Hello Nick Terrell,
I grepped the README for zstd and it doesn't appear there is a mailing
list to add to the CC.
The patch c684b4e9a301: "lib: zstd: Upgrade to latest upstream zstd
version 1.4.10" from Sep 11, 2020, leads to the following Smatch static
checker warnings:
lib/zstd/compress/zstd_opt.c:695 ZSTD_insertBtAndGetAllMatches() warn: should this be 'nbCompares == -1'
lib/zstd/compress/zstd_lazy.c:360 ZSTD_DUBT_findBestMatch() warn: should this be 'nbCompares == -1'
lib/zstd/compress/zstd_lazy.c:1267 ZSTD_compressBlock_lazy_extDict_generic() warn: inconsistent indenting
lib/zstd/compress/zstd_compress.c:726 ZSTD_CCtxParams_setParameter() warn: no lower bound on 'value'
lib/zstd/decompress/zstd_decompress.c:177 ZSTD_createDDictHashSet() warn: variable dereferenced before check 'ret' (see line 174)
lib/zstd/compress/zstd_opt.c
508 FORCE_INLINE_TEMPLATE
509 U32 ZSTD_insertBtAndGetAllMatches (
510 ZSTD_match_t* matches, /* store result (found matches) in this table (presumed large enough) */
511 ZSTD_matchState_t* ms,
512 U32* nextToUpdate3,
513 const BYTE* const ip, const BYTE* const iLimit, const ZSTD_dictMode_e dictMode,
514 const U32 rep[ZSTD_REP_NUM],
515 U32 const ll0, /* tells if associated literal length is 0 or not. This value must be 0 or 1 */
516 const U32 lengthToBeat,
517 U32 const mls /* template */)
518 {
519 const ZSTD_compressionParameters* const cParams = &ms->cParams;
520 U32 const sufficient_len = MIN(cParams->targetLength, ZSTD_OPT_NUM -1);
521 const BYTE* const base = ms->window.base;
522 U32 const curr = (U32)(ip-base);
523 U32 const hashLog = cParams->hashLog;
524 U32 const minMatch = (mls==3) ? 3 : 4;
525 U32* const hashTable = ms->hashTable;
526 size_t const h = ZSTD_hashPtr(ip, hashLog, mls);
527 U32 matchIndex = hashTable[h];
528 U32* const bt = ms->chainTable;
529 U32 const btLog = cParams->chainLog - 1;
530 U32 const btMask= (1U << btLog) - 1;
531 size_t commonLengthSmaller=0, commonLengthLarger=0;
532 const BYTE* const dictBase = ms->window.dictBase;
533 U32 const dictLimit = ms->window.dictLimit;
534 const BYTE* const dictEnd = dictBase + dictLimit;
535 const BYTE* const prefixStart = base + dictLimit;
536 U32 const btLow = (btMask >= curr) ? 0 : curr - btMask;
537 U32 const windowLow = ZSTD_getLowestMatchIndex(ms, curr, cParams->windowLog);
538 U32 const matchLow = windowLow ? windowLow : 1;
539 U32* smallerPtr = bt + 2*(curr&btMask);
540 U32* largerPtr = bt + 2*(curr&btMask) + 1;
541 U32 matchEndIdx = curr+8+1; /* farthest referenced position of any match => detects repetitive patterns */
542 U32 dummy32; /* to be nullified at the end */
543 U32 mnum = 0;
544 U32 nbCompares = 1U << cParams->searchLog;
^^^^^^^^^^^^^^
This is unsigned.
545
546 const ZSTD_matchState_t* dms = dictMode == ZSTD_dictMatchState ? ms->dictMatchState : NULL;
547 const ZSTD_compressionParameters* const dmsCParams =
548 dictMode == ZSTD_dictMatchState ? &dms->cParams : NULL;
549 const BYTE* const dmsBase = dictMode == ZSTD_dictMatchState ? dms->window.base : NULL;
550 const BYTE* const dmsEnd = dictMode == ZSTD_dictMatchState ? dms->window.nextSrc : NULL;
551 U32 const dmsHighLimit = dictMode == ZSTD_dictMatchState ? (U32)(dmsEnd - dmsBase) : 0;
552 U32 const dmsLowLimit = dictMode == ZSTD_dictMatchState ? dms->window.lowLimit : 0;
553 U32 const dmsIndexDelta = dictMode == ZSTD_dictMatchState ? windowLow - dmsHighLimit : 0;
554 U32 const dmsHashLog = dictMode == ZSTD_dictMatchState ? dmsCParams->hashLog : hashLog;
555 U32 const dmsBtLog = dictMode == ZSTD_dictMatchState ? dmsCParams->chainLog - 1 : btLog;
556 U32 const dmsBtMask = dictMode == ZSTD_dictMatchState ? (1U << dmsBtLog) - 1 : 0;
557 U32 const dmsBtLow = dictMode == ZSTD_dictMatchState && dmsBtMask < dmsHighLimit - dmsLowLimit ? dmsHighLimit - dmsBtMask : dmsLowLimit;
558
559 size_t bestLength = lengthToBeat-1;
560 DEBUGLOG(8, "ZSTD_insertBtAndGetAllMatches: current=%u", curr);
561
562 /* check repCode */
563 assert(ll0 <= 1); /* necessarily 1 or 0 */
564 { U32 const lastR = ZSTD_REP_NUM + ll0;
565 U32 repCode;
566 for (repCode = ll0; repCode < lastR; repCode++) {
567 U32 const repOffset = (repCode==ZSTD_REP_NUM) ? (rep[0] - 1) : rep[repCode];
568 U32 const repIndex = curr - repOffset;
569 U32 repLen = 0;
570 assert(curr >= dictLimit);
571 if (repOffset-1 /* intentional overflow, discards 0 and -1 */ < curr-dictLimit) { /* equivalent to `curr > repIndex >= dictLimit` */
572 /* We must validate the repcode offset because when we're using a dictionary the
573 * valid offset range shrinks when the dictionary goes out of bounds.
574 */
575 if ((repIndex >= windowLow) & (ZSTD_readMINMATCH(ip, minMatch) == ZSTD_readMINMATCH(ip - repOffset, minMatch))) {
576 repLen = (U32)ZSTD_count(ip+minMatch, ip+minMatch-repOffset, iLimit) + minMatch;
577 }
578 } else { /* repIndex < dictLimit || repIndex >= curr */
579 const BYTE* const repMatch = dictMode == ZSTD_dictMatchState ?
580 dmsBase + repIndex - dmsIndexDelta :
581 dictBase + repIndex;
582 assert(curr >= windowLow);
583 if ( dictMode == ZSTD_extDict
584 && ( ((repOffset-1) /*intentional overflow*/ < curr - windowLow) /* equivalent to `curr > repIndex >= windowLow` */
585 & (((U32)((dictLimit-1) - repIndex) >= 3) ) /* intentional overflow : do not test positions overlapping 2 memory segments */)
586 && (ZSTD_readMINMATCH(ip, minMatch) == ZSTD_readMINMATCH(repMatch, minMatch)) ) {
587 repLen = (U32)ZSTD_count_2segments(ip+minMatch, repMatch+minMatch, iLimit, dictEnd, prefixStart) + minMatch;
588 }
589 if (dictMode == ZSTD_dictMatchState
590 && ( ((repOffset-1) /*intentional overflow*/ < curr - (dmsLowLimit + dmsIndexDelta)) /* equivalent to `curr > repIndex >= dmsLowLimit` */
591 & ((U32)((dictLimit-1) - repIndex) >= 3) ) /* intentional overflow : do not test positions overlapping 2 memory segments */
592 && (ZSTD_readMINMATCH(ip, minMatch) == ZSTD_readMINMATCH(repMatch, minMatch)) ) {
593 repLen = (U32)ZSTD_count_2segments(ip+minMatch, repMatch+minMatch, iLimit, dmsEnd, prefixStart) + minMatch;
594 } }
595 /* save longer solution */
596 if (repLen > bestLength) {
597 DEBUGLOG(8, "found repCode %u (ll0:%u, offset:%u) of length %u",
598 repCode, ll0, repOffset, repLen);
599 bestLength = repLen;
600 matches[mnum].off = repCode - ll0;
601 matches[mnum].len = (U32)repLen;
602 mnum++;
603 if ( (repLen > sufficient_len)
604 | (ip+repLen == iLimit) ) { /* best possible */
605 return mnum;
606 } } } }
607
608 /* HC3 match finder */
609 if ((mls == 3) /*static*/ && (bestLength < mls)) {
610 U32 const matchIndex3 = ZSTD_insertAndFindFirstIndexHash3(ms, nextToUpdate3, ip);
611 if ((matchIndex3 >= matchLow)
612 & (curr - matchIndex3 < (1<<18)) /*heuristic : longer distance likely too expensive*/ ) {
613 size_t mlen;
614 if ((dictMode == ZSTD_noDict) /*static*/ || (dictMode == ZSTD_dictMatchState) /*static*/ || (matchIndex3 >= dictLimit)) {
615 const BYTE* const match = base + matchIndex3;
616 mlen = ZSTD_count(ip, match, iLimit);
617 } else {
618 const BYTE* const match = dictBase + matchIndex3;
619 mlen = ZSTD_count_2segments(ip, match, iLimit, dictEnd, prefixStart);
620 }
621
622 /* save best solution */
623 if (mlen >= mls /* == 3 > bestLength */) {
624 DEBUGLOG(8, "found small match with hlog3, of length %u",
625 (U32)mlen);
626 bestLength = mlen;
627 assert(curr > matchIndex3);
628 assert(mnum==0); /* no prior solution */
629 matches[0].off = (curr - matchIndex3) + ZSTD_REP_MOVE;
630 matches[0].len = (U32)mlen;
631 mnum = 1;
632 if ( (mlen > sufficient_len) |
633 (ip+mlen == iLimit) ) { /* best possible length */
634 ms->nextToUpdate = curr+1; /* skip insertion */
635 return 1;
636 } } }
637 /* no dictMatchState lookup: dicts don't have a populated HC3 table */
638 }
639
640 hashTable[h] = curr; /* Update Hash Table */
641
642 while (nbCompares-- && (matchIndex >= matchLow)) {
^^^^^^^^^^^^
This is a post op so it will exit the loop with nbCompares set to -1U.
643 U32* const nextPtr = bt + 2*(matchIndex & btMask);
644 const BYTE* match;
645 size_t matchLength = MIN(commonLengthSmaller, commonLengthLarger); /* guaranteed minimum nb of common bytes */
646 assert(curr > matchIndex);
647
648 if ((dictMode == ZSTD_noDict) || (dictMode == ZSTD_dictMatchState) || (matchIndex+matchLength >= dictLimit)) {
649 assert(matchIndex+matchLength >= dictLimit); /* ensure the condition is correct when !extDict */
650 match = base + matchIndex;
651 if (matchIndex >= dictLimit) assert(memcmp(match, ip, matchLength) == 0); /* ensure early section of match is equal as expected */
652 matchLength += ZSTD_count(ip+matchLength, match+matchLength, iLimit);
653 } else {
654 match = dictBase + matchIndex;
655 assert(memcmp(match, ip, matchLength) == 0); /* ensure early section of match is equal as expected */
656 matchLength += ZSTD_count_2segments(ip+matchLength, match+matchLength, iLimit, dictEnd, prefixStart);
657 if (matchIndex+matchLength >= dictLimit)
658 match = base + matchIndex; /* prepare for match[matchLength] read */
659 }
660
661 if (matchLength > bestLength) {
662 DEBUGLOG(8, "found match of length %u at distance %u (offCode=%u)",
663 (U32)matchLength, curr - matchIndex, curr - matchIndex + ZSTD_REP_MOVE);
664 assert(matchEndIdx > matchIndex);
665 if (matchLength > matchEndIdx - matchIndex)
666 matchEndIdx = matchIndex + (U32)matchLength;
667 bestLength = matchLength;
668 matches[mnum].off = (curr - matchIndex) + ZSTD_REP_MOVE;
669 matches[mnum].len = (U32)matchLength;
670 mnum++;
671 if ( (matchLength > ZSTD_OPT_NUM)
672 | (ip+matchLength == iLimit) /* equal : no way to know if inf or sup */) {
673 if (dictMode == ZSTD_dictMatchState) nbCompares = 0; /* break should also skip searching dms */
^^^^^^^^^^^^^^
Or it could exit here.
674 break; /* drop, to preserve bt consistency (miss a little bit of compression) */
675 }
676 }
677
678 if (match[matchLength] < ip[matchLength]) {
679 /* match smaller than current */
680 *smallerPtr = matchIndex; /* update smaller idx */
681 commonLengthSmaller = matchLength; /* all smaller will now have at least this guaranteed common length */
682 if (matchIndex <= btLow) { smallerPtr=&dummy32; break; } /* beyond tree size, stop the search */
683 smallerPtr = nextPtr+1; /* new candidate => larger than match, which was smaller than current */
684 matchIndex = nextPtr[1]; /* new matchIndex, larger than previous, closer to current */
685 } else {
686 *largerPtr = matchIndex;
687 commonLengthLarger = matchLength;
688 if (matchIndex <= btLow) { largerPtr=&dummy32; break; } /* beyond tree size, stop the search */
689 largerPtr = nextPtr;
690 matchIndex = nextPtr[0];
691 } }
692
693 *smallerPtr = *largerPtr = 0;
694
--> 695 if (dictMode == ZSTD_dictMatchState && nbCompares) {
^^^^^^^^^^
The should this be check for if nbCompares == -1? This could be
intentional. Hard to tell.
696 size_t const dmsH = ZSTD_hashPtr(ip, dmsHashLog, mls);
697 U32 dictMatchIndex = dms->hashTable[dmsH];
698 const U32* const dmsBt = dms->chainTable;
699 commonLengthSmaller = commonLengthLarger = 0;
700 while (nbCompares-- && (dictMatchIndex > dmsLowLimit)) {
701 const U32* const nextPtr = dmsBt + 2*(dictMatchIndex & dmsBtMask);
702 size_t matchLength = MIN(commonLengthSmaller, commonLengthLarger); /* guaranteed minimum nb of common bytes */
703 const BYTE* match = dmsBase + dictMatchIndex;
704 matchLength += ZSTD_count_2segments(ip+matchLength, match+matchLength, iLimit, dmsEnd, prefixStart);
705 if (dictMatchIndex+matchLength >= dmsHighLimit)
706 match = base + dictMatchIndex + dmsIndexDelta; /* to prepare for next usage of match[matchLength] */
707
708 if (matchLength > bestLength) {
709 matchIndex = dictMatchIndex + dmsIndexDelta;
710 DEBUGLOG(8, "found dms match of length %u at distance %u (offCode=%u)",
711 (U32)matchLength, curr - matchIndex, curr - matchIndex + ZSTD_REP_MOVE);
712 if (matchLength > matchEndIdx - matchIndex)
713 matchEndIdx = matchIndex + (U32)matchLength;
714 bestLength = matchLength;
715 matches[mnum].off = (curr - matchIndex) + ZSTD_REP_MOVE;
716 matches[mnum].len = (U32)matchLength;
717 mnum++;
718 if ( (matchLength > ZSTD_OPT_NUM)
719 | (ip+matchLength == iLimit) /* equal : no way to know if inf or sup */) {
720 break; /* drop, to guarantee consistency (miss a little bit of compression) */
721 }
722 }
723
724 if (dictMatchIndex <= dmsBtLow) { break; } /* beyond tree size, stop the search */
725 if (match[matchLength] < ip[matchLength]) {
726 commonLengthSmaller = matchLength; /* all smaller will now have at least this guaranteed common length */
727 dictMatchIndex = nextPtr[1]; /* new matchIndex larger than previous (closer to current) */
728 } else {
729 /* match is larger than current */
730 commonLengthLarger = matchLength;
731 dictMatchIndex = nextPtr[0];
732 }
733 }
734 }
735
736 assert(matchEndIdx > curr+8);
737 ms->nextToUpdate = matchEndIdx - 8; /* skip repetitive patterns */
738 return mnum;
739 }
regards,
dan carpenter
