From owner-freebsd-hackers@freebsd.org  Sun Dec 31 22:11:46 2017
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 68892EA9E9E
 for <freebsd-hackers@mailman.ysv.freebsd.org>;
 Sun, 31 Dec 2017 22:11:46 +0000 (UTC)
 (envelope-from markmi@dsl-only.net)
Received: from asp.reflexion.net (outbound-mail-210-137.reflexion.net
 [208.70.210.137])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (Client did not present a certificate)
 by mx1.freebsd.org (Postfix) with ESMTPS id F2EF965826
 for <freebsd-hackers@freebsd.org>; Sun, 31 Dec 2017 22:11:45 +0000 (UTC)
 (envelope-from markmi@dsl-only.net)
Received: (qmail 22259 invoked from network); 31 Dec 2017 22:11:38 -0000
Received: from unknown (HELO mail-cs-01.app.dca.reflexion.local) (10.81.19.1)
 by 0 (rfx-qmail) with SMTP; 31 Dec 2017 22:11:38 -0000
Received: by mail-cs-01.app.dca.reflexion.local
 (Reflexion email security v8.40.3) with SMTP;
 Sun, 31 Dec 2017 17:11:38 -0500 (EST)
Received: (qmail 2613 invoked from network); 31 Dec 2017 22:11:38 -0000
Received: from unknown (HELO iron2.pdx.net) (69.64.224.71)
 by 0 (rfx-qmail) with (AES256-SHA encrypted) SMTP; 31 Dec 2017 22:11:38 -0000
Received: from [192.168.1.25] (c-76-115-7-162.hsd1.or.comcast.net
 [76.115.7.162])
 by iron2.pdx.net (Postfix) with ESMTPSA id 66346EC8171;
 Sun, 31 Dec 2017 14:11:37 -0800 (PST)
From: Mark Millard <markmi@dsl-only.net>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: quoted-printable
Mime-Version: 1.0 (Mac OS X Mail 10.3 \(3273\))
Subject: Re: Is it considered to be ok to not check the return code of
 close(2) in base?
Message-Id: <79FFA3EB-5994-4B7B-BE35-F1AB9D4AE3CD@dsl-only.net>
Date: Sun, 31 Dec 2017 14:11:36 -0800
To: phk@phk.freebsd.dk,
 FreeBSD Hackers <freebsd-hackers@freebsd.org>
X-Mailer: Apple Mail (2.3273)
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: Sun, 31 Dec 2017 22:11:46 -0000

Poul-Henning Kamp phk at phk.freebsd.dk wrote on
Sat Dec 30 20:35:35 UTC 2017 :

> But if you just close a file, and you're 100% sure that will work,
> you should write it as:
>=20
> 	assert(close(fd) =3D=3D 0);
>=20
> To tell the rest of us about your assumption and your confidence in =
it.

Quoting the FreeBSD assert man page:

QUOTE
     The assert() macro	may be removed at compile time by defining =
NDEBUG as a
     macro (e.g., by using the cc(1) option -DNDEBUG).
ENDQUOTE

This makes required-actions inside asserts dangerous,
at least without guarantees that NDEBUG will be
undefined. Trying to guarantee that NDEBUG will be
undefined would generally be a bad idea.

So,

assert(close(fd) =3D=3D 0);

is a bad coding practice in my view.

=3D=3D=3D
Mark Millard
markmi at dsl-only.net