In libev, why the default loop is on the stack?

Question

    int main()
    {
        struct ev_loop *loop1 = EV_DEFAULT;
        struct ev_loop *loop2 = ev_default_loop(0);
        printf("%ld\n%ld\n", (long)loop1, (long)loop2);
        return 0;
    }

Yes, loop1 is equal to loop2. But why are they both on the stack, not the heap? And, maybe ev_default_loop is like this,

    int* func()
    {
        int a;
        return &a;
    }

But after func returns, its stack has been cleaned up. So is it REALLY safe?

Answer 1

EV_DEFAULT might be a global variable, and ev_default_loop returns this variable as well. So, there're not on the stack.

Additional, you take a dangerous practice of return stack address for caller using.