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// lock_guard(mutex_type& m, adopt_lock_t);
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    m.lock();
35    std::lock_guard<std::mutex> lg(m, std::adopt_lock);
36    t1 = Clock::now();
37    }
38    ns d = t1 - t0 - ms(250);
39    assert(d < ms(50));  // within 50ms
40}
41
42int main()
43{
44    m.lock();
45    std::thread t(f);
46    std::this_thread::sleep_for(ms(250));
47    m.unlock();
48    t.join();
49}
50