From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755280Ab0CWQ1b (ORCPT ); Tue, 23 Mar 2010 12:27:31 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:35482 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755238Ab0CWQ11 (ORCPT ); Tue, 23 Mar 2010 12:27:27 -0400 Date: Tue, 23 Mar 2010 13:27:19 -0300 From: Arnaldo Carvalho de Melo To: Peter Zijlstra Cc: Frederic Weisbecker , Masami Hiramatsu , Mark Wielaard , Ingo Molnar , lkml , systemtap , DLE , Paul Mackerras , Mike Galbraith Subject: Re: [PATCH -tip 10/10] perf probe: Accessing members in data structures Message-ID: <20100323162719.GG4066@ghostprotocols.net> References: <20100316220515.32050.82185.stgit@localhost6.localdomain6> <20100316220626.32050.57552.stgit@localhost6.localdomain6> <1268821537.6022.12.camel@springer.wildebeest.org> <4BA12A23.4030109@redhat.com> <20100318032804.GA5045@nowhere> <1269359713.5109.95.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1269359713.5109.95.camel@twins> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.19 (2009-01-05) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Tue, Mar 23, 2010 at 04:55:13PM +0100, Peter Zijlstra escreveu: > On Thu, 2010-03-18 at 04:28 +0100, Frederic Weisbecker wrote: > > On Wed, Mar 17, 2010 at 03:14:43PM -0400, Masami Hiramatsu wrote: > > > Mark Wielaard wrote: > > > > If you find that a problem then you can do like SystemTap does and allow > > > > '.' in place of '->'. In the code you already use the > > > > perf_probe_arg_field ref flag only to check that the DIE gives you the > > > > same information. So you could just drop that and use any separator. > > > > Then you decide based on whether you see a DW_TAG_pointer_type. This > > > > gives the user some extra flexibility by letting them not having to care > > > > about specifying extra type information already available elsewhere. > > > Thanks, when designing this feature, I considered it too. > > > Since perf probe already support displaying source code by --line option, > > > users will read the probed code itself and try to probe it. In that case, > > > I think they naturally use '.' and '->' as they read (they might try to > > > copy & paste it). > > > So, I think that it would be good to support both of '.' and '->' as > > > they are used in the code, because it will not confuse users. > > And lets people use what is common for them: expressions that follow > > C rules in the context. > > And those who will be more familiar with perf probe will know they can > > use the simplified "." based scheme. > I'd expect a syntax error when I mix up '.' and '->'. Yup, I'd stick with following the C language rules. - Arnaldo