libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.cons/mutex.pass.cpp

//===----------------------------------------------------------------------===//
//
// 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: no-threads
// UNSUPPORTED: c++03, c++11

// <shared_mutex>

// template <class Mutex> class shared_lock;

// explicit shared_lock(mutex_type& m);

// template<class _Mutex> shared_lock(shared_lock<_Mutex>)
//     -> shared_lock<_Mutex>;  // C++17

#include <atomic>
#include <cassert>
#include <shared_mutex>
#include <thread>
#include <type_traits>
#include <vector>

#include "make_test_thread.h"
#include "test_macros.h"

struct Monitor {
  bool lock_shared_called   = false;
  bool unlock_shared_called = false;
};

struct TrackedMutex {
  Monitor* monitor = nullptr;

  void lock_shared() {
    if (monitor != nullptr)
      monitor->lock_shared_called = true;
  }
  void unlock_shared() {
    if (monitor != nullptr)
      monitor->unlock_shared_called = true;
  }
};

template <class Mutex>
void test() {
  // Basic sanity test
  {
    Mutex mutex;
    std::vector<std::thread> threads;
    std::atomic<bool> ready(false);
    for (int i = 0; i != 5; ++i) {
      threads.push_back(support::make_test_thread([&] {
        while (!ready) {
          // spin
        }

        std::shared_lock<Mutex> lock(mutex);
        assert(lock.owns_lock());
      }));
    }

    ready = true;
    for (auto& t : threads)
      t.join();
  }

  // Test CTAD
  {
#if TEST_STD_VER >= 17
    Mutex mutex;
    std::shared_lock lock(mutex);
    static_assert(std::is_same<decltype(lock), std::shared_lock<Mutex>>::value);
#endif
  }
}

int main(int, char**) {
#if TEST_STD_VER >= 17
  test<std::shared_mutex>();
#endif
  test<std::shared_timed_mutex>();
  test<TrackedMutex>();

  // Use shared_lock with a dummy mutex class that tracks whether each
  // operation has been called or not.
  {
    Monitor monitor;
    TrackedMutex mutex{&monitor};

    std::shared_lock<TrackedMutex> lock(mutex);
    assert(monitor.lock_shared_called);
    assert(lock.owns_lock());

    lock.unlock();
    assert(monitor.unlock_shared_called);
  }

  return 0;
}