Qt framework has an signal for all QObjects which is emmited before destruction of that QObject. This event can be used to have some QObject* variable automatically emptied when the object it points to is destroyed.
But to do this, you need to employ relatively lot of code. You would need to register a signal and link it up to the variable. Not very convenient in my opinion.
Can I have it arranged (by Qt) that a pointer to QObject is cleared automatically when QObject is destroyed?
Not with a raw pointer, no, but Qt supplies a templated QPointer class that does exactly what you are describing.