From owner-freebsd-threads@FreeBSD.ORG  Thu Dec 29 05:50:08 2005
Return-Path: <owner-freebsd-threads@FreeBSD.ORG>
X-Original-To: freebsd-threads@hub.freebsd.org
Delivered-To: freebsd-threads@hub.freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 9E02016A41F
	for <freebsd-threads@hub.freebsd.org>;
	Thu, 29 Dec 2005 05:50:08 +0000 (GMT)
	(envelope-from gnats@FreeBSD.org)
Received: from freefall.freebsd.org (freefall.freebsd.org [216.136.204.21])
	by mx1.FreeBSD.org (Postfix) with ESMTP id A8FA043D55
	for <freebsd-threads@hub.freebsd.org>;
	Thu, 29 Dec 2005 05:50:07 +0000 (GMT)
	(envelope-from gnats@FreeBSD.org)
Received: from freefall.freebsd.org (gnats@localhost [127.0.0.1])
	by freefall.freebsd.org (8.13.4/8.13.4) with ESMTP id jBT5o7Ul072508
	for <freebsd-threads@freefall.freebsd.org>;
	Thu, 29 Dec 2005 05:50:07 GMT
	(envelope-from gnats@freefall.freebsd.org)
Received: (from gnats@localhost)
	by freefall.freebsd.org (8.13.4/8.13.4/Submit) id jBT5o7Cn072507;
	Thu, 29 Dec 2005 05:50:07 GMT (envelope-from gnats)
Date: Thu, 29 Dec 2005 05:50:07 GMT
Message-Id: <200512290550.jBT5o7Cn072507@freefall.freebsd.org>
To: freebsd-threads@FreeBSD.org
From: Dmitrij Tejblum <tejblum@yandex-team.ru>
Cc: 
Subject: Re: threads/79887: [patch] freopen() isn't thread-safe
X-BeenThere: freebsd-threads@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
Reply-To: Dmitrij Tejblum <tejblum@yandex-team.ru>
List-Id: Threading on FreeBSD <freebsd-threads.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-threads>, 
	<mailto:freebsd-threads-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-threads>
List-Post: <mailto:freebsd-threads@freebsd.org>
List-Help: <mailto:freebsd-threads-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-threads>,
	<mailto:freebsd-threads-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 29 Dec 2005 05:50:08 -0000

The following reply was made to PR threads/79887; it has been noted by GNATS.

From: Dmitrij Tejblum <tejblum@yandex-team.ru>
To: David Xu <davidxu@freebsd.org>
Cc: bug-followup@freebsd.org
Subject: Re: threads/79887: [patch] freopen() isn't thread-safe
Date: Thu, 29 Dec 2005 08:43:15 +0300

 David Xu wrote:
 
 > Dmitrij Tejblum wrote:
 >
 >>
 >> David Xu wrote:
 >>
 >>> Indeed, this a bug, but the patch you provided breaks the samentic the
 >>> FILE structure was designed for, here you conditionally call
 >>> fp->_close(), this is incorrect, because the hook may be an external
 >>> function, it should always be called to notify external code.
 >>
 >>
 >>
 >> I only assume that
 >> 1) _file and _close fields are internal to stdio, i.e. only stdio 
 >> code manipulate with them directly
 >> 2) If _file != -1, then the FILE is associated with the file 
 >> descriptor, fp->_close == __sclose (because the only code that can 
 >> set fp_close to something different is funopen, and it set _file to 
 >> -1) and __sclose just close the _fp->_file
 >> If so, we know that dup2() will close the descriptor too, dup2() is 
 >> required to do it.
 >>
 > I think we allow _close and others to be changed by user code unless
 > someone can clarify that this is not allowed now, otherwise your
 > assumption is false.
 
 Well, this is C, not C++, so there cannot be strict difference between 
 allowed and disallowed. But the _close field is not required by any 
 standarts (funopen() too) and is not documented by manpages (I checked 
 manpages with grep). And there does exist documented interface for 
 setting _close: funopen(). Thus _close is internal.