Terry, the provided example is incomplete and doesn't make sense as it stands. For better or worse, windll.dllname attempts to load WinDLL(dllname) and cache the resulting library on the windll loader. (The library in turn caches function pointers, which means this design is a problem waiting to happen, which has happened a few times with various projects conflicting with each other over windll.kernel32 function prototypes. I recommend using WinDLL instead.)

I gather that Erwan wants ctypes.byref() and the implicit _byref that's called by PyCPointerType_from_param to be enhanced to support objects that define _as_parameter_. So I'm changing the issue type accordingly.