From: Marc-André Lureau <marcandre.lureau@redhat.com>

An interface can't have any instance size or callback, or itself
implement other interfaces (this is unsupported).

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20180912125303.29158-1-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 qom/object.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/qom/object.c b/qom/object.c
index 75d1d48..9222b23 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -286,7 +286,14 @@ static void type_initialize(TypeImpl *ti)
     if (ti->instance_size == 0) {
         ti->abstract = true;
     }
-
+    if (type_is_ancestor(ti, type_interface)) {
+        assert(ti->instance_size == 0);
+        assert(ti->abstract);
+        assert(!ti->instance_init);
+        assert(!ti->instance_post_init);
+        assert(!ti->instance_finalize);
+        assert(!ti->num_interfaces);
+    }
     ti->class = g_malloc0(ti->class_size);
 
     parent = type_get_parent(ti);
-- 
1.8.3.1