+;;; This is to support signal handlers that want to return to the
+;;; interrupted context without leaving anything extra on the stack. A
+;;; simple
+;;;
+;;; (without-interrupts
+;;; (unblock-deferrable-signals)
+;;; (allow-with-interrupts ...))
+;;;
+;;; would not cut it, as upon leaving WITHOUT-INTERRUPTS the pending
+;;; handlers is run with stuff from the function in which this is
+;;; still on the stack.
+(defvar *unblock-deferrables-on-enabling-interrupts-p* nil)