std::jthread::joinable
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std::jthread
Member functions
Observers
jthread::joinable
Operations
Stop token handling
Non-member functions
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.
[edit] Parameters
(none)
[edit] Return value
true if the std::jthread object identifies an active thread of execution, false otherwise.
[edit] Example
Run this code
#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
[edit] 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]