Re: [Qemu-devel] [PATCH 1/5] qom/object: Add a new function object_initialize_as_child()

[Eduardo Habkost <ehabkost@redhat.com>]

On Thu, Jul 12, 2018 at 05:30:59PM +0200, Thomas Huth wrote:
> A lot of code is using the object_initialize() function followed by a call to
> object_property_add_child() to add the newly initialized object as a child of
> the current object. Both functions increase the reference counter of the new
> object, but many spots that call these two functions then forget to drop one
> of the superfluous references. So the newly created object is often not cleaned
> up correctly when the parent is destroyed. In the worst case, this can cause
> crashes, e.g. because device objects are not correctly removed from their
> parent_bus.
> Since this is a common pattern between many code spots, let's introdcue a
> new function that takes care of calling all three required initialization
> functions, first object_initialize(), then object_property_add_child() and
> finally object_unref().
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  include/qom/object.h | 19 +++++++++++++++++++
>  qom/object.c         | 14 ++++++++++++++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/include/qom/object.h b/include/qom/object.h
> index f3d2308..c1b254c 100644
> --- a/include/qom/object.h
> +++ b/include/qom/object.h
> @@ -749,6 +749,25 @@ int object_set_propv(Object *obj,
>  void object_initialize(void *obj, size_t size, const char *typename);
>  
>  /**
> + * object_initialize_as_child:
> + * @parentobj: The parent object to add a property to
> + * @propname: The name of the property
> + * @childobj: A pointer to the memory to be used for the object.
> + * @size: The maximum size available at @obj for the object.
> + * @type: The name of the type of the object to instantiate.
> + * @errp: If an error occurs, a pointer to an area to store the area
> + *
> + * This function will initialize an object. The memory for the object should
> + * have already been allocated. The object will then be added as child property
> + * to a parent with object_property_add_child() function. The returned object
> + * has a reference count of 1, and will be finalized when the last reference is
> + * dropped.
> + */
> +void object_initialize_as_child(Object *parentobj, const char *propname,
> +                                void *childobj, size_t size, const char *type,
> +                                Error **errp);

Why did you use void* instead of Object*?

-- 
Eduardo