+#if 0
+ /* at one time we had the bright idea of using mprotect() to
+ * hide the semispace that we're not using at the moment, so
+ * we'd see immediately if anyone had a pointer to it.
+ * Unfortunately, if we gc during a call to an assembler
+ * routine with a "raw" return style, at least on PPC we are
+ * expected to return into oldspace because we can't easily
+ * update the link register - it's not tagged, and we can't do
+ * it as an offset of reg_CODE because the calling routine
+ * might be nowhere near our code vector. We hope that we
+ * don't run very far in oldspace before it catapults us into
+ * newspace by either calling something else or returning
+ */
+
+ /* write-enable */
+ os_protect(new_space,DYNAMIC_SPACE_SIZE,OS_VM_PROT_ALL);
+#endif