https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125714
--- Comment #2 from Drea Pinski <pinskia at gcc dot gnu.org> --- The documentation just says: Because a pure function cannot have any observable side effects it does not make sense for such a function to return void. Declaring such a function is diagnosed. But it does not say it has to mean anything and not ignored ....
