From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <jon@ffconsultancy.com>
X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on yquem.inria.fr
X-Spam-Level: 
X-Spam-Status: No, score=0.0 required=5.0 tests=AWL autolearn=disabled 
	version=3.1.3
X-Original-To: caml-list@yquem.inria.fr
Delivered-To: caml-list@yquem.inria.fr
Received: from mail4-relais-sop.national.inria.fr (mail4-relais-sop.national.inria.fr [192.134.164.105])
	by yquem.inria.fr (Postfix) with ESMTP id 12EFDBC6C
	for <caml-list@yquem.inria.fr>; Mon,  4 Feb 2008 11:58:44 +0100 (CET)
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: Ah4FAIZ+pkfUnw7VhWdsb2JhbACCNo1zAQEBCAQGBwgTB5oQ
X-IronPort-AV: E=Sophos;i="4.25,302,1199660400"; 
   d="scan'208";a="22148271"
Received: from ptb-relay02.plus.net ([212.159.14.213])
  by mail4-smtp-sop.national.inria.fr with ESMTP; 04 Feb 2008 11:58:43 +0100
Received: from [80.229.56.224] (helo=beast.local)
	 by ptb-relay02.plus.net with esmtp (Exim) id 1JLz2A-00048W-BC; Mon, 04 Feb 2008 10:58:42 +0000
From: Jon Harrop <jon@ffconsultancy.com>
Organization: Flying Frog Consultancy Ltd.
To: Alain Frisch <alain@frisch.fr>
Subject: Re: [Caml-list] Using OCaml's run-time from LLVM-generated native code
Date: Mon, 4 Feb 2008 10:32:05 +0000
User-Agent: KMail/1.9.7
Cc: caml-list <caml-list@yquem.inria.fr>
References: <200802012124.56835.jon@ffconsultancy.com> <200802032319.15846.jon@ffconsultancy.com> <47A6B8B5.9010907@frisch.fr>
In-Reply-To: <47A6B8B5.9010907@frisch.fr>
MIME-Version: 1.0
Content-Type: text/plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
Message-Id: <200802041032.05929.jon@ffconsultancy.com>
X-Plusnet-Relay: 30e73d340d0dea656e9c309fdd80fe15
X-Spam: no; 0.00; ocaml's:01 run-time:01 frisch:01 ocaml's:01 pointer:01 ocaml:01 runtime:01 ocaml:01 camlparam:01 stdio:01 mlvalues:01 alloc:01 intext:01 extern:01 camlprim:01 

On Monday 04 February 2008 07:03:17 Alain Frisch wrote:
> Jon Harrop wrote:
> > How does OCaml's stack walker work with C code, for example? In
> > particular, how does it know what is a pointer into the heap from a C
> > stack frame? Must it be explicitly disabled?
>
> The OCaml runtime does not scan the stack frames corresponding to C
> functions.

How does it know which stack frames correspond to C functions?

> Jon, it is somewhat weird that you spend so much time writing about
> forking OCaml and do not take a few minutes to read the source code. The
> macros CAMLparam*, CAMLlocal* are not really that mysterious.

Despite the availability of that code it seems that few people can use it 
correctly and I am one of them.

This seems to work even though it calls full_major aggressively:

#include <stdio.h>
#include <string.h>
#include <caml/mlvalues.h>
#include <caml/alloc.h>
#include <caml/memory.h>
#include <caml/fail.h>
#include <caml/callback.h>
#include <caml/custom.h>
#include <caml/intext.h>

extern value caml_gc_full_major(value v);

CAMLprim value fib(value nv) {
  CAMLparam1(nv);
  CAMLlocal5(a, b, c, d, e);
  int64 n = Int64_val(nv);
  if (n < 2) CAMLreturn(nv);
  a = copy_int64(n-1);
  b = copy_int64(n-2);
  c = fib(a);
  d = fib(b);
  e = copy_int64(Int64_val(c) + Int64_val(d));
  caml_gc_full_major(0);
  CAMLreturn(e);
}

int apply(int n) {
  CAMLlocal2(nv, fibn);
  nv = copy_int64(n);
  fibn = fib(nv);
  caml_gc_full_major(0);
  return Int64_val(fib(nv));
}

int main(int argc, char* argv[]) {
  caml_main(argv);
  printf("%d\n", apply(argc == 2 ? atoi(argv[1]) : 10));
  return 0;
}

Is that correct code?

Rather than messing around with these macros in each and every function it is 
probably easier and more efficient to register a single global root at entry, 
pointing to a shadow stack and push and pop elements to and from that 
directly.

-- 
Dr Jon D Harrop, Flying Frog Consultancy Ltd.
http://www.ffconsultancy.com/products/?e