title: Concatenating string with itself two times give segmentation fault
body: <pre><code>#include &lt;stdio.h&gt;
  
  int main(void)
  {
      char a[100] = "hi";
  
      strcat(a, a);
      strcat(a, a);
  
      printf("%s\n", a);
  
      return 0;
  }
  </code></pre>