std::packaged_task<R(Args...)>::operator()

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void operator()( 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 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.

Example

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 2142 C++11 a successful call to operator() synchronized with
a call to any member function of a std::future or
std::shared_future that share their shared state with *this
no additional synchronization
guarantees other than what is
already provided by shared state

See also

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