+extern void block_deferrable_signals(void);
+extern void block_blockable_signals(void);
+extern void unblock_deferrable_signals(void);
+extern void unblock_gc_signals(void);
+extern void unblock_signals_in_context_and_maybe_warn(os_context_t *context);
+
+extern boolean deferrables_blocked_in_sigset_p(sigset_t *sigset);