title: Warning/error "function declaration isn't a prototype"
body: <p>I have a library I created,</p>
  <h3>File <em>mylib.c:</em></h3>
  <pre><code>#include &lt;mylib.h&gt;
  
  int
  testlib() {
      printf(&quot;Hello, World!\n&quot;);
      return (0);
  }
  </code></pre>
  <h3>File <em>mylib.h:</em></h3>
  <pre><code>#include &lt;stdio.h&gt;
  extern int testlib();
  </code></pre>
  <p>In my program, I've attempted to call this library function:</p>
  <h3>File <em>myprogram.c</em>:</h3>
  <pre><code>#include &lt;mylib.h&gt;
  
  int
  main (int argc, char *argv[]) {
      testlib();
      return (0);
  }
  </code></pre>
  <p>When I attempt to compile this program I get the following error:</p>
  <pre>In file included from myprogram.c:1
  mylib.h:2 warning: function declaration isn't a prototype</pre>
  <p>I'm using: <code>gcc (GCC) 3.4.5 20051201 (Red Hat 3.4.5-2)</code></p>
  <p>What is the proper way to declare a function prototype?</p>