From: mheaney@on2.com (Matthew Heaney)
Subject: Re: Importing C structs?
Date: 31 Jul 2003 09:59:33 -0700
Date: 2003-07-31T16:59:34+00:00 [thread overview]
Message-ID: <1ec946d1.0307310859.67460c46@posting.google.com> (raw)
In-Reply-To: Xns93C98A38494B8cblamstudentutwenten@194.109.133.20
Ching Bon Lam <c.lam_REMOVE_THIS@student.utwente.nl> wrote in message news:<Xns93C98A38494B8cblamstudentutwenten@194.109.133.20>...
> "Matthew Heaney" <matthewjheaney@earthlink.net> wrote in
> news:1V1Wa.299$jp.55@newsread4.news.pas.earthlink.net:
>
> > This is probably overkill. For an opaque type all you need to do is:
> >
> > type DB_Type is limited null record;
> > type DB_Access is access all DB_Type;
> > for DB_Access'Storage_Size use 0;
> > pragma Convention (C, DB_Access);
>
> overkill? i don't think so.. opaque_structure_def is defined in
> Interfaces.C.Extensions (i-cexten.ads in gnat) as:
>
> subtype opaque_structure_def is System.Address;
>
> just a memory address. That's the same as DB *. Since the api (well, most
> api written in C) only use DB * and not DB, you don't need another access
> type. that's why
A memory address is not the same thing as DB*. A "memory address" has
type void*. A void* can point to anything. A DB* can not.
You are free of course to use System.Address everywhere in Ada, just
as you are free to use void* everywhere in C, but you lose strong
typing that way. There is a reason why the C API used type DB* and
not type void*.
So I stand by my assertion that type opaque_structure_def is not the
correct choice for a binding to dbopen().
next prev parent reply other threads:[~2003-07-31 16:59 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-30 20:03 Importing C structs? Freejack
2003-07-30 20:52 ` chris
2003-07-30 21:26 ` Freejack
2003-07-30 23:50 ` tmoran
2003-07-31 10:53 ` chris
2003-08-04 14:33 ` Andreas Almroth
2003-08-04 15:16 ` Samuel Tardieu
2003-08-04 20:07 ` Randy Brukardt
2003-07-31 17:14 ` Warren W. Gay VE3WWG
2003-08-12 0:02 ` chris
2003-07-31 18:17 ` Xenos
2003-07-31 19:16 ` Simon Wright
2003-07-31 20:17 ` Samuel Tardieu
2003-07-31 20:40 ` Xenos
2003-07-30 23:14 ` Ching Bon Lam
2003-07-31 0:07 ` tmoran
2003-07-31 5:35 ` Matthew Heaney
2003-07-31 7:46 ` Freejack
2003-07-31 9:27 ` Martin Dowie
2003-07-31 21:41 ` Freejack
2003-08-01 7:39 ` Martin Dowie
2003-07-31 17:34 ` Matthew Heaney
2003-07-31 11:29 ` Ching Bon Lam
2003-07-31 16:59 ` Matthew Heaney [this message]
2003-07-31 17:32 ` Warren W. Gay VE3WWG
2003-07-31 17:13 ` Matthew Heaney
2003-07-31 17:40 ` Randy Brukardt
2003-07-31 5:21 ` Matthew Heaney
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