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std::promise::set_value_at_thread_exit(3) | C++ Standard Libary | std::promise::set_value_at_thread_exit(3) |
NAME¶
std::promise::set_value_at_thread_exit - std::promise::set_value_at_thread_exit
Synopsis¶
void set_value_at_thread_exit( const R& (member only of
generic promise
value ); (1) template)
(since C++11)
(member only of generic promise
void set_value_at_thread_exit( R&& value ); (2) template)
(since C++11)
(member only of promise<R&> template
void set_value_at_thread_exit( R& value ); (3) specialization)
(since C++11)
(member only of promise<void>
void set_value_at_thread_exit() (4) template specialization)
(since C++11)
Stores the value into the shared state without making the state ready
immediately.
The state is made ready when the current thread exits, after all variables
with
thread-local storage duration have been destroyed.
The operation behaves as though set_value, set_exception,
set_value_at_thread_exit,
and set_exception_at_thread_exit acquire a single mutex associated with the
promise
object while updating the promise object.
An exception is thrown if there is no shared state or the shared state
already
stores a value or exception.
Calls to this function do not introduce data races with calls to get_future
(therefore they need not synchronize with each other).
Parameters¶
value - value to store in the shared state
Return value¶
(none)
Exceptions¶
std::future_error on the following conditions:
* *this has no shared state. The error code is set to no_state.
* The shared state already stores a value or exception. The error code is set
to
promise_already_satisfied.
Additionally:
1-2) Any exception thrown by the copy constructor of value
3) Any exception thrown by the move constructor of value
Example¶
// Run this code
#include <iostream>
#include <future>
#include <thread>
int main()
{
using namespace std::chrono_literals;
std::promise<int> p;
std::future<int> f = p.get_future();
std::thread([&p] {
std::this_thread::sleep_for(1s);
p.set_value_at_thread_exit(9);
}).detach();
std::cout << "Waiting..." << std::flush;
f.wait();
std::cout << "Done!\nResult is: " << f.get() <<
'\n';
}
Output:¶
Waiting...Done!
Result is: 9
See also¶
set_value sets the result to specific value
(public member function)
2022.07.31 | http://cppreference.com |