From: Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>
Subject: Re: Question about package Interfaces.
Date: Tue, 14 Sep 2010 09:36:43 -0700
Date: 2010-09-14T09:36:43-07:00 [thread overview]
Message-ID: <i6o8at$1e1c$1@adenine.netfront.net> (raw)
In-Reply-To: <i6n4vc$a9$1@news.eternal-september.org>
On 09/13/2010 11:33 PM, J-P. Rosen wrote:
>
> Imagine that you declared:
> X : Unsigned_8;
> and you discover that the declaration advances the data counter by 4
> bytes. You can interpret that as X occupying 32 bits, or as X occupying
> only 8 bits with 3 unused padding bytes ahead of it.
>
> There is positively no way to tell the difference.
You could examine the machine code to see if it does 4-byte or 1-byte load and
stores.
This might be important if X were, say, a memory-mapped control register for a
H/W device. But then, I'd expect to see
for X'Size use 8;
for X'Address use ...;
--
Jeff Carter
"To Err is human, to really screw up, you need C++!"
St�phane Richard
63
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next prev parent reply other threads:[~2010-09-14 16:36 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-13 1:10 Question about package Interfaces Peter C. Chapin
2010-09-13 3:54 ` Robert A Duff
2010-09-13 13:47 ` Peter C. Chapin
2010-09-13 14:15 ` Robert A Duff
2010-09-13 18:31 ` Peter C. Chapin
2010-09-13 22:47 ` Robert A Duff
2010-09-14 6:33 ` J-P. Rosen
2010-09-14 16:36 ` Jeffrey Carter [this message]
2010-09-14 17:01 ` J-P. Rosen
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