std::jthread::join
From cppreference.com
| 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.
Parameters
(none)
Return value
(none)
Postconditions
joinable() is false.
Exceptions
std::system_error if an error occurs.
Error conditions
- resource_deadlock_would_occur if this->get_id() == std::this_thread::get_id() (deadlock detected).
- no_such_process if the thread is not valid.
- invalid_argument if joinable() is false.
Example
Run this code
#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!
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
| permits the thread to execute independently from the thread handle (public member function) | |
| checks whether the thread is joinable, i.e. potentially running in parallel context (public member function) | |
| C documentation for thrd_join
| |