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 34580E95A91 for ; Mon, 9 Oct 2023 08:32:55 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qplgn-0005JU-Tb; Mon, 09 Oct 2023 04:32:33 -0400 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 1qplgm-0005Hl-Ud for qemu-devel@nongnu.org; Mon, 09 Oct 2023 04:32:32 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qplgl-0000VH-2m for qemu-devel@nongnu.org; Mon, 09 Oct 2023 04:32:32 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1696840349; 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=oV2qeWKhGtahxPQFRTzJMNNy9fxuV7526nbdg4Trw0A=; b=eRN5/Ig3jqVfNHQAYNaFhgSMWmF8cEid1P0KzPKrkxK/hqtJFgl0780VtwMdtQOKi4h228 UmPZf2jhuUOA9dZ73WXoTRg+kVtjdtjvpTdIPOn68I9Pc+91YwJ+fCf0FbSvkVMOpSbAM0 qq3Jj9UpCK4i6ggO5q0zmmaNInSNggM= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-244-r-LeOhyJNlaR-0y7CHRTUg-1; Mon, 09 Oct 2023 04:32:11 -0400 X-MC-Unique: r-LeOhyJNlaR-0y7CHRTUg-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 568E5810BD9; Mon, 9 Oct 2023 08:32:11 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.42]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9174E400F36; Mon, 9 Oct 2023 08:32:10 +0000 (UTC) Date: Mon, 9 Oct 2023 09:32:07 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Thomas Huth Cc: qemu-devel@nongnu.org, Paolo Bonzini , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: [PATCH 0/2] topic: meson: add more compiler hardening flags Message-ID: References: <20231005173812.966264-1-berrange@redhat.com> <62196cb3-72e4-5db2-c0c4-ec1e74c8d432@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <62196cb3-72e4-5db2-c0c4-ec1e74c8d432@redhat.com> User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.133.124; 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_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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 Mon, Oct 09, 2023 at 09:21:01AM +0200, Thomas Huth wrote: > On 05/10/2023 19.38, Daniel P. Berrangé wrote: > ... > > > > I also tested enabling -ftrapv, to change signed integer > > overflow from wrapping, to trapping instead. This exposed a > > bug in the string-input-visitor which overflows when parsing > > ranges, and exposed the test-int128 code as (harmlessly) > > overflowing during its testing. Both can be fixed, but I'm > > not entirely sure whether -ftrapv is viable or not. I was > > wondering about TCG and whether it has a need to intentionally > > allow integer overflow for any of its instruction emulation > > requirements ? > I'm not an expert when it comes to this question, but as far as I > understood, we are using -fwrapv (with "w", not "t") on purpose, see > meson.build: > > # We use -fwrapv to tell the compiler that we require a C dialect where > # left shift of signed integers is well defined and has the expected > # 2s-complement style results. (Both clang and gcc agree that it > # provides these semantics.) > > And according to the man-page of gcc: > > The options -ftrapv and -fwrapv override each other, > so using -ftrapv -fwrapv on the command-line results > in -fwrapv being effective. > > If I got that right, this means you cannot use -ftrapv with QEMU. Opps, I didn't notice we had -fwrapv in our flags, that is clearly mutually exclusive with -ftrapv, so nothing further to do here. 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 :|