{"id":2225355,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2225355/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/20260420212533.3862595-1-ppalka@redhat.com/","project":{"id":17,"url":"http://patchwork.ozlabs.org/api/1.1/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},"msgid":"<20260420212533.3862595-1-ppalka@redhat.com>","date":"2026-04-20T21:25:33","name":"libstdc++: Restrict engaged -> disengaged std::optional fix [PR124910]","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"9b569ca8aff01b9c7efb02f87de0a10648a0bda2","submitter":{"id":78319,"url":"http://patchwork.ozlabs.org/api/1.1/people/78319/?format=json","name":"Patrick Palka","email":"ppalka@redhat.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/gcc/patch/20260420212533.3862595-1-ppalka@redhat.com/mbox/","series":[{"id":500686,"url":"http://patchwork.ozlabs.org/api/1.1/series/500686/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/list/?series=500686","date":"2026-04-20T21:25:33","name":"libstdc++: Restrict engaged -> disengaged std::optional fix [PR124910]","version":1,"mbox":"http://patchwork.ozlabs.org/series/500686/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2225355/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2225355/checks/","tags":{},"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=Tn3InJn8;\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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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":"Tested on x86_64-pc-linux-gnu, does this look OK for trunk?\n\n-- >8 --\n\nIt turns out a union without an active member does not violate C++20 core\nconstant expression rules and r16-8748 was really just a workaround for\na front end bug. The actual underlying problem -- that the constexpr\nevaluator treated an explicitly destroyed union member as still active\n-- has been fixed by r16-8767 which makes this workaround unnecessary\nfor GCC. Rather than remove the workaround, restrict it to Clang which\nseems to have a similar bug.\n\n\tPR c++/124910\n\nlibstdc++-v3/ChangeLog:\n\n\t* include/std/optional (_Optional_payload_base::_M_destroy):\n\tRestrict r16-8748 workaround to Clang, and adjust comment.\n---\n libstdc++-v3/include/std/optional | 5 ++---\n 1 file changed, 2 insertions(+), 3 deletions(-)","diff":"diff --git a/libstdc++-v3/include/std/optional b/libstdc++-v3/include/std/optional\nindex 49ba7b6b45dd..b9cc019feff7 100644\n--- a/libstdc++-v3/include/std/optional\n+++ b/libstdc++-v3/include/std/optional\n@@ -321,10 +321,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION\n {\n \t_M_engaged = false;\n \t_M_payload._M_value.~_Stored_type();\n-#if __cpp_lib_optional >= 202106L // full constexpr support\n+#if defined(__clang__) && __cpp_lib_optional >= 202106L // full constexpr support\n \tif (std::is_constant_evaluated())\n-\t // Ensure union _M_payload always has an active member, for sake\n-\t // of the core constant expression requirements.\n+\t // Work around PR124910 for Clang.\n \t std::construct_at(std::__addressof(_M_payload._M_empty));\n #endif\n }\n","prefixes":[]}