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
21std::mutex m;
22
23typedef std::chrono::system_clock Clock;
24typedef Clock::time_point time_point;
25typedef Clock::duration duration;
26typedef std::chrono::milliseconds ms;
27typedef std::chrono::nanoseconds ns;
28
29void 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
41int 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