arrays-and-pointers.c

#include <stdio.h>

int main()
{
    int arr[5] = {1, 2, 3, 4, 5};

    arr;     // int[5];          array
    &arr;    // int (*)[5];      pointer to an array   (note that (int *)[5] would be an array of pointers)
    &arr[0]; // int *;           pointer to an int
    *arr;    // int;             arr decays it to its initial pointer (&arr[0]) then dereferencing gives arr[0]

    // when the array (arr) by itself is used anywhere (eg. arithmetic operation, passing into a function)
    // it 'decays' into a pointer
    // int[5] -> int *
    // thus losing size information.

    // It does not decay into a pointer, when:
    // - it is used with & (&arr)
    // - it is used with sizeof()

    printf("%lu\n", sizeof(arr));  // 20 (5 * 4), when used with sizeof it doesnt decay and still means the entire array
    printf("%lu\n", sizeof(&arr)); // 8, pointer's size
    printf("%lu\n", sizeof(*arr)); // 4, int's size

    // https://www.oreilly.com/library/view/understanding-and-using/9781449344535/ch04.html#PointersAndMultiDimensionArraysSection

    // Incrementing behaviour:
    arr + 1;  // int *        incremented by 1 * sizeof(int)      &arr[1];
    &arr + 1; // int (*)[5]   incremented by 1 * sizeof(int[5])

    // in general, (type *) variable on incrementing, has an offset of sizeof(type).

    return 0;
}