build: be sure to include config.h first in the generated parser

[bison.git] / src / lalr.c

diff --git a/src/lalr.c b/src/lalr.c
index b66e9c3f10a68be25c32d4abea5718df706025c9..d99f960fbf903fdad47f62580fb79695c829ffe1 100644 (file)
--- a/src/lalr.c
+++ b/src/lalr.c
@@ -1,35 +1,32 @@
-/* Compute look-ahead criteria for Bison.
+/* Compute lookahead criteria for Bison.

 
 

-   Copyright (C) 1984, 1986, 1989, 2000, 2001, 2002, 2003, 2004
-   Free Software Foundation, Inc.
+   Copyright (C) 1984, 1986, 1989, 2000-2013 Free Software Foundation,
+   Inc.

 
    This file is part of Bison, the GNU Compiler Compiler.
 
 
    This file is part of Bison, the GNU Compiler Compiler.
 

-   Bison is free software; you can redistribute it and/or modify
+   This program is free software: you can redistribute it and/or modify

    it under the terms of the GNU General Public License as published by
    it under the terms of the GNU General Public License as published by

-   the Free Software Foundation; either version 2, or (at your option)
-   any later version.
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.

 
 

-   Bison is distributed in the hope that it will be useful,
+   This program is distributed in the hope that it will be useful,

    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License

-   along with Bison; see the file COPYING.  If not, write to
-   the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
-   Boston, MA 02111-1307, USA.  */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

 
 
 
 

-/* Compute how to make the finite state machine deterministic; find
-   which rules need look-ahead in each state, and which look-ahead
+/* Find which rules need lookahead in each state, and which lookahead

    tokens they accept.  */
 
    tokens they accept.  */
 

+#include <config.h>

 #include "system.h"
 
 #include <bitset.h>
 #include <bitsetv.h>
 #include "system.h"
 
 #include <bitset.h>
 #include <bitsetv.h>

-#include <quotearg.h>

 
 #include "LR0.h"
 #include "complain.h"
 
 #include "LR0.h"
 #include "complain.h"


@@ -37,15 +34,17 @@
 #include "getargs.h"
 #include "gram.h"
 #include "lalr.h"
 #include "getargs.h"
 #include "gram.h"
 #include "lalr.h"

+#include "muscle-tab.h"

 #include "nullable.h"
 #include "reader.h"
 #include "relation.h"
 #include "symtab.h"
 
 #include "nullable.h"
 #include "reader.h"
 #include "relation.h"
 #include "symtab.h"
 

-goto_number *goto_map = NULL;
-static goto_number ngotos = 0;
-state_number *from_state = NULL;
-state_number *to_state = NULL;
+goto_number *goto_map;
+goto_number ngotos;
+state_number *from_state;
+state_number *to_state;
+bitsetv goto_follows = NULL;

 
 /* Linked list of goto numbers.  */
 typedef struct goto_list
 
 /* Linked list of goto numbers.  */
 typedef struct goto_list


@@ -55,7 +54,7 @@ typedef struct goto_list
 } goto_list;
 
 
 } goto_list;
 
 

-/* LA is a LR by NTOKENS matrix of bits.  LA[l, i] is 1 if the rule
+/* LA is an NLA by NTOKENS matrix of bits.  LA[l, i] is 1 if the rule

    LArule[l] is applicable in the appropriate state when the next
    token is symbol i.  If LA[l, i] and LA[l, j] are both 1 for i != j,
    it is a conflict.  */
    LArule[l] is applicable in the appropriate state when the next
    token is symbol i.  If LA[l, i] and LA[l, j] are both 1 for i != j,
    it is a conflict.  */


@@ -64,24 +63,20 @@ static bitsetv LA = NULL;
 size_t nLA;
 
 
 size_t nLA;
 
 

-/* And for the famous F variable, which name is so descriptive that a
-   comment is hardly needed.  <grin>.  */
-static bitsetv F = NULL;
-

 static goto_number **includes;
 static goto_list **lookback;
 
 
 
 
 static goto_number **includes;
 static goto_list **lookback;
 
 
 
 

-static void
+void

 set_goto_map (void)
 {
   state_number s;
   goto_number *temp_map;
 
 set_goto_map (void)
 {
   state_number s;
   goto_number *temp_map;
 

-  CALLOC (goto_map, nvars + 1);
-  CALLOC (temp_map, nvars + 1);
+  goto_map = xcalloc (nvars + 1, sizeof *goto_map);
+  temp_map = xnmalloc (nvars + 1, sizeof *temp_map);

 
   ngotos = 0;
   for (s = 0; s < nstates; ++s)
 
   ngotos = 0;
   for (s = 0; s < nstates; ++s)


@@ -89,21 +84,23 @@ set_goto_map (void)
       transitions *sp = states[s]->transitions;
       int i;
       for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)
       transitions *sp = states[s]->transitions;
       int i;
       for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)

-       {
-         if (ngotos >= GOTO_NUMBER_MAXIMUM)
-           abort ();
-         ngotos++;
-         goto_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
-       }
+        {
+          ngotos++;
+
+          /* Abort if (ngotos + 1) would overflow.  */
+          aver (ngotos != GOTO_NUMBER_MAXIMUM);
+
+          goto_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
+        }

     }
 
   {
     }
 
   {

-    int k = 0;
+    goto_number k = 0;

     int i;
     for (i = ntokens; i < nsyms; i++)
       {
     int i;
     for (i = ntokens; i < nsyms; i++)
       {

-       temp_map[i - ntokens] = k;
-       k += goto_map[i - ntokens];
+        temp_map[i - ntokens] = k;
+        k += goto_map[i - ntokens];

       }
 
     for (i = ntokens; i < nsyms; i++)
       }
 
     for (i = ntokens; i < nsyms; i++)


@@ -113,36 +110,31 @@ set_goto_map (void)
     temp_map[nsyms - ntokens] = ngotos;
   }
 
     temp_map[nsyms - ntokens] = ngotos;
   }
 

-  CALLOC (from_state, ngotos);
-  CALLOC (to_state, ngotos);
+  from_state = xcalloc (ngotos, sizeof *from_state);
+  to_state = xcalloc (ngotos, sizeof *to_state);

 
   for (s = 0; s < nstates; ++s)
     {
       transitions *sp = states[s]->transitions;
       int i;
       for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)
 
   for (s = 0; s < nstates; ++s)
     {
       transitions *sp = states[s]->transitions;
       int i;
       for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)

-       {
-         int k = temp_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
-         from_state[k] = s;
-         to_state[k] = sp->states[i]->number;
-       }
+        {
+          goto_number k = temp_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
+          from_state[k] = s;
+          to_state[k] = sp->states[i]->number;
+        }

     }
 
     }
 

-  XFREE (temp_map);
+  free (temp_map);

 }
 
 
 }
 
 

-
-/*----------------------------------------------------------.
-| Map a state/symbol pair into its numeric representation.  |
-`----------------------------------------------------------*/
-
-static int
+goto_number

 map_goto (state_number s0, symbol_number sym)
 {
 map_goto (state_number s0, symbol_number sym)
 {

-  int high;
-  int low;
-  int middle;
+  goto_number high;
+  goto_number low;
+  goto_number middle;

   state_number s;
 
   low = goto_map[sym - ntokens];
   state_number s;
 
   low = goto_map[sym - ntokens];


@@ -150,16 +142,15 @@ map_goto (state_number s0, symbol_number sym)
 
   for (;;)
     {
 
   for (;;)
     {

-      if (high < low)
-       abort ();
+      aver (low <= high);

       middle = (low + high) / 2;
       s = from_state[middle];
       if (s == s0)
       middle = (low + high) / 2;
       s = from_state[middle];
       if (s == s0)

-       return middle;
+        return middle;

       else if (s < s0)
       else if (s < s0)

-       low = middle + 1;
+        low = middle + 1;

       else
       else

-       high = middle - 1;
+        high = middle - 1;

     }
 }
 
     }
 }
 


@@ -167,13 +158,13 @@ map_goto (state_number s0, symbol_number sym)
 static void
 initialize_F (void)
 {
 static void
 initialize_F (void)
 {

-  goto_number **reads = CALLOC (reads, ngotos);
-  goto_number *edge = CALLOC (edge, ngotos + 1);
-  int nedges = 0;
+  goto_number **reads = xnmalloc (ngotos, sizeof *reads);
+  goto_number *edge = xnmalloc (ngotos + 1, sizeof *edge);
+  goto_number nedges = 0;

 
 

-  int i;
+  goto_number i;

 
 

-  F = bitsetv_create (ngotos, ntokens, BITSET_FIXED);
+  goto_follows = bitsetv_create (ngotos, ntokens, BITSET_FIXED);

 
   for (i = 0; i < ngotos; i++)
     {
 
   for (i = 0; i < ngotos; i++)
     {


@@ -182,42 +173,44 @@ initialize_F (void)
 
       int j;
       FOR_EACH_SHIFT (sp, j)
 
       int j;
       FOR_EACH_SHIFT (sp, j)

-       bitset_set (F[i], TRANSITION_SYMBOL (sp, j));
+        bitset_set (goto_follows[i], TRANSITION_SYMBOL (sp, j));

 
       for (; j < sp->num; j++)
 
       for (; j < sp->num; j++)

-       {
-         symbol_number sym = TRANSITION_SYMBOL (sp, j);
-         if (nullable[sym - ntokens])
-           edge[nedges++] = map_goto (stateno, sym);
-       }
-
-      if (nedges)
-       {
-         CALLOC (reads[i], nedges + 1);
-         memcpy (reads[i], edge, nedges * sizeof (edge[0]));
-         reads[i][nedges] = -1;
-         nedges = 0;
-       }
+        {
+          symbol_number sym = TRANSITION_SYMBOL (sp, j);
+          if (nullable[sym - ntokens])
+            edge[nedges++] = map_goto (stateno, sym);
+        }
+
+      if (nedges == 0)
+        reads[i] = NULL;
+      else
+        {
+          reads[i] = xnmalloc (nedges + 1, sizeof reads[i][0]);
+          memcpy (reads[i], edge, nedges * sizeof edge[0]);
+          reads[i][nedges] = END_NODE;
+          nedges = 0;
+        }

     }
 
     }
 

-  relation_digraph (reads, ngotos, &F);
+  relation_digraph (reads, ngotos, &goto_follows);

 
   for (i = 0; i < ngotos; i++)
 
   for (i = 0; i < ngotos; i++)

-    XFREE (reads[i]);
+    free (reads[i]);

 
 

-  XFREE (reads);
-  XFREE (edge);
+  free (reads);
+  free (edge);

 }
 
 
 static void
 }
 
 
 static void

-add_lookback_edge (state *s, rule *r, int gotono)
+add_lookback_edge (state *s, rule *r, goto_number gotono)

 {
   int ri = state_reduction_find (s, r);
 {
   int ri = state_reduction_find (s, r);

-  goto_list *sp = MALLOC (sp, 1);
-  sp->next = lookback[(s->reductions->look_ahead_tokens - LA) + ri];
+  goto_list *sp = xmalloc (sizeof *sp);
+  sp->next = lookback[(s->reductions->lookahead_tokens - LA) + ri];

   sp->value = gotono;
   sp->value = gotono;

-  lookback[(s->reductions->look_ahead_tokens - LA) + ri] = sp;
+  lookback[(s->reductions->lookahead_tokens - LA) + ri] = sp;

 }
 
 
 }
 
 


@@ -225,11 +218,11 @@ add_lookback_edge (state *s, rule *r, int gotono)
 static void
 build_relations (void)
 {
 static void
 build_relations (void)
 {

-  goto_number *edge = CALLOC (edge, ngotos + 1);
-  state_number *states1 = CALLOC (states1, ritem_longest_rhs () + 1);
-  int i;
+  goto_number *edge = xnmalloc (ngotos + 1, sizeof *edge);
+  state_number *states1 = xnmalloc (ritem_longest_rhs () + 1, sizeof *states1);
+  goto_number i;

 
 

-  CALLOC (includes, ngotos);
+  includes = xnmalloc (ngotos, sizeof *includes);

 
   for (i = 0; i < ngotos; i++)
     {
 
   for (i = 0; i < ngotos; i++)
     {


@@ -238,53 +231,57 @@ build_relations (void)
       rule **rulep;
 
       for (rulep = derives[symbol1 - ntokens]; *rulep; rulep++)
       rule **rulep;
 
       for (rulep = derives[symbol1 - ntokens]; *rulep; rulep++)

-       {
-         bool done;
-         int length = 1;
-         item_number *rp;
-         state *s = states[from_state[i]];
-         states1[0] = s->number;
-
-         for (rp = (*rulep)->rhs; *rp >= 0; rp++)
-           {
-             s = transitions_to (s->transitions,
-                                 item_number_as_symbol_number (*rp));
-             states1[length++] = s->number;
-           }
-
-         if (!s->consistent)
-           add_lookback_edge (s, *rulep, i);
-
-         length--;
-         done = false;
-         while (!done)
-           {
-             done = true;
-             rp--;
-             /* JF added rp>=ritem &&   I hope to god its right! */
-             if (rp >= ritem && ISVAR (*rp))
-               {
-                 /* Downcasting from item_number to symbol_number.  */
-                 edge[nedges++] = map_goto (states1[--length],
-                                            item_number_as_symbol_number (*rp));
-                 if (nullable[*rp - ntokens])
-                   done = false;
-               }
-           }
-       }
-
-      if (nedges)
-       {
-         int j;
-         CALLOC (includes[i], nedges + 1);
-         for (j = 0; j < nedges; j++)
-           includes[i][j] = edge[j];
-         includes[i][nedges] = -1;
-       }
+        {
+          bool done;
+          int length = 1;
+          item_number const *rp;
+          state *s = states[from_state[i]];
+          states1[0] = s->number;
+
+          for (rp = (*rulep)->rhs; ! item_number_is_rule_number (*rp); rp++)
+            {
+              s = transitions_to (s->transitions,
+                                  item_number_as_symbol_number (*rp));
+              states1[length++] = s->number;
+            }
+
+          if (!s->consistent)
+            add_lookback_edge (s, *rulep, i);
+
+          length--;
+          done = false;
+          while (!done)
+            {
+              done = true;
+              /* Each rhs ends in a rule number, and there is a
+                 sentinel (ritem[-1]=0) before the first rhs, so it is safe to
+                 decrement RP here.  */
+              rp--;
+              if (ISVAR (*rp))
+                {
+                  /* Downcasting from item_number to symbol_number.  */
+                  edge[nedges++] = map_goto (states1[--length],
+                                             item_number_as_symbol_number (*rp));
+                  if (nullable[*rp - ntokens])
+                    done = false;
+                }
+            }
+        }
+
+      if (nedges == 0)
+        includes[i] = NULL;
+      else
+        {
+          int j;
+          includes[i] = xnmalloc (nedges + 1, sizeof includes[i][0]);
+          for (j = 0; j < nedges; j++)
+            includes[i][j] = edge[j];
+          includes[i][nedges] = END_NODE;
+        }

     }
 
     }
 

-  XFREE (edge);
-  XFREE (states1);
+  free (edge);
+  free (states1);

 
   relation_transpose (&includes, ngotos);
 }
 
   relation_transpose (&includes, ngotos);
 }


@@ -294,140 +291,153 @@ build_relations (void)
 static void
 compute_FOLLOWS (void)
 {
 static void
 compute_FOLLOWS (void)
 {

-  int i;
+  goto_number i;

 
 

-  relation_digraph (includes, ngotos, &F);
+  relation_digraph (includes, ngotos, &goto_follows);

 
   for (i = 0; i < ngotos; i++)
 
   for (i = 0; i < ngotos; i++)

-    XFREE (includes[i]);
+    free (includes[i]);

 
 

-  XFREE (includes);
+  free (includes);

 }
 
 
 static void
 }
 
 
 static void

-compute_look_ahead_tokens (void)
+compute_lookahead_tokens (void)

 {
   size_t i;
   goto_list *sp;
 
   for (i = 0; i < nLA; i++)
     for (sp = lookback[i]; sp; sp = sp->next)
 {
   size_t i;
   goto_list *sp;
 
   for (i = 0; i < nLA; i++)
     for (sp = lookback[i]; sp; sp = sp->next)

-      bitset_or (LA[i], LA[i], F[sp->value]);
+      bitset_or (LA[i], LA[i], goto_follows[sp->value]);

 
   /* Free LOOKBACK. */
   for (i = 0; i < nLA; i++)
     LIST_FREE (goto_list, lookback[i]);
 
 
   /* Free LOOKBACK. */
   for (i = 0; i < nLA; i++)
     LIST_FREE (goto_list, lookback[i]);
 

-  XFREE (lookback);
-  bitsetv_free (F);
+  free (lookback);

 }
 
 
 }
 
 

-/*-----------------------------------------------------.
-| Count the number of look-ahead tokens required for S |
-| (N_LOOK_AHEAD_TOKENS member).                        |
-`-----------------------------------------------------*/
+/*----------------------------------------------------.
+| Count the number of lookahead tokens required for S |
+| (N_LOOKAHEAD_TOKENS member).                        |
+`----------------------------------------------------*/

 
 static int
 
 static int

-state_look_ahead_tokens_count (state *s)
+state_lookahead_tokens_count (state *s, bool default_reduction_only_for_accept)

 {
 {

-  int k;
-  int n_look_ahead_tokens = 0;
+  int n_lookahead_tokens = 0;

   reductions *rp = s->reductions;
   transitions *sp = s->transitions;
 
   reductions *rp = s->reductions;
   transitions *sp = s->transitions;
 

-  /* We need a look-ahead either to distinguish different
-     reductions (i.e., there are two or more), or to distinguish a
-     reduction from a shift.  Otherwise, it is straightforward,
-     and the state is `consistent'.  */
+  /* Transitions are only disabled during conflict resolution, and that
+     hasn't happened yet, so there should be no need to check that
+     transition 0 hasn't been disabled before checking if it is a shift.
+     However, this check was performed at one time, so we leave it as an
+     aver.  */
+  aver (sp->num == 0 || !TRANSITION_IS_DISABLED (sp, 0));
+
+  /* We need a lookahead either to distinguish different reductions
+     (i.e., there are two or more), or to distinguish a reduction from a
+     shift.  Otherwise, it is straightforward, and the state is
+     'consistent'.  However, do not treat a state with any reductions as
+     consistent unless it is the accepting state (because there is never
+     a lookahead token that makes sense there, and so no lookahead token
+     should be read) if the user has otherwise disabled default
+     reductions.  */

   if (rp->num > 1
   if (rp->num > 1

-      || (rp->num == 1 && sp->num &&
-         !TRANSITION_IS_DISABLED (sp, 0) && TRANSITION_IS_SHIFT (sp, 0)))
-    n_look_ahead_tokens += rp->num;
+      || (rp->num == 1 && sp->num && TRANSITION_IS_SHIFT (sp, 0))
+      || (rp->num == 1 && rp->rules[0]->number != 0
+          && default_reduction_only_for_accept))
+    n_lookahead_tokens += rp->num;

   else
     s->consistent = 1;
 
   else
     s->consistent = 1;
 

-  for (k = 0; k < sp->num; k++)
-    if (!TRANSITION_IS_DISABLED (sp, k) && TRANSITION_IS_ERROR (sp, k))
-      {
-       s->consistent = 0;
-       break;
-      }
-
-  return n_look_ahead_tokens;
+  return n_lookahead_tokens;

 }
 
 
 }
 
 

-/*-----------------------------------------------------.
-| Compute LA, NLA, and the look_ahead_tokens members.  |
-`-----------------------------------------------------*/
+/*----------------------------------------------------.
+| Compute LA, NLA, and the lookahead_tokens members.  |
+`----------------------------------------------------*/

 
 

-static void
+void

 initialize_LA (void)
 {
   state_number i;
   bitsetv pLA;
 initialize_LA (void)
 {
   state_number i;
   bitsetv pLA;

+  bool default_reduction_only_for_accept;
+  {
+    char *default_reductions =
+      muscle_percent_define_get ("lr.default-reduction");
+    default_reduction_only_for_accept = STREQ (default_reductions, "accepting");
+    free (default_reductions);
+  }

 
 

-  /* Compute the total number of reductions requiring a look-ahead.  */
+  /* Compute the total number of reductions requiring a lookahead.  */

   nLA = 0;
   for (i = 0; i < nstates; i++)
   nLA = 0;
   for (i = 0; i < nstates; i++)

-    nLA += state_look_ahead_tokens_count (states[i]);
+    nLA +=
+      state_lookahead_tokens_count (states[i],
+                                    default_reduction_only_for_accept);

   /* Avoid having to special case 0.  */
   if (!nLA)
     nLA = 1;
 
   pLA = LA = bitsetv_create (nLA, ntokens, BITSET_FIXED);
   /* Avoid having to special case 0.  */
   if (!nLA)
     nLA = 1;
 
   pLA = LA = bitsetv_create (nLA, ntokens, BITSET_FIXED);

-  CALLOC (lookback, nLA);

 
 

-  /* Initialize the members LOOK_AHEAD_TOKENS for each state whose reductions
-     require look-ahead tokens.  */
+  /* Initialize the members LOOKAHEAD_TOKENS for each state whose reductions
+     require lookahead tokens.  */

   for (i = 0; i < nstates; i++)
     {
   for (i = 0; i < nstates; i++)
     {

-      int count = state_look_ahead_tokens_count (states[i]);
+      int count =
+        state_lookahead_tokens_count (states[i],
+                                      default_reduction_only_for_accept);

       if (count)
       if (count)

-       {
-         states[i]->reductions->look_ahead_tokens = pLA;
-         pLA += count;
-       }
+        {
+          states[i]->reductions->lookahead_tokens = pLA;
+          pLA += count;
+        }

     }
 }
 
 
     }
 }
 
 

-/*----------------------------------------------.
-| Output the look-ahead tokens for each state.  |
-`----------------------------------------------*/
+/*---------------------------------------------.
+| Output the lookahead tokens for each state.  |
+`---------------------------------------------*/

 
 static void
 
 static void

-look_ahead_tokens_print (FILE *out)
+lookahead_tokens_print (FILE *out)

 {
   state_number i;
   int j, k;
 {
   state_number i;
   int j, k;

-  fprintf (out, "Look-ahead tokens: BEGIN\n");
+  fprintf (out, "Lookahead tokens: BEGIN\n");

   for (i = 0; i < nstates; ++i)
     {
       reductions *reds = states[i]->reductions;
       bitset_iterator iter;
   for (i = 0; i < nstates; ++i)
     {
       reductions *reds = states[i]->reductions;
       bitset_iterator iter;

-      int n_look_ahead_tokens = 0;
-
-      if (reds->look_ahead_tokens)
-       for (k = 0; k < reds->num; ++k)
-         if (reds->look_ahead_tokens[k])
-           ++n_look_ahead_tokens;
-
-      fprintf (out, "State %d: %d look-ahead tokens\n",
-              i, n_look_ahead_tokens);
-
-      if (reds->look_ahead_tokens)
-       for (j = 0; j < reds->num; ++j)
-         BITSET_FOR_EACH (iter, reds->look_ahead_tokens[j], k, 0)
-         {
-           fprintf (out, "   on %d (%s) -> rule %d\n",
-                    k, symbols[k]->tag,
-                    reds->rules[j]->number);
-         };
+      int n_lookahead_tokens = 0;
+
+      if (reds->lookahead_tokens)
+        for (k = 0; k < reds->num; ++k)
+          if (reds->lookahead_tokens[k])
+            ++n_lookahead_tokens;
+
+      fprintf (out, "State %d: %d lookahead tokens\n",
+               i, n_lookahead_tokens);
+
+      if (reds->lookahead_tokens)
+        for (j = 0; j < reds->num; ++j)
+          BITSET_FOR_EACH (iter, reds->lookahead_tokens[j], k, 0)
+          {
+            fprintf (out, "   on %d (%s) -> rule %d\n",
+                     k, symbols[k]->tag,
+                     reds->rules[j]->number);
+          };

     }
     }

-  fprintf (out, "Look-ahead tokens: END\n");
+  fprintf (out, "Lookahead tokens: END\n");

 }
 
 void
 }
 
 void


@@ -436,12 +446,47 @@ lalr (void)
   initialize_LA ();
   set_goto_map ();
   initialize_F ();
   initialize_LA ();
   set_goto_map ();
   initialize_F ();

+  lookback = xcalloc (nLA, sizeof *lookback);

   build_relations ();
   compute_FOLLOWS ();
   build_relations ();
   compute_FOLLOWS ();

-  compute_look_ahead_tokens ();
+  compute_lookahead_tokens ();

 
   if (trace_flag & trace_sets)
 
   if (trace_flag & trace_sets)

-    look_ahead_tokens_print (stderr);
+    lookahead_tokens_print (stderr);
+}
+
+
+void
+lalr_update_state_numbers (state_number old_to_new[], state_number nstates_old)
+{
+  goto_number ngotos_reachable = 0;
+  symbol_number nonterminal = 0;
+  aver (nsyms == nvars + ntokens);
+  {
+    goto_number i;
+    for (i = 0; i < ngotos; ++i)
+      {
+        while (i == goto_map[nonterminal])
+          goto_map[nonterminal++] = ngotos_reachable;
+        /* If old_to_new[from_state[i]] = nstates_old, remove this goto
+           entry.  */
+        if (old_to_new[from_state[i]] != nstates_old)
+          {
+            /* from_state[i] is not removed, so it and thus to_state[i] are
+               reachable, so to_state[i] != nstates_old.  */
+            aver (old_to_new[to_state[i]] != nstates_old);
+            from_state[ngotos_reachable] = old_to_new[from_state[i]];
+            to_state[ngotos_reachable] = old_to_new[to_state[i]];
+            ++ngotos_reachable;
+          }
+      }
+  }
+  while (nonterminal <= nvars)
+    {
+      aver (ngotos == goto_map[nonterminal]);
+      goto_map[nonterminal++] = ngotos_reachable;
+    }
+  ngotos = ngotos_reachable;

 }
 
 
 }
 
 


@@ -450,6 +495,6 @@ lalr_free (void)
 {
   state_number s;
   for (s = 0; s < nstates; ++s)
 {
   state_number s;
   for (s = 0; s < nstates; ++s)

-    states[s]->reductions->look_ahead_tokens = NULL;
+    states[s]->reductions->lookahead_tokens = NULL;

   bitsetv_free (LA);
 }
   bitsetv_free (LA);
 }