From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=FROM_EXCESS_BASE64, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2E352C48BD7 for ; Thu, 27 Jun 2019 16:29:46 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 063602133F for ; Thu, 27 Jun 2019 16:29:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 063602133F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:52424 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hgXHN-0000Ag-9D for qemu-devel@archiver.kernel.org; Thu, 27 Jun 2019 12:29:45 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:42485) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hgWrS-0005Ps-Az for qemu-devel@nongnu.org; Thu, 27 Jun 2019 12:03:01 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hgWrP-0003Dg-Vh for qemu-devel@nongnu.org; Thu, 27 Jun 2019 12:02:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41378) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hgWrP-0002zG-Ot for qemu-devel@nongnu.org; Thu, 27 Jun 2019 12:02:55 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B78423004425; Thu, 27 Jun 2019 16:02:23 +0000 (UTC) Received: from redhat.com (ovpn-112-68.ams2.redhat.com [10.36.112.68]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 98A89600CC; Thu, 27 Jun 2019 16:02:21 +0000 (UTC) Date: Thu, 27 Jun 2019 17:02:18 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster Message-ID: <20190627160218.GO12358@redhat.com> References: <87tvcbc9ul.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87tvcbc9ul.fsf@dusky.pond.sub.org> User-Agent: Mutt/1.11.4 (2019-03-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Thu, 27 Jun 2019 16:02:28 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] Should configure --enable-debug add -Og to CFLAGS? X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Peter Maydell , qemu-devel@nongnu.org, Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Jun 27, 2019 at 05:43:30PM +0200, Markus Armbruster wrote: > The fine manual advises: > > '-O0' > Reduce compilation time and make debugging produce the expected > results. This is the default. > [...] > '-Og' > Optimize debugging experience. '-Og' should be the optimization > level of choice for the standard edit-compile-debug cycle, offering > a reasonable level of optimization while maintaining fast > compilation and a good debugging experience. It is a better choice > than '-O0' for producing debuggable code because some compiler > passes that collect debug information are disabled at '-O0'. > > Our configure --enable-debug effectively picks -O0. Should it pick -Og > instead? NB, it is the --enable-debug-info option to configure that actually adds the "-g" flag for debug info in objects, and turns off -O2. --enable-debug turns on TCG and Mutex debugging & disables fortify source, but doesn't affect optimization level. Adding -Og to --enable-debug-info would be problematic for Fedora/RHEL distro builds, as we want debugging symbols, but also still want -O2 to be used. Yes, the naming of these options is a trapdoor over a pit of crocodiles :-) Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|