running std::thread not in Constructor

Question

I want to understand how to work with std::thread. Most of std::thread tutorials looks like that

void foo() { ... }
....
std::thread thread(foo);
....
thread.join();

Ok, I understand that we can specify which function attached to thread in constructor. But, do we have any other way?

In other words, what I need to insert to run t3 thread?

#include <thread>
#include <iostream>

void print(const char* s){
    while (true)
        std::cout << s <<'\n';
}

int main() {

    std::thread t1(print, "foo");
    std::thread *t2;
    t2 = new std::thread(print, "bar");
    std::thread t3; // Don't change this line
    // what I need to put here to run t3 ?

    t1.join();
    t2->join();
    t3.join();
    delete t2;
    return 0;
}

Kiskae · Accepted Answer · 2018-06-30 17:28:05Z

3

t3 is essentially a dummy thread. Looking at the reference the default constructor says:

Creates new thread object which does not represent a thread.

But since std::thread has operator=(std::thread&&) you can make it represent an actual thread by moving a new thread into the variable:

t3 = std::thread(print, "foobar");

This will create and launch a new thread, then assign it to t3.

edited Jun 30, 2018 at 17:28

answered Jun 30, 2018 at 17:03

Kiskae

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2 Comments

Stepan Loginov Over a year ago

And what actual difference between "use" or "don't use" std::move in this case?

Kiskae Over a year ago

Actually it is redundant. But I was looking at the documentation and tried to avoid invoking the copy constructor, so I just put in the std::move to be safe.

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