https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86440
--- Comment #4 from Yohei Kojima <y.koj.eel at gmail dot com> ---
Also, -Wignored-qualifiers messages disappeared with g++ compiling b.c.
Probably it is a bug caused by the same reason as this bug.
$ g++ -c -Wall -Wextra -Wignored-qualifiers b.c
b.c: In function 'void g(void* const (*)())':
b.c:4:22: warning: unused parameter 'h' [-Wunused-parameter]
4 | void g(void *const (*h)(void)) {
| ~~~~~~~~~~~~~~^~~~~~~~
