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

[Louis Dionne via libcxx-commits]

================
@@ -0,0 +1,91 @@
+//
+// 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
+
+// bool compare_exchange_weak(T&, T, memory_order, memory_order) const noexcept;
+// bool compare_exchange_weak(T&, T, memory_order = memory_order::seq_cst) const noexcept;
+
+#include <atomic>
+#include <concepts>
+#include <cassert>
+#include <type_traits>
+
+#include "test_macros.h"
+
+template <typename T>
+void test_compare_exchange_weak() {
+  {
+    T x(T(1));
+    std::atomic_ref<T> const a(x);
+
+    T t(T(1));
+    std::same_as<bool> auto y = a.compare_exchange_weak(t, T(2));
+    assert(y == true);
+    assert(a == T(2));
+    assert(t == T(1));
+    y = a.compare_exchange_weak(t, T(3));
+    assert(y == false);
+    assert(a == T(2));
+    assert(t == T(2));
+
+    ASSERT_NOEXCEPT(a.compare_exchange_weak(t, T(2)));
+  }
+  {
+    T x(T(1));
+    std::atomic_ref<T> const a(x);
+
+    T t(T(1));
+    std::same_as<bool> auto y = a.compare_exchange_weak(t, T(2), std::memory_order_seq_cst);
+    assert(y == true);
+    assert(a == T(2));
+    assert(t == T(1));
+    y = a.compare_exchange_weak(t, T(3), std::memory_order_seq_cst);
+    assert(y == false);
+    assert(a == T(2));
+    assert(t == T(2));
+
+    ASSERT_NOEXCEPT(a.compare_exchange_weak(t, T(2), std::memory_order_seq_cst));
+  }
+  {
+    T x(T(1));
+    std::atomic_ref<T> const a(x);
+
+    T t(T(1));
+    std::same_as<bool> auto y = a.compare_exchange_weak(t, T(2), std::memory_order_release, std::memory_order_relaxed);
+    assert(y == true);
+    assert(a == T(2));
+    assert(t == T(1));
+    y = a.compare_exchange_weak(t, T(3), std::memory_order_release, std::memory_order_relaxed);
+    assert(y == false);
+    assert(a == T(2));
+    assert(t == T(2));
+
+    ASSERT_NOEXCEPT(a.compare_exchange_weak(t, T(2), std::memory_order_release, std::memory_order_relaxed));
+  }
+}
+
+void test() {
+  test_compare_exchange_weak<int>();
+
+  test_compare_exchange_weak<float>();
+
+  test_compare_exchange_weak<int*>();
+
+  struct X {
+    int i;
+    //X() = default;
+    X(int ii) noexcept : i(ii) {}
+    bool operator==(X o) const { return i == o.i; }
+  };
+  test_compare_exchange_weak<X>();
----------------
ldionne wrote:

You could use `libcxx/test/support/type_algorithms.h` or `libcxx/test/support/atomic_helpers.h` for instantiating on multiple types.

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