title: Warning: parameter names (without types) in function declaration
body: <p>Rookie question FYI. </p>
  
  <p>Whenever I compile/run the code, <strong>extern tolayer2(rtpktTo1);</strong> I receive a warning.
  The warning reads, as in the title, <em>Warning: parameter names (without types) in function declaration</em></p>
  
  <p>Any help appreciated. </p>
  
  <p>node0.c </p>
  
  <pre><code>extern struct rtpkt {
    int sourceid;       /* id of sending router sending this pkt */
    int destid;         /* id of router to which pkt being sent 
                           (must be an immediate neighbor) */
    int mincost[4];    /* current understanding of min cost to node 0 ... 3 */
    };
  
  /* Create routing packets (rtpkt) and send to neighbors via tolayer2(). */
      struct rtpkt rtpktTo1;
          rtpktTo1.sourceid = 0;
          rtpktTo1.destid = 1;
          rtpktTo1.mincost[0] = minCost[0];
          rtpktTo1.mincost[1] = minCost[1];
          rtpktTo1.mincost[2] = minCost[2];
          rtpktTo1.mincost[3] = minCost[3];
  
  extern tolayer2(rtpktTo1);
  </code></pre>
  
  <p>prog3.c </p>
  
  <pre><code>tolayer2(packet)
    struct rtpkt packet;
  {
    /* This has a lot of code in it */ 
  }
  </code></pre>