https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108462
--- Comment #3 from Gaius Mulley <gaius at gcc dot gnu.org> --- ah, oops, of course the testsuite checks in tree :-) So after an install: $ cd gcc/testsuite/gm2/isocoroutines/run/pass $ gm2 -fiso coroutine.mod && ./a.out would be a simple test.