【C语言】数组名传递给函数，数组的sizeof变为4的原因

#include<iostream>
using namespace std;

void Swap_arr(char* charArr){
    int len = sizeof(charArr);
    cout << "len =" << len << endl;    //输出len =4
}

int main(){
    char charArr[] = "abcdefgh";
    Swap_arr(charArr);
    return 1;
}

#include<iostream>
using namespace std;

void test_arr(char* charArr, int len){
    cout << "len =" << len << endl;    //输出：len =8
}

int main(){
    char charArr[] = "abcdefgh";
    int len = sizeof(charArr) / sizeof(charArr[0]) - 1;
    test_arr(charArr,len);
    return 1;
}