Bug#16119355:PREPARED STATEMENT: READ OF FREED MEMORY WITH STRING CONVERSION FUNCTIONS

Reverting fix for Bug#16119355 in 5.1 as this needs two patches 
from 5.5+ to work for a certain case

sql/item_func.h

@@ -1391,13 +1391,6 @@ public:
     :Item_func(b), cached_result_type(INT_RESULT),
      entry(NULL), entry_thread_id(0), name(a)
   {}
-  Item_func_set_user_var(THD *thd, Item_func_set_user_var *item)
-    :Item_func(thd, item), cached_result_type(item->cached_result_type),
-    entry(item->entry), entry_thread_id(item->entry_thread_id),
-    value(item->value), decimal_buff(item->decimal_buff),
-    null_item(item->null_item), save_result(item->save_result),
-    name(item->name)
-  {}
 
   enum Functype functype() const { return SUSERVAR_FUNC; }
   double val_real();

sql/sql_select.cc

@@ -15779,88 +15779,64 @@ change_to_use_tmp_fields(THD *thd, Item **ref_pointer_array,
   res_selected_fields.empty();
   res_all_fields.empty();
 
-  uint border= all_fields.elements - elements;
-  for (uint i= 0; (item= it++); i++)
+  uint i, border= all_fields.elements - elements;
+  for (i= 0; (item= it++); i++)
   {
     Field *field;
-    if (item->with_sum_func && item->type() != Item::SUM_FUNC_ITEM)
+
+    if ((item->with_sum_func && item->type() != Item::SUM_FUNC_ITEM) ||
+        (item->type() == Item::FUNC_ITEM &&
+         ((Item_func*)item)->functype() == Item_func::SUSERVAR_FUNC))
       item_field= item;
-    else if (item->type() == Item::FIELD_ITEM)
-      item_field= item->get_tmp_table_item(thd);
-    else if (item->type() == Item::FUNC_ITEM &&
-             ((Item_func*)item)->functype() == Item_func::SUSERVAR_FUNC)
+    else
     {
-      field= item->get_tmp_table_field();
-      if( field != NULL)
+      if (item->type() == Item::FIELD_ITEM)
       {
-        /*
-          Replace "@:=<expression>" with "@:=<tmp table column>". Otherwise, we
-          would re-evaluate <expression>, and if expression were a subquery, this
-          would access already-unlocked tables.
-         */
-        Item_func_set_user_var* suv=
-          new Item_func_set_user_var(thd, (Item_func_set_user_var*) item);
-        Item_field *new_field= new Item_field(field);
-        if (!suv || !new_field)
-          DBUG_RETURN(true);                  // Fatal error
-        /*
-         We are replacing the argument of Item_func_set_user_var after its value
-         has been read.  The argument's null_value should be set by now, so we
-         must set it explicitly for the replacement argument since the null_value
-         may be read without any preceeding call to val_*().
-        */
-        new_field->update_null_value();
-        List<Item> list;
-        list.push_back(new_field);
-        suv->set_arguments(list);
-        item_field= suv;
+        item_field= item->get_tmp_table_item(thd);
       }
-      else
-        item_field= item;
-    }
-    else if ((field= item->get_tmp_table_field()))
-    {
-      if (item->type() == Item::SUM_FUNC_ITEM && field->table->group)
-        item_field= ((Item_sum*) item)->result_item(field);
-      else
-        item_field= (Item*) new Item_field(field);
-      if (!item_field)
-        DBUG_RETURN(true);                    // Fatal error
-
-      if (item->real_item()->type() != Item::FIELD_ITEM)
-        field->orig_table= 0;
-      item_field->name= item->name;
-      if (item->type() == Item::REF_ITEM)
+      else if ((field= item->get_tmp_table_field()))
       {
-        Item_field *ifield= (Item_field *) item_field;
-        Item_ref *iref= (Item_ref *) item;
-        ifield->table_name= iref->table_name;
-        ifield->db_name= iref->db_name;
-      }
+        if (item->type() == Item::SUM_FUNC_ITEM && field->table->group)
+          item_field= ((Item_sum*) item)->result_item(field);
+        else
+          item_field= (Item*) new Item_field(field);
+        if (!item_field)
+          DBUG_RETURN(TRUE);                    // Fatal error
+
+        if (item->real_item()->type() != Item::FIELD_ITEM)
+          field->orig_table= 0;
+        item_field->name= item->name;
+        if (item->type() == Item::REF_ITEM)
+        {
+          Item_field *ifield= (Item_field *) item_field;
+          Item_ref *iref= (Item_ref *) item;
+          ifield->table_name= iref->table_name;
+          ifield->db_name= iref->db_name;
+        }
 #ifndef DBUG_OFF
-      if (!item_field->name)
-      {
-        char buff[256];
-        String str(buff,sizeof(buff),&my_charset_bin);
-        str.length(0);
-        item->print(&str, QT_ORDINARY);
-        item_field->name= sql_strmake(str.ptr(),str.length());
-      }
+        if (!item_field->name)
+        {
+          char buff[256];
+          String str(buff,sizeof(buff),&my_charset_bin);
+          str.length(0);
+          item->print(&str, QT_ORDINARY);
+          item_field->name= sql_strmake(str.ptr(),str.length());
+        }
 #endif
+      }
+      else
+        item_field= item;
     }
-    else
-      item_field= item;
-
     res_all_fields.push_back(item_field);
     ref_pointer_array[((i < border)? all_fields.elements-i-1 : i-border)]=
       item_field;
   }
 
   List_iterator_fast<Item> itr(res_all_fields);
-  for (uint i= 0; i < border; i++)
+  for (i= 0; i < border; i++)
     itr++;
   itr.sublist(res_selected_fields, elements);
-  DBUG_RETURN(false);
+  DBUG_RETURN(FALSE);
 }