object: store a pointer to private data

This effectively reverts commit 07998682.

include/vlc_objects.h

@@ -29,6 +29,7 @@
  */
 
 struct vlc_logger;
+struct vlc_object_internals;
 
 /**
  * VLC object common members
@@ -40,6 +41,7 @@ struct vlc_logger;
 struct vlc_common_members
 {
     struct vlc_logger *logger;
+    struct vlc_object_internals *priv;
 
     bool no_interact;
 

src/misc/objects.c

@@ -85,6 +85,8 @@ void *vlc_custom_create (vlc_object_t *parent, size_t length,
     priv->resources = NULL;
 
     vlc_object_t *obj = (vlc_object_t *)(priv + 1);
+
+    obj->obj.priv = priv;
     obj->obj.force = false;
     memset (obj + 1, 0, length - sizeof (*obj)); /* type-specific stuff */
 

src/misc/variables.h

@@ -48,7 +48,7 @@ struct vlc_object_internals
     struct vlc_res *resources;
 };
 
-# define vlc_internals( obj ) (((vlc_object_internals_t*)(VLC_OBJECT(obj)))-1)
+# define vlc_internals(o) ((o)->obj.priv)
 # define vlc_externals( priv ) ((vlc_object_t *)((priv) + 1))
 
 extern void var_DestroyAll( vlc_object_t * );