=== modified file src/object/pdf-obj.h
--- src/object/pdf-obj.h	2011-03-08 20:06:45 +0000
+++ src/object/pdf-obj.h	2011-05-10 01:50:27 +0000
@@ -54,6 +54,12 @@
 
 const pdf_obj_t PDF_OBJ_NULL = {0, 0, NULL};
 
+/* Macro for testing whether the PDF obj is PDF_OBJ_NULL */
+#define PDF_OBJ_IS_NULL(obj) \
+          (((obj).f == PDF_OBJ_NULL.f) && \
+           ((obj).v == PDF_OBJ_NULL.v) && \
+           ((obj).p == PDF_OBJ_NULL.p))
+
 /* A pdf_obj_t variable can be of any of the following types.  */
 
 enum pdf_obj_type_e