hi to all, I've centos 7.5 in VM, and having Qt5.7 in same VM.

I am trying to build some program, in this a class connDB having static method as follows :-
Qt Code: 
  1. QSqlDatabase * connDB::connectDB(QSqlDatabase *db, QString *uname, QString *passwd, QString *dbname, QString *host )
  2. {
  3.     db = new QSqlDatabase(QSqlDatabase::addDatabase("QMYSQL"));
  4.     db->setDatabaseName(*dbname);
  5.     db->setHostName(*host);
  6.     db->setUserName(*uname);
  7.     db->setPassword(*passwd);
  8.     db->setPort(3306);
  9.  
  10.     return db;
  11. }
To copy to clipboard, switch view to plain text mode 

now in a slot :-
Qt Code: 
  1. void MyMainWindow::on_pushButtonLogin_clicked()
  2. {
  3.     QString user = ui->lineEditUserName->text().trimmed();
  4.     QString passwd = ui->lineEditPassword->text().trimmed();
  5.     QString dbname = "cbs";
  6.     QString host = "serverora11gr2.db.net";
  7.  
  8.     db = connDB::connectDB(db, &user, &passwd, &dbname, &host);
  9.  
  10.     if(db->open())
  11.     {
  12.         QMessageBox::information(this, "Login", " Connection Succeeded");
  13.     }
  14.     else
  15.     {
  16.         QMessageBox::warning(this, "Login", "Coneection failure : " + db->lastError().text());
  17.     }
  18.  
  19.     db->close();
  20.     QSqlDatabase::removeDatabase(dbname);
  21.     delete db;
  22. }
To copy to clipboard, switch view to plain text mode 
when I tried to to run it is successfully runs but when i press login button more it shows following
QSqlDatabasePrivate::addDatabase: duplicate connection name 'qt_sql_default_connection', old connection removed.

how to overcome this problem.cbs login problem.jpg