After fork/pipe, make the ports returned by the pipe the

current-in/output-ports. This corresponds to the intended semantics of
side-effecting the standard ports and tells the GC that the ports are
alive.

scsh/scsh.scm

@@ -36,12 +36,16 @@
       (let ((proc (forker #f no-new-command-level?)))
 	(cond (proc		; Parent
 	       (close w)
-	       (move->fdes r 0))
+	       (move->fdes r 0)
+               (set-current-input-port! r))
 	      (else		; Child
 	       (close r)
-	       (move->fdes w 1)
-	       (if maybe-thunk
-		   (call-terminally maybe-thunk))))
+               (move->fdes w 1)
+               (if maybe-thunk
+                   (with-current-output-port
+                    w
+                    (call-terminally maybe-thunk))
+                   (set-current-output-port! w))))
 	proc))))