qt how get out parameter of Stored Procedure?

could somebody tell me how to get out parameter of Stored Procedure
for example:

Code:

CREATE PROCEDURE `proc_userByAdd`(in_username varchar(20), in_password varchar(40), OUT out_result int) 
BEGIN 
DECLARE tmp_userid INT DEFAULT 0; 
DECLARE txn_error INT DEFAULT 0; 
DECLARE CONTINUE HANDLER FOR SQLEXCEPTION BEGIN 
SET txn_error=1; 
END; 
set out_result = 1; 
START TRANSACTION; 
insert into userinfo(username,password) values(in_username,in_password); 
IF txn_error THEN 
set out_result = 0; 
ROLLBACK ; 
END IF; 
select LAST_INSERT_ID() into tmp_userid; 
insert into user_role(roleid,userid) values(in_roleid,tmp_userid); 
IF txn_error THEN 
set out_result =0; 
ROLLBACK ; 
END IF; 
COMMIT; 
END

Code:

QSqlQuery query(db_tmp);
    int result = 1;
 
    query.prepare("call proc_userByAdd(?,?,?,?)");
    query.bindValue(0,username);
    query.bindValue(1,password);
    query.bindValue(2,roleid);
    query.bindValue(3,0,QSql::Out);
 
    if(!query.exec())
    {
        WRTLOG(tr("[DBERROR][USERMANAGE][addUser]%1\r\n[sql]%2").arg(query.lastError().text(),query.lastQuery()),DEBUG);
        result = 0;
    }
    else
    {
        result = query.boundValue(3).toInt();
    }