void *foo_vtable;

struct Foo
{
 void *vtable;
 int truc;
}

struct Foo* init_foo()
{
 Foo *f = malloc(sizeof(*f));
f->vtable = foo_vtable;
}


int main()
{
 foo_vtable = malloc(x * sizeof(void*));
foo_vtable[0] = (void*)&foo_func;
}