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Mon, 21 Oct 2024 22:23:13 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHYni3e127UIJn8X29NLGhal+BdZBq4gjjsuvOVg3UOp3MSSkKrqrmyyRHzERHE8LL7KCQJuaBut/qZ4w4cj24= X-Received: by 2002:a05:600c:3b9b:b0:431:562a:54be with SMTP id 5b1f17b1804b1-43161627c0dmr162388365e9.9.1729574592850; Mon, 21 Oct 2024 22:23:12 -0700 (PDT) MIME-Version: 1.0 References: <20241021163538.136941-1-pbonzini@redhat.com> <20241021163538.136941-11-pbonzini@redhat.com> <12b03ebb-6bc2-4ffe-99cc-4818b5d992ee@linaro.org> In-Reply-To: <12b03ebb-6bc2-4ffe-99cc-4818b5d992ee@linaro.org> From: Paolo Bonzini Date: Tue, 22 Oct 2024 07:23:01 +0200 Message-ID: Subject: Re: [PATCH v2 10/13] qdev: make properties array "const" To: =?UTF-8?Q?Philippe_Mathieu=2DDaud=C3=A9?= Cc: qemu-devel@nongnu.org, Manos Pitsidianakis , Junjie Mao , =?UTF-8?Q?Daniel_P=2E_Berrang=C3=A9?= , Richard Henderson , Markus Armbruster , Eduardo Habkost Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=170.10.129.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.421, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1.699, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=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: 2.1.29 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-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, Oct 22, 2024 at 6:31=E2=80=AFAM Philippe Mathieu-Daud=C3=A9 wrote: > > -void qdev_property_add_static(DeviceState *dev, Property *prop) > > +void qdev_property_add_static(DeviceState *dev, const Property *prop) > > { > > Object *obj =3D OBJECT(dev); > > ObjectProperty *op; > > @@ -980,7 +980,7 @@ void qdev_property_add_static(DeviceState *dev, Pro= perty *prop) > > field_prop_getter(prop->info), > > field_prop_setter(prop->info), > > prop->info->release, > > - prop); > > + (Property *)prop); > > I like the overall patch idea, but I'm not keen on casting > const to non-const. Should we adapt the callee -- here > object_property_add() -- to also take a const argument? This argument goes into prop->opaque and is passed to all accessor/resolver/finalizers functions. So it would be a much larger change because it needs to change all those functions from "void *opaque" to "const void *opaque". It would also be an issue because some finalizers write to the opaque for good reason: static void object_finalize_child_property( Object *obj, const char *name, void *opaque) { Object *child =3D opaque; if (child->class->unparent) { (child->class->unparent)(child); } child->parent =3D NULL; // <--- here object_unref(child); } So, it's not great but it seems necessary. At least keeping the const within qdev properties makes things "safer" within that realm. Paolo