Native calling interface: how to translate "wchar_t"?

I would like to use the ncurses int addwstr(const wchar_t *wstr); function in Perl6.

How could I get a Perl 6 signatures which conveys const wchar_t *wstr of addwstr?

use v6;
use NativeCall;

constant LIB = 'libncursesw.so.5';

sub addwstr(  ?  ) returns int32 is native(LIB) is export {*};