-#define TAG (1ULL << 63)
-#define TAG_VALUE(v) ((uint64_t)(v) | TAG)
-#define IS_TAGGED(v) ((uint64_t)(v) & TAG)
-#define STRIP_TAG(v) ((uint64_t)(v) & ~TAG)
+#define TAG1 (1ULL << 63)
+#define TAG2 (1ULL << 62)
+#define TAG_VALUE(v, tag) ((uint64_t)(v) | tag)
+#define IS_TAGGED(v, tag) ((uint64_t)(v) & tag)
+#define STRIP_TAG(v, tag) ((uint64_t)(v) & ~tag)
+
+#define DOES_NOT_EXIST 0
+#define ERROR_INVALID_OPTION (-1)
+#define ERROR_INVALID_ARGUMENT (-2)
+#define ERROR_UNSUPPORTED_FEATURE (-3)