[Bug c++/64332] gcc/g++ handles system_header differently

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64332

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I don't think it is system header which is being handled differently, rather I
think it is warning for attribute is being handled differently.