https://gcc.gnu.org/g:ca57ad11199ea822a5e72131b3f154de93853fe6
commit r16-9877-gca57ad11199ea822a5e72131b3f154de93853fe6 Author: Jakub Jelinek <[email protected]> Date: Wed Oct 21 09:04:21 2026 +0200 c++: Call check_trait_type for CPTK_STRUCTURED_BINDING_SIZE [PR127766] The following testcase is rejected because we don't even try to complete the type, so if it wasn't instantiated with those arguments before, we reject it. Fixed up calling check_trait_type, with kind 4, for non-class I think cp_decomp_size already does the right thing, for arrays we actually just care about number of elements. On the pt.cc side, fixed by removing the special casing of this exact trait and instead passing complain to all finish_trait_expr calls in TRAIT_EXPR case. 2026-10-21 Jakub Jelinek <[email protected]> PR c++/127766 * semantics.cc (finish_structured_binding_size): Call check_trait_type with kind 4. * g++.dg/ext/builtin-structured-binding-size2.C: Expect different diagnostics. * g++.dg/ext/builtin-structured-binding-size7.C: New test. Reviewed-by: Jason Merrill <[email protected]> (cherry picked from commit 1498f0547eb1692c39c63ad3e8e22859dc526e3e) Diff: --- gcc/cp/semantics.cc | 2 ++ gcc/testsuite/g++.dg/ext/builtin-structured-binding-size2.C | 2 +- gcc/testsuite/g++.dg/ext/builtin-structured-binding-size7.C | 10 ++++++++++ 3 files changed, 13 insertions(+), 1 deletion(-) diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc index 7e9a29aa3ba0..3b5f61ef4ccf 100644 --- a/gcc/cp/semantics.cc +++ b/gcc/cp/semantics.cc @@ -14321,6 +14321,8 @@ tree finish_structured_binding_size (location_t loc, tree type, tsubst_flags_t complain) { + if (!check_trait_type (type, /* kind = */ 4, complain)) + return error_mark_node; if (TYPE_REF_P (type)) { if (complain & tf_error) diff --git a/gcc/testsuite/g++.dg/ext/builtin-structured-binding-size2.C b/gcc/testsuite/g++.dg/ext/builtin-structured-binding-size2.C index 9abd80fec9d5..ebdc08ec19ff 100644 --- a/gcc/testsuite/g++.dg/ext/builtin-structured-binding-size2.C +++ b/gcc/testsuite/g++.dg/ext/builtin-structured-binding-size2.C @@ -21,7 +21,7 @@ template <> struct std::tuple_size <C> { static constexpr double value = 42; }; template <> struct std::tuple_size <D> { static constexpr int value = -1; }; -int a = __builtin_structured_binding_size (A); // { dg-error "structured binding refers to incomplete class type 'A'" } +int a = __builtin_structured_binding_size (A); // { dg-error "invalid use of incomplete type 'struct A'" } int b = __builtin_structured_binding_size (A &); // { dg-error "'__builtin_structured_binding_size' argument 'A\\\&' is a reference" } int c = __builtin_structured_binding_size (B[]); // { dg-error "cannot decompose array of unknown bound 'B \\\[\\\]'" } int d = __builtin_structured_binding_size (C); // { dg-error "'std::tuple_size<C>::value' is not an integral constant expression" } diff --git a/gcc/testsuite/g++.dg/ext/builtin-structured-binding-size7.C b/gcc/testsuite/g++.dg/ext/builtin-structured-binding-size7.C new file mode 100644 index 000000000000..d12934b5ac75 --- /dev/null +++ b/gcc/testsuite/g++.dg/ext/builtin-structured-binding-size7.C @@ -0,0 +1,10 @@ +// PR c++/127766 +// { dg-do compile { target c++11 } } + +template <typename T> struct A { T a, b; }; +static_assert (__builtin_structured_binding_size (A <int>) == 2, ""); + +template <typename T> struct B { T a, b, c; }; +template <typename T> +constexpr int foo () { return __builtin_structured_binding_size (B<T>); } +static_assert (foo <int> () == 3, "");
