title: pointer "value computed is not used" in c function
body: <p>I wrote a function that that shortens a string (sentence of words) at requested length. I do not want that a the cut of the sentence happens to be in middle of a single word. So i skip back n chars until I reach a space and cut the sentence string there.
  My problem is not really a problem, compiling my function spits out a warning that says "warning: value computed is not used", see the commented line in the code. The function works as expected though.
  So either I am blind, or I am sitting to long on my project, actually I do not understand that warning. Could anybody please point me the flaw in the function?</p>
  
  <pre><code>
  char *
  str_cut(char *s, size_t len) {
      char *p = NULL;
      int n = 3;
  
      p = s + len;
      if (p &lt; (s + strlen (s))) {
          /*
           * do not cut string in middle of a word.
           * if cut-point is no space, reducue string until space reached ...
           */
          if (*p != ' ')
              while (*p != ' ')
                  *p--;   // TODO: triggers warning: warning: value computed is not used
  
          /* add space for dots and extra space, terminate string */
          p += n + 1;
          *p = '\0';
  
          /* append dots */
          while (n-- && (--p > s))
              *p = '.';
      }
      return s;
  }
  
  </code></pre>
  
  <p>My compiler on the development machine is "gcc version 4.2.4 (Ubuntu 4.2.4-1ubuntu4)"</p>