{"id":2226708,"url":"http://patchwork.ozlabs.org/api/patches/2226708/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/bmm.hhuoj2uk6c.gcc.gcc-TEST.ppalka.57.1.4@forge-stage.sourceware.org/","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":"","list_archive_url":null,"date":"2026-04-22T18:27:28","name":"[v1,4/8] libstdc++: Directly implement ranges::stable_sort [PR100795]","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"90bc113c25281ff4bfb68d775f090acd7b69894f","submitter":{"id":93215,"url":"http://patchwork.ozlabs.org/api/people/93215/?format=json","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.57.1.4@forge-stage.sourceware.org/mbox/","series":[{"id":501079,"url":"http://patchwork.ozlabs.org/api/series/501079/?format=json","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/2226708/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2226708/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 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; dmarc=none (p=none dis=none)\n header.from=forge-stage.sourceware.org","sourceware.org;\n spf=pass smtp.mailfrom=forge-stage.sourceware.org","server2.sourceware.org;\n arc=none smtp.remote-ip=38.145.34.39"],"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 4g17Rq5s5Yz1yGs\n\tfor ; Thu, 23 Apr 2026 04:44:23 +1000 (AEST)","from vm01.sourceware.org (localhost [127.0.0.1])\n\tby sourceware.org (Postfix) with ESMTP id CD2A2453E3FA\n\tfor ; Wed, 22 Apr 2026 18:44:21 +0000 (GMT)","from forge-stage.sourceware.org (vm08.sourceware.org [38.145.34.39])\n by sourceware.org (Postfix) with ESMTPS id 4B5584B7A1FD\n for ; Wed, 22 Apr 2026 18:28:35 +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 205E84349E\n for ; Wed, 22 Apr 2026 18:28:35 +0000 (UTC)"],"DKIM-Filter":["OpenDKIM Filter v2.11.0 sourceware.org CD2A2453E3FA","OpenDKIM Filter v2.11.0 sourceware.org 4B5584B7A1FD"],"DMARC-Filter":"OpenDMARC Filter v1.4.2 sourceware.org 4B5584B7A1FD","ARC-Filter":"OpenARC Filter v1.0.0 sourceware.org 4B5584B7A1FD","ARC-Seal":"i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1776882515; cv=none;\n b=oEgXtjaB7lsf1x+h/xJtBfHdANiXfbyoPJK2/h02pCv4f0ogE8qw8be3kjLIA5iFmaE+4D0l8GOBrqncmYBvM6+WqgjblRPElZbVr63bWcv66jUwUvj+g3D6TrkkI1We0QaMj5rxwHFXHJEzAyUdMP+xufNdD3c3TRPlhL1Fpp0=","ARC-Message-Signature":"i=1; a=rsa-sha256; d=sourceware.org; s=key;\n t=1776882515; c=relaxed/simple;\n bh=8SKV0VRtagR9j5ipzIqS7gdhNahG/Js57X0RPNC61Is=;\n h=From:Date:Subject:To:Message-ID;\n b=CGtFHvWrXISphAq3vdrzhf3qBAAimRtySvBSu6cizB6oann5TrqN4vRwLvYZazQTKAsZ1J54h75zHw2C3KeY3SD7sGFzbQo5JElX+2ZcLrf2JH3/XUfud5uY9GLLK0o3bjnPrbFuhhYx6Q5GL2xqsh6i+0egzYoqpxvGeqrqhgc=","ARC-Authentication-Results":"i=1; server2.sourceware.org","From":"ppalka via Sourceware Forge\n ","Date":"Wed, 22 Apr 2026 18:27:28 +0000","Subject":"[PATCH v1 4/8] libstdc++: Directly implement ranges::stable_sort\n [PR100795]","To":"gcc-patches mailing list ","Message-ID":"\n ","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 ","In-Reply-To":"\n ","X-Patch-URL":"\n https://forge.sourceware.org/gcc/gcc-TEST/commit/d9f1bb26d38541337f0f6c3bb7eba211dbca00a8","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 ","Reply-To":"gcc-patches mailing list ,\n ppalka@gcc.gnu.org","Errors-To":"gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org"},"content":"From: Patrick Palka \n\n\tPR libstdc++/100795\n\nlibstdc++-v3/ChangeLog:\n\n\t* include/bits/ranges_algo.h (__detail::__move_merge): New,\n\tbased on the stl_algo.h implementation.\n\t(__detail::__merge_sort_loop): Likewise.\n\t(__detail::__chunk_insertion_sort): Likewise.\n\t(__detail::__merge_sort_with_buffer): Likewise.\n\t(__detail::__stable_sort_adaptive): Likewise.\n\t(__detail::__stable_sort_adaptive_resize): Likewise.\n\t(__detail::__inplace_stable_sort): Likewise.\n\t(__stable_sort_fn::operator()): Reimplement in terms of the above.\n\t* testsuite/25_algorithms/stable_sort/constrained.cc:\n---\n libstdc++-v3/include/bits/ranges_algo.h | 207 +++++++++++++++++-\n .../25_algorithms/stable_sort/constrained.cc | 30 +++\n 2 files changed, 233 insertions(+), 4 deletions(-)","diff":"diff --git a/libstdc++-v3/include/bits/ranges_algo.h b/libstdc++-v3/include/bits/ranges_algo.h\nindex b0357600adbc..7dfd4e7ed64c 100644\n--- a/libstdc++-v3/include/bits/ranges_algo.h\n+++ b/libstdc++-v3/include/bits/ranges_algo.h\n@@ -2388,6 +2388,170 @@ namespace ranges\n \n inline constexpr __sort_fn sort{};\n \n+ namespace __detail\n+ {\n+ /// This is a helper function for the __merge_sort_loop routines.\n+ template\n+ _Out\n+ __move_merge(_Iter __first1, _Iter __last1,\n+\t\t _Iter __first2, _Iter __last2,\n+\t\t _Out __result, _Comp __comp)\n+ {\n+\twhile (__first1 != __last1 && __first2 != __last2)\n+\t {\n+\t if (__comp(*__first2, *__first1))\n+\t {\n+\t\t*__result = ranges::iter_move(__first2);\n+\t\t++__first2;\n+\t }\n+\t else\n+\t {\n+\t\t*__result = ranges::iter_move(__first1);\n+\t\t++__first1;\n+\t }\n+\t ++__result;\n+\t }\n+\treturn ranges::move(__first2, __last2,\n+\t\t\t ranges::move(__first1, __last1, __result).out).out;\n+ }\n+\n+ template\n+ void\n+ __merge_sort_loop(_Iter __first, _Iter __last, _Out __result,\n+\t\t\t_Distance __step_size, _Comp __comp)\n+ {\n+\tconst _Distance __two_step = 2 * __step_size;\n+\n+\twhile (__last - __first >= __two_step)\n+\t {\n+\t __result = __detail::__move_merge(__first, __first + __step_size,\n+\t\t\t\t\t __first + __step_size,\n+\t\t\t\t\t __first + __two_step,\n+\t\t\t\t\t __result, __comp);\n+\t __first += __two_step;\n+\t }\n+\t__step_size = ranges::min(_Distance(__last - __first), __step_size);\n+\n+\t__detail::__move_merge(__first, __first + __step_size,\n+\t\t\t __first + __step_size, __last, __result, __comp);\n+ }\n+\n+ template\n+ constexpr void\n+ __chunk_insertion_sort(_Iter __first, _Iter __last,\n+\t\t\t _Distance __chunk_size, _Compare __comp)\n+ {\n+\twhile (__last - __first >= __chunk_size)\n+\t {\n+\t __detail::__insertion_sort(__first, __first + __chunk_size, __comp);\n+\t __first += __chunk_size;\n+\t }\n+\t__detail::__insertion_sort(__first, __last, __comp);\n+ }\n+\n+ template\n+ void\n+ __merge_sort_with_buffer(_Iter __first, _Iter __last,\n+\t\t\t _Pointer __buffer, _Comp __comp)\n+ {\n+\tusing _Distance = iter_difference_t<_Iter>;\n+\n+\tconst _Distance __len = __last - __first;\n+\tconst _Pointer __buffer_last = __buffer + ptrdiff_t(__len);\n+\n+\tconstexpr int __chunk_size = 7;\n+\t_Distance __step_size = __chunk_size;\n+\t__detail::__chunk_insertion_sort(__first, __last, __step_size, __comp);\n+\n+\twhile (__step_size < __len)\n+\t {\n+\t __detail::__merge_sort_loop(__first, __last, __buffer,\n+\t\t\t\t\t__step_size, __comp);\n+\t __step_size *= 2;\n+\t __detail::__merge_sort_loop(__buffer, __buffer_last, __first,\n+\t\t\t\t\tptrdiff_t(__step_size), __comp);\n+\t __step_size *= 2;\n+\t }\n+ }\n+\n+ template\n+ void\n+ __merge_adaptive(_Iter __first, _Iter __middle, _Iter __last,\n+\t\t iter_difference_t<_Iter> __len1,\n+\t\t iter_difference_t<_Iter> __len2,\n+\t\t _Pointer __buffer, _Comp __comp); // defined near inplace_merge\n+\n+ template\n+ void\n+ __merge_adaptive_resize(_Iter __first, _Iter __middle, _Iter __last,\n+\t\t\t _Distance __len1, _Distance __len2,\n+\t\t\t _Pointer __buffer, _Distance __buffer_size,\n+\t\t\t _Comp __comp); // defined near inplace_merge\n+\n+ template\n+ constexpr void\n+ __merge_without_buffer(_Iter __first, _Iter __middle, _Iter __last,\n+\t\t\t _Distance __len1, _Distance __len2,\n+\t\t\t _Comp __comp); // defined near inplace_merge\n+\n+ template\n+ void\n+ __stable_sort_adaptive(_Iter __first, _Iter __middle, _Iter __last,\n+\t\t\t _Pointer __buffer, _Comp __comp)\n+ {\n+\t__detail::__merge_sort_with_buffer(__first, __middle, __buffer, __comp);\n+\t__detail::__merge_sort_with_buffer(__middle, __last, __buffer, __comp);\n+\n+\t__detail::__merge_adaptive(__first, __middle, __last,\n+\t\t\t\t __middle - __first, __last - __middle,\n+\t\t\t\t __buffer, __comp);\n+ }\n+\n+ template\n+ void\n+ __stable_sort_adaptive_resize(_Iter __first, _Iter __last,\n+\t\t\t\t _Pointer __buffer, _Distance __buffer_size,\n+\t\t\t\t _Comp __comp)\n+ {\n+\tconst _Distance __len = (__last - __first + 1) / 2;\n+\tconst _Iter __middle = __first + __len;\n+\tif (__len > __buffer_size)\n+\t {\n+\t __detail::__stable_sort_adaptive_resize(__first, __middle, __buffer,\n+\t\t\t\t\t\t __buffer_size, __comp);\n+\t __detail::__stable_sort_adaptive_resize(__middle, __last, __buffer,\n+\t\t\t\t\t\t __buffer_size, __comp);\n+\t __detail::__merge_adaptive_resize(__first, __middle, __last,\n+\t\t\t\t\t _Distance(__middle - __first),\n+\t\t\t\t\t _Distance(__last - __middle),\n+\t\t\t\t\t __buffer, __buffer_size,\n+\t\t\t\t\t __comp);\n+\t }\n+\telse\n+\t __detail::__stable_sort_adaptive(__first, __middle, __last,\n+\t\t\t\t\t __buffer, __comp);\n+ }\n+\n+ template\n+ _GLIBCXX26_CONSTEXPR\n+ void\n+ __inplace_stable_sort(_Iter __first, _Iter __last, _Comp __comp)\n+ {\n+\tif (__last - __first < 15)\n+\t {\n+\t __detail::__insertion_sort(__first, __last, __comp);\n+\t return;\n+\t }\n+\t_Iter __middle = __first + (__last - __first) / 2;\n+\t__detail::__inplace_stable_sort(__first, __middle, __comp);\n+\t__detail::__inplace_stable_sort(__middle, __last, __comp);\n+\t__detail::__merge_without_buffer(__first, __middle, __last,\n+\t\t\t\t\t __middle - __first,\n+\t\t\t\t\t __last - __middle,\n+\t\t\t\t\t __comp);\n+ }\n+ } // namespace __detail\n+\n struct __stable_sort_fn\n {\n template _Sent,\n@@ -2398,10 +2562,45 @@ namespace ranges\n operator()(_Iter __first, _Sent __last,\n \t\t _Comp __comp = {}, _Proj __proj = {}) const\n {\n-\tauto __lasti = ranges::next(__first, __last);\n-\tstd::stable_sort(std::move(__first), __lasti,\n-\t\t\t __detail::__make_comp_proj(__comp, __proj));\n-\treturn __lasti;\n+\tif constexpr (!same_as<_Iter, _Sent>)\n+\t return (*this)(__first, ranges::next(__first, __last),\n+\t\t\t std::move(__comp), std::move(__proj));\n+\telse\n+\t {\n+\t using _DistanceType = iter_difference_t<_Iter>;\n+\n+\t if (__first == __last)\n+\t return __last;\n+\n+#if _GLIBCXX_HOSTED\n+# if __glibcxx_constexpr_algorithms >= 202306L // >= C++26\n+\t if consteval {\n+\t __detail::__inplace_stable_sort(__first, __last, __comp);\n+\t return __last;\n+\t }\n+# endif\n+\n+\t typedef _Temporary_buffer<_Iter, iter_value_t<_Iter>> _TmpBuf;\n+\t // __stable_sort_adaptive sorts the range in two halves,\n+\t // so the buffer only needs to fit half the range at once.\n+\t _TmpBuf __buf(__first, ptrdiff_t((__last - __first + 1) / 2));\n+\n+\t auto __comp_proj = __detail::__make_comp_proj(__comp, __proj);\n+\t if (__buf._M_requested_size() == __buf.size()) [[likely]]\n+\t __detail::__stable_sort_adaptive(__first,\n+\t\t\t\t\t __first + _DistanceType(__buf.size()),\n+\t\t\t\t\t __last, __buf.begin(), __comp_proj);\n+\t else if (__buf.begin()) [[unlikely]]\n+\t __detail::__inplace_stable_sort(__first, __last, __comp_proj);\n+\t else\n+\t __detail::__stable_sort_adaptive_resize(__first, __last, __buf.begin(),\n+\t\t\t\t\t\t _DistanceType(__buf.size()),\n+\t\t\t\t\t\t __comp_proj);\n+#else\n+\t __detail::__inplace_stable_sort(__first, __last, __comp_proj);\n+#endif\n+\t return __last;\n+\t }\n }\n \n template\n #include \n+#include \n #include \n #include \n #include \n@@ -62,8 +63,37 @@ test01()\n }\n }\n \n+void\n+test02()\n+{\n+ // PR libstdc++/100795 - ranges::stable_sort should not use std::stable_sort\n+ // directly\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+\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+ using cat = std::iterator_traits>::iterator_category;\n+ static_assert( std::same_as );\n+ static_assert( std::ranges::random_access_range );\n+\n+ ranges::stable_sort(w);\n+ VERIFY( ranges::equal(w, v) );\n+\n+ ranges::stable_sort(w, std::ranges::greater{});\n+ VERIFY( ranges::equal(w, v | std::views::reverse) );\n+\n+ ranges::stable_sort(w, std::ranges::greater{}, std::negate{});\n+ VERIFY( ranges::equal(w, v) );\n+}\n+\n int\n main()\n {\n test01();\n+ test02();\n }\n","prefixes":["v1","4/8"]}