Index: bison/src/bison/2.4.1/bison-2.4.1-src/src/nullable.c |
=================================================================== |
--- bison/src/bison/2.4.1/bison-2.4.1-src/src/nullable.c (revision 0) |
+++ bison/src/bison/2.4.1/bison-2.4.1-src/src/nullable.c (revision 0) |
@@ -0,0 +1,142 @@ |
+/* Calculate which nonterminals can expand into the null string for Bison. |
+ |
+ Copyright (C) 1984, 1989, 2000, 2001, 2002, 2003, 2004, 2005, 2006 |
+ Free Software Foundation, Inc. |
+ |
+ This file is part of Bison, the GNU Compiler Compiler. |
+ |
+ 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 |
+ the Free Software Foundation, either version 3 of the License, or |
+ (at your option) any later version. |
+ |
+ 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 |
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
+ |
+ |
+/* Set up NULLABLE, a vector saying which nonterminals can expand into |
+ the null string. NULLABLE[I - NTOKENS] is nonzero if symbol I can |
+ do so. */ |
+ |
+#include <config.h> |
+#include "system.h" |
+ |
+#include "getargs.h" |
+#include "gram.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; |
+ |
+bool *nullable = NULL; |
+ |
+static void |
+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 - ntokens] ? "yes" : "no"); |
+ fputs ("\n\n", out); |
+} |
+ |
+void |
+nullable_compute (void) |
+{ |
+ 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. */ |
+ 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? */ |
+ rule_list *relts = xnmalloc (nritems + nvars + 1, sizeof *relts); |
+ |
+ nullable = xcalloc (nvars, sizeof *nullable); |
+ |
+ s1 = s2 = squeue; |
+ p = relts; |
+ |
+ for (ruleno = 0; ruleno < nrules; ++ruleno) |
+ if (rules[ruleno].useful) |
+ { |
+ rule *rules_ruleno = &rules[ruleno]; |
+ if (rules_ruleno->rhs[0] >= 0) |
+ { |
+ /* 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++; |
+ } |
+ } |
+ else |
+ { |
+ /* This rule has an empty RHS. */ |
+ aver (item_number_as_rule_number (rules_ruleno->rhs[0]) |
+ == ruleno); |
+ 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++ - ntokens]; p; p = p->next) |
+ { |
+ rule *r = p->value; |
+ if (--rcount[r->number] == 0) |
+ if (r->useful && ! nullable[r->lhs->number - ntokens]) |
+ { |
+ nullable[r->lhs->number - ntokens] = true; |
+ *s2++ = r->lhs->number; |
+ } |
+ } |
+ |
+ free (squeue); |
+ free (rcount); |
+ free (rsets); |
+ free (relts); |
+ |
+ if (trace_flag & trace_sets) |
+ nullable_print (stderr); |
+} |
+ |
+ |
+void |
+nullable_free (void) |
+{ |
+ free (nullable); |
+} |
Property changes on: bison\src\bison\2.4.1\bison-2.4.1-src\src\nullable.c |
___________________________________________________________________ |
Added: svn:eol-style |
+ LF |