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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: How do I write directly to a memory address?
Date: Mon, 14 Feb 2011 18:25:25 -0600
Organization: Jacob Sparre Andersen Research & Innovation
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Date: 2011-02-14T18:25:25-06:00
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"Hyman Rosen" <hyrosen@mail.com> wrote in message 
news:4d5872d3$0$1707$882e7ee2@usenet-news.net...
> On 2/11/2011 11:47 PM, Edward Fish wrote:
>> But if you're using GNAT you may have noticed that it doesn't allow
>> a straight "For Data'Address Use 16#000B_8000#;" because GNAT
>> uses a private type and not a derivative of Universal_Integer.
>>
>> They recommend an implementation-dependent "to_Address" function,
>> but that would make things non-portable.
>
> Portable to what? Other systems that also happen to have a two-segment
> address with a video frame buffer at 16#000B_8000#? Aren't you being a
> little pedantic here?

There definitely are different degrees of portabaility. He's probably 
thinking of "portable for the same target", that is, portable to another Ada 
implementation on the same target.

That's not that uncommon of a goal. Claw, for example is intended to be a 
portable interface to Windows, "portable" in the sense that it will work on 
all Ada 95 compilers that target Windows. This is something that has to be 
baked in from the beginning, in that if you get in bad habits of depending 
on implementation-specific behavior, it can be very painful to work out from 
under them.

Portability to any Ada compiler for any target is even better, but it 
doesn't make sense for a lot of applications. (What good does an interface 
to Windows do on Linux?)

                              Randy.