seek_offset
if (out.seek_offset > 0 && (out.flags & ISTRUNC)) {
if (ftruncate(out.fd, out.seek_offset) == -1)
out.seek_offset = lseek(out.fd, pending, SEEK_CUR);
if (out.seek_offset == -1)
out.seek_offset = 0;
off_t seek_offset; /* offset of last seek past output hole */
if (lseek(out.fd, seek_offset(&out), SEEK_CUR) == -1 &&
if (lseek(in.fd, seek_offset(&in), SEEK_CUR) == -1 &&