OOP in C simple example constructors

#include <stdio.h>
#include <stdlib.h>
typedef struct base base_t;
typedef struct child child_t;
#define INIT() \
    base_t base; \
    child_t child; \
    printf("Init done...\n");

#define NEW(a) _Generic((a), \
    base_t: base_new(), \
    child_t: child_new())

#define NEW_1(a, b) _Generic((a), \
    base_t: base_new_1(b), \
    child_t: child_new())

typedef struct base{
    int (*getId)(void* self);
    void (*free)(void* self);
    int id;
} base_t;

int getId(void* self){return ((base_t*)self)->id;}
void base_free(void* bse){base_t* bs = (base_t*)bse; free(bs);}

base_t* base_new(){
    base_t *res = malloc(sizeof(base_t));
    res->getId = getId;
    res->free = base_free;
    return res;
}

base_t* base_new_1(int id){
    base_t *res = malloc(sizeof(base_t));
    res->getId = getId;
    res->free = base_free;
    res->id = id;
    return res;
}

typedef struct child{
    int (*getId)(void* self);
    void (*free)(void* self);
    base_t *super;
    char name[10];
} child_t;

int getChildId(void* self){ return ((child_t*)self)->super->id;}

void child_free(void* bse){
    child_t* chld = (child_t*)bse;
    chld->super->free(chld->super);
    free(chld);
}

child_t* child_new(){
    child_t* chld = malloc(sizeof(child_t));
    chld->super = base_new();
    chld->getId = getChildId;
    chld->free = child_free;
    return chld;
}

int main(int argc, char **argv){
    INIT(); //init base child for constructors
    base_t *bse = NEW_1(base, 2); //constructor
    child_t *chld;
    chld = NEW(child); //constructor
    chld->name[0] = '1';
    chld->super->id = 1;
    const int n = 3;
    void* mass[3] = {bse, chld, NEW_1(base, 10)};
    for (int i=0; i<n; i++){
        //int id = ((base_t*)mass[i])->getId(mass[i]); //Polymorphism
        int id = ((child_t*)mass[i])->getId(mass[i]); //Polymorphism
        printf("id =%i\n", id);
    }
    chld->free(chld);
    bse->free(bse);
    return 0;
}