STM32中基于库V3.5的头文件中，去掉了对bool类型变量的定义，而将它放在了文件stdbool.h中(d:\Keil_v5\ARM\ARMCC\include\stdbool.h)
stdbool文件内容如下:
/* stdbool.h: ISO/IEC 9899:1999 (C99), section 7.16 */
/* Copyright (C) ARM Ltd., 2002
* All rights reserved
* RCS $Revision: 177844 $
* Checkin $Date: 2012-11-21 11:51:12 +0000 (Wed, 21 Nov 2012) $
* Revising $Author: drodgman $
*/
#ifndef __bool_true_false_are_defined
#define __bool_true_false_are_defined 1
#define __ARMCLIB_VERSION 5060001
#ifndef __cplusplus /* In C++, 'bool', 'true' and 'false' and keywords */
#define bool _Bool
#define true 1
#define false 0
#else
#ifdef __GNUC__
/* GNU C++ supports direct inclusion of stdbool.h to provide C99
compatibility by defining _Bool */
#define _Bool bool
#endif
#endif
#endif /* __bool_true_false_are_defined */
