src/derives.c

   1 /* Match rules with nonterminals for bison,
   2    Copyright 1984, 1989, 2000, 2001  Free Software Foundation, Inc.
   3
   4    This file is part of Bison, the GNU Compiler Compiler.
   5
   6    Bison is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    Bison is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with Bison; see the file COPYING.  If not, write to
  18    the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21
  22 /* set_derives finds, for each variable (nonterminal), which rules can
  23    derive it.  It sets up the value of derives so that derives[i -
  24    ntokens] points to a vector of rule numbers, terminated with -1.
  25    */
  26
  27 #include "system.h"
  28 #include "getargs.h"
  29 #include "types.h"
  30 #include "reader.h"
  31 #include "gram.h"
  32 #include "derives.h"
  33
  34 short **derives;
  35
  36
  37 static void
  38 print_derives (void)
  39 {
  40   int i;
  41   short *sp;
  42
  43   fputs ("DERIVES\n", stderr);
  44
  45   for (i = ntokens; i < nsyms; i++)
  46     {
  47       fprintf (stderr, "\t%s derives\n", tags[i]);
  48       for (sp = derives[i]; *sp > 0; sp++)
  49         fprintf (stderr, "\t\t%d (%s)\n", *sp, tags[*sp]);
  50     }
  51
  52   fputs ("\n\n", stderr);
  53 }
  54
  55
  56 void
  57 set_derives (void)
  58 {
  59   int i;
  60   int lhs;
  61   shorts *p;
  62   short *q;
  63   shorts **dset;
  64   shorts *delts;
  65
  66   dset = XCALLOC (shorts *, nvars) - ntokens;
  67   delts = XCALLOC (shorts, nrules + 1);
  68
  69   p = delts;
  70   for (i = nrules; i > 0; i--)
  71     {
  72       lhs = rule_table[i].lhs;
  73       if (lhs >= 0)
  74         {
  75           p->next = dset[lhs];
  76           p->value = i;
  77           dset[lhs] = p;
  78           p++;
  79         }
  80     }
  81
  82   derives = XCALLOC (short *, nvars) - ntokens;
  83   q = XCALLOC (short, nvars + nrules);
  84
  85   for (i = ntokens; i < nsyms; i++)
  86     {
  87       derives[i] = q;
  88       p = dset[i];
  89       while (p)
  90         {
  91           *q++ = p->value;
  92           p = p->next;
  93         }
  94       *q++ = -1;
  95     }
  96
  97   if (trace_flag)
  98     print_derives ();
  99
 100   XFREE (dset + ntokens);
 101   XFREE (delts);
 102 }
 103
 104 void
 105 free_derives (void)
 106 {
 107   XFREE (derives[ntokens]);
 108   XFREE (derives + ntokens);
 109 }