https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97876
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> --- Github's poor life choices should not be our problem ;-) If clang-8 doesn't ship <stop_token> and doesn't work with GCC's <stop_token>, I would interpret that as you can't test <stop_token> with clang-8.