https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81513
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- The C++11 attribute syntax isn't supported in C++03 mode, but the noreturn attribute is supported using the GNU attribute syntax (and has been for years) so it's right for that to be non-zero. I'm not sure why maybe_unused is non-zero but doesn't work. __attribute__((unused)) works, but __attribute__((maybe_unused)) doesn't.
