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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 // <mutex>
11 
12 // template <class Mutex> class lock_guard;
13 
14 // explicit lock_guard(mutex_type& m);
15 
16 #include <mutex>
17 #include <thread>
18 #include <cstdlib>
19 #include <cassert>
20 
21 std::mutex m;
22 
23 typedef std::chrono::system_clock Clock;
24 typedef Clock::time_point time_point;
25 typedef Clock::duration duration;
26 typedef std::chrono::milliseconds ms;
27 typedef std::chrono::nanoseconds ns;
28 
f()29 void f()
30 {
31     time_point t0 = Clock::now();
32     time_point t1;
33     {
34     std::lock_guard<std::mutex> lg(m);
35     t1 = Clock::now();
36     }
37     ns d = t1 - t0 - ms(250);
38     assert(d < ns(2500000));  // within 2.5ms
39 }
40 
main()41 int main()
42 {
43     m.lock();
44     std::thread t(f);
45     std::this_thread::sleep_for(ms(250));
46     m.unlock();
47     t.join();
48 }
49