Re: [Qemu-devel] [PATCH v4 5/8] qom: add object_new_with_props / object_new_withpropv constructors

[Daniel P. Berrange]

On Tue, May 19, 2015 at 05:52:14PM +0200, Andreas Färber wrote:
> Am 13.05.2015 um 18:14 schrieb Daniel P. Berrange:
> > +Object *object_new_with_propv(const char *typename,
> > +                              Object *parent,
> > +                              const char *id,
> > +                              Error **errp,
> > +                              va_list vargs)
> > +{
> > +    Object *obj;
> > +    ObjectClass *klass;
> > +    Error *local_err = NULL;
> > +
> > +    klass = object_class_by_name(typename);
> > +    if (!klass) {
> > +        error_setg(errp, "invalid object type: %s", typename);
> > +        return NULL;
> > +    }
> > +
> > +    if (object_class_is_abstract(klass)) {
> > +        error_setg(errp, "object type '%s' is abstract", typename);
> > +        return NULL;
> > +    }
> > +    obj = object_new(typename);
> > +
> > +    if (object_set_propv(obj, &local_err, vargs) < 0) {
> > +        goto error;
> > +    }
> > +
> > +    object_property_add_child(parent, id, obj, &local_err);
> > +    if (local_err) {
> > +        goto error;
> > +    }
> > +
> > +    if (object_dynamic_cast(obj, TYPE_USER_CREATABLE)) {
> > +        user_creatable_complete(obj, &local_err);
> > +        if (local_err) {
> > +            object_unparent(obj);
> > +            goto error;
> > +        }
> > +    }
> > +
> > +    object_unref(OBJECT(obj));
> > +    return obj;
> 
> This looks fishy. Either we return obj and need to retain a ref for that
> (caller's responsibility to unref) or we unref it and return void.
> Or am I misreading the code?

Paolo told me on previous posting that object_property_add_child()
holds a reference on 'obj' for as long as it is registered in the
object hierarchy composition. So it sufficient to rely on that long
term reference, and let the caller dispose of the object by calling
object_unparent(obj) when finally done.

Regards,
Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|