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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: question re Ada equivalent of C function
Date: 1998/02/22
Message-ID: <dewar.888162643@merv>#1/1
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Date: 1998-02-22T00:00:00+00:00
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<<As both Linux and NT are real operating systems, neither will allow you to
directly
access an IO port from a user program. By messing around with rights and
such
you might be able to pull it off using inline-assembly tricks, but at this
low level
both Linux vs NT and GNAT vs OA are incompatible.

>>

Although this may be a valid description of restrictions in NT and Linux,
it is by no means a necessary restriction. In OS/2, you can use inp and
outp from a protected mode program if you use a .DEF file to declare
the IOSEG segment that the run-time library uses to perform
input/output to the port. The code for the segment must be marked
with the IOPL keyword in the .DEF file. FOr more details, have a look
at the OS/2 documentation, or look in the Microsoft C Run-Time
Library Reference document (an excellent source for all sorts of
information on C-callable routines and their compatibility across
systems).

I am not suggesting that everyone move to OS/2, just pointing out that
the chain of reasoning that X is a "real operating system", therefore
X cannot allow you to directly access an IO port is misleading.