Re: Sharing a struct/class/pointer in the data_seg() of a dll?

From:

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>

Newsgroups:

microsoft.public.vc.mfc

Date:

Thu, 5 Feb 2009 23:27:03 -0500

Message-ID:

<OCasrMBiJHA.1252@TK2MSFTNGP03.phx.gbl>

"FFMG" <spambucket@myoddweb.com> wrote in message
news:02d43f57-7874-4cf9-8955-cd64b9e8af33@r37g2000prr.googlegroups.com...

Hi,

if I do

#pragma data_seg (".seg")
int some_number = 0;
#pragma data_seg()

Then the data sharing works as expected, (the data is shared between
the processes).

But if I do,

#pragma data_seg (".seg")
myclass* m_pSomething = NULL;
#pragma data_seg()

although the value of the pointer, (the 32bit value), itself is shared
the data is invalid.
I am guessing that it is because the memory past the pointer is not
accessible to the other process.

So, how can I share a class object/pointer in a DLL?
How would I be able to achieve the above?

This is as expected. Different processes are in different address spaces,
so using the same pointer in multiple processes cannot work. Think of it
this way: Each process has an independent virtual-to-physical address
mapping. So the (virtual) pointer becomes meaningless outside of the
process where it is created.

Share data, not pointers.

--
Scott McPhillips [VC++ MVP]