Hi
Im writing a number of apps which need a common class for accessing/storing
various items. The class will be in a shared data segment of a dll (mfc_extn
dll) thus:

////////////////////////////////////////////////////////////////////////////
/
// Here are the global variables...
////////////////////////////////////////////////////////////////////////////
/

#pragma data_seg(".data")
CData* ptrData = NULL;
CData theData;
#pragma data_seg()
#pragma comment(linker, "/SECTION:.data,RWS")

__export etc... CData* getCommonData()
{
 ptrData = &theData;    // just in case the data is relocated...
 return ptrData;

Testing this from first app & data can be read/write ok. from 2nd app, ptr
is returning same value but accessing the class from within the 2nd app does
not giveme the data set in the first...

// ie 1st app...
ptr = getCommonData()
ptr -> setInfo("foo")

// 2nd app...
ptr = getCommonData()
ptr -> getInfo()  <> "foo"

I have done this sort of thing with COM in the past but for this application
there are a number of reasons why we do not wish to go that route..
Any Ideas?
Many Thanks in advance..
Mark

Mark,

You need to initialise theData class - which I suspect isn't
appropriate for you. However, the problem with trying to share a
pointer is that there's no guarantee that the memory will be mapped to
the same address in each process. See Q100634 "HOWTO: Specify Shared
and Nonshared Data in a DLL" for more information.

Dave
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Dave

Thanks for that but... I understand that the memory location wil probably
change hence the call to get the address of the dataclass before I do
anything with it..
i.e I always call..

getCommonData()
{
 ptrData = &theData;
 return ptrData;

I have changed the construction of the class to also initalize it
CData theData("");

when running from 2 apps, the *ptr returned is always the same value but the
data returned from within the class is not..

Ie. 1st app sets data to "111" 2nd app getData = "".

If I then try to set the data from the 2nd App, I get all sorts of memory
access assertions...

Many Thanks
Mark

Mark,

Have you checked Knowledge Base article Q100634? I think that the
information mentioned in its Summary Note still applies in your
situation.

Dave
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Dave

Ok, read, re-read, & re-read again..

So.. even so I am getting the address of the class each time I need it
before ANY action, the fact is that private data in the class may not be in
the shared segment and therefore not avaliable?

So.. in that case .. is there any other method avaliable for me to create a
class in a global memory pool? Or any other suggestions? (I was keeping away
from com as the apps will need to be ported to CE in  the near future & I
was trying to keep overheads to a minimum..) but I may have no option..

Many thanks dave
Regards
Mark

Yes - that's what I believe anyhow.

Adopt a less complicated method - just share a structure with the data
that can easily be put in the shared area?

Dave
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Ill try that - thacks again Dave