c++显示传递数组时为什么要指定其长度？

ackerman

#include <iostream>const int SIZE = 5;int sum_arr(int p[],int size);int main(){        int sum;        int arr[SIZE] = {1,2,3,4,5};        std::cout << "sizeof (arr)=" << sizeof(arr) << ", address=" << arr <<std::endl;        sum = sum_arr(arr,SIZE);        std::cout << "sum of arr=" << sum <<std::endl;        return 0;}int sum_arr(int p[], int size){        int sum = 0;        std::cout << "sizeof (p)=" << sizeof(p) << ", address=" << p <<std::endl;        for (int i =0; i < size; i++)                sum += p[i];        return sum;} 输出如下：
 

ackerman@ubuntu:~/桌面/c++test$ ./a.out sizeof (arr)=20, address=0xbf9afa68sizeof (p)=4, address=0xbf9afa68sum of arr = 15