Method pop_front

thread/thread.cpp:391–404

        }

        thread* pop_front()
        {
            auto ret = q[0];
            if (q.size() == 1) {
                q.pop_back();
                return ret;
            }
            q[0] = q.back();
            q[0]->idx = 0;
            q.pop_back();
            down(0);
            ret->idx = -1;
            return ret;
        }

        int pop(thread *obj)
        {