Adding new variable into header file breaks my application

[Raadush]

Wiseguy: it doesn't crash. In my main:

CardManager cardManager;
 
    if(cardManager.isLoaded())
    {
        cardManager.mainWindow.show();
        app.exec();
    }

CardManager cardManager;

    if(cardManager.isLoaded())
    {
        cardManager.mainWindow.show();
        app.exec();
    }

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when I have commented those 4 lines in header file, when debugger hits app.exec(), mainWindow of cardManager is shown. When I uncomment one of those commented lines, when it hits app.exec() nothing happens, no mainWindow is shown the application only get stuck in exec() loop and I must close it usind stop button.

amleto: Yes, what I'm posting is not fault, but as I said there are 4 commented lines in that code and when I uncoment one of them (define one new QMenu or QAction variable) my app stops working. I dont have used them anywhere else in my code except this definition.