X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/630e182b7ba2257805c49424c96b9dc03a113668..e2c2f696504e69ad69beb700c5e37b0ff6d0b81b:/src/nullable.c?ds=sidebyside diff --git a/src/nullable.c b/src/nullable.c index 2797180c..7ee66120 100644 --- a/src/nullable.c +++ b/src/nullable.c @@ -1,37 +1,45 @@ -/* 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, 2005, 2006 + Free Software Foundation, Inc. This file is part of Bison, the GNU Compiler Compiler. - Bison is free software; you can redistribute it and/or modify + 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 2, or (at your option) - any later version. + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. - Bison is distributed in the hope that it will be useful, + 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 Bison; see the file COPYING. If not, write to - the Free Software Foundation, Inc., 59 Temple Place - Suite 330, - Boston, MA 02111-1307, USA. */ + along with this program. If not, see . */ /* 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 #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) @@ -39,104 +47,96 @@ 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. */ + 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) - { - p = rsets[*s1++]; - while (p) - { - int ruleno = p->value; - p = p->next; - if (--rcount[ruleno] == 0) + 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]) { - int symbol = rule_table[ruleno].lhs; - if (symbol >= 0 && !nullable[symbol]) - { - nullable[symbol] = 1; - *s2++ = symbol; - } + 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); }