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 D0225CCD185 for ; Wed, 15 Oct 2025 05:51:09 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1v8uPS-00010N-3F; Wed, 15 Oct 2025 01:50:50 -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 1v8uPQ-00010F-Dp for qemu-trivial@nongnu.org; Wed, 15 Oct 2025 01:50:48 -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 1v8uPM-0007Vu-P5 for qemu-trivial@nongnu.org; Wed, 15 Oct 2025 01:50:48 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1760507438; h=from:from: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=doYfQ04zxKVDefG+tjuoJ5edIX9ZvZ5HtUkiz/HfXAs=; b=gFHYjD3ItJLRBPOPOaNqDbh9eDmxgMtE+o97DyNsBbJup8y5D68cL4V75rpIJvEiOto/p0 aJn7lpOn62dgy/StzEChB4RjAjtA74QxOzv0wociQ1gOXNmO3sBkUzOe4KsJHTv1vhaydY LUpA3dvA+eQV1BK9N92gfIpdaejS37o= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-92-pdZXh2k1OHqTGUKYh4e8Kg-1; Wed, 15 Oct 2025 01:50:35 -0400 X-MC-Unique: pdZXh2k1OHqTGUKYh4e8Kg-1 X-Mimecast-MFC-AGG-ID: pdZXh2k1OHqTGUKYh4e8Kg_1760507433 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2F4A118001D1; Wed, 15 Oct 2025 05:50:33 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.19]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4D9F019560AD; Wed, 15 Oct 2025 05:50:32 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id D03E721E6A27; Wed, 15 Oct 2025 07:50:29 +0200 (CEST) From: Markus Armbruster To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Cc: Peter Maydell , qemu-devel@nongnu.org, sstabellini@kernel.org, anthony@xenproject.org, paul@xen.org, edgar.iglesias@gmail.com, xen-devel@lists.xenproject.org, qemu-trivial@nongnu.org Subject: Re: [PATCH] hw/display/xenfb: Replace unreachable code by abort() In-Reply-To: <2cad2907-5a93-4630-856f-7237063eb3ce@linaro.org> ("Philippe =?utf-8?Q?Mathieu-Daud=C3=A9=22's?= message of "Tue, 14 Oct 2025 17:19:31 +0200") References: <20250729111226.3627499-1-armbru@redhat.com> <2cad2907-5a93-4630-856f-7237063eb3ce@linaro.org> Date: Wed, 15 Oct 2025 07:50:29 +0200 Message-ID: <87y0pck922.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@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=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-trivial@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-trivial-bounces+qemu-trivial=archiver.kernel.org@nongnu.org Sender: qemu-trivial-bounces+qemu-trivial=archiver.kernel.org@nongnu.org Philippe Mathieu-Daud=C3=A9 writes: > On 14/10/25 14:59, Peter Maydell wrote: >> On Tue, 14 Oct 2025 at 09:36, Peter Maydell w= rote: >>> >>> On Tue, 29 Jul 2025 at 12:14, Markus Armbruster wro= te: >>>> >>>> xenfb_mouse_event() has a switch statement whose controlling >>>> expression move->axis is an enum InputAxis. The enum values are >>>> INPUT_AXIS_X and INPUT_AXIS_Y, encoded as 0 and 1. The switch has a >>>> case for both axes. In addition, it has an unreachable default label. >>>> This convinces Coverity that move->axis can be greater than 1. It >>>> duly reports a buffer overrun when it is used to subscript an array >>>> with two elements. >>> >>> I think also that Coverity gets confused by QAPI's convention >>> in generated code of defining enumerations like this: >>> >>> typedef enum InputAxis { >>> INPUT_AXIS_X, >>> INPUT_AXIS_Y, >>> INPUT_AXIS__MAX, >>> } InputAxis; >>> >>> Coverity thinks that INPUT_AXIS__MAX might be a valid >>> value it can see in move->axis, because we defined the >>> enum that way. >>> >>> In theory I suppose that since the __MAX value is only >>> there to be an array or enumeration bound Correct. >>> that we could >>> emit code that #defines it rather than making it part >>> of the enum. I'd love that, but it's harder than it has any right to be; see the message Philippe referred to below. >> Also, there's an argument that this function should >> ignore unknown input-axis enum values. If we ever in future >> extend this to support a Z-axis, it would be better to >> ignore the events we can't send, the same way we already >> do for unknown INPUT_EVENT_KIND_BTN button types, rather >> than aborting. No objection. >> But it's not very important, so the >> g_assert_not_reached() will do. >>=20 >> (In some other languages, we'd get a compile failure for >> adding a new value to the enum that we didn't handle. >> But not in C :-)) > > See this thread where it was discussed (until I gave up...): > https://lore.kernel.org/qemu-devel/873564spze.fsf@pond.sub.org/