Sams Teach Yourself C++ in 24 Hours, Third Edition

Stray or Dangling Pointers

One source of bugs that are nasty and difficult to find is stray pointers. A stray pointer is created when you call delete on a pointer—thereby freeing the memory that it points to—and later try to use that pointer again without reassigning it.

It is as though the Acme Mail Order company moved away, and you still pressed the programmed button on your phone. It is possible that nothing terrible happens—a telephone rings in a deserted warehouse. Another possibility is that the telephone number has been reassigned to a munitions factory, and your call detonates an explosive and blows up your whole city!

In short, be careful not to use a pointer after you have called delete on it. The pointer still points to the old area ...