src/gram.h

   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_ */