From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 21864 invoked by alias); 29 Apr 2019 20:10:19 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 21855 invoked by uid 89); 29 Apr 2019 20:10:18 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-4.6 required=5.0 tests=AWL,BAYES_50,SPF_PASS autolearn=ham version=3.3.1 spammy=H*u:Intel, H*UA:Intel, H*r:sk:server-, HX-Languages-Length:662 X-HELO: mx2.freebsd.org Received: from mx2.freebsd.org (HELO mx2.freebsd.org) (8.8.178.116) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 29 Apr 2019 20:10:17 +0000 Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (Client CN "mx1.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx2.freebsd.org (Postfix) with ESMTPS id DBEC69846F; Mon, 29 Apr 2019 20:10:14 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Received: from smtp.freebsd.org (smtp.freebsd.org [IPv6:2610:1c1:1:606c::24b:4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "smtp.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id C9BF170DF3; Mon, 29 Apr 2019 20:10:13 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Received: from John-Baldwins-MacBook-Pro-3.local (ralph.baldwin.cx [66.234.199.215]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client did not present a certificate) (Authenticated sender: jhb) by smtp.freebsd.org (Postfix) with ESMTPSA id 4F56D10A8F; Mon, 29 Apr 2019 20:10:13 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Subject: Re: [PATCH 2/2] Change ptype/o to print bit offset To: Tom Tromey , gdb-patches@sourceware.org References: <20190429183105.15973-1-tromey@adacore.com> <20190429183105.15973-3-tromey@adacore.com> From: John Baldwin Openpgp: preference=signencrypt Message-ID: Date: Mon, 29 Apr 2019 20:10:00 -0000 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190429183105.15973-3-tromey@adacore.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: C9BF170DF3 X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org X-Spamd-Result: default: False [-2.94 / 15.00]; local_wl_from(0.00)[FreeBSD.org]; NEURAL_HAM_MEDIUM(-1.00)[-0.999,0]; NEURAL_HAM_SHORT(-0.94)[-0.940,0]; ASN(0.00)[asn:11403, ipnet:2610:1c1:1::/48, country:US]; NEURAL_HAM_LONG(-1.00)[-1.000,0] X-IsSubscribed: yes X-SW-Source: 2019-04/txt/msg00635.txt.bz2 On 4/29/19 11:31 AM, Tom Tromey wrote: > This is better, IMO, because now the "offset" of a bitfield is > consistent with the offset of an ordinary member, referring to its > offset from the start of the structure. I agree with this. This is what I use ptype /o for (to get starting offsets). pahole's format may make sense if the bits were numbered N -> 0 instead of 0 -> N, or if bitfields used "high" bits instead of "low" bits, but the convention I always see is to use 0 for LSB and N for MSB. I'm also assuming that compilers start with the LSB when assigning bits to bitfield members. -- John Baldwin