From owner-freebsd-hackers@freebsd.org  Mon Jan  8 17:52:01 2018
Return-Path: <owner-freebsd-hackers@freebsd.org>
Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 by mailman.ysv.freebsd.org (Postfix) with ESMTP id F3104E7AABF
 for <freebsd-hackers@mailman.ysv.freebsd.org>;
 Mon,  8 Jan 2018 17:52:01 +0000 (UTC)
 (envelope-from eric@vangyzen.net)
Received: from smtp.vangyzen.net (hotblack.vangyzen.net [199.48.133.146])
 by mx1.freebsd.org (Postfix) with ESMTP id DB30E692CC;
 Mon,  8 Jan 2018 17:52:01 +0000 (UTC)
 (envelope-from eric@vangyzen.net)
Received: from sweettea.beer.town (unknown [76.164.8.130])
 by smtp.vangyzen.net (Postfix) with ESMTPSA id 80FEA5646F;
 Mon,  8 Jan 2018 11:52:00 -0600 (CST)
Subject: Re: Is it considered to be ok to not check the return code of
 close(2) in base?
To: "Rodney W. Grimes" <freebsd-rwg@pdx.rh.CN85.dnsmgr.net>,
 Eugene Grosbein <eugen@grosbein.net>
Cc: Brooks Davis <brooks@freebsd.org>, Alan Somers <asomers@freebsd.org>,
 Yuri <yuri@rawbw.com>, Ian Lepore <ian@freebsd.org>,
 Freebsd hackers list <freebsd-hackers@freebsd.org>
References: <201801081655.w08GtO3D022568@pdx.rh.CN85.dnsmgr.net>
From: Eric van Gyzen <eric@vangyzen.net>
Message-ID: <df6f98a5-76db-d6d8-6321-d35b59eeec22@vangyzen.net>
Date: Mon, 8 Jan 2018 11:51:56 -0600
User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:52.0) Gecko/20100101
 Thunderbird/52.4.0
MIME-Version: 1.0
In-Reply-To: <201801081655.w08GtO3D022568@pdx.rh.CN85.dnsmgr.net>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.25
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
 <freebsd-hackers.freebsd.org>
List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-hackers>, 
 <mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers/>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-hackers>, 
 <mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 08 Jan 2018 17:52:02 -0000

On 01/08/2018 10:55, Rodney W. Grimes wrote:
>> 08.01.2018 23:13, Eric van Gyzen wrote:
>>
>>> Right, which is the reason such bugs are hard to diagnose.  Optionally
>>> killing the process on close->EBADF would help find buggy code when
>>> another thread did NOT re-open the file descriptor between the two close
>>> calls.
>>
>> Wouldn't "close(f); assert(errno != EBADF);" be better?

Putting the code in one place is far better than putting it in N
places...after /finding/ those N places.  Indeed, the purpose of this
code is to help people find those places, even in their own code,
outside of base.

> Or even
> #ifdef DEBUG_CLOSE
> #define close(f)	close(f); assert(errno != EBADF);
> #endif

errno could have been EBADF before the close().  A successful close()
does not modify errno.  So, this would have be larger, making it even
more unpalatable.

> Then the people that want to go chasing these errors can,
> and the rest of us are untouched.

Every mention in this thread of killing the process has called it
optional.  Tools, not policy.

Eric