From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Thread: 103376,8ecbc35ea893182f
X-Google-Attributes: gid103376,public,usenet
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news1.google.com!news3.google.com!feeder1-2.proxad.net!proxad.net!feeder1-1.proxad.net!club-internet.fr!feedme-small.clubint.net!nuzba.szn.dk!news.jacob-sparre.dk!pnx.dk!not-for-mail
From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Interfacing to C: big structures
Date: Tue, 26 Feb 2008 15:14:36 -0600
Organization: Jacob's private Usenet server
Message-ID: <fq1vnp$kq1$1@jacob-sparre.dk>
References: 
 <c48dc7da-6f04-4f0f-9a8f-e0acc371ee3c@o10g2000hsf.googlegroups.com>
 <62idb0F23ddfnU1@mid.individual.net>
 <56a177e4-506f-4bc8-a531-7f2dd15d50c8@i7g2000prf.googlegroups.com>
 <m27igr4i0b.fsf@mac.com>
NNTP-Posting-Host: static-69-95-181-76.mad.choiceone.net
X-Trace: jacob-sparre.dk 1204060729 21313 69.95.181.76 (26 Feb 2008 21:18:49
 GMT)
X-Complaints-To: news@jacob-sparre.dk
NNTP-Posting-Date: Tue, 26 Feb 2008 21:18:49 +0000 (UTC)
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 6.00.2800.1914
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1914
Xref: g2news1.google.com comp.lang.ada:20111
Date: 2008-02-26T15:14:36-06:00
List-Id: <comp.lang.ada>

"Simon Wright" <simon.j.wright@mac.com> wrote in message
news:m27igr4i0b.fsf@mac.com...
> Adam Beneschan <adam@irvine.com> writes:
>
> > I thought of something like this, but Maciej said something about
> > wanting to avoid dynamic memory, and it seems that you're defining a
> > type whose size isn't going to be known until runtime, and therefore
> > if you declare an Ada variable of that type, it will have to be
> > allocated dynamically in some way.
>
> That was the cunning trick: the size is known at *elaboration* time!
>
> procedure Main_Program is
>   type T is Ada.Streams.Stream_Element_Array (1 .. Size_Returned_From_C);
>   V : aliased T;

But at least some compilers will allocate V on the heap (under the covers,
of course) because the size of the object is not know at compile-time.
Janus/Ada works this way, for instance. For high-integrity applications,
that's still unacceptable.

But the OP didn't provide enough information to know if this is acceptable
to him or not.

                                          Randy.