Re: curiosity in value of "source-directory" in function "autoload-generated-file" and in the containing file "autoload.el.gz"

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 18 Jun 2017 09:51:37 -0700 (PDT)
> From: Alan <wehmann@fnal.gov>
> Injection-Date: Sun, 18 Jun 2017 16:51:37 +0000
> 
> I find it curious that the file "/Applications/Emacs.app/Contents/Resources/lisp/emacs-lisp/autoload.el.gz" has the following code:
> 
> (defun autoload-generated-file ()
>   (expand-file-name generated-autoload-file
>                     ;; File-local settings of generated-autoload-file should
>                     ;; be interpreted relative to the file's location,
>                     ;; of course.
>                     (if (not (local-variable-p 'generated-autoload-file))
>                         (expand-file-name "lisp" source-directory))))
> 
> and "source-directory" in this code has no other mention in this file, except in a comment.

source-directory is a built-in variable, defined in C.  The above
snippet is needed when building Emacs and when running it uninstalled,
i.e. from its build tree.  I think.