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 AFA8DCAC59A for ; Fri, 19 Sep 2025 12:08:12 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uzZst-0000UY-Cl; Fri, 19 Sep 2025 08:06:41 -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 1uzZsg-0000Qv-Rj for qemu-devel@nongnu.org; Fri, 19 Sep 2025 08:06:28 -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 1uzZsX-0007GP-Hc for qemu-devel@nongnu.org; Fri, 19 Sep 2025 08:06:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1758283575; 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=T01AH818qeNeowtpwxea0ArQoFwC0ja08QtMrfMfTF4=; b=Y9+3sob5v/ZjJJgcspM9bPrB/LTLBGNDvF2J12JXuSdEvjOK47cLhyY6Y/b7xk0Go4L1oH eb+BWDqLNrdIjC4fh7K6J13E47Jx7VFRKGZwDTPFCib1UweRRQ07bbV9bS0+XBY5SQOIa8 YN9yGPuBiVjIw4WBcMWTkpYAbHSzacM= 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-206-F38_89h1O6G11tso2B32eA-1; Fri, 19 Sep 2025 08:06:14 -0400 X-MC-Unique: F38_89h1O6G11tso2B32eA-1 X-Mimecast-MFC-AGG-ID: F38_89h1O6G11tso2B32eA_1758283573 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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 4972D1800293; Fri, 19 Sep 2025 12:06:13 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.33]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 009EE180035E; Fri, 19 Sep 2025 12:06:12 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 3855521E6A27; Fri, 19 Sep 2025 14:06:10 +0200 (CEST) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Cc: qemu-devel@nongnu.org, Paolo Bonzini , Eduardo Habkost Subject: Re: [PATCH] qom: use ERRP_GUARD in user_creatable_complete In-Reply-To: ("Daniel P. =?utf-8?Q?Berrang?= =?utf-8?Q?=C3=A9=22's?= message of "Fri, 19 Sep 2025 12:41:56 +0100") References: <20250919101504.1503735-1-berrange@redhat.com> <87cy7m3cj9.fsf@pond.sub.org> Date: Fri, 19 Sep 2025 14:06:10 +0200 Message-ID: <87v7lezlxp.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 3.4.1 on 10.30.177.111 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: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.105, 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_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, T_SPF_TEMPERROR=0.01 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Daniel P. Berrang=C3=A9 writes: > On Fri, Sep 19, 2025 at 01:30:18PM +0200, Markus Armbruster wrote: >> Daniel P. Berrang=C3=A9 writes: >>=20 >> > With error_propagate, the stack trace from any error_abort/fatal >> > usage will start from the error_propagate() call, which is largely >> > useless. Using ERRP_GUARD ensures the stack trace starts from >> > the origin that reported the error. >>=20 >> Yes. >>=20 >> I've been chipping at error_propagate() uses on and off for a while. >> There are hundreds left. > > Are there cases where it is still OK to use error_propagate or should > we be looking to eliminate all its usage ? The common use of error_propagate() is to propagate an error received from a function to the caller. This is better done with ERRP_GUARD(). qapi/error.h: * Call a function, receive an error from it, and pass it to the caller * - when the function returns a value that indicates failure, say * false: * if (!foo(arg, errp)) { * handle the error... * } * - when it does not, say because it is a void function: * ERRP_GUARD(); * foo(arg, errp); * if (*errp) { * handle the error... * } * More on ERRP_GUARD() below. * * Code predating ERRP_GUARD() still exists, and looks like this: * Error *err =3D NULL; * foo(arg, &err); * if (err) { * handle the error... * error_propagate(errp, err); // deprecated * } We occasionally store errors on the heap, and use error_propagate() to move them into an @errp argument. qapi/error.h: * Pass an existing error to the caller: * error_propagate(errp, err); * This is rarely needed. When @err is a local variable, use of * ERRP_GUARD() commonly results in more readable code. error_propagate() can also be used to accumulate errors. This cannot be done with ERRP_GUARD(). qapi/error.h: * Receive and accumulate multiple errors (first one wins): * Error *err =3D NULL, *local_err =3D NULL; * foo(arg, &err); * bar(arg, &local_err); * error_propagate(&err, local_err); * if (err) { * handle the error... * } Accumulating errors is commonly a bad idea. Note that g_propagate_error() explicitly prohibits such usage. We deviated from it. The *possibility* of intentional error acculumation makes conversions to ERRP_GUARD() harder. Perhaps we should track down all uses of error accumulation, then change error_propagate() to prohibit it. [...]