{"id":2227950,"url":"http://patchwork.ozlabs.org/api/patches/2227950/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/20260424152301.2386133-1-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":"<20260424152301.2386133-1-tkaminsk@redhat.com>","list_archive_url":null,"date":"2026-04-24T15:21:56","name":"[v2] libstdc++: Disallow duration of cv-qualified types and references.","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"c5edc409f75ae557180b3c9dad523fa1d64aea0a","submitter":{"id":90409,"url":"http://patchwork.ozlabs.org/api/people/90409/?format=json","name":"Tomasz Kamiński","email":"tkaminsk@redhat.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/gcc/patch/20260424152301.2386133-1-tkaminsk@redhat.com/mbox/","series":[{"id":501381,"url":"http://patchwork.ozlabs.org/api/series/501381/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/list/?series=501381","date":"2026-04-24T15:21:56","name":"[v2] libstdc++: Disallow duration of cv-qualified types and references.","version":2,"mbox":"http://patchwork.ozlabs.org/series/501381/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2227950/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2227950/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=Uq+bFeUm;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=2620:52:6:3111::32; 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a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;\n s=mimecast20190719; t=1777044187;\n h=from:from:reply-to:subject:subject:date:date:message-id:message-id:\n to:to:cc:mime-version:mime-version:content-type:content-type:\n content-transfer-encoding:content-transfer-encoding:\n in-reply-to:in-reply-to:references:references;\n bh=HDbNSVwmV3nAQNTTJMMXWo+gnYCdKG6xCS8roI6BoBs=;\n b=Uq+bFeUmBRVIcWqFRymFztGOXakqybSWlJeqhJSdwQUP+jWiSWm4YJa/QRDSHniA5GNO0E\n +6jnnaJ9vk0QSBYzkKlOMw8zr1xCTvbuhh6KDq8iA+mh1zFiWiqFjQpu4nIHD5SFKBUPt4\n kUB2DFk9UyVBLQBRl+N2cfeMr9dtDj8=","X-MC-Unique":"wDDNeg0OMuaEHRtlRsZ-PA-1","X-Mimecast-MFC-AGG-ID":"wDDNeg0OMuaEHRtlRsZ-PA_1777044183","From":"=?utf-8?q?Tomasz_Kami=C5=84ski?= ","To":"libstdc++@gcc.gnu.org,\n\tgcc-patches@gcc.gnu.org","Subject":"[PATCH v2] libstdc++: Disallow duration of cv-qualified types and\n references.","Date":"Fri, 24 Apr 2026 17:21:56 +0200","Message-ID":"<20260424152301.2386133-1-tkaminsk@redhat.com>","In-Reply-To":"\n ","References":"\n ","MIME-Version":"1.0","X-Scanned-By":"MIMEDefang 3.0 on 10.30.177.17","X-Mimecast-Spam-Score":"0","X-Mimecast-MFC-PROC-ID":"CKU68q3t6MDdK4GicCqKXe1LUPSueNYyqGzMxh3eXTo_1777044183","X-Mimecast-Originator":"redhat.com","Content-Transfer-Encoding":"8bit","content-type":"text/plain; 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 implements LWG 4481, \"Disallow chrono::duration\",\nwhich was approved in Croydon 2026.\n\nlibstdc++-v3/ChangeLog:\n\n\t* include/bits/chrono.h: Add static_assert requiring cv-unqualified\n\tnon-reference type.\n\t* testsuite/20_util/duration/io.cc: Remove const-qualifier in\n\tstream manipluators tests.\n\t* testsuite/20_util/duration/requirements/typedefs_neg4.cc:\n\tNew test.\n---\nv2 removes const from manipulators test instead of nuking them completly.\n\nTesting on x86_64-linux. *duration* test passed again.\nOK for trunk when all tests passes?\n\n libstdc++-v3/include/bits/chrono.h | 4 ++++\n libstdc++-v3/testsuite/20_util/duration/io.cc | 12 ++++++------\n .../20_util/duration/requirements/typedefs_neg4.cc | 11 +++++++++++\n 3 files changed, 21 insertions(+), 6 deletions(-)\n create mode 100644 libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg4.cc","diff":"diff --git a/libstdc++-v3/include/bits/chrono.h b/libstdc++-v3/include/bits/chrono.h\nindex fd91505c16f..d639cfaa485 100644\n--- a/libstdc++-v3/include/bits/chrono.h\n+++ b/libstdc++-v3/include/bits/chrono.h\n@@ -514,6 +514,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION\n template\n class duration\n {\n+\t// _GLIBCXX_RESOLVE_LIB_DEFECTS\n+\t// 4481. Disallow chrono::duration\n+\tstatic_assert(is_same<_Rep, __remove_cvref_t<_Rep>>::value,\n+\t\t \"rep should be cv-unqualified object type\");\n \tstatic_assert(!__is_duration<_Rep>::value,\n \t\t \"rep cannot be a std::chrono::duration\");\n \tstatic_assert(__is_ratio<_Period>::value,\ndiff --git a/libstdc++-v3/testsuite/20_util/duration/io.cc b/libstdc++-v3/testsuite/20_util/duration/io.cc\nindex 6ada4fcfa84..83ecd33c038 100644\n--- a/libstdc++-v3/testsuite/20_util/duration/io.cc\n+++ b/libstdc++-v3/testsuite/20_util/duration/io.cc\n@@ -40,10 +40,10 @@ test01()\n VERIFY( ss.str() == \"121s 122s 123s 124s 125s 126s 127s \" );\n \n ss.str(\"\");\n- ss << std::hex << std::uppercase << duration(0x1A) << ' ';\n- ss << std::hex << std::uppercase << duration(0x2A) << ' ';\n+ ss << std::hex << std::uppercase << duration(0x1A) << ' ';\n+ ss << std::hex << std::uppercase << duration(0x2A) << ' ';\n ss << std::hex << std::uppercase << duration(0x3A) << ' ';\n- ss << std::scientific << duration(4.5) << ' ';\n+ ss << std::scientific << duration(4.5) << ' ';\n VERIFY( ss.str() == \"1As 2As 3As 4.500000E+00s \" );\n }\n \n@@ -79,10 +79,10 @@ test02()\n VERIFY( ss.str() == L\"121s 122s 123s 124s 125s 126s 127s \" );\n \n ss.str(L\"\");\n- ss << std::hex << std::uppercase << duration(0x1A) << ' ';\n- ss << std::hex << std::uppercase << duration(0x2A) << ' ';\n+ ss << std::hex << std::uppercase << duration(0x1A) << ' ';\n+ ss << std::hex << std::uppercase << duration(0x2A) << ' ';\n ss << std::hex << std::uppercase << duration(0x3A) << ' ';\n- ss << std::scientific << duration(4.5) << ' ';\n+ ss << std::scientific << duration(4.5) << ' ';\n VERIFY( ss.str() == L\"1As 2As 3As 4.500000E+00s \" );\n #endif\n }\ndiff --git a/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg4.cc b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg4.cc\nnew file mode 100644\nindex 00000000000..52a5d92cc8b\n--- /dev/null\n+++ b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg4.cc\n@@ -0,0 +1,11 @@\n+// { dg-do compile { target c++11 } }\n+\n+#include \n+\n+const int i = 10;\n+// Check if rep is a cv-unqualifed object type\n+std::chrono::duration d1(i); // { dg-error \"required from here\" }\n+std::chrono::duration d2(i); // { dg-error \"required from here\" }\n+std::chrono::duration d3(i); // { dg-error \"required from here\" }\n+\n+// { dg-error \"rep should be cv-unqualified object type\" \"\" { target *-*-* } 0 }\n","prefixes":["v2"]}