Re: Timestamps in ...-autoloads.el files

[Alex Kost]

I've just noticed that our generated "…-autoloads.el" files still have
unwished timestamps (SOURCE_DATE_EPOCH is not honored).

To recap: we use "gnu/packages/patches/emacs-source-date-epoch.patch" to
modify 'autoload-insert-section-header' function, and it should work,
but it doesn't.  IIUC this happens because "autoload.elc" file was
compiled using the unpatched "autoload.el", but first things first.  Try
the following recipe in Emacs (installed with Guix):

1. M-: (setenv "SOURCE_DATE_EPOCH" "1")

2. Generate autoloads for any file with autoload cookies.  If you don't
   have such a file at hand, make "/tmp/f1.el" file with this single
   line:

   ;;;###autoload(defun f1 nil)

   Then: "M-x update-file-autoloads </tmp/f1.el> </tmp/auto1.el>"

Now open "/tmp/auto1.el" and you'll see a "bad" timestamp like this one:
(22323 17532 313464 85000).

But!  If you reevaluate 'autoload-insert-section-header' and try again
the timestamp will be "good":

3. M-x find-function autoload-insert-section-header

4. Reevaluate it: C-M-x

5. M-x update-file-autoloads </tmp/f1.el> </tmp/auto2.el>

Now look at "/tmp/auto2.el": it contains (0 1 0 0) timestamp as
expected.

I looked at the compiled "autoload.elc" file and if I understood it
correctly, it was compiled using the unpatched version of "autoload.el"
(because there is no mention of SOURCE_DATE_EPOCH there).  But I don't
understand how it could happen since patching is performed before
building.  Any ideas?

-- 
Alex