add: free (utmp_buf);
context: who (const char *filename){  int n_users;  STRUCT_UTMP *utmp_buf;  int fail = read_utmp (filename, &n_users, &utmp_buf);  if (fail)    error (EXIT_FAILURE, errno, "%s", filename);  if (short_list)    list_entries_who (n_users, utmp_buf);  else    scan_entries (n_users, utmp_buf);}