std::stop_token

 

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std::stop_token

Member functions

stop_token::stop_token

stop_token::~stop_token

stop_token::operator=

Modifiers

stop_token::swap

Observers

stop_token::stop_requested

stop_token::stop_possible

Non-member functions

swap(std::stop_token)

operator==

 

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 alias templates

Type	Definition
callback_type<Callback> (since C++26)	std::stop_callback<Callback>

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