X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/e3e4e81446edb4e92e21cde1fc873f517b9402ea..2cbd078f5153288a39cbf046231a3870df8170cb:/src/nullable.c?ds=sidebyside

diff --git a/src/nullable.c b/src/nullable.c
index 8e8809e2..e73344f8 100644
--- 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 "reader.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)
@@ -39,97 +48,96 @@ nullable_print (FILE *out)
   int i;
   fputs ("NULLABLE\n", out);
   for (i = ntokens; i < nsyms; i++)
-    fprintf (out, "\t%s: %s\n", tags[i], 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)
 {
-  short *r;
-  short *s1;
-  short *s2;
-  shorts *p;
-
-  short *squeue;
-  short *rcount;
-  shorts **rsets;
-  shorts *relts;
-
-  if (trace_flag)
-    fprintf (stderr, "Entering set_nullable\n");
-
-  nullable = XCALLOC (char, nvars) - ntokens;
-
-  squeue = XCALLOC (short, nvars);
-  s1 = s2 = squeue;
-
-  rcount = XCALLOC (short, nrules + 1);
+  rule_number ruleno;
+  symbol_number *s1;
+  symbol_number *s2;
+  rule_list *p;
 
+  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.  */
-  rsets = XCALLOC (shorts *, nvars + nuseless_nonterminals) - ntokens;
+  rule_list **rsets = xcalloc (nvars, sizeof *rsets);
   /* This is said to be more elements than we actually use.
-     Supposedly nitems - nrules is enough.
-     But why take the risk?  */
-  relts = XCALLOC (shorts, nitems + nvars + nuseless_nonterminals + 1);
+     Supposedly NRITEMS - NRULES is enough.  But why take the risk?  */
+  rule_list *relts = xnmalloc (nritems + nvars + 1, sizeof *relts);
+
+  nullable = xcalloc (nvars, sizeof *nullable);
+
+  s1 = s2 = squeue;
   p = relts;
 
-  for (r = ritem; *r; ++r)
-    {
-      /* Walk RITEM to find (i), if there are any tokens in the
-	 RHS, and (ii), to find RULENO. */
-      int ruleno;
-      int any_tokens = 0;
-      short *r1;
-      for (r1 = r; *r1 > 0; ++r1)
-	if (ISTOKEN (*r1))
-	  any_tokens = 1;
-      ruleno = -*r1;
-
-      /* Examine the RHS of the rule.  */
-      if (!any_tokens)
-	for (/* Nothing. */; *r > 0; ++r)
+  for (ruleno = 0; ruleno < nrules; ++ruleno)
+    if (rules[ruleno].useful)
+      {
+	rule *rules_ruleno = &rules[ruleno];
+	if (rules_ruleno->rhs[0] >= 0)
 	  {
-	    rcount[ruleno]++;
-	    p->next = rsets[*r];
-	    p->value = ruleno;
-	    rsets[*r] = p;
-	    p++;
+	    /* This rule has a non empty RHS. */
+	    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 (rp = rules_ruleno->rhs; *rp >= 0; ++rp)
+		{
+		  rcount[ruleno]++;
+		  p->next = rsets[*rp - ntokens];
+		  p->value = rules_ruleno;
+		  rsets[*rp - ntokens] = p;
+		  p++;
+		}
 	  }
-
-      /* Examine its LHS. */
-      if (rule_table[ruleno].useful && !nullable[rule_table[ruleno].lhs])
-	{
-	  nullable[rule_table[ruleno].lhs] = 1;
-	  *s2++ = rule_table[ruleno].lhs;
-        }
-    }
+	else
+	  {
+	    /* This rule has an empty RHS. */
+	    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->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)
       {
-	int ruleno = p->value;
-	if (--rcount[ruleno] == 0)
-	  if (rule_table[ruleno].useful && !nullable[rule_table[ruleno].lhs])
+	rule *r = p->value;
+	if (--rcount[r->number] == 0)
+	  if (r->useful && ! nullable[r->lhs->number - ntokens])
 	    {
-	      nullable[rule_table[ruleno].lhs] = 1;
-	      *s2++ = rule_table[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);
 }