The following code causes an internal compiler error in GCC 14 and trunk: https://gcc.godbolt.org/z/j5Y945fMq struct A { int x; void foo(this auto &&self) noexcept(noexcept(self.x)) {} auto bar() -> decltype(foo()) {} }; This results in the following error: <source>: In instantiation of 'void A::foo(this auto:1&&) [with auto:1 = A&]': <source>:5:35: required from here 5 | auto bar() -> decltype(foo()) {} | ~~~^~ <source>:4:14: internal compiler error: in tsubst_expr, at cp/pt.cc:21978 4 | void foo(this auto &&self) noexcept(noexcept(self.x)) {} | ^~~ 0x285c505 diagnostic_context::diagnostic_impl(rich_location*, diagnostic_metadata const*, diagnostic_option_id, char const*, __va_list_tag (*) [1], diagnostic_t) ???:0 0x28702e5 internal_error(char const*, ...) ???:0 0xa8b484 fancy_abort(char const*, int, char const*) ???:0 0xccfed2 maybe_instantiate_noexcept(tree_node*, int) ???:0 0xb8c2ea mark_used(tree_node*, int) ???:0 0xab6458 build_new_method_call(tree_node*, tree_node*, vec<tree_node*, va_gc, vl_embed>**, tree_node*, int, tree_node**, int) ???:0 0xd17106 finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**, bool, bool, int) ???:0 0xc989da c_parse_file() ???:0 0xdf0599 c_common_parse_file() ???:0 Worth noting that Clang emits a weird error on this code: https://stackoverflow.com/q/79081096/2752075 error: exception specification is not available until end of class definition
This crash is reproducible in C++20 mode as well without deducing this: ``` struct A { int x; void foo(this auto &&self) noexcept(noexcept(self.x)) {} auto bar() -> decltype(foo()) {} }; ``` In instantiation of 'void A::foo() [with <template-parameter-1-1> = int]': <source>:5:36: required from here 5 | auto bar() -> decltype(foo<int>()) {} | ~~~~~~~~^~ <source>:4:10: internal compiler error: Segmentation fault 4 | void foo() noexcept(noexcept(x)) {} | ^~~ 0x2031cbc internal_error(char const*, ...) ???:0 0x11fb4f4 check_qualified_type(tree_node const*, tree_node const*, int) ???:0 0x11fb5f3 get_qualified_type(tree_node*, int) ???:0 0x1206345 build_qualified_type(tree_node*, int) ???:0 0x843cba build_noexcept_spec(tree_node*, int) ???:0 0x9301e1 maybe_instantiate_noexcept(tree_node*, int) ???:0 0x83311a mark_used(tree_node*, int) ???:0 0x79d629 build_new_method_call(tree_node*, tree_node*, vec<tree_node*, va_gc, vl_embed>**, tree_node*, int, tree_node**, int) ???:0 0x960c3c finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**, bool, bool, int) ???:0 0x90ee14 c_parse_file() ???:0 0xa0d1b9 c_common_parse_file() ???:0 Online demo: https://gcc.godbolt.org/z/PW6sn8Tjq
Started with r12-6025 so mine. commit 06041b2c67a5d4d0941c53990f0438a309703ed0 Author: Marek Polacek <polacek@redhat.com> Date: Wed Dec 15 17:41:53 2021 -0500 c++: delayed noexcept in member function template [PR99980]
(comment #1 corrected) > This crash is reproducible in C++20 mode as well without deducing this: ``` struct A { int x; template<class> void foo() noexcept(noexcept(x)) {} auto bar() -> decltype(foo<int>()) {} }; ```
The trunk branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>: https://gcc.gnu.org/g:f5ef1f9e8589697086c8cfea6ad07d56050dde96 commit r15-7417-gf5ef1f9e8589697086c8cfea6ad07d56050dde96 Author: Marek Polacek <polacek@redhat.com> Date: Thu Feb 6 08:57:22 2025 -0500 c++: ICE with unparsed noexcept [PR117106] In a member-specification of a class, a noexcept-specifier is a complete-class context. Thus we delay parsing until the end of the class via our DEFERRED_PARSE mechanism; see cp_parser_save_noexcept and cp_parser_late_noexcept_specifier. We also attempt to defer instantiation of noexcept-specifiers in order to reduce the number of instantiations; this is done via DEFERRED_NOEXCEPT. We can even have both, as in noexcept65.C: a DEFERRED_PARSE wrapped in DEFERRED_NOEXCEPT, which uses the DEFPARSE_INSTANTIATIONS mechanism. noexcept65.C works, because when we really need the noexcept, which is when parsing the body of S::A::A(), the noexcept will have been parsed already; noexcepts are parsed before bodies of member function. But in this test we have: struct A { int x; template<class> void foo() noexcept(noexcept(x)) {} auto bar() -> decltype(foo<int>()) {} // #1 }; and I think the decltype in #1 needs the unparsed noexcept before it could have been parsed. clang++ rejects the test and I suppose we should reject it as well, rather than crashing on a DEFERRED_PARSE in tsubst_expr. PR c++/117106 PR c++/118190 gcc/cp/ChangeLog: * pt.cc (maybe_instantiate_noexcept): Give an error if the noexcept hasn't been parsed yet. gcc/testsuite/ChangeLog: * g++.dg/cpp0x/noexcept89.C: New test. * g++.dg/cpp0x/noexcept90.C: New test. Reviewed-by: Jason Merrill <jason@redhat.com>
Fixed for 15.