Index: ext/fts5/fts5_expr.c
==================================================================
--- ext/fts5/fts5_expr.c
+++ ext/fts5/fts5_expr.c
@@ -1465,10 +1465,11 @@
 }
 
 typedef struct TokenCtx TokenCtx;
 struct TokenCtx {
   Fts5ExprPhrase *pPhrase;
+  int rc;
 };
 
 /*
 ** Callback for tokenizing terms used by ParseTerm().
 */
@@ -1483,40 +1484,53 @@
   int rc = SQLITE_OK;
   const int SZALLOC = 8;
   TokenCtx *pCtx = (TokenCtx*)pContext;
   Fts5ExprPhrase *pPhrase = pCtx->pPhrase;
 
+  /* If an error has already occurred, this is a no-op */
+  if( pCtx->rc!=SQLITE_OK ) return pCtx->rc;
+
   assert( pPhrase==0 || pPhrase->nTerm>0 );
   if( pPhrase && (tflags & FTS5_TOKEN_COLOCATED) ){
     Fts5ExprTerm *pSyn;
     int nByte = sizeof(Fts5ExprTerm) + nToken+1;
     pSyn = (Fts5ExprTerm*)sqlite3_malloc(nByte);
-    if( pSyn==0 ) return SQLITE_NOMEM;
-    memset(pSyn, 0, nByte);
-    pSyn->zTerm = (char*)&pSyn[1];
-    memcpy(pSyn->zTerm, pToken, nToken);
-    pSyn->pSynonym = pPhrase->aTerm[pPhrase->nTerm-1].pSynonym;
-    pPhrase->aTerm[pPhrase->nTerm-1].pSynonym = pSyn;
+    if( pSyn==0 ){
+      rc = SQLITE_NOMEM;
+    }else{
+      memset(pSyn, 0, nByte);
+      pSyn->zTerm = (char*)&pSyn[1];
+      memcpy(pSyn->zTerm, pToken, nToken);
+      pSyn->pSynonym = pPhrase->aTerm[pPhrase->nTerm-1].pSynonym;
+      pPhrase->aTerm[pPhrase->nTerm-1].pSynonym = pSyn;
+    }
   }else{
     Fts5ExprTerm *pTerm;
     if( pPhrase==0 || (pPhrase->nTerm % SZALLOC)==0 ){
       Fts5ExprPhrase *pNew;
       int nNew = SZALLOC + (pPhrase ? pPhrase->nTerm : 0);
 
       pNew = (Fts5ExprPhrase*)sqlite3_realloc(pPhrase, 
           sizeof(Fts5ExprPhrase) + sizeof(Fts5ExprTerm) * nNew
       );
-      if( pNew==0 ) return SQLITE_NOMEM;
-      if( pPhrase==0 ) memset(pNew, 0, sizeof(Fts5ExprPhrase));
-      pCtx->pPhrase = pPhrase = pNew;
-      pNew->nTerm = nNew - SZALLOC;
-    }
-
-    pTerm = &pPhrase->aTerm[pPhrase->nTerm++];
-    memset(pTerm, 0, sizeof(Fts5ExprTerm));
-    pTerm->zTerm = sqlite3Fts5Strndup(&rc, pToken, nToken);
-  }
+      if( pNew==0 ){
+        rc = SQLITE_NOMEM;
+      }else{
+        if( pPhrase==0 ) memset(pNew, 0, sizeof(Fts5ExprPhrase));
+        pCtx->pPhrase = pPhrase = pNew;
+        pNew->nTerm = nNew - SZALLOC;
+      }
+    }
+
+    if( rc==SQLITE_OK ){
+      pTerm = &pPhrase->aTerm[pPhrase->nTerm++];
+      memset(pTerm, 0, sizeof(Fts5ExprTerm));
+      pTerm->zTerm = sqlite3Fts5Strndup(&rc, pToken, nToken);
+    }
+  }
+
+  pCtx->rc = rc;
   return rc;
 }
 
 
 /*
@@ -1571,11 +1585,11 @@
     sqlite3Fts5Dequote(z);
     n = strlen(z);
     rc = sqlite3Fts5Tokenize(pConfig, flags, z, n, &sCtx, fts5ParseTokenize);
   }
   sqlite3_free(z);
-  if( rc ){
+  if( rc || (rc = sCtx.rc) ){
     pParse->rc = rc;
     fts5ExprPhraseFree(sCtx.pPhrase);
     sCtx.pPhrase = 0;
   }else if( sCtx.pPhrase ){
 
@@ -1620,11 +1634,11 @@
   Fts5Expr *pNew = 0;             /* Expression to return via *ppNew */
   Fts5ExprPhrase **apPhrase;      /* pNew->apPhrase */
   Fts5ExprNode *pNode;            /* pNew->pRoot */
   Fts5ExprNearset *pNear;         /* pNew->pRoot->pNear */
 
-  TokenCtx sCtx = {0};            /* Context object for fts5ParseTokenize */
+  TokenCtx sCtx = {0,0};          /* Context object for fts5ParseTokenize */
 
 
   pOrig = pExpr->apExprPhrase[iPhrase];
 
   pNew = (Fts5Expr*)sqlite3Fts5MallocZero(&rc, sizeof(Fts5Expr));

Index: ext/fts5/fts5_test_mi.c
==================================================================
--- ext/fts5/fts5_test_mi.c
+++ ext/fts5/fts5_test_mi.c
@@ -350,11 +350,11 @@
   int nVal,                       /* Number of values in apVal[] array */
   sqlite3_value **apVal           /* Array of trailing arguments */
 ){
   const char *zArg;
   Fts5MatchinfoCtx *p;
-  int rc;
+  int rc = SQLITE_OK;
 
   if( nVal>0 ){
     zArg = (const char*)sqlite3_value_text(apVal[0]);
   }else{
     zArg = "pcx";
@@ -361,15 +361,20 @@
   }
 
   p = (Fts5MatchinfoCtx*)pApi->xGetAuxdata(pFts, 0);
   if( p==0 || sqlite3_stricmp(zArg, p->zArg) ){
     p = fts5MatchinfoNew(pApi, pFts, pCtx, zArg);
-    pApi->xSetAuxdata(pFts, p, sqlite3_free);
-    if( p==0 ) return;
+    if( p==0 ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = pApi->xSetAuxdata(pFts, p, sqlite3_free);
+    }
   }
 
-  rc = fts5MatchinfoIter(pApi, pFts, p, fts5MatchinfoLocalCb);
+  if( rc==SQLITE_OK ){
+    rc = fts5MatchinfoIter(pApi, pFts, p, fts5MatchinfoLocalCb);
+  }
   if( rc!=SQLITE_OK ){
     sqlite3_result_error_code(pCtx, rc);
   }else{
     /* No errors has occured, so return a copy of the array of integers. */
     int nByte = p->nRet * sizeof(u32);

Index: ext/fts5/test/fts5_common.tcl
==================================================================
--- ext/fts5/test/fts5_common.tcl
+++ ext/fts5/test/fts5_common.tcl
@@ -292,6 +292,39 @@
 }
 proc NOT {a b} {
   if {[llength $b]>0} { return [list] }
   return $a
 }
+
+#-------------------------------------------------------------------------
+# This command is similar to [split], except that it also provides the
+# start and end offsets of each token. For example:
+#
+#   [fts5_tokenize_split "abc d ef"] -> {abc 0 3 d 4 5 ef 6 8}
+#
+
+proc gobble_whitespace {textvar} {
+  upvar $textvar t
+  regexp {([ ]*)(.*)} $t -> space t
+  return [string length $space]
+}
+
+proc gobble_text {textvar wordvar} {
+  upvar $textvar t
+  upvar $wordvar w
+  regexp {([^ ]*)(.*)} $t -> w t
+  return [string length $w]
+}
+
+proc fts5_tokenize_split {text} {
+  set token ""
+  set ret [list]
+  set iOff [gobble_whitespace text]
+  while {[set nToken [gobble_text text word]]} {
+    lappend ret $word $iOff [expr $iOff+$nToken]
+    incr iOff $nToken
+    incr iOff [gobble_whitespace text]
+  }
+
+  set ret
+}
 

Index: ext/fts5/test/fts5fault6.test
==================================================================
--- ext/fts5/test/fts5fault6.test
+++ ext/fts5/test/fts5fault6.test
@@ -145,8 +145,74 @@
     CREATE VIRTUAL TABLE yu USING fts5(x, tokenize="unicode61 separators abc");
   }
 } -test {
   faultsim_test_result {0 {}}
 }
+
+#-------------------------------------------------------------------------
+# OOM while running a query that includes synonyms and matchinfo().
+#
+proc mit {blob} {
+  set scan(littleEndian) i*
+  set scan(bigEndian) I*
+  binary scan $blob $scan($::tcl_platform(byteOrder)) r
+  return $r
+}
+proc tcl_tokenize {tflags text} {
+  foreach {w iStart iEnd} [fts5_tokenize_split $text] {
+    sqlite3_fts5_token $w $iStart $iEnd
+    if {$tflags=="query" && [string length $w]==1} {
+      for {set i 2} {$i < 7} {incr i} {
+        sqlite3_fts5_token -colo [string repeat $w $i] $iStart $iEnd
+      }
+    }
+  }
+}
+proc tcl_create {args} { return "tcl_tokenize" }
+reset_db
+sqlite3_fts5_create_tokenizer db tcl tcl_create
+db func mit mit
+sqlite3_fts5_register_matchinfo db
+do_test 5.0 {
+  execsql { CREATE VIRTUAL TABLE t1 USING fts5(a, tokenize=tcl) }
+  foreach {rowid text} {
+    1 {aaaa cc b aaaaa cc aa} 
+    2 {aa aa bb a bbb}
+    3 {bb aaaaa aaaaa b aaaa aaaaa}
+    4 {aa a b aaaa aa}
+    5 {aa b ccc aaaaa cc}
+    6 {aa aaaaa bbbb cc aaa}
+    7 {aaaaa aa aa ccccc bb}
+    8 {ccc bbbbb ccccc bbb c}
+    9 {cccccc bbbb a aaa cccc c}
+  } {
+    execsql { INSERT INTO t1(rowid, a) VALUES($rowid, $text) }
+  }
+} {}
+
+set res [list {*}{
+  1 {3 24 8 2 12 6}
+  5 {2 24 8 2 12 6}
+  6 {3 24 8 1 12 6}
+  7 {3 24 8 1 12 6}
+  9 {2 24 8 3 12 6}
+}]
+do_execsql_test 5.1 {
+  SELECT rowid, mit(matchinfo(t1, 'x')) FROM t1 WHERE t1 MATCH 'a AND c'
+} $res
+
+faultsim_save_and_close
+do_faultsim_test 5.2 -faults oom* -prep {
+  faultsim_restore_and_reopen
+  sqlite3_fts5_create_tokenizer db tcl tcl_create
+  sqlite3_fts5_register_matchinfo db
+  db func mit mit
+} -body {
+  db eval { 
+    SELECT rowid, mit(matchinfo(t1, 'x')) FROM t1 WHERE t1 MATCH 'a AND c'
+  }
+} -test {
+  faultsim_test_result [list 0 $::res]
+}
 
 finish_test
 

Index: ext/fts5/test/fts5synonym.test
==================================================================
--- ext/fts5/test/fts5synonym.test
+++ ext/fts5/test/fts5synonym.test
@@ -38,38 +38,12 @@
     foreach x $S {if {$x!=$s} {lappend o $x}}
     set ::syn($s) $o
   }
 }
 
-proc gobble_whitespace {textvar} {
-  upvar $textvar t
-  regexp {([ ]*)(.*)} $t -> space t
-  return [string length $space]
-}
-
-proc gobble_text {textvar wordvar} {
-  upvar $textvar t
-  upvar $wordvar w
-  regexp {([^ ]*)(.*)} $t -> w t
-  return [string length $w]
-}
-
-proc do_tokenize_split {text} {
-  set token ""
-  set ret [list]
-  set iOff [gobble_whitespace text]
-  while {[set nToken [gobble_text text word]]} {
-    lappend ret $word $iOff [expr $iOff+$nToken]
-    incr iOff $nToken
-    incr iOff [gobble_whitespace text]
-  }
-
-  set ret
-}
-
 proc tcl_tokenize {tflags text} {
-  foreach {w iStart iEnd} [do_tokenize_split $text] {
+  foreach {w iStart iEnd} [fts5_tokenize_split $text] {
     sqlite3_fts5_token $w $iStart $iEnd
   }
 }
 
 proc tcl_create {args} {
@@ -93,11 +67,11 @@
 # Test a tokenizer that supports synonyms by adding extra entries to the
 # FTS index.
 #
 
 proc tcl_tokenize {tflags text} {
-  foreach {w iStart iEnd} [do_tokenize_split $text] {
+  foreach {w iStart iEnd} [fts5_tokenize_split $text] {
     sqlite3_fts5_token $w $iStart $iEnd
     if {$tflags=="document" && [info exists ::syn($w)]} {
       foreach s $::syn($w) {
         sqlite3_fts5_token -colo $s $iStart $iEnd
       }
@@ -135,11 +109,11 @@
 #
 reset_db
 sqlite3_fts5_create_tokenizer db tcl tcl_create
 proc tcl_tokenize {tflags text} {
   set bColo 1
-  foreach {w iStart iEnd} [do_tokenize_split $text] {
+  foreach {w iStart iEnd} [fts5_tokenize_split $text] {
     if {$bColo} {
       sqlite3_fts5_token -colo $w $iStart $iEnd
       set bColo 0
     } {
       sqlite3_fts5_token $w $iStart $iEnd
@@ -158,11 +132,11 @@
 do_execsql_test 3.1.1 {
   INSERT INTO ft(ft) VALUES('integrity-check');
 } {}
 
 proc tcl_tokenize {tflags text} {
-  foreach {w iStart iEnd} [do_tokenize_split $text] {
+  foreach {w iStart iEnd} [fts5_tokenize_split $text] {
     sqlite3_fts5_token $w $iStart $iEnd
   }
 }
 
 do_execsql_test 3.1.2 {
@@ -170,11 +144,11 @@
 } {1}
 
 reset_db
 sqlite3_fts5_create_tokenizer db tcl tcl_create
 proc tcl_tokenize {tflags text} {
-  foreach {w iStart iEnd} [do_tokenize_split $text] {
+  foreach {w iStart iEnd} [fts5_tokenize_split $text] {
     sqlite3_fts5_token $w $iStart $iEnd
     sqlite3_fts5_token -colo $w $iStart $iEnd
   }
 }
 do_execsql_test 3.2.0 {
@@ -205,11 +179,11 @@
 # Check that expressions with synonyms can be parsed and executed.
 #
 reset_db
 sqlite3_fts5_create_tokenizer db tcl tcl_create
 proc tcl_tokenize {tflags text} {
-  foreach {w iStart iEnd} [do_tokenize_split $text] {
+  foreach {w iStart iEnd} [fts5_tokenize_split $text] {
     sqlite3_fts5_token $w $iStart $iEnd
     if {$tflags=="query" && [info exists ::syn($w)]} {
       foreach s $::syn($w) {
         sqlite3_fts5_token -colo $s $iStart $iEnd
       }
@@ -328,11 +302,11 @@
 # Test terms with more than 4 synonyms.
 #
 reset_db
 sqlite3_fts5_create_tokenizer db tcl tcl_create
 proc tcl_tokenize {tflags text} {
-  foreach {w iStart iEnd} [do_tokenize_split $text] {
+  foreach {w iStart iEnd} [fts5_tokenize_split $text] {
     sqlite3_fts5_token $w $iStart $iEnd
     if {$tflags=="query" && [string length $w]==1} {
       for {set i 2} {$i<=10} {incr i} {
         sqlite3_fts5_token -colo [string repeat $w $i] $iStart $iEnd
       }