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std::packag..._thread_exit(3) C++ Standard Libarystd::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	with forwarded args as the arguments. The  re-
       turn 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 <future>
	#include <iostream>
	#include <chrono>
	#include <thread>
	#include <functional>
	#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		  2022.07.31	 std::packag..._thread_exit(3)

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