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std::packag..._thread_exit(3)  C++ Standard Libary std::packag..._thread_exit(3)

NAME
     std::packaged_task::make_ready_at_thread_exit	    -	      std::pack-
     aged_task::make_ready_at_thread_exit

Synopsis
	void make_ready_at_thread_exit( ArgTypes... args );  (since C++11)

	Calls the stored task as if by INVOKE<R>(f, args...),  where  f  is  the
     stored task.
	The  return value of the task or any exception thrown by it is stored in
     the shared
	state of *this.

	The shared state is only made ready after the current thread  exits  and
     all objects
	of thread-local storage duration are destroyed.

Parameters
	args - the parameters to pass on invocation of the stored task

Return value
	(none)

Exceptions
	std::future_error on the following error conditions:

	  *  The stored task has already been invoked. The error category is set
     to
	    promise_already_satisfied.
	  * *this has no shared state. The error category is set to no_state.

Example
     // Run this code

      #include <chrono>
      #include <functional>
      #include <future>
      #include <iostream>
      #include <thread>
      #include <utility>

      void worker(std::future<void>& output)
      {
	  std::packaged_task<void(bool&)> my_task{[](bool& done) { done =  true;
     }};
	  auto result = my_task.get_future();

	  bool done = false;
	  my_task.make_ready_at_thread_exit(done); // execute task right away

	  std::cout << "worker: done = " << std::boolalpha << done << std::endl;

	  auto status = result.wait_for(std::chrono::seconds(0));
	  if (status == std::future_status::timeout)
	      std::cout << "worker: result is not ready yet" << std::endl;

	  output = std::move(result);
      }

      int main()
      {
	  std::future<void> result;

	  std::thread{worker, std::ref(result)}.join();

	  auto status = result.wait_for(std::chrono::seconds(0));
	  if (status == std::future_status::ready)
	      std::cout << "main: result is ready" << std::endl;
      }

Output:
      worker: done = true
      worker: result is not ready yet
      main: result is ready

See also
	operator() executes the function
		   (public member function)

http://cppreference.com 	   2024.06.10	   std::packag..._thread_exit(3)
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