virobject: Check if @parent is the first member in class

Our virObject code relies heavily on the fact that the first
member of the class struct is type of virObject (or some
derivation of if). Let's check for that.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

diff --git a/src/util/virobject.h b/src/util/virobject.h
index ed1a117b09b89797321473f8ced6c04fabd75a79..77ebad1e8b783ac6b24f1cdb0b808bdfd5a1d88e 100644 (file)
--- a/src/util/virobject.h
+++ b/src/util/virobject.h
@@ -76,7 +76,8 @@ virClassPtr virClassForObjectRWLockable(void);
 # endif
 
 # define VIR_CLASS_NEW(name, prnt) \
-    (name##Class = virClassNew(prnt, #name, sizeof(name), name##Dispose))
+    verify_expr(offsetof(name, parent) == 0, \
+      (name##Class = virClassNew(prnt, #name, sizeof(name), name##Dispose)))
 
 virClassPtr
 virClassNew(virClassPtr parent,