std::jthread::joinable
bool joinable() const noexcept; | (since C++20) |
Checks if the std::jthread object identifies an active thread of execution. Specifically, returns true if get_id() != std::jthread::id(). So a default constructed jthread is not joinable.
A thread that has finished executing code, but has not yet been joined is still considered an active thread of execution and is therefore joinable.
Parameters
(none)
Return value
true if the std::jthread object identifies an active thread of execution, false otherwise.
Example
#include <chrono>
#include <iostream>
#include <thread>
using namespace std::chrono_literals;
void foo()
{
std::this_thread::sleep_for(500ms);
}
int main()
{
std::cout << std::boolalpha;
std::jthread t;
std::cout << "before starting, joinable: " << t.joinable() << '\n';
t = std::jthread{foo};
std::cout << "after starting, joinable: " << t.joinable() << '\n';
t.join();
std::cout << "after joining, joinable: " << t.joinable() << '\n';
t = std::jthread{foo};
t.detach();
std::cout << "after detaching, joinable: " << t.joinable() << '\n';
}
Output:
before starting, joinable: false after starting, joinable: true after joining, joinable: false after detaching, joinable: false
References
- C++23 standard (ISO/IEC 14882:2024):
- 33.4.4.3 Members [thread.jthread.mem]
- C++20 standard (ISO/IEC 14882:2020):
- 32.4.3.2 Members [thread.jthread.mem]
See also
| returns the id of the thread (public member function) |
|
| waits for the thread to finish its execution (public member function) |
|
| permits the thread to execute independently from the thread handle (public member function) |
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