title: calculate the length of string by the function of strlen
body: <pre><code>  char arr[]={'a','b','c'};
    int len=strlen(arr);
  </code></pre>
  <p>I know that when the pointer of char meet the address of <code>'0'</code>, this function would stop running and return the length between the array's first address and the address of <code>'0'</code>.
  But when I created one string by that way, I didn't put <code>'0'</code>. So the pointer of char maybe
  keep moving to find the address of <code>'0'</code>. In this process , the pointer maybe made a error about out-of-bounds access.
  So why this code didn't make warn to me or why this code didn't make error?</p>