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