如何檢查std :: thread是否仍在運行（cross-platform）

使用std :: async and std :: future

{ std :: this_thread :: sleep_for（3s）; 返回8; }）; //檢查線程狀態 自動狀態= future.wait_for（0ms）; if（status == std :: future_status ::準備就緒）{ 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 與std :: thread 
 C 11及以後的一種簡單的方法是利用布爾原子flag：
 {
    std :: this_thread :: sleep_for（3s）;
    完成= true;
  }）;

  //檢查線程狀態
  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 任務（[] {
    std :: this_thread :: sleep_for（3s）;
  }）;
  auto future = task.get_future（）;

  std ::線程t（std :: move（task））;

  //檢查線程狀態
  自動狀態= future.wait_for（0ms）;
  if（status == std :: future_status ::準備就緒）{
    // ...
  }

  T.Join（）;
} [&& && && && &&華