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GET /api/patches/2226723/?format=api
{ "id": 2226723, "url": "http://patchwork.ozlabs.org/api/patches/2226723/?format=api", "web_url": "http://patchwork.ozlabs.org/project/gcc/patch/bmm.hhuoj2uk6c.gcc.gcc-TEST.ppalka.57.1.8@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.hhuoj2uk6c.gcc.gcc-TEST.ppalka.57.1.8@forge-stage.sourceware.org>", "list_archive_url": null, "date": "2026-04-22T18:27:32", "name": "[v1,8/8] libstdc++: Directly implement ranges::shuffle [PR100795]", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "66709b688e66e64124fff423aab9ea0808ff603e", "submitter": { "id": 93215, "url": "http://patchwork.ozlabs.org/api/people/93215/?format=api", "name": "ppalka via Sourceware Forge", "email": "forge-bot+ppalka@forge-stage.sourceware.org" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/gcc/patch/bmm.hhuoj2uk6c.gcc.gcc-TEST.ppalka.57.1.8@forge-stage.sourceware.org/mbox/", "series": [ { "id": 501079, "url": "http://patchwork.ozlabs.org/api/series/501079/?format=api", "web_url": "http://patchwork.ozlabs.org/project/gcc/list/?series=501079", "date": "2026-04-22T18:27:24", "name": "libstdc++: C++20 iterator awareness fixes for various Ranges algorithms [PR100795]", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/501079/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2226723/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2226723/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=2620:52:6:3111::32; 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Wed, 22 Apr 2026 18:28:37 +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 57E07434A3\n for <gcc-patches@gcc.gnu.org>; Wed, 22 Apr 2026 18:28:35 +0000 (UTC)" ], "DKIM-Filter": [ "OpenDKIM Filter v2.11.0 sourceware.org DDFE140A2C74", "OpenDKIM Filter v2.11.0 sourceware.org 8C96748FED96" ], "DMARC-Filter": "OpenDMARC Filter v1.4.2 sourceware.org 8C96748FED96", "ARC-Filter": "OpenARC Filter v1.0.0 sourceware.org 8C96748FED96", "ARC-Seal": "i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1776882517; cv=none;\n b=d5YBhsaBwkZuqYUXS5kxPzddD+gcCKwxTsKth3NtzukokC5ZB6Op93YMWiVBfcqcO8qDi8cnzCma4qT7/ljQB/HBceJ6cr1xhgUCk/e471PCJhv+XeBdBLVltfMYqJ1nhyfTkPxK8tptiwCK6RrA7KMRWPElNCk7Fy/yQ8J/J5k=", "ARC-Message-Signature": "i=1; a=rsa-sha256; d=sourceware.org; s=key;\n t=1776882517; c=relaxed/simple;\n bh=tsU7zPesNWpEEqdIF/bcPclx4XA1cLwPbnPXKfdP9O0=;\n h=From:Date:Subject:To:Message-ID;\n b=g3MmUNTWRDqJQrAQk3IEXoCLybT0/fDr9RjRf2dIgP1XLB4uUCyvVnuOWPJgtAShLWygphmrQyE9xNva40kKvBzk+7GAY0ACN8BFwHELvdzEfkT9J7xxM9s6ANJ7csVWMBNFn5fYthvmrKLiRBydXdyJGexCwBul//X0DL4AIKs=", "ARC-Authentication-Results": "i=1; server2.sourceware.org", "From": "ppalka via Sourceware Forge\n <forge-bot+ppalka@forge-stage.sourceware.org>", "Date": "Wed, 22 Apr 2026 18:27:32 +0000", "Subject": "[PATCH v1 8/8] libstdc++: Directly implement ranges::shuffle\n [PR100795]", "To": "gcc-patches mailing list <gcc-patches@gcc.gnu.org>", "Message-ID": "\n <bmm.hhuoj2uk6c.gcc.gcc-TEST.ppalka.57.1.8@forge-stage.sourceware.org>", "X-Mailer": "batrachomyomachia", "X-Pull-Request-Organization": "gcc", "X-Pull-Request-Repository": "gcc-TEST", "X-Pull-Request": "https://forge.sourceware.org/gcc/gcc-TEST/pulls/57", "References": "\n <bmm.hhuoj2uk6c.gcc.gcc-TEST.ppalka.57.1.0@forge-stage.sourceware.org>", "In-Reply-To": "\n <bmm.hhuoj2uk6c.gcc.gcc-TEST.ppalka.57.1.0@forge-stage.sourceware.org>", "X-Patch-URL": "\n https://forge.sourceware.org/gcc/gcc-TEST/commit/a3c5a8afc73bbf2a4e4ae14cb51119c92fc1340d", "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 ppalka@gcc.gnu.org", "Errors-To": "gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org" }, "content": "From: Patrick Palka <ppalka@redhat.com>\n\n\tPR libstdc++/100795\n\nlibstdc++-v3/ChangeLog:\n\n\t* include/bits/ranges_algo.h (shuffle_fn::operator()):\n\tReimplement directly.\n\t* testsuite/25_algorithms/shuffle/constrained.cc (test02):\n---\n libstdc++-v3/include/bits/ranges_algo.h | 58 ++++++++++++++++++-\n .../25_algorithms/shuffle/constrained.cc | 25 ++++++++\n 2 files changed, 80 insertions(+), 3 deletions(-)", "diff": "diff --git a/libstdc++-v3/include/bits/ranges_algo.h b/libstdc++-v3/include/bits/ranges_algo.h\nindex 672a0ebce0de..83eaa7da28b9 100644\n--- a/libstdc++-v3/include/bits/ranges_algo.h\n+++ b/libstdc++-v3/include/bits/ranges_algo.h\n@@ -1952,9 +1952,61 @@ namespace ranges\n _Iter\n operator()(_Iter __first, _Sent __last, _Gen&& __g) const\n {\n-\tauto __lasti = ranges::next(__first, __last);\n-\tstd::shuffle(std::move(__first), __lasti, std::forward<_Gen>(__g));\n-\treturn __lasti;\n+\t// FIXME: Correctly handle integer-class difference types.\n+\tif (__first == __last)\n+\t return __first;\n+\n+\tusing _DistanceType = iter_difference_t<_Iter>;\n+\tusing __ud_type = __detail::__make_unsigned_like_t<_DistanceType>;\n+\tusing __distr_type = std::uniform_int_distribution<__ud_type>;\n+\tusing __p_type = typename __distr_type::param_type;\n+\n+\tusing __uc_type\n+\t = common_type_t<typename remove_reference_t<_Gen>::result_type, __ud_type>;\n+\n+\tconst __uc_type __urngrange = __g.max() - __g.min();\n+\tconst __uc_type __urange = __uc_type(__last - __first);\n+\n+\tif (__urngrange / __urange >= __urange)\n+\t // I.e. (__urngrange >= __urange * __urange) but without wrap issues.\n+\t {\n+\t _Iter __i = __first + 1;\n+\n+\t // Since we know the range isn't empty, an even number of elements\n+\t // means an uneven number of elements /to swap/, in which case we\n+\t // do the first one up front:\n+\n+\t if ((__urange % 2) == 0)\n+\t {\n+\t\t__distr_type __d{0, 1};\n+\t\tranges::iter_swap(__i++, __first + __d(__g));\n+\t }\n+\n+\t // Now we know that __last - __i is even, so we do the rest in pairs,\n+\t // using a single distribution invocation to produce swap positions\n+\t // for two successive elements at a time:\n+\n+\t while (__i != __last)\n+\t {\n+\t\tconst __uc_type __swap_range = __uc_type(__i - __first) + 1;\n+\n+\t\tconst pair<__uc_type, __uc_type> __pospos =\n+\t\t __gen_two_uniform_ints(__swap_range, __swap_range + 1, __g);\n+\n+\t\tranges::iter_swap(__i++, __first + __pospos.first);\n+\t\tranges::iter_swap(__i++, __first + __pospos.second);\n+\t }\n+\n+\t return __i;\n+\t }\n+\n+\t__distr_type __d;\n+\n+\t_Iter __i = __first + 1;\n+\tfor (; __i != __last; ++__i)\n+\t ranges::iter_swap(__i, __first + __d(__g, __p_type(0, __i - __first)));\n+\n+\treturn __i;\n }\n \n template<random_access_range _Range, typename _Gen>\ndiff --git a/libstdc++-v3/testsuite/25_algorithms/shuffle/constrained.cc b/libstdc++-v3/testsuite/25_algorithms/shuffle/constrained.cc\nindex d0977a292fee..70c6bdfc3d9e 100644\n--- a/libstdc++-v3/testsuite/25_algorithms/shuffle/constrained.cc\n+++ b/libstdc++-v3/testsuite/25_algorithms/shuffle/constrained.cc\n@@ -20,6 +20,7 @@\n \n #include <algorithm>\n #include <random>\n+#include <ranges>\n #include <vector>\n #include <testsuite_hooks.h>\n #include <testsuite_iterators.h>\n@@ -62,8 +63,32 @@ test01()\n }\n }\n \n+void\n+test02()\n+{\n+ // PR libstdc++/100795 - ranges::shuffle should not use std::shuffle directly\n+#if 0 // FIXME: ranges::shuffle rejects integer-class difference types.\n+#if __SIZEOF_INT128__\n+ auto v = std::views::iota(__int128(0), __int128(20));\n+#else\n+ auto v = std::views::iota(0ll, 20ll);\n+#endif\n+#else\n+ auto v = std::views::iota(0, 20);\n+#endif\n+\n+ int storage[20] = {2,5,4,3,1,6,7,9,10,8,11,14,12,13,15,16,18,0,19,17};\n+ auto w = v | std::views::transform([&](auto i) -> int& { return storage[i]; });\n+ using type = decltype(w);\n+ static_assert( std::ranges::random_access_range<type> );\n+\n+ std::ranlux48_base g;\n+ ranges::shuffle(w, g);\n+}\n+\n int\n main()\n {\n test01();\n+ test02();\n }\n", "prefixes": [ "v1", "8/8" ] }