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

[jakub at gcc dot gnu.org]

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

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Different warnings are simply done at different compilation phases.  This is
similar to how you get only a subset of FE warnings on uninstantiated
templates, only something can be warned reliably at that phase, and something
is just too hard to warn at that phase.  So, lots of warnings you get only when
actually instantiating the templates.