https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118319
--- Comment #6 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Simon Martin <simar...@gcc.gnu.org>: https://gcc.gnu.org/g:198f4df07d6a1db9c8ef39536da56c1b596c57a8 commit r15-7380-g198f4df07d6a1db9c8ef39536da56c1b596c57a8 Author: Simon Martin <si...@nasilyan.com> Date: Wed Feb 5 20:35:34 2025 +0100 c++: Reject default arguments for template class friend functions [PR118319] We segfault upon the following invalid code === cut here === template <int> struct S { friend void foo (int a = []{}()); }; void foo (int a) {} int main () { S<0> t; foo (); } === cut here === The problem is that we end up with a LAMBDA_EXPR callee in set_flags_from_callee, and dereference its NULL_TREE TREE_TYPE (TREE_TYPE (..)). This patch sets the default argument to error_mark_node and gives a hard error for template class friend functions that do not meet the requirement in C++17 11.3.6/4 (the change is restricted to templates per discussion with Jason). PR c++/118319 gcc/cp/ChangeLog: * decl.cc (grokfndecl): Inspect all friend function parameters. If it's not valid for them to have a default value and we're processing a template, set the default value to error_mark_node and give a hard error. gcc/testsuite/ChangeLog: * g++.dg/parse/defarg18.C: New test. * g++.dg/parse/defarg18a.C: New test.
