`ac-etags.el' is etags/ctags completion source for auto-complete. Sample configuration If you change `requires' auto-complete source attribute (custom-set-variables '(ac-etags-requires 1)) (eval-after-load "etags" '(progn (ac-etags-setup))) (defun my/c-mode-common-hook () (add-to-list 'ac-sources 'ac-source-etags)) (add-hook 'c-mode-common-hook 'my/c-mode-common-hook)