eo: Prevent eo_override to be called on an already overridden object

I don't see the point of it but can't be bothered to argue.
For Tom.

2 files changed, 10 insertions, 0 deletions

diff --git a/src/lib/eo/Eo.h b/src/lib/eo/Eo.h
index 58c26b4536..293234a15c 100644
--- a/src/lib/eo/Eo.h
+++ b/src/lib/eo/Eo.h
@@ -452,6 +452,10 @@ EAPI const Eo_Class *eo_class_new(const Eo_Class_Description *desc, const Eo_Cla
  *
  * If @p ops is #NULL, this will revert the @p obj to its original class
  * without any function overrides.
+ *
+ * It is not possible to override a function table of an object when it's
+ * already been overridden. Call eo_override(obj, NULL) first if you really
+ * need to do that.
  */
 EAPI Eina_Bool eo_override(Eo *obj, const Eo_Ops *ops);
 
diff --git a/src/lib/eo/eo.c b/src/lib/eo/eo.c
index 52ba754ff6..a7df2b5a33 100644
--- a/src/lib/eo/eo.c
+++ b/src/lib/eo/eo.c
@@ -1360,6 +1360,12 @@ eo_override(Eo *eo_id, const Eo_Ops *ops)
         _vtable_init(obj->vtable, previous->size);
         _vtable_copy_all(obj->vtable, previous);
      }
+   else
+     {
+        ERR("Function table already overridden, not allowed to override again. "
+            "Call with NULL to reset the function table first.");
+        return EINA_FALSE;
+     }
 
    if (!_eo_class_funcs_set(obj->vtable, ops, obj->klass, klass, EINA_TRUE))
      {