Backport into build-201102032246-5.1.52sp1

> ------------------------------------------------------------
> revno: 3517
> revision-id: sergey.glukhov@oracle.com-20101213103926-okypkn10adeeyns8
> parent: davi.arnaut@oracle.com-20101207150620-s49dstok48oy585o
> committer: Sergey Glukhov <sergey.glukhov@oracle.com>
> branch nick: mysql-5.1-bugteam
> timestamp: Mon 2010-12-13 13:39:26 +0300
> message:
>   Bug#58396 group_concat and explain extended are still crashy
>   Explain fails at fix_fields stage and some items are left unfixed,
>   particulary Item_group_concat. Item_group_concat::orig_args field
>   is uninitialized in this case and Item_group_concat::print call 
>   leads to crash.
>   The fix:
>   move the initialization of Item_group_concat::orig_args
>   into constructor.

mysql-test/r/func_gconcat.result

@@ -1029,4 +1029,16 @@ GROUP_CONCAT(t1.a ORDER BY t1.a)
 1,1,2,2
 DEALLOCATE PREPARE stmt;
 DROP TABLE t1;
+#
+# Bug#58396 group_concat and explain extended are still crashy
+#
+CREATE TABLE t1(a INT);
+EXPLAIN EXTENDED SELECT UPDATEXML('1', a, '1')
+FROM t1 ORDER BY (SELECT GROUP_CONCAT(1) FROM t1);
+ERROR HY000: Only constant XPATH queries are supported
+SHOW WARNINGS;
+Level	Code	Message
+Error	1105	Only constant XPATH queries are supported
+Note	1003	select updatexml('1',`test`.`t1`.`a`,'1') AS `UPDATEXML('1', a, '1')` from `test`.`t1` order by (select group_concat(1 separator ',') from `test`.`t1`)
+DROP TABLE t1;
 End of 5.1 tests

mysql-test/t/func_gconcat.test

@@ -734,4 +734,15 @@ EXECUTE stmt;
 DEALLOCATE PREPARE stmt;
 DROP TABLE t1;
 
+--echo #
+--echo # Bug#58396 group_concat and explain extended are still crashy
+--echo #
+
+CREATE TABLE t1(a INT);
+--error ER_UNKNOWN_ERROR
+EXPLAIN EXTENDED SELECT UPDATEXML('1', a, '1')
+FROM t1 ORDER BY (SELECT GROUP_CONCAT(1) FROM t1);
+SHOW WARNINGS;
+DROP TABLE t1;
+
 --echo End of 5.1 tests

sql/item_sum.cc

@@ -3003,6 +3003,7 @@ Item_func_group_concat(Name_resolution_context *context_arg,
       order_item->item= arg_ptr++;
     }
   }
+  memcpy(orig_args, args, sizeof(Item*) * arg_count);
 }
 
 
@@ -3233,7 +3234,6 @@ Item_func_group_concat::fix_fields(THD *thd, Item **ref)
   if (check_sum_func(thd, ref))
     return TRUE;
 
-  memcpy (orig_args, args, sizeof (Item *) * arg_count);
   fixed= 1;
   return FALSE;
 }