When starting emacs and loading cedet semantic on Mac, it will be got this error message:
error: Exuberent CTags not found.  Use M-x semantic-ectag-version RET

I checked the code in cedet/semantic/ctags/semantic-ectag-util.el, it's ran "ctags --version" to check ctags. But the output isn't what cedet semantic want.

This is right output by regular ctags:
Exuberant Ctags 5.8, Copyright (C) 1996-2009 Darren Hiebert
  Compiled: Nov 16 2009, 15:53:25
  Addresses: <dhiebert@users.sourceforge.net>, http://ctags.sourceforge.net
  Optional compiled features: +wildcards, +regex

The ctags execution file is wrapped in mac emacs(/Applications/MacPorts/Emacs.app/Contents/MacOS/bin):
ctags (GNU Emacs 23.1)
Copyright (C) 2009 Free Software Foundation, Inc.
This program is distributed under the terms in ETAGS.README

So, i installed another ctags by macports and override the ctags in emacs application contents. It works !!!!!!!