fix custodian-managed-list: omit custodian-boxes

pkgs/racket-test-core/tests/racket/subprocess.rktl

@@ -432,6 +432,15 @@
   (test #f pair? (member sp (custodian-managed-list c2 c)))
   (custodian-shutdown-all c))
 
+;; Check custodian-boxes are omitted by custodian-managed-list:
+(let* ([c (make-custodian)]
+       [c2 (make-custodian c)])
+  (define cb (make-custodian-box c2 'value))
+  (test '() custodian-managed-list c2 c)
+  (test 'value custodian-box-value cb)
+  (custodian-shutdown-all c2)
+  (test #f custodian-box-value cb))
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;; process groups
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

racket/src/cs/schemified/thread.scm

@@ -5732,7 +5732,27 @@
             c_0
             "second custodian"
             super-c_0))
-         (hash-keys (custodian-children c_0)))))))
+         (reverse$1
+          (let ((ht_0 (custodian-children c_0)))
+            (begin
+              (letrec*
+               ((for-loop_0
+                 (|#%name|
+                  for-loop
+                  (lambda (fold-var_0 i_0)
+                    (begin
+                      (if i_0
+                        (let ((v_0 (hash-iterate-key ht_0 i_0)))
+                          (let ((fold-var_1
+                                 (if (not (1/custodian-box? v_0))
+                                   (let ((fold-var_1 (cons v_0 fold-var_0)))
+                                     (values fold-var_1))
+                                   fold-var_0)))
+                            (for-loop_0
+                             fold-var_1
+                             (hash-iterate-next ht_0 i_0))))
+                        fold-var_0))))))
+               (for-loop_0 null (hash-iterate-first ht_0)))))))))))
 (define 1/custodian-memory-accounting-available?
   (|#%name| custodian-memory-accounting-available? (lambda () (begin #t))))
 (define 1/custodian-require-memory

racket/src/thread/custodian.rkt

@@ -381,7 +381,9 @@
     (raise-arguments-error who "the second custodian does not manage the first custodian"
                            "first custodian" c
                            "second custodian" super-c))
-  (hash-keys (custodian-children c)))
+  (for/list ([v (in-hash-keys (custodian-children c))]
+             #:when (not (custodian-box? v)))
+    v))
 
 (define (custodian-memory-accounting-available?)
   #t)