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From: kendalla@iddic.UUCP (Kendall Auel)
Newsgroups: net.arch
Subject: Re: 286 stack overflow
Message-ID: <2172@iddic.UUCP>
Date: Mon, 9-Sep-85 18:08:06 EDT
Article-I.D.: iddic.2172
Posted: Mon Sep  9 18:08:06 1985
Date-Received: Thu, 12-Sep-85 11:18:53 EDT
References: <8780@microsoft.UUCP>
Reply-To: kendalla@iddic.UUCP (Kendall Auel)
Organization: Tektronix, Beaverton OR
Lines: 28
Summary: 


Gordon Letwin writes:

> [about the 80286 memory protection feature]
>
>                  ... but you can't expand the stack segment when it
> overflows.  Bottom line, the good news is that you can tell the stack
> overflowed, the bad news is that you must now abort the program.

To handle the stack overflow condition, you can simply create another stack
segment. Since Intel allows segments to overlap, it would be a good idea
to have the new segment include the first 2 or 3K words of the original
stack. This allows for addressing parameters which may have been passed
on the stack.

When the stack "underflows", the original stack segment can be brought
back in. I suppose you can call this "virtual stack management".

Question: What happens if the memory directly preceding the original
stack is already in use?  (Hint: what happens if you try, for example,
to expand a 32K segment into a 64K segment?)


Kendall Auel
Tektronix, Inc.
Graphics Workstations Division

(usual disclaimer)