Re: How to make aot native-compilation and pdmp creation reproduceable

[Gerd Möllmann]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Gerd Möllmann <gerd.moellmann@gmail.com>
>> Cc: bjorn.bidar@thaodan.de,  emacs-devel@gnu.org
>> Date: Mon, 09 Oct 2023 13:26:03 +0200
>> 
>> Eli Zaretskii <eliz@gnu.org> writes:
>> 
>> >> Offset 17 is the stat of the dump fingerprint (the first 16 bytes are a
>> >> magic number).
>> >> 
>> >> struct dump_header
>> >> {
>> >>   /* File type magic.  */
>> >>   char magic[sizeof (dump_magic)];
>> >> 
>> >>   /* Associated Emacs binary.  */
>> >>   unsigned char fingerprint[sizeof fingerprint];
>> >
>> > The fingerprint is supposed to remain unchanged if you rebuild the
>> > same code base.
>> 
>> Right, that's the problem -- apparently it isn't unchanged in this case
>> as the diff of the executables' objdump shows.
>> 
>> My hypothesis is that x-win.eln changes between builds (print-circle
>> etc.) => make-fingerprint computes a different ingerprint and so on.
>
> If x-win.el didn't change, x-win.eln will not be regenerated, so
> something else is at work here.

But x-win.elc _did_ change.  To cite one of Björn's mails

> Strangely the only eln file that changes is x-win.el:
> /usr/lib64/emacs/29.1/native-lisp/29.1-115521d4/preloaded/x-win-3c49581f-6ddb7e08.eln
>  differs in ELF sections
> --- old 
> /usr/lib64/emacs/29.1/native-lisp/29.1-115521d4/preloaded/x-win-3c49581f-6ddb7e08.eln
>  (objdump)
> +++ new 
> /usr/lib64/emacs/29.1/native-lisp/29.1-115521d4/preloaded/x-win-3c49581f-6ddb7e08.eln
>  (objdump)
> @@ -2950,7 +2950,7 @@
>   0e7c0 6f726564 20736573 73696f6e 20646174  ored session dat
>   0e7d0 61222022 4865776c 6574742d 5061636b  a" "Hewlett-Pack
>   0e7e0 61726420 496e636f 72706f72 61746564  ard Incorporated
> - 0e7f0 22202334 3d282831 3638202e 206d7574  " #4=((168 . mut
> + 0e7f0 22202336 3d282831 3638202e 206d7574  " #6=((168 . mut
>   0e800 652d6163 75746529 20283136 39202e20  e-acute) (169 . 
>   0e810 6d757465 2d677261 76652920 28313730  mute-grave) (170
>   0e820 202e206d 7574652d 61736369 69636972   . mute-asciicir
> @@ -2976,7 +2976,7 @@
>   0e960 20224865 776c6574 742d5061 636b6172   "Hewlett-Packar
>   0e970 6420436f 6d70616e 79222022 5831312f  d Company" "X11/
>   0e980 4e655753 202d2053 756e204d 6963726f  NeWS - Sun Micro
> - 0e990 73797374 656d7320 496e632e 22202336  systems Inc." #6
> + 0e990 73797374 656d7320 496e632e 22202334  systems Inc." #4
>   0e9a0 3d282833 39323937 36202e20 66333629  =((392976 . f36)
>   0e9b0 20283339 32393737 202e2066 33372920   (392977 . f37) 
>   0e9c0 28333933 30353620 2e207265 71292028  (393056 . req) (