struct array {
    int* data;
    int size;
};

struct array* array_create()
{
    struct array* array = (struct array*) malloc(sizeof(struct array));
    array->data = (int*) malloc(sizeof(int) * 10000);
    array->size = 10000;
    return array;
}

void array_resize(struct array* array, int size)
{
    if (size > array->size) {
        free(array);
        array->data = (int*) malloc(sizeof(int) * size);
    }

    array->size = size;
}

int array_size(struct array* array)
{
    return array->size;
}

typedef struct array* ARRAY;

ARRAY array_create();
void array_resize(struct array* array, int size);

void edit()
{
    array_resize(array, 100); // I can run the code but program crashes
}

ARRAY array;
array = array_create();
edit();                       // Program crashes

free(array);
    array->data = (int*) malloc(sizeof(int) * size);

void array_resize(struct array* array, int size)
{
    if (size > array->size) {
        free(array);
        array->data = (int*) malloc(sizeof(int) * size);
    }

    array->size = size;
}

struct array;
struct array *array_create();