typedef struct {
     foo @*data; //Non-nullable pointer to nullable pointer of foo
     size_t size;
     size_t fill;
  } foo_vec;
  
  void foo_vec_push(foo_vec @v, foo @x) {
    if (v->fill == v->size) {
      //realloc and zero data
    } else {
      data[idx++] = v;
    }
  }
  
  foo @ foo_vec_get(foo_vec @v, size_t idx) {
    if (idx < fill) {
      return (foo @)(data+idx);
    } else {
      abort();
    }
  }