On Friday, 21 October 2022 21:14:54 CEST Marek Polacek via Gcc wrote:
> commit 0a91bdaf177409a2a5e7895bce4f0e7091b4b3ca
> Author: Joseph Myers <joseph@codesourcery.com>
> Date:   Wed Sep 7 13:56:25 2022 +0000
> 
>     c: New C2x keywords
> 
> which says:
> 
>     As with the removal of unprototyped functions, this change has a
> high risk of breaking some old code and people doing GNU/Linux
> distribution builds may wish to see how much is broken in a build
> with a -std=gnu2x default.

It already does break a lot.  See https://bugs.gentoo.org/870412 
(comments go over the details).  I was intending on giving this issue a 
proper look in the GNU toolchain frame of reference, but never got 
around to it (and I kinda knocked priority down after managing to 
configure properly once IIRC).

-- 
Arsen Arsenović