std::thread move constructor

Question

I recently looked at this std::thread reference.

For the move constructor it says:

 thread( thread&& other ); 

Move constructor. Constructs the thread object to represent the thread of execution that was represented by other. After this call other no longer represents a thread of execution.

Also, in the example below there are these lines:

int n=0;
std::thread t3(f2, n);
std::thread t4(std::move(t3)); // t4 is now running f2(). t3 is no longer a thread

What I don't understand is what exactly happens with thread t3 and t4 ? Does t4 waits until t3 finish its execution? What does it mean that t3 is no longer a thread?

Answer 1

std::thread isn't a thread. It is a representation of a thread provided by an underlying operating system that you can use to manipulate the thread. This is just like a car object isn't really a car.

move moves the thread being represented from one std::thread to another. After the move , t3 is a gutless std::thread . The std::thread object is still there, but t3 doesn't reference any actual system thread. t4 now represents the thread previously represented by t3 , but it will not wait unless you call join .