mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-19 10:53:58 +00:00
140 lines
2.8 KiB
C
140 lines
2.8 KiB
C
/* Part of the bison parser generator,
|
|
Copyright (C) 1984, 1989 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 <stdio.h>
|
|
#include "system.h"
|
|
#include "types.h"
|
|
#include "gram.h"
|
|
#include "alloc.h"
|
|
|
|
|
|
char *nullable;
|
|
|
|
void free_nullable PARAMS((void));
|
|
void set_nullable PARAMS((void));
|
|
|
|
void
|
|
set_nullable (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;
|
|
/* 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);
|
|
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))
|
|
any_tokens = 1;
|
|
}
|
|
|
|
if (!any_tokens)
|
|
{
|
|
ruleno = -symbol;
|
|
r = r1;
|
|
for (symbol = *r++; symbol > 0; symbol = *r++)
|
|
{
|
|
rcount[ruleno]++;
|
|
p->next = rsets[symbol];
|
|
p->value = ruleno;
|
|
rsets[symbol] = p;
|
|
p++;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
while (s1 < s2)
|
|
{
|
|
p = rsets[*s1++];
|
|
while (p)
|
|
{
|
|
ruleno = p->value;
|
|
p = p->next;
|
|
if (--rcount[ruleno] == 0)
|
|
{
|
|
symbol = rlhs[ruleno];
|
|
if (symbol >= 0 && !nullable[symbol])
|
|
{
|
|
nullable[symbol] = 1;
|
|
*s2++ = symbol;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
FREE(squeue);
|
|
FREE(rcount);
|
|
FREE(rsets + ntokens);
|
|
FREE(relts);
|
|
}
|
|
|
|
|
|
void
|
|
free_nullable (void)
|
|
{
|
|
FREE(nullable + ntokens);
|
|
}
|