(CHECK_POINTER_COMPATIBILITY (&((STRUCT *) 0)->MEMBER, POINTER), \
(STRUCT *) ((char *) (POINTER) - offsetof (STRUCT, MEMBER)))
+/* A null pointer constant suitable for use in a varargs parameter list.
+
+ This is useful because a literal 0 may not have the same width as a null
+ pointer. NULL by itself is also insufficient because in C it may expand to
+ simply 0. */
+#define NULL_SENTINEL ((void *) NULL)
+
#endif /* libpspp/cast.h */