• 在使用 Keil MDK 开发项目，编译时，报如下错误

*** Using Compiler 'V5.06 update 1 (build 61)', folder: 'D:\Keil_v5\ARM\ARMCC\Bin'
Build target 'led_breathe'
compiling main.c...
user\main.c(11): error:  #268: declaration may not appear after executable statement in block
  	uint8_t dutyCycle = 0;
user\main.c(12): error:  #268: declaration may not appear after executable statement in block
  	uint8_t dir = 0;
user\main.c: 0 warnings, 2 errors
".\Objects\led_breathe.axf" - 2 Error(s), 0 Warning(s).
Target not created.
Build Time Elapsed:  00:00:00

# 关键错误

user\main.c(11): error:  #268: declaration may not appear after executable statement in block
  	uint8_t dutyCycle = 0;
user\main.c(12): error:  #268: declaration may not appear after executable statement in block
  	uint8_t dir = 0;

问题原因

• 这个错误是变量声明放在了可执行代码之后（见下例），C89 标准不允许混合声明和代码

int main()
{
	TIM3_init();

	TIM3_start();

	uint8_t dutyCycle = 0;
	uint8_t dir = 0;
	
	...
}

处理策略

• 在 Keil MDK 中启用 C99