【c语言】位段大小的计算以及宏的应用

// 位段大小的计算以及宏的应用

#include <stdio.h>
#include <malloc.h>
#define MAX_SIZE A+B

struct _Record_Struct
{
	unsigned char Env_Alarm_ID : 4;
	unsigned char Paral : 2;
	unsigned char state;
	unsigned char avail : 1;
}*Env_Alarm_Record;

int main()
{
	int A = 2;
	int B = 3;
	struct _Record_Struct *pointer = (struct _Record_Struct*)malloc
									 (sizeof(struct _Record_Struct) * MAX_SIZE);
	printf("%d\n", sizeof(struct _Record_Struct));//结构体大小是3
	free(pointer);
	return 0;
}
// 3*2+3=9开辟出来9个字节的空间

<img src="http://img.blog.csdn.net/20150508174521965?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvemhhb3lhcWlhbjU1Mg==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center" alt="" />