A C/C++ pointer puzzle?

Suppose we have an integer variable whose size is 4 bytes and another pointer variable whose size is 8 bytes. So what will be the output below?

Example

#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;
}

To solve this problem, we can follow some important points:

• Integer size is 4 bytes (32 bits), pointer The size is 8 bytes. If we add 1 to the pointer, it will point to the next immediate type.

• The type of &a1 is int **, &a2 is int ***, and the type of &a3 is int ****. Here are all pointers. If we add 1, we will add 8 bytes.

• a [0] [0] [0] is an integer, &a [0] [0] [0] is int *, a [0] [0] is int * , the type of &a[0][0] is int(*)[6], and so on. So the type of &a is int(*)[4][5][6].

Output

480 8 8 8
8 8 8 480
4 8 8 120
4 24 120 480
1 4 24 120

The above is the detailed content of A C/C++ pointer puzzle?. For more information, please follow other related articles on the PHP Chinese website!