【基础】volatile unsigned int * a和 (volatile unsigned int *) a

错误：

    (volatile unsigned int *)pGPFCON = (volatile unsigned int *)0x56000050;
    (volatile unsigned int *)pGPFDAT = (volatile unsigned int *)0x56000054;

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• (int*)a将指针变量a强制类型转换为整型指针,一般不放在等号左边
• int*a，定义一个整型指针变量a
  

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正确：

volatile unsigned int *pGPFCON = (volatile unsigned int *)0x56000050;
volatile unsigned int *pGPFDAT = (volatile unsigned int *)0x56000054;