* lisp/bookmark.el (bookmark-write-file): Bind `print-circle' to `t'

  here to allow circular custom bookmark types.  (Bug#12503)

2 files changed, 8 insertions, 1 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 7ac0ec72990..0e515c2a7b4 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -2,6 +2,8 @@
 
         * bookmark.el (bookmark-version-control): Give tags in the
         :type choices (Bug#12309), and improve doc string.
+        (bookmark-write-file): Bind `print-circle' to `t' to allow
+        circular custom bookmark types.  (Bug#12503)
 
 2012-10-01  Paul Eggert  <eggert@cs.ucla.edu>
 
diff --git a/lisp/bookmark.el b/lisp/bookmark.el
index 3259d6283f9..ebb3aac3319 100644
--- a/lisp/bookmark.el
+++ b/lisp/bookmark.el
@@ -1359,7 +1359,12 @@ for a file, defaulting to the file defined by variable
     (goto-char (point-min))
     (delete-region (point-min) (point-max))
     (let ((print-length nil)
-          (print-level nil))
+          (print-level nil)
+          ;; See bug #12503 for why we bind `print-circle'.  Users
+          ;; can define their own bookmark types, which can result in
+          ;; arbitrary Lisp objects being stored in bookmark records,
+          ;; and some users create objects containing circularities.
+          (print-circle t))
       (bookmark-insert-file-format-version-stamp)
       (insert "(")
       ;; Rather than a single call to `pp' we make one per bookmark.