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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 76A91C4361B for ; Fri, 18 Dec 2020 19:24:45 +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 F3B6423B84 for ; Fri, 18 Dec 2020 19:24:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F3B6423B84 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]:49390 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kqLMp-000577-Mx for qemu-devel@archiver.kernel.org; Fri, 18 Dec 2020 14:24:43 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:35130) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kqLLE-0004T5-66 for qemu-devel@nongnu.org; Fri, 18 Dec 2020 14:23:04 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:49576) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kqLLC-0004a7-I0 for qemu-devel@nongnu.org; Fri, 18 Dec 2020 14:23:03 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1608319381; 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=YFfH5+W7nZRqRI+qlhjgiOtEzkgWa/B+vtrb4FFmJSA=; b=PkkZugt0ZzRsu9Hs7oszADNcYc0/gB1IvEyU+vEMdsNYTjZ0uvnvTKkqponxE7pFl5xS2h ldhZHa/MQeaY0FY6w4fXkG267j5nd/kckZ0bkqkFQY/Yswx5zNUU+ide8n92HOAz2L4TZw ayEFt4hxenw0yNWAvkJnxNfUnuDOGEQ= 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-455-Qm1wsdZCMnmPEsBOHjMM3A-1; Fri, 18 Dec 2020 14:23:00 -0500 X-MC-Unique: Qm1wsdZCMnmPEsBOHjMM3A-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 2981B802B42 for ; Fri, 18 Dec 2020 19:22:59 +0000 (UTC) Received: from [10.10.112.131] (ovpn-112-131.rdu2.redhat.com [10.10.112.131]) by smtp.corp.redhat.com (Postfix) with ESMTP id CF52860C15; Fri, 18 Dec 2020 19:22:51 +0000 (UTC) Subject: Re: [PATCH 06/12] qapi/source: Add builtin null-object sentinel To: Markus Armbruster References: <20201214235327.1007124-1-jsnow@redhat.com> <20201214235327.1007124-7-jsnow@redhat.com> <87r1nqrtp7.fsf@dusky.pond.sub.org> <9f25c91a-774d-fbe3-3780-5415e7a54524@redhat.com> <87im90k5mr.fsf@dusky.pond.sub.org> From: John Snow Message-ID: Date: Fri, 18 Dec 2020 14:22:50 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.1 MIME-Version: 1.0 In-Reply-To: <87im90k5mr.fsf@dusky.pond.sub.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jsnow@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=jsnow@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, 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: =?UTF-8?Q?Marc-Andr=c3=a9_Lureau?= , qemu-devel@nongnu.org, Eduardo Habkost , Cleber Rosa Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 12/17/20 6:56 AM, Markus Armbruster wrote: > John Snow writes: > >> On 12/16/20 4:22 AM, Markus Armbruster wrote: >>> 2. On error with "no source info", don't crash. >>> I have my doubts on this one. >>> Such an error means the QAPI code generator screwed up, at least >>> in >>> theory. Crashing is only proper. It gets the screwup fixed. >>> >> >> QAPISemError and friends will also halt the generator and don't >> produce output and will fail tests. They aren't less visible or more >> ignorable somehow. >> >>> In practice, errors due to interactions between built-in stuff and >>> user-defined stuff could conceivably escape testing. I can't >>> remember such a case offhand. >>> Will the "no source info" error be more useful than a crash? >>> Possibly. Will it get the screwup fixed? Maybe not. >> >> I don't understand this; if it's an error -- there's no QAPI, there's >> no QEMU. It's definitely getting fixed. >> >> If QAPISourceInfo is primarily used for printing error information, we >> are already in a situation where the generator is hosed and has >> wandered itself into a problem that can't be ignored. >> >> There's no additional value in having python crash twice per every >> crash because we have bad types in our error reporting functions. > > Consider the following scenario. The average developer knows just > enough about QAPI to be dangerous. That's okay; if you had to be a QAPI > expert to modify the QAPI schema, we would have failed. Now meet Joe > Average. He's a good guy. Today his job happens to require extending > the QAPI schema. In a hurry, as usual. So Joe brings his well-honed > voodoo programming skills to bear, and writes something that looks > plausible to him. His build fails. He's not surprised; he's voodoo- > programming after all. However, the error message is less clear than > usual. Something about a '[builtin]' file. There is no '[builtin]' > file. What to do? Obvious! If a bit of voodoo doesn't get you over > the finish line, use more: twiddle the schema until it works. > > If his build failed with a Python backtrace instead, Joe would > immediately know that he ran into a bug in our tooling he should report. > > Again, I don't mean to criticize Joe. I've walked in his shoes myself. > > Worse, Joe was going to see an error about the "None" file or an error about the "[builtin]" file. I understand, though: don't suppress crash messages with opaque crap that doesn't help spot the error. It's just that I don't think that's what is happening here. See lengthy response in other email. --js