https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118283
--- Comment #2 from Sam James <sjames at gcc dot gnu.org> --- (In reply to Brecht Sanders from comment #0) We hit a bunch of issues like this during the 14 cycle when we started to enforce C99 properly and fixed issues like this while we were there. Recent versions of autoconf should be okay, but custom checks may need fixing. For builtin checks, autoreconf should fix it.
