[Bug c++/77298] -Wnonnull-compare only emitted for code which is invoked

["msebor at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77298

--- Comment #6 from Martin Sebor <msebor at gcc dot gnu.org> ---
Yes, that makes sense to me as an explanation of the limitation of the GCC
implementation and a solution/workaround for it.   I don't think it's something
users unfamiliar with GCC internals think of, though.  I don't have a sense of
how much work it would be to change GCC to issue these warnings consistently,
whether or not functions are used, but I suspect it's not a trivial "bug fix."

Until this change is made (if it ever is made), it seems that documenting the
limitation and the -fkeep-inline-functions workaround might help users who are
relying on these warnings to be consistent.  If you all agree I volunteer to
reopen thus bug and add something to the manual.  Yes?