From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <rich@annexia.org>
X-Original-To: caml-list@sympa.inria.fr
Delivered-To: caml-list@sympa.inria.fr
Received: from mail2-relais-roc.national.inria.fr (mail2-relais-roc.national.inria.fr [192.134.164.83])
	by sympa.inria.fr (Postfix) with ESMTPS id 91CAF8009A
	for <caml-list@sympa.inria.fr>; Sat,  3 Dec 2016 14:20:30 +0100 (CET)
Authentication-Results: mail2-smtp-roc.national.inria.fr; spf=None smtp.pra=rich@annexia.org; spf=Pass smtp.mailfrom=rich@annexia.org; spf=Pass smtp.helo=postmaster@annexia.org
Received-SPF: None (mail2-smtp-roc.national.inria.fr: no sender
  authenticity information available from domain of
  rich@annexia.org) identity=pra; client-ip=80.68.91.176;
  receiver=mail2-smtp-roc.national.inria.fr;
  envelope-from="rich@annexia.org";
  x-sender="rich@annexia.org"; x-conformance=sidf_compatible
Received-SPF: Pass (mail2-smtp-roc.national.inria.fr: domain of
  rich@annexia.org designates 80.68.91.176 as permitted sender)
  identity=mailfrom; client-ip=80.68.91.176;
  receiver=mail2-smtp-roc.national.inria.fr;
  envelope-from="rich@annexia.org";
  x-sender="rich@annexia.org"; x-conformance=sidf_compatible;
  x-record-type="v=spf1"
Received-SPF: Pass (mail2-smtp-roc.national.inria.fr: domain of
  postmaster@annexia.org designates 80.68.91.176 as permitted
  sender) identity=helo; client-ip=80.68.91.176;
  receiver=mail2-smtp-roc.national.inria.fr;
  envelope-from="rich@annexia.org";
  x-sender="postmaster@annexia.org";
  x-conformance=sidf_compatible; x-record-type="v=spf1"
IronPort-PHdr: =?us-ascii?q?9a23=3AZLaZzRUiLKzne8kv1wSpZs56bxjV8LGtZVwlr6E/?=
 =?us-ascii?q?grcLSJyIuqrYZhWOt8tkgFKBZ4jH8fUM07OQ6PG7HzBdqsza+DBaKdoXCE9D0Z?=
 =?us-ascii?q?1X1yUbQ+e7SmTDZMbwaCI7GMkQHHRExFqcdXZvJcDlelfJqWez5zNBUj/2NA5y?=
 =?us-ascii?q?O/inUtWK15f//6mI9pbSewRFgiamKfM3dU3u7FaZis5DgI5nI6Asxx+BpnpUaf?=
 =?us-ascii?q?5R2WMgcVOXngru/MCs/LZs9i1Rv7Qq8MsWAovgeKFtB4ZZBzQvKWx924vO81Hh?=
 =?us-ascii?q?Sg2C/TFUBn8XmRpgCg7D4QH7V9H2qCSs5bk14zWTIcCjFeN8Yj+l9ao+DUaw0C?=
 =?us-ascii?q?o=3D?=
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: =?us-ascii?q?A0BuAQC4xUJY/7BbRFBdGgEBAQECAQEBA?=
 =?us-ascii?q?QgBAQEBFgEBAQMBAQEJAQEBgw0BAQEBAR9agQaNR5ViAQEDAQaBHZAyhEuCCCu?=
 =?us-ascii?q?FdwKCHT8UAQEBAQEBAQEBAQFhKIIzBAEVAQSCFwEFOj8QCxgJExIPBSghLohYC?=
 =?us-ascii?q?q9xiz8BAQEBBgEBAQEBHQWFdECEZYd5gjAFmmYBhkqKP5BKSY05hA0fN4EZI4U?=
 =?us-ascii?q?yPjSIMYFPAQEB?=
X-IPAS-Result: =?us-ascii?q?A0BuAQC4xUJY/7BbRFBdGgEBAQECAQEBAQgBAQEBFgEBAQM?=
 =?us-ascii?q?BAQEJAQEBgw0BAQEBAR9agQaNR5ViAQEDAQaBHZAyhEuCCCuFdwKCHT8UAQEBA?=
 =?us-ascii?q?QEBAQEBAQFhKIIzBAEVAQSCFwEFOj8QCxgJExIPBSghLohYCq9xiz8BAQEBBgE?=
 =?us-ascii?q?BAQEBHQWFdECEZYd5gjAFmmYBhkqKP5BKSY05hA0fN4EZI4UyPjSIMYFPAQEB?=
X-IronPort-AV: E=Sophos;i="5.33,735,1477954800"; 
   d="scan'208";a="247928817"
Received: from annexia.org ([80.68.91.176])
  by mail2-smtp-roc.national.inria.fr with ESMTP/TLS/AES128-GCM-SHA256; 03 Dec 2016 14:20:29 +0100
Received: from rich by annexia.org with local (Exim 4.84_2)
	(envelope-from <rich@annexia.org>)
	id 1cDAEu-0007Kq-O0; Sat, 03 Dec 2016 13:20:28 +0000
Date: Sat, 3 Dec 2016 13:20:28 +0000
From: "Richard W.M. Jones" <rich@annexia.org>
To: immanuel litzroth <ilitzroth@gmail.com>
Cc: OCaML List Mailing <caml-list@inria.fr>
Message-ID: <20161203132028.GA28111@annexia.org>
References: <CAJjmLU4n0NVWzzCQ6-P+R1Neg0Er7gUQFJYNeHfLja7VbzEhAA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAJjmLU4n0NVWzzCQ6-P+R1Neg0Er7gUQFJYNeHfLja7VbzEhAA@mail.gmail.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
Subject: Re: [Caml-list] Raising invalid_argument with a constructed string.

On Mon, Nov 28, 2016 at 03:39:05PM +0100, immanuel litzroth wrote:
> caml_invalid_argument(str) is no return and does not free it's
> argument.
> So calling it with a string constructed dynamically will mean it'll never
> get freed.
> I could construct an ocaml string and pass that to caml_raise_with_arg,
> but I don't seem to be able to get to the caml_exn_Invalid_argument from
> c. Am I missing something?

We have the same problem in libguestfs in a few places.  The solution
is to use an allocation on the C stack, either a fixed size buffer or
[although we don't currently use this] a variable sized one using
alloca.  The string is freed when the stack is unwound.  Examples:

https://github.com/libguestfs/libguestfs/blob/master/builder/yajl-c.c#L108-L114
https://github.com/libguestfs/libguestfs/blob/master/v2v/domainxml-c.c#L120

Be nice to have a "freeing" version of caml_raise* I suppose.

Rich.