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 D0287C433F5 for ; Thu, 30 Sep 2021 13:57:23 +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 8F187619E4 for ; Thu, 30 Sep 2021 13:57:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 8F187619E4 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]:36024 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mVwYs-0001lu-Ps for qemu-devel@archiver.kernel.org; Thu, 30 Sep 2021 09:57:22 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41452) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mVwXF-00077W-DD for qemu-devel@nongnu.org; Thu, 30 Sep 2021 09:55:41 -0400 Received: from kylie.crudebyte.com ([5.189.157.229]:58931) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mVwXD-0006xv-4v for qemu-devel@nongnu.org; Thu, 30 Sep 2021 09:55:41 -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=BWwB7ZjI+JiB5FA1FZi3XDTLBE+4nIFgKpjPsfvT+kQ=; b=lno15Fc5ZkgScRDL04GLMNe9TV b5Muvay/lh6DBRfnrLDqT+csanC0eGwqmFAxMjvegHZvx+orPI3wfWjsZRnJaDX3BvfIhLzHoEzKa jC8PgWPT8l9v4Pt1igyPllsBU6Esdmm9pkfJHn964jQVE+s92uZC3gF4fRTm+wx4Q32Uq0/z+ePSa z+Ym43KejUhDFj8qajv5i3jjh1bLOX8WNqgFm1NNgBmSRihQv+leu11xWhW38Gsk4yb9fQLNFXhDt bXAsq+qciyn+bzZ2jvqByBo2YjiVzzl9jY7eJXDc+E+SHrKh/t2TROYW1csAbxG192bNO7GOJI7uc wrRPGlrrGzWDf8lgYUncREd3z7cHnP9pE3aKWaphunTooEkvosRt3M1HzFX7AodEbUHcK2Rblv012 5dHphxCnc2ldYxyLu5NxghcrCnGom+zccFEVZXeTFjnNDcxsvosKrJ0vDT5XDLsKckJ4BlMIzHtcG M6VZCDMflXQFqX05UFm/wp21uyE5rBbbMVirUbK3i3pPY/4UAdlb0gRlul0l4Cj5aj3tG9TxHbKEm XWVg2Ro72CtOJdsbyrhMSy+HDiOEFJOmJdCBlQ2YC62RwJo9XZfzMOY8K5SeH75WiOWRxrdxepD/B RNHjtT4L6jD5wF+qwQ+wGXHTaDqg/1SE5whFfqVvQ=; From: Christian Schoenebeck To: Daniel =?ISO-8859-1?Q?P=2E_Berrang=E9?= Cc: qemu-devel@nongnu.org, 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 15:55:36 +0200 Message-ID: <4707830.eRlNOxMu1p@silver> In-Reply-To: References: <12467459.urXsdUxXdL@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 Donnerstag, 30. September 2021 15:31:10 CEST Daniel P. Berrang=E9 wrote: > On Thu, Sep 30, 2021 at 03:20:19PM +0200, Christian Schoenebeck wrote: > > On Mittwoch, 29. September 2021 19:48:38 CEST Daniel P. Berrang=E9 wrot= e: > > > 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= =20 wrote: > > > > > On Tue, Sep 28, 2021 at 06:23:23PM +0200, Christian Schoenebeck=20 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 Schoenebe= ck > >=20 > > wrote: > > > > [...] > > > >=20 > > > > > The GLib automatic memory support is explicitly designed to be > > > > > extendd > > > > > with support for application specific types. We already do exactly > > > > > that > > > > > 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 > > > > really > > > > 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. > >=20 > > Ok, thanks for the clarification. > >=20 > > > > So let's say you already have the following type and cleanup functi= on > > > > 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. > >=20 > > I got that, but your preferred user pattern was this: > > DECLARE_QARRAY_TYPE(Foo); > > =20 > > ... > > =20 > > g_autoptr(FooArray) foos =3D foo_array_new(n); > >=20 > > I don't see a portable way to do upper-case to lower-case conversion wi= th > > the>=20 > > C preprocessor. So you would end up like this instead: > > g_autoptr(FooArray) foos =3D Foo_array_new(n); > >=20 > > Which does not really fit into common QEMU naming conventions either, d= oes > > it? > Right, it would need to be a two arg macro: >=20 > DECLARE_QARRAY_TYPE(Foo, foo); >=20 > similar to what we do with macros for declaring QOM types becuase of > the same case conversion needs. >=20 > > And I can help it, I don't see what's wrong in exposing a regular C-arr= ay > > to user code. I mean in the Linux kernel for instance it is absolutely > > normal to convert from a compound structure to its parent structure. I > > don't find anything magical about that and it is simply less code and > > better readable. > QEMU code is not Linux code. We're following the GLib practices for > automatic memory deallocation, and QOM is also modelled on GLib. The > proposal looks magical from the POV of QEMU's code patterns, as it is > not making use of GLib's g_auto* code. Hmm, I start to think whether I should just make it some 9p local utility c= ode=20 for now instead, e.g. "P9Array" or something. Best regards, Christian Schoenebeck