From:	sandmann AT clio DOT rice DOT edu (Charles Sandmann)
Message-Id:	<9801141421.AA14365@clio.rice.edu>
Subject:	Re: [MCLSSAA2 AT fs2 DOT mt DOT umist DOT ac DOT uk: Hooking interrupt 9 : a DIFF]
To:	eliz AT is DOT elta DOT co DOT il (Eli Zaretskii)
Date:	Wed, 14 Jan 1998 08:21:18 -0600 (CST)
Cc:	dj AT delorie DOT com, Anthony DOT Appleyard AT umist DOT ac DOT uk, djgpp-workers AT delorie DOT com
In-Reply-To:	<Pine.SUN.3.91.980114131138.8730E-100000@is> from "Eli Zaretskii" at Jan 14, 98 01:12:02 pm

> Are you talking about the user-defined callback here, or about the
> DJGPP handler which is on exceptn.S?

The user-defined callback should be very simple.  If it calls 
functions with arguments, uses any registers which aren't saved,
accesses automatic variables with DS or is compiled -fomit-frame-pointer
things may break.  Since this is a hardware interrupt routine,
try some complicated routines under various DPMI providers and see
how it behaves.  At the very least, I think there should be 
a pushal/popal around the user routine, save all seg regs, and
set up ES also.  There is still the SS/DS mismatch, but if you
don't call anything you are probably OK.

All conjecture from inspection...

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