1 /* Data definitions for internal representation of Bison's input. 2 3 Copyright (C) 1984, 1986, 1989, 1992, 2001, 2002, 2003, 2004, 2005 4 Free Software Foundation, Inc. 5 6 This file is part of Bison, the GNU Compiler Compiler. 7 8 Bison 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 2, or (at your option) 11 any later version. 12 13 Bison 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 Bison; see the file COPYING. If not, write to 20 the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, 21 Boston, MA 02110-1301, USA. */ 22 23 #ifndef GRAM_H_ 24 # define GRAM_H_ 25 26 /* Representation of the grammar rules: 27 28 NTOKENS is the number of tokens, and NVARS is the number of 29 variables (nonterminals). NSYMS is the total number, ntokens + 30 nvars. 31 32 Each symbol (either token or variable) receives a symbol number. 33 Numbers 0 to NTOKENS - 1 are for tokens, and NTOKENS to NSYMS - 1 34 are for variables. Symbol number zero is the end-of-input token. 35 This token is counted in ntokens. The true number of token values 36 assigned is NTOKENS reduced by one for each alias declaration. 37 38 The rules receive rule numbers 1 to NRULES in the order they are 39 written. More precisely Bison augments the grammar with the 40 initial rule, `$accept: START-SYMBOL $end', which is numbered 1, 41 all the user rules are 2, 3 etc. Each time a rule number is 42 presented to the user, we subtract 1, so *displayed* rule numbers 43 are 0, 1, 2... 44 45 Internally, we cannot use the number 0 for a rule because for 46 instance RITEM stores both symbol (the RHS) and rule numbers: the 47 symbols are shorts >= 0, and rule number are stored negative. 48 Therefore 0 cannot be used, since it would be both the rule number 49 0, and the token $end). 50 51 Actions are accessed via the rule number. 52 53 The rules themselves are described by several arrays: amongst which 54 RITEM, and RULES. 55 56 RULES is an array of rules, whose members are: 57 58 RULES[R].lhs -- the symbol of the left hand side of rule R. 59 60 RULES[R].rhs -- the index in RITEM of the beginning of the portion 61 for rule R. 62 63 RULES[R].prec -- the symbol providing the precedence level of R. 64 65 RULES[R].precsym -- the symbol attached (via %prec) to give its 66 precedence to R. Of course, if set, it is equal to `prec', but we 67 need to distinguish one from the other when reducing: a symbol used 68 in a %prec is not useless. 69 70 RULES[R].assoc -- the associativity of R. 71 72 RULES[R].dprec -- the dynamic precedence level of R (for GLR 73 parsing). 74 75 RULES[R].merger -- index of merging function for R (for GLR 76 parsing). 77 78 RULES[R].line -- the line where R was defined. 79 80 RULES[R].useful -- true iff the rule is used (i.e., false if thrown 81 away by reduce). 82 83 The right hand side is stored as symbol numbers in a portion of 84 RITEM. 85 86 The length of the portion is one greater than the number of symbols 87 in the rule's right hand side. The last element in the portion 88 contains minus R, which identifies it as the end of a portion and 89 says which rule it is for. 90 91 The portions of RITEM come in order of increasing rule number. 92 NRITEMS is the total length of RITEM. Each element of RITEM is 93 called an "item" and its index in RITEM is an item number. 94 95 Item numbers are used in the finite state machine to represent 96 places that parsing can get to. 97 98 SYMBOLS[I]->prec records the precedence level of each symbol. 99 100 Precedence levels are assigned in increasing order starting with 1 101 so that numerically higher precedence values mean tighter binding 102 as they ought to. Zero as a symbol or rule's precedence means none 103 is assigned. 104 105 Associativities are recorded similarly in SYMBOLS[I]->assoc. */ 106 107 # include "location.h" 108 # include "symtab.h" 109 110 # define ISTOKEN(i) ((i) < ntokens) 111 # define ISVAR(i) ((i) >= ntokens) 112 113 extern int nsyms; 114 extern int ntokens; 115 extern int nvars; 116 117 typedef int item_number; 118 extern item_number *ritem; 119 extern unsigned int nritems; 120 121 /* There is weird relationship between OT1H item_number and OTOH 122 symbol_number and rule_number: we store the latter in 123 item_number. symbol_number values are stored as-is, while 124 the negation of (rule_number + 1) is stored. 125 126 Therefore, a symbol_number must be a valid item_number, and we 127 sometimes have to perform the converse transformation. */ 128 129 static inline item_number 130 symbol_number_as_item_number (symbol_number sym) 131 { 132 return sym; 133 } 134 135 static inline symbol_number 136 item_number_as_symbol_number (item_number i) 137 { 138 return i; 139 } 140 141 static inline bool 142 item_number_is_symbol_number (item_number i) 143 { 144 return i >= 0; 145 } 146 147 /* Rule numbers. */ 148 typedef int rule_number; 149 extern rule_number nrules; 150 151 static inline item_number 152 rule_number_as_item_number (rule_number r) 153 { 154 return -1 - r; 155 } 156 157 static inline rule_number 158 item_number_as_rule_number (item_number i) 159 { 160 return -1 - i; 161 } 162 163 static inline bool 164 item_number_is_rule_number (item_number i) 165 { 166 return i < 0; 167 } 168 169 /*--------. 170 | Rules. | 171 `--------*/ 172 173 typedef struct 174 { 175 /* The number of the rule in the source. It is usually the index in 176 RULES too, except if there are useless rules. */ 177 rule_number user_number; 178 179 /* The index in RULES. Usually the rule number in the source, 180 except if some rules are useless. */ 181 rule_number number; 182 183 symbol *lhs; 184 item_number *rhs; 185 186 /* This symbol provides both the associativity, and the precedence. */ 187 symbol *prec; 188 189 int dprec; 190 int merger; 191 192 /* This symbol was attached to the rule via %prec. */ 193 symbol *precsym; 194 195 location location; 196 bool useful; 197 198 const char *action; 199 location action_location; 200 } rule; 201 202 extern rule *rules; 203 204 /* A function that selects a rule. */ 205 typedef bool (*rule_filter) (rule *); 206 207 /* Return true IFF the rule has a `number' smaller than NRULES. */ 208 bool rule_useful_p (rule *r); 209 210 /* Return true IFF the rule has a `number' higher than NRULES. */ 211 bool rule_useless_p (rule *r); 212 213 /* Return true IFF the rule is not flagged as useful *and* is useful. 214 In other words, it was discarded because of conflicts. */ 215 bool rule_never_reduced_p (rule *r); 216 217 /* Print this rule's number and lhs on OUT. If a PREVIOUS_LHS was 218 already displayed (by a previous call for another rule), avoid 219 useless repetitions. */ 220 void rule_lhs_print (rule *r, symbol *previous_lhs, FILE *out); 221 222 /* Return the length of the RHS. */ 223 int rule_rhs_length (rule *r); 224 225 /* Print this rule's RHS on OUT. */ 226 void rule_rhs_print (rule *r, FILE *out); 227 228 /* Print this rule on OUT. */ 229 void rule_print (rule *r, FILE *out); 230 231 232 233 234 /* Table of the symbols, indexed by the symbol number. */ 235 extern symbol **symbols; 236 237 /* TOKEN_TRANSLATION -- a table indexed by a token number as returned 238 by the user's yylex routine, it yields the internal token number 239 used by the parser and throughout bison. */ 240 extern symbol_number *token_translations; 241 extern int max_user_token_number; 242 243 244 245 /* Dump RITEM for traces. */ 246 void ritem_print (FILE *out); 247 248 /* Return the size of the longest rule RHS. */ 249 size_t ritem_longest_rhs (void); 250 251 /* Print the grammar's rules numbers from BEGIN (inclusive) to END 252 (exclusive) on OUT under TITLE. */ 253 void grammar_rules_partial_print (FILE *out, const char *title, 254 rule_filter filter); 255 256 /* Print the grammar's rules on OUT. */ 257 void grammar_rules_print (FILE *out); 258 259 /* Dump the grammar. */ 260 void grammar_dump (FILE *out, const char *title); 261 262 /* Report on STDERR the rules that are not flagged USEFUL, using the 263 MESSAGE (which can be `useless rule' when invoked after grammar 264 reduction, or `never reduced' after conflicts were taken into 265 account). */ 266 void grammar_rules_never_reduced_report (const char *message); 267 268 /* Free the packed grammar. */ 269 void grammar_free (void); 270 271 #endif /* !GRAM_H_ */ 272
