std::async is not working in c++11, linux platform

Question

bool tf()
{
    sleep(5000);
    return true;
}

int main()
{
    std::future<bool> bb = std::async(std::launch::async, tf);
    bool b = false;
    while(1)
    {   
        if(b == true) break;

        b = bb.get();
    }   

    return 0;
}

why don't work? I intended to terminate program after 5 seconds. However, the program is freezing.

`sleep` take parameter in seconds. So your program goes to sleep for `500` seconds. Probably you mean `usleep`. — Konstantin T., Nov 22 '18 at 08:22
As an aside: `bb.get()` will block your main thread until the future is completed or ruined. It does not make sense to call this method in a loop. — Botje, Nov 22 '18 at 08:26
Related: https://stackoverflow.com/questions/1658386/sleep-function-in-c — Hulk, Nov 22 '18 at 08:33

score 0 · Answer 1 · edited Nov 22 '18 at 10:48

There is a much better alternative to the direct use of invoking a global sleep. Use the <chrono> header and the string literals it provides together with std::this_thread::sleep_for. This is less error prone, e.g.

#include <chrono>

// Bring the literals into the scope:
using namespace std::chrono_literals;

bool tf()
{
   std::this_thread::sleep_for(5s);
   //                          ^^ Awesome! How readable is this?!

   return true;
}

Together with the rest of the snippet you posted, this should work as intended.

std::async is not working in c++11, linux platform

1 Answers1