diff options
Diffstat (limited to 'lisp')
| -rw-r--r-- | lisp/simple.el | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/lisp/simple.el b/lisp/simple.el index b3ff6344aa0..d4e34049c2a 100644 --- a/lisp/simple.el +++ b/lisp/simple.el @@ -554,7 +554,8 @@ addition, the encoding is fully shown." :version "21.1") (defcustom eval-expression-debug-on-error t - "*Value to use for `debug-on-error' when evaluating in `eval-expression'." + "*Non-nil means set `debug-on-error' when evaluating in `eval-expression'. +If nil, don't change the value of `debug-on-error'." :group 'lisp :type 'boolean :version "21.1") @@ -570,8 +571,20 @@ Value is also consed on to front of the variable `values'." nil read-expression-map t 'read-expression-history) current-prefix-arg)) - (let ((debug-on-error eval-expression-debug-on-error)) - (setq values (cons (eval eval-expression-arg) values))) + + (if (null eval-expression-debug-on-error) + (setq values (cons (eval eval-expression-arg) values)) + (let ((old-value (make-symbol "t")) new-value) + ;; Bind debug-on-error to something unique so that we can + ;; detect when evaled code changes it. + (let ((debug-on-error old-value)) + (setq values (cons (eval eval-expression-arg) values)) + (setq new-value debug-on-error)) + ;; If evaled code has changed the value of debug-on-error, + ;; propagate that change to the global binding. + (unless (eq old-value new-value) + (setq debug-on-error new-value)))) + (let ((print-length eval-expression-print-length) (print-level eval-expression-print-level)) (prin1 (car values) |