Hazme un menú de login recursivo

void login(){
    string username;
    string password;
    cout << " username:";
    cin >> username;
    cout << "password:";
    cin >> password;
    if (username == "" || password == ""){
        cout << "You have to enter your username and password!" << endl;
        login();
    }else{
        cout << "Welcome!" << endl;
    }
}