1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // UNSUPPORTED: libcpp-has-no-threads
10 // UNSUPPORTED: c++98, c++03
11 
12 // <future>
13 
14 // class future<R>
15 
16 // template <class Clock, class Duration>
17 //   future_status
18 //   wait_until(const chrono::time_point<Clock, Duration>& abs_time) const;
19 
20 #include <future>
21 #include <atomic>
22 #include <cassert>
23 
24 enum class WorkerThreadState { Uninitialized, AllowedToRun, Exiting };
25 typedef std::chrono::milliseconds ms;
26 
27 std::atomic<WorkerThreadState> thread_state(WorkerThreadState::Uninitialized);
28 
29 void set_worker_thread_state(WorkerThreadState state)
30 {
31     thread_state.store(state, std::memory_order_relaxed);
32 }
33 
34 void wait_for_worker_thread_state(WorkerThreadState state)
35 {
36     while (thread_state.load(std::memory_order_relaxed) != state);
37 }
38 
39 void func1(std::promise<int> p)
40 {
41     wait_for_worker_thread_state(WorkerThreadState::AllowedToRun);
42     p.set_value(3);
43     set_worker_thread_state(WorkerThreadState::Exiting);
44 }
45 
46 int j = 0;
47 
48 void func3(std::promise<int&> p)
49 {
50     wait_for_worker_thread_state(WorkerThreadState::AllowedToRun);
51     j = 5;
52     p.set_value(j);
53     set_worker_thread_state(WorkerThreadState::Exiting);
54 }
55 
56 void func5(std::promise<void> p)
57 {
58     wait_for_worker_thread_state(WorkerThreadState::AllowedToRun);
59     p.set_value();
60     set_worker_thread_state(WorkerThreadState::Exiting);
61 }
62 
63 int main(int, char**)
64 {
65     typedef std::chrono::high_resolution_clock Clock;
66     {
67         typedef int T;
68         std::promise<T> p;
69         std::future<T> f = p.get_future();
70         std::thread(func1, std::move(p)).detach();
71         assert(f.valid());
72         assert(f.wait_until(Clock::now() + ms(10)) == std::future_status::timeout);
73         assert(f.valid());
74 
75         // allow the worker thread to produce the result and wait until the worker is done
76         set_worker_thread_state(WorkerThreadState::AllowedToRun);
77         wait_for_worker_thread_state(WorkerThreadState::Exiting);
78 
79         assert(f.wait_until(Clock::now() + ms(10)) == std::future_status::ready);
80         assert(f.valid());
81         Clock::time_point t0 = Clock::now();
82         f.wait();
83         Clock::time_point t1 = Clock::now();
84         assert(f.valid());
85         assert(t1-t0 < ms(5));
86     }
87     {
88         typedef int& T;
89         std::promise<T> p;
90         std::future<T> f = p.get_future();
91         std::thread(func3, std::move(p)).detach();
92         assert(f.valid());
93         assert(f.wait_until(Clock::now() + ms(10)) == std::future_status::timeout);
94         assert(f.valid());
95 
96         // allow the worker thread to produce the result and wait until the worker is done
97         set_worker_thread_state(WorkerThreadState::AllowedToRun);
98         wait_for_worker_thread_state(WorkerThreadState::Exiting);
99 
100         assert(f.wait_until(Clock::now() + ms(10)) == std::future_status::ready);
101         assert(f.valid());
102         Clock::time_point t0 = Clock::now();
103         f.wait();
104         Clock::time_point t1 = Clock::now();
105         assert(f.valid());
106         assert(t1-t0 < ms(5));
107     }
108     {
109         typedef void T;
110         std::promise<T> p;
111         std::future<T> f = p.get_future();
112         std::thread(func5, std::move(p)).detach();
113         assert(f.valid());
114         assert(f.wait_until(Clock::now() + ms(10)) == std::future_status::timeout);
115         assert(f.valid());
116 
117         // allow the worker thread to produce the result and wait until the worker is done
118         set_worker_thread_state(WorkerThreadState::AllowedToRun);
119         wait_for_worker_thread_state(WorkerThreadState::Exiting);
120 
121         assert(f.wait_until(Clock::now() + ms(10)) == std::future_status::ready);
122         assert(f.valid());
123         Clock::time_point t0 = Clock::now();
124         f.wait();
125         Clock::time_point t1 = Clock::now();
126         assert(f.valid());
127         assert(t1-t0 < ms(5));
128     }
129 
130   return 0;
131 }
132