annotate Parser/firstsets.c @ 4566:6403c94de50d legacy-trunk

Added safeguard against failure in __del__.
author Guido van Rossum <guido@python.org>
date Wed, 27 Nov 1996 19:39:58 +0000
parents 65d2d8e67da3
children 1c9a84e0981d
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1 /***********************************************************
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2 Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
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3 The Netherlands.
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4
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5 All Rights Reserved
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6
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7 Permission to use, copy, modify, and distribute this software and its
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8 documentation for any purpose and without fee is hereby granted,
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9 provided that the above copyright notice appear in all copies and that
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10 both that copyright notice and this permission notice appear in
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11 supporting documentation, and that the names of Stichting Mathematisch
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12 Centrum or CWI or Corporation for National Research Initiatives or
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13 CNRI not be used in advertising or publicity pertaining to
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14 distribution of the software without specific, written prior
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15 permission.
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16
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17 While CWI is the initial source for this software, a modified version
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18 is made available by the Corporation for National Research Initiatives
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19 (CNRI) at the Internet address ftp://ftp.python.org.
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20
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21 STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH
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22 REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
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23 MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH
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24 CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
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25 DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
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26 PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
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27 TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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28 PERFORMANCE OF THIS SOFTWARE.
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29
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30 ******************************************************************/
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31
6
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32 /* Computation of FIRST stets */
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33
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34 #include "pgenheaders.h"
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35 #include "grammar.h"
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36 #include "token.h"
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37
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38 extern int debugging;
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39
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40 /* Forward */
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41 static void calcfirstset PROTO((grammar *, dfa *));
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42
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43 void
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44 addfirstsets(g)
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45 grammar *g;
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46 {
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47 int i;
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48 dfa *d;
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49
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50 printf("Adding FIRST sets ...\n");
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51 for (i = 0; i < g->g_ndfas; i++) {
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52 d = &g->g_dfa[i];
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53 if (d->d_first == NULL)
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54 calcfirstset(g, d);
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55 }
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56 }
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57
6
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58 static void
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59 calcfirstset(g, d)
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60 grammar *g;
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61 dfa *d;
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62 {
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63 int i, j;
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64 state *s;
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65 arc *a;
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66 int nsyms;
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67 int *sym;
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68 int nbits;
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69 static bitset dummy;
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70 bitset result;
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71 int type;
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72 dfa *d1;
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73 label *l0;
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74
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75 if (debugging)
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76 printf("Calculate FIRST set for '%s'\n", d->d_name);
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77
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78 if (dummy == NULL)
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79 dummy = newbitset(1);
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80 if (d->d_first == dummy) {
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81 fprintf(stderr, "Left-recursion for '%s'\n", d->d_name);
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82 return;
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83 }
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84 if (d->d_first != NULL) {
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85 fprintf(stderr, "Re-calculating FIRST set for '%s' ???\n",
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86 d->d_name);
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87 }
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88 d->d_first = dummy;
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89
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90 l0 = g->g_ll.ll_label;
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91 nbits = g->g_ll.ll_nlabels;
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92 result = newbitset(nbits);
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93
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94 sym = NEW(int, 1);
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95 if (sym == NULL)
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96 fatal("no mem for new sym in calcfirstset");
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97 nsyms = 1;
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98 sym[0] = findlabel(&g->g_ll, d->d_type, (char *)NULL);
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99
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100 s = &d->d_state[d->d_initial];
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101 for (i = 0; i < s->s_narcs; i++) {
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102 a = &s->s_arc[i];
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103 for (j = 0; j < nsyms; j++) {
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104 if (sym[j] == a->a_lbl)
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105 break;
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106 }
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107 if (j >= nsyms) { /* New label */
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108 RESIZE(sym, int, nsyms + 1);
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109 if (sym == NULL)
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110 fatal("no mem to resize sym in calcfirstset");
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111 sym[nsyms++] = a->a_lbl;
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112 type = l0[a->a_lbl].lb_type;
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113 if (ISNONTERMINAL(type)) {
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114 d1 = finddfa(g, type);
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115 if (d1->d_first == dummy) {
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116 fprintf(stderr,
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117 "Left-recursion below '%s'\n",
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118 d->d_name);
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119 }
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120 else {
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121 if (d1->d_first == NULL)
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122 calcfirstset(g, d1);
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123 mergebitset(result, d1->d_first, nbits);
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124 }
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125 }
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126 else if (ISTERMINAL(type)) {
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127 addbit(result, a->a_lbl);
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128 }
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129 }
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130 }
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131 d->d_first = result;
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132 if (debugging) {
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133 printf("FIRST set for '%s': {", d->d_name);
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134 for (i = 0; i < nbits; i++) {
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135 if (testbit(result, i))
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136 printf(" %s", labelrepr(&l0[i]));
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137 }
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138 printf(" }\n");
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139 }
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140 }