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

[Eli Zaretskii]

> From: Andrea Corallo <akrl@sdf.org>
> Cc: 47120@debbugs.gnu.org
> Date: Sat, 13 Mar 2021 19:43:55 +0000
> 
> > 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.

I'm talking about the *.el files that are not automatically natively
compiled, they are natively compiled when first time loaded into
Emacs.

> > 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 the .eln file be preferred even if it's outdated, or will we load the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.

That's OK.  But I think it would be better to recompile the .eln file
when .el is updated and we are byte-compiling to produce an updated
.elc file.

Thanks.