https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80516
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #3)
> The warning has changed slightly since GCC 9:
>
> 80516.cc:6:3: warning: ‘signed’ specified with ‘u’ {aka ‘unsigned int’}
> [-Wpedantic]
> 6 | S<signed u> s;
> | ^~~~~~
That was because of PR 84701.
