http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55587
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-12-04 09:40:44 UTC --- asan.exp starts with if ![check_effective_target_faddress_sanitizer] { return } but that just checks whether -fsanitize=address works, not whether libasan has been built. That further check is in asan_init, guess we could return 0/1 from asan_init on whether it found libasan and if it hasn't, don't call gcc-dg-runtest.