https://gcc.gnu.org/g:0ac5a60c37d9a40e8993b8207e904b713e73b5d3
commit r16-5488-g0ac5a60c37d9a40e8993b8207e904b713e73b5d3 Author: Jakub Jelinek <[email protected]> Date: Fri Nov 21 14:17:01 2025 +0100 c++: Fix up build_data_member_initialization [PR121445] The following testcase ICEs, because the constexpr ctor in C++14 or later doesn't contain any member initializers and so the massage_constexpr_body -> build_constexpr_constructor_member_initializers -> build_data_member_initialization member initialization discovery looks at the ctor body instead. And while it has various cases where it punts, including COMPONENT_REF with a VAR_DECL as first operand on lhs of INIT_EXPR, here there is COMPONENT_REF with several COMPONENT_REFs and VAR_DECL only inside the innermost. The following patch makes sure we punt on those as well, instead of blindly assuming it is anonymous union member initializer or asserting it is a vtable store. An alternative to this would be some flag on the INIT_EXPRs created by perform_member_init and let build_data_member_initialization inspect only INIT_EXPRs with that flag set. 2025-11-21 Jakub Jelinek <[email protected]> PR c++/121445 * constexpr.cc (build_data_member_initialization): Just return false if member is COMPONENT_REF of COMPONENT_REF with VAR_P get_base_address. * g++.dg/cpp1y/constexpr-121445.C: New test. Diff: --- gcc/cp/constexpr.cc | 3 +++ gcc/testsuite/g++.dg/cpp1y/constexpr-121445.C | 19 +++++++++++++++++++ 2 files changed, 22 insertions(+) diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index 016e3db927c9..e091e8643a01 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -477,6 +477,9 @@ build_data_member_initialization (tree t, vec<constructor_elt, va_gc> **vec) if (TREE_CODE (aggr) != COMPONENT_REF) /* Normal member initialization. */ member = TREE_OPERAND (member, 1); + else if (VAR_P (get_base_address (aggr))) + /* Initializing a local variable, don't add anything. */ + return true; else if (ANON_AGGR_TYPE_P (TREE_TYPE (aggr))) /* Initializing a member of an anonymous union. */ return build_anon_member_initialization (member, init, vec); diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-121445.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-121445.C new file mode 100644 index 000000000000..b210aaffaf40 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-121445.C @@ -0,0 +1,19 @@ +// PR c++/121445 +// { dg-do compile { target c++14 } } + +struct D { + const char *d; + const char *foo () { return ""; }; // { dg-message "declared here" "" { target c++20_down } } + constexpr D () : d (foo ()) {} // { dg-error "call to non-'constexpr' function 'const char\\\* D::foo\\\(\\\)'" "" { target c++20_down } } + constexpr D &operator= (const char *) { return *this; } +}; +struct S { + constexpr S () + { + struct A { D a; }; + struct B { A b; }; + struct C { B c; }; + C d {}; + d.c.b.a = ""; + } +};
