Fix #67976: cal_days_month() fails for final month of the French calendar

The French calendar ends on 0014-13-05, so trying to calculate the Julian
day of 0015-01-01 fails. We cater to that by returning the hard-coded value.

NEWS

@@ -11,6 +11,10 @@ PHP                                                                        NEWS
   . Fixed bug #72641 (phpize (on Windows) ignores PHP_PREFIX).
     (Yuji Uchiyama)
 
+- Calendar:
+  . Fixed bug #67976 (cal_days_month() fails for final month of the French
+    calendar). (cmb)
+
 - Curl:
   . Fixed bug #71144 (Segmentation fault when using cURL with ZTS).
     (maroszek at gmx dot net)

ext/calendar/calendar.c

@@ -359,6 +359,10 @@ PHP_FUNCTION(cal_days_in_month)
 		}
 		else {
 			sdn_next = calendar->to_jd(year + 1, 1, 1);
+			if (cal == CAL_FRENCH && sdn_next == 0) {
+				/* The French calendar ends on 0014-13-05. */
+				sdn_next = 2380953;
+			}
 		}
 	}
 

ext/calendar/tests/bug67976.phpt

@@ -0,0 +1,12 @@
+--TEST--
+Bug #67976 (cal_days_month() fails for final month of the French calendar)
+--SKIPIF--
+<?php
+if (!extension_loaded('calendar')) die('skip ext/calendar required');
+?>
+--FILE--
+<?php
+var_dump(cal_days_in_month(CAL_FRENCH, 13, 14));
+?>
+--EXPECT--
+int(5)