https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81327
--- Comment #12 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Every GCC release comes with a http://gcc.gnu.org/gcc-7/porting_to.html (similarly for other releases and we'll have one for gcc-8 too), and especially with -Werror people need to adjust their codes not just for stuff that is newly flagged as errors, but also for the warnings. If we were required not to issue any new warnings on some set of packages, we could probably never introduce new warnings at all.
