Re: Multiple major modes

[Johan Bockgård]

Richard Stallman <address@hidden> writes:

> This suggests an idea to me.  Maybe Emacs could highlight the function
> definition somehow, to indicate that the function has been advised.

FWIW, there is already an entry in TODO

    ** Emacs Lisp mode could put an overlay on the defun for every
      function that has advice.  The overlay could have `after-text'
      like " [Function has advice]".  It might look like (defun foo
      [Function has advice] (x y) The overlay could also be a button
      that you could use to view the advice.

> That might solve the problem that makes advising bad for debugging.

Here's an example where advice can be really confusing:

;; See ad-default-compilation-action
(require 'bytecomp)

(defun foo (x y)
  (+ x y))

(defadvice foo (before bar activate)
  (car x))

(foo 1 2)
  =>

Debugger entered--Lisp error: (wrong-type-argument listp 1)
  foo(1 2)
  eval((foo 1 2))
  eval-last-sexp-1(nil)
  eval-last-sexp(nil)
  call-interactively(eval-last-sexp)


(If the advice is not compiled "car(1)" is present in the backtrace.)

-- 
Johan Bockgård