Arrays as function parameters in C

array-params.c

#include <stdio.h>
#include <stdlib.h>

/* the array name by default is a pointer to its first element,
 * similar to test2
 */
void test1(int len, int x[])
{
    int i;
    for (i = 0; i < len; i++)
    {
        printf("x[%d] = %d; ", i, x[i]);
    }

    printf("\n");
}

/* pass the pointer to the first element */
void test2(int len, int* x)
{
    for (int i = 0; i < len; i++)
    {
        printf("x[%d] = %d; ", i, *(x + i));
    }

    printf("\n");
}

/* array pointer: the array name by default points to the first element;
 * &array returns the pointer to the entire array
 */
void test3(int len, int(*x)[len])
{
    for (int i = 0; i < len; i++)
    {
        printf("x[%d] = %d; ", i, (*x)[i]);
    }

    printf("\n");
}

/* multidimensional array: the array name by default is a pointer to its
 * first elements, which is also int(*)[]
 */
void test4(int r, int c, int y[][c])
{
    for (int a = 0; a < r; a++)
    {
        for (int b = 0; b < c; b++)
        {
            printf("y[%d][%d] = %d; ", a, b, y[a][b]);
        }
    }

    printf("\n");
}

/* multidimensional array: pass the pointer to the first element */
void test5(int r, int c, int (*y)[c])
{
    for (int a = 0; a < r; a++)
    {
        for (int b = 0; b < c; b++)
        {
            printf("y[%d][%d] = %d; ", a, b, (*y)[b]);
        }

        y++;
    }

    printf("\n");
}

/* multidimensional array */
void test6(int r, int c, int (*y)[][c])
{
    for (int a = 0; a < r; a++)
    {
        for (int b = 0; b < c; b++)
        {
            printf("y[%d][%d] = %d; ", a, b, (*y)[a][b]);
        }
    }

    printf("\n");
}

/* pointer array whose elements are pointers, equivalent to test8 */
void test7(int count, char** s)
{
    for (int i = 0; i < count; i++)
    {
        printf("%s; ", *(s++));
    }

    printf("\n");
}

void test8(int count, char* s[count])
{
    for (int i = 0; i < count; i++)
    {
        printf("%s; ", s[i]);
    }

    printf("\n");
}

/* pointer array ending with NULL */
void test9(int** x)
{
    int* p;
    while ((p = *x) != NULL)
    {
        printf("%d; ", *p);
        x++;
    }

    printf("\n");
}

int main(int argc, char* argv[])
{
    int x[] = { 1, 2, 3 };

    int len = sizeof(x) / sizeof(int);
    test1(len, x);
    test2(len, x);
    test3(len, &x);

    int y[][2] =
    {
        {10, 11},
        {20, 21},
        {30, 31}
    };

    int a = sizeof(y) / (sizeof(int) * 2);
    int b = 2;
    test4(a, b, y);
    test5(a, b, y);
    test6(a, b, &y);

    char* s[] = { "aaa", "bbb", "ccc" };
    test7(sizeof(s) / sizeof(char*), s);
    test8(sizeof(s) / sizeof(char*), s);

    int* xx[] = { &(int){111}, &(int){222}, &(int){333}, NULL };
    test9(xx);

    return EXIT_SUCCESS;
}