The object_ref/unref methods are intended for use with any subclass of
the base Object. Using "Object *" in the signature is not adding any
meaningful level of type safety, since callers simply use "OBJECT(ptr)"
and this expands to an unchecked cast "(Object *)".

By using "void *" we enable the object_unref() method to be used to
provide support for g_autoptr() with any subclass.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 include/qom/object.h | 4 ++--
 qom/object.c         | 6 ++++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/qom/object.h b/include/qom/object.h
index 0f3a60617c..1f8aa2d48e 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -1035,7 +1035,7 @@ GSList *object_class_get_list_sorted(const char *implements_type,
  * as its reference count is greater than zero.
  * Returns: @obj
  */
-Object *object_ref(Object *obj);
+Object *object_ref(void *obj);
 
 /**
  * object_unref:
@@ -1044,7 +1044,7 @@ Object *object_ref(Object *obj);
  * Decrease the reference count of a object.  A object cannot be freed as long
  * as its reference count is greater than zero.
  */
-void object_unref(Object *obj);
+void object_unref(void *obj);
 
 /**
  * object_property_try_add:
diff --git a/qom/object.c b/qom/object.c
index 00fdf89b3b..b1822a2ef4 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1124,8 +1124,9 @@ GSList *object_class_get_list_sorted(const char *implements_type,
                         object_class_cmp);
 }
 
-Object *object_ref(Object *obj)
+Object *object_ref(void *objptr)
 {
+    Object *obj = OBJECT(objptr);
     if (!obj) {
         return NULL;
     }
@@ -1133,8 +1134,9 @@ Object *object_ref(Object *obj)
     return obj;
 }
 
-void object_unref(Object *obj)
+void object_unref(void *objptr)
 {
+    Object *obj = OBJECT(objptr);
     if (!obj) {
         return;
     }
-- 
2.26.2

On 7/23/20 1:14 PM, Daniel P. Berrangé wrote:
> The object_ref/unref methods are intended for use with any subclass of
> the base Object. Using "Object *" in the signature is not adding any
> meaningful level of type safety, since callers simply use "OBJECT(ptr)"
> and this expands to an unchecked cast "(Object *)".
> 
> By using "void *" we enable the object_unref() method to be used to
> provide support for g_autoptr() with any subclass.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>   include/qom/object.h | 4 ++--
>   qom/object.c         | 6 ++++--
>   2 files changed, 6 insertions(+), 4 deletions(-)

Is it worth a followup patch (probably with Coccinelle) that changes:

object_ref(OBJECT(dev));

to the now-simpler

object_ref(dev);

But I don't think it belongs in this patch, so

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

On Thu, Jul 23, 2020 at 02:04:45PM -0500, Eric Blake wrote:
> On 7/23/20 1:14 PM, Daniel P. Berrangé wrote:
> > The object_ref/unref methods are intended for use with any subclass of
> > the base Object. Using "Object *" in the signature is not adding any
> > meaningful level of type safety, since callers simply use "OBJECT(ptr)"
> > and this expands to an unchecked cast "(Object *)".
> > 
> > By using "void *" we enable the object_unref() method to be used to
> > provide support for g_autoptr() with any subclass.
> > 
> > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> > ---
> >   include/qom/object.h | 4 ++--
> >   qom/object.c         | 6 ++++--
> >   2 files changed, 6 insertions(+), 4 deletions(-)
> 
> Is it worth a followup patch (probably with Coccinelle) that changes:
> 
> object_ref(OBJECT(dev));
> 
> to the now-simpler
> 
> object_ref(dev);

Yes, its worth a cleanup.

> But I don't think it belongs in this patch, so
> 
> Reviewed-by: Eric Blake <eblake@redhat.com>

Regards,
Daniel
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