qom: Add class_base_init

The class_base_init TypeInfo callback was present in one of the early
QOM versions but removed (on my request...) before committing.  We
will need it soon, add it.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NAnthony Liguori <aliguori@us.ibm.com>
Signed-off-by: NAndreas Färber <afaerber@suse.de>

include/qemu/object.h

@@ -291,10 +291,15 @@ struct Object
  *   has occurred to allow a class to set its default virtual method pointers.
  *   This is also the function to use to override virtual methods from a parent
  *   class.
+ * @class_base_init: This function is called for all base classes after all
+ *   parent class initialization has occurred, but before the class itself
+ *   is initialized.  This is the function to use to undo the effects of
+ *   memcpy from the parent class to the descendents.
  * @class_finalize: This function is called during class destruction and is
  *   meant to release and dynamic parameters allocated by @class_init.
- * @class_data: Data to pass to the @class_init and @class_finalize functions.
- *   This can be useful when building dynamic classes.
+ * @class_data: Data to pass to the @class_init, @class_base_init and
+ *   @class_finalize functions.  This can be useful when building dynamic
+ *   classes.
  * @interfaces: The list of interfaces associated with this type.  This
  *   should point to a static array that's terminated with a zero filled
  *   element.
@@ -312,6 +317,7 @@ struct TypeInfo
     size_t class_size;
 
     void (*class_init)(ObjectClass *klass, void *data);
+    void (*class_base_init)(ObjectClass *klass, void *data);
     void (*class_finalize)(ObjectClass *klass, void *data);
     void *class_data;
 

qom/object.c

@@ -45,6 +45,7 @@ struct TypeImpl
     size_t instance_size;
 
     void (*class_init)(ObjectClass *klass, void *data);
+    void (*class_base_init)(ObjectClass *klass, void *data);
     void (*class_finalize)(ObjectClass *klass, void *data);
 
     void *class_data;
@@ -112,6 +113,7 @@ TypeImpl *type_register(const TypeInfo *info)
     ti->instance_size = info->instance_size;
 
     ti->class_init = info->class_init;
+    ti->class_base_init = info->class_base_init;
     ti->class_finalize = info->class_finalize;
     ti->class_data = info->class_data;
 
@@ -232,6 +234,13 @@ static void type_initialize(TypeImpl *ti)
         memcpy((void *)ti->class + sizeof(ObjectClass),
                (void *)parent->class + sizeof(ObjectClass),
                parent->class_size - sizeof(ObjectClass));
+
+        while (parent) {
+            if (parent->class_base_init) {
+                parent->class_base_init(ti->class, ti->class_data);
+            }
+            parent = type_get_parent(parent);
+        }
     }
 
     memset((void *)ti->class + class_size, 0, ti->class_size - class_size);