qom: Introduce object_class_is_abstract()

This lets a caller check if an ObjectClass as returned by, e.g.,
object_class_by_name() is instantiatable.
Signed-off-by: NAndreas Färber <afaerber@suse.de>
Cc: Anthony Liguori <anthony@codemonkey.ws>

include/qom/object.h

@@ -690,6 +690,14 @@ ObjectClass *object_class_get_parent(ObjectClass *klass);
  */
 const char *object_class_get_name(ObjectClass *klass);
 
+/**
+ * object_class_is_abstract:
+ * @klass: The class to obtain the abstractness for.
+ *
+ * Returns: %true if @klass is abstract, %false otherwise.
+ */
+bool object_class_is_abstract(ObjectClass *klass);
+
 /**
  * object_class_by_name:
  * @typename: The QOM typename to obtain the class for.

qom/object.c

@@ -501,6 +501,11 @@ ObjectClass *object_get_class(Object *obj)
     return obj->class;
 }
 
+bool object_class_is_abstract(ObjectClass *klass)
+{
+    return klass->type->abstract;
+}
+
 const char *object_class_get_name(ObjectClass *klass)
 {
     return klass->type->name;