https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116443
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- I don't think this is technically a bug. The C standard requires an integral constant expression for a case label, and "str"[0] is not required to be an integral constant expression. The C standard does allow implementations to be flexible in what they consider to be integral constant expressions, so Clang is allowed to accept this code, but it's not required to accept it. So if GCC accepted this, it would be as a non-standard extension.
