NAME¶

std::stop_token - std::stop_token

Synopsis¶

Defined in header <stop_token>
class stop_token; (since C++20)

The stop_token class provides the means to check if a stop request has been made or
can be made, for its associated std::stop_source object. It is essentially a
thread-safe "view" of the associated stop-state.

The stop_token can also be passed to the constructor of std::stop_callback, such
that the callback will be invoked if the stop_token's associated std::stop_source is
requested to stop. And stop_token can be passed to the interruptible waiting
functions of std::condition_variable_any, to interrupt the condition variable's wait
if stop is requested.

Member functions¶

constructor constructs new stop_token object
(public member function)
destructor destructs the stop_token object
(public member function)
operator= assigns the stop_token object
(public member function)

Modifiers¶

swap swaps two stop_token objects
(public member function)

Observers¶

stop_requested checks whether the associated stop-state has been requested to stop
(public member function)
stop_possible checks whether associated stop-state can be requested to stop
(public member function)

Non-member functions¶

operator== compares two std::stop_token objects
(function)
swap(std::stop_token) specializes the std::swap algorithm
(C++20) (function)

Notes¶

A stop_token object is not generally constructed independently, but rather retrieved
from a std::jthread or std::stop_source. This makes it share the same associated
stop-state as the std::jthread or std::stop_source.

Feature-test macro Value Std Feature
__cpp_lib_jthread 201911L (C++20) Stop token and joining thread

Example¶

// Run this code

#include <iostream>
#include <thread>

using namespace std::literals::chrono_literals;

void f(std::stop_token stop_token, int value)
{
while (!stop_token.stop_requested())
{
std::cout << value++ << ' ' << std::flush;
std::this_thread::sleep_for(200ms);
}
std::cout << std::endl;
}

int main()
{
std::jthread thread(f, 5); // prints 5 6 7 8... for approximately 3 seconds
std::this_thread::sleep_for(3s);
// The destructor of jthread calls request_stop() and join().
}

Possible output:¶

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19