title: Why this line make my program segfault?
body: <p>I cut useless part of my code to make my post clearer.</p>
  
  <p>Here is the problem, the first and only line in the function <code>init_dda()</code> make my programme segfault, I really don't understand how is it possible, if you have an explanation, thanks to you.</p>
  
  <pre><code>void    dda_algorithm(t_env *e)
  {
      t_dda   *d;
  
      d = NULL;
      init_dda(e, d);
  }
  
  void    init_dda(t_env *e, t_dda *d)
  {
      d-&gt;map_x = 3;
  }
  </code></pre>
  
  <p>Here is the construction of my structure <code>t_dda</code>:</p>
  
  <pre><code>typedef struct  s_dda
  {
      int         map_x;
  }               t_dda;
  </code></pre>
  
  <p>I have no compilation error with warning flags enabled.</p>