plugins/tests/system/atomic

// Copyright 2021 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef TOOLS_CLANG_PLUGINS_TESTS_SYSTEM_ATOMIC_
#define TOOLS_CLANG_PLUGINS_TESTS_SYSTEM_ATOMIC_

namespace std {

// Faux-implementation of std::atomic.
// The standard requires that the following conditions are met for `T`:
// std::is_copy_constructible<T>::value == true
// std::is_move_constructible<T>::value == true
// std::is_copy_assignable<T>::value == true
// std::is_move_assignable<T>::value == true
// std::is_trivially_copyable<T>::value == true
//
// An exception is made to the last condition for
// std::atomic<std::shared_ptr<T>> and std::atomic<std::weak_ptr<T>>, by
// defining partial-specializations in <memory>
//
// The standard also says that std::atomic<Integral> (where `Integral` is a
// built-in integral type, including raw pointers) is a standard-layout struct,
// and has a trivial destructor:
// https://eel.is/c++draft/atomics.types.generic#atomics.types.int-2
template <typename T>
struct atomic {
  T i;

  atomic();
  ~atomic() = default;

  // std::atomic is never copyable or moveable
  atomic(const atomic&) = delete;
  atomic(atomic&&) = delete;
  atomic& operator=(const atomic&) = delete;
  atomic& operator=(atomic&&) = delete;
};

using atomic_int = std::atomic<int>;

}  // namespace std

#endif  // TOOLS_CLANG_PLUGINS_TESTS_SYSTEM_ATOMIC_