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GET /api/patches/2226669/?format=api
{ "id": 2226669, "url": "http://patchwork.ozlabs.org/api/patches/2226669/?format=api", "web_url": "http://patchwork.ozlabs.org/project/gcc/patch/bmm.hhuo2dtkd4.gcc.gcc-TEST.peppe.44.1.2@forge-stage.sourceware.org/", "project": { "id": 17, "url": "http://patchwork.ozlabs.org/api/projects/17/?format=api", "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": "<bmm.hhuo2dtkd4.gcc.gcc-TEST.peppe.44.1.2@forge-stage.sourceware.org>", "list_archive_url": null, "date": "2026-04-22T18:10:42", "name": "[v1,2/2] libstdc++: add constexpr stable_partition", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "7994b774cdcc3eba868905b59968fa613440abf9", "submitter": { "id": 93222, "url": "http://patchwork.ozlabs.org/api/people/93222/?format=api", "name": "peppe via Sourceware Forge", "email": "forge-bot+peppe@forge-stage.sourceware.org" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/gcc/patch/bmm.hhuo2dtkd4.gcc.gcc-TEST.peppe.44.1.2@forge-stage.sourceware.org/mbox/", "series": [ { "id": 501068, "url": "http://patchwork.ozlabs.org/api/series/501068/?format=api", "web_url": "http://patchwork.ozlabs.org/project/gcc/list/?series=501068", "date": "2026-04-22T18:10:42", "name": "WIP: more_constexpr_stable_algorithms", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/501068/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2226669/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2226669/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "<gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org>", "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 spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=38.145.34.32; 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Wed, 22 Apr 2026 18:11:37 +0000 (GMT)", "from forge-stage.sourceware.org (localhost [IPv6:::1])\n (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n key-exchange x25519 server-signature ECDSA (prime256v1) server-digest SHA256)\n (No client certificate requested)\n by forge-stage.sourceware.org (Postfix) with ESMTPS id 4FF974340C\n for <gcc-patches@gcc.gnu.org>; Wed, 22 Apr 2026 18:11:37 +0000 (UTC)" ], "DKIM-Filter": [ "OpenDKIM Filter v2.11.0 sourceware.org 84F834AA397D", "OpenDKIM Filter v2.11.0 sourceware.org 824524BBCDC5" ], "DMARC-Filter": "OpenDMARC Filter v1.4.2 sourceware.org 824524BBCDC5", "ARC-Filter": "OpenARC Filter v1.0.0 sourceware.org 824524BBCDC5", "ARC-Seal": "i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1776881497; cv=none;\n b=ExYnuEHEc2HXLkIvj0pjWy5ec6556iHbEa9kVV/HATd4new79kALN9hlVTzaaeHlC4Dw9fal0uHBnTzNec3cBmOYv+S+jxQyd9JkXWZUB8Raw9FgwZwzV6WGst2okHUxvsrBLyvn0Jeb6DoziX6ywmugbb414m3U+7T/jQv+A0Q=", "ARC-Message-Signature": "i=1; a=rsa-sha256; d=sourceware.org; s=key;\n t=1776881497; c=relaxed/simple;\n bh=BGit1KnNN0m6OLa/zjmOx4DnaHNcCahNyBYwCmisFF4=;\n h=From:Date:Subject:To:Message-ID;\n b=golhKrgIF2d0itFWLjAHcaMM+zaa0OTjPea7H+n09WMqFxRdzNT6cNdNcs4Ks6XbmOT2qoT0q/+GBIpTVZYDnumaDJ3MAHErX4r++3kYFV0NX2oU/Tv9D1m+GHreC0JGGmuipZnr5cDRcLwvmW+l/ZqPcNruOlEI73bmG7b2I+U=", "ARC-Authentication-Results": "i=1; server2.sourceware.org", "From": "peppe via Sourceware Forge <forge-bot+peppe@forge-stage.sourceware.org>", "Date": "Wed, 22 Apr 2026 18:10:42 +0000", "Subject": "[PATCH v1 2/2] libstdc++: add constexpr stable_partition", "To": "gcc-patches mailing list <gcc-patches@gcc.gnu.org>", "Message-ID": "\n <bmm.hhuo2dtkd4.gcc.gcc-TEST.peppe.44.1.2@forge-stage.sourceware.org>", "X-Mailer": "batrachomyomachia", "X-Requested-Reviewer": "redi", "X-Pull-Request-Organization": "gcc", "X-Pull-Request-Repository": "gcc-TEST", "X-Pull-Request": "https://forge.sourceware.org/gcc/gcc-TEST/pulls/44", "References": "\n <bmm.hhuo2dtkd4.gcc.gcc-TEST.peppe.44.1.0@forge-stage.sourceware.org>", "In-Reply-To": "\n <bmm.hhuo2dtkd4.gcc.gcc-TEST.peppe.44.1.0@forge-stage.sourceware.org>", "X-Patch-URL": "\n https://forge.sourceware.org/peppe/gcc-TEST/commit/bfb9835a6472095f7e80eb19c7074686efd4bc96", "X-BeenThere": "gcc-patches@gcc.gnu.org", "X-Mailman-Version": "2.1.30", "Precedence": "list", "List-Id": "Gcc-patches mailing list <gcc-patches.gcc.gnu.org>", "List-Unsubscribe": "<https://gcc.gnu.org/mailman/options/gcc-patches>,\n <mailto:gcc-patches-request@gcc.gnu.org?subject=unsubscribe>", "List-Archive": "<https://gcc.gnu.org/pipermail/gcc-patches/>", "List-Post": "<mailto:gcc-patches@gcc.gnu.org>", "List-Help": "<mailto:gcc-patches-request@gcc.gnu.org?subject=help>", "List-Subscribe": "<https://gcc.gnu.org/mailman/listinfo/gcc-patches>,\n <mailto:gcc-patches-request@gcc.gnu.org?subject=subscribe>", "Reply-To": "gcc-patches mailing list <gcc-patches@gcc.gnu.org>,\n peppe@noreply.localhost", "Errors-To": "gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org" }, "content": "From: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>\n\nThis completes the implementation of P2562R1 for C++26.\n\nUnlike the other constexpr algorithms of the same family,\nstable_partition does not have a constexpr-friendly version \"ready to\nuse\" during constant evaluation. In fact, it is not even available on\nfreestanding, because it always allocates a temporary memory buffer.\n\nThis commit implements the simplest possible strategy: during constant\nevaluation allocate a buffer of length 1 on the stack, and use that as\na working area.\n\nlibstdc++-v3/ChangeLog:\n\n\t* include/bits/algorithmfwd.h (stable_partition): Mark it\n\tas constexpr for C++26.\n\t* include/bits/ranges_algo.h (__stable_partition_fn): Likewise.\n\t* include/bits/stl_algo.h (stable_partition): Mark it as\n\tconstexpr for C++26; during constant evaluation use a new\n\tcodepath where a temporary buffer of 1 element is used.\n\t* testsuite/25_algorithms/headers/algorithm/synopsis.cc\n\t(stable_partition): Add constexpr.\n\t* testsuite/25_algorithms/stable_partition/constexpr.cc: New test.\n---\n libstdc++-v3/include/bits/algorithmfwd.h | 1 +\n libstdc++-v3/include/bits/ranges_algo.h | 2 +\n libstdc++-v3/include/bits/stl_algo.h | 21 ++++++++-\n .../headers/algorithm/synopsis.cc | 1 +\n .../stable_partition/constexpr.cc | 44 +++++++++++++++++++\n 5 files changed, 67 insertions(+), 2 deletions(-)\n create mode 100644 libstdc++-v3/testsuite/25_algorithms/stable_partition/constexpr.cc", "diff": "diff --git a/libstdc++-v3/include/bits/algorithmfwd.h b/libstdc++-v3/include/bits/algorithmfwd.h\nindex 05894b580028..a727b2783814 100644\n--- a/libstdc++-v3/include/bits/algorithmfwd.h\n+++ b/libstdc++-v3/include/bits/algorithmfwd.h\n@@ -649,6 +649,7 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)\n \n #if _GLIBCXX_HOSTED\n template<typename _BIter, typename _Predicate>\n+ _GLIBCXX26_CONSTEXPR\n _BIter\n stable_partition(_BIter, _BIter, _Predicate);\n #endif\ndiff --git a/libstdc++-v3/include/bits/ranges_algo.h b/libstdc++-v3/include/bits/ranges_algo.h\nindex 2814d90061cc..f36e7dd59911 100644\n--- a/libstdc++-v3/include/bits/ranges_algo.h\n+++ b/libstdc++-v3/include/bits/ranges_algo.h\n@@ -2389,6 +2389,7 @@ namespace ranges\n \t typename _Proj = identity,\n \t indirect_unary_predicate<projected<_Iter, _Proj>> _Pred>\n requires permutable<_Iter>\n+ _GLIBCXX26_CONSTEXPR\n subrange<_Iter>\n operator()(_Iter __first, _Sent __last,\n \t\t _Pred __pred, _Proj __proj = {}) const\n@@ -2404,6 +2405,7 @@ namespace ranges\n \t indirect_unary_predicate<projected<iterator_t<_Range>, _Proj>>\n \t _Pred>\n requires permutable<iterator_t<_Range>>\n+ _GLIBCXX26_CONSTEXPR\n borrowed_subrange_t<_Range>\n operator()(_Range&& __r, _Pred __pred, _Proj __proj = {}) const\n {\ndiff --git a/libstdc++-v3/include/bits/stl_algo.h b/libstdc++-v3/include/bits/stl_algo.h\nindex bb7dbfbd8e04..71ead103d2bf 100644\n--- a/libstdc++-v3/include/bits/stl_algo.h\n+++ b/libstdc++-v3/include/bits/stl_algo.h\n@@ -1447,6 +1447,7 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)\n /// move-assign an element onto itself.\n template<typename _ForwardIterator, typename _Pointer, typename _Predicate,\n \t typename _Distance>\n+ _GLIBCXX26_CONSTEXPR\n _ForwardIterator\n __stable_partition_adaptive(_ForwardIterator __first,\n \t\t\t\t_ForwardIterator __last,\n@@ -1507,6 +1508,7 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)\n }\n \n template<typename _ForwardIterator, typename _Predicate>\n+ _GLIBCXX26_CONSTEXPR\n _ForwardIterator\n __stable_partition(_ForwardIterator __first, _ForwardIterator __last,\n \t\t _Predicate __pred)\n@@ -1521,11 +1523,25 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)\n typedef typename iterator_traits<_ForwardIterator>::difference_type\n \t_DistanceType;\n \n+ const _DistanceType __len = std::distance(__first, __last);\n+\n+#if __glibcxx_constexpr_algorithms >= 202306L // >= C++26\n+ if consteval {\n+\t// Simulate a _Temporary_buffer of length 1:\n+\t_ValueType __buf = std::move(*__first);\n+\t*__first = std::move(__buf);\n+\treturn std::__stable_partition_adaptive(__first, __last, __pred,\n+\t\t\t\t\t\t__len,\n+\t\t\t\t\t\t&__buf,\n+\t\t\t\t\t\t_DistanceType(1));\n+ }\n+#endif\n+\n _Temporary_buffer<_ForwardIterator, _ValueType>\n-\t__buf(__first, std::distance(__first, __last));\n+\t__buf(__first, __len);\n return\n \tstd::__stable_partition_adaptive(__first, __last, __pred,\n-\t\t\t\t\t _DistanceType(__buf.requested_size()),\n+\t\t\t\t\t __len,\n \t\t\t\t\t __buf.begin(),\n \t\t\t\t\t _DistanceType(__buf.size()));\n }\n@@ -1548,6 +1564,7 @@ _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)\n * relative ordering after calling @p stable_partition().\n */\n template<typename _ForwardIterator, typename _Predicate>\n+ _GLIBCXX26_CONSTEXPR\n inline _ForwardIterator\n stable_partition(_ForwardIterator __first, _ForwardIterator __last,\n \t\t _Predicate __pred)\ndiff --git a/libstdc++-v3/testsuite/25_algorithms/headers/algorithm/synopsis.cc b/libstdc++-v3/testsuite/25_algorithms/headers/algorithm/synopsis.cc\nindex 8d5c1fb7ac73..072dd0781046 100644\n--- a/libstdc++-v3/testsuite/25_algorithms/headers/algorithm/synopsis.cc\n+++ b/libstdc++-v3/testsuite/25_algorithms/headers/algorithm/synopsis.cc\n@@ -349,6 +349,7 @@ namespace std\n partition(_BIter, _BIter, _Predicate);\n \n template<typename _BIter, typename _Predicate>\n+ _GLIBCXX26_CONSTEXPR\n _BIter\n stable_partition(_BIter, _BIter, _Predicate);\n \ndiff --git a/libstdc++-v3/testsuite/25_algorithms/stable_partition/constexpr.cc b/libstdc++-v3/testsuite/25_algorithms/stable_partition/constexpr.cc\nnew file mode 100644\nindex 000000000000..8decc93eb827\n--- /dev/null\n+++ b/libstdc++-v3/testsuite/25_algorithms/stable_partition/constexpr.cc\n@@ -0,0 +1,44 @@\n+// { dg-do compile { target c++26 } }\n+\n+#include <algorithm>\n+#include <array>\n+\n+constexpr auto\n+create_array()\n+{\n+ return std::to_array({0, 10, 1, 2, 3, 3, 4, -1, -2, -4, 5, 6});\n+}\n+\n+constexpr bool\n+test01()\n+{\n+ auto ar = create_array();\n+ auto pred = [](int i) { return i % 2 == 0; };\n+ std::stable_partition(ar.begin(), ar.end(), pred);\n+ return std::is_partitioned(ar.begin(), ar.end(), pred);\n+}\n+\n+static_assert(test01());\n+\n+constexpr bool\n+test02()\n+{\n+ auto ar = create_array();\n+ auto pred = [](int i) { return i % 2 == 0; };\n+ std::ranges::stable_partition(ar, pred);\n+ return std::ranges::is_partitioned(ar, pred);\n+}\n+\n+static_assert(test02());\n+\n+constexpr bool\n+test03()\n+{\n+ auto ar = create_array();\n+ auto pred = [](int i) { return i % 2 == 0; };\n+ auto proj = [](int i) { return i + 1; };\n+ std::ranges::stable_partition(ar, pred, proj);\n+ return std::ranges::is_partitioned(ar, pred, proj);\n+}\n+\n+static_assert(test03());\n", "prefixes": [ "v1", "2/2" ] }