1 /* Data definitions for internal representation of Bison's input.
2
3 Copyright (C) 1984, 1986, 1989, 1992, 2001-2007, 2009-2015, 2018-2021
4 Free 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 #ifndef GRAM_H_
22 # define GRAM_H_
23
24 /* Representation of the grammar rules:
25
26 NTOKENS is the number of tokens, and NNTERMS is the number of
27 nonterminals (aka variables). NSYMS is the total number, NTOKENS +
28 NNTERMS.
29
30 Each symbol (either token or nterm) receives a symbol number.
31 Numbers 0 to NTOKENS - 1 are for tokens, and NTOKENS to NSYMS - 1
32 are for nterms. Symbol number zero is the end-of-input token.
33 This token is counted in ntokens. The true number of token values
34 assigned is NTOKENS reduced by one for each alias declaration.
35
36 The rules receive rule numbers 1 to NRULES in the order they are
37 written. More precisely Bison augments the grammar with the
38 initial rule, '$accept: START-SYMBOL $end', which is numbered 1,
39 all the user rules are 2, 3 etc. Each time a rule number is
40 presented to the user, we subtract 1, so *displayed* rule numbers
41 are 0, 1, 2...
42
43 Internally, we cannot use the number 0 for a rule because for
44 instance RITEM stores both symbols (the RHS) and rule numbers: the
45 symbols are integers >= 0, and rule numbers are stored negative.
46 Therefore 0 cannot be used, since it would be both the rule number
47 0, and the token $end.
48
49 Actions are accessed via the rule number.
50
51 The rules themselves are described by several arrays: amongst which
52 RITEM, and RULES.
53
54 RULES is an array of rules, whose members are:
55
56 RULES[R].lhs -- the symbol of the left hand side of rule R.
57
58 RULES[R].rhs -- the beginning of the portion of RITEM for rule R.
59
60 RULES[R].prec -- the symbol providing the precedence level of R.
61
62 RULES[R].precsym -- the symbol attached (via %prec) to give its
63 precedence to R. Of course, if set, it is equal to 'prec', but we
64 need to distinguish one from the other when reducing: a symbol used
65 in a %prec is not useless.
66
67 RULES[R].assoc -- the associativity of R.
68
69 RULES[R].dprec -- the dynamic precedence level of R (for GLR
70 parsing).
71
72 RULES[R].merger -- index of merging function for R (for GLR
73 parsing).
74
75 RULES[R].line -- the line where R was defined.
76
77 RULES[R].useful -- whether the rule is used. False if thrown away
78 by reduce().
79
80 The right hand side of rules is stored as symbol numbers in a
81 portion of RITEM.
82
83 The length of the portion is one greater than the number of symbols
84 in the rule's right hand side. The last element in the portion
85 contains -R, which identifies it as the end of a portion and says
86 which rule it is for.
87
88 The portions of RITEM come in order of increasing rule number.
89 NRITEMS is the total length of RITEM. Each element of RITEM is
90 called an "item" of type item_number and its index in RITEM is an
91 item_index.
92
93 Item numbers are used in the finite state machine to represent
94 places that parsing can get to.
95
96 SYMBOLS[I]->prec records the precedence level of each symbol.
97
98 Precedence levels are assigned in increasing order starting with 1
99 so that numerically higher precedence values mean tighter binding
100 as they ought to. Zero as a symbol or rule's precedence means none
101 is assigned.
102
103 Associativities are recorded similarly in SYMBOLS[I]->assoc. */
104
105 # include "system.h"
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 nnterms;
116
117 /* Elements of ritem. */
118 typedef int item_number;
119 # define ITEM_NUMBER_MAX INT_MAX
120 extern item_number *ritem;
121 extern int nritems;
122
123 /* Indices into ritem. */
124 typedef unsigned int item_index;
125
126 /* There is weird relationship between OT1H item_number and OTOH
127 symbol_number and rule_number: we store the latter in
128 item_number. symbol_number values are stored as-is, while
129 the negation of (rule_number + 1) is stored.
130
131 Therefore, a symbol_number must be a valid item_number, and we
132 sometimes have to perform the converse transformation. */
133
134 static inline item_number
135 symbol_number_as_item_number (symbol_number sym)
136 {
137 return sym;
138 }
139
140 static inline symbol_number
141 item_number_as_symbol_number (item_number i)
142 {
143 return i;
144 }
145
146 static inline bool
147 item_number_is_symbol_number (item_number i)
148 {
149 return i >= 0;
150 }
151
152 /* Rule numbers. */
153 typedef int rule_number;
154 # define RULE_NUMBER_MAX INT_MAX
155
156 static inline item_number
157 rule_number_as_item_number (rule_number r)
158 {
159 return -1 - r;
160 }
161
162 static inline rule_number
163 item_number_as_rule_number (item_number i)
164 {
165 return -1 - i;
166 }
167
168 static inline bool
169 item_number_is_rule_number (item_number i)
170 {
171 return i < 0;
172 }
173
174
175 /*--------.
176 | Rules. |
177 `--------*/
178
179 typedef struct
180 {
181 /* The number of the rule in the source. It is usually the index in
182 RULES too, except if there are useless rules. */
183 rule_number code;
184
185 /* The index in RULES. Usually the rule number in the source,
186 except if some rules are useless. */
187 rule_number number;
188
189 sym_content *lhs;
190 item_number *rhs;
191
192 /* This symbol provides both the associativity, and the precedence. */
193 sym_content *prec;
194
195 int dprec;
196 int merger;
197
198 /* This symbol was attached to the rule via %prec. */
199 sym_content *precsym;
200
201 /* Location of the rhs. */
202 location location;
203 bool useful;
204 bool is_predicate;
205
206 /* Counts of the numbers of expected conflicts for this rule, or -1 if none
207 given. */
208 int expected_sr_conflicts;
209 int expected_rr_conflicts;
210
211 const char *action;
212 location action_loc;
213 } rule;
214
215 /* The used rules (size NRULES). */
216 extern rule *rules;
217 extern rule_number nrules;
218
219 /* Get the rule associated to this item. ITEM points inside RITEM. */
220 static inline rule const *
221 item_rule (item_number const *item)
222 {
223 item_number const *sp = item;
224 while (!item_number_is_rule_number (*sp))
225 ++sp;
226 rule_number r = item_number_as_rule_number (*sp);
227 return &rules[r];
228 }
229
230 /* Pretty-print this ITEM (as in the report). ITEM points inside
231 RITEM. PREVIOUS_RULE is used to see if the lhs is common, in which
232 case LHS is factored. Passing NULL is fine. */
233 void item_print (item_number *item, rule const *previous_rule,
234 FILE *out);
235
236 /*--------.
237 | Rules. |
238 `--------*/
239
240 /* A function that selects a rule. */
241 typedef bool (*rule_filter) (rule const *);
242
243 /* Whether is an accepting rule (i.e., its reduction terminates
244 parsing with success). */
245 static inline bool
246 rule_is_initial (rule const *r)
247 {
248 /* In the case of multistart, we need to check whether the LHS is
249 $accept. In the case of "unistart", it would suffice to
250 check whether this is rule number 0. */
251 return r->lhs == acceptsymbol->content;
252 }
253
254 /* Whether the rule has a 'number' smaller than NRULES. That is, it
255 is useful in the grammar. */
256 bool rule_useful_in_grammar_p (rule const *r);
257
258 /* Whether the rule has a 'number' higher than NRULES. That is, it is
259 useless in the grammar. */
260 bool rule_useless_in_grammar_p (rule const *r);
261
262 /* Whether the rule is not flagged as useful but is useful in the
263 grammar. In other words, it was discarded because of conflicts. */
264 bool rule_useless_in_parser_p (rule const *r);
265
266 /* Whether the rule has a single RHS, and no user action. */
267 bool rule_useless_chain_p (rule const *r);
268
269 /* Print this rule's number and lhs on OUT. If a PREVIOUS_LHS was
270 already displayed (by a previous call for another rule), avoid
271 useless repetitions. */
272 void rule_lhs_print (rule const *r, sym_content const *previous_lhs,
273 FILE *out);
274 void rule_lhs_print_xml (rule const *r, FILE *out, int level);
275
276 /* The length of the RHS. */
277 size_t rule_rhs_length (rule const *r);
278
279 /* Print this rule's RHS on OUT. */
280 void rule_rhs_print (rule const *r, FILE *out);
281
282 /* Print this rule on OUT. If a PREVIOUS_RULE was already displayed,
283 avoid useless repetitions of their LHS. */
284 void rule_print (rule const *r, rule const *prev_rule, FILE *out);
285
286
287
288 /* Table of the symbols, indexed by the symbol number. */
289 extern symbol **symbols;
290
291 /* TOKEN_TRANSLATION -- a table indexed by a token number as returned
292 by the user's yylex routine, it yields the internal token number
293 used by the parser and throughout bison. */
294 extern symbol_number *token_translations;
295 extern int max_code;
296
297
298
299 /* Dump RITEM for traces. */
300 void ritem_print (FILE *out);
301
302 /* The size of the longest rule RHS. */
303 size_t ritem_longest_rhs (void);
304
305 /* Print the grammar's rules that match FILTER on OUT under TITLE. */
306 void grammar_rules_partial_print (FILE *out, const char *title,
307 rule_filter filter);
308
309 /* Print the grammar's useful rules on OUT. */
310 void grammar_rules_print (FILE *out);
311 /* Print all of the grammar's rules with a "usefulness" attribute. */
312 void grammar_rules_print_xml (FILE *out, int level);
313
314 /* Dump the grammar. */
315 void grammar_dump (FILE *out, const char *title);
316
317 /* Report on STDERR the rules that are not flagged USEFUL, using the
318 MESSAGE (which can be 'rule useless in grammar' when invoked after grammar
319 reduction, or 'rule useless in parser due to conflicts' after conflicts
320 were taken into account). */
321 void grammar_rules_useless_report (const char *message);
322
323 /* Free the packed grammar. */
324 void grammar_free (void);
325
326 /* The version %required by the grammar file, as an int (100 * major +
327 minor). 0 if unspecified. */
328 extern int required_version;
329
330 #endif /* !GRAM_H_ */