X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/ceed8467b7db3615d3c9bfa9f3e5525d54c6a161..c0ad8bf3c2fb46f001bb24ac98a72b8bfb3a77ce:/src/nullable.c diff --git a/src/nullable.c b/src/nullable.c index 516fce40..c0b60f64 100644 --- a/src/nullable.c +++ b/src/nullable.c @@ -1,139 +1,137 @@ /* Part of the bison parser generator, - Copyright (C) 1984, 1989 Free Software Foundation, Inc. + Copyright (C) 1984, 1989, 2000, 2001, 2002 Free Software Foundation, Inc. -This file is part of Bison, the GNU Compiler Compiler. + This file is part of Bison, the GNU Compiler Compiler. -Bison 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. + Bison 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. -Bison 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. + Bison 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. */ + 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. */ -/* set up nullable, a vector saying which nonterminals can expand into - the null string. nullable[i - ntokens] is nonzero if symbol i can +/* 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 "system.h" -#include "types.h" +#include "getargs.h" +#include "symtab.h" #include "gram.h" -#include "alloc.h" +#include "reduce.h" +#include "nullable.h" +/* Linked list of rules. */ +typedef struct rule_list_s +{ + struct rule_list_s *next; + rule_t *value; +} rule_list_t; -char *nullable; +bool *nullable = NULL; -extern void free_nullable PARAMS((void)); -extern void set_nullable PARAMS((void)); +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] ? "yes" : "no"); + fputs ("\n\n", out); +} void -set_nullable (void) +nullable_compute (void) { - register short *r; - register short *s1; - register short *s2; - register int ruleno; - register int symbol; - register shorts *p; - - short *squeue; - short *rcount; - shorts **rsets; - shorts *relts; - char any_tokens; - short *r1; - -#ifdef TRACE - fprintf(stderr, _("Entering set_nullable")); -#endif - - nullable = NEW2(nvars, char) - ntokens; - - squeue = NEW2(nvars, short); - s1 = s2 = squeue; - - rcount = NEW2(nrules + 1, short); - rsets = NEW2(nvars, shorts *) - ntokens; + rule_number_t ruleno; + symbol_number_t *s1; + symbol_number_t *s2; + rule_list_t *p; + + symbol_number_t *squeue = XCALLOC (symbol_number_t, nvars); + short *rcount = XCALLOC (short, nrules); + /* RITEM contains all the rules, including useless productions. + Hence we must allocate room for useless nonterminals too. */ + rule_list_t **rsets = XCALLOC (rule_list_t *, nvars) - ntokens; /* This is said to be more elements than we actually use. - Supposedly nitems - nrules is enough. - But why take the risk? */ - relts = NEW2(nitems + nvars + 1, shorts); + Supposedly NRITEMS - NRULES is enough. But why take the risk? */ + rule_list_t *relts = XCALLOC (rule_list_t, nritems + nvars + 1); + + nullable = XCALLOC (bool, nvars) - ntokens; + + s1 = s2 = squeue; p = relts; - r = ritem; - while (*r) - { - if (*r < 0) - { - symbol = rlhs[-(*r++)]; - if (symbol >= 0 && !nullable[symbol]) - { - nullable[symbol] = 1; - *s2++ = symbol; - } - } - else - { - r1 = r; - any_tokens = 0; - for (symbol = *r++; symbol > 0; symbol = *r++) - { - if (ISTOKEN(symbol)) + for (ruleno = 0; ruleno < nrules; ++ruleno) + if (rules[ruleno].useful) + { + rule_t *rule = &rules[ruleno]; + if (rule->rhs[0] >= 0) + { + /* This rule has a non empty RHS. */ + item_number_t *r = NULL; + int any_tokens = 0; + for (r = rule->rhs; *r >= 0; ++r) + if (ISTOKEN (*r)) any_tokens = 1; - } - if (!any_tokens) - { - ruleno = -symbol; - r = r1; - for (symbol = *r++; symbol > 0; symbol = *r++) + /* This rule has only nonterminals: schedule it for the second + pass. */ + if (!any_tokens) + for (r = rule->rhs; *r >= 0; ++r) { rcount[ruleno]++; - p->next = rsets[symbol]; - p->value = ruleno; - rsets[symbol] = p; + p->next = rsets[*r]; + p->value = rule; + rsets[*r] = p; p++; } - } - } - } + } + else + { + /* This rule has an empty RHS. */ + assert (item_number_as_rule_number (rule->rhs[0]) == ruleno); + if (rule->useful && !nullable[rule->lhs->number]) + { + nullable[rule->lhs->number] = 1; + *s2++ = rule->lhs->number; + } + } + } while (s1 < s2) - { - p = rsets[*s1++]; - while (p) - { - ruleno = p->value; - p = p->next; - if (--rcount[ruleno] == 0) + for (p = rsets[*s1++]; p; p = p->next) + { + rule_t *rule = p->value; + if (--rcount[rule->number] == 0) + if (rule->useful && !nullable[rule->lhs->number]) { - symbol = rlhs[ruleno]; - if (symbol >= 0 && !nullable[symbol]) - { - nullable[symbol] = 1; - *s2++ = symbol; - } + nullable[rule->lhs->number] = 1; + *s2++ = rule->lhs->number; } - } - } + } + + XFREE (squeue); + XFREE (rcount); + XFREE (rsets + ntokens); + XFREE (relts); - FREE(squeue); - FREE(rcount); - FREE(rsets + ntokens); - FREE(relts); + if (trace_flag & trace_sets) + nullable_print (stderr); } void -free_nullable (void) +nullable_free (void) { - FREE(nullable + ntokens); + XFREE (nullable + ntokens); }