https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65377
npl at chello dot at changed: What |Removed |Added ---------------------------------------------------------------------------- Status|RESOLVED |UNCONFIRMED Resolution|INVALID |--- --- Comment #3 from npl at chello dot at --- 1) It simply shouldnt fail. 2) this is a generic header for C and C++. __has_cpp_attribute(clang::fallthrough) should resolve to 0 and not fail. This is a bug in gcc, unless you can explain why it shouldnt resolve to 0.