Fix for bug #7515 "from_unixtime(0) now returns NULL instead of

the Epoch". (With after review fixes).


mysql-test/r/func_time.result:
  Added test for bug #7515 "from_unixtime(0) now returns NULL instead of
  the Epoch".
mysql-test/t/func_time.test:
  Added test for bug #7515 "from_unixtime(0) now returns NULL instead of
  the Epoch".
sql/item_timefunc.cc:
  Item_func_from_unixtime:
   from_unixtime(0) should return Epoch instead of NULL.
sql/item_timefunc.h:
  Item_func_from_unixtime:
   - Removed unused method definition.
   - fix_length_and_dec() should set maybe_null to true since now
     from_unixtime() can return NULL even in case when none of its
     arguments is NULL.

1 files changed, 6 insertions, 4 deletions

diff --git a/sql/item_timefunc.cc b/sql/item_timefunc.cc
index d188310be24..b03fd151383 100644
--- a/sql/item_timefunc.cc
+++ b/sql/item_timefunc.cc
@@ -946,10 +946,12 @@ bool Item_func_from_unixtime::get_date(TIME *ltime,
 {
   struct tm tm_tmp;
   time_t tmp;
-  longlong arg= args[0]->val_int();
-  if ((null_value= (args[0]->null_value ||
-                    arg < TIMESTAMP_MIN_VALUE ||
-                    arg > TIMESTAMP_MAX_VALUE)))
+  ulonglong arg= (ulonglong)(args[0]->val_int());
+  /*
+    "arg > TIMESTAMP_MAX_VALUE" check also covers case of negative
+    from_unixtime() argument since arg is unsigned.
+  */
+  if ((null_value= (args[0]->null_value || arg > TIMESTAMP_MAX_VALUE)))
     return 1;
   tmp= arg;
   localtime_r(&tmp,&tm_tmp);