From: "J-P. Rosen" <rosen@adalog.fr>
Subject: Re: Question about package Interfaces.
Date: Tue, 14 Sep 2010 19:01:33 +0200
Date: 2010-09-14T19:01:33+02:00 [thread overview]
Message-ID: <i6o9pe$9ug$1@news.eternal-september.org> (raw)
In-Reply-To: <i6o8at$1e1c$1@adenine.netfront.net>
Le 14/09/2010 18:36, Jeffrey Carter a �crit :
> 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.
>
Not exactly.
A compiler is allowed to overwrite unused bytes if it makes code more
efficient
--
---------------------------------------------------------
J-P. Rosen (rosen@adalog.fr)
Visit Adalog's web site at http://www.adalog.fr
prev parent reply other threads:[~2010-09-14 17:01 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
2010-09-14 17:01 ` J-P. Rosen [this message]
replies disabled
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox