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 // <mutex>
13 
14 // template <class Mutex> class unique_lock;
15 
16 // mutex_type *mutex() const;
17 
18 #include <mutex>
19 #include <cassert>
20 
21 std::mutex m;
22 
main()23 int main()
24 {
25     std::unique_lock<std::mutex> lk0;
26     assert(lk0.mutex() == nullptr);
27     std::unique_lock<std::mutex> lk1(m);
28     assert(lk1.mutex() == &m);
29     lk1.unlock();
30     assert(lk1.mutex() == &m);
31 }
32