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 7B899C433FE for ; Thu, 30 Sep 2021 13:22:47 +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 ECD5061139 for ; Thu, 30 Sep 2021 13:22:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org ECD5061139 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=crudebyte.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:43778 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mVw1N-0006IB-3u for qemu-devel@archiver.kernel.org; Thu, 30 Sep 2021 09:22:45 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33612) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mVvz8-0003qd-Rm for qemu-devel@nongnu.org; Thu, 30 Sep 2021 09:20:29 -0400 Received: from kylie.crudebyte.com ([5.189.157.229]:52335) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mVvz5-00032q-Kc for qemu-devel@nongnu.org; Thu, 30 Sep 2021 09:20:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=kylie; h=Content-Type:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Content-ID:Content-Description; bh=2UrZC7AQ4ezzXNsyTSmC4lrw5Nc6T6ptNwJ+p37F5SU=; b=pFnh2KoIDr85lPLSIZM20NE+/C nur/eZDzEAACHNuYHKA5aS/zh2n9ZWV3+hY2+9k7I0J402wnZ7gaC6GdbSSY3vLTFOeMZh79fs+FJ i68OhmFEjTSxY4499jk8hFgIoWvrQyP2McSRdFhrHSyoRecEfQJkOkNCqxcBBj2TYsd8a7s2lKrGH +ojDOMUEdRns3y++LOkKLnDtJHEDGgUnIC+TGXA10T+ngVZkqStDBpXbNePymr6dv5ZNIU4wtR6zy JatnNgmPNnDQml6+3bXoz/FS+n/weC6rEHSp/FsWXNruHDY8tOfNCgmU9d/sdtK2Y/dVQgOlvQTlv d0zQu3spRXeMLlm2m/3kvKUmFVCwgT7dDiPzA/Cy4dLjn11kczyy3ap1igIJR6AZXfgG56LvrT0QD SDe/OjEXr+htVDbdRagey19y5wlE/j2ML6X2yROkPOiCivefRULAHXW4RLEjVS17sX4aL40ZP+d1G aVgs9JkFSxZ7Mn22XCi6GP3PiUUC2cFPDZlwedpKhhgdNL2gS0kP7riEzoi8rOHzElPmBY+Xi5no9 LuB/wdUTwV7AC7vyx55aQf4vfLmqf3u89LtKuCrr7unE5awfC29G2idvze5cN/g/WhO96N5ceRZMG GYv6SjRgG5FZfHsYR00eIgROKZs6J+EWUkntRC4e0=; From: Christian Schoenebeck To: qemu-devel@nongnu.org, Daniel =?ISO-8859-1?Q?P=2E_Berrang=E9?= Cc: Richard Henderson , Alex =?ISO-8859-1?Q?Benn=E9e?= , Greg Kurz Subject: Re: [PATCH v2 1/5] qemu/qarray.h: introduce QArray Date: Thu, 30 Sep 2021 15:20:19 +0200 Message-ID: <12467459.urXsdUxXdL@silver> In-Reply-To: References: <3065428.eF6XsjkFDY@silver> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1" Received-SPF: pass client-ip=5.189.157.229; envelope-from=qemu_oss@crudebyte.com; helo=kylie.crudebyte.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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mittwoch, 29. September 2021 19:48:38 CEST Daniel P. Berrang=E9 wrote: > On Wed, Sep 29, 2021 at 07:32:39PM +0200, Christian Schoenebeck wrote: > > On Dienstag, 28. September 2021 18:41:17 CEST Daniel P. Berrang=E9 wrot= e: > > > On Tue, Sep 28, 2021 at 06:23:23PM +0200, Christian Schoenebeck wrote: > > > > On Dienstag, 28. September 2021 15:04:36 CEST Daniel P. Berrang=E9= =20 wrote: > > > > > On Sun, Aug 22, 2021 at 03:16:46PM +0200, Christian Schoenebeck=20 wrote: > > [...] > > > The GLib automatic memory support is explicitly designed to be extendd > > > with support for application specific types. We already do exactly th= at > > > all over QEMU with many calls to G_DEFINE_AUTOPTR_CLEANUP_FUNC(..) to > > > register functions for free'ing specific types, such that you can > > > use 'g_autoptr' with them. > >=20 > > Ok, just to make sure that I am not missing something here, because rea= lly > > if there is already something that does the job that I simply haven't > > seen, then I happily drop this QArray code. >=20 > I don't believe there is anything that currently addresses this well. >=20 > > But AFAICS this G_DEFINE_AUTOPTR_CLEANUP_FUNC() & g_autoptr concept does > > not have any notion of "size" or "amount", right? >=20 > Correct, all it knows is that there's a data type and an associated > free function. Ok, thanks for the clarification. > > So let's say you already have the following type and cleanup function in > > your existing code: > >=20 > > typedef struct MyScalar { > >=20 > > int a; > > char *b; > >=20 > > } MyScalar; > >=20 > > void myscalar_free(MayScalar *s) { > >=20 > > g_free(s->b); > >=20 > > } > >=20 > > Then if you want to use G_DEFINE_AUTOPTR_CLEANUP_FUNC() for an array on > > that scalar type, then you still would need to *manually* write > > additionally a separate type and cleanup function like: > >=20 > > typedef struct MyArray { > >=20 > > MyScalar *s; > > int n; > >=20 > > }; > >=20 > > void myarray_free(MyArray *a) { > >=20 > > for (int i =3D 0; i < a->n; ++i) { > > =20 > > myscalar_free(a->s[i]); > > =20 > > } > > g_free(a); > >=20 > > } > >=20 > > Plus you have to manually populate that field 'n' after allocation. > >=20 > > Am I wrong? >=20 > Yes and no. You can of course manually write all these stuff > as you describe, but since we expect the array wrappers to be > needed for more than one type it makes more sense to have > that all done via macros. >=20 > Your patch contains a DECLARE_QARRAY_TYPE and DEFINE_QARRAY_TYPE > that provide all this reqiured boilerplate code. The essential > difference that I'm suggesting is that the array struct type emitted > by the macro is explicitly visible as a concept to calling code such > that it is used directly used with g_autoptr. I got that, but your preferred user pattern was this: DECLARE_QARRAY_TYPE(Foo); ... g_autoptr(FooArray) foos =3D foo_array_new(n); I don't see a portable way to do upper-case to lower-case conversion with t= he=20 C preprocessor. So you would end up like this instead: g_autoptr(FooArray) foos =3D Foo_array_new(n); Which does not really fit into common QEMU naming conventions either, does = it? And I can help it, I don't see what's wrong in exposing a regular C-array t= o=20 user code. I mean in the Linux kernel for instance it is absolutely normal = to=20 convert from a compound structure to its parent structure. I don't find=20 anything magical about that and it is simply less code and better readable. Best regards, Christian Schoenebeck