rem: printf (print_fmt, line_no); fputs (separator_str, stdout); line_no += page_incr;
add: intmax_t next_line_no;  printf (lineno_format, lineno_width, line_no, separator_str);  next_line_no = line_no + page_incr; if (next_line_no < line_no) error (EXIT_FAILURE, 0, _("line number overflow")); line_no = next_line_no;
context: print_lineno (void){  printf (print_fmt, line_no);  fputs (separator_str, stdout);  line_no += page_incr;}