[pygobject] check if object is actually a PyGFlag before trying to access g_type

[John Palmieri <johnp src gnome org>]

commit 861369ec59b17f67151813dc2e87c6e86126b954
Author: John (J5) Palmieri <johnp redhat com>
Date:   Tue Sep 13 16:04:31 2011 -0400

    check if object is actually a PyGFlag before trying to access g_type
    
     * we are lucky this bit of code worked for as long as it did but when
       checking if an object is a PyGFlag we can't just rely on looking
       at the g_type field because if a regular gobject is passed in
       as is the case when you compare a long to a gflag, the gobject
       will not have a g_type field.  Accessing a non-existant field
       could at best give you a false positive and at worse read
       memory beyond the bounds of the actual structure passed in

 gi/_gobject/pygobject-private.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/gi/_gobject/pygobject-private.h b/gi/_gobject/pygobject-private.h
index 38a5b64..0166825 100644
--- a/gi/_gobject/pygobject-private.h
+++ b/gi/_gobject/pygobject-private.h
@@ -184,7 +184,7 @@ typedef struct {
 
 extern PyTypeObject PyGFlags_Type;
 
-#define PyGFlags_Check(x) (g_type_is_a(((PyGFlags*)x)->gtype, G_TYPE_FLAGS))
+#define PyGFlags_Check(x) (PyObject_IsInstance(x, &PyGFlags_Type) && g_type_is_a(((PyGFlags*)x)->gtype, G_TYPE_FLAGS))
 
 extern PyObject * pyg_flags_add        (PyObject *   module,
 					const char * type_name,
@@ -194,7 +194,7 @@ extern PyObject * pyg_flags_from_gtype (GType        gtype,
 					int          value);
 
 /* pygenum */
-#define PyGEnum_Check(x) (g_type_is_a(((PyGFlags*)x)->gtype, G_TYPE_ENUM))
+#define PyGEnum_Check(x) (PyObject_IsInstance(x, &PyGEnum_Type) && g_type_is_a(((PyGFlags*)x)->gtype, G_TYPE_ENUM))
 
 typedef struct {
 	PYGLIB_PyLongObject parent;