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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id A5FF6C021B8 for ; Tue, 4 Mar 2025 13:44:30 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tpSZ7-0005C8-24; Tue, 04 Mar 2025 08:44:09 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tpSYw-0005BQ-Jd for qemu-devel@nongnu.org; Tue, 04 Mar 2025 08:44:02 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tpSYs-0008PS-KA for qemu-devel@nongnu.org; Tue, 04 Mar 2025 08:43:56 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1741095832; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=BCTGo1CTqjZK1Bf3A6KHZZWoW1Zu+888yicwVodMVL8=; b=a9FezROulNT+K84e7K/TjTn6OLopyjYUeeGHzK1fgAaab9WaUTMckOl0A8AGovwnZ0gaBL ZkPm2RjcX1mVJnYo4GOqKwr298HST2KX8FIGU18xjPYf/jrqVy6Wte6K5U2pveWT2u0c6Y uEZAWcdyWShBg6wJMWBmx3Mm9FTXrN4= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-475-RXxuUOH4NoeHIQyJoFKsWQ-1; Tue, 04 Mar 2025 08:43:43 -0500 X-MC-Unique: RXxuUOH4NoeHIQyJoFKsWQ-1 X-Mimecast-MFC-AGG-ID: RXxuUOH4NoeHIQyJoFKsWQ_1741095822 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C8F8219373D7; Tue, 4 Mar 2025 13:43:41 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.210]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 86E161955E93; Tue, 4 Mar 2025 13:43:39 +0000 (UTC) Date: Tue, 4 Mar 2025 13:43:36 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Cc: Alex =?utf-8?Q?Benn=C3=A9e?= , qemu-devel@nongnu.org, Paolo Bonzini , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau Subject: Re: [RFC PATCH] meson.build: add -gsplit-dwarf to default cflags Message-ID: References: <20250303221703.1291078-1-alex.bennee@linaro.org> <87tt8958tj.fsf@draig.linaro.org> <902997f5-a2c8-4585-a834-5cde5aee98a1@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <902997f5-a2c8-4585-a834-5cde5aee98a1@linaro.org> User-Agent: Mutt/2.2.13 (2024-03-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, Mar 04, 2025 at 02:40:31PM +0100, Philippe Mathieu-Daudé wrote: > On 4/3/25 13:11, Daniel P. Berrangé wrote: > > On Tue, Mar 04, 2025 at 11:33:44AM +0000, Alex Bennée wrote: > > > Daniel P. Berrangé writes: > > > > > > > On Mon, Mar 03, 2025 at 10:17:03PM +0000, Alex Bennée wrote: > > > > > This option is supported by both gcc (since 4.7) and clang (since > > > > > 7.0). Not only does this make the linkers job easier by reducing the > > > > > amount of ELF it needs to parse it also reduces the total build size > > > > > quite considerably. In my case a default build went from 5.8G to 3.9G. > > > > > > > > I've not come across this option before, but the docs say > > > > > > > > ‘-gsplit-dwarf’ > > > > If DWARF debugging information is enabled, separate as much > > > > debugging information as possible into a separate output file with > > > > the extension ‘.dwo’. This option allows the build system to avoid > > > > linking files with debug information. To be useful, this option > > > > requires a debugger capable of reading ‘.dwo’ files. > > > > > > > > In Fedora and RHEL we build QEMU will full debug enabled, and then a feature > > > > of the distro RPM build config will post-process all ELF files to extract > > > > the debug info into files that we store under /usr/lib/debug. eg for > > > > /usr/bin/qemu-system-x86_64, we get a separate > > > > /usr/lib/debug/bin/qemu-system-x86_64-9.1.3-1.fc41.x86_64.debug, and > > > > tools like GDB, etc know to look for these separate files. > > > > > > A modern gdb can certainly handle fetching the debug out of the .dwo > > > files when debugging. > > > > See this response from one of the upstream GCC maintainers pretty much > > recommending against (on by default) use of -gsplit-dwarf: > > > > https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/thread/RXA55BTO62NWWHCTUFYGEVHJKZPL5EKE/ > > Jakub said: > > "it can be useful for fast modify/rebuild/test cycles during > development, but is something that is really undesirable for > the distro builds." > > Do distro use --enable-debug by default? Otherwise it might be > useful to add it for developers. We don't have --enable-debug in Fedora/RHEL, and I doubt other distros would enable it given it turns off all optimization as well as introducing other static debug overheads. With 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 :|