Array assignment change first value

I want to create a binary heap with custom element, and the heap uses an array of struct Elem for store the data. But after the insertion, some data are lost, in this case the key value.

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

#define DEFAULT_CAPACITY    16
#define VALS 10

const int values[VALS] = {1, 2, 3, 4, 7, 8, 9, 10, 14, 16};

typedef int (*compareFunction)(const void *, const void *);

typedef struct Elem {
    void    *key;
    void    *value;
} Elem;

typedef struct Heap {
    unsigned int    size;
    unsigned int    capacity;
    Elem            **array;
    compareFunction compare;
} Heap;

Heap *hpCreate(compareFunction compare)
{
    Heap *heap;

    heap = (struct Heap *) malloc(sizeof(struct Heap));
    if (heap == NULL) return NULL;

    if ((heap->array = (struct Elem **) malloc(0)) == NULL) {
        free(heap);
        return NULL;
    }

    heap->size = 0;
    heap->capacity = DEFAULT_CAPACITY;
    heap->compare = compare;

    return heap;
}

Elem *hpCreateElem(void *key, void *value)
{
    Elem *el;

    el = (struct Elem *) malloc(sizeof(struct Elem));
    if (el == NULL) return NULL;

    el->key = key;
    el->value = value;

    return el;
}

void hpInsert(Heap *hp, void *key, void *value)
{
    Elem *el, *par;
    int pos;

    pos = hp->size++;
    el = hpCreateElem(key, value);
    par = hp->array[pos/2];

    while (pos > 1 && hp->compare(el->key, par->key) > 0) {
        hp->array[pos] = hp->array[pos/2];
        pos = pos/2;
        par = hp->array[pos/2];
    }

    hp->array[pos] = el;
}

int compare_int_ptr(const void *ptr1, const void *ptr2)
{
    int v1 = *((int *) ptr1); 
    int v2 = *((int *) ptr2);

    if (v1 == v2)
        return 0;
    else
        return (v1 > v2) ? 1 : -1;
}

int main()
{
    Heap *hp;
    Elem *el;
    int i;

    hp = hpCreate(compare_int_ptr);

    for (i = 0; i < VALS; i++) {
        hpInsert(hp, (void *) &values[i], (void *) &values[i]);
    }

    for (i = 0; i < VALS; i++) {
        el = hp->array[i];
        printf("%d\n", *((int *) el->key));
    }

    return 0;
}

the output produced is

4196700
16
14
9
10
4
3
8
17231984
7

instead of the binary heap array correctly ordered as 16 9 14 7 4 8 10 3 2 1