[libcxx-commits] [libcxx] [libc++] Implement C++20 atomic_ref (PR #76647)

[Louis Dionne via libcxx-commits]

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@@ -0,0 +1,68 @@
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+// REQUIRES: has-unix-headers
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-hardening-mode=none || libcpp-hardening-mode=fast
+// XFAIL: libcpp-hardening-mode=debug && availability-verbose_abort-missing
+// ADDITIONAL_COMPILE_FLAGS: -Wno-user-defined-warnings
+
+// <atomic>
+
+// bool compare_exchange_strong(T& expected, T desired, memory_order success, memory_order failure) const noexcept;
+//
+// Preconditions: failure is memory_order::relaxed, memory_order::consume, memory_order::acquire, or memory_order::seq_cst.
+
+#include <atomic>
+
+#include "atomic_helpers.h"
+#include "check_assertion.h"
+
+template <typename T>
+struct TestCompareExchangeStrongInvalidMemoryOrder {
+  void operator()() const {
+    {
+      T x(T(1));
+      std::atomic_ref<T> const a(x);
+      T t(T(2));
+      a.compare_exchange_strong(t, T(3), std::memory_order_relaxed, std::memory_order_relaxed);
+    }
+
+    TEST_LIBCPP_ASSERT_FAILURE(
+        ([] {
+          T x(T(1));
+          std::atomic_ref<T> const a(x);
+          T t(T(2));
+          a.compare_exchange_strong(t, T(3), std::memory_order_relaxed, std::memory_order_release);
+        }()),
+        "atomic_ref: failure memory order argument to strong atomic compare-and-exchange operation is invalid");
+
+    TEST_LIBCPP_ASSERT_FAILURE(
+        ([] {
+          T x(T(1));
+          std::atomic_ref<T> const a(x);
+          T t(T(2));
+          a.compare_exchange_strong(t, T(3), std::memory_order_relaxed, std::memory_order_acq_rel);
+        }()),
+        "atomic_ref: failure memory order argument to strong atomic compare-and-exchange operation is invalid");
+  }
+};
+
+void test() {
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ldionne wrote:

Optional nitpick: you could call those from `main` directly. We generally use the `void test(){ }` pattern for things where we need to test both constexpr and non-constexpr, so we call `test()` twice. Again, this is an optional nitpick.

https://github.com/llvm/llvm-project/pull/76647