如何让Emacs cc-mode将Mako模板的%指令按C预处理指令处理？

Absolutely! You can tweak cc-mode's configuration to treat Mako's %-prefixed lines just like C preprocessor # lines. Here's how to do it step by step:

• Update the preprocessor symbol regex
  cc-mode uses c-preprocessor-symbol-regexp to identify which lines count as preprocessor directives. By default, it only matches lines starting with #. We'll extend it to include % as well:

  (setq c-preprocessor-symbol-regexp "^[ \t]*[%#]")
  

  This regex matches lines that start with optional whitespace followed by either % or #, so cc-mode will now recognize Mako directives as preprocessor-style lines.

• Adjust indentation behavior
  To ensure % lines use the same indentation rules as # preprocessor lines, set the cpp-macro offset in c-offsets-alist. For example, to keep them aligned with the current indentation level:

  (setq c-offsets-alist '((cpp-macro . 0)))
  

  If you prefer them indented like regular code, you can use values like + (indent one level) or - (outdent one level) instead of 0.

• Apply the configuration automatically
  To make these settings stick every time you open a C file (or Mako C template), add the code to your Emacs init file (~/.emacs or ~/.emacs.d/init.el) using a mode hook:

  (add-hook 'c-mode-hook
            (lambda ()
              (setq c-preprocessor-symbol-regexp "^[ \t]*[%#]")
              (setq c-offsets-alist '((cpp-macro . 0)))))
  

  If your Mako templates have a specific extension (like .mako.c), you can also auto-associate them with c-mode:

  (add-to-list 'auto-mode-alist '("\\.mako\\.c\\'" . c-mode))
  

After setting this up, restart Emacs or reload your config (M-x eval-buffer if you edited the init file directly). Your Mako % directives should now get the same syntax highlighting and automatic indentation as standard C preprocessor lines!

内容的提问来源于stack exchange，提问作者Jmb