src/derives.c

   1 /* Match rules with nonterminals for bison,
   2
   3    Copyright (C) 1984, 1989, 2000-2003, 2005, 2009-2015, 2018-2021 Free
   4    Software Foundation, Inc.
   5
   6    This file is part of Bison, the GNU Compiler Compiler.
   7
   8    This program is free software: you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation, either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  20
  21 #include <config.h>
  22 #include "system.h"
  23
  24 #include "getargs.h"
  25
  26 #include "derives.h"
  27 #include "gram.h"
  28 #include "reader.h"
  29 #include "symtab.h"
  30
  31 /* Linked list of rule numbers.  */
  32 typedef struct rule_list
  33 {
  34   struct rule_list *next;
  35   rule *value;
  36 } rule_list;
  37
  38 rule ***derives;
  39
  40 static void
  41 print_derives (void)
  42 {
  43   fputs ("DERIVES\n", stderr);
  44
  45   for (symbol_number i = ntokens; i < nsyms; ++i)
  46     {
  47       fprintf (stderr, "  %s derives\n", symbols[i]->tag);
  48       for (rule **rp = derives[i - ntokens]; *rp; ++rp)
  49         {
  50           fprintf (stderr, "    %3d ", (*rp)->code);
  51           rule_rhs_print (*rp, stderr);
  52           fprintf (stderr, "\n");
  53         }
  54     }
  55
  56   fputs ("\n\n", stderr);
  57 }
  58
  59
  60 void
  61 derives_compute (void)
  62 {
  63   /* DSET[NTERM - NTOKENS] -- A linked list of the numbers of the rules
  64      whose LHS is NTERM.  */
  65   rule_list **dset = xcalloc (nnterms, sizeof *dset);
  66
  67   /* DELTS[RULE] -- There are NRULES rule number to attach to nterms.
  68      Instead of performing NRULES allocations for each, have an array
  69      indexed by rule numbers.  */
  70   rule_list *delts = xnmalloc (nrules, sizeof *delts);
  71
  72   for (rule_number r = nrules - 1; r >= 0; --r)
  73     {
  74       symbol_number lhs = rules[r].lhs->number;
  75       rule_list *p = &delts[r];
  76       /* A new LHS is found.  */
  77       p->next = dset[lhs - ntokens];
  78       p->value = &rules[r];
  79       dset[lhs - ntokens] = p;
  80     }
  81
  82   /* DSET contains what we need under the form of a linked list.  Make
  83      it a single array.  */
  84
  85   derives = xnmalloc (nnterms, sizeof *derives);
  86   /* Q is the storage for DERIVES[...] (DERIVES[0] = q).  */
  87   rule **q = xnmalloc (nnterms + nrules, sizeof *q);
  88
  89   for (symbol_number i = ntokens; i < nsyms; ++i)
  90     {
  91       rule_list *p = dset[i - ntokens];
  92       derives[i - ntokens] = q;
  93       while (p)
  94         {
  95           *q++ = p->value;
  96           p = p->next;
  97         }
  98       *q++ = NULL;
  99     }
 100
 101   if (trace_flag & trace_sets)
 102     print_derives ();
 103
 104   free (dset);
 105   free (delts);
 106 }
 107
 108
 109 void
 110 derives_free (void)
 111 {
 112   if (derives)
 113     {
 114       free (derives[0]);
 115       free (derives);
 116     }
 117 }