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std::jthread::join

From cppreference.com
< cpp‎ | thread‎ | jthread
 
 
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void join();
(since C++20)

Blocks the current thread until the thread identified by *this finishes its execution.

The completion of the thread identified by *this synchronizes with the corresponding successful return from join().

No synchronization is performed on *this itself. Concurrently calling join() on the same jthread object from multiple threads constitutes a data race that results in undefined behavior.

Contents

[edit] Parameters

(none)

[edit] Return value

(none)

[edit] Postconditions

joinable() is false.

[edit] Exceptions

std::system_error if an error occurs.

[edit] Error conditions

[edit] Example

#include <chrono>
#include <iostream>
#include <thread>
 
void foo()
{
    // simulate expensive operation
    std::this_thread::sleep_for(std::chrono::seconds(1));
}
 
void bar()
{
    // simulate expensive operation
    std::this_thread::sleep_for(std::chrono::seconds(1));
}
 
int main()
{
    std::cout << "starting first helper...\n";
    std::jthread helper1(foo);
 
    std::cout << "starting second helper...\n";
    std::jthread helper2(bar);
 
    std::cout << "waiting for helpers to finish..." << std::endl;
    helper1.join();
    helper2.join();
 
    std::cout << "done!\n";
}

Output:

starting first helper...
starting second helper...
waiting for helpers to finish...
done!

[edit] References

  • C++23 standard (ISO/IEC 14882:2023):
  • 33.4.4.3 Members [thread.jthread.mem]
  • C++20 standard (ISO/IEC 14882:2020):
  • 32.4.3.2 Members [thread.jthread.mem]

[edit] See also

permits the thread to execute independently from the thread handle
(public member function) [edit]
checks whether the thread is joinable, i.e. potentially running in parallel context
(public member function) [edit]
C documentation for thrd_join