{"id":2227817,"url":"http://patchwork.ozlabs.org/api/patches/2227817/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/20260424100453.1166034-1-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":"<20260424100453.1166034-1-tkaminsk@redhat.com>","list_archive_url":null,"date":"2026-04-24T10:04:02","name":"libstdc++: Constrain views::adjacent(_transform)?<0> to forward_ranges.","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"a79a60c06604752a40139fd52dacf95c6d54d711","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/20260424100453.1166034-1-tkaminsk@redhat.com/mbox/","series":[{"id":501335,"url":"http://patchwork.ozlabs.org/api/series/501335/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/list/?series=501335","date":"2026-04-24T10:04:02","name":"libstdc++: Constrain views::adjacent(_transform)?<0> to forward_ranges.","version":1,"mbox":"http://patchwork.ozlabs.org/series/501335/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2227817/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2227817/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=X6TfN03X;\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; helo=vm01.sourceware.org;\n envelope-from=gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org;\n receiver=patchwork.ozlabs.org)","sourceware.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=X6TfN03X","sourceware.org; dmarc=pass (p=quarantine dis=none)\n header.from=redhat.com","sourceware.org; spf=pass smtp.mailfrom=redhat.com","server2.sourceware.org;\n arc=none smtp.remote-ip=170.10.129.124"],"Received":["from vm01.sourceware.org (vm01.sourceware.org\n [IPv6:2620:52:6:3111::32])\n\t(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n\t key-exchange x25519 server-signature ECDSA (secp384r1) server-digest SHA384)\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4g27rw02tnz1yD5\n\tfor ; Fri, 24 Apr 2026 20:06:06 +1000 (AEST)","from vm01.sourceware.org (localhost [127.0.0.1])\n\tby sourceware.org (Postfix) with ESMTP id 742C64BB3BE1\n\tfor ; Fri, 24 Apr 2026 10:06:04 +0000 (GMT)","from us-smtp-delivery-124.mimecast.com\n (us-smtp-delivery-124.mimecast.com [170.10.129.124])\n by sourceware.org (Postfix) with ESMTP id 959524BB3B96\n for ; Fri, 24 Apr 2026 10:05:01 +0000 (GMT)","from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com\n (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by\n relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3,\n cipher=TLS_AES_256_GCM_SHA384) id us-mta-377-gPw7UrFWM66q20q6Y330pw-1; Fri,\n 24 Apr 2026 06:04:56 -0400","from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com\n (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17])\n (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest\n SHA256)\n (No client certificate requested)\n by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS\n id A44EC18005A9; Fri, 24 Apr 2026 10:04:55 +0000 (UTC)","from localhost (unknown [10.44.48.150])\n by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP\n id ED4451944CED; Fri, 24 Apr 2026 10:04:54 +0000 (UTC)"],"DKIM-Filter":["OpenDKIM Filter v2.11.0 sourceware.org 742C64BB3BE1","OpenDKIM Filter v2.11.0 sourceware.org 959524BB3B96"],"DMARC-Filter":"OpenDMARC Filter v1.4.2 sourceware.org 959524BB3B96","ARC-Filter":"OpenARC Filter v1.0.0 sourceware.org 959524BB3B96","ARC-Seal":"i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1777025101; cv=none;\n b=r3QK3iu+WtJmbb3k/1/t33qS5rLVkmG55c/myhd4yuG/1QpKnTopuCFPWeVGGiRMg9xmvmPoxmBXESpvxzbZD1W0IHHROpE5+m9sHyzgurpIMPscmi6bhMBtcdYjprE6LMOHK/43m/2BpuF8vYMKxiqtAd3HRhNFwSiq/H8Mn/Y=","ARC-Message-Signature":"i=1; a=rsa-sha256; d=sourceware.org; s=key;\n t=1777025101; c=relaxed/simple;\n bh=TMnBWIgWrfkSCFYCTSJispv8c9468SWJf88SMu3ViSk=;\n h=DKIM-Signature:From:To:Subject:Date:Message-ID:MIME-Version;\n b=LjwOh8sla95UZHinDc9e9Ingz8nT+pglBgoSyMEF5RToot5VtPtTYXQ6ThaVHwneICI3If979oFbtJwMbwdm/j1NTW136gOHOH7eXOnFV34K+jvWll/HkiF1VvkBTtkq26fVlRCfTgeg968bmisldZdt1UpdPcBKUG+GyDS+A4M=","ARC-Authentication-Results":"i=1; server2.sourceware.org","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;\n s=mimecast20190719; t=1777025101;\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 bh=7EgeQG7P0+xIPGtTi8VZuiMzYm4lW9ejvyOt+UqTSAk=;\n b=X6TfN03X0jfUgsy9gIfLIcXJKOF9L2SuUilx0H0m00MWm+oGvxdTTfLZ27zmcJLzk+A8vD\n nieUMU8ND4PptIMPP8rA0wxaFWdybeBrjUoD/tprztlMGrXAsMwvuTssbE+oateT9zyO28\n 1XjUL0Hw9ndyPz8bsTWzv009PJruiF4=","X-MC-Unique":"gPw7UrFWM66q20q6Y330pw-1","X-Mimecast-MFC-AGG-ID":"gPw7UrFWM66q20q6Y330pw_1777025095","From":"=?utf-8?q?Tomasz_Kami=C5=84ski?= ","To":"libstdc++@gcc.gnu.org,\n\tgcc-patches@gcc.gnu.org","Subject":"[PATCH] libstdc++: Constrain views::adjacent(_transform)?<0> to\n forward_ranges.","Date":"Fri, 24 Apr 2026 12:04:02 +0200","Message-ID":"<20260424100453.1166034-1-tkaminsk@redhat.com>","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":"nw_R-yFtaXt-X90dceckiHN-NxMg8ikJh_8mRadgtpA_1777025095","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 resolves LWG 4098, \"views::adjacent<0> should reject non-forward ranges\"\nwhich was approved in Sofia 2024.\n\nlibstdc++-v3/ChangeLog:\n\n\t* include/std/ranges (_AdjacentTransform::operator())\n\t(_Adjacent::operator()): Require forward_range for N == 0.\n\t* testsuite/std/ranges/adaptors/adjacent/1.cc: Test if input_ranges\n\tare rejected.\n\t* testsuite/std/ranges/adaptors/adjacent_transform/1.cc: Likewise.\n---\nTesting on x86_64-linux. *adaptors/adjacent* test passed.\nOK for trunk when all tests passes?\n\n libstdc++-v3/include/std/ranges | 10 ++++++++--\n .../testsuite/std/ranges/adaptors/adjacent/1.cc | 7 +++++++\n .../std/ranges/adaptors/adjacent_transform/1.cc | 7 +++++++\n 3 files changed, 22 insertions(+), 2 deletions(-)","diff":"diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges\nindex 9c7d639a154..ba4c9f60ab2 100644\n--- a/libstdc++-v3/include/std/ranges\n+++ b/libstdc++-v3/include/std/ranges\n@@ -5859,8 +5859,11 @@ namespace views::__adaptor\n template\n struct _Adjacent : __adaptor::_RangeAdaptorClosure<_Adjacent<_Nm>>\n {\n+\t// _GLIBCXX_RESOLVE_LIB_DEFECTS\n+\t// 4098. views::adjacent<0> should reject non-forward ranges\n \ttemplate\n-\t requires (_Nm == 0) || __detail::__can_adjacent_view<_Nm, _Range>\n+\t requires (_Nm == 0) && forward_range<_Range>\n+\t\t || __detail::__can_adjacent_view<_Nm, _Range>\n \t constexpr auto\n \t operator() [[nodiscard]] (_Range&& __r) const\n \t {\n@@ -6197,8 +6200,11 @@ namespace views::__adaptor\n template\n struct _AdjacentTransform : __adaptor::_RangeAdaptor<_AdjacentTransform<_Nm>>\n {\n+\t// _GLIBCXX_RESOLVE_LIB_DEFECTS\n+\t// 4098. views::adjacent<0> should reject non-forward ranges\n \ttemplate\n-\t requires (_Nm == 0) || __detail::__can_adjacent_transform_view<_Nm, _Range, _Fp>\n+\t requires (_Nm == 0) && forward_range<_Range>\n+\t\t || __detail::__can_adjacent_transform_view<_Nm, _Range, _Fp>\n \t constexpr auto\n \t operator() [[nodiscard]] (_Range&& __r, _Fp&& __f) const\n \t {\ndiff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent/1.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent/1.cc\nindex 0a5c67f5614..57322922e5e 100644\n--- a/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent/1.cc\n+++ b/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent/1.cc\n@@ -9,6 +9,13 @@\n namespace ranges = std::ranges;\n namespace views = std::views;\n \n+template\n+concept can_adjacent0 = requires (Range& rg)\n+{ views::adjacent<0>(rg); };\n+\n+static_assert( !can_adjacent0<__gnu_test::test_input_range> );\n+static_assert( can_adjacent0<__gnu_test::test_forward_range> );\n+\n constexpr bool\n test01()\n {\ndiff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent_transform/1.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent_transform/1.cc\nindex 6890618754b..a75d02efbb8 100644\n--- a/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent_transform/1.cc\n+++ b/libstdc++-v3/testsuite/std/ranges/adaptors/adjacent_transform/1.cc\n@@ -9,6 +9,13 @@\n namespace ranges = std::ranges;\n namespace views = std::views;\n \n+template\n+concept can_adjacent0 = requires (Range& rg)\n+{ views::adjacent_transform<0>(rg, []() { return 10; }); };\n+\n+static_assert( !can_adjacent0<__gnu_test::test_input_range> );\n+static_assert( can_adjacent0<__gnu_test::test_forward_range> );\n+\n constexpr bool\n test01()\n {\n","prefixes":[]}