From mboxrd@z Thu Jan  1 00:00:00 1970
Received: (from weis@localhost) by pauillac.inria.fr (8.7.6/8.7.3) id WAA19864 for caml-red; Sat, 10 Feb 2001 22:27:36 +0100 (MET)
Received: from nez-perce.inria.fr (nez-perce.inria.fr [192.93.2.78]) by pauillac.inria.fr (8.7.6/8.7.3) with ESMTP id WAA32441 for <caml-list@pauillac.inria.fr>; Fri, 9 Feb 2001 22:36:29 +0100 (MET)
Received: from ftp.filemaker.com (ftp.filemaker.com [192.35.50.27])
	by nez-perce.inria.fr (8.11.1/8.10.0) with ESMTP id f19LaSL02778
	for <caml-list@inria.fr>; Fri, 9 Feb 2001 22:36:28 +0100 (MET)
Received: from imap.filemaker.com (imap.filemaker.com [17.184.4.101])
	by ftp.filemaker.com (8.9.0/8.9.0) with ESMTP id NAA18516
	for <caml-list@inria.fr>; Fri, 9 Feb 2001 13:01:56 -0800 (PST)
Received: from [17.184.16.95] ([17.184.16.95])
	by imap.filemaker.com (8.9.3/8.9.0) with SMTP id NAA02332
	for <caml-list@inria.fr>; Fri, 9 Feb 2001 13:01:53 -0800 (PST)
Message-Id: <200102092101.NAA02332@imap.filemaker.com>
Subject: Strange memory leak
Date: Fri, 9 Feb 2001 13:08:57 -0800
x-sender: hao-yang_wang@mail.filemaker.com
x-mailer: Claris Emailer 2.0v3, January 22, 1998
From: Hao-yang Wang <hao-yang_wang@filemaker.com>
To: <caml-list@inria.fr>
Mime-Version: 1.0
Content-Type: text/plain; charset="US-ASCII"
Sender: weis@pauillac.inria.fr

I wrote this bunch of code:
-----------------------------------
type 'a zlist = Znull | Zcons of 'a * 'a zzlist
and 'a zzlist = 'a zlist Lazy.t

let rec zfilter f zz =
    let z = Lazy.force zz in
    match z with
        Znull ->
            Znull
      | Zcons(head, ztail) ->
            if f head then
                z
            else
                zfilter f ztail

let rec build_list n =
    if n > 0 then
        Zcons(n, lazy (build_list (n - 1)))
    else
        Znull

let rec loopy f zz =
    match zfilter f zz with
        Znull ->
            ()
      | Zcons(head, ztail) ->
            loopy f ztail
-----------------------------------
>>From the byte-code toplevel, the following expression evaluates fine

  loopy (fun x -> true) (lazy (build_list 1000000));;

while the following expression produces "Fatal error: out of memory."

  loopy (fun x -> false) (lazy (build_list 1000000));;

Why? In particular, the function zfilter looks tail-recursive to me.

I am using ocaml-3.00, with the Macintosh version of top-level.

Thanks,
Hao-yang Wang