OOP in C

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

struct MaClasse;

typedef struct MaClasse
{
    void (*init)(struct MaClasse** this);
    void (*free)(struct MaClasse** this);
    void (*print)(void);
} MaClasse;

void MaClasse_init(struct MaClasse** this);
void MaClasse_free(struct MaClasse** this);
void MaClasse_print();

void MaClasse_init(struct MaClasse** this)
{
    *this = (MaClasse*) calloc(1, sizeof(MaClasse));
    (*this)->init = &MaClasse_init;
    (*this)->free = &MaClasse_free;
    (*this)->print = &MaClasse_print;
}

void MaClasse_free(struct MaClasse** this)
{
    free(*this);
    *this = NULL;
}

void MaClasse_print()
{
    printf("Hello World!\n");
}

int main(void)
{
    MaClasse *a;
    MaClasse_init(&a);
    a->print();
    a->free(&a);
    return EXIT_SUCCESS;
}