From owner-freebsd-arch@FreeBSD.ORG Fri Aug 15 00:41:15 2014 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id EF6D5D8E; Fri, 15 Aug 2014 00:41:14 +0000 (UTC) Received: from elvis.mu.org (elvis.mu.org [192.203.228.196]) by mx1.freebsd.org (Postfix) with ESMTP id D6D2B27B1; Fri, 15 Aug 2014 00:41:14 +0000 (UTC) Received: from u10-2-16-021.office.norse-data.com (unknown [50.204.88.51]) by elvis.mu.org (Postfix) with ESMTPSA id 92753346DE3D; Thu, 14 Aug 2014 17:41:14 -0700 (PDT) Message-ID: <53ED578B.6070205@freebsd.org> Date: Thu, 14 Aug 2014 17:42:51 -0700 From: Alfred Perlstein Organization: FreeBSD User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:31.0) Gecko/20100101 Thunderbird/31.0 MIME-Version: 1.0 To: Warner Losh , John Baldwin Subject: Re: XML Output: libxo - provide single API to output TXT, XML, JSON and HTML References: <20140814052648.GM2737@kib.kiev.ua> <201408140606.s7E66XXA091972@idle.juniper.net> <20140814085257.GN2737@kib.kiev.ua> <201408140847.00573.jhb@freebsd.org> <94A47A7D-89C9-4504-B669-2A5EDA80373B@bsdimp.com> In-Reply-To: <94A47A7D-89C9-4504-B669-2A5EDA80373B@bsdimp.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit X-Mailman-Approved-At: Fri, 15 Aug 2014 02:55:11 +0000 Cc: Marcel Moolenaar , Phil Shafer , John-Mark Gurney , "Simon J. Gerraty" , arch@freebsd.org, Poul-Henning Kamp , freebsd-arch , Konstantin Belousov X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 15 Aug 2014 00:41:15 -0000 On 8/14/14 9:13 AM, Warner Losh wrote: > On Aug 14, 2014, at 6:47 AM, John Baldwin wrote: > >>>> Marking the binary with a libxo-specific note tells the caller that >>>> the binary is capable of rendering its output in a non-traditional >>>> style and gives the caller a means of triggering those styles of >>>> output. In the libxo-enabled world, I see this as vital information >>>> the caller needs to initialize the environment in which the command >>>> will be run. Isn't this exactly the sort of information ELF targets >>>> for note sections? >>> How binary format has any relevance for an application level feature ? >>> What would you do with the binaries which permissions are 'r-s--x--x', >>> which is not unexpected for the tools which gather system information >>> and have to access things like /dev/mem ? >>> >>> You removed and did not answered a crusial question, which is a litmus >>> test for your proposal. Namely, how presence of the proposed note in >>> the binary is different from DT_NEEDED tag for your library ? >> Yes, checking DT_NEEDED for libxo.so is the first thing I thought of as well. >> It is equivalent to 'ldd foo | grep libxo'. > Doesn’t work for static binaries, nor for cases where libxo is linked in by a > library indirectly, nor for when the command is a shell script that may > invoke a command that supports this output, nor for a python script that > implements this output, etc. > > My question for people advocating this method: Why not require all commands > that generate this kind of output to support a standard command line option > that causes the command to print nothing and return 0 if it supports reporting, > or anything else if it doesn’t (return 0 with output, or return non-zero with or without > output). This would handle the more complicated implementation issues with using > DT_NEEDED and/or the ELF note, be more in line with how things are traditionally > done, and offer greater flexibility of implementation. > > Warner This is a decent idea, however the problem is firstly that most short-opts are taken, second issue is that adding getopt_long to a whole slew of programs will make the effort take a long time. It's really better to limit scope of this such that we are just making machine readable output. -Alfred