mirror of
https://git.savannah.gnu.org/git/bison.git
synced 2026-03-09 20:33:03 +00:00
1a2b5d37e1
* src/gram.h, src/lalr.c, src/nullable.c, src/output.c, src/print.c * src/print_graph.c, src/reader.c, src/reduce.c: Rename rule_table as rules.
134 lines
3.3 KiB
C
134 lines
3.3 KiB
C
/* Part of the bison parser generator,
|
|
Copyright 1984, 1989, 2000, 2001 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
|
|
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.
|
|
|
|
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
|
|
do so. */
|
|
|
|
#include "system.h"
|
|
#include "getargs.h"
|
|
#include "symtab.h"
|
|
#include "types.h"
|
|
#include "gram.h"
|
|
#include "reduce.h"
|
|
#include "nullable.h"
|
|
|
|
char *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] ? "yes" : "no");
|
|
fputs ("\n\n", out);
|
|
}
|
|
|
|
void
|
|
set_nullable (void)
|
|
{
|
|
int ruleno;
|
|
short *s1;
|
|
short *s2;
|
|
shorts *p;
|
|
|
|
short *squeue = XCALLOC (short, nvars);
|
|
short *rcount = XCALLOC (short, nrules + 1);
|
|
/* RITEM contains all the rules, including useless productions.
|
|
Hence we must allocate room for useless nonterminals too. */
|
|
shorts **rsets = XCALLOC (shorts *, nvars) - ntokens;
|
|
/* This is said to be more elements than we actually use.
|
|
Supposedly NRITEMS - NRULES is enough. But why take the risk? */
|
|
shorts *relts = XCALLOC (shorts, nritems + nvars + 1);
|
|
|
|
if (trace_flag)
|
|
fprintf (stderr, "Entering set_nullable\n");
|
|
|
|
nullable = XCALLOC (char, nvars) - ntokens;
|
|
|
|
s1 = s2 = squeue;
|
|
p = relts;
|
|
|
|
for (ruleno = 1; ruleno < nrules + 1; ++ruleno)
|
|
if (rules[ruleno].useful)
|
|
{
|
|
if (ritem[rules[ruleno].rhs] >= 0)
|
|
{
|
|
/* This rule has a non empty RHS. */
|
|
short *r;
|
|
int any_tokens = 0;
|
|
for (r = &ritem[rules[ruleno].rhs]; *r >= 0; ++r)
|
|
if (ISTOKEN (*r))
|
|
any_tokens = 1;
|
|
|
|
/* This rule has only nonterminals: schedule it for the second
|
|
pass. */
|
|
if (!any_tokens)
|
|
for (r = &ritem[rules[ruleno].rhs]; *r >= 0; ++r)
|
|
{
|
|
rcount[ruleno]++;
|
|
p->next = rsets[*r];
|
|
p->value = ruleno;
|
|
rsets[*r] = p;
|
|
p++;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
/* This rule has an empty RHS. */
|
|
assert (ritem[rules[ruleno].rhs] == -ruleno);
|
|
if (rules[ruleno].useful && !nullable[rules[ruleno].lhs])
|
|
{
|
|
nullable[rules[ruleno].lhs] = 1;
|
|
*s2++ = rules[ruleno].lhs;
|
|
}
|
|
}
|
|
}
|
|
|
|
while (s1 < s2)
|
|
for (p = rsets[*s1++]; p; p = p->next)
|
|
{
|
|
ruleno = p->value;
|
|
if (--rcount[ruleno] == 0)
|
|
if (rules[ruleno].useful && !nullable[rules[ruleno].lhs])
|
|
{
|
|
nullable[rules[ruleno].lhs] = 1;
|
|
*s2++ = rules[ruleno].lhs;
|
|
}
|
|
}
|
|
|
|
XFREE (squeue);
|
|
XFREE (rcount);
|
|
XFREE (rsets + ntokens);
|
|
XFREE (relts);
|
|
|
|
if (trace_flag)
|
|
nullable_print (stderr);
|
|
}
|
|
|
|
|
|
void
|
|
free_nullable (void)
|
|
{
|
|
XFREE (nullable + ntokens);
|
|
}
|