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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 B2BA3C43331 for ; Thu, 2 Apr 2020 05:55:00 +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 7354C2078B for ; Thu, 2 Apr 2020 05:55:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fHcrvgjT" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7354C2078B 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]:33670 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jJsod-0000Bk-HZ for qemu-devel@archiver.kernel.org; Thu, 02 Apr 2020 01:54:59 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41950) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jJsnz-0008CR-GK for qemu-devel@nongnu.org; Thu, 02 Apr 2020 01:54:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jJsny-0007eF-5n for qemu-devel@nongnu.org; Thu, 02 Apr 2020 01:54:19 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:34276 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jJsny-0007ad-1l for qemu-devel@nongnu.org; Thu, 02 Apr 2020 01:54:18 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585806856; 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=w+8l5AZwU4kBukbo3rgZU4xOirZHabTV4Y0p8dHV8h4=; b=fHcrvgjTlX1SOos6DnnyDcjzjhEgLDn2UEkEY5hnA3nkdQ48L5bHYw5zqUhwL0IgrfJd4f 6edE/ZSPkmaO4/Fgk/ojBtsipcS3llc5zI6iorN2oZmQpkELIlVX3c9nY81SEp3EeorZWh VXOoCVXa8gTDA9zs37uyYZxlM7oUNOU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-374-Nc6sZ1YLPza7RoKr7_5GJg-1; Thu, 02 Apr 2020 01:54:14 -0400 X-MC-Unique: Nc6sZ1YLPza7RoKr7_5GJg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D32A11005516; Thu, 2 Apr 2020 05:54:13 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-112-69.ams2.redhat.com [10.36.112.69]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 87E1D60BF4; Thu, 2 Apr 2020 05:54:13 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 1048F11385E2; Thu, 2 Apr 2020 07:54:12 +0200 (CEST) From: Markus Armbruster To: Peter Maydell Subject: Re: Questionable aspects of QEMU Error's design References: <87o8sblgto.fsf@dusky.pond.sub.org> Date: Thu, 02 Apr 2020 07:54:11 +0200 In-Reply-To: (Peter Maydell's message of "Wed, 1 Apr 2020 21:15:32 +0100") Message-ID: <87sghmbfgc.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 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: , Cc: Vladimir Sementsov-Ogievskiy , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Peter Maydell writes: > On Wed, 1 Apr 2020 at 10:03, Markus Armbruster wrote: >> >> QEMU's Error was patterned after GLib's GError. Differences include: > > From my POV the major problem with Error as we have it today > is that it makes the simple process of writing code like > device realize functions horrifically boilerplate heavy; > for instance this is from hw/arm/armsse.c: > > object_property_set_link(cpuobj, OBJECT(&s->cpu_container[i]), > "memory", &err); > if (err) { > error_propagate(errp, err); > return; > } > object_property_set_link(cpuobj, OBJECT(s), "idau", &err); > if (err) { > error_propagate(errp, err); > return; > } > object_property_set_bool(cpuobj, true, "realized", &err); > if (err) { > error_propagate(errp, err); > return; > } > > 16 lines of code just to set 2 properties on an object > and realize it. It's a lot of boilerplate and as > a result we frequently get it wrong or take shortcuts > (eg forgetting the error-handling entirely, calling > error_propagate just once for a whole sequence of > calls, taking the lazy approach and using err_abort > or err_fatal when we ought really to be propagating > an error, etc). I haven't looked at 'auto propagation' > yet, hopefully it will help? With that, you can have object_property_set_link(cpuobj, OBJECT(&s->cpu_container[i]), "memory", errp); if (*errp) { return; } object_property_set_link(cpuobj, OBJECT(s), "idau", errp); if (*errp) { return; } object_property_set_bool(cpuobj, true, "realized", errp); if (*errp) { return; } but you have to add ERRP_AUTO_PROPAGATE(); right at the beginning of the function. It's a small improvement. A bigger one is if (object_property_set_link(cpuobj, OBJECT(&s->cpu_container[i]), "memory", errp)) { return; } if (object_property_set_link(cpuobj, OBJECT(s), "idau", errp)) { return; } if (object_property_set_bool(cpuobj, true, "realized", errp)) { return; } This is item "Return value conventions" in the message you replied to. Elsewhere in this thread, I discussed the difficulties of automating the conversion to this style. I think I know how to automate converting the calls to use the bool return value, but converting the functions to return it looks hard. We could do that manually for a modest set of frequently used functions. object.h would top my list.