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bb0027a9ac
`rule_number_t**'. (set_derives, free_derives): Rename as... (derives_compute, derives_free): this. Adjust all dependencies. * src/nullable.c (set_nullable, free_nullable): Rename as... (nullable_compute, nullable_free): these. (rule_list_t): Store rule_t *, not rule_number_t. * src/state.c (state_rule_lookaheads_print): Directly compare rule pointers, instead of their numbers. * src/main.c (main): Call nullable_free, and derives_free earlier, as they were lo longer used.
138 lines
3.5 KiB
C
138 lines
3.5 KiB
C
/* Part of the bison parser generator,
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Copyright (C) 1984, 1989, 2000, 2001, 2002 Free Software Foundation, Inc.
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This file is part of Bison, the GNU Compiler Compiler.
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Bison is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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Bison is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with Bison; see the file COPYING. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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/* Set up NULLABLE, a vector saying which nonterminals can expand into
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the null string. NULLABLE[I - NTOKENS] is nonzero if symbol I can
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do so. */
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#include "system.h"
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#include "getargs.h"
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#include "symtab.h"
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#include "gram.h"
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#include "reduce.h"
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#include "nullable.h"
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/* Linked list of rules. */
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typedef struct rule_list_s
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{
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struct rule_list_s *next;
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rule_t *value;
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} rule_list_t;
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bool *nullable = NULL;
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static void
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nullable_print (FILE *out)
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{
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int i;
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fputs ("NULLABLE\n", out);
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for (i = ntokens; i < nsyms; i++)
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fprintf (out, "\t%s: %s\n", symbols[i]->tag, nullable[i] ? "yes" : "no");
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fputs ("\n\n", out);
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}
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void
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nullable_compute (void)
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{
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rule_number_t ruleno;
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symbol_number_t *s1;
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symbol_number_t *s2;
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rule_list_t *p;
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symbol_number_t *squeue = XCALLOC (symbol_number_t, nvars);
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short *rcount = XCALLOC (short, nrules);
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/* RITEM contains all the rules, including useless productions.
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Hence we must allocate room for useless nonterminals too. */
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rule_list_t **rsets = XCALLOC (rule_list_t *, nvars) - ntokens;
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/* This is said to be more elements than we actually use.
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Supposedly NRITEMS - NRULES is enough. But why take the risk? */
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rule_list_t *relts = XCALLOC (rule_list_t, nritems + nvars + 1);
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nullable = XCALLOC (bool, nvars) - ntokens;
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s1 = s2 = squeue;
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p = relts;
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for (ruleno = 0; ruleno < nrules; ++ruleno)
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if (rules[ruleno].useful)
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{
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rule_t *rule = &rules[ruleno];
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if (rule->rhs[0] >= 0)
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{
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/* This rule has a non empty RHS. */
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item_number_t *r = NULL;
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int any_tokens = 0;
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for (r = rule->rhs; *r >= 0; ++r)
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if (ISTOKEN (*r))
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any_tokens = 1;
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/* This rule has only nonterminals: schedule it for the second
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pass. */
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if (!any_tokens)
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for (r = rule->rhs; *r >= 0; ++r)
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{
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rcount[ruleno]++;
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p->next = rsets[*r];
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p->value = rule;
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rsets[*r] = p;
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p++;
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}
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}
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else
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{
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/* This rule has an empty RHS. */
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assert (item_number_as_rule_number (rule->rhs[0]) == ruleno);
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if (rule->useful && !nullable[rule->lhs->number])
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{
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nullable[rule->lhs->number] = 1;
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*s2++ = rule->lhs->number;
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}
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}
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}
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while (s1 < s2)
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for (p = rsets[*s1++]; p; p = p->next)
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{
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rule_t *rule = p->value;
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if (--rcount[rule->number] == 0)
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if (rule->useful && !nullable[rule->lhs->number])
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{
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nullable[rule->lhs->number] = 1;
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*s2++ = rule->lhs->number;
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}
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}
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XFREE (squeue);
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XFREE (rcount);
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XFREE (rsets + ntokens);
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XFREE (relts);
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if (trace_flag & trace_sets)
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nullable_print (stderr);
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}
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void
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nullable_free (void)
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{
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XFREE (nullable + ntokens);
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}
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