Use log-info instead of printf to permit silencing os2.rkt

os2.rkt

@@ -305,10 +305,12 @@
   (struct-copy vm state
 	       [processes (for/hash ([(pid p) (in-hash (vm-processes state))]
 				     #:when (or (process-alive? pid p)
-						(begin (printf "~a PID ~v (~a) garbage-collected~n"
+						(begin
+						  (log-info
+						   (format "~a PID ~v (~a) garbage-collected"
 							   (vm-name state)
 							   pid
-							       (process-name p))
+							   (process-name p)))
 						  #f)))
 			    (values pid p))]))
 
@@ -444,29 +446,28 @@
     (struct-copy vm (enqueue-actions state new-pid initial-actions)
 		 [processes (hash-set (vm-processes state) new-pid initial-process)]
 		 [next-process-id (+ new-pid 1)]))
-  (printf "~a PID ~v (~a) started~n" (vm-name state) new-pid new-name)
+  (log-info (format "~a PID ~v (~a) started" (vm-name state) new-pid new-name))
-  (flush-output (current-output-port))
   (run-trapk spawned-state spawning-pid k new-pid))
 
 (define (print-kill vm-name pid-to-kill process-name reason)
   (cond
-   [(eq? reason #f) (printf "~a PID ~v (~a) exited normally~n"
+   [(eq? reason #f) (log-info (format "~a PID ~v (~a) exited normally"
 				      vm-name
 				      pid-to-kill
-			    process-name)]
+				      process-name))]
-   [(exn? reason) ((error-display-handler)
+   [(exn? reason) (begin ((error-display-handler)
 			  (format "~a PID ~v (~a) exited with exception~n~a"
 				  vm-name
 				  pid-to-kill
 				  process-name
 				  (exn-message reason))
-		   reason)]
+			  reason)
-   [else (printf "~a PID ~v (~a) exited with reason: ~a~n"
+			 (flush-output (current-output-port)))]
+   [else (log-info (format "~a PID ~v (~a) exited with reason: ~a"
 			   vm-name
 			   pid-to-kill
 			   process-name
-		 reason)])
+			   reason))]))
-  (flush-output (current-output-port)))
 
 (define (do-kill pid-to-kill reason state)
   (cond