Starting QT Application - c++

Question

I want to start my QT6 Application, but got exit code 139 (interrupted by signal 11: SIGSEGV).
Login extends QMainWindow with the following code in the main.cpp:
#include <QApplication>
#include <QPushButton>
#include "Login.h"
int main(int argc, char *argv[]) {
QApplication a(argc, argv);
auto login = new Login();
a.setActiveWindow(login);
login->show();
return a.exec();//QApplication::exec();
}
Edit: Adding Code of my Login.h and Login.cpp to provide minimal working example.
My Login.h:
#ifndef RESTCLIENT_LOGIN_H
#define RESTCLIENT_LOGIN_H
#include <QWidget>
#include <QPushButton>
#include <QLineEdit>
#include "QMainWindow"
QT_BEGIN_NAMESPACE
namespace Ui { class Login; }
QT_END_NAMESPACE
class Login : public QMainWindow {
Q_OBJECT
QPushButton * loginButton;
QLineEdit * passwordInput;
QLineEdit * usernameInput;
public slots:
void buttonPressed();
public:
explicit Login(QWidget *parent = nullptr);
~Login() override;
private:
Ui::Login *ui;
};
#endif //RESTCLIENT_LOGIN_H
And Login.cpp:
#include "Login.h"
#include "ui_Login.h"
Login::Login(QWidget *parent) :
QMainWindow(parent), ui(new Ui::Login) {
ui->setupUi(this);
QObject::connect(loginButton, &QPushButton::clicked, this, &Login::buttonPressed);
this ->setCentralWidget(new QWidget(this));
}
Login::~Login() {
delete ui;
}
void Login::buttonPressed() {
//todo process login
}
There is no more errors when running it, as far as I undestand it, there is no problem with finding it.
My Login GUI is very simple, I'm connecting my loginButton to the buttonPressed method in the Login.cpp, but that should be fine.
My Login.h is basically method definiton and definition of the QT elements.
Some help would be very nice, cause I can't find any usefull stuff about this (As you see, I'm new to c++ and QT)
Editi 2:
my ui_login.h:
/********************************************************************************
** Form generated from reading UI file 'Login.ui'
**
** Created by: Qt User Interface Compiler version 6.2.4
**
** WARNING! All changes made in this file will be lost when recompiling UI file!
********************************************************************************/
#ifndef UI_LOGIN_H
#define UI_LOGIN_H
#include <QtCore/QVariant>
#include <QtWidgets/QApplication>
#include <QtWidgets/QLabel>
#include <QtWidgets/QLineEdit>
#include <QtWidgets/QPushButton>
#include <QtWidgets/QWidget>
QT_BEGIN_NAMESPACE
class Ui_Login
{
public:
QLabel *label;
QLabel *label_2;
QLineEdit *usernameInput;
QLineEdit *passwordInput;
QPushButton *loginButton;
void setupUi(QWidget *Login)
{
if (Login->objectName().isEmpty())
Login->setObjectName(QString::fromUtf8("Login"));
Login->resize(1216, 835);
label = new QLabel(Login);
label->setObjectName(QString::fromUtf8("label"));
label->setGeometry(QRect(230, 180, 121, 51));
label->setLineWidth(2);
label_2 = new QLabel(Login);
label_2->setObjectName(QString::fromUtf8("label_2"));
label_2->setGeometry(QRect(220, 340, 111, 41));
usernameInput = new QLineEdit(Login);
usernameInput->setObjectName(QString::fromUtf8("usernameInput"));
usernameInput->setGeometry(QRect(490, 190, 141, 51));
passwordInput = new QLineEdit(Login);
passwordInput->setObjectName(QString::fromUtf8("passwordInput"));
passwordInput->setGeometry(QRect(490, 360, 151, 41));
loginButton = new QPushButton(Login);
loginButton->setObjectName(QString::fromUtf8("loginButton"));
loginButton->setGeometry(QRect(520, 480, 88, 34));
retranslateUi(Login);
QObject::connect(loginButton, &QPushButton::clicked, loginButton, qOverload<>(&QPushButton::click));
QMetaObject::connectSlotsByName(Login);
} // setupUi
void retranslateUi(QWidget *Login)
{
Login->setWindowTitle(QCoreApplication::translate("Login", "Login", nullptr));
label->setText(QCoreApplication::translate("Login", "Username:", nullptr));
label_2->setText(QCoreApplication::translate("Login", "Password:", nullptr));
loginButton->setText(QCoreApplication::translate("Login", "Login", nullptr));
} // retranslateUi
};
namespace Ui {
class Login: public Ui_Login {};
} // namespace Ui
QT_END_NAMESPACE
#endif // UI_LOGIN_H