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From: "mpolacek at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/109680] [13/14 Regression] is_convertible<int() const, int(*)()> incorrectly true Date: Tue, 02 May 2023 19:22:15 +0000 [thread overview] Message-ID: <bug-109680-4-MxrlsQJ1lT@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-109680-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109680 --- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> --- Ah, I think I see what's going on here. Once again, the problem is that this assert no longer passes: #include <utility> static_assert (!std::is_convertible_v <int () const, int (*) ()>, ""); std::is_convertible does To test() { return std::declval<From>(); } here, From is 'int () const'. std::declval is defined as: template<class T> typename std::add_rvalue_reference<T>::type declval() noexcept; Now, std::add_rvalue_reference is defined as "If T is a function type that has no cv- or ref- qualifier or an object type, provides a member typedef type which is T&&, otherwise type is T." In our case, T is cv-qualified, so the result is T, so we end up with int () const declval() noexcept; which is invalid. In other words: using T = int () const; T fn1(); // bad, fn returning a fn T& fn2(); // bad, cannot declare reference to qualified function type T* fn3(); // bad, cannot declare pointer to qualified function type using U = int (); U fn4(); // bad, fn returning a fn U& fn5(); // OK U* fn6(); // OK So the check we're looking for is probably if (TREE_CODE (type) == FUNCTION_TYPE && (type_memfn_quals (type) != TYPE_UNQUALIFIED || type_memfn_rqual (type) != REF_QUAL_NONE)) but I think it should be put wherever we simulate declval().
next prev parent reply other threads:[~2023-05-02 19:22 UTC|newest] Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-04-29 17:13 [Bug c++/109680] New: Regression where `int() const` is considered convertible to `int(*)()` dpsicilia at gmail dot com 2023-04-29 17:28 ` [Bug c++/109680] " pinskia at gcc dot gnu.org 2023-04-29 17:42 ` [Bug c++/109680] [13/14 Regression] is_convertible<int() const, int(*)()> incorrectly true pinskia at gcc dot gnu.org 2023-05-01 9:03 ` jakub at gcc dot gnu.org 2023-05-01 16:09 ` mpolacek at gcc dot gnu.org 2023-05-01 16:32 ` jakub at gcc dot gnu.org 2023-05-01 23:13 ` mpolacek at gcc dot gnu.org 2023-05-02 7:36 ` jakub at gcc dot gnu.org 2023-05-02 19:22 ` mpolacek at gcc dot gnu.org [this message] 2023-05-03 12:58 ` mpolacek at gcc dot gnu.org 2023-05-10 22:25 ` cvs-commit at gcc dot gnu.org 2023-05-10 22:25 ` [Bug c++/109680] [13 " mpolacek at gcc dot gnu.org 2023-07-03 12:08 ` dpsicilia at gmail dot com 2023-07-03 12:36 ` redi at gcc dot gnu.org 2023-07-27 9:25 ` rguenth at gcc dot gnu.org 2023-08-04 18:08 ` pinskia at gcc dot gnu.org 2024-05-21 9:14 ` jakub at gcc dot gnu.org
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