[{"id":3679905,"web_url":"http://patchwork.ozlabs.org/comment/3679905/","msgid":"","list_archive_url":null,"date":"2026-04-21T14:13:31","subject":"Re: [PATCH] libstdc++: Implement __integral_constant_like in terms of\n __constexpr_wrapper_like.","submitter":{"id":48004,"url":"http://patchwork.ozlabs.org/api/people/48004/","name":"Jonathan Wakely","email":"jwakely@redhat.com"},"content":"On Tue, 21 Apr 2026 at 15:10, Tomasz Kamiński wrote:\n>\n> This implements LWG4486. integral-constant-like and constexpr-wrapper-like\n> exposition-only concept duplication.\n>\n> libstdc++-v3/ChangeLog:\n>\n> * include/bits/simd_details.h (simd::__constexpr_wrapper_like):\n> Move to...\n> * include/std/concepts (std::__constexpr_wrapper_like): Moved\n> from bits/simd_details.h.\n> * include/std/span (std::__integral_constant_like): Define in\n> terms of __constexpr_wrapper_like.\n> * testsuite/std/simd/traits_impl.cc: Added using declaration\n> for std::__constexpr_wrapper_like.\n> ---\n>\n> Tested on x86_64-linux locally. OK for trunk/stage-1?\n> I done it, to double check if they are in sync. This impacts span in C++20 mode,\n> so maybe it is safer to keep it for stage-1. From other seems safe, i.e. should\n> work as soon as test passes.\n>\n> libstdc++-v3/include/bits/simd_details.h | 7 -------\n> libstdc++-v3/include/std/concepts | 9 +++++++++\n> libstdc++-v3/include/std/span | 8 +++-----\n> libstdc++-v3/testsuite/std/simd/traits_impl.cc | 1 +\n> 4 files changed, 13 insertions(+), 12 deletions(-)\n>\n> diff --git a/libstdc++-v3/include/bits/simd_details.h b/libstdc++-v3/include/bits/simd_details.h\n> index 31bd6ac45ab..408a344d2ec 100644\n> --- a/libstdc++-v3/include/bits/simd_details.h\n> +++ b/libstdc++-v3/include/bits/simd_details.h\n> @@ -1030,13 +1030,6 @@ namespace simd\n> /** @internal\n> * C++26 [simd.expos]\n> */\n> - template\n> - concept __constexpr_wrapper_like\n> - = convertible_to<_Tp, decltype(_Tp::value)>\n> - && equality_comparable_with<_Tp, decltype(_Tp::value)>\n> - && bool_constant<_Tp() == _Tp::value>::value\n> - && bool_constant(_Tp()) == _Tp::value>::value;\n> -\n> // [simd.ctor] explicit(...) of broadcast ctor\n> template \n> concept __non_narrowing_constexpr_conversion\n> diff --git a/libstdc++-v3/include/std/concepts b/libstdc++-v3/include/std/concepts\n> index 7673443f33a..328096a89e3 100644\n> --- a/libstdc++-v3/include/std/concepts\n> +++ b/libstdc++-v3/include/std/concepts\n> @@ -421,6 +421,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION\n> && ! requires(_Tp&& __t, _Up&& __u)\n> { static_cast<_Up&&>(__u).operator<=>(static_cast<_Tp&&>(__t)); }));\n> }\n> +\n> + // [expos.only.entity]\n> + template\n> + concept __constexpr_wrapper_like\n> + = convertible_to<_Tp, decltype(_Tp::value)>\n> + && equality_comparable_with<_Tp, decltype(_Tp::value)>\n> + && bool_constant<_Tp() == _Tp::value>::value\n> + && bool_constant(_Tp()) == _Tp::value>::value;\n> +\n> _GLIBCXX_END_NAMESPACE_VERSION\n> } // namespace\n> #endif // __cpp_lib_concepts\n> diff --git a/libstdc++-v3/include/std/span b/libstdc++-v3/include/std/span\n> index a5f5bf48f90..1215ce826f6 100644\n> --- a/libstdc++-v3/include/std/span\n> +++ b/libstdc++-v3/include/std/span\n> @@ -467,15 +467,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION\n> {\n> // _GLIBCXX_RESOLVE_LIB_DEFECTS\n> // 4351. integral-constant-like needs more remove_cvref_t\n> + // 4486. integral-constant-like and constexpr-wrapper-like exposition-only\n> + // concept duplicatiob\n\nTypo: duplication\n\nOK for stage 1\n\n\n> template\n> concept __integral_constant_like =\n> is_integral_v>\n> && !is_same_v>\n> - && convertible_to<_Tp, decltype(_Tp::value)>\n> - && equality_comparable_with<_Tp, decltype(_Tp::value)>\n> - && bool_constant<_Tp() == _Tp::value>::value\n> - && bool_constant(_Tp()) == _Tp::value>\n> - ::value;\n> + && __constexpr_wrapper_like<_Tp>;\n>\n> template\n> constexpr size_t __maybe_static_ext = dynamic_extent;\n> diff --git a/libstdc++-v3/testsuite/std/simd/traits_impl.cc b/libstdc++-v3/testsuite/std/simd/traits_impl.cc\n> index f73a9e3beb5..2f705c7df2f 100644\n> --- a/libstdc++-v3/testsuite/std/simd/traits_impl.cc\n> +++ b/libstdc++-v3/testsuite/std/simd/traits_impl.cc\n> @@ -16,6 +16,7 @@ using std::float32_t;\n> using std::float64_t;\n>\n> using namespace std::simd;\n> +using std::__constexpr_wrapper_like;\n>\n> template \n> void test()\n> --\n> 2.53.0\n>","headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","gcc-patches@gcc.gnu.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","gcc-patches@gcc.gnu.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=bL4vIrPP;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=38.145.34.32; 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