数组名的sizeof 与数组作为函数参数的sizeof

#include <stdio.h>
using namespace std;
//字符串反转
int a[]={4,5,6};
int sum(int b[],int len)
{
int i,result=0;
for(i=0;i<len;i++)
{
result+=b[i];
}
printf("size of b:%d\n",sizeof(b));
return result;
}
int main(void)
{
printf("sizeof a:%d\n",sizeof(a));
sum(a,3);//

cout<<sum(a,3)<<endl;
}

sizeof  a: 12

sizeof b :4

15