c++ - Workaround for blocking async?

Question

The async call below is blocking because the destructor of the returned future is blocking:

void foo() {}

void foo_async() {
    std::async(std::launch::async, foo);
}

But I don't want to block!

I'm considering to use the following workaround:

void foo_async() {
    std::thread(foo).detach();
}

Is this ok? Or would you recommend a different solution?

Answer 1

You could use the following version of async which provides a non-blocking future. As such you can take advantage of the future if you need it and on the other side you can just ignore it when you want a fire-and-forget task.

template< class Function, class... Args>
std::future<typename std::result_of<Function(Args...)>::type> async( Function&& f, Args&&... args ) 
{
    typedef typename std::result_of<Function(Args...)>::type R;
    auto bound_task = std::bind(std::forward<Function>(f), std::forward<Args>(args)...);
    std::packaged_task<R()> task(std::move(bound_task));
    auto ret = task.get_future();
    std::thread t(std::move(task));
    t.detach();
    return ret;   
}