__sseek
fp->_seek = __sseek;
__sseek(fp->_cookie, -off, SEEK_CUR);
if (fp->_seek != __sseek || fp->_file < 0) {
__sseek(fp->_cookie, off, SEEK_SET);
._close = __sclose, ._read = __sread, ._seek = __sseek, \
fp->_seek = __sseek;
(void) __sseek(fp, 0, SEEK_END);
fp->_seek = __sseek;
(void) __sseek(fp, 0, SEEK_END);
if (seekfn != __sseek ||
fpos_t __sseek(void *, fpos_t, int);
return ((st.st_mode & S_IFMT) == S_IFREG && fp->_seek == __sseek ?