From 8751e5b75fb216e7a4be2a2866dce50652f1b801 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Sun, 22 Nov 2020 15:21:44 -0700
Subject: [PATCH] Chez Scheme: fix `$describe-fasl-from-port` with cycles

---
 racket/src/ChezScheme/s/strip.ss | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/racket/src/ChezScheme/s/strip.ss b/racket/src/ChezScheme/s/strip.ss
index d03a5f234b..2d5c392601 100644
--- a/racket/src/ChezScheme/s/strip.ss
+++ b/racket/src/ChezScheme/s/strip.ss
@@ -730,9 +730,12 @@
               [else
                (let ([p (eq-hashtable-cell ht x #f)])
                  (or (cdr p)
-                     (let ([v (describe-next x)])
-                       (set-cdr! p v)
-                       v)))]))
+                     (let ([self (vector 'CYCLE #f)])
+                       (set-cdr! p self)
+                       (let ([v (describe-next x)])
+                         (vector-set! self 1 v)
+                         (set-cdr! p v)
+                         v))))]))
           (define (describe-next x)
             (fasl-case x
               [entry (situation fasl)