just::thread Complete C++ Standard Thread Library by Just Software Solutions

this->joinable() would return true

Blocks the current thread until the thread of execution associated with *this has finished.

this->get_id()==id(). The thread of execution associated with *this prior to the call has finished.

The completion of the thread of execution associated with *this prior to the call happens-before the call to join() returns.

std::system_error if the effects cannot be achieved or this->joinable() would return false.