bug#47120: 28.0.50; [feature/native-comp] Stale *.eln files are not recompiled

[Andrea Corallo via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

> If you have some *.eln files in your ~/.emacs.d/eln-cache/ directory,
> and the update from Git causes some of the corresponding *.el files to
> be updated, then the *.elc files are rebuilt, but the *.eln files are
> not.  Which then leaves you with stale *.eln files in the cache.
>
> Can the FOO.eln file be re-generated if the corresponding FOO.elc file
> is being generated?

FOO.eln should be regenerated when FOO.elc is regenerated using make
*if* FOO.el is part of the files that are native compiled during the
build process (all files when using NATIVE_FULL_AOT).

If this is not what's going on we have a bug.

> And I wonder what happens when we load the corresponding library: will
> the .eln file be preferred even if it's outdated, or will we load the
> .elc file in this situation?

The .elc will be loaded and deferred compilation will spawn an async
native compilation + will do the hot definition swap.

Thanks

  Andrea