.\driverlib\timer.h(247): error: #20: identifier "bool" is undefined
.\driverlib\timer.h(249): error: #20: identifier "bool" is undefined
.\driverlib\timer.h(253): error: #20: identifier "bool" is undefined
.\driverlib\timer.h(255): error: #20: identifier "bool" is undefined
.\driverlib\timer.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
