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 // void swap(shared_lock& u) noexcept;
17 
18 #include <shared_mutex>
19 #include <cassert>
20 
21 struct mutex
22 {
23     void lock_shared() {}
24     void unlock_shared() {}
25 };
26 
27 mutex m;
28 
29 int main(int, char**)
30 {
31     std::shared_lock<mutex> lk1(m);
32     std::shared_lock<mutex> lk2;
33     lk1.swap(lk2);
34     assert(lk1.mutex() == nullptr);
35     assert(lk1.owns_lock() == false);
36     assert(lk2.mutex() == &m);
37     assert(lk2.owns_lock() == true);
38     static_assert(noexcept(lk1.swap(lk2)), "member swap must be noexcept");
39 
40   return 0;
41 }
42