+extern boolean interrupt_maybe_gc_int(int, siginfo_t *, void *);
+extern boolean maybe_defer_handler(void *handler, struct interrupt_data *data,
+ int signal, siginfo_t *info,
+ os_context_t *context);
+#if defined LISP_FEATURE_GENCGC
+/* assembly language stub that executes trap_PendingInterrupt */
+extern void do_pending_interrupt(void);
+#endif
+
+#ifdef LISP_FEATURE_SB_THREAD
+extern void interrupt_thread_handler(int, siginfo_t*, void*);
+extern void sig_stop_for_gc_handler(int, siginfo_t*, void*);
+#endif
+extern void undoably_install_low_level_interrupt_handler (int signal,
+ void
+ handler(int,
+ siginfo_t*,
+ void*));