emacs启动报错：Symbol's value as variable is void: c-mode-base-map

iMouse

我今天按照
http://emacser.com/cedet.htm
配置了.emacs
其中配置项：
(define-key c-mode-base-map [M-S-f12] 'semantic-analyze-proto-impl-toggle)

配置后，重新启动emacs，出现如下错误

An error has occurred while loading `/home/imouse/.emacs':

Symbol's value as variable is void: c-mode-base-map

To ensure normal operation, you should investigate and remove the
cause of the error in your initialization file.  Start Emacs with
the `--debug-init' option to view a complete error backtrace.

Loading semantic-el...done
For information about GNU Emacs and the GNU system, type C-h C-a.


请问是否缺少什么插件吗？

谢谢！