4f4d6c81f8
Operating systems are best effort by default, so we cannot assume that sleep-like APIs return as soon as we'd like. Even if a sleep-like API returns when we want it to, the potential for preemption means that attempts to measure time are subject to delays.
36 lines
1.0 KiB
C++
36 lines
1.0 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// UNSUPPORTED: libcpp-has-no-threads
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// <thread>
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// template <class Clock, class Duration>
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// void sleep_until(const chrono::time_point<Clock, Duration>& abs_time);
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#include <thread>
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#include <cstdlib>
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#include <cassert>
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#include "test_macros.h"
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int main(int, char**)
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{
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typedef std::chrono::system_clock Clock;
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typedef Clock::time_point time_point;
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std::chrono::milliseconds ms(500);
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time_point t0 = Clock::now();
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std::this_thread::sleep_until(t0 + ms);
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time_point t1 = Clock::now();
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// NOTE: Operating systems are (by default) best effort and therefore we may
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// have slept longer, perhaps much longer than we requested.
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assert(t1 - t0 >= ms);
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return 0;
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}
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