662: Mainline

The check_owner function, defined next, exhibits a railroad_car parameter, a character-pointer parameter, and an integer return value, which is either 0 or 1 depending on whether the car belongs to the railroad specified by the character-pointer parameter. Note that the check_owner function uses strncmp, a function supplied by the string-handling library, which tests two strings to see whether a specified number of initial characters in the two strings are the same:

// DANGEROUS; contributes to difficult-to-find bug: 
int check_owner (railroad_car r, char *s) { 
  if (strncmp (s, r.serial_number, 3)) 
    return 0; 
  else 
    return 1; 
}