Re: [Dev-C++] address pointers

[Michael C U. <mu...@cb...>]

On Sat, 31 Jan 2004, Brian Gordon wrote:

> I'm new to C++ and in my C++ book, I am learning about pointers. I have
> a question: can you store an address to some kind of "omnitype" pointer?
> I am thinking about doing something like this:

Although in my last message I showed you how to do what you are asking, I
would also stress that directly manipulating pointer addresses is usually
quite risky unless you are doing some kind of very low level programming
(like programming a microcontroller). Pointer address manipulation is only
guranteed to behave well if you are dealing with an array, where you know
the the elements of the array are stored contigiously in memory. The
following code sample is a disaster waiting to happen:

int x, y;
int *p = x;
p += 1;

In this case, I have increased the address of *p by one integer offset. In
other words, I have increased the address that *p points to by 32 bits. So
*p no longer points at x. But does it point at y? Probably not, because
there is no gurantee that x and y are stroed contigiously in memory, even
though they were declared one right after the other. So in the above
sample, we cannot predict what the results will be since *p now points to
an address with unpredictable contents. (More then likely, *p now points
to garbage).

Hope that clears things up, and hope I wasn't just telling you stuff you
already know. But you said you were new to C++, and it looked like what
you were doing was probably unsafe.

Mike