Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!sdd.hp.com!hplabs!otter.hpl.hp.com!hpopd!richardh
From: richardh@hpopd.pwd.hp.com (Richard Hancock)
Newsgroups: comp.os.msdos.apps
Subject: Re: Windows and pointers as parameters
Message-ID: <38900002@hpopd.pwd.hp.com>
Date: 26 Mar 91 12:34:31 GMT
References: <1991Mar22.185504.3266@cs.uoregon.edu>
Organization: The Vicuna Backlash
Lines: 22

/ hpopd:comp.os.msdos.apps / akm@geriatrix.cs.uoregon.edu (Anant Kartik Mithal) /  6:55 pm  Mar 22, 1991 /
Hi,

> a question about pointers as function parameters. Given that windows
> can move code/data around in memory (I believe that is correct), is
> it okay (or is it not okay) to pass pointers as the arguments to a
> function? What I want to do is to have a function set the values of a
> couple of variables (boring sort of stuff), but I am not sure that I
> can pass the variables through pointers to the setting function. eg:

You shouldn't ASSUME that your DS will never change (though I suspect
that in never will in protected mode). Therefore you shouldn't keep
hold of a far pointer to a variable in your DS across any call which
might cause your DS to move (eg. a GlobalAlloc() call).

Having said that, I seem to remember that Windows locks your DS when
it calls your WndProc.

Summary : only pass near pointers; if you do eventually need them as far
pointers simply cast them when you need to use them.

Richard.