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 
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 #if _LIBCPP_STD_VER > 11
23 
24 struct mutex
25 {
lock_sharedmutex26     void lock_shared() {}
unlock_sharedmutex27     void unlock_shared() {}
28 };
29 
30 mutex m;
31 
32 #endif  // _LIBCPP_STD_VER > 11
33 
main()34 int main()
35 {
36 #if _LIBCPP_STD_VER > 11
37     std::shared_lock<mutex> lk1(m);
38     std::shared_lock<mutex> lk2;
39     swap(lk1, lk2);
40     assert(lk1.mutex() == nullptr);
41     assert(lk1.owns_lock() == false);
42     assert(lk2.mutex() == &m);
43     assert(lk2.owns_lock() == true);
44     static_assert(noexcept(swap(lk1, lk2)), "non-member swap must be noexcept");
45 #endif  // _LIBCPP_STD_VER > 11
46 }
47