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From: Jason Merrill <jason@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-576] c++: constexpr ref to array of array [PR102307] Date: Tue, 17 May 2022 22:09:29 +0000 (GMT) [thread overview] Message-ID: <20220517220929.6DB02385740B@sourceware.org> (raw) https://gcc.gnu.org/g:2b0c8377729a3c62a05897136666574ab939aaab commit r13-576-g2b0c8377729a3c62a05897136666574ab939aaab Author: Jason Merrill <jason@redhat.com> Date: Tue Apr 26 11:15:04 2022 -0400 c++: constexpr ref to array of array [PR102307] The problem here is that first check_initializer calls build_aggr_init_full_exprs, which does overload resolution, but then in the case of failed constexpr throws away the result and does it again in build_functional_cast. But in the first overload resolution, reshape_init_array_1 decided to reuse the inner CONSTRUCTORs because tf_error is set, so we know we're committed. But the second pass gets confused by the CONSTRUCTORs with non-init-list types. Fixed by avoiding a second pass: instead, pass the call from build_aggr_init to build_cplus_new, which will turn it into a TARGET_EXPR. I don't bother to change the object argument because it will be replaced later in simplify_aggr_init_expr. PR c++/102307 gcc/cp/ChangeLog: * decl.cc (check_initializer): Use build_cplus_new in case of constexpr failure. gcc/testsuite/ChangeLog: * g++.dg/cpp1z/constexpr-array2.C: New test. Diff: --- gcc/cp/decl.cc | 17 ++++++++++++----- gcc/testsuite/g++.dg/cpp1z/constexpr-array2.C | 12 ++++++++++++ 2 files changed, 24 insertions(+), 5 deletions(-) diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc index 5654bc754e6..381259cb9cf 100644 --- a/gcc/cp/decl.cc +++ b/gcc/cp/decl.cc @@ -7413,12 +7413,19 @@ check_initializer (tree decl, tree init, int flags, vec<tree, va_gc> **cleanups) /* Declared constexpr or constinit, but no suitable initializer; massage init appropriately so we can pass it into store_init_value for the error. */ - if (CLASS_TYPE_P (type) - && (!init || TREE_CODE (init) == TREE_LIST)) + tree new_init = NULL_TREE; + if (!processing_template_decl + && TREE_CODE (init_code) == CALL_EXPR) + new_init = build_cplus_new (type, init_code, tf_none); + else if (CLASS_TYPE_P (type) + && (!init || TREE_CODE (init) == TREE_LIST)) + new_init = build_functional_cast (input_location, type, + init, tf_none); + if (new_init) { - init = build_functional_cast (input_location, type, - init, tf_none); - if (TREE_CODE (init) == TARGET_EXPR) + init = new_init; + if (TREE_CODE (init) == TARGET_EXPR + && !(flags & LOOKUP_ONLYCONVERTING)) TARGET_EXPR_DIRECT_INIT_P (init) = true; } init_code = NULL_TREE; diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-array2.C b/gcc/testsuite/g++.dg/cpp1z/constexpr-array2.C new file mode 100644 index 00000000000..c30e3f2361d --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-array2.C @@ -0,0 +1,12 @@ +// PR c++/102307 +// { dg-do compile { target c++11 } } + +#include <array> +template <unsigned N, unsigned M> struct Matrix { + constexpr Matrix(double const (&arr)[N][M]); // { dg-warning "never defined" } + constexpr Matrix(std::array<std::array<double, M>, N> const &arr); +}; +int main() { + constexpr Matrix<2, 3> + mat {{ {1.0, 2.0, 3.0}, {4.0, 5.0, 6.0} }}; // { dg-error "before its definition" } +}
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