https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110382
--- Comment #8 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-13 branch has been updated by Marek Polacek <mpola...@gcc.gnu.org>: https://gcc.gnu.org/g:a82583e43eaacab9a111d1fca14c7d272aa3e039 commit r13-9294-ga82583e43eaacab9a111d1fca14c7d272aa3e039 Author: Marek Polacek <pola...@redhat.com> Date: Fri Jul 21 17:48:37 2023 -0400 c++: fix ICE with constexpr ARRAY_REF [PR110382] This code in cxx_eval_array_reference has been hard to get right. In r12-2304 I added some code; in r13-5693 I removed some of it. Here the problematic line is "S s = arr[0];" which causes a crash on the assert in verify_ctor_sanity: gcc_assert (!ctx->object || !DECL_P (ctx->object) || ctx->global->get_value (ctx->object) == ctx->ctor); ctx->object is the VAR_DECL 's', which is correct here. The second line points to the problem: we replaced ctx->ctor in cxx_eval_array_reference: new_ctx.ctor = build_constructor (elem_type, NULL); // #1 which I think we shouldn't have; the CONSTRUCTOR we created in cxx_eval_constant_expression/DECL_EXPR new_ctx.ctor = build_constructor (TREE_TYPE (r), NULL); had the right type. We still need #1 though. E.g., in constexpr-96241.C, we never set ctx.ctor/object before calling cxx_eval_array_reference, so we have to build a CONSTRUCTOR there. And in constexpr-101371-2.C we have a ctx.ctor, but it has the wrong type, so we need a new one. We can fix the problem by always clearing the object, and, as an optimization, only create/free a new ctor when actually needed. PR c++/110382 gcc/cp/ChangeLog: * constexpr.cc (cxx_eval_array_reference): Create a new constructor only when we don't already have a matching one. Clear the object when the type is non-scalar. gcc/testsuite/ChangeLog: * g++.dg/cpp1y/constexpr-110382.C: New test. (cherry picked from commit 6e424febfbcb27c21a7fe3a137e614765f9cf9d2)
