Bug#19136: Manual 5.0->5.1 merge

sql/item_func.cc:
  Auto merged
sql/sql_select.cc:
  Auto merged

mysql-test/r/rpl_user_variables.result

@@ -78,5 +78,6 @@ abcn1
 abcn1n2
 abc\def
 This is a test
+insert into t1 select * FROM (select @var1 union  select @var2) AS t2;
 drop table t1;
 stop slave;

mysql-test/t/rpl_user_variables.test

@@ -55,6 +55,7 @@ SELECT * FROM t1 ORDER BY n;
 sync_slave_with_master;
 SELECT * FROM t1 ORDER BY n;
 connection master;
+insert into t1 select * FROM (select @var1 union  select @var2) AS t2;
 drop table t1;
 sync_slave_with_master;
 stop slave;

sql/item_func.cc

@@ -3948,14 +3948,24 @@ int get_var_with_binlog(THD *thd, enum_sql_command sql_command,
       sql_set_variables(), we could instead manually call check() and update();
       this would save memory and time; but calling sql_set_variables() makes
       one unique place to maintain (sql_set_variables()). 
+
+      Manipulation with lex is necessary since free_underlaid_joins
+      is going to release memory belonging to the main query.
     */
 
     List<set_var_base> tmp_var_list;
+    LEX *sav_lex= thd->lex, lex_tmp;
+    thd->lex= &lex_tmp;
+    lex_start(thd, NULL, 0);
     tmp_var_list.push_back(new set_var_user(new Item_func_set_user_var(name,
                                                                        new Item_null())));
     /* Create the variable */
     if (sql_set_variables(thd, &tmp_var_list))
+    {
+      thd->lex= sav_lex;
       goto err;
+    }
+    thd->lex= sav_lex;
     if (!(var_entry= get_variable(&thd->user_vars, name, 0)))
       goto err;
   }