C++ atomic_flag query state

Question

I am using C++ std::atomic_flag as an atomic Boolean flag. Setting the flag to true or false is not a problem but how to query the current state of flag without

Answer 1

If you want to use atomic_flag to determine whether a thread should exit, you can do it like this:

Initialization:

std::atomic_flag keep_running = ATOMIC_FLAG_INIT;
keep_running.test_and_set();

Thread loop:

while (keep_running.test_and_set()) {
    // do thread stuff
}

When you want the thread to exit:

keep_running.clear();