highlighting "TODO", "FIXME" and friends

When doing some programming with emacs, I like to highlight certain words that are not language keywords, but still have some special significance to me.

The emacs manual mentions this really useful trick:

(add-hook 'c-mode-common-hook
               (lambda ()
                (font-lock-add-keywords nil
                 '(("\\<\\(FIXME\\|TODO\\|BUG\\):" 1 font-lock-warning-face t)))))

This adds a hook function, a function that will be called when we open a C-file, so whenever there is a 'FIXME:', it gets a different color, so it stands out:

/* FIXME: check for foo */

Some notes:

• I am using c-mode-common-hook instead of the c-mode-hook (as the emacs manual does); this means that this will work for all C-mode languages - C/C++/Java/Objective-C/...
  
• I also added some extra keywords (TODO, BUG); you can of course add your own keywords there as well. It might help to use M-x re-builder (the Emacs regular expression builder), as Emacs regular expressions can be quite tricky to get right...