如何检查std :: thread是否仍在运行（cross-platform）

使用std :: async and std :: future

{ std :: this_thread :: sleep_for（3s）; 返回8; }）; //检查线程状态 自动状态= future.wait_for（0ms）; if（status == std :: future_status ::准备就绪）{ std :: cout

Using std::promise (with std::thread)

If std::async is not an option, you can employ std::promise to obtain a future object:

#include 
#include 

int main() {
  auto future = std::async(std::launch::async, [] {
    std::this_thread::sleep_for(3s);
    return 8;
  });

  // Check thread status
  auto status = future.wait_for(0ms);
  if (status == std::future_status::ready) {
    std::cout 使用std :: atomic 与std :: thread 
 C 11及以后的一种简单的方法是利用布尔原子flag：
 {
    std :: this_thread :: sleep_for（3s）;
    完成= true;
  }）;

  //检查线程状态
  如果（完成）{
    std :: cout Using std::packaged_task (with std::thread)
#include 
#include 

int main() {
  std::promise p;
  auto future = p.get_future();

  std::thread t([&p] {
    std::this_thread::sleep_for(3s);
    p.set_value(true);
  });

  // Check thread status
  auto status = future.wait_for(0ms);
  if (status == std::future_status::ready) {
    std::cout Another option is to leverage std::packaged_task, which provides a cleaner alternative to using std::promise:
#include 
#include 

int main（）{
  std :: packaged_task 任务（[] {
    std :: this_thread :: sleep_for（3s）;
  }）;
  auto future = task.get_future（）;

  std ::线程t（std :: move（task））;

  //检查线程状态
  自动状态= future.wait_for（0ms）;
  if（status == std :: future_status ::准备就绪）{
    // ...
  }

  T.Join（）;
} [&& && && && &&华