Ensure that we don't call print-unreadable-function from " prin1"

* src/print.c (PRINTPREPARE): Bind the current buffer so that we
can retrieve it later.
(print_vectorlike): Use it (bug#56773).
(syms_of_print): New internal `print--unreadable-callback-buffer'
variable.

2 files changed, 10 insertions, 1 deletions

diff --git a/test/lisp/subr-tests.el b/test/lisp/subr-tests.el
index 20f81d1ddc5..1d85631a4b8 100644
--- a/test/lisp/subr-tests.el
+++ b/test/lisp/subr-tests.el
@@ -1122,5 +1122,15 @@ final or penultimate step during initialization."))
       (should (equal (butlast l n)
                      (subr-tests--butlast-ref l n))))))
 
+(ert-deftest test-print-unreadable-function-buffer ()
+  (with-temp-buffer
+    (let ((current (current-buffer))
+          callback-buffer)
+      (let ((print-unreadable-function
+             (lambda (_object _escape)
+               (setq callback-buffer (current-buffer)))))
+        (prin1-to-string (make-marker)))
+      (should (eq current callback-buffer)))))
+
 (provide 'subr-tests)
 ;;; subr-tests.el ends here
diff --git a/test/src/print-tests.el b/test/src/print-tests.el
index f818b4d4715..91187d9f45c 100644
--- a/test/src/print-tests.el
+++ b/test/src/print-tests.el
@@ -529,6 +529,5 @@ otherwise, use a different charset."
                   (should (equal (% (- (length numbers) loopback-index) loop)
                                  0)))))))))))
 
-
 (provide 'print-tests)
 ;;; print-tests.el ends here