From owner-freebsd-stable@FreeBSD.ORG  Mon Jun  1 15:34:04 2009
Return-Path: <owner-freebsd-stable@FreeBSD.ORG>
Delivered-To: freebsd-stable@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 453DC1065676
	for <freebsd-stable@freebsd.org>; Mon,  1 Jun 2009 15:34:04 +0000 (UTC)
	(envelope-from dudu@dudu.ro)
Received: from mail-bw0-f213.google.com (mail-bw0-f213.google.com
	[209.85.218.213])
	by mx1.freebsd.org (Postfix) with ESMTP id CF2808FC16
	for <freebsd-stable@freebsd.org>; Mon,  1 Jun 2009 15:34:03 +0000 (UTC)
	(envelope-from dudu@dudu.ro)
Received: by bwz9 with SMTP id 9so7724710bwz.43
	for <freebsd-stable@freebsd.org>; Mon, 01 Jun 2009 08:34:02 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.223.112.204 with SMTP id x12mr3263188fap.70.1243870442714; 
	Mon, 01 Jun 2009 08:34:02 -0700 (PDT)
From: Vlad Galu <dudu@dudu.ro>
Date: Mon, 1 Jun 2009 18:33:42 +0300
Message-ID: <ad79ad6b0906010833y20042080td1ebe0d3bfffbdc5@mail.gmail.com>
To: freebsd-stable@freebsd.org
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Subject: Unnamed POSIX shared semaphores
X-BeenThere: freebsd-stable@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Production branch of FreeBSD source code <freebsd-stable.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-stable>, 
	<mailto:freebsd-stable-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-stable>
List-Post: <mailto:freebsd-stable@freebsd.org>
List-Help: <mailto:freebsd-stable-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-stable>,
	<mailto:freebsd-stable-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 01 Jun 2009 15:34:04 -0000

Hello,

According to sem_init(3), we can't have shared unnamed semaphores.
However, the following code snippet seems to work just  fine:

-- cut here --
        sem_t semaphore;
        if (sem_init(&semaphore, 1, 10) < 0)
                std::cout << "Couldn't init semaphore: " <<
strerror(errno) << std::endl;
        if (sem_wait(&semaphore) < 0)
                std::cout << "Couldn't decrement semaphore: " <<
strerror(errno) << std::endl;
        int val;
        sem_getvalue(&semaphore, &val);
        std::cout << "Value is " << val << std::endl;
-- and here --

Is this a case where sem_init() silently reports success, or should be
the man page get an update?

Thanks,
Vlad