{"id":2226068,"url":"http://patchwork.ozlabs.org/api/patches/2226068/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/20260422073435.140670-1-tkaminsk@redhat.com/","project":{"id":17,"url":"http://patchwork.ozlabs.org/api/projects/17/?format=json","name":"GNU Compiler Collection","link_name":"gcc","list_id":"gcc-patches.gcc.gnu.org","list_email":"gcc-patches@gcc.gnu.org","web_url":null,"scm_url":null,"webscm_url":null,"list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20260422073435.140670-1-tkaminsk@redhat.com>","list_archive_url":null,"date":"2026-04-22T07:33:55","name":"libstdc++: Accept data_handle_type by value in mdspan deduction guide.","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"4b97acf65cf37809d91d6a96d4c3cc4d3ac9d3c5","submitter":{"id":90409,"url":"http://patchwork.ozlabs.org/api/people/90409/?format=json","name":"Tomasz Kaminski","email":"tkaminsk@redhat.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/gcc/patch/20260422073435.140670-1-tkaminsk@redhat.com/mbox/","series":[{"id":500934,"url":"http://patchwork.ozlabs.org/api/series/500934/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/list/?series=500934","date":"2026-04-22T07:33:55","name":"libstdc++: Accept data_handle_type by value in mdspan deduction guide.","version":1,"mbox":"http://patchwork.ozlabs.org/series/500934/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2226068/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2226068/checks/","tags":{},"related":[],"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=c31G9aP+;\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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charset=\"US-ASCII\"; x-default=true","X-BeenThere":"gcc-patches@gcc.gnu.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Gcc-patches mailing list ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org"},"content":"This makes the deduction guide accepting data_handle_type, mapping\nand accessor consistent with corresponding constructor.\nResolves LWG4511.\n\nlibstdc++-v3/ChangeLog:\n\n\t* include/std/mdspan (mdspan): Remove reference from\n\t_AccessorType::data_handle_type parameteter of deduction\n\tguide.\n\t* testsuite/23_containers/mdspan/mdspan.cc: New test.\n---\nTesting on x86_64-linux locally. All *mdspan* test passed in C++23,C++26\nmode and with modules. OK for trunk when all test passes?\n\n libstdc++-v3/include/std/mdspan | 4 +++-\n .../testsuite/23_containers/mdspan/mdspan.cc | 19 +++++++++++++++++++\n 2 files changed, 22 insertions(+), 1 deletion(-)","diff":"diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan\nindex f30c5e83d16..fae4ce0baa2 100644\n--- a/libstdc++-v3/include/std/mdspan\n+++ b/libstdc++-v3/include/std/mdspan\n@@ -3267,8 +3267,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION\n -> mdspan<_ElementType, typename _MappingType::extents_type,\n \t typename _MappingType::layout_type>;\n \n+ // _GLIBCXX_RESOLVE_LIB_DEFECTS\n+ // 4511. Inconsistency between the deduction guide of std::mdspan taking...\n template\n- mdspan(const typename _AccessorType::data_handle_type&, const _MappingType&,\n+ mdspan(typename _AccessorType::data_handle_type, const _MappingType&,\n \t const _AccessorType&)\n -> mdspan\n return true;\n }\n \n+void\n+test_from_volatile_ptr_and_accessor()\n+{\n+ constexpr size_t n = 3*5*7;\n+ std::array storage{};\n+ double* volatile vptr = storage.data();\n+ using Extents = std::extents;\n+\n+ auto exts = Extents{};\n+ auto m = std::layout_left::mapping(exts);\n+ auto a = std::default_accessor{};\n+ auto md = std::mdspan(vptr, m, a);\n+\n+ assert_deduced_typedefs(md);\n+ VERIFY(md.data_handle() == storage.data());\n+ VERIFY(md.mapping() == m);\n+}\n+\n template\n class OpaqueAccessor\n@@ -757,6 +775,7 @@ main()\n test_from_int_like();\n test_from_int_like();\n \n+ test_from_volatile_ptr_and_accessor();\n test_from_opaque_accessor();\n test_from_base_class_accessor();\n test_from_mapping_like();\n","prefixes":[]}