From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 94899 invoked by alias); 30 Aug 2018 18:56:01 -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 94888 invoked by uid 89); 30 Aug 2018 18:56:00 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-2.9 required=5.0 tests=AWL,BAYES_00,KAM_SHORT,RCVD_IN_DNSWL_NONE,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=Hx-languages-length:1591 X-HELO: gateway36.websitewelcome.com Received: from gateway36.websitewelcome.com (HELO gateway36.websitewelcome.com) (192.185.179.26) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 30 Aug 2018 18:55:59 +0000 Received: from cm10.websitewelcome.com (cm10.websitewelcome.com [100.42.49.4]) by gateway36.websitewelcome.com (Postfix) with ESMTP id 656CB40121698 for ; Thu, 30 Aug 2018 13:00:10 -0500 (CDT) Received: from box5379.bluehost.com ([162.241.216.53]) by cmsmtp with SMTP id vS6LfdzGzBcCXvS6bf7vCu; Thu, 30 Aug 2018 13:55:57 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=tromey.com; s=default; h=Content-Transfer-Encoding:Content-Type:MIME-Version:Message-ID: In-Reply-To:Date:References:Subject:Cc:To:From:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=GsNPFgzH9xFIYY+IcLHrLgN+LwLaK2Fubwx8RchWrI8=; b=Dae/JOTgyx+BsIe9z6XqCYEsk6 pm461akiciXeUbM+8lqlMxBfCUPg1hHdILpCQaxq25aOGDom7eyh8gwn+b2vZpoDyRlfyxpt0UpMY fMlyMBcGLIoXzQrQNEaGL/Q7y; Received: from 75-166-85-72.hlrn.qwest.net ([75.166.85.72]:56130 helo=pokyo) by box5379.bluehost.com with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91) (envelope-from ) id 1fvS6K-0005Lf-SQ; Thu, 30 Aug 2018 13:55:28 -0500 From: Tom Tromey To: Pedro Alves Cc: Tom Tromey , gdb-patches@sourceware.org Subject: Re: [PATCH 0/9] Add UBSan to the build 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> Date: Thu, 30 Aug 2018 18:56:00 -0000 In-Reply-To: <00b73eed-01eb-ff51-e81d-35b0d6ae75d9@redhat.com> (Pedro Alves's message of "Thu, 30 Aug 2018 19:41:41 +0100") Message-ID: <8736uv3crj.fsf@tromey.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-SW-Source: 2018-08/txt/msg00840.txt.bz2 >>>>> "Pedro" =3D=3D 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 t= rue, I think we Pedro> should at least document it somewhere more prominently, as I think t= hat 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. Pedro> Kind of like how GCC documents --enable-checking, at Pedro> : Pedro> "When you specify this option, the compiler is built to perform inte= rnal consistency Pedro> checks of the requested complexity. This does not change the generat= ed 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 =E2=80= =98yes,extra=E2=80=99 by default when Pedro> building from SVN or snapshots, but =E2=80=98release=E2=80=99 for re= leases." Do we have a similar doc somewhere? I could update it. Also I think this series should update NEWS for the new configure option. Tom