From 710467e0340f0fbfbf7e2d422584fdca89d5bc23 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= <marcandre.lureau@redhat.com>
Date: Thu, 4 Oct 2018 04:28:37 -0400
Subject: [PATCH] qom/object: add some interface asserts

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

Backports commit 422ca1432f7b44f2a9f3ad94a65d36927da021fa from qemu
---
 qemu/qom/object.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/qemu/qom/object.c b/qemu/qom/object.c
index 7e8334da..591747fd 100644
--- a/qemu/qom/object.c
+++ b/qemu/qom/object.c
@@ -273,7 +273,18 @@ static void type_initialize(struct uc_struct *uc, TypeImpl *ti)
 
     ti->class_size = type_class_get_size(uc, ti);
     ti->instance_size = type_object_get_size(uc, ti);
+    if (ti->instance_size == 0) {
+        ti->abstract = true;
+    }
 
+    if (type_is_ancestor(uc, ti, uc->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(uc, ti);