https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89093
--- Comment #75 from Jakub Jelinek <jakub at gcc dot gnu.org> --- It failed for me as well. And a GCC version check won't really help when using earlier GCC 9 snapshot as system compiler (though, admittedly that isn't supported). Another option would be to define the attribute only #ifdef IN_RTS, because when it is #ifdef IN_GCC_FRONTEND, it is compiled with -fno-exceptions and so won't be really invoked.
