Timer配置出现问题的解决办法？

.driverlibtimer.h(247): error:  #20: identifier "bool" is undefined
.driverlibtimer.h(249): error:  #20: identifier "bool" is undefined
.driverlibtimer.h(253): error:  #20: identifier "bool" is undefined
.driverlibtimer.h(255): error:  #20: identifier "bool" is undefined
.driverlibtimer.h(281): error:  #20: identifier "bool" is undefined
调用timer.h头文件时为什么会出现这个错误，编译环境是MDK4.72,开发板是TM4C1294XL