libcxx/test/std/thread/futures/futures.async/async_race.pass.cpp

   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: no-threads
  10 // UNSUPPORTED: c++03
  11
  12 // <future>
  13
  14 // template <class F, class... Args>
  15 //     future<typename result_of<F(Args...)>::type>
  16 //     async(F&& f, Args&&... args);
  17
  18 // template <class F, class... Args>
  19 //     future<typename result_of<F(Args...)>::type>
  20 //     async(launch policy, F&& f, Args&&... args);
  21
  22 // This test is designed to cause and allow TSAN to detect the race condition
  23 // reported in PR23293: https://llvm.org/PR23293
  24
  25 #include <future>
  26 #include <chrono>
  27 #include <thread>
  28 #include <memory>
  29 #include <cassert>
  30
  31 #include "test_macros.h"
  32
  33 int f_async() {
  34     typedef std::chrono::milliseconds ms;
  35     std::this_thread::sleep_for(ms(200));
  36     return 42;
  37 }
  38
  39 bool ran = false;
  40
  41 int f_deferred() {
  42     ran = true;
  43     return 42;
  44 }
  45
  46 void test_each() {
  47     {
  48         std::future<int> f = std::async(f_async);
  49         int const result = f.get();
  50         assert(result == 42);
  51     }
  52     {
  53         std::future<int> f = std::async(std::launch::async, f_async);
  54         int const result = f.get();
  55         assert(result == 42);
  56     }
  57     {
  58         ran = false;
  59         std::future<int> f = std::async(std::launch::deferred, f_deferred);
  60         assert(ran == false);
  61         int const result = f.get();
  62         assert(ran == true);
  63         assert(result == 42);
  64     }
  65 }
  66
  67 int main(int, char**) {
  68     for (int i=0; i < 25; ++i) test_each();
  69
  70   return 0;
  71 }