Best way for waiting for callback to finish

Question

In the code below, main() function is calling request() function which inter call th_request_async() function which mm_th_done_cb().

What will be the best and efficient

Answer 1

If C++11 is available,you can std::future

#include 
int main()
{
    request();
    std::future myFuture = std::async(mm_th_done_cb);
    //wait until mm_th_done_cb has been excuted;
    int result = myFuture.get();
}

or you can use synchronization mechanism.such as condition_variable,which is cross-platform.

#include 
std::mutex mtx;
std::condition_variable cv;
int mm_th_done_cb(int error_code, th_result_s* th_result, void* user_data)
{
    cv.notify_one();
    return 0;
}

int main()
{
    request();
    unique_lock lck(mtx);
    cv.wait(lck);
    return 0;
}