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bh=vwR77u+189LL/UU2UMYCw+MeSbcf/LyW1EVg0RVjA/Y=; b=KVqoEp17XnV81CKB0R72ykxjMsqiSrvSz8DaUjdYBL4oDlePT3VnRmPAK2XH+h1P/0GFlm KUXm5uG3kXTCfnzWDWbOjrRTSl6BYhAVPrsuAraNsGduXUS00z/dIJgY6L8ng2abPGaM7r F2OCoFbIxsczYcjDpdoOD8v5q1rXeWM= 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-587-Ofd0NNSrO2a7RyFumJx5oA-1; Thu, 28 Jan 2021 05:57:46 -0500 X-MC-Unique: Ofd0NNSrO2a7RyFumJx5oA-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 70210180A086 for ; Thu, 28 Jan 2021 10:57:45 +0000 (UTC) Received: from merkur.fritz.box (ovpn-115-102.ams2.redhat.com [10.36.115.102]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 816426F80A; Thu, 28 Jan 2021 10:57:44 +0000 (UTC) Date: Thu, 28 Jan 2021 11:57:42 +0100 From: Kevin Wolf To: Markus Armbruster Subject: Re: [PATCH 3/6] qapi: Simplify full_name_nth() in qobject-input-visitor Message-ID: <20210128105742.GA5361@merkur.fritz.box> References: <20201112172850.401925-1-kwolf@redhat.com> <20201112172850.401925-4-kwolf@redhat.com> <87ft2mpjon.fsf@dusky.pond.sub.org> <20210127214242.GG6090@merkur.fritz.box> <87mtwtfqw2.fsf@dusky.pond.sub.org> MIME-Version: 1.0 In-Reply-To: <87mtwtfqw2.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 28.01.2021 um 08:43 hat Markus Armbruster geschrieben: > Kevin Wolf writes: > > > 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). > > See, I can write impenetrable comments with the best of them! > > The spot that talks about @name is in visitor.h: > > * The @name parameter of visit_type_FOO() describes the relation > * between this QAPI value and its parent container. When visiting > * the root of a tree, @name is ignored; when visiting a member of an > * object, @name is the key associated with the value; when visiting a > * member of a list, @name is NULL; and when visiting the member of an > * alternate, @name should equal the name used for visiting the > * alternate. > > Many contracts in the same file refer back to it like this: > > * @name expresses the relationship of this object to its parent > * container; see the general description of @name above. > > The contract here doesn't. > > >> 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. > > Yes, the generated visitors always exhaust the list. But virtual walks > needn't. Ah. Okay, I'll add the bool parameter then. Kevin