elisp function for generating header guards for C/C++ headers.

c-include-guard.el

(defun c-include-guard ()
  "Insert C header include guards."
  (interactive)
  (let (original-point macro-name)
    (set 'original-point (point))
    (set 'macro-name
         (upcase
          (replace-regexp-in-string
           "\\."
           "_"
           (file-name-nondirectory
            buffer-file-name))))
    (goto-char (point-min))
    (insert
     (concat "#ifndef " macro-name "\n#define " macro-name "\n\n"))
    (set 'original-point (- (+ (point) original-point) 1))
    (goto-char (point-max))
    (insert "\n#endif\n")
    (goto-char original-point)))