Date: Wed, 18 Feb 1998 19:01:12 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: Martin Stromberg <Martin DOT Stromberg AT lu DOT erisoft DOT se>
cc: djgpp AT delorie DOT com
Subject: Re: gdb crashing: found a bug in dbgcom.c
In-Reply-To: <6cedqo$fjk$1@antares.lu.erisoft.se>
Message-ID: <Pine.SUN.3.91.980218185814.9672D-100000@is>
MIME-Version: 1.0
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On 18 Feb 1998, Martin Stromberg wrote:

> of the a >= 4096 part. What is that for? Are we never allowed to look at 
> memory addresses < 4096? Why?

The first 4K bytes are the null page.  CWSDPMI (and any other DPMI host 
which supports null-pointer detection) disallows dereferencing a null 
pointer.  Since protection is enforced on the page level, the entire page 
cannot be accessed.  The DPMI hosts which support this feature make it so 
no valid linear address falls into that page.