C关于指针的那点事

一,场景一

　 int arr[4] = {10, 20, 30, 40};

int (*pp)[4] = &arr;

int* p = (int*)(pp + 1);

NSLog(@"%d", *(p-2)); // 结果:30

二,场景二

int arr[4] = {10, 20, 30, 40};

int (*pp)[4] = &arr;

double* p = (double*)(pp + 1);

NSLog(@"%d", *(int*)(p - 2)); // 结果:10

int arr2[2][4] = {

{10, 20, 30, 40},

{11, 21, 31, 41}

};

int (*pp2)[4] = &arr2[1];

NSLog(@"%d", *(int*)pp2); // 结果:11

double* p2 = (double*)pp2;

NSLog(@"%d", *(int*)(p2 + 1)); // 结果:31

int* p2p = (int*)(arr2 + 1);

NSLog(@"%d", *(p2p - 3)); // 结果:20