https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106486
--- Comment #6 from H. Peter Anvin <hpa at zytor dot com> --- Ping on this? It seems it ought to be a trivial thing to do? The solution in Comment 3 is definitely the right one; -Wno-missing-prototypes should be a warning (and ignored) or even an error, but -Wmissing-prototypes just silently ignored as redundant. Although a lot of Makefiles have CXXFLAGS, it is common enough to have WARNFLAGS or similar to make it easier to customize warnings. If warnings are probed by autoconf, a lot of configure scripts get it actively wrong. This includes GNU projects, or at least used to (they might have been fixed since, I don't know.) -Wno-unknown-warning-option (Comment 2) is another possibility (not mutually exclusive, either.) One can argue back and forth if "unknown" is really the right thing here as opposed to something like -Wno-invalid-warning-option, but it is *definitely* bizarre to have a completely unknown warning symbol be ignored, but then have a new version of gcc suddenly start spewing warnings over it.
