In the following testcase: // { dg-do compile { target c++20 } } struct S { virtual constexpr int foo () const { return 42; } }; constexpr S s; constexpr auto a = &S::foo; constexpr auto b = (s.*a) (); constexpr auto c = (s.*&S::foo) (); we correctly accept b's initializer, but reject c's initializer with: error: value ‘1’ of type ‘int (S::*)() const’ is not a constant expression
This might be a dup.
Confirmed.
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>: https://gcc.gnu.org/g:f45610a45236e97616726ca042898d6ac46a082e commit r12-4491-gf45610a45236e97616726ca042898d6ac46a082e Author: Jakub Jelinek <jakub@redhat.com> Date: Tue Oct 19 09:24:57 2021 +0200 c++: Don't reject calls through PMF during constant evaluation [PR102786] The following testcase incorrectly rejects the c initializer, while in the s.*a case cxx_eval_* sees .__pfn reads etc., in the s.*&S::foo case get_member_function_from_ptrfunc creates expressions which use INTEGER_CSTs with type of pointer to METHOD_TYPE. And cxx_eval_constant_expression rejects any INTEGER_CSTs with pointer type if they aren't 0. Either we'd need to make sure we defer such folding till cp_fold but the function and pfn_from_ptrmemfunc is used from lots of places, or the following patch just tries to reject only non-zero INTEGER_CSTs with pointer types if they don't point to METHOD_TYPE in the hope that all such INTEGER_CSTs with POINTER_TYPE to METHOD_TYPE are result of folding valid pointer-to-member function expressions. I don't immediately see how one could create such INTEGER_CSTs otherwise, cast of integers to PMF is rejected and would have the PMF RECORD_TYPE anyway, etc. 2021-10-19 Jakub Jelinek <jakub@redhat.com> PR c++/102786 * constexpr.c (cxx_eval_constant_expression): Don't reject INTEGER_CSTs with type POINTER_TYPE to METHOD_TYPE. * g++.dg/cpp2a/constexpr-virtual19.C: New test.
The releases/gcc-11 branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>: https://gcc.gnu.org/g:62e4f0e8977497e01d2c262a3bd459ab26a5aaca commit r11-9326-g62e4f0e8977497e01d2c262a3bd459ab26a5aaca Author: Jakub Jelinek <jakub@redhat.com> Date: Tue Oct 19 09:24:57 2021 +0200 c++: Don't reject calls through PMF during constant evaluation [PR102786] The following testcase incorrectly rejects the c initializer, while in the s.*a case cxx_eval_* sees .__pfn reads etc., in the s.*&S::foo case get_member_function_from_ptrfunc creates expressions which use INTEGER_CSTs with type of pointer to METHOD_TYPE. And cxx_eval_constant_expression rejects any INTEGER_CSTs with pointer type if they aren't 0. Either we'd need to make sure we defer such folding till cp_fold but the function and pfn_from_ptrmemfunc is used from lots of places, or the following patch just tries to reject only non-zero INTEGER_CSTs with pointer types if they don't point to METHOD_TYPE in the hope that all such INTEGER_CSTs with POINTER_TYPE to METHOD_TYPE are result of folding valid pointer-to-member function expressions. I don't immediately see how one could create such INTEGER_CSTs otherwise, cast of integers to PMF is rejected and would have the PMF RECORD_TYPE anyway, etc. 2021-10-19 Jakub Jelinek <jakub@redhat.com> PR c++/102786 * constexpr.c (cxx_eval_constant_expression): Don't reject INTEGER_CSTs with type POINTER_TYPE to METHOD_TYPE. * g++.dg/cpp2a/constexpr-virtual19.C: New test. (cherry picked from commit f45610a45236e97616726ca042898d6ac46a082e)
Fixed.
The releases/gcc-10 branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>: https://gcc.gnu.org/g:536b03642ad1a32100f71d414e6bd6dc54fc208a commit r10-10650-g536b03642ad1a32100f71d414e6bd6dc54fc208a Author: Jakub Jelinek <jakub@redhat.com> Date: Tue Oct 19 09:24:57 2021 +0200 c++: Don't reject calls through PMF during constant evaluation [PR102786] The following testcase incorrectly rejects the c initializer, while in the s.*a case cxx_eval_* sees .__pfn reads etc., in the s.*&S::foo case get_member_function_from_ptrfunc creates expressions which use INTEGER_CSTs with type of pointer to METHOD_TYPE. And cxx_eval_constant_expression rejects any INTEGER_CSTs with pointer type if they aren't 0. Either we'd need to make sure we defer such folding till cp_fold but the function and pfn_from_ptrmemfunc is used from lots of places, or the following patch just tries to reject only non-zero INTEGER_CSTs with pointer types if they don't point to METHOD_TYPE in the hope that all such INTEGER_CSTs with POINTER_TYPE to METHOD_TYPE are result of folding valid pointer-to-member function expressions. I don't immediately see how one could create such INTEGER_CSTs otherwise, cast of integers to PMF is rejected and would have the PMF RECORD_TYPE anyway, etc. 2021-10-19 Jakub Jelinek <jakub@redhat.com> PR c++/102786 * constexpr.c (cxx_eval_constant_expression): Don't reject INTEGER_CSTs with type POINTER_TYPE to METHOD_TYPE. * g++.dg/cpp2a/constexpr-virtual19.C: New test. (cherry picked from commit f45610a45236e97616726ca042898d6ac46a082e)
The releases/gcc-9 branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>: https://gcc.gnu.org/g:662de049d63759b731bed62f9df60edb47120658 commit r9-10106-g662de049d63759b731bed62f9df60edb47120658 Author: Jakub Jelinek <jakub@redhat.com> Date: Tue Oct 19 09:24:57 2021 +0200 c++: Don't reject calls through PMF during constant evaluation [PR102786] The following testcase incorrectly rejects the c initializer, while in the s.*a case cxx_eval_* sees .__pfn reads etc., in the s.*&S::foo case get_member_function_from_ptrfunc creates expressions which use INTEGER_CSTs with type of pointer to METHOD_TYPE. And cxx_eval_constant_expression rejects any INTEGER_CSTs with pointer type if they aren't 0. Either we'd need to make sure we defer such folding till cp_fold but the function and pfn_from_ptrmemfunc is used from lots of places, or the following patch just tries to reject only non-zero INTEGER_CSTs with pointer types if they don't point to METHOD_TYPE in the hope that all such INTEGER_CSTs with POINTER_TYPE to METHOD_TYPE are result of folding valid pointer-to-member function expressions. I don't immediately see how one could create such INTEGER_CSTs otherwise, cast of integers to PMF is rejected and would have the PMF RECORD_TYPE anyway, etc. 2021-10-19 Jakub Jelinek <jakub@redhat.com> PR c++/102786 * constexpr.c (cxx_eval_constant_expression): Don't reject INTEGER_CSTs with type POINTER_TYPE to METHOD_TYPE. * g++.dg/cpp2a/constexpr-virtual19.C: New test. (cherry picked from commit f45610a45236e97616726ca042898d6ac46a082e)