From the C++11 spec:
30.3.1.3 thread destructor [thread.thread.destr] ~thread();
If joinable(), calls std::terminate(). Otherwise, has no effects.
[ Note: Either implicitly detaching or joining a joinable() thread in its destructor could result in difficult to debug correctness (for detach) or performance (for join) bugs encountered only when an exception is raised. Thus the pro grammer must ensure that the destructor is never executed while the thread is still joinable. — end note ]
So calling a thread destructor
without first calling join
(to wait for it to finish) or detach
is guarenteed to immediately call std::terminate
and end the program.