max_n_num = tipc_highest_allowed_slave;
        assert(n_num > 0);
        assert(n_num <= max_n_num);
-       assert(c_ptr->nodes[n_num] == 0);
+       assert(c_ptr->nodes[n_num] == NULL);
        c_ptr->nodes[n_num] = n_ptr;
        if (n_num > c_ptr->highest_node)
                c_ptr->highest_node = n_num;
 
                if ((mod(msg_seqno(buf_msg(l_ptr->last_out)) -
                         msg_seqno(buf_msg(l_ptr->first_out)))
                     != (l_ptr->out_queue_size - 1))
-                   || (l_ptr->last_out->next != 0)) {
+                   || (l_ptr->last_out->next != NULL)) {
                        tipc_printf(buf, "\nSend queue inconsistency\n");
                        tipc_printf(buf, "first_out= %x ", l_ptr->first_out);
                        tipc_printf(buf, "next_out= %x ", l_ptr->next_out);
 
                reference = (next_plus_upper & ~index_mask) + index;
                entry->data.reference = reference;
                entry->object = object;
-               if (lock != 0)
+               if (lock != NULL)
                        *lock = &entry->lock;
                spin_unlock_bh(&entry->lock);
        }
 
 
        assert(c_ptr->addr);
        assert(c_num <= tipc_max_clusters);
-       assert(z_ptr->clusters[c_num] == 0);
+       assert(z_ptr->clusters[c_num] == NULL);
        z_ptr->clusters[c_num] = c_ptr;
 }