Bug#11765216 58154: UNINITIALIZED VARIABLE FORMAT IN STR_TO_DATE FUNCTION

Valgrind warning happens due to uninitialized cached_format_type field
which is used later in Item_func_str_to_date::val_str method.
The fix is to init cached_format_type field.

mysql-test/r/func_time.result

@@ -1381,4 +1381,10 @@ DROP TABLE t1;
 SELECT STR_TO_DATE(SPACE(2),'1');
 STR_TO_DATE(SPACE(2),'1')
 0000-00-00
+#
+# Bug#11765216  58154: UNINITIALIZED VARIABLE FORMAT IN STR_TO_DATE FUNCTION
+#
+SET GLOBAL SQL_MODE='';
+DO  STR_TO_DATE((''), FROM_DAYS(@@GLOBAL.SQL_MODE));
+SET GLOBAL SQL_MODE=DEFAULT;
 End of 5.1 tests

mysql-test/t/func_time.test

@@ -887,4 +887,12 @@ DROP TABLE t1;
 
 SELECT STR_TO_DATE(SPACE(2),'1');
 
+--echo #
+--echo # Bug#11765216  58154: UNINITIALIZED VARIABLE FORMAT IN STR_TO_DATE FUNCTION
+--echo #
+
+SET GLOBAL SQL_MODE='';
+DO  STR_TO_DATE((''), FROM_DAYS(@@GLOBAL.SQL_MODE));
+SET GLOBAL SQL_MODE=DEFAULT;
+
 --echo End of 5.1 tests

sql/item_timefunc.cc

@@ -3293,6 +3293,7 @@ void Item_func_str_to_date::fix_length_and_dec()
 {
   maybe_null= 1;
   decimals=0;
+  cached_format_type= DATE_TIME;
   cached_field_type= MYSQL_TYPE_DATETIME;
   max_length= MAX_DATETIME_FULL_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
   cached_timestamp_type= MYSQL_TIMESTAMP_NONE;