Bug#41370: TIMESTAMP field does not accepts NULL from FROM_UNIXTIME()

When storing a NULL to a TIMESTAMP NOT NULL DEFAULT ...,
NULL returned from some functions threw a 'cannot be NULL error.'

NULL-returns now correctly result in the timestamp-field being
assigned its default value.

mysql-test/r/type_timestamp.result:
  Show that for TIMESTAMP NOT NULL DEFAULT, NULL function returns
  set default now.
mysql-test/t/type_timestamp.test:
  Show that for TIMESTAMP NOT NULL DEFAULT, NULL function returns
  set default now.
sql/item.cc:
  When storing a returned NULL (from a time- or date-related
  function), make sure to apply NULL-means-DEFAULT magic where
  applicable.

mysql-test/r/type_timestamp.result

@@ -492,6 +492,7 @@ a	b	c
 5	NULL	2001-09-09 04:46:59
 6	NULL	2006-06-06 06:06:06
 drop table t1;
+End of 4.1 tests
 set time_zone= @@global.time_zone;
 CREATE TABLE t1 (
 `id` int(11) NOT NULL auto_increment,
@@ -508,3 +509,21 @@ select is_nullable from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME='t1' and COL
 is_nullable
 NO
 drop table t1;
+CREATE TABLE t1 ( f1 INT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY,
+f2 TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+f3 TIMESTAMP);
+INSERT INTO t1 (f2,f3) VALUES (NOW(), "0000-00-00 00:00:00");
+INSERT INTO t1 (f2,f3) VALUES (NOW(), NULL);
+INSERT INTO t1 (f2,f3) VALUES (NOW(), ASCII(NULL));
+INSERT INTO t1 (f2,f3) VALUES (NOW(), FROM_UNIXTIME('9999999999'));
+INSERT INTO t1 (f2,f3) VALUES (NOW(), TIME(NULL));
+UPDATE t1 SET f2=NOW(), f3=FROM_UNIXTIME('9999999999') WHERE f1=1;
+SELECT f1,f2-f3 FROM t1;
+f1	f2-f3
+1	0
+2	0
+3	0
+4	0
+5	0
+DROP TABLE t1;
+End of 5.0 tests

mysql-test/t/type_timestamp.test

@@ -324,7 +324,7 @@ insert into t1 (a, c) values (4, '2004-04-04 00:00:00'),
 select * from t1;
 drop table t1;
 
-# End of 4.1 tests
+--echo End of 4.1 tests
 
 # Restore timezone to default
 set time_zone= @@global.time_zone;
@@ -339,3 +339,21 @@ PRIMARY KEY (`id`)
 show fields from t1;
 select is_nullable from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME='t1' and COLUMN_NAME='posted_on';
 drop table t1;
+
+#
+# Bug#41370: TIMESTAMP field does not accepts NULL from FROM_UNIXTIME()
+#
+
+CREATE TABLE t1 ( f1 INT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY,
+                  f2 TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+                  f3 TIMESTAMP);
+INSERT INTO t1 (f2,f3) VALUES (NOW(), "0000-00-00 00:00:00");
+INSERT INTO t1 (f2,f3) VALUES (NOW(), NULL);
+INSERT INTO t1 (f2,f3) VALUES (NOW(), ASCII(NULL));
+INSERT INTO t1 (f2,f3) VALUES (NOW(), FROM_UNIXTIME('9999999999'));
+INSERT INTO t1 (f2,f3) VALUES (NOW(), TIME(NULL));
+UPDATE t1 SET f2=NOW(), f3=FROM_UNIXTIME('9999999999') WHERE f1=1;
+SELECT f1,f2-f3 FROM t1;
+DROP TABLE t1;
+
+--echo End of 5.0 tests

sql/item.cc

@@ -321,7 +321,7 @@ int Item::save_time_in_field(Field *field)
 {
   MYSQL_TIME ltime;
   if (get_time(&ltime))
-    return set_field_to_null(field);
+    return set_field_to_null_with_conversions(field, 0);
   field->set_notnull();
   return field->store_time(&ltime, MYSQL_TIMESTAMP_TIME);
 }
@@ -331,7 +331,7 @@ int Item::save_date_in_field(Field *field)
 {
   MYSQL_TIME ltime;
   if (get_date(&ltime, TIME_FUZZY_DATE))
-    return set_field_to_null(field);
+    return set_field_to_null_with_conversions(field, 0);
   field->set_notnull();
   return field->store_time(&ltime, MYSQL_TIMESTAMP_DATETIME);
 }