(defun truncate-command-history-for-gc ()
- (let ((tail (nthcdr 30 command-history)))
- (if tail (setcdr tail nil)))
- (let ((tail (nthcdr 30 values)))
- (if tail (setcdr tail nil)))
- )
+ ;; We should try to avoid accessing any bindings to speak of in this
+ ;; function; as this hook is called asynchronously, the search for
+ ;; those bindings might search local bindings from essentially
+ ;; arbitrary functions. We force the body of the function to run at
+ ;; command-loop level, where the danger of local bindings is much
+ ;; reduced; the code can still do its job because the command history
+ ;; and values list will not grow before then anyway.
+ ;;
+ ;; Nothing is done in batch mode, both because it is a waste of time
+ ;; (there is no command loop!) and because this any GCs during dumping
+ ;; will invoke this code, and if it were to enqueue an eval event,
+ ;; the portable dumper would try to dump it and fail.
+ (if (not (noninteractive))
+ (enqueue-eval-event
+ #'(lambda (arg)
+ (let ((tail (nthcdr 30 command-history)))
+ (if tail (setcdr tail nil)))
+ (let ((tail (nthcdr 30 values)))
+ (if tail (setcdr tail nil))))
+ nil)))
(add-hook 'pre-gc-hook 'truncate-command-history-for-gc)