NAME

std::thread::join - std::thread::join

Synopsis

void join(); (since C++11)

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 thread 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 <iostream>
#include <thread>
#include <chrono>

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::thread helper1(foo);

std::cout << "starting second helper...\n";
std::thread 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++20 standard (ISO/IEC 14882:2020):

* 32.4.2.5 Members [thread.thread.member]

* C++17 standard (ISO/IEC 14882:2017):

* 33.3.2.5 thread members [thread.thread.member]

* C++14 standard (ISO/IEC 14882:2014):

* 30.3.1.5 thread members [thread.thread.member]

* C++11 standard (ISO/IEC 14882:2011):

* 30.3.1.5 thread members [thread.thread.member]