet it's not enough.

Thanks,
Kacper