iterating in a array in C

Question

Hey I have something of this type

eph_t *a;

The type is eph_t as you can see. Its an array in C but I do not know the size of the array nor

Answer 1

You can reserve the first element of array to store the size

#include 
#include 
#include 

typedef struct {
    int x, y;
    double z;
} eph_t;

static void temp(eph_t *a)
{
    size_t n;

    memcpy(&n, a - 1, sizeof(size_t)); /* get size (stored in a - 1) */
    printf("Count = %zu\n", n);
}

int main(void)
{
    const size_t n = 5;
    eph_t a[n + 1]; /* allocate space for 1 more element */

    memcpy(&a[0], &n, sizeof(size_t)); /* now the first element contains n */
    temp(a + 1); /* skip first element */
    return 0;
}