FAILED_LPOS
blk_lpos->begin = FAILED_LPOS;
blk_lpos->next = FAILED_LPOS;
(blk_lpos->begin == FAILED_LPOS && blk_lpos->next == FAILED_LPOS)) {
descs[_DESCS_COUNT(descbits) - 1].text_blk_lpos.begin = FAILED_LPOS;
descs[_DESCS_COUNT(descbits) - 1].text_blk_lpos.next = FAILED_LPOS;
.begin = FAILED_LPOS, \
.next = FAILED_LPOS, \