std::packaged_task::operator()

C++

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Named requirements

Language support library

Concepts library (C++20)

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Numerics library

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Regular expressions library (C++11)

Atomic operations library (C++11)

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Technical Specifications

Thread support library

Threads
thread (C++11)
hardware_destructive_interference_sizehardware_constructive_interference_size (C++17)(C++17)
this_thread namespace
get_id (C++11) yield (C++11)	sleep_for (C++11) sleep_until (C++11)
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mutex (C++11) recursive_mutex (C++11) shared_mutex (C++17)	timed_mutex (C++11) recursive_timed_mutex (C++11) shared_timed_mutex (C++14)
Generic lock management
lock_guard (C++11) scoped_lock (C++17) unique_lock (C++11) shared_lock (C++14) defer_lock_ttry_to_lock_tadopt_lock_t (C++11)(C++11)(C++11)	lock (C++11) try_lock (C++11) defer_locktry_to_lockadopt_lock (C++11)(C++11)(C++11) once_flag (C++11) call_once (C++11)
Condition variables
condition_variable (C++11)
condition_variable_any (C++11)
notify_all_at_thread_exit (C++11)
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Futures
promise (C++11) future (C++11) shared_future (C++11) packaged_task (C++11) async (C++11)	launch (C++11) future_status (C++11) future_error (C++11) future_category (C++11) future_errc (C++11)

std::packaged_task

Member functions

packaged_task::packaged_task

packaged_task::~packaged_task

packaged_task::operator=

packaged_task::valid

packaged_task::swap

Getting the result

packaged_task::get_future

Execution

packaged_task::operator()

packaged_task::make_ready_at_thread_exit

packaged_task::reset

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

Calls the stored task with args as the arguments. The return value of the task or any exceptions thrown are stored in the shared state. The shared state is made ready and any threads waiting for this are unblocked.

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.

Notes

A successful call to operator() synchronizes with a call to any member function of a std::future or std::shared_future that share their shared state with *this.	(until C++14)
No additional synchronization guarantees other than what's already provided by shared state.	(since C++14)

See also

make_ready_at_thread_exit

executes the function ensuring that the result is ready only once the current thread exits (public member function)