Date: Mon, 27 Jan 1997 08:59:21 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: Matthew Kennedy <q9522772 AT helios DOT usq DOT edu DOT au>
cc: djgpp AT delorie DOT com
Subject: Re: info on ___djgpp_base_address, ___djgpp_dos_sel, ___djgpp_ds_alias , etc
In-Reply-To: <Pine.HPP.3.95.970122015244.7707C-100000@helios.usq.edu.au>
Message-ID: <Pine.SUN.3.91.970127085205.7993C-100000@is>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII


On Wed, 22 Jan 1997, Matthew Kennedy wrote:

> I haven't has much success in finding documentation on these variables -
> used so frequently in the sample ISR programs (like mkkbd3 etc).

__djgpp_base_address is documented with the `__djgpp_nearptr_enable' 
library function on the libc.inf library reference docs file.  I don't 
know what __djgpp_dos_sel is; if you mean _dos_ds, then it is documented 
with the `_go32_info_block' variable on libc.inf.  __djgpp_ds_alias is a 
selector that has the same base address and limit as the one loaded into 
DS register, but it is always valid, while DS is sometimes made 
deliberately invalid by the DJGPP signal support (so acessing a memory 
will cause an exception and call the signal handler), and so if you use 
DS from a hardware interrupt handler, it might crash when you press e.g. 
Ctrl-Break (which causes a SIGINT).

Generally, searching for these in the libc.inf file should find you all 
the references to them.  Fire up info.exe and press `s' to search the 
entire reference.