假设我们有一个整型变量,其大小为 4 字节,还有另一个指针变量,其大小为 8 字节。那么下面的输出会是什么?
示例
#include<iostream>
using namespace std;
main() {
int a[4][5][6];
int x = 0;
int* a1 = &x;
int** a2 = &a1;
int*** a3 = &a2;
cout << sizeof(a) << " " << sizeof(a1) << " " << sizeof(a2) << " " << sizeof(a3) << endl;
cout << (char*)(&a1 + 1) - (char*)&a1 << " ";
cout << (char*)(&a2 + 1) - (char*)&a2 << " ";
cout << (char*)(&a3 + 1) - (char*)&a3 << " ";
cout << (char*)(&a + 1) - (char*)&a << endl;
cout << (char*)(a1 + 1) - (char*)a1 << " ";
cout << (char*)(a2 + 1) - (char*)a2 << " ";
cout << (char*)(a3 + 1) - (char*)a3 << " ";
cout << (char*)(a + 1) - (char*)a << endl;
cout << (char*)(&a[0][0][0] + 1) - (char*)&a[0][0][0] << " ";
cout << (char*)(&a[0][0] + 1) - (char*)&a[0][0] << " ";
cout << (char*)(&a[0] + 1) - (char*)&a[0] << " ";
cout << (char*)(&a + 1) - (char*)&a << endl;
cout << (a[0][0][0] + 1) - a[0][0][0] << " ";
cout << (char*)(a[0][0] + 1) - (char*)a[0][0] << " ";
cout << (char*)(a[0] + 1) - (char*)a[0] << " ";
cout << (char*)(a + 1) - (char*)a;
}
解决这个问题,我们可以遵循以下一些重要点:
整数大小为4字节(32位),指针大小为8字节。如果我们将1与指针相加,它将指向下一个立即类型。
&a1的类型是int **,&a2是int ***,&a3的类型是int ****。这里都指向指针。如果我们加1,我们将添加8字节。
a [0] [0] [0]是一个整数,&a [0] [0] [0]是int *,a [0] [0]是int *,&a [0] [0]的类型是int(*)[6],依此类推。所以&a的类型是int(*)[4] [5] [6]。
输出
480 8 8 8
8 8 8 480
4 8 8 120
4 24 120 480
1 4 24 120