What happens when calling the destructor of a thread object that has a condition variable waiting?

Question

I am using a SynchronisedQueue to communicate between threads. I found that destroying the thread object when the attaching thread is waiting on a condition var

Answer 1

The destructor for std::thread will call std::terminate if it is run on a thread if you not have called join() (to wait the thread to finish) or detach() (to detach the thread from the object) on it.

Your code calls the destructor for worker_thread without calling join() or detach() on it, and so std::terminate is called. This is unrelated to the presence of condition variables.