I have something like below (from the answer) in my init file:

(add-hook 'LaTeX-mode-hook 'my-latex-hook)

(defun my-latex-hook ()
  (require 'tex-site)
  (define-key LaTeX-mode-map "-" (lambda () (interactive) (insert "_")))
  (define-key LaTeX-mode-map "_" (lambda () (interactive) (insert "-")))
  (define-key LaTeX-mode-map "6" (lambda () (interactive) (insert "^")))
  (define-key LaTeX-mode-map "^" (lambda () (interactive) (insert "6"))))

When I byte-compile the init file, there is a message: Warning: reference to free variable LaTeX-mode-map. The function works without problem in LaTeX-mode. Should one take this message serious? Is there a better way to write the above function in order to prevent this warning?

2 Answers 2


What you are doing is safe, because when your hook is executed LaTeX is already loaded and LaTeX-mode-map is defined. Byte compiler cannot know that because when it compiles your file LaTeX mode is not loaded and thus symbol LaTeX-mode-map considered free variable.

Apart from the technique you use, you can use eval-after-load:

(eval-after-load 'my-file
  ;; use functions from ‘my-file’ without fear

If you don't want to see the warning you can load file that contains LaTeX-mode-map only when you byte-compile your file:

  (require 'my-file))

This will not slow down Emacs on startup since my-file will be loaded only when your file is going to be compiled.

Many people will argue that you shouldn't compile your configuration files, though.


If you're going for a single file init, you can add this declare:

(defvar LaTeX-mode-map)

If you have multiple files, like I do, just require tex-site at top level, see ora-latex.el. What I do is load this always:

(add-hook 'LaTeX-mode-hook 'my-latex-hook)

But then my-latex-hook is an autoloaded function in ora-latex.el. So the whole file isn't loaded until necessary. The my-latex-hook function is usually empty, unless I need to enable some minor modes or set mode-local vars. The define-key statements are run only once instead of each time a new tex file is opened, which isn't a big deal but it's nice to have.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.