revision of fix_fields() calls (BUG2838)

mysql-test/r/subselect.result:
  test suite for BUG#2838
mysql-test/t/subselect.test:
  test suite for BUG#2838
sql/item.cc:
  revision of fix_fields() calls
  removed unnecessary variabl, and used correct last parameter of fix_fields()
sql/item_cmpfunc.cc:
  revision of fix_fields() calls (BUG#2838)
sql/item_func.cc:
  revision of fix_fields() calls
sql/item_row.cc:
  changed for efficience (and to be similar for Item_func::fix_fields)
sql/item_subselect.cc:
  fixed last arguments for fix_fields call
sql/item_sum.cc:
  layout fixed
  revision of fix_fields() calls
sql/log_event.cc:
  revision of fix_fields() calls
sql/set_var.cc:
  revision of fix_fields() calls
sql/sql_base.cc:
  revision of fix_fields() calls
sql/sql_class.cc:
  revision of fix_fields() calls
sql/sql_handler.cc:
  revision of fix_fields() calls

1 files changed, 10 insertions, 8 deletions

diff --git a/sql/item_row.cc b/sql/item_row.cc
index 7f847bd1d4e..2b0cd38e3c1 100644
--- a/sql/item_row.cc
+++ b/sql/item_row.cc
@@ -62,19 +62,21 @@ bool Item_row::fix_fields(THD *thd, TABLE_LIST *tabl, Item **ref)
   {
     if ((*arg)->fix_fields(thd, tabl, arg))
       return 1;
-    used_tables_cache |= (*arg)->used_tables();
-    if (const_item_cache&= (*arg)->const_item() && !with_null)
+    // we can't assign 'item' before, because fix_fields() can change arg
+    Item *item= *arg;
+    used_tables_cache |= item->used_tables();
+    if (const_item_cache&= item->const_item() && !with_null)
     {
-      if ((*arg)->cols() > 1)
-	with_null|= (*arg)->null_inside();
+      if (item->cols() > 1)
+	with_null|= item->null_inside();
       else
       {
-	(*arg)->val_int();
-	with_null|= (*arg)->null_value;
+	item->val_int();
+	with_null|= item->null_value;
       }
     }
-    maybe_null|= (*arg)->maybe_null;
-    with_sum_func= with_sum_func || (*arg)->with_sum_func;
+    maybe_null|= item->maybe_null;
+    with_sum_func= with_sum_func || item->with_sum_func;
   }
   return 0;
 }