Application crash

Recently I had very interesting problem. There was an object which caused an application crash when it was deleted. During debugging the content of the object's destructor worked properly, but after a closing bracket application just crashed. After time consuming investigation I found out that the object was defined as global, on the stack. Then a pointer to it was passed to some method which at some point deleted this object using that pointer. Of course when the program exited it tried to destroy already destroyed object.

QObject::deleteLater() - the best way to hide bugs

The method deleteLater() is very often used to avoid application crashes. In fact in most cases it just hides the real problem! Qt provides several methods to avoid dangling pointers and control objects lifetime. For example QObject::setParent can be used or "destroyed" signal. Developers should use them and really dig to the problem, understand what is going on in their product.

Additionally it is important to remember that deleteLater() works only if a main loop (qapp.exec()) of an application is already running or is going to be started after the call. Otherwise the object won't be deleted. In some cases even if there is no memory leaks when a program is running objects might not be cleaned before the program exists. In general it is not a problem since the memory will be freed by the system. Unfortunately it is not possible for valgrind to check if this is the case what basically means that it will report many memory leaks. It is then time consuming to investigate which leaks are real.

http://doc.trolltech.com/4.6/qobject.html#details
http://doc.trolltech.com/4.6/objecttrees.html
http://doc.trolltech.com/4.6/qobject.html#dtor.QObject
http://doc.trolltech.com/4.6/qobject.html#deleteLater

Git

Extremely good presentation about Git:

http://excess.org/article/2008/07/ogre-git-tutorial/