From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 31475 invoked by alias); 25 Jan 2016 18:27:43 -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 31461 invoked by uid 89); 25 Jan 2016 18:27:42 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.9 required=5.0 tests=BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=letter X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Mon, 25 Jan 2016 18:27:41 +0000 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (Postfix) with ESMTPS id AB9A518B249; Mon, 25 Jan 2016 18:27:40 +0000 (UTC) Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.phx2.redhat.com [10.5.9.1]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u0PIRciS009789; Mon, 25 Jan 2016 13:27:39 -0500 Message-ID: <56A6691A.3060400@redhat.com> Date: Mon, 25 Jan 2016 18:27:00 -0000 From: Pedro Alves User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Paul_Koning@Dell.com, jhb@freebsd.org CC: gdb-patches@sourceware.org, k.toshihito@yahoo.de Subject: Re: [PATCH] Add a new format letter to dump instructions backward References: <1827952218.466587.1453670934999.JavaMail.yahoo.ref@mail.yahoo.com> <1827952218.466587.1453670934999.JavaMail.yahoo@mail.yahoo.com> <56A609E7.6050903@redhat.com> <2015581.ugHgmqoO9R@ralph.baldwin.cx> <3F40FBEE-2395-4ECC-94A0-A395B35B788C@dell.com> In-Reply-To: <3F40FBEE-2395-4ECC-94A0-A395B35B788C@dell.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SW-Source: 2016-01/txt/msg00631.txt.bz2 On 01/25/2016 06:22 PM, Paul_Koning@Dell.com wrote: > >> On Jan 25, 2016, at 12:52 PM, John Baldwin wrote: >> >> On Monday, January 25, 2016 11:41:27 AM Pedro Alves wrote: >>> On 01/24/2016 09:28 PM, Toshihito Kikuchi wrote: >>> ... >>> #3 - negative repeat counts ? >>> >>> (gdb) x /4i // next 4 instructions >>> (gdb) x /-4i // previous 4 instructions >>> ... >>> #3 feels natural to me. What do you (and others) think? >> >> I think #3 is the most natural as well. I also think this is a >> very useful feature. > > Yes, but how do you do instructions backwards if the instruction length is variable? It is entirely possible that there will be multiple possible answers, and no way to tell which one (if any) is "correct". You disassemble forward starting from the previous known instruction boundary, based on symbol/line info. I haven't looked at the implementation in detail, but from the patch description, that's what I assume the patch is doing. Thanks, Pedro Alves