src/derives.c

   1 /* Match rules with nonterminals for bison,
   2    Copyright (C) 1984, 1989, 2000 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 "xalloc.h"
  29 #include "types.h"
  30 #include "gram.h"
  31 #include "derives.h"
  32
  33 short **derives;
  34
  35 #if DEBUG
  36
  37 static void
  38 print_derives (void)
  39 {
  40   int i;
  41   short *sp;
  42
  43   fputs ("\n\n\n", stdout);
  44   printf (_("DERIVES"));
  45   fputs ("\n\n", stdout);
  46
  47   for (i = ntokens; i < nsyms; i++)
  48     {
  49       printf (_("%s derives"), tags[i]);
  50       for (sp = derives[i]; *sp > 0; sp++)
  51         {
  52           printf ("  %d", *sp);
  53         }
  54       putchar ('\n');
  55     }
  56
  57   putchar ('\n');
  58 }
  59
  60 #endif
  61
  62 void
  63 set_derives (void)
  64 {
  65   int i;
  66   int lhs;
  67   shorts *p;
  68   short *q;
  69   shorts **dset;
  70   shorts *delts;
  71
  72   dset = XCALLOC (shorts *, nvars) - ntokens;
  73   delts = XCALLOC (shorts, nrules + 1);
  74
  75   p = delts;
  76   for (i = nrules; i > 0; i--)
  77     {
  78       lhs = rlhs[i];
  79       if (lhs >= 0)
  80         {
  81           p->next = dset[lhs];
  82           p->value = i;
  83           dset[lhs] = p;
  84           p++;
  85         }
  86     }
  87
  88   derives = XCALLOC (short *, nvars) - ntokens;
  89   q = XCALLOC (short, nvars + nrules);
  90
  91   for (i = ntokens; i < nsyms; i++)
  92     {
  93       derives[i] = q;
  94       p = dset[i];
  95       while (p)
  96         {
  97           *q++ = p->value;
  98           p = p->next;
  99         }
 100       *q++ = -1;
 101     }
 102
 103 #if DEBUG
 104   print_derives ();
 105 #endif
 106
 107   XFREE (dset + ntokens);
 108   XFREE (delts);
 109 }
 110
 111 void
 112 free_derives (void)
 113 {
 114   XFREE (derives[ntokens]);
 115   XFREE (derives + ntokens);
 116 }