title: Modify argument without return
body: <p>I have a problem in C. I have this function :</p>
  
  <pre><code>int test(void *data);
  </code></pre>
  
  <p>I want to change <em>data</em> with this function but I don't want another prototype (not use void **). Actualy, data equals null out this function.</p>
  
  <pre><code>#include &lt;stdio.h&gt;
  #include &lt;stdlib.h&gt;
  
  int
  test(void *data)
  {
    data = "toto";
  
    return 1;
  }
  
  int
  main()
  {
    void *d;
  
    if (test(d) != 1) {
      printf("erreur\n");
    }
  
    printf("résultat : %s\n", (char *) d); // displays "résultat : (null)"
  
    return 0;
  }
  </code></pre>
  
  <p>Help me please. ;)</p>