keil在配置STemWin时出现错误

Error: L6218E: Undefined symbol GUI_X_GetTaskId (referred from gui_task.o).
Error: L6218E: Undefined symbol GUI_X_InitOS (referred from gui_task.o).
Error: L6218E: Undefined symbol GUI_X_Lock (referred from gui_task.o).
Error: L6218E: Undefined symbol GUI_X_Unlock (referred from gui_task.o).
这四个函数好像只有函数声明没用函数实体，请问怎么解决呢

http://blog.sina.com.cn/s/blog_98ee3a930102va54.html