Generic Stack implementation in C-style C++

I implemented generic stack in C. Seems to work fine. It doesn't work for strings, though.

It was compiled using Visual C++.

Implementation:

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

struct node{
    void* value;

    node* next;
};

struct stack{
    node* first;
    int elemSize;
    int length;
};

stack* StackNew(int elemSize)
{
    stack* s = (stack*)malloc(sizeof(stack));
    s->elemSize = elemSize;
    s->length = 0;
    return s;
}

void Push(stack* s, void* value)
{
    node* oldFirst = s->first;
    s->first = (node*)malloc(sizeof(node));
    s->first->value = malloc(s->elemSize);
    memcpy(s->first->value, value, s->elemSize);
    s->first->next = oldFirst;
    s->length++;
}

void* Pop(stack* s)
{
    void* value = malloc(s->elemSize);
    memcpy(value, s->first->value, s->elemSize);
    node* oldFirst = s->first;
    s->first = s->first->next;
    free(oldFirst);
    s->length--;
    return value;
}

void Destory(stack* s)
{
    while (s->length > 0) Pop(s);
    free(s);
}

Test:

struct point{
    int x, y;
};

int main()
{
    stack* s = StackNew(sizeof(point));
    for (int i = 0; i < 100; i++){
        point pt;
        pt.x = i;
        pt.y = i * i;
        Push(s, &pt);
    }

    while (s->length > 0) {
        point pt = *(point*)Pop(s);
        printf("(%d,%d)\n", pt.x, pt.y);
    }
    Destory(s);
    return 0;
}

Output:

(99,9801)
(98,9604)
(97,9409)
(96,9216)
(95,9025)
(94,8836)
(93,8649)
(92,8464)
(91,8281)
(90,8100)
(89,7921)
(88,7744)
(87,7569)
(86,7396)
...

as expected.

Please tell me what I did wrong and how I can improve things.