std::thread::joinable

bool joinable() const;
(since C++11)

Checks if the thread object identifies an active thread of execution. Specifically, returns true if get_id() != std::thread::id(). So a default constructed thread 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 thread object identifies an active thread of execution, false otherwise.

Exceptions

noexcept specification:
noexcept

Example

#include <iostream>
#include <thread>
#include <chrono>
 
void foo()
{
    std::this_thread::sleep_for(std::chrono::seconds(1));
}
 
int main()
{
    std::thread t;
    std::cout << "before starting, joinable: " << t.joinable() << '\n';
 
    t = std::thread(foo);
    std::cout << "after starting, joinable: " << t.joinable() << '\n';
 
    t.join();
    std::cout << "after joining, joinable: " << t.joinable() << '\n';
}

Output:

before starting, joinable: 0
after starting, joinable: 1
after joining, joinable: 0

See also

returns the id of the thread
(public member function)
waits for a thread to finish its execution
(public member function)
permits the thread to execute independently from the thread handle
(public member function)

References

  • C++11 standard (ISO/IEC 14882:2011):
    • 30.3.1.5 thread members [thread.thread.member]
doc_CPP
2016-10-11 10:07:21
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