Fix incorrect comment.

[bison.git] / src / nullable.c

diff --git a/src/nullable.c b/src/nullable.c
index f8c9b32e5cf523b36742cb375ef0a087188ce2be..e73344f8283f1552474879eca64a112fd0328e66 100644 (file)
--- a/src/nullable.c
+++ b/src/nullable.c
@@ -1,5 +1,7 @@
-/* Part of the bison parser generator,
-   Copyright 1984, 1989, 2000, 2001 Free Software Foundation, Inc.
+/* Calculate which nonterminals can expand into the null string for Bison.
+
+   Copyright (C) 1984, 1989, 2000, 2001, 2002, 2003, 2004 Free
+   Software Foundation, Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
 
@@ -15,8 +17,8 @@
 
    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.  */
+   the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02110-1301, USA.  */
 
 
 /* Set up NULLABLE, a vector saying which nonterminals can expand into
@@ -24,14 +26,21 @@
    do so.  */
 
 #include "system.h"
+
 #include "getargs.h"
-#include "symtab.h"
-#include "types.h"
 #include "gram.h"
-#include "reduce.h"
 #include "nullable.h"
+#include "reduce.h"
+#include "symtab.h"
+
+/* Linked list of rules.  */
+typedef struct rule_list
+{
+  struct rule_list *next;
+  rule *value;
+} rule_list;
 
-char *nullable = NULL;
+bool *nullable = NULL;
 
 static void
 nullable_print (FILE *out)
@@ -39,95 +48,96 @@ nullable_print (FILE *out)
   int i;
   fputs ("NULLABLE\n", out);
   for (i = ntokens; i < nsyms; i++)
-    fprintf (out, "\t%s: %s\n", symbols[i]->tag, nullable[i] ? "yes" : "no");
+    fprintf (out, "\t%s: %s\n", symbols[i]->tag,
+            nullable[i - ntokens] ? "yes" : "no");
   fputs ("\n\n", out);
 }
 
 void
-set_nullable (void)
+nullable_compute (void)
 {
-  int ruleno;
-  short *s1;
-  short *s2;
-  shorts *p;
+  rule_number ruleno;
+  symbol_number *s1;
+  symbol_number *s2;
+  rule_list *p;
 
-  short *squeue = XCALLOC (short, nvars);
-  short *rcount = XCALLOC (short, nrules + 1);
+  symbol_number *squeue = xnmalloc (nvars, sizeof *squeue);
+  size_t *rcount = xcalloc (nrules, sizeof *rcount);
   /* RITEM contains all the rules, including useless productions.
      Hence we must allocate room for useless nonterminals too.  */
-  shorts **rsets = XCALLOC (shorts *, nvars) - ntokens;
+  rule_list **rsets = xcalloc (nvars, sizeof *rsets);
   /* This is said to be more elements than we actually use.
      Supposedly NRITEMS - NRULES is enough.  But why take the risk?  */
-  shorts *relts = XCALLOC (shorts, nritems + nvars + 1);
-
-  if (trace_flag)
-    fprintf (stderr, "Entering set_nullable\n");
+  rule_list *relts = xnmalloc (nritems + nvars + 1, sizeof *relts);
 
-  nullable = XCALLOC (char, nvars) - ntokens;
+  nullable = xcalloc (nvars, sizeof *nullable);
 
   s1 = s2 = squeue;
   p = relts;
 
-  for (ruleno = 1; ruleno < nrules + 1; ++ruleno)
+  for (ruleno = 0; ruleno < nrules; ++ruleno)
     if (rules[ruleno].useful)
       {
-       if (ritem[rules[ruleno].rhs] >= 0)
+       rule *rules_ruleno = &rules[ruleno];
+       if (rules_ruleno->rhs[0] >= 0)
          {
            /* This rule has a non empty RHS. */
-           short *r;
-           int any_tokens = 0;
-           for (r = &ritem[rules[ruleno].rhs]; *r >= 0; ++r)
-             if (ISTOKEN (*r))
-               any_tokens = 1;
+           item_number *rp = NULL;
+           bool any_tokens = false;
+           for (rp = rules_ruleno->rhs; *rp >= 0; ++rp)
+             if (ISTOKEN (*rp))
+               any_tokens = true;
 
            /* This rule has only nonterminals: schedule it for the second
               pass.  */
            if (!any_tokens)
-             for (r = &ritem[rules[ruleno].rhs]; *r >= 0; ++r)
+             for (rp = rules_ruleno->rhs; *rp >= 0; ++rp)
                {
                  rcount[ruleno]++;
-                 p->next = rsets[*r];
-                 p->value = ruleno;
-                 rsets[*r] = p;
+                 p->next = rsets[*rp - ntokens];
+                 p->value = rules_ruleno;
+                 rsets[*rp - ntokens] = p;
                  p++;
                }
          }
        else
          {
            /* This rule has an empty RHS. */
-           assert (ritem[rules[ruleno].rhs] == -ruleno);
-           if (rules[ruleno].useful && !nullable[rules[ruleno].lhs])
+           if (item_number_as_rule_number (rules_ruleno->rhs[0]) != ruleno)
+             abort ();
+           if (rules_ruleno->useful
+               && ! nullable[rules_ruleno->lhs->number - ntokens])
              {
-               nullable[rules[ruleno].lhs] = 1;
-               *s2++ = rules[ruleno].lhs;
+               nullable[rules_ruleno->lhs->number - ntokens] = true;
+               *s2++ = rules_ruleno->lhs->number;
              }
          }
       }
 
   while (s1 < s2)
-    for (p = rsets[*s1++]; p; p = p->next)
+    for (p = rsets[*s1++ - ntokens]; p; p = p->next)
       {
-       ruleno = p->value;
-       if (--rcount[ruleno] == 0)
-         if (rules[ruleno].useful && !nullable[rules[ruleno].lhs])
+       rule *r = p->value;
+       if (--rcount[r->number] == 0)
+         if (r->useful && ! nullable[r->lhs->number - ntokens])
            {
-             nullable[rules[ruleno].lhs] = 1;
-             *s2++ = rules[ruleno].lhs;
+             nullable[r->lhs->number - ntokens] = true;
+             *s2++ = r->lhs->number;
            }
       }
 
-  XFREE (squeue);
-  XFREE (rcount);
-  XFREE (rsets + ntokens);
-  XFREE (relts);
+  free (squeue);
+  free (rcount);
+  free (rsets);
+  free (relts);
 
-  if (trace_flag)
+  if (trace_flag & trace_sets)
     nullable_print (stderr);
 }
 
 
 void
-free_nullable (void)
+nullable_free (void)
 {
-  XFREE (nullable + ntokens);
+  free (nullable);
 }