problem manipulating strings

From: Pink Floyd (
Date: 08/01/95

I'm not too experienced with C, and I am having a problem with strings/pointers
that I can't figure out. in limits.c, this is part of the function set_title :

void set_title(struct char_data * ch, char *title)
  if (title == NULL) {
    title = READ_TITLE(ch);
    if ((GET_CLASS(ch) == CLASS_PALADIN) && (GET_LEVEL(ch) == 10)
     /* this next line causes the Segmentation fault */
      strcat(title, "some string");
    /* "some string" is actually a macro that returns a string, but I
       tested the macro independently and it works fine */
   /* if the 'if (GET_CLASS)...' check above fails, it makes it here fine */
  if (strlen(title) > MAX_TITLE_LENGTH)
    title[MAX_TITLE_LENGTH] = '\0';
  if (GET_TITLE(ch) != NULL)

  GET_TITLE(ch) = str_dup(title); /* this might be some clue to my misuse 
                                     of title or strcat() */

I kinda have an idea of why its crashing, but I can't really tell exactly
why.  I get the feeling that if I learn the solution to this problem it will
be a big step in my understanding of pointers...  
Thanks in advance for your help!

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