title: passing argument 1 of 'strlen' differ in signedness
body: <p>I use <code>strlen()</code> call all over my project, until now I compiled my project without <code>-Wall</code> compiler option. But when I start using <code>-Wall</code> I face so many compiler warning. 80% are the strlen <code>char *</code> vs <code>const char *</code> warning.</p>
  <p>I am aware of type casting all <code>strlen()</code> calls.  Is there any other way that I can suppress the following warning?</p>
  <pre><code>./Proj.c:3126: warning: pointer targets in passing argument 1 of 
      'strlen' differ in signedness`
  
  C:/staging/usr/include/string.h:397: note: expected 'const char *' but 
      argument is of type 'unsigned char *'`
  </code></pre>