int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    //the same version of context for all GL widgets
    QSurfaceFormat format;
    format.setDepthBufferSize(24);
    format.setStencilBufferSize(8);
    format.setVersion(4, 5);
    format.setProfile(QSurfaceFormat::CoreProfile);
    QSurfaceFormat::setDefaultFormat(format);

    //restores std::stof divides numbers by '.' instead of local
    std::setlocale(LC_ALL, "C");

    if (argc > 2 && std::string(argv[1]) == "--config")
    {
        Config(std::string(argv[2]));
    }
    else
    {
        Config();
    }

    //creation and displaying main window
    MainWindow w = new MainWindow();
    w.show();      //<------ somwhere below segmentation happens

    return a.exec();
}

Main window looks like this:

MainWindow::MainWindow(QWidget *parent): QMainWindow(parent), ui(new Ui::MainWindow)
{
    inpMan = &ObjManager::getInstance();
    tm = &TimelapseManager::getInstance();

    ui->setupUi(this);

    oglWindow = std::make_unique<OGLWindow>(qobject_cast<OGLWindow*>(ui->oglWindow));

    if (!oglWindow) {
        oglWindow = std::make_unique<OGLWindow>(new OGLWindow(this));
        ui->oglWindow->setParent(nullptr);
        ui->oglWindow->deleteLater();
        ui->centralwidget->layout()->addWidget(oglWindow.get());
    }

    initGUI();
    enableUIElements(false);

    // glutInit(argc, argv);    //<----remnant of glut
}

segmentation happens when w.show() is proceeded and statck trace looks like this:

1  QOpenGLContext::functions() const                                                          0x7ffe7131809a 
2  QOpenGLWidget::qt_static_metacall(QObject *, QMetaObject::Call, int, void * *)             0x7ffeb7f921da 
3  QOpenGLWidget::makeCurrent(QOpenGLWidget::TargetBuffer)                                    0x7ffeb7f93798 
4  QWidget::event(QEvent *)                                                                   0x7ffe72f09d90 
5  QApplicationPrivate::notify_helper(QObject *, QEvent *)                                    0x7ffe72eb5b5c 
6  QCoreApplication::notifyInternal2(QObject *, QEvent *)                                     0x7ffe71aa73aa 
7  QWidgetPrivate::sendPaintEvent(QRegion const&)                                             0x7ffe72f0113e 
8  QOpenGLWidget::resizeEvent(QResizeEvent *)                                                 0x7ffeb7f92fea 
9  QWidget::event(QEvent *)                                                                   0x7ffe72f0a417 
10 QApplicationPrivate::notify_helper(QObject *, QEvent *)                                    0x7ffe72eb5b5c 
11 QCoreApplication::notifyInternal2(QObject *, QEvent *)                                     0x7ffe71aa73aa 
12 QWidgetPrivate::sendPendingMoveAndResizeEvents(bool, bool)                                 0x7ffe72f0105b 
13 QWidgetPrivate::show_helper()                                                              0x7ffe72f06349 
14 QWidgetPrivate::setVisible(bool)                                                           0x7ffe72f094a4 
15 QWidgetPrivate::showChildren(bool)                                                         0x7ffe72f05df1 
16 QWidgetPrivate::show_helper()                                                              0x7ffe72f06366 
17 QWidgetPrivate::setVisible(bool)                                                           0x7ffe72f094a4 
18 QWidgetPrivate::showChildren(bool)                                                         0x7ffe72f05df1 
19 QWidgetPrivate::show_helper()                                                              0x7ffe72f06366 
20 QWidgetPrivate::setVisible(bool)                                                           0x7ffe72f094a4 
21 main                                                                           main.cpp 33 0x7ff641ae586f

It tells me something is with context but what? During debug everything is initialized in my OGLWindow::OGLWindow(QWidget *parent):QOpenGLWidget(parent) window properly

void OGLWindow::initializeGL()
{
    initializeOpenGLFunctions();

    glEnable(GL_PROGRAM_POINT_SIZE);
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_BLEND);

    createShaders();

    fillBufferCross();
    fillBufferScale();
}

What I miss?