cal: fix --span for large numbers of months

The need to calculate with whole years when go back for --span.

Addresses: https://github.com/karelzak/util-linux/issues/677
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/misc-utils/cal.c b/misc-utils/cal.c
index acbcf5005e8b56ef1087842ae0669159305eecd3..4dff491fb63ba3adcbc699e0a48bfbb03810c872 100644 (file)
--- a/misc-utils/cal.c
+++ b/misc-utils/cal.c
@@ -840,17 +840,20 @@ static void cal_output_months(struct cal_month *month, const struct cal_control
 static void monthly(const struct cal_control *ctl)
 {
        struct cal_month m1,m2,m3, *m;
-       int i, rows, new_month, month = ctl->req.start_month ? ctl->req.start_month : ctl->req.month;
+       int i, rows, month = ctl->req.start_month ? ctl->req.start_month : ctl->req.month;
        int32_t year = ctl->req.year;
 
        /* cal -3, cal -Y --span, etc. */
        if (ctl->span_months) {
-               new_month = month - ctl->num_months / 2;
+               int new_month = month - ctl->num_months / 2;
                if (new_month < 1) {
-                       month = new_month + MONTHS_IN_YEAR;
-                       year--;
-               }
-               else
+                       new_month *= -1;
+                       year -= (new_month / MONTHS_IN_YEAR) + 1;
+
+                       if (new_month > MONTHS_IN_YEAR)
+                               new_month %= MONTHS_IN_YEAR;
+                       month = MONTHS_IN_YEAR - new_month;
+               } else
                        month = new_month;
        }