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

the Epoch". (With after review fixes).

2 files changed, 7 insertions, 6 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);
diff --git a/sql/item_timefunc.h b/sql/item_timefunc.h
index e04e24627d9..8ee2f935a80 100644
--- a/sql/item_timefunc.h
+++ b/sql/item_timefunc.h
@@ -359,8 +359,7 @@ class Item_func_from_unixtime :public Item_date_func
   longlong val_int();
   String *val_str(String *str);
   const char *func_name() const { return "from_unixtime"; }
-  void fix_length_and_dec() { decimals=0; max_length=19; }
-//  enum Item_result result_type () const { return STRING_RESULT; }
+  void fix_length_and_dec() { decimals=0; max_length=19; maybe_null= 1; }
   bool get_date(TIME *res,bool fuzzy_date);
 };