Manual merge of fix for bug #6439 "from_unixtime() function returns

wrong datetime values for too big argument" from 4.0 tree to 4.1 tree.

mysql-test/r/func_time.result

@@ -474,6 +474,12 @@ unix_timestamp(@a)
 select unix_timestamp('1969-12-01 19:00:01');
 unix_timestamp('1969-12-01 19:00:01')
 0
+select from_unixtime(0);
+from_unixtime(0)
+NULL
+select from_unixtime(2145916800);
+from_unixtime(2145916800)
+NULL
 CREATE TABLE t1 (datetime datetime, timestamp timestamp, date date, time time);
 INSERT INTO t1 values ("2001-01-02 03:04:05", "2002-01-02 03:04:05", "2003-01-02", "06:07:08");
 SELECT * from t1;

mysql-test/t/func_time.test

@@ -229,6 +229,13 @@ select @a:=FROM_UNIXTIME(1);
 select unix_timestamp(@a);
 select unix_timestamp('1969-12-01 19:00:01');
 
+#
+# Test for bug #6439 "unix_timestamp() function returns wrong datetime 
+# values for too big argument". It should return error instead.
+#
+select from_unixtime(0);
+select from_unixtime(2145916800);
+
 #
 # Test types from + INTERVAL
 #

sql/item_timefunc.cc

@@ -1601,50 +1601,46 @@ void Item_func_from_unixtime::fix_length_and_dec()
 String *Item_func_from_unixtime::val_str(String *str)
 {
   TIME time_tmp;
-  my_time_t tmp;
-  
+
   DBUG_ASSERT(fixed == 1);
-  tmp= (time_t) args[0]->val_int();
-  if ((null_value=args[0]->null_value))
-    goto null_date;
-  
-  thd->variables.time_zone->gmt_sec_to_TIME(&time_tmp, tmp);
-  
+
+  if (get_date(&time_tmp, 0))
+    return 0;
+
   if (str->alloc(20*MY_CHARSET_BIN_MB_MAXLEN))
-    goto null_date;
+  {
+    null_value= 1;
+    return 0;
+  }
+
   make_datetime((DATE_TIME_FORMAT *) 0, &time_tmp, str);
   return str;
-
-null_date:
-  null_value=1;
-  return 0;
 }
 
 
 longlong Item_func_from_unixtime::val_int()
 {
   TIME time_tmp;
-  my_time_t tmp;
-  
+
   DBUG_ASSERT(fixed == 1);
 
-  tmp= (time_t) (ulong) args[0]->val_int();
-  if ((null_value=args[0]->null_value))
+  if (get_date(&time_tmp, 0))
     return 0;
-  
-  current_thd->variables.time_zone->gmt_sec_to_TIME(&time_tmp, tmp);
-  
+
   return (longlong) TIME_to_ulonglong_datetime(&time_tmp);
 }
 
 bool Item_func_from_unixtime::get_date(TIME *ltime,
 				       uint fuzzy_date __attribute__((unused)))
 {
-  my_time_t tmp=(my_time_t) args[0]->val_int();
-  if ((null_value=args[0]->null_value))
+  longlong tmp= args[0]->val_int();
+
+  if ((null_value= (args[0]->null_value ||
+                    tmp < TIMESTAMP_MIN_VALUE ||
+                    tmp > TIMESTAMP_MAX_VALUE)))
     return 1;
-  
-  current_thd->variables.time_zone->gmt_sec_to_TIME(ltime, tmp);
+
+  thd->variables.time_zone->gmt_sec_to_TIME(ltime, (my_time_t)tmp);
 
   return 0;
 }