Date: Tue, 29 Oct 1996 08:25:30 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: Bill Currie <billc AT blackmagic DOT tait DOT co DOT nz>
Cc: DJGPP workers <djgpp-workers AT delorie DOT com>
Subject: Re: function _exit() and about dbgcom.c
In-Reply-To: <3275D36A.15D7@blackmagic.tait.co.nz>
Message-Id: <Pine.SUN.3.91.961029081515.18709D-100000@is>
Mime-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII


On Tue, 29 Oct 1996, Bill Currie wrote:

> err, why not create a REAL PSP? Easy enough (debug.com does it).  Sure it means swapping psp's 
> when going to/from debuggee, but it might cause less hassles in the long run?

It also means messing with undocumented DOS where you don't have to, 
which in turn probably means problems in Windows, which gets more and 
more innovative about this issue with every Windows revision.  (Read the 
"Undocumented DOS, 2nd ed." and the "Unauthorized Windows 95" for the 
juicy details.)  As an excercise for starters, try to reflect on the fact 
that the DOS call to create a PSP was undocumented until DOS 5.0.

Whenever you run a DJGPP program, DOS thinks that the program which runs
is the DPMI host (in v1.x, it was go32.exe who played this role).  So the
PSP actually belongs to the DPMI host.  I guess this means that switching
PSPs between the debugger and the debuggee means that you also need a PSP
for every DJGPP programs, and creating it must be a terrible pain in the
lower back and a lot of code bloat. 

Given how good the DJGPP debug system works all the above notwithstanding,
I would say leave it alone.