[libcxx-commits] [libcxx] [libc++][In progress] Floating Point Atomic (PR #67799)

[Louis Dionne via libcxx-commits]

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@@ -0,0 +1,49 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+//   static constexpr bool is_always_lock_free = implementation-defined;
+//   bool is_lock_free() const volatile noexcept;
+//   bool is_lock_free() const noexcept;
+
+#include <atomic>
+#include <cassert>
+#include <concepts>
+
+#include "test_macros.h"
+
+template <class T>
+void test() {
+  //   static constexpr bool is_always_lock_free = implementation-defined;
+  {
+    bool r = std::atomic<T>::is_always_lock_free;
+    assert(r == __atomic_always_lock_free(sizeof(T), 0));
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ldionne wrote:

I think these tests could run into the same problem that we are fixing in https://github.com/llvm/llvm-project/pull/68109, i.e. if `sizeof(T)` doesn't allow being lockfree but `sizeof(_Atomic(T))` allows it, this test will fail spuriously.

https://github.com/llvm/llvm-project/pull/67799