https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96380
--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Marek Polacek <mpola...@gcc.gnu.org>: https://gcc.gnu.org/g:001c63d15e31bc0a1545426d889a0b9f671b4961 commit r12-42-g001c63d15e31bc0a1545426d889a0b9f671b4961 Author: Marek Polacek <pola...@redhat.com> Date: Tue Apr 20 12:16:04 2021 -0400 c++: Don't allow defining types in enum-base [PR96380] In r11-2064 I made cp_parser_enum_specifier commit to tentative parse when seeing a '{'. That still looks like the correct thing to do, but it caused an ICE-on-invalid as well as accepts-invalid. When we have something sneaky like this, which is broken in multiple ways: template <class> enum struct c : union enum struct c { e = b, f = a }; we parse the "enum struct c" part (that's OK) and then we see that we have an enum-base, so we consume ':' and then parse the type-specifier that follows the :. "union enum" is clearly invalid, but we're still parsing tentatively and we parse everything up to the ;, and then throw away the underlying type. We parsed everything because we were tricked into parsing an enum-specifier in an enum-base of another enum-specifier! Not good. Since the grammar for enum-base doesn't allow a defining-type-specifier, only a type-specifier, we should set type_definition_forbidden_message which fixes all the problems in this PR. gcc/cp/ChangeLog: PR c++/96380 * parser.c (cp_parser_enum_specifier): Don't allow defining types in enum-base. gcc/testsuite/ChangeLog: PR c++/96380 * g++.dg/cpp0x/enum_base4.C: New test. * g++.dg/cpp0x/enum_base5.C: New test.
