From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gabriel.scherer@gmail.com>
Received: from mail2-relais-roc.national.inria.fr (mail2-relais-roc.national.inria.fr [192.134.164.83])
	by yquem.inria.fr (Postfix) with ESMTP id 0A1B4BC57
	for <caml-list@yquem.inria.fr>; Tue,  8 Jun 2010 13:41:01 +0200 (CEST)
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: AiECAGfJDUzRVaE0mGdsb2JhbACeOQgVAQEBAQEICQwHESKrfYIChVsuiE8BAQMFglOCPgSODg
X-IronPort-AV: E=Sophos;i="4.53,384,1272837600"; 
   d="scan'208";a="52666543"
Received: from mail-fx0-f52.google.com ([209.85.161.52])
  by mail2-smtp-roc.national.inria.fr with ESMTP; 08 Jun 2010 13:41:00 +0200
Received: by fxm19 with SMTP id 19so2471107fxm.39
        for <caml-list@yquem.inria.fr>; Tue, 08 Jun 2010 04:41:00 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=gmail.com; s=gamma;
        h=domainkey-signature:received:mime-version:sender:received
         :in-reply-to:references:from:date:x-google-sender-auth:message-id
         :subject:to:cc:content-type;
        bh=mHZDcfQH3WFISREpRHnCW7oWGnVJjmJRvIhXVREGUwk=;
        b=v0+GERreNtH1us1WV8jpJYXwoz2xFS43sVz1wNDDGVxl1O04dtgp4NucW9GRGAX9gw
         3HYiDMd95+JXqktGRfHaMYbYQkX6nFNkU1IAw89Nd3VXbAfpJ7b5/1dCbhtzDJ9nULc3
         zMEV4k9YxHqTKl5boVXbeL7BTFU7BC2srUeu4=
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=mime-version:sender:in-reply-to:references:from:date
         :x-google-sender-auth:message-id:subject:to:cc:content-type;
        b=W5Ay7iV2KW8YXql241vwB9rF71YML2H5LtDU6i93Ur0yQwH4QEqkbn9xBIaOI/3/Hu
         xhrhAlLMG51v4SSI1lqNtAJDHkbkXhVpjZsk+KarfuT8WicyTzutso8UQoTGtbMnckBC
         udrWdwjDA9zguDs+sB/RHfcktcMmkDLzoO7jA=
Received: by 10.204.79.204 with SMTP id q12mr7727550bkk.118.1275997260236; 
	Tue, 08 Jun 2010 04:41:00 -0700 (PDT)
MIME-Version: 1.0
Sender: gabriel.scherer@gmail.com
Received: by 10.204.112.14 with HTTP; Tue, 8 Jun 2010 04:40:40 -0700 (PDT)
In-Reply-To: <AANLkTikI4-YKT7A3AaNoippzvyAZBRU-HlhaGAh6QwrC@mail.gmail.com>
References: <4C0D3557.1020200@gmail.com> <010d01cb0672$09f3eb90$1ddbc2b0$@romulus.metastack.com> 
	<4C0D4C88.4070102@gmail.com> <AANLkTinsp9JgePfV6aZVyypOdjNHmNzz3E_i-U3Zvo9S@mail.gmail.com> 
	<AANLkTikI4-YKT7A3AaNoippzvyAZBRU-HlhaGAh6QwrC@mail.gmail.com>
From: bluestorm <bluestorm.dylc@gmail.com>
Date: Tue, 8 Jun 2010 13:40:40 +0200
X-Google-Sender-Auth: d50uMxDWj_lvmUYVlMtr_qtyTZw
Message-ID: <AANLkTimcF7VHWskWk3ZINn_ySH4oxIHFvFP1mXmqtw1x@mail.gmail.com>
Subject: Re: [Caml-list] Converting variants with only constant constructors 
	to integers
To: Kaustuv Chaudhuri <kaustuv.chaudhuri@inria.fr>
Cc: caml-list caml-list <caml-list@yquem.inria.fr>
Content-Type: multipart/alternative; boundary=0016e6d7e90d6e51820488834371
X-Spam: no; 0.00; variants:01 constructors:01 integers:01 segfault:01 segfaults:01 ocaml:01 runtime:01 val:01 segfault:01 segfaults:01 ocaml:01 runtime:01 val:01 caml-list:01 int:01 

--0016e6d7e90d6e51820488834371
Content-Type: text/plain; charset=ISO-8859-1

You're right : that's true in the "int" case and I hadn't considered it.

But if you use the same trick for ('a -> float) or other types you can get a
segfault :

# external floatify : 'a -> float = "%identity";;
external floatify : 'a -> float = "%identity"
# floatify 0;;
Segmentation fault

Also there are other problems with "intify" that may be worse than segfaults
: your application running with nonsense data and failing at an arbitrary
later point. Though ocaml doesn't fail (in the current implementation, it
would be unwise to assume that the GC/runtime will never check this), you
get strange behavior with those integers-wich-are-not-integers :

# let x = intify (1,2);;
val x : int = 70246988845964
# x * 1 - x;;
- : int = 1

--0016e6d7e90d6e51820488834371
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

You&#39;re right : that&#39;s true in the &quot;int&quot; case and I hadn&#=
39;t considered it.<div><br><div>But if you use the same trick for (&#39;a =
-&gt; float) or other types you can get a segfault :</div></div><div><br>

</div><div><div># external floatify : &#39;a -&gt; float =3D &quot;%identit=
y&quot;;;</div><div>external floatify : &#39;a -&gt; float =3D &quot;%ident=
ity&quot;</div><div># floatify 0;;</div><div>Segmentation fault</div></div>

<div><br></div><div>Also there are other problems with &quot;intify&quot; t=
hat may be worse than segfaults : your application running with nonsense da=
ta and failing at an arbitrary later point. Though ocaml doesn&#39;t fail (=
in the current implementation, it would be unwise to assume that the GC/run=
time will never check this), you get strange behavior with those integers-w=
ich-are-not-integers :</div>

<div><br></div><div><div># let x =3D intify (1,2);;</div><div>val x : int =
=3D 70246988845964</div></div><div><div># x * 1 - x;;</div><div>- : int =3D=
 1</div></div>

--0016e6d7e90d6e51820488834371--