Date: Tue, 2 Nov 1999 11:12:20 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
X-Sender: eliz AT is
To: Charles Sandmann <sandmann AT clio DOT rice DOT edu>
cc: djgpp AT delorie DOT com
Subject: Re: Problem with DOS and DPMI
In-Reply-To: <381dc296.sandmann@clio.rice.edu>
Message-ID: <Pine.SUN.3.91.991102111201.20126K-100000@is>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Reply-To: djgpp AT delorie DOT com
X-Mailing-List: djgpp AT delorie DOT com
X-Unsubscribes-To: listserv AT delorie DOT com
Precedence: bulk


On Mon, 1 Nov 1999, Charles Sandmann wrote:

> > On Sun, 31 Oct 1999, Damian Yerrick wrote:
> > 
> > > > Page Fault cr2=10000000 at eip=e75; flags=6
> > > > eax=00000030 ebx=00000000 ecx=0000000c edx=00000000
> > > > esi=0001a44a edi=00000000 ebp=00000000 esp=00002672
> > > > cs=18 ds=38 es=af fs=0 gs=0 ss=20 error=0002
> > > > ================================================
> > > 
> > > Page Fault in Sandmann's CWSDPMI not in Micro$oft's DPMW32
> > > 
> > > This means you are accessing an address below 0x00001000.
> > 
> > Not in this case.  This message comes from CWSDPMI, not from the
> > application (the latter never prints cr2 and flags, and the segment
> > registers are printed differently).  Section 12.2 of the FAQ describes
> > the application crash message when dereferencing NULL pointers; you
> > will see that the format is different.
> 
> You are both right.  The message is from CWSDPMI, and it is 
> referencing a null pointer. the 0x10000000 address is the base of the
> DPMI space, so would be where the null pointer lives.

What exactly in the above data tells that it is a NULL pointer?
AFAIK, Page Fault in a DPMI host can happen for a variety of reasons,
the null page is only one of them.  (In contrast, Page Fault in a DPMI
client's code almost never happens _except_ when a null page is
accessed.)