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

[Kacper Michajlow <kasper93@gmail.com>]

On Thu, 3 Apr 2025 at 11:39, Martin Storsjö <martin@martin.st> wrote:
>
> On Thu, 3 Apr 2025, Kacper Michajlow wrote:
>
> > 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.
>
> So essentially to configure a build to use the next major API version
> before doing the actual bump?
>
> I've actually mentioned that we should do that (and that we should have a
> FATE instance that continuously tests this, so that we know beforehand
> that our planned next form of the APIs actually works), and I did try
> making a PoC of it at some point, but unfortunately, I think I concluded
> that it was a bit more messy than I had wanted, so I didn't continue
> on it.
>
> See https://github.com/mstorsjo/ffmpeg/commit/next-abi for my PoC.

Yes, making the API version configurable would work. But as you
noticed it gets a bit messy with all the conditionals.

I didn't think about it long, I wanted to discuss this first, but was
thinking about a simple DISABLE_DEPRECATED which would be defined by
configure and all `FF_API_*` would depend on that.

#define DISABLE_DEPRECATED 0
#define FOO(c) (c) && !DISABLE_DEPRECATED

#define LIBAVUTIL_VERSION_MAJOR  60
#define FF_API_MOD_UINTP2               FOO(LIBAVUTIL_VERSION_MAJOR < 61)
#define FF_API_RISCV_FD_ZBA             FOO(LIBAVUTIL_VERSION_MAJOR < 61)
...

Also if someone wants to go fancy, the deprecated feature could be
disabled individually, but I don't really see much use for that,
except niche cases where you might still use deprecated things, but
not all... but then just don't disable them.

- Kacper
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