Thanks a lot. This solves the problem. However, it breaks the abstractness. Now in D side, we can call auto v = ab(). This does not make sense, because then &v cannot be used in the C library.
I don't understand why when we manipulate AB*, D compiler needs to know the size of struct ab. Moreover, when we use AB*[int], the D compiler complains about there's no opHash defined for AB. I don't think they are necessary at all.
