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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 9ACD7C6FA8B for ; Thu, 22 Sep 2022 17:07:54 +0000 (UTC) Received: from localhost ([::1]:48384 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1obPg1-0001Zb-ES for qemu-devel@archiver.kernel.org; Thu, 22 Sep 2022 13:07:53 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:55524) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1obO7E-00081S-IZ for qemu-devel@nongnu.org; Thu, 22 Sep 2022 11:27:54 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:42896) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1obO7D-00038a-1m for qemu-devel@nongnu.org; Thu, 22 Sep 2022 11:27:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1663860470; 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=mrCP19LB4SryCR63MOFI8bydcwc9GeCZfEg3tdi5P8s=; b=h5Ac6vBIA4NKhtJT6nm8n1o+0woqBdlM/Csg5W0EI4RD6mpC3bHe0/SDmJt0ohxDVy+g7c JVXOZsDv6JEfNy7eZrLuQKyktRaU/JfV5t0ypRi7IOjCUE2hcIYDdu773Dh16cr8TwLxBr gJwK/mjzDJ/Ctx1OUU7nQio2cWAfKWw= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-12-uXlFpvs7MT-uAtI7S9GFxw-1; Thu, 22 Sep 2022 11:27:46 -0400 X-MC-Unique: uXlFpvs7MT-uAtI7S9GFxw-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 7B525872844; Thu, 22 Sep 2022 15:27:46 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.163]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4540D492B1B; Thu, 22 Sep 2022 15:27:46 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 5368E21E6900; Thu, 22 Sep 2022 17:27:43 +0200 (CEST) From: Markus Armbruster To: Kevin Wolf Cc: Claudio Fontana , Daniel P. =?utf-8?Q?Berrang=C3=A9?= , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Paolo Bonzini , Richard Henderson , qemu-devel@nongnu.org, dinechin@redhat.com, Gerd Hoffmann , =?utf-8?Q?Marc?= =?utf-8?Q?-Andr=C3=A9?= Lureau Subject: Re: [PATCH v4 2/3] module: add Error arguments to module_load_one and module_load_qom_one References: <20220908183012.17667-3-cfontana@suse.de> <877d23ekj0.fsf@pond.sub.org> <76775f64-e49a-1c3c-0d73-10d93eff34e4@amsat.org> <87y1ucdirx.fsf@pond.sub.org> <878rmc54cw.fsf@pond.sub.org> <87leqb4ul9.fsf@pond.sub.org> <5f5921fe-6d4f-490b-4328-702a45973bbc@suse.de> <87bkr7mvgr.fsf@pond.sub.org> Date: Thu, 22 Sep 2022 17:27:43 +0200 In-Reply-To: (Kevin Wolf's message of "Thu, 22 Sep 2022 16:54:53 +0200") Message-ID: <87wn9vig40.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@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, 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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Kevin Wolf writes: > Am 22.09.2022 um 14:42 hat Markus Armbruster geschrieben: [...] >> If you have callers that need to distinguish between not found, found >> but bad, found and good, then return three distinct values. >> >> I proposed to return -1 for found but bad (error), 0 for not found (no >> error), and 1 for loaded (no error). > > My intuition with this one was that "not found" is still an error case, > but it's an error case that we need to distinguish from other error > cases. > > Is this one of the rare use cases for error classes? If I remember correctly, "not found" is not actually an error for most callers. If we make it one, these callers have to error_free(). Minor annoyance, especially when you have to add an else just for that. Even if we decide to make it an error, I would not create an error class for it. I like rc = module_load_one(..., errp); if (rc == -ENOENT) { error_free(*errp); } else if (rc < 0) { return; } better than Error *err = NULL; module_load_one(..., &err); if (err && err->class == ERROR_CLASS_NOT_FOUND) { error_free(err); } else if (err) { error_propagate(errp, err); return; } I respect your intuition. Would it still say "error case" when the function is called module_load_if_exists()? Hmm, another thought... a need to distinguish error cases can be a symptom of trying to do too much in one function. We could split this into "look up module" and "actually load it".