From owner-freebsd-arch@FreeBSD.ORG Thu Dec 1 15:12:18 2011 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 72719106566C; Thu, 1 Dec 2011 15:12:18 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42]) by mx1.freebsd.org (Postfix) with ESMTP id 47C708FC0A; Thu, 1 Dec 2011 15:12:18 +0000 (UTC) Received: from bigwig.baldwin.cx (bigwig.baldwin.cx [96.47.65.170]) by cyrus.watson.org (Postfix) with ESMTPSA id EF54B46B0C; Thu, 1 Dec 2011 10:12:17 -0500 (EST) Received: from jhbbsd.localnet (unknown [209.249.190.124]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id 710C0B914; Thu, 1 Dec 2011 10:12:17 -0500 (EST) From: John Baldwin To: David Schultz Date: Thu, 1 Dec 2011 10:07:23 -0500 User-Agent: KMail/1.13.5 (FreeBSD/8.2-CBSD-20110714-p8; KDE/4.5.5; amd64; ; ) References: <201111301032.04102.jhb@freebsd.org> <20111201014944.GA78010@zim.MIT.EDU> In-Reply-To: <20111201014944.GA78010@zim.MIT.EDU> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201112011007.23430.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (bigwig.baldwin.cx); Thu, 01 Dec 2011 10:12:17 -0500 (EST) Cc: Zack Kirsch , mdf@freebsd.org, freebsd-arch@freebsd.org Subject: Re: Use of bool / stdbool.h in kernel X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 01 Dec 2011 15:12:18 -0000 On Wednesday, November 30, 2011 8:49:44 pm David Schultz wrote: > On Wed, Nov 30, 2011, John Baldwin wrote: > > On Wednesday, November 30, 2011 12:13:53 am Bruce Evans wrote: > > > On Tue, 29 Nov 2011 mdf@freebsd.org wrote: > > > > > > > At $WORK we have a hack in one of the *.mk files to allow including > > > > stdbool.h in the kernel and we use it extensively. This is not > > > > allowed by style(9), as far as I can tell, because the file is in > > > > include/stdbool.h and those files are not allowed to be included in > > > > kernel sources. > > > > > > Including stdbool.h in the kernel is not a style bug, but unsupported. > > > > > > > What I want to check on is, would it be acceptable to move stdbool.h > > > > from include/stdbool.h to sys/sys/stdbool.h (i.e. like errno.h) and > > > > then include it in the kernel as ? That is, is the > > > > > > Would be a larger style bug, especially if it were actually used. > > > Even its spellings of TRUE and FALSE are strange. Even in userland > > > stdbool.h is considered so useful that it is never used in src/bin > > > and is only used a few times on other src/*bin. src/bin never uses > > > TRUE of FALSE either. > > > > I suspect there is some bias here though due to the fact that there wasn't > > a standard bool type when most of this code was written. :) I don't think > > that means we have to forgo use of the new type now that it is in fact > > standardized in C99. I would be happy to have 'bool' available and the > > lowercase 'true' and 'false' are fine with me. > > The lowercase 'true' and 'false' are intended to mimic C++, where > they are keywords. Regardless of how you prefer to capitalize > them, using them instead of 0 and 1 makes the intent much clearer. > This is especially true in the kernel, where non-zero could mean > true, or it could be an error code. > > Unfortunately, the "new type" is mostly useless, aside from > improving readability. Unlike modern languages, C doesn't > consider it a compile-time error to mix up bools and ints. Yes, I consider it a readability aide and think it is fine as such. -- John Baldwin