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 lock_guard;
15 
16 // lock_guard(mutex_type& m, adopt_lock_t);
17 
18 #include <mutex>
19 #include <thread>
20 #include <cstdlib>
21 #include <cassert>
22 
23 std::mutex m;
24 
25 typedef std::chrono::system_clock Clock;
26 typedef Clock::time_point time_point;
27 typedef Clock::duration duration;
28 typedef std::chrono::milliseconds ms;
29 typedef std::chrono::nanoseconds ns;
30 
f()31 void f()
32 {
33     time_point t0 = Clock::now();
34     time_point t1;
35     {
36     m.lock();
37     std::lock_guard<std::mutex> lg(m, std::adopt_lock);
38     t1 = Clock::now();
39     }
40     ns d = t1 - t0 - ms(250);
41     assert(d < ms(50));  // within 50ms
42 }
43 
main()44 int main()
45 {
46     m.lock();
47     std::thread t(f);
48     std::this_thread::sleep_for(ms(250));
49     m.unlock();
50     t.join();
51 }
52