Re: source-directory, installed Emacs, and C source

[Eli Zaretskii <eliz@gnu.org>]

> From: Manuel Giraud <manuel@ledu-giraud.fr>
> Cc: sbaugh@catern.com,  emacs-devel@gnu.org
> Date: Wed, 25 Oct 2023 10:41:33 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> [...]
> 
> > AFAIR, Emacs looks for Lisp files by scanning load-path.  So if you
> > customize load-path to include the directories in the source tree, you
> > should be able to tell Emacs to look for the Lisp files in another
> > directory.  I think that's what we do when Emacs is run uninstalled,
> > and that's why it finds the Lisp files in the source tree.
> 
> This works… but not always.  Here is a test I've just done:
> 
>      - emacs -Q
>      - then load the following:
> --8<---------------cut here---------------start------------->8---
> (add-to-list 'load-path "~/emacs-repo/lisp/")
> (dolist (dir '("vc" "use-package" "url" "textmodes" "progmodes"
> 	       "play" "org" "nxml" "net" "mh-e" "mail" "leim"
> 	       "language" "international" "image" "gnus" "eshell"
> 	       "erc" "emulation" "emacs-lisp" "cedet" "calendar"
> 	       "calc" "obsolete"))
>   (add-to-list 'load-path (format "~/emacs-repo/lisp/%s/" dir)))
> --8<---------------cut here---------------end--------------->8---

I never said you should just prepend the source tree to the previous
value, did I?

And anyway, are you sure you emulated Spencer's use case closely
enough?  He never described in detail which files are where, but AFAIU
at the very least you should have removed the *.el and *.el.gz files
from the installation directory, since that is what he does (again,
AFAIU).