m4 has contains an outdated vendor copy of gnulib that does not yet know
about hurd-amd64. The underlying bug and patch on the gnulib side is
https://bugs.gnu.org/63334 and has since been fixed there. Also the
Debian gnulib package version 20250303-1 contains the fix. What does not
contain the fix is m4's copy. Could you please update it (after trixie
is released)?

Thanks to Samuel for having done all the actual work.

Helmut

No need to update the current package when they have already released
m4-1.4.20, which I will upload for unstable after the release of trixie
(not a big fan of experimental). I have a prototype here:

https://salsa.debian.org/sanvila/m4-next

Thanks.

We believe that the bug you reported is fixed in the latest version of
m4, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1109129@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Santiago Vila <sanvila@debian.org> (supplier of updated m4 package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Mon, 01 Sep 2025 20:30:00 +0200
Source: m4
Architecture: source
Version: 1.4.20-1
Distribution: unstable
Urgency: medium
Maintainer: Santiago Vila <sanvila@debian.org>
Changed-By: Santiago Vila <sanvila@debian.org>
Closes: 1109129
Changes:
 m4 (1.4.20-1) unstable; urgency=medium
 .
   * New upstream release.
   * Should fix FTBFS problem on hurd-amd64. Closes: #1109129.
   * Drop -std=c17 from CFLAGS, should not be needed anymore.
   * Switch debian/watch to version 5.
   * Reenable all tests again.
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