Index: tool/lemon.c
==================================================================
--- tool/lemon.c
+++ tool/lemon.c
@@ -411,10 +411,11 @@
   char *filename;          /* Name of the input file */
   char *outname;           /* Name of the current output file */
   char *tokenprefix;       /* A prefix added to token names in the .h file */
   int nconflict;           /* Number of parsing conflicts */
   int nactiontab;          /* Number of entries in the yy_action[] table */
+  int nlookaheadtab;       /* Number of entries in yy_lookahead[] */
   int tablesize;           /* Total table size of all tables in bytes */
   int basisflag;           /* Print only basis configurations */
   int has_fallback;        /* True if any %fallback is seen in the grammar */
   int nolinenosflag;       /* True if #line statements should not be printed */
   char *argv0;             /* Name of the program */
@@ -587,14 +588,16 @@
   int mnLookahead;             /* Minimum aLookahead[].lookahead */
   int mnAction;                /* Action associated with mnLookahead */
   int mxLookahead;             /* Maximum aLookahead[].lookahead */
   int nLookahead;              /* Used slots in aLookahead[] */
   int nLookaheadAlloc;         /* Slots allocated in aLookahead[] */
+  int nterminal;               /* Number of terminal symbols */
+  int nsymbol;                 /* total number of symbols */
 };
 
 /* Return the number of entries in the yy_action table */
-#define acttab_size(X) ((X)->nAction)
+#define acttab_lookahead_size(X) ((X)->nAction)
 
 /* The value for the N-th entry in yy_action */
 #define acttab_yyaction(X,N)  ((X)->aAction[N].action)
 
 /* The value for the N-th entry in yy_lookahead */
@@ -606,17 +609,19 @@
   free( p->aLookahead );
   free( p );
 }
 
 /* Allocate a new acttab structure */
-acttab *acttab_alloc(void){
+acttab *acttab_alloc(int nsymbol, int nterminal){
   acttab *p = (acttab *) calloc( 1, sizeof(*p) );
   if( p==0 ){
     fprintf(stderr,"Unable to allocate memory for a new acttab.");
     exit(1);
   }
   memset(p, 0, sizeof(*p));
+  p->nsymbol = nsymbol;
+  p->nterminal = nterminal;
   return p;
 }
 
 /* Add a new action to the current transaction set.
 **
@@ -653,20 +658,28 @@
 ** Add the transaction set built up with prior calls to acttab_action()
 ** into the current action table.  Then reset the transaction set back
 ** to an empty set in preparation for a new round of acttab_action() calls.
 **
 ** Return the offset into the action table of the new transaction.
+**
+** If the makeItSafe parameter is true, then the offset is chosen so that
+** it is impossible to overread the yy_lookaside[] table regardless of
+** the lookaside token.  This is done for the terminal symbols, as they
+** come from external inputs and can contain syntax errors.  When makeItSafe
+** is false, there is more flexibility in selecting offsets, resulting in
+** a smaller table.  For non-terminal symbols, which are never syntax errors,
+** makeItSafe can be false.
 */
-int acttab_insert(acttab *p){
-  int i, j, k, n;
+int acttab_insert(acttab *p, int makeItSafe){
+  int i, j, k, n, end;
   assert( p->nLookahead>0 );
 
   /* Make sure we have enough space to hold the expanded action table
   ** in the worst case.  The worst case occurs if the transaction set
   ** must be appended to the current action table
   */
-  n = p->mxLookahead + 1;
+  n = p->nsymbol + 1;
   if( p->nAction + n >= p->nActionAlloc ){
     int oldAlloc = p->nActionAlloc;
     p->nActionAlloc = p->nAction + n + p->nActionAlloc + 20;
     p->aAction = (struct lookahead_action *) realloc( p->aAction,
                           sizeof(p->aAction[0])*p->nActionAlloc);
@@ -684,11 +697,12 @@
   ** duplicate of the current transaction set.  Fall out of the loop
   ** if and when the duplicate is found.
   **
   ** i is the index in p->aAction[] where p->mnLookahead is inserted.
   */
-  for(i=p->nAction-1; i>=0; i--){
+  end = makeItSafe ? p->mnLookahead : 0;
+  for(i=p->nAction-1; i>=end; i--){
     if( p->aAction[i].lookahead==p->mnLookahead ){
       /* All lookaheads and actions in the aLookahead[] transaction
       ** must match against the candidate aAction[i] entry. */
       if( p->aAction[i].action!=p->mnAction ) continue;
       for(j=0; j<p->nLookahead; j++){
@@ -714,16 +728,17 @@
 
   /* If no existing offsets exactly match the current transaction, find an
   ** an empty offset in the aAction[] table in which we can add the
   ** aLookahead[] transaction.
   */
-  if( i<0 ){
+  if( i<end ){
     /* Look for holes in the aAction[] table that fit the current
     ** aLookahead[] transaction.  Leave i set to the offset of the hole.
     ** If no holes are found, i is left at p->nAction, which means the
     ** transaction will be appended. */
-    for(i=0; i<p->nActionAlloc - p->mxLookahead; i++){
+    i = makeItSafe ? p->mnLookahead : 0;
+    for(; i<p->nActionAlloc - p->mxLookahead; i++){
       if( p->aAction[i].lookahead<0 ){
         for(j=0; j<p->nLookahead; j++){
           k = p->aLookahead[j].lookahead - p->mnLookahead + i;
           if( k<0 ) break;
           if( p->aAction[k].lookahead>=0 ) break;
@@ -737,21 +752,39 @@
         }
       }
     }
   }
   /* Insert transaction set at index i. */
+#if 0
+  printf("Acttab:");
+  for(j=0; j<p->nLookahead; j++){
+    printf(" %d", p->aLookahead[j].lookahead);
+  }
+  printf(" inserted at %d\n", i);
+#endif
   for(j=0; j<p->nLookahead; j++){
     k = p->aLookahead[j].lookahead - p->mnLookahead + i;
     p->aAction[k] = p->aLookahead[j];
     if( k>=p->nAction ) p->nAction = k+1;
   }
+  if( makeItSafe && i+p->nterminal>p->nAction ) p->nAction = i+p->nterminal;
   p->nLookahead = 0;
 
   /* Return the offset that is added to the lookahead in order to get the
   ** index into yy_action of the action */
   return i - p->mnLookahead;
 }
+
+/*
+** Return the size of the action table without the trailing syntax error
+** entries.
+*/
+int acttab_action_size(acttab *p){
+  int n = p->nAction;
+  while( n>0 && p->aAction[n-1].lookahead<0 ){ n--; }
+  return n;
+}
 
 /********************** From the file "build.c" *****************************/
 /*
 ** Routines to construction the finite state machine for the LEMON
 ** parser generator.
@@ -1722,10 +1755,11 @@
     stats_line("total symbols", lem.nsymbol);
     stats_line("rules", lem.nrule);
     stats_line("states", lem.nxstate);
     stats_line("conflicts", lem.nconflict);
     stats_line("action table entries", lem.nactiontab);
+    stats_line("lookahead table entries", lem.nlookaheadtab);
     stats_line("total table size (bytes)", lem.tablesize);
   }
   if( lem.nconflict > 0 ){
     fprintf(stderr,"%d parsing conflicts.\n",lem.nconflict);
   }
@@ -4165,11 +4199,11 @@
   mxNtOfst = mnNtOfst = 0;
   /* In an effort to minimize the action table size, use the heuristic
   ** of placing the largest action sets first */
   for(i=0; i<lemp->nxstate*2; i++) ax[i].iOrder = i;
   qsort(ax, lemp->nxstate*2, sizeof(ax[0]), axset_compare);
-  pActtab = acttab_alloc();
+  pActtab = acttab_alloc(lemp->nsymbol, lemp->nterminal);
   for(i=0; i<lemp->nxstate*2 && ax[i].nAction>0; i++){
     stp = ax[i].stp;
     if( ax[i].isTkn ){
       for(ap=stp->ap; ap; ap=ap->next){
         int action;
@@ -4176,11 +4210,11 @@
         if( ap->sp->index>=lemp->nterminal ) continue;
         action = compute_action(lemp, ap);
         if( action<0 ) continue;
         acttab_action(pActtab, ap->sp->index, action);
       }
-      stp->iTknOfst = acttab_insert(pActtab);
+      stp->iTknOfst = acttab_insert(pActtab, 1);
       if( stp->iTknOfst<mnTknOfst ) mnTknOfst = stp->iTknOfst;
       if( stp->iTknOfst>mxTknOfst ) mxTknOfst = stp->iTknOfst;
     }else{
       for(ap=stp->ap; ap; ap=ap->next){
         int action;
@@ -4188,11 +4222,11 @@
         if( ap->sp->index==lemp->nsymbol ) continue;
         action = compute_action(lemp, ap);
         if( action<0 ) continue;
         acttab_action(pActtab, ap->sp->index, action);
       }
-      stp->iNtOfst = acttab_insert(pActtab);
+      stp->iNtOfst = acttab_insert(pActtab, 0);
       if( stp->iNtOfst<mnNtOfst ) mnNtOfst = stp->iNtOfst;
       if( stp->iNtOfst>mxNtOfst ) mxNtOfst = stp->iNtOfst;
     }
 #if 0  /* Uncomment for a trace of how the yy_action[] table fills out */
     { int jj, nn;
@@ -4247,11 +4281,11 @@
   **                     shifting non-terminals after a reduce.
   **  yy_default[]       Default action for each state.
   */
 
   /* Output the yy_action table */
-  lemp->nactiontab = n = acttab_size(pActtab);
+  lemp->nactiontab = n = acttab_action_size(pActtab);
   lemp->tablesize += n*szActionType;
   fprintf(out,"#define YY_ACTTAB_COUNT (%d)\n", n); lineno++;
   fprintf(out,"static const YYACTIONTYPE yy_action[] = {\n"); lineno++;
   for(i=j=0; i<n; i++){
     int action = acttab_yyaction(pActtab, i);
@@ -4266,10 +4300,11 @@
     }
   }
   fprintf(out, "};\n"); lineno++;
 
   /* Output the yy_lookahead table */
+  lemp->nlookaheadtab = n = acttab_lookahead_size(pActtab);
   lemp->tablesize += n*szCodeType;
   fprintf(out,"static const YYCODETYPE yy_lookahead[] = {\n"); lineno++;
   for(i=j=0; i<n; i++){
     int la = acttab_yylookahead(pActtab, i);
     if( la<0 ) la = lemp->nsymbol;
@@ -4285,11 +4320,10 @@
   fprintf(out, "};\n"); lineno++;
 
   /* Output the yy_shift_ofst[] table */
   n = lemp->nxstate;
   while( n>0 && lemp->sorted[n-1]->iTknOfst==NO_OFFSET ) n--;
-  fprintf(out, "#define YY_SHIFT_USE_DFLT (%d)\n", lemp->nactiontab); lineno++;
   fprintf(out, "#define YY_SHIFT_COUNT    (%d)\n", n-1); lineno++;
   fprintf(out, "#define YY_SHIFT_MIN      (%d)\n", mnTknOfst); lineno++;
   fprintf(out, "#define YY_SHIFT_MAX      (%d)\n", mxTknOfst); lineno++;
   fprintf(out, "static const %s yy_shift_ofst[] = {\n",
        minimum_size_type(mnTknOfst, lemp->nterminal+lemp->nactiontab, &sz));
@@ -4310,11 +4344,10 @@
     }
   }
   fprintf(out, "};\n"); lineno++;
 
   /* Output the yy_reduce_ofst[] table */
-  fprintf(out, "#define YY_REDUCE_USE_DFLT (%d)\n", mnNtOfst-1); lineno++;
   n = lemp->nxstate;
   while( n>0 && lemp->sorted[n-1]->iNtOfst==NO_OFFSET ) n--;
   fprintf(out, "#define YY_REDUCE_COUNT (%d)\n", n-1); lineno++;
   fprintf(out, "#define YY_REDUCE_MIN   (%d)\n", mnNtOfst); lineno++;
   fprintf(out, "#define YY_REDUCE_MAX   (%d)\n", mxNtOfst); lineno++;
@@ -4380,14 +4413,12 @@
 
   /* Generate a table containing the symbolic name of every symbol
   */
   for(i=0; i<lemp->nsymbol; i++){
     lemon_sprintf(line,"\"%s\",",lemp->symbols[i]->name);
-    fprintf(out,"  %-15s",line);
-    if( (i&3)==3 ){ fprintf(out,"\n"); lineno++; }
+    fprintf(out,"  /* %4d */ \"%s\",\n",i, lemp->symbols[i]->name); lineno++;
   }
-  if( (i&3)!=0 ){ fprintf(out,"\n"); lineno++; }
   tplt_xfer(lemp->name,in,out,&lineno);
 
   /* Generate a table containing a text string that describes every
   ** rule in the rule set of the grammar.  This information is used
   ** when tracing REDUCE actions.

Index: tool/lempar.c
==================================================================
--- tool/lempar.c
+++ tool/lempar.c
@@ -129,23 +129,17 @@
 ** Given state S and lookahead X, the action is computed as either:
 **
 **    (A)   N = yy_action[ yy_shift_ofst[S] + X ]
 **    (B)   N = yy_default[S]
 **
-** The (A) formula is preferred.  The B formula is used instead if:
-**    (1)  The yy_shift_ofst[S]+X value is out of range, or
-**    (2)  yy_lookahead[yy_shift_ofst[S]+X] is not equal to X, or
-**    (3)  yy_shift_ofst[S] equal YY_SHIFT_USE_DFLT.
-** (Implementation note: YY_SHIFT_USE_DFLT is chosen so that
-** YY_SHIFT_USE_DFLT+X will be out of range for all possible lookaheads X.
-** Hence only tests (1) and (2) need to be evaluated.)
+** The (A) formula is preferred.  The B formula is used instead if
+** yy_lookahead[yy_shift_ofst[S]+X] is not equal to X.
 **
 ** The formulas above are for computing the action when the lookahead is
 ** a terminal symbol.  If the lookahead is a non-terminal (as occurs after
 ** a reduce action) then the yy_reduce_ofst[] array is used in place of
-** the yy_shift_ofst[] array and YY_REDUCE_USE_DFLT is used in place of
-** YY_SHIFT_USE_DFLT.
+** the yy_shift_ofst[] array.
 **
 ** The following are the tables generated in this section:
 **
 **  yy_action[]        A single table containing all actions.
 **  yy_lookahead[]     A table containing the lookahead for each entry in
@@ -476,11 +470,12 @@
   assert( stateno <= YY_SHIFT_COUNT );
   do{
     i = yy_shift_ofst[stateno];
     assert( iLookAhead!=YYNOCODE );
     i += iLookAhead;
-    if( i<0 || i>=YY_ACTTAB_COUNT || yy_lookahead[i]!=iLookAhead ){
+    assert( i>=0 && i<sizeof(yy_lookahead)/sizeof(yy_lookahead[0]) );
+    if( yy_lookahead[i]!=iLookAhead ){
 #ifdef YYFALLBACK
       YYCODETYPE iFallback;            /* Fallback token */
       if( iLookAhead<sizeof(yyFallback)/sizeof(yyFallback[0])
              && (iFallback = yyFallback[iLookAhead])!=0 ){
 #ifndef NDEBUG
@@ -539,11 +534,10 @@
   }
 #else
   assert( stateno<=YY_REDUCE_COUNT );
 #endif
   i = yy_reduce_ofst[stateno];
-  assert( i!=YY_REDUCE_USE_DFLT );
   assert( iLookAhead!=YYNOCODE );
   i += iLookAhead;
 #ifdef YYERRORSYMBOL
   if( i<0 || i>=YY_ACTTAB_COUNT || yy_lookahead[i]!=iLookAhead ){
     return yy_default[stateno];