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GET /api/patches/2226650/?format=api
{ "id": 2226650, "url": "http://patchwork.ozlabs.org/api/patches/2226650/?format=api", "web_url": "http://patchwork.ozlabs.org/project/gcc/patch/bmm.hhunqjrqt2.gcc.gcc-TEST.redi.37.1.1@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.hhunqjrqt2.gcc.gcc-TEST.redi.37.1.1@forge-stage.sourceware.org>", "list_archive_url": null, "date": "2026-04-22T17:58:46", "name": "[v1,1/1] libstdc++: Add missing static_assert to std::expected<void,E>::value()&&", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "6b6278bd4353cf2917d5a2f36582a9db65762e9c", "submitter": { "id": 93210, "url": "http://patchwork.ozlabs.org/api/people/93210/?format=api", "name": "Jonathan Wakely via Sourceware Forge", "email": "forge-bot+redi@forge-stage.sourceware.org" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/gcc/patch/bmm.hhunqjrqt2.gcc.gcc-TEST.redi.37.1.1@forge-stage.sourceware.org/mbox/", "series": [ { "id": 501058, "url": "http://patchwork.ozlabs.org/api/series/501058/?format=api", "web_url": "http://patchwork.ozlabs.org/project/gcc/list/?series=501058", "date": "2026-04-22T17:58:46", "name": "libstdc++: Add missing static_assert to std::expected<void,E>::value()&&", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/501058/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2226650/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2226650/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 17:59:37 +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 B5DB342BFF\n for <gcc-patches@gcc.gnu.org>; Wed, 22 Apr 2026 17:59:37 +0000 (UTC)" ], "DKIM-Filter": [ "OpenDKIM Filter v2.11.0 sourceware.org E8C3F4BB58F8", "OpenDKIM Filter v2.11.0 sourceware.org DDF754BB58F8" ], "DMARC-Filter": "OpenDMARC Filter v1.4.2 sourceware.org DDF754BB58F8", "ARC-Filter": "OpenARC Filter v1.0.0 sourceware.org DDF754BB58F8", "ARC-Seal": "i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1776880777; cv=none;\n b=RRWQDsgyJBTZY2Rj/FEnBuOcZv9fSQ/IGaVLU6wTyJUoPME275zEmlhcBoCvk3P/buBLuyoUXnF/tN5MGomuBDcVt4Kmf4ziMh8JwIFaBpRDyW7nSrPAD3Ibc8h3iBVY5eUp4wnv9Iwaf0NIvrPM0pxp+FU1ly9DP6cFSL5HNOk=", "ARC-Message-Signature": "i=1; a=rsa-sha256; d=sourceware.org; s=key;\n t=1776880777; c=relaxed/simple;\n bh=PolDstwKqkVPQ5fIKImSaofrh9ubvEPy0vkmn8kalwc=;\n h=From:Date:Subject:To:Message-ID;\n b=MHy78ydEDRBzUM3bCsrNCJdszoeu7J6NR2/FJtGejoBq010B9Q6H+o8C9fx0fFwEvPmrmZCJddsMvpAUH8ZRaTi3leFw+bkAhxGHkECHSNEP4/m19kopUOYu+xVh8eNo/DI4zqD7JWr0wJhGEvBVuTmYUTsi0gAxqBEASPS2UuQ=", "ARC-Authentication-Results": "i=1; server2.sourceware.org", "From": "Jonathan Wakely via Sourceware Forge\n <forge-bot+redi@forge-stage.sourceware.org>", "Date": "Wed, 22 Apr 2026 17:58:46 +0000", "Subject": "[PATCH v1 1/1] libstdc++: Add missing static_assert to\n std::expected<void,E>::value()&&", "To": "gcc-patches mailing list <gcc-patches@gcc.gnu.org>", "Message-ID": "\n <bmm.hhunqjrqt2.gcc.gcc-TEST.redi.37.1.1@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/37", "References": "\n <bmm.hhunqjrqt2.gcc.gcc-TEST.redi.37.1.0@forge-stage.sourceware.org>", "In-Reply-To": "\n <bmm.hhunqjrqt2.gcc.gcc-TEST.redi.37.1.0@forge-stage.sourceware.org>", "X-Patch-URL": "\n https://forge.sourceware.org/redi/gcc/commit/62b2ee5099bb3aa807112e827ea224427071a2b2", "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>, redi@gcc.gnu.org", "Errors-To": "gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org" }, "content": "From: Jonathan Wakely <jwakely@redhat.com>\n\nThe r15-2326-gea435261ad58ea change missed a static_assert for\nis_move_constructible_v in expected<cv void, E>::value()&&. When\nexceptions are enabled, the program is ill-formed if the error type is\nnot move constructible, because we can't construct the\nstd::bad_expected_access. But when using -fno-exceptions, we never\nconstruct an exception, so don't need to copy/move the error value. So\nthat the same code compiles with/without exceptions enabled, we should\nenforce the requirement explicitly.\n\nAdd the static_assert, and a test that verifies the Mandates:\nconditions added by LWG 3843 and 3490 are enforced even with\n-fno-exceptions.\n\nlibstdc++-v3/ChangeLog:\n\n\t* include/std/expected (expected<cv void,E>::value()&&):\n\tAdd missing static_assert for LWG 3940.\n\t* testsuite/20_util/expected/lwg3843.cc: New test.\n---\n libstdc++-v3/include/std/expected | 1 +\n .../testsuite/20_util/expected/lwg3843.cc | 69 +++++++++++++++++++\n 2 files changed, 70 insertions(+)\n create mode 100644 libstdc++-v3/testsuite/20_util/expected/lwg3843.cc", "diff": "diff --git a/libstdc++-v3/include/std/expected b/libstdc++-v3/include/std/expected\nindex 7de2aeffc70c..5dc1dfbe5b8a 100644\n--- a/libstdc++-v3/include/std/expected\n+++ b/libstdc++-v3/include/std/expected\n@@ -1541,6 +1541,7 @@ namespace __expected\n value() &&\n {\n \tstatic_assert( is_copy_constructible_v<_Er> );\n+\tstatic_assert( is_move_constructible_v<_Er> );\n \tif (_M_has_value) [[likely]]\n \t return;\n \t_GLIBCXX_THROW_OR_ABORT(bad_expected_access<_Er>(std::move(_M_unex)));\ndiff --git a/libstdc++-v3/testsuite/20_util/expected/lwg3843.cc b/libstdc++-v3/testsuite/20_util/expected/lwg3843.cc\nnew file mode 100644\nindex 000000000000..2afb9cc680bf\n--- /dev/null\n+++ b/libstdc++-v3/testsuite/20_util/expected/lwg3843.cc\n@@ -0,0 +1,69 @@\n+// { dg-do compile { target c++23 } }\n+// { dg-options \"-fno-exceptions\" }\n+\n+#include <expected>\n+\n+// 3843. std::expected<T,E>::value() & assumes E is copy constructible\n+void\n+test_lwg3843()\n+{\n+ struct E1 {\n+ E1(int) { }\n+ E1(E1&) { }\n+ E1(const E1&) = delete;\n+ };\n+ std::expected<int, E1> v1;\n+ v1.value(); // { dg-error \"here\" }\n+ const auto& v1c = v1;\n+ v1c.value(); // { dg-error \"here\" }\n+\n+ struct E2 {\n+ E2(int) { }\n+ E2(const E2&) { }\n+ E2(E2&&) = delete;\n+ };\n+ std::expected<int, E2> v2;\n+ v2.value();\n+ std::move(v2).value(); // { dg-error \"here\" }\n+ const auto& v2c = v2;\n+ v2c.value();\n+ std::move(v2c).value();\n+\n+ struct E3 {\n+ E3(int) { }\n+ E3(const E3&) { }\n+ E3(E3&&) { }\n+ E3(const E3&&) = delete;\n+ };\n+ std::expected<int, E3> v3;\n+ v3.value();\n+ std::move(v3).value();\n+ const auto& v3c = v3;\n+ v3c.value();\n+ std::move(v3c).value(); // { dg-error \"here\" }\n+}\n+\n+// 3940. std::expected<void, E>::value() also needs E to be copy constructible\n+void\n+test_lwg3940()\n+{\n+ struct E1 {\n+ E1(int) { }\n+ E1(E1&) { }\n+ E1(const E1&) = delete;\n+ };\n+ std::expected<void, E1> v1;\n+ v1.value(); // { dg-error \"here\" }\n+\n+ struct E2 {\n+ E2(int) { }\n+ E2(const E2&) { }\n+ E2(E2&&) = delete;\n+ };\n+ std::expected<void, E2> v2;\n+ std::move(v2).value(); // { dg-error \"here\" }\n+}\n+\n+// { dg-error \"static assertion failed\" \"\" { target *-*-* } 0 }\n+// { dg-prune-output \"use of deleted function\" }\n+// { dg-prune-output \"control reaches end of non-void function\" }\n", "prefixes": [ "v1", "1/1" ] }