Push mark when using ido-imenu

gistfile1.el

;; Push mark when using ido-imenu

(defvar push-mark-before-goto-char nil)

(defadvice goto-char (before push-mark-first activate)
  (when push-mark-before-goto-char
    (push-mark)))

(defun ido-imenu-push-mark ()
  (interactive)
  (let ((push-mark-before-goto-char t))
    (ido-imenu)))

It turns out that the ido-imenu command in use in the screencast is not in Emacs 24. I have no idea where it came from either, but here's the code for that aswell: https://gist.github.com/2360578

Why not just advice ido-imenu?

  (defadvice ido-imenu (before push-mark activate)
    (push-mark))

Good question -- isn't advicing goto-char a bit risky performance-wise since it's called by so much other code, even non-interactive code?