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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 99E7BC433EF for ; Thu, 28 Oct 2021 15:33:49 +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 327B0610C7 for ; Thu, 28 Oct 2021 15:33:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 327B0610C7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:51286 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mg7PY-0000tT-70 for qemu-devel@archiver.kernel.org; Thu, 28 Oct 2021 11:33:48 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:45084) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mg7OF-0007kJ-CD for qemu-devel@nongnu.org; Thu, 28 Oct 2021 11:32:27 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:28324) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mg7OD-0002t7-LJ for qemu-devel@nongnu.org; Thu, 28 Oct 2021 11:32:27 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1635435144; h=from:from:reply-to: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=57LrMt9xK62X+TLYo56CEkc3biNj5LChvQMnItBX74s=; b=NXEjvHWhq1tbKXagpN2Jdxk1pnfN5krEWyDwqTnSl/p7xtRz2xhuO0tXp64w6gLwqMwayZ e/qnOc2hmMMLgRzHuTkkgpmw2SeYS+qBmkp0FteLthLpafHNHT76gYNHDMM4CO71EMhsUx XcyU90oPQAwIt271HDXAH11AcL4uTuE= 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-296-G73z6KG-M6GboaKqyfvPvg-1; Thu, 28 Oct 2021 11:32:21 -0400 X-MC-Unique: G73z6KG-M6GboaKqyfvPvg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D98FF802B4F; Thu, 28 Oct 2021 15:32:19 +0000 (UTC) Received: from redhat.com (unknown [10.39.195.37]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 276791017E37; Thu, 28 Oct 2021 15:31:59 +0000 (UTC) Date: Thu, 28 Oct 2021 16:31:56 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster Subject: Re: [PATCH v3 04/19] docs/devel: add example of command returning unstructured text Message-ID: References: <20210930132349.3601823-1-berrange@redhat.com> <20210930132349.3601823-5-berrange@redhat.com> <87r1c5nr4d.fsf@dusky.pond.sub.org> MIME-Version: 1.0 In-Reply-To: <87r1c5nr4d.fsf@dusky.pond.sub.org> User-Agent: Mutt/2.0.7 (2021-05-04) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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_LOW=-0.7, RCVD_IN_MSPIKE_H2=-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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Laurent Vivier , Thomas Huth , Eduardo Habkost , David Hildenbrand , Michael Roth , Cornelia Huck , Yuval Shaia , qemu-devel@nongnu.org, Peter Xu , "Dr. David Alan Gilbert" , Halil Pasic , Christian Borntraeger , qemu-s390x@nongnu.org, Gerd Hoffmann , Paolo Bonzini , Richard Henderson , Eric Blake Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Oct 28, 2021 at 04:47:14PM +0200, Markus Armbruster wrote: > Daniel P. Berrangé writes: > > > This illustrates how to add a QMP command returning unstructured text, > > following the guidelines added in the previous patch. The example uses > > a simplified version of 'info roms'. > > > > Signed-off-by: Daniel P. Berrangé > > --- > > docs/devel/writing-monitor-commands.rst | 87 ++++++++++++++++++++++++- > > 1 file changed, 86 insertions(+), 1 deletion(-) > > +Implementing the HMP command > > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > + > > +Now that the QMP command is in place, we can also make it available in > > +the human monitor (HMP) as shown in previous examples. The HMP > > +implementations will all look fairly similar, as all they need do is > > +invoke the QMP command and then print the resulting text or error > > +message. Here's the implementation of the "info roms" HMP command:: > > + > > + void hmp_info_roms(Monitor *mon, const QDict *qdict) > > + { > > + Error err = NULL; > > + g_autoptr(HumanReadableText) info = qmp_x_query_roms(&err); > > + > > + if (err) { > > + error_report_err(err); > > + return; > > + } > > There's hmp_handle_error(). > > If it returned whether there's an error, we could write > > if (hmp_handle_error(err)) { > return; > } I'll add a return value to hmp_handle_error and update existing callers where appropriate > > Of course, qmp_x_query_roms() can't fail, so we could just as well do > > g_autoptr(HumanReadableText) info = qmp_x_query_roms(&error_abort); > > Okay as long as we show how to report errors in HMP commands > *somewhere*, but the use of &error_abort needs explaining. Not sure > that's an improvement here. For the sake of illustration I think I'll stick with hmp_handle_error and not &error_abort. In fact following Dave's feedback, I've added a helper to provide the HMP implementation with no code required in the no-arg case. > Aside: the existing examples show questionable error handling. The > first one uses error_get_pretty() instead of hmp_handle_error(). The > other two throw away the error they get from the QMP command, and report > "Could not query ..." instead, which is a bit of an anti-pattern. I'll fix those examples > > > + monitor_printf(mon, "%s\n", info->human_readable_text); > > Sure you want to print an extra newline? Opps, mistake. > If not, then consider > > monitor_puts(mon, info->human_readable_text); I'd prefer "%s", since it avoids danger of the human readable text possibly containing a '%' sign that trips up printf. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|