Emacs c-mode 自动加载失败
我想在加载 c 模式时加载名为“my-c-setup.el”的文件。所以，我使用“自动加载”功能。
使用我的 python 设置，它运行良好：
lang.el
(autoload 'python-mode "my-python-setup" "" t)
my-python-setup.el
(require 'python)
; ...
我正在尝试对 c 模式执行相同的操作，但我确实这样做不起作用：
lang.el
(autoload 'c-mode "my-c-setup" "" t)
my-c-setup.el
(setq c-basic-offset 4)
; ...
当我尝试以 c 模式打开文件（例如 test.c）时，我有以下内容错误 ：
File mode specification error: (error "Autoloading failed to define function c-mode")
I want to load my file named "my-c-setup.el" when the c-mode is loading. So, I'm using the function "autoload".
With my python setup, it works well :
lang.el
(autoload 'python-mode "my-python-setup" "" t)
my-python-setup.el
(require 'python)
; ...
I'm trying to do the same with the c-mode, but i does not work :
lang.el
(autoload 'c-mode "my-c-setup" "" t)
my-c-setup.el
(setq c-basic-offset 4)
; ...
When I try to open a file in c-mode (test.c for example), I have the following error :
File mode specification error: (error "Autoloading failed to define function c-mode")
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评论（3）
自动加载不是您要寻找的。它所做的只是在第一次需要时加载一些代码，这是扩展 Emacs 功能同时保持较短启动时间的便捷方法。
为了解决您的问题，我们必须考虑您真正想要做什么：您是否只是希望在某个时刻加载一些代码，或者您是否想要为
c- 中的所有缓冲区进行缓冲区本地自定义模式？如果您只想让 Emacs 在启动时加载代码，请将代码直接放入
.emacs文件中，或者使用load-file或require 而不是autoload：load-file只需获取一个文件名，加载该文件中的 lisp 代码并对其进行计算。因此，如果您的代码位于名为“/path/to/my-c-setup.el”的文件中，您可以将以下行放入 .emacs 中，代码将在每次启动时加载：也许您不这样做不想为您加载的每个文件提供绝对路径名。在这种情况下，您可以使用函数
load-library，它类似于load-file但尝试在存储在变量中的任何目录中查找给定的文件名load-path：优点是您只需执行一次
add-to-list部分，并且所有后续调用load-library> 将能够在该目录中找到代码。另一种方法是提供/要求机制：您可以通过在其中放置
(provide 'feature)调用来使 .el 文件“提供”某些功能，例如，然后放置相应的
(require 'feature)在您的 .emacs 文件中，您的代码也会被加载：但是，如果您希望仅在缓冲区上激活
c-mode时加载您的代码，实现的方法是通过 Emacs 的 Hook机制：大多数主要模式都提供可自定义的挂钩变量，您可以向其中添加在调用主要模式时将调用的函数。例如，c-mode 提供了
c-mode-hook。为了在缓冲区打开 c-mode 时调用您自己的自定义，请将它们放入一个函数中，例如my-c-mode-customizations并将以下行添加到您的 . emacs 文件：当然，您仍然需要
autoload让 Emacs 真正找到该函数的定义。Autoload is not what you're looking for. What it does is simply load some code the first time it is needed, which is a handy way to extend Emacs' functionality while still keeping the start-up time low.
To solve your problem, we gotta think about what you really want to do: do you simply want some of your code to be loaded at some point, or do you want buffer-local customizations for ever buffer that is in
c-mode?If you simply want Emacs to load your code at start-up, either put your code directly into your
.emacsfile or useload-fileorrequireinstead ofautoload:load-filesimply takes a file name, loads the lisp code in that file and evaluates it. So if your code is in a file named "/path/to/my-c-setup.el", you could put the following line in your .emacs, and the code will be loaded on every start-up:Perhaps you don't want to give the absolute path name for every file you load. In that case, you could use the function
load-libraryinstead which is similar toload-filebut tries to find the given filename in any of the directories stored in the variableload-path:The advantage is that you have to do the
add-to-listpart only once, and all subsequent calls toload-librarywill be able to find code in that directory.An alternative way is the provide/require mechanism: you can make your .el-file "provide" some feature by putting a
(provide 'feature)call in it, e.g.Then put an according
(require 'feature)in your .emacs file, and your code will be loaded as well:However, if you want your code only be loaded when
c-modeis activated on a buffer, the way to achieve that is through Emacs' Hook mechanism:Most major modes provide a customizable hook variable to which you can add functions that will be called whenever the major mode is invoked. For instance, c-mode provides
c-mode-hook. In order for your own customizations to be called whenever c-mode is turned on for a buffer, put them in a function, say,my-c-mode-customizationsand add the following line to your .emacs file:Of course, you still need
autoloadfor Emacs to actually find the definition of that function.Lisp 的 autoload 在文件加载时不会调用函数，而是告诉 lisp 该函数可用并且给定的文件提供了该函数。每当有人调用（尚未定义）函数时，就会加载该文件。
我认为
c-mode已经定义，因此无法重新注册。Lisp's autoload does not call a function when a file is loaded but tells lisp that the function is available and that the given file provides it. Whenever someone calls the (not yet defined) function, the file is loaded.
I think that
c-modeis already defined and thus fails to re-register.自动加载并不像您想象的那样。
http://www.gnu.org/software/emacs/elisp/ html_node/Autoload.html
您可能想要的是模式挂钩或加载后评估。
请参阅 eval-after-load 与模式挂钩了解两者之间的差异。
Autoload doesn't do what you think it does.
http://www.gnu.org/software/emacs/elisp/html_node/Autoload.html
What you probably want are mode-hooks or eval-after-load.
See eval-after-load vs. mode hook for the difference between the two.