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GET /api/patches/2195376/?format=api
{ "id": 2195376, "url": "http://patchwork.ozlabs.org/api/patches/2195376/?format=api", "web_url": "http://patchwork.ozlabs.org/project/gcc/patch/20260210215430.1863636-1-ppalka@redhat.com/", "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": "<20260210215430.1863636-1-ppalka@redhat.com>", "list_archive_url": null, "date": "2026-02-10T21:54:30", "name": "libstdc++: Clear padding bits in std::atomic ctor in C++11 [PR114865]", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "faafb9a847a92942bcd9a2cd14e1743cd0707ce0", "submitter": { "id": 78319, "url": "http://patchwork.ozlabs.org/api/people/78319/?format=api", "name": "Patrick Palka", "email": "ppalka@redhat.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/gcc/patch/20260210215430.1863636-1-ppalka@redhat.com/mbox/", "series": [ { "id": 491743, "url": "http://patchwork.ozlabs.org/api/series/491743/?format=api", "web_url": "http://patchwork.ozlabs.org/project/gcc/list/?series=491743", "date": "2026-02-10T21:54:30", "name": "libstdc++: Clear padding bits in std::atomic ctor in C++11 [PR114865]", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/491743/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2195376/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2195376/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\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=F5ndSQnu;\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 <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>", "Errors-To": "gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org" }, "content": "Tested on x86_64-pc-linux-gnu with GLIBCXX_TESTSUITE_STDS=11,14,20,\ndoes this look OK for trunk and backports (after r16-7199 gets\nbackported)? Also tested with Clang 21.\n\n-- >8 --\n\nAfter the front end change r16-7199 both GCC and Clang allow\nnon-empty constexpr constructor bodies in C++11 as an extension,\nso we can unconditionally enable the __builtin_clear_padding logic\nin std::atomic's constructor.\n\n\tPR libstdc++/114865\n\nlibstdc++-v3/ChangeLog:\n\n\t* include/std/atomic (atomic<_Tp>::atomic(_Tp))\n\t[C++11]: Enable __builtin_clear_padding logic.\n\t* testsuite/29_atomics/atomic/cons/static_zero_padding.cc\n\t[C++11]: Enable test verifying cleared padding bits for a\n\tstd::atomic local variable.\n---\n libstdc++-v3/include/std/atomic | 5 ++++-\n .../testsuite/29_atomics/atomic/cons/static_zero_padding.cc | 2 --\n 2 files changed, 4 insertions(+), 3 deletions(-)", "diff": "diff --git a/libstdc++-v3/include/std/atomic b/libstdc++-v3/include/std/atomic\nindex 56dbe7bf5b95..306667e3c633 100644\n--- a/libstdc++-v3/include/std/atomic\n+++ b/libstdc++-v3/include/std/atomic\n@@ -247,14 +247,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION\n atomic& operator=(const atomic&) = delete;\n atomic& operator=(const atomic&) volatile = delete;\n \n+#pragma GCC diagnostic push\n+#pragma GCC diagnostic ignored \"-Wc++14-extensions\" // constexpr ctor body\n constexpr atomic(_Tp __i) noexcept : _M_i(__i)\n {\n-#if __cplusplus >= 201402L && __has_builtin(__builtin_clear_padding)\n+#if __has_builtin(__builtin_clear_padding)\n \tif _GLIBCXX17_CONSTEXPR (__atomic_impl::__maybe_has_padding<_Tp>())\n \t if (!std::__is_constant_evaluated())\n \t __builtin_clear_padding(std::__addressof(_M_i));\n #endif\n }\n+#pragma GCC diagnostic pop\n \n operator _Tp() const noexcept\n { return load(); }\ndiff --git a/libstdc++-v3/testsuite/29_atomics/atomic/cons/static_zero_padding.cc b/libstdc++-v3/testsuite/29_atomics/atomic/cons/static_zero_padding.cc\nindex 506513647c6c..e3594fb1c8ea 100644\n--- a/libstdc++-v3/testsuite/29_atomics/atomic/cons/static_zero_padding.cc\n+++ b/libstdc++-v3/testsuite/29_atomics/atomic/cons/static_zero_padding.cc\n@@ -57,9 +57,7 @@ void test_struct(std::atomic<T>& g, const T& zp)\n \n std::atomic<T> l(T{1, 2});\n std::memcpy(&t, &zp, sizeof(T));\n-#if __cplusplus >= 201402L // Remove once PR114865 is fixed\n VERIFY( l.compare_exchange_strong(t, d) );\n-#endif\n \n constexpr std::atomic<T> cl(T{1, 2});\n }\n", "prefixes": [] }