Newbe Dev Stack

Answer : When a thread object goes out of scope and it is in joinable state, the program is terminated. The Standard Committee had two other options for the destructor of a joinable thread. It could quietly join -- but join might never return if the thread is stuck. Or it could detach the thread (a detached thread is not joinable). However, detached threads are very tricky, since they might survive till the end of the program and mess up the release of resources. So if you don't want to terminate your program, make sure you join (or detach) every thread. How to reproduce that error: #include <iostream> #include <stdlib.h> #include <string> #include <thread> using namespace std; void task1(std::string msg){ cout << "task1 says: " << msg; } int main() { std::thread t1(task1, "hello"); return 0; } Compile and run: el@defiant ~/foo4/39_threading $ g++ -o s s.cpp -pthread -std=c++11 el@defiant ~/foo4/39_threading ...

Answer : Wait and await - while similar conceptually - are actually completely different. Wait will synchronously block until the task completes. So the current thread is literally blocked waiting for the task to complete. As a general rule, you should use " async all the way down"; that is, don't block on async code. On my blog, I go into the details of how blocking in asynchronous code causes deadlock. await will asynchronously wait until the task completes. This means the current method is "paused" (its state is captured) and the method returns an incomplete task to its caller. Later, when the await expression completes, the remainder of the method is scheduled as a continuation. You also mentioned a "cooperative block", by which I assume you mean a task that you're Wait ing on may execute on the waiting thread. There are situations where this can happen, but it's an optimization. There are many situations where it can't...