https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94753
Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |ASSIGNED Assignee|unassigned at gcc dot gnu.org |pinskia at gcc dot gnu.org --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- I am going to fix this for GCC 15. The check for -undef is done way to early it seems in c_cpp_builtins . Basically the code to define the feature macros need to be moved to before that check. The reason why __cplusplus works is because that is done via libcpp rather than from the front-end.