+// Marking the <next> field of a node logically removes it from the list
+#if 0
+static inline markable_t MARK_NODE(node_t * x) { return TAG_VALUE((markable_t)x, TAG1); }
+static inline int HAS_MARK(markable_t x) { return (IS_TAGGED(x, TAG1) == TAG1); }
+static inline node_t * GET_NODE(markable_t x) { assert(!HAS_MARK(x)); return (node_t *)x; }
+static inline node_t * STRIP_MARK(markable_t x) { return ((node_t *)STRIP_TAG(x, TAG1)); }
+#else
+#define MARK_NODE(x) TAG_VALUE((markable_t)(x), TAG1)
+#define HAS_MARK(x) (IS_TAGGED((x), TAG1) == TAG1)
+#define GET_NODE(x) ((node_t *)(x))
+#define STRIP_MARK(x) ((node_t *)STRIP_TAG((x), TAG1))
+#endif
+