Import SQLite 3.8.7.4.

third_party/sqlite/patches/0023-fts2-Fix-numerous-out-of-bounds-bugs-reading-corrupt.patch

-From 106d71238a58d4dfbeb8cf1cba45a1c4e6f583e8 Mon Sep 17 00:00:00 2001
-From: Chris Evans <cevans@chromium.org>
-Date: Wed, 30 Sep 2009 23:10:34 +0000
-Subject: [PATCH 23/23] [fts2] Fix numerous out-of-bounds bugs reading corrupt
- database.
-
-Fix numerous bugs in fts2 where a corrupt fts2 database could cause
-out-of-bounds reads and writes.
-
-Original review URL is more descriptive:
-http://codereview.chromium.org/216026
----
- third_party/sqlite/src/ext/fts2/fts2.c | 751 ++++++++++++++++++++++-----------
- 1 file changed, 514 insertions(+), 237 deletions(-)
-
-diff --git a/third_party/sqlite/src/ext/fts2/fts2.c b/third_party/sqlite/src/ext/fts2/fts2.c
-index d5587b3..36d14ff 100644
---- a/third_party/sqlite/src/ext/fts2/fts2.c
-+++ b/third_party/sqlite/src/ext/fts2/fts2.c
-@@ -447,30 +447,41 @@ static int putVarint(char *p, sqlite_int64 v){
- /* Read a 64-bit variable-length integer from memory starting at p[0].
-  * Return the number of bytes read, or 0 on error.
-  * The value is stored in *v. */
--static int getVarint(const char *p, sqlite_int64 *v){
-+static int getVarintSafe(const char *p, sqlite_int64 *v, int max){
-   const unsigned char *q = (const unsigned char *) p;
-   sqlite_uint64 x = 0, y = 1;
--  while( (*q & 0x80) == 0x80 ){
-+  if( max>VARINT_MAX ) max = VARINT_MAX;
-+  while( max && (*q & 0x80) == 0x80 ){
-+    max--;
-     x += y * (*q++ & 0x7f);
-     y <<= 7;
--    if( q - (unsigned char *)p >= VARINT_MAX ){  /* bad data */
--      assert( 0 );
--      return 0;
--    }
-+  }
-+  if ( !max ){
-+    assert( 0 );
-+    return 0;  /* tried to read too much; bad data */
-   }
-   x += y * (*q++);
-   *v = (sqlite_int64) x;
-   return (int) (q - (unsigned char *)p);
- }
- 
--static int getVarint32(const char *p, int *pi){
-+static int getVarint(const char *p, sqlite_int64 *v){
-+  return getVarintSafe(p, v, VARINT_MAX);
-+}
-+
-+static int getVarint32Safe(const char *p, int *pi, int max){
-  sqlite_int64 i;
-- int ret = getVarint(p, &i);
-+ int ret = getVarintSafe(p, &i, max);
-+ if( !ret ) return ret;
-  *pi = (int) i;
-  assert( *pi==i );
-  return ret;
- }
- 
-+static int getVarint32(const char* p, int *pi){
-+  return getVarint32Safe(p, pi, VARINT_MAX);
-+}
-+
- /*******************************************************************/
- /* DataBuffer is used to collect data into a buffer in piecemeal
- ** fashion.  It implements the usual distinction between amount of
-@@ -639,7 +650,7 @@ typedef struct DLReader {
- 
- static int dlrAtEnd(DLReader *pReader){
-   assert( pReader->nData>=0 );
--  return pReader->nData==0;
-+  return pReader->nData<=0;
- }
- static sqlite_int64 dlrDocid(DLReader *pReader){
-   assert( !dlrAtEnd(pReader) );
-@@ -663,7 +674,8 @@ static int dlrAllDataBytes(DLReader *pReader){
- */
- static const char *dlrPosData(DLReader *pReader){
-   sqlite_int64 iDummy;
--  int n = getVarint(pReader->pData, &iDummy);
-+  int n = getVarintSafe(pReader->pData, &iDummy, pReader->nElement);
-+  if( !n ) return NULL;
-   assert( !dlrAtEnd(pReader) );
-   return pReader->pData+n;
- }
-@@ -673,7 +685,7 @@ static int dlrPosDataLen(DLReader *pReader){
-   assert( !dlrAtEnd(pReader) );
-   return pReader->nElement-n;
- }
--static void dlrStep(DLReader *pReader){
-+static int dlrStep(DLReader *pReader){
-   assert( !dlrAtEnd(pReader) );
- 
-   /* Skip past current doclist element. */
-@@ -682,32 +694,48 @@ static void dlrStep(DLReader *pReader){
-   pReader->nData -= pReader->nElement;
- 
-   /* If there is more data, read the next doclist element. */
--  if( pReader->nData!=0 ){
-+  if( pReader->nData>0 ){
-     sqlite_int64 iDocidDelta;
--    int iDummy, n = getVarint(pReader->pData, &iDocidDelta);
-+    int nTotal = 0;
-+    int iDummy, n = getVarintSafe(pReader->pData, &iDocidDelta, pReader->nData);
-+    if( !n ) return SQLITE_CORRUPT_BKPT;
-+    nTotal += n;
-     pReader->iDocid += iDocidDelta;
-     if( pReader->iType>=DL_POSITIONS ){
--      assert( n<pReader->nData );
-       while( 1 ){
--        n += getVarint32(pReader->pData+n, &iDummy);
--        assert( n<=pReader->nData );
-+        n = getVarint32Safe(pReader->pData+nTotal, &iDummy,
-+                            pReader->nData-nTotal);
-+        if( !n ) return SQLITE_CORRUPT_BKPT;
-+        nTotal += n;
-         if( iDummy==POS_END ) break;
-         if( iDummy==POS_COLUMN ){
--          n += getVarint32(pReader->pData+n, &iDummy);
--          assert( n<pReader->nData );
-+          n = getVarint32Safe(pReader->pData+nTotal, &iDummy,
-+                              pReader->nData-nTotal);
-+          if( !n ) return SQLITE_CORRUPT_BKPT;
-+          nTotal += n;
-         }else if( pReader->iType==DL_POSITIONS_OFFSETS ){
--          n += getVarint32(pReader->pData+n, &iDummy);
--          n += getVarint32(pReader->pData+n, &iDummy);
--          assert( n<pReader->nData );
-+          n = getVarint32Safe(pReader->pData+nTotal, &iDummy,
-+                              pReader->nData-nTotal);
-+          if( !n ) return SQLITE_CORRUPT_BKPT;
-+          nTotal += n;
-+          n = getVarint32Safe(pReader->pData+nTotal, &iDummy,
-+                              pReader->nData-nTotal);
-+          if( !n ) return SQLITE_CORRUPT_BKPT;
-+          nTotal += n;
-         }
-       }
-     }
--    pReader->nElement = n;
-+    pReader->nElement = nTotal;
-     assert( pReader->nElement<=pReader->nData );
-   }
-+  return SQLITE_OK;
- }
--static void dlrInit(DLReader *pReader, DocListType iType,
--                    const char *pData, int nData){
-+static void dlrDestroy(DLReader *pReader){
-+  SCRAMBLE(pReader);
-+}
-+static int dlrInit(DLReader *pReader, DocListType iType,
-+                   const char *pData, int nData){
-+  int rc;
-   assert( pData!=NULL && nData!=0 );
-   pReader->iType = iType;
-   pReader->pData = pData;
-@@ -716,10 +744,9 @@ static void dlrInit(DLReader *pReader, DocListType iType,
-   pReader->iDocid = 0;
- 
-   /* Load the first element's data.  There must be a first element. */
--  dlrStep(pReader);
--}
--static void dlrDestroy(DLReader *pReader){
--  SCRAMBLE(pReader);
-+  rc = dlrStep(pReader);
-+  if( rc!=SQLITE_OK ) dlrDestroy(pReader);
-+  return rc;
- }
- 
- #ifndef NDEBUG
-@@ -806,9 +833,9 @@ static void dlwDestroy(DLWriter *pWriter){
- /* TODO(shess) This has become just a helper for docListMerge.
- ** Consider a refactor to make this cleaner.
- */
--static void dlwAppend(DLWriter *pWriter,
--                      const char *pData, int nData,
--                      sqlite_int64 iFirstDocid, sqlite_int64 iLastDocid){
-+static int dlwAppend(DLWriter *pWriter,
-+                     const char *pData, int nData,
-+                     sqlite_int64 iFirstDocid, sqlite_int64 iLastDocid){
-   sqlite_int64 iDocid = 0;
-   char c[VARINT_MAX];
-   int nFirstOld, nFirstNew;     /* Old and new varint len of first docid. */
-@@ -817,7 +844,8 @@ static void dlwAppend(DLWriter *pWriter,
- #endif
- 
-   /* Recode the initial docid as delta from iPrevDocid. */
--  nFirstOld = getVarint(pData, &iDocid);
-+  nFirstOld = getVarintSafe(pData, &iDocid, nData);
-+  if( !nFirstOld ) return SQLITE_CORRUPT_BKPT;
-   assert( nFirstOld<nData || (nFirstOld==nData && pWriter->iType==DL_DOCIDS) );
-   nFirstNew = putVarint(c, iFirstDocid-pWriter->iPrevDocid);
- 
-@@ -838,10 +866,11 @@ static void dlwAppend(DLWriter *pWriter,
-     dataBufferAppend(pWriter->b, c, nFirstNew);
-   }
-   pWriter->iPrevDocid = iLastDocid;
-+  return SQLITE_OK;
- }
--static void dlwCopy(DLWriter *pWriter, DLReader *pReader){
--  dlwAppend(pWriter, dlrDocData(pReader), dlrDocDataBytes(pReader),
--            dlrDocid(pReader), dlrDocid(pReader));
-+static int dlwCopy(DLWriter *pWriter, DLReader *pReader){
-+  return dlwAppend(pWriter, dlrDocData(pReader), dlrDocDataBytes(pReader),
-+                   dlrDocid(pReader), dlrDocid(pReader));
- }
- static void dlwAdd(DLWriter *pWriter, sqlite_int64 iDocid){
-   char c[VARINT_MAX];
-@@ -902,45 +931,63 @@ static int plrEndOffset(PLReader *pReader){
-   assert( !plrAtEnd(pReader) );
-   return pReader->iEndOffset;
- }
--static void plrStep(PLReader *pReader){
--  int i, n;
-+static int plrStep(PLReader *pReader){
-+  int i, n, nTotal = 0;
- 
-   assert( !plrAtEnd(pReader) );
- 
--  if( pReader->nData==0 ){
-+  if( pReader->nData<=0 ){
-     pReader->pData = NULL;
--    return;
-+    return SQLITE_OK;
-   }
- 
--  n = getVarint32(pReader->pData, &i);
-+  n = getVarint32Safe(pReader->pData, &i, pReader->nData);
-+  if( !n ) return SQLITE_CORRUPT_BKPT;
-+  nTotal += n;
-   if( i==POS_COLUMN ){
--    n += getVarint32(pReader->pData+n, &pReader->iColumn);
-+    n = getVarint32Safe(pReader->pData+nTotal, &pReader->iColumn,
-+                        pReader->nData-nTotal);
-+    if( !n ) return SQLITE_CORRUPT_BKPT;
-+    nTotal += n;
-     pReader->iPosition = 0;
-     pReader->iStartOffset = 0;
--    n += getVarint32(pReader->pData+n, &i);
-+    n = getVarint32Safe(pReader->pData+nTotal, &i, pReader->nData-nTotal);
-+    if( !n ) return SQLITE_CORRUPT_BKPT;
-+    nTotal += n;
-   }
-   /* Should never see adjacent column changes. */
-   assert( i!=POS_COLUMN );
- 
-   if( i==POS_END ){
-+    assert( nTotal<=pReader->nData );
-     pReader->nData = 0;
-     pReader->pData = NULL;
--    return;
-+    return SQLITE_OK;
-   }
- 
-   pReader->iPosition += i-POS_BASE;
-   if( pReader->iType==DL_POSITIONS_OFFSETS ){
--    n += getVarint32(pReader->pData+n, &i);
-+    n = getVarint32Safe(pReader->pData+nTotal, &i, pReader->nData-nTotal);
-+    if( !n ) return SQLITE_CORRUPT_BKPT;
-+    nTotal += n;
-     pReader->iStartOffset += i;
--    n += getVarint32(pReader->pData+n, &i);
-+    n = getVarint32Safe(pReader->pData+nTotal, &i, pReader->nData-nTotal);
-+    if( !n ) return SQLITE_CORRUPT_BKPT;
-+    nTotal += n;
-     pReader->iEndOffset = pReader->iStartOffset+i;
-   }
--  assert( n<=pReader->nData );
--  pReader->pData += n;
--  pReader->nData -= n;
-+  assert( nTotal<=pReader->nData );
-+  pReader->pData += nTotal;
-+  pReader->nData -= nTotal;
-+  return SQLITE_OK;
- }
- 
--static void plrInit(PLReader *pReader, DLReader *pDLReader){
-+static void plrDestroy(PLReader *pReader){
-+  SCRAMBLE(pReader);
-+}
-+
-+static int plrInit(PLReader *pReader, DLReader *pDLReader){
-+  int rc;
-   pReader->pData = dlrPosData(pDLReader);
-   pReader->nData = dlrPosDataLen(pDLReader);
-   pReader->iType = pDLReader->iType;
-@@ -948,10 +995,9 @@ static void plrInit(PLReader *pReader, DLReader *pDLReader){
-   pReader->iPosition = 0;
-   pReader->iStartOffset = 0;
-   pReader->iEndOffset = 0;
--  plrStep(pReader);
--}
--static void plrDestroy(PLReader *pReader){
--  SCRAMBLE(pReader);
-+  rc = plrStep(pReader);
-+  if( rc!=SQLITE_OK ) plrDestroy(pReader);
-+  return rc;
- }
- 
- /*******************************************************************/
-@@ -1137,14 +1183,16 @@ static void dlcDelete(DLCollector *pCollector){
- ** deletion will be trimmed, and will thus not effect a deletion
- ** during the merge.
- */
--static void docListTrim(DocListType iType, const char *pData, int nData,
--                        int iColumn, DocListType iOutType, DataBuffer *out){
-+static int docListTrim(DocListType iType, const char *pData, int nData,
-+                       int iColumn, DocListType iOutType, DataBuffer *out){
-   DLReader dlReader;
-   DLWriter dlWriter;
-+  int rc;
- 
-   assert( iOutType<=iType );
- 
--  dlrInit(&dlReader, iType, pData, nData);
-+  rc = dlrInit(&dlReader, iType, pData, nData);
-+  if( rc!=SQLITE_OK ) return rc;
-   dlwInit(&dlWriter, iOutType, out);
- 
-   while( !dlrAtEnd(&dlReader) ){
-@@ -1152,7 +1200,8 @@ static void docListTrim(DocListType iType, const char *pData, int nData,
-     PLWriter plWriter;
-     int match = 0;
- 
--    plrInit(&plReader, &dlReader);
-+    rc = plrInit(&plReader, &dlReader);
-+    if( rc!=SQLITE_OK ) break;
- 
-     while( !plrAtEnd(&plReader) ){
-       if( iColumn==-1 || plrColumn(&plReader)==iColumn ){
-@@ -1163,7 +1212,11 @@ static void docListTrim(DocListType iType, const char *pData, int nData,
-         plwAdd(&plWriter, plrColumn(&plReader), plrPosition(&plReader),
-                plrStartOffset(&plReader), plrEndOffset(&plReader));
-       }
--      plrStep(&plReader);
-+      rc = plrStep(&plReader);
-+      if( rc!=SQLITE_OK ){
-+        plrDestroy(&plReader);
-+        goto err;
-+      }
-     }
-     if( match ){
-       plwTerminate(&plWriter);
-@@ -1171,10 +1224,13 @@ static void docListTrim(DocListType iType, const char *pData, int nData,
-     }
- 
-     plrDestroy(&plReader);
--    dlrStep(&dlReader);
-+    rc = dlrStep(&dlReader);
-+    if( rc!=SQLITE_OK ) break;
-   }
-+err:
-   dlwDestroy(&dlWriter);
-   dlrDestroy(&dlReader);
-+  return rc;
- }
- 
- /* Used by docListMerge() to keep doclists in the ascending order by
-@@ -1231,19 +1287,20 @@ static void orderedDLReaderReorder(OrderedDLReader *p, int n){
- /* TODO(shess) nReaders must be <= MERGE_COUNT.  This should probably
- ** be fixed.
- */
--static void docListMerge(DataBuffer *out,
--                         DLReader *pReaders, int nReaders){
-+static int docListMerge(DataBuffer *out,
-+                        DLReader *pReaders, int nReaders){
-   OrderedDLReader readers[MERGE_COUNT];
-   DLWriter writer;
-   int i, n;
-   const char *pStart = 0;
-   int nStart = 0;
-   sqlite_int64 iFirstDocid = 0, iLastDocid = 0;
-+  int rc = SQLITE_OK;
- 
-   assert( nReaders>0 );
-   if( nReaders==1 ){
-     dataBufferAppend(out, dlrDocData(pReaders), dlrAllDataBytes(pReaders));
--    return;
-+    return SQLITE_OK;
-   }
- 
-   assert( nReaders<=MERGE_COUNT );
-@@ -1276,20 +1333,23 @@ static void docListMerge(DataBuffer *out,
-       nStart += dlrDocDataBytes(readers[0].pReader);
-     }else{
-       if( pStart!=0 ){
--        dlwAppend(&writer, pStart, nStart, iFirstDocid, iLastDocid);
-+        rc = dlwAppend(&writer, pStart, nStart, iFirstDocid, iLastDocid);
-+        if( rc!=SQLITE_OK ) goto err;
-       }
-       pStart = dlrDocData(readers[0].pReader);
-       nStart = dlrDocDataBytes(readers[0].pReader);
-       iFirstDocid = iDocid;
-     }
-     iLastDocid = iDocid;
--    dlrStep(readers[0].pReader);
-+    rc = dlrStep(readers[0].pReader);
-+    if( rc!=SQLITE_OK ) goto err;
- 
-     /* Drop all of the older elements with the same docid. */
-     for(i=1; i<nReaders &&
-              !dlrAtEnd(readers[i].pReader) &&
-              dlrDocid(readers[i].pReader)==iDocid; i++){
--      dlrStep(readers[i].pReader);
-+      rc = dlrStep(readers[i].pReader);
-+      if( rc!=SQLITE_OK ) goto err;
-     }
- 
-     /* Get the readers back into order. */
-@@ -1299,8 +1359,11 @@ static void docListMerge(DataBuffer *out,
-   }
- 
-   /* Copy over any remaining elements. */
--  if( nStart>0 ) dlwAppend(&writer, pStart, nStart, iFirstDocid, iLastDocid);
-+  if( nStart>0 )
-+    rc = dlwAppend(&writer, pStart, nStart, iFirstDocid, iLastDocid);
-+err:
-   dlwDestroy(&writer);
-+  return rc;
- }
- 
- /* Helper function for posListUnion().  Compares the current position
-@@ -1336,30 +1399,40 @@ static int posListCmp(PLReader *pLeft, PLReader *pRight){
- ** work with any doclist type, though both inputs and the output
- ** should be the same type.
- */
--static void posListUnion(DLReader *pLeft, DLReader *pRight, DLWriter *pOut){
-+static int posListUnion(DLReader *pLeft, DLReader *pRight, DLWriter *pOut){
-   PLReader left, right;
-   PLWriter writer;
-+  int rc;
- 
-   assert( dlrDocid(pLeft)==dlrDocid(pRight) );
-   assert( pLeft->iType==pRight->iType );
-   assert( pLeft->iType==pOut->iType );
- 
--  plrInit(&left, pLeft);
--  plrInit(&right, pRight);
-+  rc = plrInit(&left, pLeft);
-+  if( rc != SQLITE_OK ) return rc;
-+  rc = plrInit(&right, pRight);
-+  if( rc != SQLITE_OK ){
-+    plrDestroy(&left);
-+    return rc;
-+  }
-   plwInit(&writer, pOut, dlrDocid(pLeft));
- 
-   while( !plrAtEnd(&left) || !plrAtEnd(&right) ){
-     int c = posListCmp(&left, &right);
-     if( c<0 ){
-       plwCopy(&writer, &left);
--      plrStep(&left);
-+      rc = plrStep(&left);
-+      if( rc != SQLITE_OK ) break;
-     }else if( c>0 ){
-       plwCopy(&writer, &right);
--      plrStep(&right);
-+      rc = plrStep(&right);
-+      if( rc != SQLITE_OK ) break;
-     }else{
-       plwCopy(&writer, &left);
--      plrStep(&left);
--      plrStep(&right);
-+      rc = plrStep(&left);
-+      if( rc != SQLITE_OK ) break;
-+      rc = plrStep(&right);
-+      if( rc != SQLITE_OK ) break;
-     }
-   }
- 
-@@ -1367,56 +1440,75 @@ static void posListUnion(DLReader *pLeft, DLReader *pRight, DLWriter *pOut){
-   plwDestroy(&writer);
-   plrDestroy(&left);
-   plrDestroy(&right);
-+  return rc;
- }
- 
- /* Write the union of doclists in pLeft and pRight to pOut.  For
- ** docids in common between the inputs, the union of the position
- ** lists is written.  Inputs and outputs are always type DL_DEFAULT.
- */
--static void docListUnion(
-+static int docListUnion(
-   const char *pLeft, int nLeft,
-   const char *pRight, int nRight,
-   DataBuffer *pOut      /* Write the combined doclist here */
- ){
-   DLReader left, right;
-   DLWriter writer;
-+  int rc;
- 
-   if( nLeft==0 ){
-     if( nRight!=0) dataBufferAppend(pOut, pRight, nRight);
--    return;
-+    return SQLITE_OK;
-   }
-   if( nRight==0 ){
-     dataBufferAppend(pOut, pLeft, nLeft);
--    return;
-+    return SQLITE_OK;
-   }
- 
--  dlrInit(&left, DL_DEFAULT, pLeft, nLeft);
--  dlrInit(&right, DL_DEFAULT, pRight, nRight);
-+  rc = dlrInit(&left, DL_DEFAULT, pLeft, nLeft);
-+  if( rc!=SQLITE_OK ) return rc;
-+  rc = dlrInit(&right, DL_DEFAULT, pRight, nRight);
-+  if( rc!=SQLITE_OK ){
-+    dlrDestroy(&left);
-+    return rc;
-+  }
-   dlwInit(&writer, DL_DEFAULT, pOut);
- 
-   while( !dlrAtEnd(&left) || !dlrAtEnd(&right) ){
-     if( dlrAtEnd(&right) ){
--      dlwCopy(&writer, &left);
--      dlrStep(&left);
-+      rc = dlwCopy(&writer, &left);
-+      if( rc!=SQLITE_OK ) break;
-+      rc = dlrStep(&left);
-+      if( rc!=SQLITE_OK ) break;
-     }else if( dlrAtEnd(&left) ){
--      dlwCopy(&writer, &right);
--      dlrStep(&right);
-+      rc = dlwCopy(&writer, &right);
-+      if( rc!=SQLITE_OK ) break;
-+      rc = dlrStep(&right);
-+      if( rc!=SQLITE_OK ) break;
-     }else if( dlrDocid(&left)<dlrDocid(&right) ){
--      dlwCopy(&writer, &left);
--      dlrStep(&left);
-+      rc = dlwCopy(&writer, &left);
-+      if( rc!=SQLITE_OK ) break;
-+      rc = dlrStep(&left);
-+      if( rc!=SQLITE_OK ) break;
-     }else if( dlrDocid(&left)>dlrDocid(&right) ){
--      dlwCopy(&writer, &right);
--      dlrStep(&right);
-+      rc = dlwCopy(&writer, &right);
-+      if( rc!=SQLITE_OK ) break;
-+      rc = dlrStep(&right);
-+      if( rc!=SQLITE_OK ) break;
-     }else{
--      posListUnion(&left, &right, &writer);
--      dlrStep(&left);
--      dlrStep(&right);
-+      rc = posListUnion(&left, &right, &writer);
-+      if( rc!=SQLITE_OK ) break;
-+      rc = dlrStep(&left);
-+      if( rc!=SQLITE_OK ) break;
-+      rc = dlrStep(&right);
-+      if( rc!=SQLITE_OK ) break;
-     }
-   }
- 
-   dlrDestroy(&left);
-   dlrDestroy(&right);
-   dlwDestroy(&writer);
-+  return rc;
- }
- 
- /* pLeft and pRight are DLReaders positioned to the same docid.
-@@ -1431,35 +1523,47 @@ static void docListUnion(
- ** include the positions from pRight that are one more than a
- ** position in pLeft.  In other words:  pRight.iPos==pLeft.iPos+1.
- */
--static void posListPhraseMerge(DLReader *pLeft, DLReader *pRight,
--                               DLWriter *pOut){
-+static int posListPhraseMerge(DLReader *pLeft, DLReader *pRight,
-+                              DLWriter *pOut){
-   PLReader left, right;
-   PLWriter writer;
-   int match = 0;
-+  int rc;
- 
-   assert( dlrDocid(pLeft)==dlrDocid(pRight) );
-   assert( pOut->iType!=DL_POSITIONS_OFFSETS );
- 
--  plrInit(&left, pLeft);
--  plrInit(&right, pRight);
-+  rc = plrInit(&left, pLeft);
-+  if( rc!=SQLITE_OK ) return rc;
-+  rc = plrInit(&right, pRight);
-+  if( rc!=SQLITE_OK ){
-+    plrDestroy(&left);
-+    return rc;
-+  }
- 
-   while( !plrAtEnd(&left) && !plrAtEnd(&right) ){
-     if( plrColumn(&left)<plrColumn(&right) ){
--      plrStep(&left);
-+      rc = plrStep(&left);
-+      if( rc!=SQLITE_OK ) break;
-     }else if( plrColumn(&left)>plrColumn(&right) ){
--      plrStep(&right);
-+      rc = plrStep(&right);
-+      if( rc!=SQLITE_OK ) break;
-     }else if( plrPosition(&left)+1<plrPosition(&right) ){
--      plrStep(&left);
-+      rc = plrStep(&left);
-+      if( rc!=SQLITE_OK ) break;
-     }else if( plrPosition(&left)+1>plrPosition(&right) ){
--      plrStep(&right);
-+      rc = plrStep(&right);
-+      if( rc!=SQLITE_OK ) break;
-     }else{
-       if( !match ){
-         plwInit(&writer, pOut, dlrDocid(pLeft));
-         match = 1;
-       }
-       plwAdd(&writer, plrColumn(&right), plrPosition(&right), 0, 0);
--      plrStep(&left);
--      plrStep(&right);
-+      rc = plrStep(&left);
-+      if( rc!=SQLITE_OK ) break;
-+      rc = plrStep(&right);
-+      if( rc!=SQLITE_OK ) break;
-     }
-   }
- 
-@@ -1470,6 +1574,7 @@ static void posListPhraseMerge(DLReader *pLeft, DLReader *pRight,
- 
-   plrDestroy(&left);
-   plrDestroy(&right);
-+  return rc;
- }
- 
- /* We have two doclists with positions:  pLeft and pRight.
-@@ -1481,7 +1586,7 @@ static void posListPhraseMerge(DLReader *pLeft, DLReader *pRight,
- ** iType controls the type of data written to pOut.  If iType is
- ** DL_POSITIONS, the positions are those from pRight.
- */
--static void docListPhraseMerge(
-+static int docListPhraseMerge(
-   const char *pLeft, int nLeft,
-   const char *pRight, int nRight,
-   DocListType iType,
-@@ -1489,152 +1594,198 @@ static void docListPhraseMerge(
- ){
-   DLReader left, right;
-   DLWriter writer;
-+  int rc;
- 
--  if( nLeft==0 || nRight==0 ) return;
-+  if( nLeft==0 || nRight==0 ) return SQLITE_OK;
- 
-   assert( iType!=DL_POSITIONS_OFFSETS );
- 
--  dlrInit(&left, DL_POSITIONS, pLeft, nLeft);
--  dlrInit(&right, DL_POSITIONS, pRight, nRight);
-+  rc = dlrInit(&left, DL_POSITIONS, pLeft, nLeft);
-+  if( rc!=SQLITE_OK ) return rc;
-+  rc = dlrInit(&right, DL_POSITIONS, pRight, nRight);
-+  if( rc!=SQLITE_OK ){
-+    dlrDestroy(&left);
-+    return rc;
-+  }
-   dlwInit(&writer, iType, pOut);
- 
-   while( !dlrAtEnd(&left) && !dlrAtEnd(&right) ){
-     if( dlrDocid(&left)<dlrDocid(&right) ){
--      dlrStep(&left);
-+      rc = dlrStep(&left);
-+      if( rc!=SQLITE_OK ) break;
-     }else if( dlrDocid(&right)<dlrDocid(&left) ){
--      dlrStep(&right);
-+      rc = dlrStep(&right);
-+      if( rc!=SQLITE_OK ) break;
-     }else{
--      posListPhraseMerge(&left, &right, &writer);
--      dlrStep(&left);
--      dlrStep(&right);
-+      rc = posListPhraseMerge(&left, &right, &writer);
-+      if( rc!=SQLITE_OK ) break;
-+      rc = dlrStep(&left);
-+      if( rc!=SQLITE_OK ) break;
-+      rc = dlrStep(&right);
-+      if( rc!=SQLITE_OK ) break;
-     }
-   }
- 
-   dlrDestroy(&left);
-   dlrDestroy(&right);
-   dlwDestroy(&writer);
-+  return rc;
- }
- 
- /* We have two DL_DOCIDS doclists:  pLeft and pRight.
- ** Write the intersection of these two doclists into pOut as a
- ** DL_DOCIDS doclist.
- */
--static void docListAndMerge(
-+static int docListAndMerge(
-   const char *pLeft, int nLeft,
-   const char *pRight, int nRight,
-   DataBuffer *pOut      /* Write the combined doclist here */
- ){
-   DLReader left, right;
-   DLWriter writer;
-+  int rc;
- 
--  if( nLeft==0 || nRight==0 ) return;
-+  if( nLeft==0 || nRight==0 ) return SQLITE_OK;
- 
--  dlrInit(&left, DL_DOCIDS, pLeft, nLeft);
--  dlrInit(&right, DL_DOCIDS, pRight, nRight);
-+  rc = dlrInit(&left, DL_DOCIDS, pLeft, nLeft);
-+  if( rc!=SQLITE_OK ) return rc;
-+  rc = dlrInit(&right, DL_DOCIDS, pRight, nRight);
-+  if( rc!=SQLITE_OK ){
-+    dlrDestroy(&left);
-+    return rc;
-+  }
-   dlwInit(&writer, DL_DOCIDS, pOut);
- 
-   while( !dlrAtEnd(&left) && !dlrAtEnd(&right) ){
-     if( dlrDocid(&left)<dlrDocid(&right) ){
--      dlrStep(&left);
-+      rc = dlrStep(&left);
-+      if( rc!=SQLITE_OK ) break;
-     }else if( dlrDocid(&right)<dlrDocid(&left) ){
--      dlrStep(&right);
-+      rc = dlrStep(&right);
-+      if( rc!=SQLITE_OK ) break;
-     }else{
-       dlwAdd(&writer, dlrDocid(&left));
--      dlrStep(&left);
--      dlrStep(&right);
-+      rc = dlrStep(&left);
-+      if( rc!=SQLITE_OK ) break;
-+      rc = dlrStep(&right);
-+      if( rc!=SQLITE_OK ) break;
-     }
-   }
- 
-   dlrDestroy(&left);
-   dlrDestroy(&right);
-   dlwDestroy(&writer);
-+  return rc;
- }
- 
- /* We have two DL_DOCIDS doclists:  pLeft and pRight.
- ** Write the union of these two doclists into pOut as a
- ** DL_DOCIDS doclist.
- */
--static void docListOrMerge(
-+static int docListOrMerge(
-   const char *pLeft, int nLeft,
-   const char *pRight, int nRight,
-   DataBuffer *pOut      /* Write the combined doclist here */
- ){
-   DLReader left, right;
-   DLWriter writer;
-+  int rc;
- 
-   if( nLeft==0 ){
-     if( nRight!=0 ) dataBufferAppend(pOut, pRight, nRight);
--    return;
-+    return SQLITE_OK;
-   }
-   if( nRight==0 ){
-     dataBufferAppend(pOut, pLeft, nLeft);
--    return;
-+    return SQLITE_OK;
-   }
- 
--  dlrInit(&left, DL_DOCIDS, pLeft, nLeft);
--  dlrInit(&right, DL_DOCIDS, pRight, nRight);
-+  rc = dlrInit(&left, DL_DOCIDS, pLeft, nLeft);
-+  if( rc!=SQLITE_OK ) return rc;
-+  rc = dlrInit(&right, DL_DOCIDS, pRight, nRight);
-+  if( rc!=SQLITE_OK ){
-+    dlrDestroy(&left);
-+    return rc;
-+  }
-   dlwInit(&writer, DL_DOCIDS, pOut);
- 
-   while( !dlrAtEnd(&left) || !dlrAtEnd(&right) ){
-     if( dlrAtEnd(&right) ){
-       dlwAdd(&writer, dlrDocid(&left));
--      dlrStep(&left);
-+      rc = dlrStep(&left);
-+      if( rc!=SQLITE_OK ) break;
-     }else if( dlrAtEnd(&left) ){
-       dlwAdd(&writer, dlrDocid(&right));
--      dlrStep(&right);
-+      rc = dlrStep(&right);
-+      if( rc!=SQLITE_OK ) break;
-     }else if( dlrDocid(&left)<dlrDocid(&right) ){
-       dlwAdd(&writer, dlrDocid(&left));
--      dlrStep(&left);
-+      rc = dlrStep(&left);
-+      if( rc!=SQLITE_OK ) break;
-     }else if( dlrDocid(&right)<dlrDocid(&left) ){
-       dlwAdd(&writer, dlrDocid(&right));
--      dlrStep(&right);
-+      rc = dlrStep(&right);
-+      if( rc!=SQLITE_OK ) break;
-     }else{
-       dlwAdd(&writer, dlrDocid(&left));
--      dlrStep(&left);
--      dlrStep(&right);
-+      rc = dlrStep(&left);
-+      if( rc!=SQLITE_OK ) break;
-+      rc = dlrStep(&right);
-+      if( rc!=SQLITE_OK ) break;
-     }
-   }
- 
-   dlrDestroy(&left);
-   dlrDestroy(&right);
-   dlwDestroy(&writer);
-+  return rc;
- }
- 
- /* We have two DL_DOCIDS doclists:  pLeft and pRight.
- ** Write into pOut as DL_DOCIDS doclist containing all documents that
- ** occur in pLeft but not in pRight.
- */
--static void docListExceptMerge(
-+static int docListExceptMerge(
-   const char *pLeft, int nLeft,
-   const char *pRight, int nRight,
-   DataBuffer *pOut      /* Write the combined doclist here */
- ){
-   DLReader left, right;
-   DLWriter writer;
-+  int rc;
- 
--  if( nLeft==0 ) return;
-+  if( nLeft==0 ) return SQLITE_OK;
-   if( nRight==0 ){
-     dataBufferAppend(pOut, pLeft, nLeft);
--    return;
-+    return SQLITE_OK;
-   }
- 
--  dlrInit(&left, DL_DOCIDS, pLeft, nLeft);
--  dlrInit(&right, DL_DOCIDS, pRight, nRight);
-+  rc = dlrInit(&left, DL_DOCIDS, pLeft, nLeft);
-+  if( rc!=SQLITE_OK ) return rc;
-+  rc = dlrInit(&right, DL_DOCIDS, pRight, nRight);
-+  if( rc!=SQLITE_OK ){
-+    dlrDestroy(&left);
-+    return rc;
-+  }
-   dlwInit(&writer, DL_DOCIDS, pOut);
- 
-   while( !dlrAtEnd(&left) ){
-     while( !dlrAtEnd(&right) && dlrDocid(&right)<dlrDocid(&left) ){
--      dlrStep(&right);
-+      rc = dlrStep(&right);
-+      if( rc!=SQLITE_OK ) goto err;
-     }
-     if( dlrAtEnd(&right) || dlrDocid(&left)<dlrDocid(&right) ){
-       dlwAdd(&writer, dlrDocid(&left));
-     }
--    dlrStep(&left);
-+    rc = dlrStep(&left);
-+    if( rc!=SQLITE_OK ) break;
-   }
- 
-+err:
-   dlrDestroy(&left);
-   dlrDestroy(&right);
-   dlwDestroy(&writer);
-+  return rc;
- }
- 
- static char *string_dup_n(const char *s, int n){
-@@ -3437,7 +3588,8 @@ static int fulltextNext(sqlite3_vtab_cursor *pCursor){
-       return SQLITE_OK;
-     }
-     rc = sqlite3_bind_int64(c->pStmt, 1, dlrDocid(&c->reader));
--    dlrStep(&c->reader);
-+    if( rc!=SQLITE_OK ) return rc;
-+    rc = dlrStep(&c->reader);
-     if( rc!=SQLITE_OK ) return rc;
-     /* TODO(shess) Handle SQLITE_SCHEMA AND SQLITE_BUSY. */
-     rc = sqlite3_step(c->pStmt);
-@@ -3497,14 +3649,18 @@ static int docListOfTerm(
-       return rc;
-     }
-     dataBufferInit(&new, 0);
--    docListPhraseMerge(left.pData, left.nData, right.pData, right.nData,
--                       i<pQTerm->nPhrase ? DL_POSITIONS : DL_DOCIDS, &new);
-+    rc = docListPhraseMerge(left.pData, left.nData, right.pData, right.nData,
-+                            i<pQTerm->nPhrase ? DL_POSITIONS : DL_DOCIDS, &new);
-     dataBufferDestroy(&left);
-     dataBufferDestroy(&right);
-+    if( rc!=SQLITE_OK ){
-+      dataBufferDestroy(&new);
-+      return rc;
-+    }
-     left = new;
-   }
-   *pResult = left;
--  return SQLITE_OK;
-+  return rc;
- }
- 
- /* Add a new term pTerm[0..nTerm-1] to the query *q.
-@@ -3749,18 +3905,30 @@ static int fulltextQuery(
-         return rc;
-       }
-       dataBufferInit(&new, 0);
--      docListOrMerge(right.pData, right.nData, or.pData, or.nData, &new);
-+      rc = docListOrMerge(right.pData, right.nData, or.pData, or.nData, &new);
-       dataBufferDestroy(&right);
-       dataBufferDestroy(&or);
-+      if( rc!=SQLITE_OK ){
-+        if( i!=nNot ) dataBufferDestroy(&left);
-+        queryClear(pQuery);
-+        dataBufferDestroy(&new);
-+        return rc;
-+      }
-       right = new;
-     }
-     if( i==nNot ){           /* first term processed. */
-       left = right;
-     }else{
-       dataBufferInit(&new, 0);
--      docListAndMerge(left.pData, left.nData, right.pData, right.nData, &new);
-+      rc = docListAndMerge(left.pData, left.nData,
-+                           right.pData, right.nData, &new);
-       dataBufferDestroy(&right);
-       dataBufferDestroy(&left);
-+      if( rc!=SQLITE_OK ){
-+        queryClear(pQuery);
-+        dataBufferDestroy(&new);
-+        return rc;
-+      }
-       left = new;
-     }
-   }
-@@ -3780,9 +3948,15 @@ static int fulltextQuery(
-       return rc;
-     }
-     dataBufferInit(&new, 0);
--    docListExceptMerge(left.pData, left.nData, right.pData, right.nData, &new);
-+    rc = docListExceptMerge(left.pData, left.nData,
-+                            right.pData, right.nData, &new);
-     dataBufferDestroy(&right);
-     dataBufferDestroy(&left);
-+    if( rc!=SQLITE_OK ){
-+      queryClear(pQuery);
-+      dataBufferDestroy(&new);
-+      return rc;
-+    }
-     left = new;
-   }
- 
-@@ -3876,7 +4050,8 @@ static int fulltextFilter(
-       rc = fulltextQuery(v, idxNum-QUERY_FULLTEXT, zQuery, -1, &c->result, &c->q);
-       if( rc!=SQLITE_OK ) return rc;
-       if( c->result.nData!=0 ){
--        dlrInit(&c->reader, DL_DOCIDS, c->result.pData, c->result.nData);
-+        rc = dlrInit(&c->reader, DL_DOCIDS, c->result.pData, c->result.nData);
-+        if( rc!=SQLITE_OK ) return rc;
-       }
-       break;
-     }
-@@ -4377,22 +4552,19 @@ static void interiorReaderDestroy(InteriorReader *pReader){
-   SCRAMBLE(pReader);
- }
- 
--/* TODO(shess) The assertions are great, but what if we're in NDEBUG
--** and the blob is empty or otherwise contains suspect data?
--*/
--static void interiorReaderInit(const char *pData, int nData,
--                               InteriorReader *pReader){
-+static int interiorReaderInit(const char *pData, int nData,
-+                              InteriorReader *pReader){
-   int n, nTerm;
- 
--  /* Require at least the leading flag byte */
-+  /* These conditions are checked and met by the callers. */
-   assert( nData>0 );
-   assert( pData[0]!='\0' );
- 
-   CLEAR(pReader);
- 
-   /* Decode the base blockid, and set the cursor to the first term. */
--  n = getVarint(pData+1, &pReader->iBlockid);
--  assert( 1+n<=nData );
-+  n = getVarintSafe(pData+1, &pReader->iBlockid, nData-1);
-+  if( !n ) return SQLITE_CORRUPT_BKPT;
-   pReader->pData = pData+1+n;
-   pReader->nData = nData-(1+n);
- 
-@@ -4403,17 +4575,18 @@ static void interiorReaderInit(const char *pData, int nData,
-   if( pReader->nData==0 ){
-     dataBufferInit(&pReader->term, 0);
-   }else{
--    n = getVarint32(pReader->pData, &nTerm);
-+    n = getVarint32Safe(pReader->pData, &nTerm, pReader->nData);
-+    if( !n || nTerm<0 || nTerm>pReader->nData-n) return SQLITE_CORRUPT_BKPT;
-     dataBufferInit(&pReader->term, nTerm);
-     dataBufferReplace(&pReader->term, pReader->pData+n, nTerm);
--    assert( n+nTerm<=pReader->nData );
-     pReader->pData += n+nTerm;
-     pReader->nData -= n+nTerm;
-   }
-+  return SQLITE_OK;
- }
- 
- static int interiorReaderAtEnd(InteriorReader *pReader){
--  return pReader->term.nData==0;
-+  return pReader->term.nData<=0;
- }
- 
- static sqlite_int64 interiorReaderCurrentBlockid(InteriorReader *pReader){
-@@ -4430,7 +4603,7 @@ static const char *interiorReaderTerm(InteriorReader *pReader){
- }
- 
- /* Step forward to the next term in the node. */
--static void interiorReaderStep(InteriorReader *pReader){
-+static int interiorReaderStep(InteriorReader *pReader){
-   assert( !interiorReaderAtEnd(pReader) );
- 
-   /* If the last term has been read, signal eof, else construct the
-@@ -4441,18 +4614,26 @@ static void interiorReaderStep(InteriorReader *pReader){
-   }else{
-     int n, nPrefix, nSuffix;
- 
--    n = getVarint32(pReader->pData, &nPrefix);
--    n += getVarint32(pReader->pData+n, &nSuffix);
-+    n = getVarint32Safe(pReader->pData, &nPrefix, pReader->nData);
-+    if( !n ) return SQLITE_CORRUPT_BKPT;
-+    pReader->nData -= n;
-+    pReader->pData += n;
-+    n = getVarint32Safe(pReader->pData, &nSuffix, pReader->nData);
-+    if( !n ) return SQLITE_CORRUPT_BKPT;
-+    pReader->nData -= n;
-+    pReader->pData += n;
-+    if( nSuffix<0 || nSuffix>pReader->nData ) return SQLITE_CORRUPT_BKPT;
-+    if( nPrefix<0 || nPrefix>pReader->term.nData ) return SQLITE_CORRUPT_BKPT;
- 
-     /* Truncate the current term and append suffix data. */
-     pReader->term.nData = nPrefix;
--    dataBufferAppend(&pReader->term, pReader->pData+n, nSuffix);
-+    dataBufferAppend(&pReader->term, pReader->pData, nSuffix);
- 
--    assert( n+nSuffix<=pReader->nData );
--    pReader->pData += n+nSuffix;
--    pReader->nData -= n+nSuffix;
-+    pReader->pData += nSuffix;
-+    pReader->nData -= nSuffix;
-   }
-   pReader->iBlockid++;
-+  return SQLITE_OK;
- }
- 
- /* Compare the current term to pTerm[nTerm], returning strcmp-style
-@@ -4824,7 +5005,8 @@ static int leafWriterStepMerge(fulltext_vtab *v, LeafWriter *pWriter,
-   n = putVarint(c, nData);
-   dataBufferAppend(&pWriter->data, c, n);
- 
--  docListMerge(&pWriter->data, pReaders, nReaders);
-+  rc = docListMerge(&pWriter->data, pReaders, nReaders);
-+  if( rc!= SQLITE_OK ) return rc;
-   ASSERT_VALID_DOCLIST(DL_DEFAULT,
-                        pWriter->data.pData+iDoclistData+n,
-                        pWriter->data.nData-iDoclistData-n, NULL);
-@@ -4934,7 +5116,8 @@ static int leafWriterStep(fulltext_vtab *v, LeafWriter *pWriter,
-   int rc;
-   DLReader reader;
- 
--  dlrInit(&reader, DL_DEFAULT, pData, nData);
-+  rc = dlrInit(&reader, DL_DEFAULT, pData, nData);
-+  if( rc!=SQLITE_OK ) return rc;
-   rc = leafWriterStepMerge(v, pWriter, pTerm, nTerm, &reader, 1);
-   dlrDestroy(&reader);
- 
-@@ -4979,38 +5162,40 @@ static int leafReaderDataBytes(LeafReader *pReader){
- static const char *leafReaderData(LeafReader *pReader){
-   int n, nData;
-   assert( pReader->term.nData>0 );
--  n = getVarint32(pReader->pData, &nData);
-+  n = getVarint32Safe(pReader->pData, &nData, pReader->nData);
-+  if( !n || nData>pReader->nData-n ) return NULL;
-   return pReader->pData+n;
- }
- 
--static void leafReaderInit(const char *pData, int nData,
--                           LeafReader *pReader){
-+static int leafReaderInit(const char *pData, int nData, LeafReader *pReader){
-   int nTerm, n;
- 
-+  /* All callers check this precondition. */
-   assert( nData>0 );
-   assert( pData[0]=='\0' );
- 
-   CLEAR(pReader);
- 
-   /* Read the first term, skipping the header byte. */
--  n = getVarint32(pData+1, &nTerm);
-+  n = getVarint32Safe(pData+1, &nTerm, nData-1);
-+  if( !n || nTerm<0 || nTerm>nData-1-n ) return SQLITE_CORRUPT_BKPT;
-   dataBufferInit(&pReader->term, nTerm);
-   dataBufferReplace(&pReader->term, pData+1+n, nTerm);
- 
-   /* Position after the first term. */
--  assert( 1+n+nTerm<nData );
-   pReader->pData = pData+1+n+nTerm;
-   pReader->nData = nData-1-n-nTerm;
-+  return SQLITE_OK;
- }
- 
- /* Step the reader forward to the next term. */
--static void leafReaderStep(LeafReader *pReader){
-+static int leafReaderStep(LeafReader *pReader){
-   int n, nData, nPrefix, nSuffix;
-   assert( !leafReaderAtEnd(pReader) );
- 
-   /* Skip previous entry's data block. */
--  n = getVarint32(pReader->pData, &nData);
--  assert( n+nData<=pReader->nData );
-+  n = getVarint32Safe(pReader->pData, &nData, pReader->nData);
-+  if( !n || nData<0 || nData>pReader->nData-n ) return SQLITE_CORRUPT_BKPT;
-   pReader->pData += n+nData;
-   pReader->nData -= n+nData;
- 
-@@ -5018,15 +5203,23 @@ static void leafReaderStep(LeafReader *pReader){
-     /* Construct the new term using a prefix from the old term plus a
-     ** suffix from the leaf data.
-     */
--    n = getVarint32(pReader->pData, &nPrefix);
--    n += getVarint32(pReader->pData+n, &nSuffix);
--    assert( n+nSuffix<pReader->nData );
-+    n = getVarint32Safe(pReader->pData, &nPrefix, pReader->nData);
-+    if( !n ) return SQLITE_CORRUPT_BKPT;
-+    pReader->nData -= n;
-+    pReader->pData += n;
-+    n = getVarint32Safe(pReader->pData, &nSuffix, pReader->nData);
-+    if( !n ) return SQLITE_CORRUPT_BKPT;
-+    pReader->nData -= n;
-+    pReader->pData += n;
-+    if( nSuffix<0 || nSuffix>pReader->nData ) return SQLITE_CORRUPT_BKPT;
-+    if( nPrefix<0 || nPrefix>pReader->term.nData ) return SQLITE_CORRUPT_BKPT;
-     pReader->term.nData = nPrefix;
--    dataBufferAppend(&pReader->term, pReader->pData+n, nSuffix);
-+    dataBufferAppend(&pReader->term, pReader->pData, nSuffix);
- 
--    pReader->pData += n+nSuffix;
--    pReader->nData -= n+nSuffix;
-+    pReader->pData += nSuffix;
-+    pReader->nData -= nSuffix;
-   }
-+  return SQLITE_OK;
- }
- 
- /* strcmp-style comparison of pReader's current term against pTerm.
-@@ -5133,14 +5326,19 @@ static int leavesReaderInit(fulltext_vtab *v,
- 
-   dataBufferInit(&pReader->rootData, 0);
-   if( iStartBlockid==0 ){
-+    int rc;
-     /* Corrupt if this can't be a leaf node. */
-     if( pRootData==NULL || nRootData<1 || pRootData[0]!='\0' ){
-       return SQLITE_CORRUPT_BKPT;
-     }
-     /* Entire leaf level fit in root data. */
-     dataBufferReplace(&pReader->rootData, pRootData, nRootData);
--    leafReaderInit(pReader->rootData.pData, pReader->rootData.nData,
--                   &pReader->leafReader);
-+    rc = leafReaderInit(pReader->rootData.pData, pReader->rootData.nData,
-+                        &pReader->leafReader);
-+    if( rc!=SQLITE_OK ){
-+      dataBufferDestroy(&pReader->rootData);
-+      return rc;
-+    }
-   }else{
-     sqlite3_stmt *s;
-     int rc = sql_get_leaf_statement(v, idx, &s);
-@@ -5174,7 +5372,7 @@ static int leavesReaderInit(fulltext_vtab *v,
-       if( pLeafData==NULL || nLeafData<1 || pLeafData[0]!='\0' ){
-         rc = SQLITE_CORRUPT_BKPT;
-       }else{
--        leafReaderInit(pLeafData, nLeafData, &pReader->leafReader);
-+        rc = leafReaderInit(pLeafData, nLeafData, &pReader->leafReader);
-       }
-     }
- 
-@@ -5197,11 +5395,12 @@ static int leavesReaderInit(fulltext_vtab *v,
- ** end of the current leaf, step forward to the next leaf block.
- */
- static int leavesReaderStep(fulltext_vtab *v, LeavesReader *pReader){
-+  int rc;
-   assert( !leavesReaderAtEnd(pReader) );
--  leafReaderStep(&pReader->leafReader);
-+  rc = leafReaderStep(&pReader->leafReader);
-+  if( rc!=SQLITE_OK ) return rc;
- 
-   if( leafReaderAtEnd(&pReader->leafReader) ){
--    int rc;
-     if( pReader->rootData.pData ){
-       pReader->eof = 1;
-       return SQLITE_OK;
-@@ -5216,6 +5415,7 @@ static int leavesReaderStep(fulltext_vtab *v, LeavesReader *pReader){
-     if( sqlite3_column_type(pReader->pStmt, 0)!=SQLITE_BLOB ){
-       return SQLITE_CORRUPT_BKPT;
-     }else{
-+      LeafReader tmp;
-       const char *pLeafData = sqlite3_column_blob(pReader->pStmt, 0);
-       int nLeafData = sqlite3_column_bytes(pReader->pStmt, 0);
- 
-@@ -5224,8 +5424,10 @@ static int leavesReaderStep(fulltext_vtab *v, LeavesReader *pReader){
-         return SQLITE_CORRUPT_BKPT;
-       }
- 
-+      rc = leafReaderInit(pLeafData, nLeafData, &tmp);
-+      if( rc!=SQLITE_OK ) return rc;
-       leafReaderDestroy(&pReader->leafReader);
--      leafReaderInit(pLeafData, nLeafData, &pReader->leafReader);
-+      pReader->leafReader = tmp;
-     }
-   }
-   return SQLITE_OK;
-@@ -5334,13 +5536,26 @@ static int leavesReadersMerge(fulltext_vtab *v,
-   DLReader dlReaders[MERGE_COUNT];
-   const char *pTerm = leavesReaderTerm(pReaders);
-   int i, nTerm = leavesReaderTermBytes(pReaders);
-+  int rc;
- 
-   assert( nReaders<=MERGE_COUNT );
- 
-   for(i=0; i<nReaders; i++){
--    dlrInit(&dlReaders[i], DL_DEFAULT,
--            leavesReaderData(pReaders+i),
--            leavesReaderDataBytes(pReaders+i));
-+    const char *pData = leavesReaderData(pReaders+i);
-+    if( pData==NULL ){
-+      rc = SQLITE_CORRUPT_BKPT;
-+      break;
-+    }
-+    rc = dlrInit(&dlReaders[i], DL_DEFAULT,
-+                 pData,
-+                 leavesReaderDataBytes(pReaders+i));
-+    if( rc!=SQLITE_OK ) break;
-+  }
-+  if( rc!=SQLITE_OK ){
-+    while( i-->0 ){
-+      dlrDestroy(&dlReaders[i]);
-+    }
-+    return rc;
-   }
- 
-   return leafWriterStepMerge(v, pWriter, pTerm, nTerm, dlReaders, nReaders);
-@@ -5444,12 +5659,14 @@ static int segmentMerge(fulltext_vtab *v, int iLevel){
- }
- 
- /* Accumulate the union of *acc and *pData into *acc. */
--static void docListAccumulateUnion(DataBuffer *acc,
--                                   const char *pData, int nData) {
-+static int docListAccumulateUnion(DataBuffer *acc,
-+                                  const char *pData, int nData) {
-   DataBuffer tmp = *acc;
-+  int rc;
-   dataBufferInit(acc, tmp.nData+nData);
--  docListUnion(tmp.pData, tmp.nData, pData, nData, acc);
-+  rc = docListUnion(tmp.pData, tmp.nData, pData, nData, acc);
-   dataBufferDestroy(&tmp);
-+  return rc;
- }
- 
- /* TODO(shess) It might be interesting to explore different merge
-@@ -5491,8 +5708,13 @@ static int loadSegmentLeavesInt(fulltext_vtab *v, LeavesReader *pReader,
-     int c = leafReaderTermCmp(&pReader->leafReader, pTerm, nTerm, isPrefix);
-     if( c>0 ) break;      /* Past any possible matches. */
-     if( c==0 ){
-+      int iBuffer, nData;
-       const char *pData = leavesReaderData(pReader);
--      int iBuffer, nData = leavesReaderDataBytes(pReader);
-+      if( pData==NULL ){
-+        rc = SQLITE_CORRUPT_BKPT;
-+        break;
-+      }
-+      nData = leavesReaderDataBytes(pReader);
- 
-       /* Find the first empty buffer. */
-       for(iBuffer=0; iBuffer<nBuffers; ++iBuffer){
-@@ -5538,11 +5760,13 @@ static int loadSegmentLeavesInt(fulltext_vtab *v, LeavesReader *pReader,
-         ** with pData/nData.
-         */
-         dataBufferSwap(p, pAcc);
--        docListAccumulateUnion(pAcc, pData, nData);
-+        rc = docListAccumulateUnion(pAcc, pData, nData);
-+        if( rc!=SQLITE_OK ) goto err;
- 
-         /* Accumulate remaining doclists into pAcc. */
-         for(++p; p<pAcc; ++p){
--          docListAccumulateUnion(pAcc, p->pData, p->nData);
-+          rc = docListAccumulateUnion(pAcc, p->pData, p->nData);
-+          if( rc!=SQLITE_OK ) goto err;
- 
-           /* dataBufferReset() could allow a large doclist to blow up
-           ** our memory requirements.
-@@ -5567,13 +5791,15 @@ static int loadSegmentLeavesInt(fulltext_vtab *v, LeavesReader *pReader,
-         if( out->nData==0 ){
-           dataBufferSwap(out, &(pBuffers[iBuffer]));
-         }else{
--          docListAccumulateUnion(out, pBuffers[iBuffer].pData,
--                                 pBuffers[iBuffer].nData);
-+          rc = docListAccumulateUnion(out, pBuffers[iBuffer].pData,
-+                                      pBuffers[iBuffer].nData);
-+          if( rc!=SQLITE_OK ) break;
-         }
-       }
-     }
-   }
- 
-+err:
-   while( nBuffers-- ){
-     dataBufferDestroy(&(pBuffers[nBuffers]));
-   }
-@@ -5632,20 +5858,26 @@ static int loadSegmentLeaves(fulltext_vtab *v,
- ** node.  Consider whether breaking symmetry is worthwhile.  I suspect
- ** it is not worthwhile.
- */
--static void getChildrenContaining(const char *pData, int nData,
--                                  const char *pTerm, int nTerm, int isPrefix,
--                                  sqlite_int64 *piStartChild,
--                                  sqlite_int64 *piEndChild){
-+static int getChildrenContaining(const char *pData, int nData,
-+                                 const char *pTerm, int nTerm, int isPrefix,
-+                                 sqlite_int64 *piStartChild,
-+                                 sqlite_int64 *piEndChild){
-   InteriorReader reader;
-+  int rc;
- 
-   assert( nData>1 );
-   assert( *pData!='\0' );
--  interiorReaderInit(pData, nData, &reader);
-+  rc = interiorReaderInit(pData, nData, &reader);
-+  if( rc!=SQLITE_OK ) return rc;
- 
-   /* Scan for the first child which could contain pTerm/nTerm. */
-   while( !interiorReaderAtEnd(&reader) ){
-     if( interiorReaderTermCmp(&reader, pTerm, nTerm, 0)>0 ) break;
--    interiorReaderStep(&reader);
-+    rc = interiorReaderStep(&reader);
-+    if( rc!=SQLITE_OK ){
-+      interiorReaderDestroy(&reader);
-+      return rc;
-+    }
-   }
-   *piStartChild = interiorReaderCurrentBlockid(&reader);
- 
-@@ -5655,7 +5887,11 @@ static void getChildrenContaining(const char *pData, int nData,
-   */
-   while( !interiorReaderAtEnd(&reader) ){
-     if( interiorReaderTermCmp(&reader, pTerm, nTerm, isPrefix)>0 ) break;
--    interiorReaderStep(&reader);
-+    rc = interiorReaderStep(&reader);
-+    if( rc!=SQLITE_OK ){
-+      interiorReaderDestroy(&reader);
-+      return rc;
-+    }
-   }
-   *piEndChild = interiorReaderCurrentBlockid(&reader);
- 
-@@ -5664,6 +5900,7 @@ static void getChildrenContaining(const char *pData, int nData,
-   /* Children must ascend, and if !prefix, both must be the same. */
-   assert( *piEndChild>=*piStartChild );
-   assert( isPrefix || *piStartChild==*piEndChild );
-+  return rc;
- }
- 
- /* Read block at iBlockid and pass it with other params to
-@@ -5709,8 +5946,12 @@ static int loadAndGetChildrenContaining(
-       return SQLITE_CORRUPT_BKPT;
-     }
- 
--    getChildrenContaining(pData, nData, pTerm, nTerm,
--                          isPrefix, piStartChild, piEndChild);
-+    rc = getChildrenContaining(pData, nData, pTerm, nTerm,
-+                               isPrefix, piStartChild, piEndChild);
-+    if( rc!=SQLITE_OK ){
-+      sqlite3_reset(s);
-+      return rc;
-+    }
-   }
- 
-   /* We expect only one row.  We must execute another sqlite3_step()
-@@ -5741,8 +5982,9 @@ static int loadSegmentInt(fulltext_vtab *v, const char *pData, int nData,
-     /* Process pData as an interior node, then loop down the tree
-     ** until we find the set of leaf nodes to scan for the term.
-     */
--    getChildrenContaining(pData, nData, pTerm, nTerm, isPrefix,
--                          &iStartChild, &iEndChild);
-+    rc = getChildrenContaining(pData, nData, pTerm, nTerm, isPrefix,
-+                               &iStartChild, &iEndChild);
-+    if( rc!=SQLITE_OK ) return rc;
-     while( iStartChild>iLeavesEnd ){
-       sqlite_int64 iNextStart, iNextEnd;
-       rc = loadAndGetChildrenContaining(v, iStartChild, pTerm, nTerm, isPrefix,
-@@ -5812,16 +6054,21 @@ static int loadSegment(fulltext_vtab *v, const char *pData, int nData,
-       DataBuffer merged;
-       DLReader readers[2];
- 
--      dlrInit(&readers[0], DL_DEFAULT, out->pData, out->nData);
--      dlrInit(&readers[1], DL_DEFAULT, result.pData, result.nData);
--      dataBufferInit(&merged, out->nData+result.nData);
--      docListMerge(&merged, readers, 2);
--      dataBufferDestroy(out);
--      *out = merged;
--      dlrDestroy(&readers[0]);
--      dlrDestroy(&readers[1]);
-+      rc = dlrInit(&readers[0], DL_DEFAULT, out->pData, out->nData);
-+      if( rc==SQLITE_OK ){
-+        rc = dlrInit(&readers[1], DL_DEFAULT, result.pData, result.nData);
-+        if( rc==SQLITE_OK ){
-+          dataBufferInit(&merged, out->nData+result.nData);
-+          rc = docListMerge(&merged, readers, 2);
-+          dataBufferDestroy(out);
-+          *out = merged;
-+          dlrDestroy(&readers[1]);
-+        }
-+        dlrDestroy(&readers[0]);
-+      }
-     }
-   }
-+
-   dataBufferDestroy(&result);
-   return rc;
- }
-@@ -5862,6 +6109,7 @@ static int termSelect(fulltext_vtab *v, int iColumn,
-     if( rc!=SQLITE_OK ) goto err;
-   }
-   if( rc==SQLITE_DONE ){
-+    rc = SQLITE_OK;
-     if( doclist.nData!=0 ){
-       /* TODO(shess) The old term_select_all() code applied the column
-       ** restrict as we merged segments, leading to smaller buffers.
-@@ -5869,10 +6117,9 @@ static int termSelect(fulltext_vtab *v, int iColumn,
-       ** system is checked in.
-       */
-       if( iColumn==v->nColumn) iColumn = -1;
--      docListTrim(DL_DEFAULT, doclist.pData, doclist.nData,
--                  iColumn, iType, out);
-+      rc = docListTrim(DL_DEFAULT, doclist.pData, doclist.nData,
-+                       iColumn, iType, out);
-     }
--    rc = SQLITE_OK;
-   }
- 
-  err:
-@@ -6218,6 +6465,7 @@ static int optimizeInternal(fulltext_vtab *v,
-                             LeafWriter *pWriter){
-   int i, rc = SQLITE_OK;
-   DataBuffer doclist, merged, tmp;
-+  const char *pData;
- 
-   /* Order the readers. */
-   i = nReaders;
-@@ -6238,14 +6486,21 @@ static int optimizeInternal(fulltext_vtab *v,
-       if( 0!=optLeavesReaderTermCmp(&readers[0], &readers[i]) ) break;
-     }
- 
-+    pData = optLeavesReaderData(&readers[0]);
-+    if( pData==NULL ){
-+      rc = SQLITE_CORRUPT_BKPT;
-+      break;
-+    }
-+
-     /* Special-case for no merge. */
-     if( i==1 ){
-       /* Trim deletions from the doclist. */
-       dataBufferReset(&merged);
--      docListTrim(DL_DEFAULT,
--                  optLeavesReaderData(&readers[0]),
--                  optLeavesReaderDataBytes(&readers[0]),
--                  -1, DL_DEFAULT, &merged);
-+      rc = docListTrim(DL_DEFAULT,
-+                       pData,
-+                       optLeavesReaderDataBytes(&readers[0]),
-+                       -1, DL_DEFAULT, &merged);
-+      if( rc!= SQLITE_OK ) break;
-     }else{
-       DLReader dlReaders[MERGE_COUNT];
-       int iReader, nReaders;
-@@ -6253,9 +6508,10 @@ static int optimizeInternal(fulltext_vtab *v,
-       /* Prime the pipeline with the first reader's doclist.  After
-       ** one pass index 0 will reference the accumulated doclist.
-       */
--      dlrInit(&dlReaders[0], DL_DEFAULT,
--              optLeavesReaderData(&readers[0]),
--              optLeavesReaderDataBytes(&readers[0]));
-+      rc = dlrInit(&dlReaders[0], DL_DEFAULT,
-+                   pData,
-+                   optLeavesReaderDataBytes(&readers[0]));
-+      if( rc!=SQLITE_OK ) break;
-       iReader = 1;
- 
-       assert( iReader<i );  /* Must execute the loop at least once. */
-@@ -6263,24 +6519,35 @@ static int optimizeInternal(fulltext_vtab *v,
-         /* Merge 16 inputs per pass. */
-         for( nReaders=1; iReader<i && nReaders<MERGE_COUNT;
-              iReader++, nReaders++ ){
--          dlrInit(&dlReaders[nReaders], DL_DEFAULT,
--                  optLeavesReaderData(&readers[iReader]),
--                  optLeavesReaderDataBytes(&readers[iReader]));
-+          pData = optLeavesReaderData(&readers[iReader]);
-+          if( pData == NULL ){
-+            rc = SQLITE_CORRUPT_BKPT;
-+            break;
-+          }
-+          rc = dlrInit(&dlReaders[nReaders], DL_DEFAULT,
-+                       pData,
-+                       optLeavesReaderDataBytes(&readers[iReader]));
-+          if( rc != SQLITE_OK ) break;
-         }
- 
-         /* Merge doclists and swap result into accumulator. */
--        dataBufferReset(&merged);
--        docListMerge(&merged, dlReaders, nReaders);
--        tmp = merged;
--        merged = doclist;
--        doclist = tmp;
-+        if( rc==SQLITE_OK ){
-+          dataBufferReset(&merged);
-+          rc = docListMerge(&merged, dlReaders, nReaders);
-+          tmp = merged;
-+          merged = doclist;
-+          doclist = tmp;
-+        }
- 
-         while( nReaders-- > 0 ){
-           dlrDestroy(&dlReaders[nReaders]);
-         }
- 
-+        if( rc!=SQLITE_OK ) goto err;
-+
-         /* Accumulated doclist to reader 0 for next pass. */
--        dlrInit(&dlReaders[0], DL_DEFAULT, doclist.pData, doclist.nData);
-+        rc = dlrInit(&dlReaders[0], DL_DEFAULT, doclist.pData, doclist.nData);
-+        if( rc!=SQLITE_OK ) goto err;
-       }
- 
-       /* Destroy reader that was left in the pipeline. */
-@@ -6288,8 +6555,9 @@ static int optimizeInternal(fulltext_vtab *v,
- 
-       /* Trim deletions from the doclist. */
-       dataBufferReset(&merged);
--      docListTrim(DL_DEFAULT, doclist.pData, doclist.nData,
--                  -1, DL_DEFAULT, &merged);
-+      rc = docListTrim(DL_DEFAULT, doclist.pData, doclist.nData,
-+                       -1, DL_DEFAULT, &merged);
-+      if( rc!=SQLITE_OK ) goto err;
-     }
- 
-     /* Only pass doclists with hits (skip if all hits deleted). */
-@@ -6628,16 +6896,19 @@ static void createDoclistResult(sqlite3_context *pContext,
-                                 const char *pData, int nData){
-   DataBuffer dump;
-   DLReader dlReader;
-+  int rc;
- 
-   assert( pData!=NULL && nData>0 );
- 
-+  rc = dlrInit(&dlReader, DL_DEFAULT, pData, nData);
-+  if( rc!=SQLITE_OK ) return;
-   dataBufferInit(&dump, 0);
--  dlrInit(&dlReader, DL_DEFAULT, pData, nData);
--  for( ; !dlrAtEnd(&dlReader); dlrStep(&dlReader) ){
-+  for( ; rc==SQLITE_OK && !dlrAtEnd(&dlReader); rc = dlrStep(&dlReader) ){
-     char buf[256];
-     PLReader plReader;
- 
--    plrInit(&plReader, &dlReader);
-+    rc = plrInit(&plReader, &dlReader);
-+    if( rc!=SQLITE_OK ) break;
-     if( DL_DEFAULT==DL_DOCIDS || plrAtEnd(&plReader) ){
-       sqlite3_snprintf(sizeof(buf), buf, "[%lld] ", dlrDocid(&dlReader));
-       dataBufferAppend(&dump, buf, strlen(buf));
-@@ -6648,7 +6919,8 @@ static void createDoclistResult(sqlite3_context *pContext,
-                        dlrDocid(&dlReader), iColumn);
-       dataBufferAppend(&dump, buf, strlen(buf));
- 
--      for( ; !plrAtEnd(&plReader); plrStep(&plReader) ){
-+      for( ; !plrAtEnd(&plReader); rc = plrStep(&plReader) ){
-+        if( rc!=SQLITE_OK ) break;
-         if( plrColumn(&plReader)!=iColumn ){
-           iColumn = plrColumn(&plReader);
-           sqlite3_snprintf(sizeof(buf), buf, "] %d[", iColumn);
-@@ -6669,6 +6941,7 @@ static void createDoclistResult(sqlite3_context *pContext,
-         dataBufferAppend(&dump, buf, strlen(buf));
-       }
-       plrDestroy(&plReader);
-+      if( rc!= SQLITE_OK ) break;
- 
-       assert( dump.nData>0 );
-       dump.nData--;                     /* Overwrite trailing space. */
-@@ -6677,6 +6950,10 @@ static void createDoclistResult(sqlite3_context *pContext,
-     }
-   }
-   dlrDestroy(&dlReader);
-+  if( rc!=SQLITE_OK ){
-+    dataBufferDestroy(&dump);
-+    return;
-+  }
- 
-   assert( dump.nData>0 );
-   dump.nData--;                     /* Overwrite trailing space. */
--- 
-2.2.1
-