Add 5.0 part of fix for bug 17047.

mysql-test/r/func_str.result:
  Add result for bug#17047: CHAR() and IN() can return NULL without
  signaling NULL result.
mysql-test/t/func_str.test:
  Add test case for bug#17047: CHAR() and IN() can return NULL without
  signaling NULL result.
sql/item_strfunc.cc:
  Add Item_str_func::fix_fields() implementation, and set maybe_null to
  TRUE if we are in the SQL mode that requires some functions to return
  null even if they normally do not.
sql/item_strfunc.h:
  Add declaration of Item_str_func::fix_fields().
  Do not reset maybe_null in Item_func_char::fix_length_and_dec().

1 files changed, 3 insertions, 3 deletions

diff --git a/sql/item_strfunc.h b/sql/item_strfunc.h
index 528180b803d..fd2aaf19675 100644
--- a/sql/item_strfunc.h
+++ b/sql/item_strfunc.h
@@ -37,6 +37,7 @@ public:
   enum Item_result result_type () const { return STRING_RESULT; }
   void left_right_max_length();
   String *check_well_formed_result(String *str);
+  bool fix_fields(THD *thd, Item **ref);
 };
 
 class Item_func_md5 :public Item_str_func
@@ -525,9 +526,8 @@ public:
   { collation.set(cs); }  
   String *val_str(String *);
   void fix_length_and_dec() 
-  { 
-    maybe_null=0;
-    max_length=arg_count * collation.collation->mbmaxlen;
+  {
+    max_length= arg_count * collation.collation->mbmaxlen;
   }
   const char *func_name() const { return "char"; }
 };