1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // UNSUPPORTED: libcpp-has-no-threads
10 // UNSUPPORTED: c++98, c++03, c++11
11 
12 // <shared_mutex>
13 
14 // template <class Mutex> class shared_lock;
15 
16 // template <class Mutex>
17 //   void swap(shared_lock<Mutex>& x, shared_lock<Mutex>& y) noexcept;
18 
19 #include <shared_mutex>
20 #include <cassert>
21 
22 struct mutex
23 {
24     void lock_shared() {}
25     void unlock_shared() {}
26 };
27 
28 mutex m;
29 
30 int main(int, char**)
31 {
32     std::shared_lock<mutex> lk1(m);
33     std::shared_lock<mutex> lk2;
34     swap(lk1, lk2);
35     assert(lk1.mutex() == nullptr);
36     assert(lk1.owns_lock() == false);
37     assert(lk2.mutex() == &m);
38     assert(lk2.owns_lock() == true);
39     static_assert(noexcept(swap(lk1, lk2)), "non-member swap must be noexcept");
40 
41   return 0;
42 }
43