Edit report at http://bugs.php.net/bug.php?id=52744&edit=1
ID: 52744
Updated by: ahar...@php.net
Reported by: gpap at internet dot gr
Summary: cal_days_in_month
-Status: Open
+Status: Assigned
Type: Bug
Package: Calendar related
Operating System: all
PHP Version: 5.3SVN-2010-08-30 (snap)
-Assigned To:
+Assigned To: aharvey
Block user comment: N
Previous Comments:
------------------------------------------------------------------------
[2010-08-30 18:16:53] gpap at internet dot gr
Description:
------------
Function cal_days_in_month returns wrong result for December 1 BCE:
echo cal_days_in_month(CAL_GREGORIAN, 12, -1) returns -1721395
echo cal_days_in_month(CAL_JULIAN, 12, -1) returns -1721393
The function uses julian day count internally to calculate the day count
difference between the 1st day of the supplied month and the 1st day of
the next
month. The next month of December 1 BCE (year -1) is January 1 CE (year
1, there
is no year zero).
But when cal_days_in_month calculates the next year as year+1, it does
not check
for year zero, so it tries to calculate the julian day for 1st January
0, which
returns 0 and consequently the wrong result of days in December 1 BCE is
returned.
actual function code taken from latest svn snapshot php5.3-201008301230
(/ext/calendar.c):
-----------------------
PHP_FUNCTION(cal_days_in_month)
{
long cal, month, year;
struct cal_entry_t *calendar;
long sdn_start, sdn_next;
if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "lll",
&cal,
&month, &year) == FAILURE) {
RETURN_FALSE;
}
if (cal < 0 || cal >= CAL_NUM_CALS) {
php_error_docref(NULL TSRMLS_CC, E_WARNING, "invalid
calendar ID
%ld.", cal);
RETURN_FALSE;
}
calendar = &cal_conversion_table[cal];
sdn_start = calendar->to_jd(year, month, 1);
if (sdn_start == 0) {
php_error_docref(NULL TSRMLS_CC, E_WARNING, "invalid
date.");
RETURN_FALSE;
}
sdn_next = calendar->to_jd(year, 1 + month, 1);
if (sdn_next == 0) {
/* if invalid, try first month of the next year... */
sdn_next = calendar->to_jd(year + 1, 1, 1);
}
RETURN_LONG(sdn_next - sdn_start);
}
-----------------------
The following correction is proposed:
-----------------------
if (sdn_next == 0) {
/* if invalid, try first month of the next year... */
- sdn_next = calendar->to_jd(year + 1, 1, 1);
+ if (year == -1) {
+ sdn_next = calendar->to_jd(1, 1, 1);
+ } else {
+ sdn_next = calendar->to_jd(year + 1, 1, 1);
+ }
}
-----------------------
Test script:
---------------
<?php
// returns -1721395 instead of 31
echo cal_days_in_month(CAL_GREGORIAN, 12, -1);
// returns -1721393 instead of 31
echo cal_days_in_month(CAL_JULIAN, 12, -1);
?>
Expected result:
----------------
31
31
Actual result:
--------------
-1721395
-1721393
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/bug.php?id=52744&edit=1
