From owner-freebsd-hackers@FreeBSD.ORG  Sun Mar 21 00:46:09 2004
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 29CBF16A4CE
	for <hackers@freebsd.org>; Sun, 21 Mar 2004 00:46:09 -0800 (PST)
Received: from mail003.syd.optusnet.com.au (mail003.syd.optusnet.com.au
	[211.29.132.144])
	by mx1.FreeBSD.org (Postfix) with ESMTP id CD24443D2D
	for <hackers@freebsd.org>; Sun, 21 Mar 2004 00:46:07 -0800 (PST)
	(envelope-from peterjeremy@optushome.com.au)
Received: from server.vk2pj.dyndns.org
	(c211-30-75-229.belrs2.nsw.optusnet.com.au [211.30.75.229])
	i2L8jn416341;	Sun, 21 Mar 2004 19:45:50 +1100
Received: from server.vk2pj.dyndns.org (localhost.vk2pj.dyndns.org
	[127.0.0.1])i2L8jiNa048118;	Sun, 21 Mar 2004 19:45:44 +1100 (EST)
	(envelope-from peter@server.vk2pj.dyndns.org)
Received: (from peter@localhost)
	by server.vk2pj.dyndns.org (8.12.10/8.12.10/Submit) id i2L8jhUc048117;
	Sun, 21 Mar 2004 19:45:43 +1100 (EST)
	(envelope-from peter)
Date: Sun, 21 Mar 2004 19:45:43 +1100
From: Peter Jeremy <peterjeremy@optushome.com.au>
To: Matt Emmerton <matt@gsicomp.on.ca>
Message-ID: <20040321084543.GA48068@server.vk2pj.dyndns.org>
References: <p0602044cbc827481888c@[128.113.24.47]>
	<002f01c40f14$f4406540$1200a8c0@gsicomp.on.ca>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <002f01c40f14$f4406540$1200a8c0@gsicomp.on.ca>
User-Agent: Mutt/1.4.2.1i
cc: hackers@freebsd.org
cc: Garance A Drosihn <drosih@rpi.edu>
Subject: Re: Adventures with gcc: code vs object-code size
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/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: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 21 Mar 2004 08:46:09 -0000

On Sun, Mar 21, 2004 at 02:20:13AM -0500, Matt Emmerton wrote:
>
>----- Original Message ----- 
>From: "Garance A Drosihn" <drosih@rpi.edu>
>To: <hackers@freebsd.org>
>Sent: Saturday, March 20, 2004 5:45 PM
>Subject: Adventures with gcc: code vs object-code size
>> if (strcmp(elemcopy, ":") == 0)
...
>I don't know why the code bloats so much on i386, but I do question the use
>of strcmp() for a single-character compare.
>Something like the following would probably be better (and would avoid your
>problem):
>
>if (elemcopy[0] == ':')
>  inf->count = 0;
>else
>  inf->addelem(inf, elemcopy);

That code isn't equivalent in general.  Your code just checks that the
first character is ':'.  It doesn't verify that the string is exactly
one character long.  It's possible that in this particular context,
elemcopy may be constrained such that it must be ":" if the first
character is ':' but this isn't clear from Garances posting.  The
equivalent code would be:

if (elemcopy[0] == ':' && elemcopy[1] == '\0')
  inf->count = 0;
else
  inf->addelem(inf, elemcopy);

But (IMHO) this is a lot less clear than the former code (thought I admit
I'm guilty of doing this quite a lot in my code).  Note that a modern C
compiler is free to convert
  strcpy(elemcopy, ":") == 0
into
  elemcopy[0] == ':' && elemcopy[1] == '\0'
assuming the relevant header (<string.h>) is in scope.  (I was under the
impression that gcc did this).

Peter