https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106259
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Marek Polacek <mpola...@gcc.gnu.org>: https://gcc.gnu.org/g:71afd0628419c5d670701cb35bc9860380c7d9fb commit r13-6417-g71afd0628419c5d670701cb35bc9860380c7d9fb Author: Marek Polacek <pola...@redhat.com> Date: Wed Mar 1 14:28:46 2023 -0500 c++: ICE with -Wmismatched-tags and member template [PR106259] -Wmismatched-tags warns about the (harmless) struct/class mismatch. For, e.g., template<typename T> struct A { }; class A<int> a; it works by adding A<T> to the class2loc hash table while parsing the class-head and then, while parsing the elaborate type-specifier, we add A<int>. At the end of c_parse_file we go through the table and warn about the class-key mismatches. In this PR we crash though; we have template<typename T> struct A { template<typename U> struct W { }; }; struct A<int>::W<int> w; // #1 where while parsing A and #1 we've stashed A<T> A<T>::W<U> A<int>::W<int> into class2loc. Then in class_decl_loc_t::diag_mismatched_tags TYPE is A<int>::W<int>, and specialization_of gets us A<int>::W<U>, which is not in class2loc, so we crash on gcc_assert (cdlguide). But it's OK not to have found A<int>::W<U>, we should just look one "level" up, that is, A<T>::W<U>. It's important to handle class specializations, so e.g. template<> struct A<char> { template<typename U> class W { }; }; where W's class-key is different than in the primary template above, so we should warn depending on whether we're looking into A<char> or into a different instantiation. PR c++/106259 gcc/cp/ChangeLog: * parser.cc (class_decl_loc_t::diag_mismatched_tags): If the first lookup of SPEC didn't find anything, try to look for most_general_template. gcc/testsuite/ChangeLog: * g++.dg/warn/Wmismatched-tags-11.C: New test.
