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 // explicit lock_guard(mutex_type& m);
17 
18 // template<class _Mutex> lock_guard(lock_guard<_Mutex>)
19 //     -> lock_guard<_Mutex>;  // C++17
20 
21 #include <mutex>
22 #include <thread>
23 #include <cstdlib>
24 #include <cassert>
25 
26 #include "test_macros.h"
27 
28 std::mutex m;
29 
30 typedef std::chrono::system_clock Clock;
31 typedef Clock::time_point time_point;
32 typedef Clock::duration duration;
33 typedef std::chrono::milliseconds ms;
34 typedef std::chrono::nanoseconds ns;
35 
36 void f()
37 {
38     time_point t0 = Clock::now();
39     time_point t1;
40     {
41     std::lock_guard<std::mutex> lg(m);
42     t1 = Clock::now();
43     }
44     ns d = t1 - t0 - ms(250);
45     assert(d < ms(200));  // within 200ms
46 }
47 
48 int main()
49 {
50     m.lock();
51     std::thread t(f);
52     std::this_thread::sleep_for(ms(250));
53     m.unlock();
54     t.join();
55 
56 #ifdef __cpp_deduction_guides
57     std::lock_guard lg(m);
58     static_assert((std::is_same<decltype(lg), std::lock_guard<decltype(m)>>::value), "" );
59 #endif
60 }
61