__DECONST
iov.iov_base = __DECONST(char *, buf);
iov->iov_base = (__DECONST(char *, iov->iov_base)) + wlen;
iov[0].iov_base = __DECONST(char *, str);
iov[1].iov_base = __DECONST(char *, ENDL);