Re: Sharing native-lisp system load-path between builds

[Eli Zaretskii <eliz@gnu.org>]

> From: Björn Bidar <bjorn.bidar@thaodan.de>
> Date: Mon, 26 Jun 2023 03:14:17 +0300
> 
> I'm building Emacs master for OpenSUSE to provide testing.
> OpenSUSE packaging packages Emacs so that they have three builds with
> different feature sets: X11 without GTK, GTK and one build just without
> X11 or GTK.
> 
> This helps different users to chose their preferred builds and keeps
> build workers small for Emacs packages build.
> 
> The packages share the elisp, native-lisp ahead of time compilations and
> docs.
> 
> Recently the native-lisp load path changed to change per Emacs
> executable.

It isn't a recent change, at least not in principle.

> I don't know the exact commit when this changed but it was
> between ref 3c8167ec0f9647e6fc33e65b0a0324f96cb795ee and
> d46a2fa319808963bbe8d3a90e7dbb13fcd844f5.
> 
> Now my questions: Is this a bug or can a different hash be used to
> determine the system load-path? It is very useful to precompile the
> lisp code once per emacs builds that share the same code.

It's impossible to share native-compiled *.eln files between different
builds, because they depend on the primitives compiled into the build
and on the architecture of the host CPU.

So you must have a separate directory for each build configuration,
and any significant change in the Emacs C code will require
recompilation of all the *.eln files.