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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
symbol_number_as_item_number(symbol_number sym)130 symbol_number_as_item_number (symbol_number sym)
131 {
132   return sym;
133 }
134 
135 static inline symbol_number
item_number_as_symbol_number(item_number i)136 item_number_as_symbol_number (item_number i)
137 {
138   return i;
139 }
140 
141 static inline bool
item_number_is_symbol_number(item_number i)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
rule_number_as_item_number(rule_number r)152 rule_number_as_item_number (rule_number r)
153 {
154   return -1 - r;
155 }
156 
157 static inline rule_number
item_number_as_rule_number(item_number i)158 item_number_as_rule_number (item_number i)
159 {
160   return -1 - i;
161 }
162 
163 static inline bool
item_number_is_rule_number(item_number i)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