Generic ArrayList in C - c

Question

I have made a Java like ArrayList class in C for educational purposes however currently it is only good for integers. I want to make it Generic so it can take any type of data. How do I go about it. I read somewhere about creating a typedef void pointer. Any thoughts ?
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Here is My code
#ifndef ARRAYLIST_H
#define ARRAYLIST_H
typedef struct ArrayList ArrayList;
typedef int bool;
#define false 0
#define true 1
struct ArrayList {
int *con;
int numElements;
int conSize;
};
ArrayList *createArrayList();
void freeArrayList(ArrayList *);
void add(ArrayList *, int);
void printList(ArrayList *);
void resize(ArrayList *);
int remove(ArrayList *, int);
bool isEmpty(ArrayList*);
int getNumElements(ArrayList*);
int getConSize(ArrayList*);
#endif
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#include<stdio.h>
#include<stdlib.h>
#include"Consts.h"
#include "ArrayList.h"
#define CAPACITY 5
ArrayList *createArrayList() {
ArrayList *arrayList = malloc(sizeof(ArrayList));
arrayList->conSize = CAPACITY;
arrayList->numElements = 0;
arrayList->con = malloc(sizeof(int) * CAPACITY);
return arrayList;
}
void freeArrayList(ArrayList * arrayList) {
if (arrayList == NULL) {
return;
}else {
free(arrayList->con);
free(arrayList);
}
}
void add(ArrayList *arrayList, int input) {
//printf("Num elements in add method before adding %d \n", arrayList->numElements);
if (arrayList->numElements >= arrayList->conSize) {
resize(arrayList);
printf("resized\n");
}
int size = arrayList->numElements;
//add element to the last
arrayList->con[size] = input;
arrayList->numElements = arrayList->numElements + 1
}
void resize(ArrayList *arrayList) {
int num = arrayList->numElements;
int oldSize = arrayList->conSize;
int newSize = oldSize + 50;
int *temp = realloc(arrayList->con, sizeof(type) * newSize);
if (temp != NULL) {
arrayList->con = temp;
arrayList->conSize = newSize;
}
}
int remove(ArrayList * arrayList, int val) {
int i = 0;
while (arrayList->con[i] != val) {
i++;
}
//remove this index
if (i == arrayList->conSize) {
return -1;
}
else {
int removedVal = arrayList->con[i]; int j;
for (j = i; j < arrayList->numElements ; j++) {
arrayList->con[j] = arrayList->con[j + 1];
}
arrayList->con[j + 1] = NULL;
arrayList->numElements = arrayList->numElements - 1;
return removedVal;
}
}

Answer 1

If you want the array list be able to store any type of data, you need to
1) make con a void pointer. void *con;
2) store additional metadata in the struct about the memory alignment of the type
3) add one more parameter to the constructor of array list, which is the additional metadata mentioned in 2)
4) when allocating memory, use the stored metadata instead of sizeof(whatever), like temp=malloc(stored_metadata_about_type*50);
Also notice that it is not usually a good idea to hardcode 50, and better declare it as a constant like buffer_size.