From owner-freebsd-current@FreeBSD.ORG  Mon Mar 31 03:35:17 2008
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@hub.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id CBF6A1065673
	for <freebsd-current@hub.freebsd.org>;
	Mon, 31 Mar 2008 03:35:17 +0000 (UTC)
	(envelope-from davidxu@FreeBSD.org)
Received: from freefall.freebsd.org (freefall.freebsd.org
	[IPv6:2001:4f8:fff6::28])
	by mx1.freebsd.org (Postfix) with ESMTP id B424E8FC1A
	for <freebsd-current@hub.freebsd.org>;
	Mon, 31 Mar 2008 03:35:17 +0000 (UTC)
	(envelope-from davidxu@FreeBSD.org)
Received: from apple.my.domain (root@localhost [127.0.0.1])
	by freefall.freebsd.org (8.14.2/8.14.2) with ESMTP id m2V3ZCkl054222
	for <freebsd-current@freebsd.org>; Mon, 31 Mar 2008 03:35:15 GMT
	(envelope-from davidxu@freebsd.org)
Message-ID: <47F05C44.9020603@freebsd.org>
Date: Mon, 31 Mar 2008 11:36:36 +0800
From: David Xu <davidxu@FreeBSD.org>
User-Agent: Thunderbird 2.0.0.9 (X11/20071211)
MIME-Version: 1.0
To: FreeBSD Current <freebsd-current@FreeBSD.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Cc: 
Subject: localtime() vs localtime_r()
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>, 
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 31 Mar 2008 03:35:18 -0000

According POSIX specification, it seems localtime_r() is not only
a reentrant version of localtime(), but also a performance-wise version.

http://www.opengroup.org/onlinepubs/000095399/functions/localtime.html


[TSF] [Option Start] The localtime_r() function shall convert the time 
in seconds since the Epoch pointed to by timer into a broken-down time 
stored in the structure to which result points. The localtime_r() 
function shall also return a pointer to that same structure.

Unlike localtime(), the reentrant version is not required to set tzname.

[TSF] [Option Start] If the reentrant version does not set tzname, it 
shall not set daylight and shall not set timezone. [Option End]


Our implementation does set tzname, tomezone and daylight, it is a bit
slower than glibc because ours has to call getenv() everytime.

Regards,
David Xu