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

Calls the stored task with forwarded args as the arguments. 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.


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

Return value



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.


#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;


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

See also

executes the function
(public member function)

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