Merge rkalimullin@bk-internal.mysql.com:/home/bk/mysql-5.0-maint

into  mysql.com:/usr/home/ram/work/bug23653/my50-bug23653

mysql-test/r/func_time.result

@@ -1047,6 +1047,9 @@ union
 (select time_format(timediff(now(), DATE_SUB(now(),INTERVAL 5 HOUR)),'%k') As H);
 H
 5
+select last_day('0000-00-00');
+last_day('0000-00-00')
+NULL
 End of 4.1 tests
 explain extended select timestampdiff(SQL_TSI_WEEK, '2001-02-01', '2001-05-01') as a1,
 timestampdiff(SQL_TSI_FRAC_SECOND, '2001-02-01 12:59:59.120000', '2001-05-01 12:58:58.119999') as a2;

mysql-test/t/func_time.test

@@ -564,6 +564,12 @@ union
 union
 (select time_format(timediff(now(), DATE_SUB(now(),INTERVAL 5 HOUR)),'%k') As H);
 
+#
+# Bug #23653: crash if last_day('0000-00-00')
+#
+
+select last_day('0000-00-00');
+
 --echo End of 4.1 tests
 
 explain extended select timestampdiff(SQL_TSI_WEEK, '2001-02-01', '2001-05-01') as a1,

sql/item_timefunc.cc

@@ -3369,7 +3369,8 @@ String *Item_func_str_to_date::val_str(String *str)
 
 bool Item_func_last_day::get_date(TIME *ltime, uint fuzzy_date)
 {
-  if (get_arg0_date(ltime, fuzzy_date & ~TIME_FUZZY_DATE))
+  if (get_arg0_date(ltime, fuzzy_date & ~TIME_FUZZY_DATE) ||
+      (ltime->month == 0))
     return 1;
   uint month_idx= ltime->month-1;
   ltime->day= days_in_month[month_idx];