From mboxrd@z Thu Jan  1 00:00:00 1970
Received: (from majordomo@localhost) by pauillac.inria.fr (8.7.6/8.7.3) id AAA12271; Tue, 10 Jul 2001 00:09:11 +0200 (MET DST)
X-Authentication-Warning: pauillac.inria.fr: majordomo set sender to owner-caml-list@pauillac.inria.fr using -f
Received: from concorde.inria.fr (concorde.inria.fr [192.93.2.39]) by pauillac.inria.fr (8.7.6/8.7.3) with ESMTP id AAA12267 for <caml-list@pauillac.inria.fr>; Tue, 10 Jul 2001 00:09:10 +0200 (MET DST)
Received: from str12.sobor.org (adsl-63-198-183-99.dsl.snfc21.pacbell.net [63.198.183.99])
	by concorde.inria.fr (8.11.1/8.10.0) with ESMTP id f69M99b12556
	for <caml-list@inria.fr>; Tue, 10 Jul 2001 00:09:09 +0200 (MET DST)
Received: from quasar.ipa.nw.ru (anza.sobor.org [192.168.123.51])
	by str12.sobor.org (Postfix) with ESMTP id 522AEAC065
	for <caml-list@inria.fr>; Mon,  9 Jul 2001 14:56:56 -0700 (PDT)
Message-ID: <3B4A2B48.8B013EA7@quasar.ipa.nw.ru>
Date: Mon, 09 Jul 2001 15:08:08 -0700
From: "Alexander V. Voinov" <avv@quasar.ipa.nw.ru>
Organization: Fear of the Lord is the beginning of wisdom
X-Mailer: Mozilla 4.75 [en] (Windows NT 5.0; U)
X-Accept-Language: en
MIME-Version: 1.0
To: caml <caml-list@inria.fr>
Subject: Re: [Caml-list] GC and interoperability with C
Content-Type: text/plain; charset=koi8-r
Content-Transfer-Encoding: 7bit
Sender: owner-caml-list@pauillac.inria.fr
Precedence: bulk

Hi Jacques,

Jacques Garrigue wrote:
> 
> > From what I see in the documentation, I see no way to 'lock' an OCaml
> > value on the heap so that it can be safely accessed from C code, and
> > then 'unlock' it, say, in the finalization function of some
> > Custom_block. In contrast to Python, e.g., where you just increment and
> > decrement the reference count.
> 
> Yes, Python uses (used?) reference counting. More clever (and faster)
> GC's, like that of caml, have to move things around.
> 
> > If this is right, the interaction of OCaml to C becomes one-way, you
> > cannot safely access OCaml world from arbitrary C code.
> 
> Yes, you can. You just have to register a pointer with the GC, and
> everytime the target is moved around, the pointer will be updated.
> See
>     void register_global_root (value *);
>     void remove_global_root (value *);

Thank you. But how can get a pointer to a value, which came as a
parameter, say:

value my_func(value a, value b)
{
   ...
   make a sophisticated C structure, referring to these values...
   ...
   return result;
}

because &a and &b point to the stack which will vanish upon exit. Or do
the CAMLparam wrappers do what is needed in this case?

Alexander
-------------------
Bug reports: http://caml.inria.fr/bin/caml-bugs  FAQ: http://caml.inria.fr/FAQ/
To unsubscribe, mail caml-list-request@inria.fr  Archives: http://caml.inria.fr