Emacs保存保存位置-保存文件时，杀死缓冲区:为什么我得到递归深度问题与钩子？

Question

我已经使用Emacs (目前为26.3)相当一段时间(数年)。我一直都有

(use-package saveplace
  :config
  (save-place-mode t))

在我的init.el中，Emacs使用save-place-mode (它附带香草Emacs作为saveplace.el)来记住文件中的最后一个位置。

我对saveplace的问题是，它一直将已访问的文件和位置保存到一个名为save-place-alist的列表中，并且只通过kill-emacs-hook中的一个钩子将该列表转储到默认位置~/.emacs.d/places。但这种情况经常发生，我忘记了，或者通常不会退出我的emacs守护进程。所以名单就会丢了。

我的方法是从save-place-alist-to-file中提取函数saveplace.el并将其添加到kill-buffer-hook中，因此现在，每当我杀死缓冲区save-place-alist时，都会将其保存到磁盘中。这就是我的保存位置配置现在看起来的样子：

(defun my-save-place-alist-to-file ()
(interactive)
(save-place-to-alist)
  (let ((file (expand-file-name save-place-file))
        (coding-system-for-write 'utf-8))
    (with-current-buffer (get-buffer-create " *Saved Places*")
      (delete-region (point-min) (point-max))
      (when save-place-forget-unreadable-files
        (save-place-forget-unreadable-files))
      (insert (format ";;; -*- coding: %s -*-\n"
                      (symbol-name coding-system-for-write)))
      (let ((print-length nil)
            (print-level nil))
        (pp save-place-alist (current-buffer)))
      (let ((version-control
             (cond
              ((null save-place-version-control) nil)
              ((eq 'never save-place-version-control) 'never)
              ((eq 'nospecial save-place-version-control) version-control)
              (t
               t))))
        (condition-case nil
            ;; Don't use write-file; we don't want this buffer to visit it.
            (write-region (point-min) (point-max) file)
          (file-error (message "Saving places: can't write %s" file)))
        (kill-buffer (current-buffer))))))

(use-package saveplace
  :config
  (save-place-mode t)
  ;; (remove-hook 'kill-buffer-hook 'save-place-to-alist)
  ;; (add-hook 'kill-buffer-hook 'my-save-place-alist-to-file))

一切我都很好，只要我不修改kill-buffer-hook，取消对最后一行的注释。函数my-save-place-alist-to-file在交互调用时正常工作。但当启动钩子时，几乎所有的东西都会刹车。首先，我不能再杀死缓冲区了。我得到了与递归深度相关的错误：

progn: Variable binding depth exceeds max-specpdl-size

调试器说：

Debugger entered--Lisp error: (error "Variable binding depth exceeds max-specpdl-size")
  generate-new-buffer(" *temp*")
  pp-to-string((("/home/.../test.txt" . 33)))
  pp((("/home/.../test.txt" . 33)) #<buffer  *Saved Places*>)
  (let ((print-length nil) (print-level nil)) (pp save-place-alist (current-buffer)))
  (save-current-buffer (set-buffer (get-buffer-create " *Saved Places*")) (delete-region (point-min) (point-max)) (if save-place-forget-unreadable-files (progn (save-place-forget-unreadable-files))) (insert (format ";;; -*- coding: %s -*-\n" (symbol-name coding-system-for-write))) (let ((print-length nil) (print-level nil)) (pp save-place-alist (current-buffer))) (let ((version-control (cond ((null save-place-version-control) nil) ((eq (quote never) save-place-version-control) (quote never)) ((eq (quote nospecial) save-place-version-control) version-control) (t t)))) (condition-case nil (write-region (point-min) (point-max) file) (file-error (message "Saving places: can't write %s" file))) (kill-buffer (current-buffer))))
  (let ((file (expand-file-name save-place-file)) (coding-system-for-write (quote utf-8))) (save-current-buffer (set-buffer (get-buffer-create " *Saved Places*")) (delete-region (point-min) (point-max)) (if save-place-forget-unreadable-files (progn (save-place-forget-unreadable-files))) (insert (format ";;; -*- coding: %s -*-\n" (symbol-name coding-system-for-write))) (let ((print-length nil) (print-level nil)) (pp save-place-alist (current-buffer))) (let ((version-control (cond ((null save-place-version-control) nil) ((eq ... save-place-version-control) (quote never)) ((eq ... save-place-version-control) version-control) (t t)))) (condition-case nil (write-region (point-min) (point-max) file) (file-error (message "Saving places: can't write %s" file))) (kill-buffer (current-buffer)))))
  my-save-place-alist-to-file()
  kill-buffer(#<buffer  *temp*-840370>)
  #f(compiled-function () #<bytecode 0x1c65c75>)()
  pp-to-string((("/home/.../test.txt" . 33)))
  pp((("/home/.../test.txt" . 33)) #<buffer  *Saved Places*>)
  (let ((print-length nil) (print-level nil)) (pp save-place-alist (current-buffer)))
  (save-current-buffer (set-buffer (get-buffer-create " *Saved Places*")) (delete-region (point-min) (point-max)) (if save-place-forget-unreadable-files (progn (save-place-forget-unreadable-files))) (insert (format ";;; -*- coding: %s -*-\n" (symbol-name coding-system-for-write))) (let ((print-length nil) (print-level nil)) (pp save-place-alist (current-buffer))) (let ((version-control (cond ((null save-place-version-control) nil) ((eq (quote never) save-place-version-control) (quote never)) ((eq (quote nospecial) save-place-version-control) version-control) (t t)))) (condition-case nil (write-region (point-min) (point-max) file) (file-error (message "Saving places: can't write %s" file))) (kill-buffer (current-buffer))))
  (let ((file (expand-file-name save-place-file)) (coding-system-for-write (quote utf-8))) (save-current-buffer (set-buffer (get-buffer-create " *Saved Places*")) (delete-region (point-min) (point-max)) (if save-place-forget-unreadable-files (progn (save-place-forget-unreadable-files))) (insert (format ";;; -*- coding: %s -*-\n" (symbol-name coding-system-for-write))) (let ((print-length nil) (print-level nil)) (pp save-place-alist (current-buffer))) (let ((version-control (cond ((null save-place-version-control) nil) ((eq ... save-place-version-control) (quote never)) ((eq ... save-place-version-control) version-control) (t t)))) (condition-case nil (write-region (point-min) (point-max) file) (file-error (message "Saving places: can't write %s" file))) (kill-buffer (current-buffer)))))
  my-save-place-alist-to-file()
  kill-buffer(#<buffer  *temp*-437350>)
  #f(compiled-function () #<bytecode 0x1c65c35>)()
  pp-to-string((("/home/.../test.txt" . 33)))
  pp((("/home/.../test.txt" . 33)) #<buffer  *Saved Places*>)
  (let ((print-length nil) (print-level nil)) (pp save-place-alist (current-buffer)))
  (save-current-buffer (set-buffer (get-buffer-create " *Saved Places*")) (delete-region (point-min) (point-max)) (if save-place-forget-unreadable-files (progn (save-place-forget-unreadable-files))) (insert (format ";;; -*- coding: %s -*-\n" (symbol-name coding-system-for-write))) (let ((print-length nil) (print-level nil)) (pp save-place-alist (current-buffer))) (let ((version-control (cond ((null save-place-version-control) nil) ((eq (quote never) save-place-version-control) (quote never)) ((eq (quote nospecial) save-place-version-control) version-control) (t t)))) (condition-case nil (write-region (point-min) (point-max) file) (file-error (message "Saving places: can't write %s" file))) (kill-buffer (current-buffer))))
  (let ((file (expand-file-name save-place-file)) (coding-system-for-write (quote utf-8))) (save-current-buffer (set-buffer (get-buffer-create " *Saved Places*")) (delete-region (point-min) (point-max)) (if save-place-forget-unreadable-files (progn (save-place-forget-unreadable-files))) (insert (format ";;; -*- coding: %s -*-\n" (symbol-name coding-system-for-write))) (let ((print-length nil) (print-level nil)) (pp save-place-alist (current-buffer))) (let ((version-control (cond ((null save-place-version-control) nil) ((eq ... save-place-version-control) (quote never)) ((eq ... save-place-version-control) version-control) (t t)))) (condition-case nil (write-region (point-min) (point-max) file) (file-error (message "Saving places: can't write %s" file))) (kill-buffer (current-buffer)))))
  my-save-place-alist-to-file()
...

我已经试过很多方法来解决这个问题了。我的第一个猜测是，(kill-buffer (current-buffer))的最后调用将导致无限递归。但是移除它没有帮助。

总之，我的问题是：

*无限递归发生的原因和地点？

Answer 1

我尝试了@choroba通过添加一个

(let 'kill-buffer-hook nil
...
) 

围绕(save-place-to-alist)之后的整个部分，确实消除了无限递归问题！但随后又出现了另一个问题:每当我切换缓冲区时，这个钩子就会被叫来，而这个键在更多的情况下都会弹出。每次写信给~/.emacs.d/places。所以这不是我想要的。

同时，我找到了一个方便的解决方案:不是将函数添加到kill-buffer-hook，而是将函数添加到after-save-hook。对我来说就足够了:)

我的最后一个save-place-setup (对我来说很好)现在看起来如下：

(defun my-save-place-alist-to-file ()
  (interactive)
  (save-place-to-alist)
  (let ((file (expand-file-name save-place-file))
        (coding-system-for-write 'utf-8))
    (with-current-buffer (get-buffer-create " *Saved Places*")
      (delete-region (point-min) (point-max))
      (when save-place-forget-unreadable-files
        (save-place-forget-unreadable-files))
      (insert (format ";;; -*- coding: %s -*-\n"
                      (symbol-name coding-system-for-write)))
      (let ((print-length nil)
            (print-level nil))
        (pp save-place-alist (current-buffer)))
      (let ((version-control
             (cond
              ((null save-place-version-control) nil)
              ((eq 'never save-place-version-control) 'never)
              ((eq 'nospecial save-place-version-control) version-control)
              (t
               t))))
        (condition-case nil
            ;; Don't use write-file; we don't want this buffer to visit it.
            (write-region (point-min) (point-max) file nil) ; 4th arg nil means: do not append!
          (file-error (message "Saving places: can't write %s" file))
          (kill-buffer (current-buffer)))))))

(use-package saveplace
  :config
  (save-place-mode t)
  (add-hook 'after-save-hook 'my-save-place-alist-to-file)) ; after-save-hook seems to be the best place for this