From owner-freebsd-questions@FreeBSD.ORG  Wed Oct 17 10:27:20 2012
Return-Path: <owner-freebsd-questions@FreeBSD.ORG>
Delivered-To: freebsd-questions@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52])
 by hub.freebsd.org (Postfix) with ESMTP id A30D769A
 for <freebsd-questions@freebsd.org>; Wed, 17 Oct 2012 10:27:20 +0000 (UTC)
 (envelope-from bennett@cs.niu.edu)
Received: from mp.cs.niu.edu (mp.cs.niu.edu [131.156.145.41])
 by mx1.freebsd.org (Postfix) with ESMTP id 715CE8FC16
 for <freebsd-questions@freebsd.org>; Wed, 17 Oct 2012 10:27:17 +0000 (UTC)
Received: from mp.cs.niu.edu (bennett@localhost [127.0.0.1])
 by mp.cs.niu.edu (8.14.3/8.14.3) with ESMTP id q9HAQLBD004122;
 Wed, 17 Oct 2012 05:26:21 -0500 (CDT)
Date: Wed, 17 Oct 2012 05:26:21 -0500 (CDT)
From: Scott Bennett <bennett@cs.niu.edu>
Message-Id: <201210171026.q9HAQLRC004121@mp.cs.niu.edu>
To: mail@ozzmosis.com
Subject: Re: clang options question
Cc: freebsd-questions@freebsd.org
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-questions>, 
 <mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
 <mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 17 Oct 2012 10:27:20 -0000

     On Wed, 17 Oct 2012 04:25:14 +1100 andrew clarke <mail@ozzmosis.com>
wrote:
>On Tue 2012-10-16 10:52:36 UTC-0500, Scott Bennett (bennett@cs.niu.edu) wrote:
>
>> From looking at the clang(1) man page, it is not clear to me what the
>> difference is between the -arch option and the -march= option.  Would
>> someone please summarize the difference(s) for me?  Thanks much!
>
>>From the users POV, clang is supposed to be a drop-in replacement for
>gcc, where -arch is also an option. Looking online though, it would
>appear it's an Apple Darwin (OS X) only feature of gcc for generating
>universal binaries.

     Oh.  Okay.  Thanks for the Darwin info, too.  I hadn't known that
OS X had carried on NEXTSTEP's support for fat binaries.
>
>The question is a bit academic as it doesn't actually do anything in
>FreeBSD, at least not for me:
>
>$ clang -o hello -arch x86_64 hello.c
>clang: warning: argument unused during compilation: '-arch x86_64'
>
>$ clang -v
>clang version 3.1 (branches/release_31)
>Target: amd64-portbld-freebsd8.3
>Thread model: posix
>
>Nor in Linux (an old version, admittedly):
>
>$ clang -o hello -arch i386 hello.c
>clang: warning: argument unused during compilation: '-arch i386'
>
>$ clang -v
>clang version 1.1 (branches/release_27)
>Target: x86_64-pc-linux-gnu
>Thread model: posix
>
     I see.  So it's just decoration for compatibility with gcc and
something to worry about.  Thanks very much for the response.


                                  Scott Bennett, Comm. ASMELG, CFIAG
**********************************************************************
* Internet:       bennett at cs.niu.edu                              *
*--------------------------------------------------------------------*
* "A well regulated and disciplined militia, is at all times a good  *
* objection to the introduction of that bane of all free governments *
* -- a standing army."                                               *
*    -- Gov. John Hancock, New York Journal, 28 January 1790         *
**********************************************************************