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From: Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP>
Newsgroups: comp.lang.ada
Subject: Re: Oberon and Wirthian languages
Date: Wed, 23 Apr 2014 12:17:30 +0000 (UTC)
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Date: 2014-04-23T12:17:30+00:00
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On 2014-04-22, Randy Brukardt <randy@rrsoftware.com> wrote:
> "Simon Clubley" <clubley@remove_me.eisner.decus.org-Earth.UFP> wrote in 
> message news:lj4de1$jql$1@dont-email.me...
>>
>> Thank you. It was not at all 100% clear from the RM if Ada offered the
>> _guarantee_ that if you had, say, 3 components in a record assignment
>> for a atomic bitfield record, that the record assignment would be treated
>> as one atomic operation instead of 3 atomic operations (one for each
>> component).
>
> It's not quite a guarentee, as it's Implementation Advice (C.6(22-23/2). The 
> reason for it being IA is simply that we can't use undefined terms like 
> "load" and "store" in normative wording. In this case, IA is actually 
> stronger because we can say directly what we mean without defining it 
> exactly. In theory, implementations are supposed to document all cases where 
> they do not follow Implementation Advice, so you should be able to determine 
> for a particular implementation as to whether it is followed.
>
> I don't think there could be an absolute guarantee, as the idea of a load or 
> store might not make sense on a data-flow machine (or some other exotic 
> design). I would guess that implementers do this in virtually all cases. As 
> Jeff said, if it is really critical, you have a verify the code.
>

Ok, those are some interesting insights.

Thanks, Randy.

Simon.

-- 
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980s technology to a 21st century world