C语言程序中的字节对齐方法详解

//2,4,8字节对齐方法测试

#include 

int main(void)

{

 int var = 0, i = 0, foo = 0,value = 0;

 for(; i < 5; i++)

 {

// var = i +( 1U & ~1U ); //这样写不会产生对齐效果 原因是()内的值为零

// foo = i +( 7U & ~7U );

// value = i + ( 3U & ~3U );

 var = i + 1U & ~1U ; //Round number of bytes to nearest 2-byte boundary 2字节对齐

 value = i + 3U & ~3U ; //Round number of bytes to nearest 4-byte boundary 4字节对齐

 foo = i + 7U & ~7U ; //Round number of bytes to nearest 8-byte boundary 8字节对齐

 printf("The num var is '%d'\n",var);

 printf("The num foo is '%d'\n",value);

 printf("The num foo is '%d'\n",foo);

 }

 printf("Hello World!\n");

 return 0;

}