passing by reference... my darkest enemy
actual reason below:
In your case (without reference) the compiler generates a temporary object (int) for the first argument of your MyApplication constructor. You pass this temporary int to QApplication’s constructor (with int reference), which saves the address of this reference. Once your MyApplication constructor is done the temporary int is destroyed but QApplication still has its address.
[Desktop Entry]
Type=Application
Version=1.0
Encoding=UTF-8
Name=Hedgewars
GenericName=Fighting Hedgehogs
GenericName[de]=Kämpfende Igel
GenericName[es]=Batallas entre erizos
GenericName[fr]=Bataille de hérissons
GenericName[ko]=고슴도치 싸우기
GenericName[ja]=ファイチングハリネズミ
GenericName[it]=Ricci combattenti
GenericName[pl]=Walczące jeże
GenericName[pt]=Batalhas entre ouriços
GenericName[ru]=Битвы ежей
GenericName[sk]=Bojujúci ježkovia
GenericName[sv]=Stridande igelkottar
Icon=hedgewars.png
Exec=hedgewars
Terminal=false
StartupNotify=false
Categories=Application;Game;StrategyGame;