1 //===----------------------------------------------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // UNSUPPORTED: libcpp-has-no-threads
11 // UNSUPPORTED: c++98, c++03, c++11
12 
13 // <shared_mutex>
14 
15 // template <class Mutex> class shared_lock;
16 
17 // template <class Mutex>
18 //   void swap(shared_lock<Mutex>& x, shared_lock<Mutex>& y) noexcept;
19 
20 #include <shared_mutex>
21 #include <cassert>
22 
23 struct mutex
24 {
lock_sharedmutex25     void lock_shared() {}
unlock_sharedmutex26     void unlock_shared() {}
27 };
28 
29 mutex m;
30 
main()31 int main()
32 {
33     std::shared_lock<mutex> lk1(m);
34     std::shared_lock<mutex> lk2;
35     swap(lk1, lk2);
36     assert(lk1.mutex() == nullptr);
37     assert(lk1.owns_lock() == false);
38     assert(lk2.mutex() == &m);
39     assert(lk2.owns_lock() == true);
40     static_assert(noexcept(swap(lk1, lk2)), "non-member swap must be noexcept");
41 }
42