摆脱“对自由变量的引用"字节编译警告 [英] Get rid of "reference to free variable" byte-compilation warnings

问题描述

我正在编写一个 emacs 主模式，它使用缓冲区局部变量来存储一些状态:

I'm writing an emacs major mode, which uses buffer-local variables to store some state:

(defun foo-mode ()
  "My nice major mode"
  (interactive)
  (kill-all-local-variables)
  (setq mode-name "foo")
  (setq major-mode 'foo-mode)
  (set (make-local-variable 'foo-state) "bar"))

(defun foo-change-state ()
  (setq foo-state "baz"))

这很好用，并且具有在任何不使用我的主要模式的缓冲区中的属性，foo-state 变量不受约束(在我看来这是一件好事，因为它避免了混乱符号表).

This works very well and has the property that in any buffer not using my major mode, the foo-state variable is not bound (which is a good thing in my opinion, since it avoids cluttering the symbols table).

然而，对这样一段代码进行字节编译会产生以下警告:

However, byte-compiling such a piece of code produces the following warning:

Warning: assignment to free variable `foo-state'

使用 defvar 消除了警告，但有一个副作用，即 foo-state 现在到处都是绑定的，这在我看来是不可取的.

Using defvar gets rid of the warning, but has the side-effect that foo-state is now bound everywhere, which is undesirable in my opinion.

有没有办法消除警告，同时仍然没有在每个缓冲区中绑定特定于模式的变量?或者我认为这些变量不应该被全局声明是我错了?

Is there a way to get rid of the warnings while still not binding the mode-specific variables in every buffer? Or am I mistaken when I think these variables should not be declared globally?

推荐答案

做你想做的事情的官方方法是 (defvar foo-state).注意没有第二个参数.另请注意，此类声明仅适用于找到它的文件(或找到它的范围，如果它在函数内使用).

The official way to do what you want is (defvar foo-state). Note the absence of a second argument. Note also that such a declaration only applies to the file where it is found (or to the scope in which it is found, if it's used inside a function).

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