A random scrapbook of problems and solutions for things I've stubbed my toe on with GNU Emacs.
Starting up Emacs24 one day, and the C++ setup didn't get run. I enabled
(setq debug-on-error t)
in my .emacs.d/init.el and saw:
c-font-lock-fontify-region: Symbol's function definition is void: nil
Running with emacs -Q to disable startup scripts saw everything working, so it's something in init.el. A bit of guesswork/triangulation later, and it's this line:
'(font-lock-mode t t (font-lock))
in (custom-set-variables.
I suspect this is an old line turning on global font lock. Now replaced by global-font-lock-mode which appears to be on by default anyway. I removed the line and all is now well.