Should not be necessary for D? extern (C): int wnsprintfA(LPSTR, int, LPCSTR, ...); int wnsprintfW(LPWSTR, int, LPCWSTR, ...); extern (Windows): int wvnsprintfA(LPSTR, int, LPCSTR, va_list); int wvnsprintfW(LPWSTR, int, LPCWSTR, va_list);