Re: Avoiding dangling pointers.

Rafael Anschau wrote:
> If you set p=0, you are not pointing nowhere, and I found that weird.
But
> it actualy makes sense, it´s better to have the program crash
> right away if something tries to write on it, than to have it write fine
> on some dark zone of heapland which you will never be able to reach
again.
> Reduces debugging time.

Actually, you missed a point: if the value of a pointer is zero, this is a
special signal value which means that it doesn't point to an object. Of
course, trying to use the object it points to (which doesn't exist) will
result in a crash, but even more im****tant is the fact that you can
_check_
if the pointer is zero and thus prevent the crash!

int* i = new int(42);
delete i;
/* 'i' now points to nowhere ('dangling pointer'), but there is no way to
detect that it doesn't point to an object. */
i = 0;
// Now you again have a usable state that you can work with


Note that a good way to avoid dangling pointers is to use so-called 'smart
pointers', which make reasonable sure that they are never dangling and
also
achieve defined error signalling behaviour even in the face of typical
programming errors.

Uli

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