| 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
|
|
|
|
|