1 /* Data definitions for internal representation of Bison's input.
2
3 Copyright (C) 1984, 1986, 1989, 1992, 2001-2007, 2009-2012 Free
4 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 -- true iff 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
111 extern int nsyms;
112 extern int ntokens;
113 extern int nvars;
114
115 typedef int item_number;
116 #define ITEM_NUMBER_MAX INT_MAX
117 extern item_number *ritem;
118 extern unsigned int 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
128 static inline item_number
symbol_number_as_item_number(symbol_number sym)129 symbol_number_as_item_number (symbol_number sym)
130 {
131 return sym;
132 }
133
134 static inline symbol_number
item_number_as_symbol_number(item_number i)135 item_number_as_symbol_number (item_number i)
136 {
137 return i;
138 }
139
140 static inline bool
item_number_is_symbol_number(item_number i)141 item_number_is_symbol_number (item_number i)
142 {
143 return i >= 0;
144 }
145
146 /* Rule numbers. */
147 typedef int rule_number;
148 #define RULE_NUMBER_MAX INT_MAX
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. That is, it is
208 useful in the grammar. */
209 bool rule_useful_in_grammar_p (rule *r);
210
211 /* Return true IFF the rule has a `number' higher than NRULES. That is, it is
212 useless in the grammar. */
213 bool rule_useless_in_grammar_p (rule *r);
214
215 /* Return true IFF the rule is not flagged as useful but is useful in the
216 grammar. In other words, it was discarded because of conflicts. */
217 bool rule_useless_in_parser_p (rule *r);
218
219 /* Print this rule's number and lhs on OUT. If a PREVIOUS_LHS was
220 already displayed (by a previous call for another rule), avoid
221 useless repetitions. */
222 void rule_lhs_print (rule *r, symbol *previous_lhs, FILE *out);
223 void rule_lhs_print_xml (rule *r, FILE *out, int level);
224
225 /* Return the length of the RHS. */
226 int rule_rhs_length (rule *r);
227
228 /* Print this rule's RHS on OUT. */
229 void rule_rhs_print (rule *r, FILE *out);
230
231 /* Print this rule on OUT. */
232 void rule_print (rule *r, FILE *out);
233
234
235
236
237 /* Table of the symbols, indexed by the symbol number. */
238 extern symbol **symbols;
239
240 /* TOKEN_TRANSLATION -- a table indexed by a token number as returned
241 by the user's yylex routine, it yields the internal token number
242 used by the parser and throughout bison. */
243 extern symbol_number *token_translations;
244 extern int max_user_token_number;
245
246
247
248 /* Dump RITEM for traces. */
249 void ritem_print (FILE *out);
250
251 /* Return the size of the longest rule RHS. */
252 size_t ritem_longest_rhs (void);
253
254 /* Print the grammar's rules that match FILTER on OUT under TITLE. */
255 void grammar_rules_partial_print (FILE *out, const char *title,
256 rule_filter filter);
257
258 /* Print the grammar's useful rules on OUT. */
259 void grammar_rules_print (FILE *out);
260 /* Print all of the grammar's rules with a "usefulness" attribute. */
261 void grammar_rules_print_xml (FILE *out, int level);
262
263 /* Dump the grammar. */
264 void grammar_dump (FILE *out, const char *title);
265
266 /* Report on STDERR the rules that are not flagged USEFUL, using the
267 MESSAGE (which can be `rule useless in grammar' when invoked after grammar
268 reduction, or `rule useless in parser due to conflicts' after conflicts
269 were taken into account). */
270 void grammar_rules_useless_report (const char *message);
271
272 /* Free the packed grammar. */
273 void grammar_free (void);
274
275 #endif /* !GRAM_H_ */
276