Fixed up the sighandler code some.

scsh/sighandlers.scm

@@ -95,18 +95,27 @@
 ;;; continuation), the ENABLED-INTERRUPTS register will be restored to its
 ;;; previous value.
 
+;;; This handler does nothing -- used when the handler is #f.
+(define (noop-sig-handler enabled-interrupts) #f)
+
 (define (set-signal-handler! sig handler)
-  (let ((nhandler (if (eq? handler #t)	; Get SIG's default handler.
+  (let ((nhandler (case handler
-		      (vector-ref default-handler-vec sig)
+		    ((#t) (vector-ref default-handler-vec sig))
-		      handler))
+		    ((#f) noop-sig-handler)
+		    (else handler)))
 	(int (signal->interrupt sig)))
     (with-enabled-interrupts 0
       (let ((ohandler (vector-ref interrupt-handlers int)))
 	(vector-set! interrupt-handlers int nhandler)
-	ohandler))))
+	(cond ((eq? ohandler (vector-ref default-handler-vec sig)) #t)
+	      ((eq? ohandler noop-sig-handler) #f)
+	      (else ohandler))))))
 
 (define (signal-handler sig)
-  (vector-ref interrupt-handlers (signal->interrupt sig)))
+  (let ((handler (vector-ref interrupt-handlers (signal->interrupt sig))))
+    (cond ((eq? handler (vector-ref default-handler-vec sig)) #t)
+	  ((eq? handler noop-sig-handler) #f)
+	  (else handler))))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;; Set the Unix signal handler. One doesn't usually use this; one usually