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 // UNSUPPORTED: c++98, c++03
12 
13 // <future>
14 
15 // class future<R>
16 
17 // template <class Clock, class Duration>
18 //   future_status
19 //   wait_until(const chrono::time_point<Clock, Duration>& abs_time) const;
20 
21 #include <future>
22 #include <atomic>
23 #include <cassert>
24 
25 enum class WorkerThreadState { Uninitialized, AllowedToRun, Exiting };
26 typedef std::chrono::milliseconds ms;
27 
28 std::atomic<WorkerThreadState> thread_state(WorkerThreadState::Uninitialized);
29 
set_worker_thread_state(WorkerThreadState state)30 void set_worker_thread_state(WorkerThreadState state)
31 {
32     thread_state.store(state, std::memory_order_relaxed);
33 }
34 
wait_for_worker_thread_state(WorkerThreadState state)35 void wait_for_worker_thread_state(WorkerThreadState state)
36 {
37     while (thread_state.load(std::memory_order_relaxed) != state);
38 }
39 
func1(std::promise<int> p)40 void func1(std::promise<int> p)
41 {
42     wait_for_worker_thread_state(WorkerThreadState::AllowedToRun);
43     p.set_value(3);
44     set_worker_thread_state(WorkerThreadState::Exiting);
45 }
46 
47 int j = 0;
48 
func3(std::promise<int &> p)49 void func3(std::promise<int&> p)
50 {
51     wait_for_worker_thread_state(WorkerThreadState::AllowedToRun);
52     j = 5;
53     p.set_value(j);
54     set_worker_thread_state(WorkerThreadState::Exiting);
55 }
56 
func5(std::promise<void> p)57 void func5(std::promise<void> p)
58 {
59     wait_for_worker_thread_state(WorkerThreadState::AllowedToRun);
60     p.set_value();
61     set_worker_thread_state(WorkerThreadState::Exiting);
62 }
63 
main()64 int main()
65 {
66     typedef std::chrono::high_resolution_clock Clock;
67     {
68         typedef int T;
69         std::promise<T> p;
70         std::future<T> f = p.get_future();
71         std::thread(func1, std::move(p)).detach();
72         assert(f.valid());
73         assert(f.wait_until(Clock::now() + ms(10)) == std::future_status::timeout);
74         assert(f.valid());
75 
76         // allow the worker thread to produce the result and wait until the worker is done
77         set_worker_thread_state(WorkerThreadState::AllowedToRun);
78         wait_for_worker_thread_state(WorkerThreadState::Exiting);
79 
80         assert(f.wait_until(Clock::now() + ms(10)) == std::future_status::ready);
81         assert(f.valid());
82         Clock::time_point t0 = Clock::now();
83         f.wait();
84         Clock::time_point t1 = Clock::now();
85         assert(f.valid());
86         assert(t1-t0 < ms(5));
87     }
88     {
89         typedef int& T;
90         std::promise<T> p;
91         std::future<T> f = p.get_future();
92         std::thread(func3, std::move(p)).detach();
93         assert(f.valid());
94         assert(f.wait_until(Clock::now() + ms(10)) == std::future_status::timeout);
95         assert(f.valid());
96 
97         // allow the worker thread to produce the result and wait until the worker is done
98         set_worker_thread_state(WorkerThreadState::AllowedToRun);
99         wait_for_worker_thread_state(WorkerThreadState::Exiting);
100 
101         assert(f.wait_until(Clock::now() + ms(10)) == std::future_status::ready);
102         assert(f.valid());
103         Clock::time_point t0 = Clock::now();
104         f.wait();
105         Clock::time_point t1 = Clock::now();
106         assert(f.valid());
107         assert(t1-t0 < ms(5));
108     }
109     {
110         typedef void T;
111         std::promise<T> p;
112         std::future<T> f = p.get_future();
113         std::thread(func5, std::move(p)).detach();
114         assert(f.valid());
115         assert(f.wait_until(Clock::now() + ms(10)) == std::future_status::timeout);
116         assert(f.valid());
117 
118         // allow the worker thread to produce the result and wait until the worker is done
119         set_worker_thread_state(WorkerThreadState::AllowedToRun);
120         wait_for_worker_thread_state(WorkerThreadState::Exiting);
121 
122         assert(f.wait_until(Clock::now() + ms(10)) == std::future_status::ready);
123         assert(f.valid());
124         Clock::time_point t0 = Clock::now();
125         f.wait();
126         Clock::time_point t1 = Clock::now();
127         assert(f.valid());
128         assert(t1-t0 < ms(5));
129     }
130 }
131