https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87068
Bug ID: 87068 Summary: No diagnostic on an ill-formed [[fallthrough]] Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: luk32 at o2 dot pl Target Milestone: --- gcc cleanly compiles an ill-formed [[fallthrough]] example from the standard, producing no diagnostic. I believe it's a bug. Problematic code: // http://eel.is/c++draft/dcl.attr.fallthrough void f(int n) { void g(), h(), i(); switch (n) { case 1: case 2: g(); [[fallthrough]]; case 3: // warning on fallthrough discouraged h(); case 4: // implementation may warn on fallthrough i(); [[fallthrough]]; // ill-formed } } Live example https://godbolt.org/z/fftSM- Credit: https://stackoverflow.com/questions/51983560/should-there-be-a-diagnostic-from-from-gcc-for-this-ill-formed-c-code