1/* Data definitions for internal representation of Bison's input.
2
3 Copyright (C) 1984, 1986, 1989, 1992, 2001-2007, 2009-2015, 2018-2019
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 <http://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 NVARS is the number of
27 variables (nonterminals). NSYMS is the total number, ntokens +
28 nvars.
29
30 Each symbol (either token or variable) receives a symbol number.
31 Numbers 0 to NTOKENS - 1 are for tokens, and NTOKENS to NSYMS - 1
32 are for variables. 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 symbol (the RHS) and rule numbers: the
45 symbols are shorts >= 0, and rule number 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 index in RITEM of the beginning of the portion
59 for rule R.
60
61 RULES[R].prec -- the symbol providing the precedence level of R.
62
63 RULES[R].precsym -- the symbol attached (via %prec) to give its
64 precedence to R. Of course, if set, it is equal to 'prec', but we
65 need to distinguish one from the other when reducing: a symbol used
66 in a %prec is not useless.
67
68 RULES[R].assoc -- the associativity of R.
69
70 RULES[R].dprec -- the dynamic precedence level of R (for GLR
71 parsing).
72
73 RULES[R].merger -- index of merging function for R (for GLR
74 parsing).
75
76 RULES[R].line -- the line where R was defined.
77
78 RULES[R].useful -- whether the rule is used (i.e., false if thrown
79 away by reduce).
80
81 The right hand side is stored as symbol numbers in a portion of
82 RITEM.
83
84 The length of the portion is one greater than the number of symbols
85 in the rule's right hand side. The last element in the portion
86 contains minus R, which identifies it as the end of a portion and
87 says which rule it is for.
88
89 The portions of RITEM come in order of increasing rule number.
90 NRITEMS is the total length of RITEM. Each element of RITEM is
91 called an "item" and its index in RITEM is an item number.
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 "location.h"
106# include "symtab.h"
107
108# define ISTOKEN(i) ((i) < ntokens)
109# define ISVAR(i) ((i) >= ntokens)
110
111extern int nsyms;
112extern int ntokens;
113extern int nvars;
114
115typedef int item_number;
116# define ITEM_NUMBER_MAX INT_MAX
117extern item_number *ritem;
118extern unsigned nritems;
119
120/* There is weird relationship between OT1H item_number and OTOH
121 symbol_number and rule_number: we store the latter in
122 item_number. symbol_number values are stored as-is, while
123 the negation of (rule_number + 1) is stored.
124
125 Therefore, a symbol_number must be a valid item_number, and we
126 sometimes have to perform the converse transformation. */
127
128static inline item_number
129symbol_number_as_item_number (symbol_number sym)
130{
131 return sym;
132}
133
134static inline symbol_number
135item_number_as_symbol_number (item_number i)
136{
137 return i;
138}
139
140static inline bool
141item_number_is_symbol_number (item_number i)
142{
143 return i >= 0;
144}
145
146/* Rule numbers. */
147typedef int rule_number;
148# define RULE_NUMBER_MAX INT_MAX
149
150static inline item_number
151rule_number_as_item_number (rule_number r)
152{
153 return -1 - r;
154}
155
156static inline rule_number
157item_number_as_rule_number (item_number i)
158{
159 return -1 - i;
160}
161
162static inline bool
163item_number_is_rule_number (item_number i)
164{
165 return i < 0;
166}
167
168
169/*--------.
170| Rules. |
171`--------*/
172
173typedef 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 sym_content *lhs;
184 item_number *rhs;
185
186 /* This symbol provides both the associativity, and the precedence. */
187 sym_content *prec;
188
189 int dprec;
190 int merger;
191
192 /* This symbol was attached to the rule via %prec. */
193 sym_content *precsym;
194
195 /* Location of the rhs. */
196 location location;
197 bool useful;
198 bool is_predicate;
199
200 /* Counts of the numbers of expected conflicts for this rule, or -1 if none
201 given. */
202 int expected_sr_conflicts;
203 int expected_rr_conflicts;
204
205 const char *action;
206 location action_loc;
207} rule;
208
209/* The used rules (size NRULES). */
210extern rule *rules;
211extern rule_number nrules;
212
213/* Get the rule associated to this item. ITEM points inside RITEM. */
214rule const *item_rule (item_number const *item);
215
216/* Pretty-print this ITEM (as in the report). ITEM points inside
217 RITEM. PREVIOUS_RULE is used to see if the lhs is common, in which
218 case LHS is factored. Passing NULL is fine. */
219void item_print (item_number *item, rule const *previous_rule,
220 FILE *out);
221
222/* A function that selects a rule. */
223typedef bool (*rule_filter) (rule const *);
224
225/* Whether the rule has a 'number' smaller than NRULES. That is, it
226 is useful in the grammar. */
227bool rule_useful_in_grammar_p (rule const *r);
228
229/* Whether the rule has a 'number' higher than NRULES. That is, it is
230 useless in the grammar. */
231bool rule_useless_in_grammar_p (rule const *r);
232
233/* Whether the rule is not flagged as useful but is useful in the
234 grammar. In other words, it was discarded because of conflicts. */
235bool rule_useless_in_parser_p (rule const *r);
236
237/* Whether the rule has a single RHS, and no user action. */
238bool rule_useless_chain_p (rule const *r);
239
240/* Print this rule's number and lhs on OUT. If a PREVIOUS_LHS was
241 already displayed (by a previous call for another rule), avoid
242 useless repetitions. */
243void rule_lhs_print (rule const *r, sym_content const *previous_lhs,
244 FILE *out);
245void rule_lhs_print_xml (rule const *r, FILE *out, int level);
246
247/* The length of the RHS. */
248size_t rule_rhs_length (rule const *r);
249
250/* Print this rule's RHS on OUT. */
251void rule_rhs_print (rule const *r, FILE *out);
252
253/* Print this rule on OUT. If a PREVIOUS_RULE was already displayed,
254 avoid useless repetitions of their LHS. */
255void rule_print (rule const *r, rule const *prev_rule, FILE *out);
256
257
258
259/* Table of the symbols, indexed by the symbol number. */
260extern symbol **symbols;
261
262/* TOKEN_TRANSLATION -- a table indexed by a token number as returned
263 by the user's yylex routine, it yields the internal token number
264 used by the parser and throughout bison. */
265extern symbol_number *token_translations;
266extern int max_user_token_number;
267
268
269
270/* Dump RITEM for traces. */
271void ritem_print (FILE *out);
272
273/* The size of the longest rule RHS. */
274size_t ritem_longest_rhs (void);
275
276/* Print the grammar's rules that match FILTER on OUT under TITLE. */
277void grammar_rules_partial_print (FILE *out, const char *title,
278 rule_filter filter);
279
280/* Print the grammar's useful rules on OUT. */
281void grammar_rules_print (FILE *out);
282/* Print all of the grammar's rules with a "usefulness" attribute. */
283void grammar_rules_print_xml (FILE *out, int level);
284
285/* Dump the grammar. */
286void grammar_dump (FILE *out, const char *title);
287
288/* Report on STDERR the rules that are not flagged USEFUL, using the
289 MESSAGE (which can be 'rule useless in grammar' when invoked after grammar
290 reduction, or 'rule useless in parser due to conflicts' after conflicts
291 were taken into account). */
292void grammar_rules_useless_report (const char *message);
293
294/* Free the packed grammar. */
295void grammar_free (void);
296
297/* The version %required by the grammar file, as an int (100 * major +
298 minor). 0 if unspecified. */
299extern int required_version;
300
301#endif /* !GRAM_H_ */
302