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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: calenday (was Re: IBM Acquires Rational Ada
Date: Fri, 20 Dec 2002 15:35:03 -0600
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Larry Kilgallen wrote in message
<7HQjlgUY7GDY@eisner.encompasserve.org>...
>In article <v04c0ul05vht40@corp.supernews.com>, "Randy Brukardt"
<randy@rrsoftware.com> writes:
>
>> a) is not a problem in practice. We did this in Claw, and all
compilers
>> put the tag at offset 0. (A few can be told to put it elsewhere, but
>> that wasn't generally available a few years ago when we did that.)
The
>> size is a problem in that it is implementation-defined.
>
>Which compilers allowed you (at the time) to specify the tag position ?
>
>What language construct did they use to accept that specification ?

Janus/Ada doesn't allow to specify the location of the tag explicitly,
but it doesn't require a particular position, either. So if you put a
component at location 0, the compiler will put the tag elsewhere (in the
first hole big enough). And if you specify the location of all other
components and the record size, it's pretty clear where the tag is. :-)

Pascal Leroy of Rational has indicated that they had at least one
customer who needed tags other than at location 0, so that their
compiler supports that as well. I don't know if they explicitly allow
specifying it, and I don't know the syntax if they do. I would presume
it is an attribute, following the standard, see 13.5.1(15).

             Randy.