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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 5BA22C433E0 for ; Wed, 27 Jan 2021 21:44:05 +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 06CB16146D for ; Wed, 27 Jan 2021 21:44:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 06CB16146D 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]:47926 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l4sbb-0002SM-Nh for qemu-devel@archiver.kernel.org; Wed, 27 Jan 2021 16:44:03 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:46274) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l4saT-0001S5-31 for qemu-devel@nongnu.org; Wed, 27 Jan 2021 16:42:53 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:46552) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l4saP-0002rU-MC for qemu-devel@nongnu.org; Wed, 27 Jan 2021 16:42:52 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611783767; 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: in-reply-to:in-reply-to:references:references; bh=9Ji9oWL6eAHcGJogoBDZGTjDf1zooWvorWumD76Mfxs=; b=TzLXiG7AgnFj1cWBBnCFKNRCmKMkUlK56BecS0mRlI5A1pky691AA3m9CLDW4WO/meL50o 72n/6134ImpWJeMTqyvnA3ZPF7G2FBnv+lhKjpiH742sP6hBvLK0pfFxPPd4bJUJIibT7U i8/r/FahcJzR+AzY9AzVpp0Va7sR8B8= 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-551-oY-PeziuP-aEImkwjqWL-Q-1; Wed, 27 Jan 2021 16:42:45 -0500 X-MC-Unique: oY-PeziuP-aEImkwjqWL-Q-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 112D356C21 for ; Wed, 27 Jan 2021 21:42:45 +0000 (UTC) Received: from merkur.fritz.box (ovpn-115-94.ams2.redhat.com [10.36.115.94]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3E58E6F923; Wed, 27 Jan 2021 21:42:44 +0000 (UTC) Date: Wed, 27 Jan 2021 22:42:42 +0100 From: Kevin Wolf To: Markus Armbruster Subject: Re: [PATCH 3/6] qapi: Simplify full_name_nth() in qobject-input-visitor Message-ID: <20210127214242.GG6090@merkur.fritz.box> References: <20201112172850.401925-1-kwolf@redhat.com> <20201112172850.401925-4-kwolf@redhat.com> <87ft2mpjon.fsf@dusky.pond.sub.org> MIME-Version: 1.0 In-Reply-To: <87ft2mpjon.fsf@dusky.pond.sub.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.308, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jsnow@redhat.com, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 27.01.2021 um 14:56 hat Markus Armbruster geschrieben: > Kevin Wolf writes: > > > Instead of counting how many elements from the top of the stack we need > > to ignore until we find the thing we're interested in, we can just > > directly pass the StackObject pointer because all callers already know > > it. > > > > We only need a different way now to tell if we want to know the name of > > something contained in the given StackObject or of the StackObject > > itself. Passing name = NULL is the obvious way to request the latter. > > > > This simplifies the interface and makes it easier to use in cases where > > we have the StackObject, but don't know how many steps down the stack it > > is. > > > > Signed-off-by: Kevin Wolf > > --- > > qapi/qobject-input-visitor.c | 38 ++++++++++++++++++------------------ > > 1 file changed, 19 insertions(+), 19 deletions(-) > > > > diff --git a/qapi/qobject-input-visitor.c b/qapi/qobject-input-visitor.c > > index a00ac32682..1415561828 100644 > > --- a/qapi/qobject-input-visitor.c > > +++ b/qapi/qobject-input-visitor.c > > @@ -87,20 +87,16 @@ static QObjectInputVisitor *to_qiv(Visitor *v) > > } > > > > /* > > - * Find the full name of something @qiv is currently visiting. > > - * @qiv is visiting something named @name in the stack of containers > > - * @qiv->stack. > > - * If @n is zero, return its full name. > > - * If @n is positive, return the full name of the @n-th container > > - * counting from the top. The stack of containers must have at least > > - * @n elements. > > - * The returned string is valid until the next full_name_nth(@v) or > > - * destruction of @v. > > + * Find the full name of something named @name in @so which @qiv is > > + * currently visiting. If @name is NULL, find the full name of @so > > + * itself. > > + * > > + * The returned string is valid until the next full_name_so(@qiv) or > > + * destruction of @qiv. > > How can this distinguish between a list and its member? > > Before the patch: > > * list member: n = 0, name = NULL > * list: n = 1, name = NULL Oh. These two lines were more helpful than the whole function comment before this patch (which doesn't talk about name = NULL at all). > Afterwards? > > Checking... yes, regression. Test case: > > {"execute": "blockdev-add", "arguments": {"driver": "file", "node-name": "blk0", "filename": "tmp.img"}} > {"return": {}} > {"execute": "blockdev-add", "arguments": {"driver": "blkdebug", "node-name": "blk1", "image": "blk0", "take-child-perms": [0]}} > {"error": {"class": "GenericError", "desc": "Invalid parameter type for 'take-child-perms', expected: string"}} > > The second command's reply changes from > > {"error": {"class": "GenericError", "desc": "Invalid parameter type for 'take-child-perms[0]', expected: string"}} > > to > > {"error": {"class": "GenericError", "desc": "Invalid parameter type for 'take-child-perms', expected: string"}} > > The idea of using @so instead of @n may be salvagable. I can always add a bool parameter that tells (independently from @name) whether we want the name of a member or of the container. Though do we really need the name of the container anywhere? The n = 1 case exists in qobject_input_check_list(), but is this a case that can fail? The pattern how lists are intended to be visited seems to be calling visit_next_list() until it returns NULL. The only place where this pattern isn't followed and visit_next_list() is called outside such a loop, so that we can actually run into the error in qobject_input_check_list(), is a test case specifically for this error path. So should we just declare not visiting all list elements a programming error and assert instead of constructing an error message that users will never see? Kevin