From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 20178 invoked by alias); 30 Aug 2018 19:06:37 -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 20168 invoked by uid 89); 30 Aug 2018 19:06:36 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-2.8 required=5.0 tests=AWL,BAYES_00,KAM_SHORT,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy= X-HELO: mx1.redhat.com Received: from mx3-rdu2.redhat.com (HELO mx1.redhat.com) (66.187.233.73) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 30 Aug 2018 19:06:35 +0000 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E18A4807A0D0; Thu, 30 Aug 2018 19:06:33 +0000 (UTC) Received: from [127.0.0.1] (ovpn04.gateway.prod.ext.ams2.redhat.com [10.39.146.4]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6C008B27A1; Thu, 30 Aug 2018 19:06:33 +0000 (UTC) Subject: Re: [PATCH 0/9] Add UBSan to the build To: Tom Tromey References: <20180827145620.11055-1-tom@tromey.com> <152ef6ac-cd48-72be-6fae-9397bca2c8b8@redhat.com> <87tvnevw5i.fsf@tromey.com> <00b73eed-01eb-ff51-e81d-35b0d6ae75d9@redhat.com> <8736uv3crj.fsf@tromey.com> Cc: gdb-patches@sourceware.org From: Pedro Alves Message-ID: Date: Thu, 30 Aug 2018 19:06:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <8736uv3crj.fsf@tromey.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-SW-Source: 2018-08/txt/msg00841.txt.bz2 On 08/30/2018 07:55 PM, Tom Tromey wrote: >>>>>> "Pedro" == Pedro Alves writes: > > Pedro> Might be noticeable in "make check" time. > Pedro> If you're doing performance analysis, say, running "make check-perf", or running > Pedro> some use case under "perf", sounds like you'll need to be sure to > Pedro> disable UBSan. I also mildly worry about random people comparing the > Pedro> performance of master GDB or some ftp snapshot against previous GDB versions > Pedro> or against other debuggers and being mislead. If that slowdown is true, I think we > Pedro> should at least document it somewhere more prominently, as I think that so > Pedro> far release vs development mode didn't have much of an impact? > > Anyone doing performance analysis really must compile with -O2 and > disable all the checking. It really does matter, IIRC the sleb/uleb > decoders really suffer without optimization. I think optimization/-O2 is much more obvious. Enabling/disabling the checking so far hasn't been an issue so far, I don't think. > > Pedro> Kind of like how GCC documents --enable-checking, at > Pedro> : > > Pedro> "When you specify this option, the compiler is built to perform internal consistency > Pedro> checks of the requested complexity. This does not change the generated code, but adds > Pedro> error checking within the compiler. This will slow down the compiler and may only work > Pedro> properly if you are building the compiler with GCC. This is ‘yes,extra’ by default when > Pedro> building from SVN or snapshots, but ‘release’ for releases." > > Do we have a similar doc somewhere? I could update it. There's a "configure options" node in the manual. And also a "configure' options" section in gdb/README too. > Also I think this series should update NEWS for the new configure option. /me nods. Thanks, Pedro Alves