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1 GNU Bison NEWS
2
3 * Noteworthy changes in release ?.? (????-??-??) [?]
4
5
6 * Noteworthy changes in release 3.0.2 (2013-12-05) [stable]
7
8 ** Bug fixes
9
10 *** Generated source files when errors are reported
11
12 When warnings are issued and -Werror is set, bison would still generate
13 the source files (*.c, *.h...). As a consequence, some runs of "make"
14 could fail the first time, but not the second (as the files were generated
15 anyway).
16
17 This is fixed: bison no longer generates this source files, but, of
18 course, still produces the various reports (*.output, *.xml, etc.).
19
20 *** %empty is used in reports
21
22 Empty right-hand sides are denoted by '%empty' in all the reports (text,
23 dot, XML and formats derived from it).
24
25 *** YYERROR and variants
26
27 When C++ variant support is enabled, an error triggered via YYERROR, but
28 not caught via error recovery, resulted in a double deletion.
29
30 * Noteworthy changes in release 3.0.1 (2013-11-12) [stable]
31
32 ** Bug fixes
33
34 *** Errors in caret diagnostics
35
36 On some platforms, some errors could result in endless diagnostics.
37
38 *** Fixes of the -Werror option
39
40 Options such as "-Werror -Wno-error=foo" were still turning "foo"
41 diagnostics into errors instead of warnings. This is fixed.
42
43 Actually, for consistency with GCC, "-Wno-error=foo -Werror" now also
44 leaves "foo" diagnostics as warnings. Similarly, with "-Werror=foo
45 -Wno-error", "foo" diagnostics are now errors.
46
47 *** GLR Predicates
48
49 As demonstrated in the documentation, one can now leave spaces between
50 "%?" and its "{".
51
52 *** Installation
53
54 The yacc.1 man page is no longer installed if --disable-yacc was
55 specified.
56
57 *** Fixes in the test suite
58
59 Bugs and portability issues.
60
61 * Noteworthy changes in release 3.0 (2013-07-25) [stable]
62
63 ** WARNING: Future backward-incompatibilities!
64
65 Like other GNU packages, Bison will start using some of the C99 features
66 for its own code, especially the definition of variables after statements.
67 The generated C parsers still aim at C90.
68
69 ** Backward incompatible changes
70
71 *** Obsolete features
72
73 Support for YYFAIL is removed (deprecated in Bison 2.4.2): use YYERROR.
74
75 Support for yystype and yyltype is removed (deprecated in Bison 1.875):
76 use YYSTYPE and YYLTYPE.
77
78 Support for YYLEX_PARAM and YYPARSE_PARAM is removed (deprecated in Bison
79 1.875): use %lex-param, %parse-param, or %param.
80
81 Missing semicolons at the end of actions are no longer added (as announced
82 in the release 2.5).
83
84 *** Use of YACC='bison -y'
85
86 TL;DR: With Autoconf <= 2.69, pass -Wno-yacc to (AM_)YFLAGS if you use
87 Bison extensions.
88
89 Traditional Yacc generates 'y.tab.c' whatever the name of the input file.
90 Therefore Makefiles written for Yacc expect 'y.tab.c' (and possibly
91 'y.tab.h' and 'y.outout') to be generated from 'foo.y'.
92
93 To this end, for ages, AC_PROG_YACC, Autoconf's macro to look for an
94 implementation of Yacc, was using Bison as 'bison -y'. While it does
95 ensure compatible output file names, it also enables warnings for
96 incompatibilities with POSIX Yacc. In other words, 'bison -y' triggers
97 warnings for Bison extensions.
98
99 Autoconf 2.70+ fixes this incompatibility by using YACC='bison -o y.tab.c'
100 (which also generates 'y.tab.h' and 'y.output' when needed).
101 Alternatively, disable Yacc warnings by passing '-Wno-yacc' to your Yacc
102 flags (YFLAGS, or AM_YFLAGS with Automake).
103
104 ** Bug fixes
105
106 *** The epilogue is no longer affected by internal #defines (glr.c)
107
108 The glr.c skeleton uses defines such as #define yylval (yystackp->yyval) in
109 generated code. These weren't properly undefined before the inclusion of
110 the user epilogue, so functions such as the following were butchered by the
111 preprocessor expansion:
112
113 int yylex (YYSTYPE *yylval);
114
115 This is fixed: yylval, yynerrs, yychar, and yylloc are now valid
116 identifiers for user-provided variables.
117
118 *** stdio.h is no longer needed when locations are enabled (yacc.c)
119
120 Changes in Bison 2.7 introduced a dependency on FILE and fprintf when
121 locations are enabled. This is fixed.
122
123 *** Warnings about useless %pure-parser/%define api.pure are restored
124
125 ** Diagnostics reported by Bison
126
127 Most of these features were contributed by Théophile Ranquet and Victor
128 Santet.
129
130 *** Carets
131
132 Version 2.7 introduced caret errors, for a prettier output. These are now
133 activated by default. The old format can still be used by invoking Bison
134 with -fno-caret (or -fnone).
135
136 Some error messages that reproduced excerpts of the grammar are now using
137 the caret information only. For instance on:
138
139 %%
140 exp: 'a' | 'a';
141
142 Bison 2.7 reports:
143
144 in.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
145 in.y:2.12-14: warning: rule useless in parser due to conflicts: exp: 'a' [-Wother]
146
147 Now bison reports:
148
149 in.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
150 in.y:2.12-14: warning: rule useless in parser due to conflicts [-Wother]
151 exp: 'a' | 'a';
152 ^^^
153
154 and "bison -fno-caret" reports:
155
156 in.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
157 in.y:2.12-14: warning: rule useless in parser due to conflicts [-Wother]
158
159 *** Enhancements of the -Werror option
160
161 The -Werror=CATEGORY option is now recognized, and will treat specified
162 warnings as errors. The warnings need not have been explicitly activated
163 using the -W option, this is similar to what GCC 4.7 does.
164
165 For example, given the following command line, Bison will treat both
166 warnings related to POSIX Yacc incompatibilities and S/R conflicts as
167 errors (and only those):
168
169 $ bison -Werror=yacc,error=conflicts-sr input.y
170
171 If no categories are specified, -Werror will make all active warnings into
172 errors. For example, the following line does the same the previous example:
173
174 $ bison -Werror -Wnone -Wyacc -Wconflicts-sr input.y
175
176 (By default -Wconflicts-sr,conflicts-rr,deprecated,other is enabled.)
177
178 Note that the categories in this -Werror option may not be prefixed with
179 "no-". However, -Wno-error[=CATEGORY] is valid.
180
181 Note that -y enables -Werror=yacc. Therefore it is now possible to require
182 Yacc-like behavior (e.g., always generate y.tab.c), but to report
183 incompatibilities as warnings: "-y -Wno-error=yacc".
184
185 *** The display of warnings is now richer
186
187 The option that controls a given warning is now displayed:
188
189 foo.y:4.6: warning: type clash on default action: <foo> != <bar> [-Wother]
190
191 In the case of warnings treated as errors, the prefix is changed from
192 "warning: " to "error: ", and the suffix is displayed, in a manner similar
193 to GCC, as [-Werror=CATEGORY].
194
195 For instance, where the previous version of Bison would report (and exit
196 with failure):
197
198 bison: warnings being treated as errors
199 input.y:1.1: warning: stray ',' treated as white space
200
201 it now reports:
202
203 input.y:1.1: error: stray ',' treated as white space [-Werror=other]
204
205 *** Deprecated constructs
206
207 The new 'deprecated' warning category flags obsolete constructs whose
208 support will be discontinued. It is enabled by default. These warnings
209 used to be reported as 'other' warnings.
210
211 *** Useless semantic types
212
213 Bison now warns about useless (uninhabited) semantic types. Since
214 semantic types are not declared to Bison (they are defined in the opaque
215 %union structure), it is %printer/%destructor directives about useless
216 types that trigger the warning:
217
218 %token <type1> term
219 %type <type2> nterm
220 %printer {} <type1> <type3>
221 %destructor {} <type2> <type4>
222 %%
223 nterm: term { $$ = $1; };
224
225 3.28-34: warning: type <type3> is used, but is not associated to any symbol
226 4.28-34: warning: type <type4> is used, but is not associated to any symbol
227
228 *** Undefined but unused symbols
229
230 Bison used to raise an error for undefined symbols that are not used in
231 the grammar. This is now only a warning.
232
233 %printer {} symbol1
234 %destructor {} symbol2
235 %type <type> symbol3
236 %%
237 exp: "a";
238
239 *** Useless destructors or printers
240
241 Bison now warns about useless destructors or printers. In the following
242 example, the printer for <type1>, and the destructor for <type2> are
243 useless: all symbols of <type1> (token1) already have a printer, and all
244 symbols of type <type2> (token2) already have a destructor.
245
246 %token <type1> token1
247 <type2> token2
248 <type3> token3
249 <type4> token4
250 %printer {} token1 <type1> <type3>
251 %destructor {} token2 <type2> <type4>
252
253 *** Conflicts
254
255 The warnings and error messages about shift/reduce and reduce/reduce
256 conflicts have been normalized. For instance on the following foo.y file:
257
258 %glr-parser
259 %%
260 exp: exp '+' exp | '0' | '0';
261
262 compare the previous version of bison:
263
264 $ bison foo.y
265 foo.y: conflicts: 1 shift/reduce, 2 reduce/reduce
266 $ bison -Werror foo.y
267 bison: warnings being treated as errors
268 foo.y: conflicts: 1 shift/reduce, 2 reduce/reduce
269
270 with the new behavior:
271
272 $ bison foo.y
273 foo.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
274 foo.y: warning: 2 reduce/reduce conflicts [-Wconflicts-rr]
275 $ bison -Werror foo.y
276 foo.y: error: 1 shift/reduce conflict [-Werror=conflicts-sr]
277 foo.y: error: 2 reduce/reduce conflicts [-Werror=conflicts-rr]
278
279 When %expect or %expect-rr is used, such as with bar.y:
280
281 %expect 0
282 %glr-parser
283 %%
284 exp: exp '+' exp | '0' | '0';
285
286 Former behavior:
287
288 $ bison bar.y
289 bar.y: conflicts: 1 shift/reduce, 2 reduce/reduce
290 bar.y: expected 0 shift/reduce conflicts
291 bar.y: expected 0 reduce/reduce conflicts
292
293 New one:
294
295 $ bison bar.y
296 bar.y: error: shift/reduce conflicts: 1 found, 0 expected
297 bar.y: error: reduce/reduce conflicts: 2 found, 0 expected
298
299 ** Incompatibilities with POSIX Yacc
300
301 The 'yacc' category is no longer part of '-Wall', enable it explicitly
302 with '-Wyacc'.
303
304 ** Additional yylex/yyparse arguments
305
306 The new directive %param declares additional arguments to both yylex and
307 yyparse. The %lex-param, %parse-param, and %param directives support one
308 or more arguments. Instead of
309
310 %lex-param {arg1_type *arg1}
311 %lex-param {arg2_type *arg2}
312 %parse-param {arg1_type *arg1}
313 %parse-param {arg2_type *arg2}
314
315 one may now declare
316
317 %param {arg1_type *arg1} {arg2_type *arg2}
318
319 ** Types of values for %define variables
320
321 Bison used to make no difference between '%define foo bar' and '%define
322 foo "bar"'. The former is now called a 'keyword value', and the latter a
323 'string value'. A third kind was added: 'code values', such as '%define
324 foo {bar}'.
325
326 Keyword variables are used for fixed value sets, e.g.,
327
328 %define lr.type lalr
329
330 Code variables are used for value in the target language, e.g.,
331
332 %define api.value.type {struct semantic_type}
333
334 String variables are used remaining cases, e.g. file names.
335
336 ** Variable api.token.prefix
337
338 The variable api.token.prefix changes the way tokens are identified in
339 the generated files. This is especially useful to avoid collisions
340 with identifiers in the target language. For instance
341
342 %token FILE for ERROR
343 %define api.token.prefix {TOK_}
344 %%
345 start: FILE for ERROR;
346
347 will generate the definition of the symbols TOK_FILE, TOK_for, and
348 TOK_ERROR in the generated sources. In particular, the scanner must
349 use these prefixed token names, although the grammar itself still
350 uses the short names (as in the sample rule given above).
351
352 ** Variable api.value.type
353
354 This new %define variable supersedes the #define macro YYSTYPE. The use
355 of YYSTYPE is discouraged. In particular, #defining YYSTYPE *and* either
356 using %union or %defining api.value.type results in undefined behavior.
357
358 Either define api.value.type, or use "%union":
359
360 %union
361 {
362 int ival;
363 char *sval;
364 }
365 %token <ival> INT "integer"
366 %token <sval> STRING "string"
367 %printer { fprintf (yyo, "%d", $$); } <ival>
368 %destructor { free ($$); } <sval>
369
370 /* In yylex(). */
371 yylval.ival = 42; return INT;
372 yylval.sval = "42"; return STRING;
373
374 The %define variable api.value.type supports both keyword and code values.
375
376 The keyword value 'union' means that the user provides genuine types, not
377 union member names such as "ival" and "sval" above (WARNING: will fail if
378 -y/--yacc/%yacc is enabled).
379
380 %define api.value.type union
381 %token <int> INT "integer"
382 %token <char *> STRING "string"
383 %printer { fprintf (yyo, "%d", $$); } <int>
384 %destructor { free ($$); } <char *>
385
386 /* In yylex(). */
387 yylval.INT = 42; return INT;
388 yylval.STRING = "42"; return STRING;
389
390 The keyword value variant is somewhat equivalent, but for C++ special
391 provision is made to allow classes to be used (more about this below).
392
393 %define api.value.type variant
394 %token <int> INT "integer"
395 %token <std::string> STRING "string"
396
397 Code values (in braces) denote user defined types. This is where YYSTYPE
398 used to be used.
399
400 %code requires
401 {
402 struct my_value
403 {
404 enum
405 {
406 is_int, is_string
407 } kind;
408 union
409 {
410 int ival;
411 char *sval;
412 } u;
413 };
414 }
415 %define api.value.type {struct my_value}
416 %token <u.ival> INT "integer"
417 %token <u.sval> STRING "string"
418 %printer { fprintf (yyo, "%d", $$); } <u.ival>
419 %destructor { free ($$); } <u.sval>
420
421 /* In yylex(). */
422 yylval.u.ival = 42; return INT;
423 yylval.u.sval = "42"; return STRING;
424
425 ** Variable parse.error
426
427 This variable controls the verbosity of error messages. The use of the
428 %error-verbose directive is deprecated in favor of "%define parse.error
429 verbose".
430
431 ** Renamed %define variables
432
433 The following variables have been renamed for consistency. Backward
434 compatibility is ensured, but upgrading is recommended.
435
436 lr.default-reductions -> lr.default-reduction
437 lr.keep-unreachable-states -> lr.keep-unreachable-state
438 namespace -> api.namespace
439 stype -> api.value.type
440
441 ** Semantic predicates
442
443 Contributed by Paul Hilfinger.
444
445 The new, experimental, semantic-predicate feature allows actions of the
446 form "%?{ BOOLEAN-EXPRESSION }", which cause syntax errors (as for
447 YYERROR) if the expression evaluates to 0, and are evaluated immediately
448 in GLR parsers, rather than being deferred. The result is that they allow
449 the programmer to prune possible parses based on the values of run-time
450 expressions.
451
452 ** The directive %expect-rr is now an error in non GLR mode
453
454 It used to be an error only if used in non GLR mode, _and_ if there are
455 reduce/reduce conflicts.
456
457 ** Tokens are numbered in their order of appearance
458
459 Contributed by Valentin Tolmer.
460
461 With '%token A B', A had a number less than the one of B. However,
462 precedence declarations used to generate a reversed order. This is now
463 fixed, and introducing tokens with any of %token, %left, %right,
464 %precedence, or %nonassoc yields the same result.
465
466 When mixing declarations of tokens with a litteral character (e.g., 'a')
467 or with an identifier (e.g., B) in a precedence declaration, Bison
468 numbered the litteral characters first. For example
469
470 %right A B 'c' 'd'
471
472 would lead to the tokens declared in this order: 'c' 'd' A B. Again, the
473 input order is now preserved.
474
475 These changes were made so that one can remove useless precedence and
476 associativity declarations (i.e., map %nonassoc, %left or %right to
477 %precedence, or to %token) and get exactly the same output.
478
479 ** Useless precedence and associativity
480
481 Contributed by Valentin Tolmer.
482
483 When developing and maintaining a grammar, useless associativity and
484 precedence directives are common. They can be a nuisance: new ambiguities
485 arising are sometimes masked because their conflicts are resolved due to
486 the extra precedence or associativity information. Furthermore, it can
487 hinder the comprehension of a new grammar: one will wonder about the role
488 of a precedence, where in fact it is useless. The following changes aim
489 at detecting and reporting these extra directives.
490
491 *** Precedence warning category
492
493 A new category of warning, -Wprecedence, was introduced. It flags the
494 useless precedence and associativity directives.
495
496 *** Useless associativity
497
498 Bison now warns about symbols with a declared associativity that is never
499 used to resolve conflicts. In that case, using %precedence is sufficient;
500 the parsing tables will remain unchanged. Solving these warnings may raise
501 useless precedence warnings, as the symbols no longer have associativity.
502 For example:
503
504 %left '+'
505 %left '*'
506 %%
507 exp:
508 "number"
509 | exp '+' "number"
510 | exp '*' exp
511 ;
512
513 will produce a
514
515 warning: useless associativity for '+', use %precedence [-Wprecedence]
516 %left '+'
517 ^^^
518
519 *** Useless precedence
520
521 Bison now warns about symbols with a declared precedence and no declared
522 associativity (i.e., declared with %precedence), and whose precedence is
523 never used. In that case, the symbol can be safely declared with %token
524 instead, without modifying the parsing tables. For example:
525
526 %precedence '='
527 %%
528 exp: "var" '=' "number";
529
530 will produce a
531
532 warning: useless precedence for '=' [-Wprecedence]
533 %precedence '='
534 ^^^
535
536 *** Useless precedence and associativity
537
538 In case of both useless precedence and associativity, the issue is flagged
539 as follows:
540
541 %nonassoc '='
542 %%
543 exp: "var" '=' "number";
544
545 The warning is:
546
547 warning: useless precedence and associativity for '=' [-Wprecedence]
548 %nonassoc '='
549 ^^^
550
551 ** Empty rules
552
553 With help from Joel E. Denny and Gabriel Rassoul.
554
555 Empty rules (i.e., with an empty right-hand side) can now be explicitly
556 marked by the new %empty directive. Using %empty on a non-empty rule is
557 an error. The new -Wempty-rule warning reports empty rules without
558 %empty. On the following grammar:
559
560 %%
561 s: a b c;
562 a: ;
563 b: %empty;
564 c: 'a' %empty;
565
566 bison reports:
567
568 3.4-5: warning: empty rule without %empty [-Wempty-rule]
569 a: {}
570 ^^
571 5.8-13: error: %empty on non-empty rule
572 c: 'a' %empty {};
573 ^^^^^^
574
575 ** Java skeleton improvements
576
577 The constants for token names were moved to the Lexer interface. Also, it
578 is possible to add code to the parser's constructors using "%code init"
579 and "%define init_throws".
580 Contributed by Paolo Bonzini.
581
582 The Java skeleton now supports push parsing.
583 Contributed by Dennis Heimbigner.
584
585 ** C++ skeletons improvements
586
587 *** The parser header is no longer mandatory (lalr1.cc, glr.cc)
588
589 Using %defines is now optional. Without it, the needed support classes
590 are defined in the generated parser, instead of additional files (such as
591 location.hh, position.hh and stack.hh).
592
593 *** Locations are no longer mandatory (lalr1.cc, glr.cc)
594
595 Both lalr1.cc and glr.cc no longer require %location.
596
597 *** syntax_error exception (lalr1.cc)
598
599 The C++ parser features a syntax_error exception, which can be
600 thrown from the scanner or from user rules to raise syntax errors.
601 This facilitates reporting errors caught in sub-functions (e.g.,
602 rejecting too large integral literals from a conversion function
603 used by the scanner, or rejecting invalid combinations from a
604 factory invoked by the user actions).
605
606 *** %define api.value.type variant
607
608 This is based on a submission from Michiel De Wilde. With help
609 from Théophile Ranquet.
610
611 In this mode, complex C++ objects can be used as semantic values. For
612 instance:
613
614 %token <::std::string> TEXT;
615 %token <int> NUMBER;
616 %token SEMICOLON ";"
617 %type <::std::string> item;
618 %type <::std::list<std::string>> list;
619 %%
620 result:
621 list { std::cout << $1 << std::endl; }
622 ;
623
624 list:
625 %empty { /* Generates an empty string list. */ }
626 | list item ";" { std::swap ($$, $1); $$.push_back ($2); }
627 ;
628
629 item:
630 TEXT { std::swap ($$, $1); }
631 | NUMBER { $$ = string_cast ($1); }
632 ;
633
634 *** %define api.token.constructor
635
636 When variants are enabled, Bison can generate functions to build the
637 tokens. This guarantees that the token type (e.g., NUMBER) is consistent
638 with the semantic value (e.g., int):
639
640 parser::symbol_type yylex ()
641 {
642 parser::location_type loc = ...;
643 ...
644 return parser::make_TEXT ("Hello, world!", loc);
645 ...
646 return parser::make_NUMBER (42, loc);
647 ...
648 return parser::make_SEMICOLON (loc);
649 ...
650 }
651
652 *** C++ locations
653
654 There are operator- and operator-= for 'location'. Negative line/column
655 increments can no longer underflow the resulting value.
656
657 * Noteworthy changes in release 2.7.1 (2013-04-15) [stable]
658
659 ** Bug fixes
660
661 *** Fix compiler attribute portability (yacc.c)
662
663 With locations enabled, __attribute__ was used unprotected.
664
665 *** Fix some compiler warnings (lalr1.cc)
666
667 * Noteworthy changes in release 2.7 (2012-12-12) [stable]
668
669 ** Bug fixes
670
671 Warnings about uninitialized yylloc in yyparse have been fixed.
672
673 Restored C90 compliance (yet no report was ever made).
674
675 ** Diagnostics are improved
676
677 Contributed by Théophile Ranquet.
678
679 *** Changes in the format of error messages
680
681 This used to be the format of many error reports:
682
683 input.y:2.7-12: %type redeclaration for exp
684 input.y:1.7-12: previous declaration
685
686 It is now:
687
688 input.y:2.7-12: error: %type redeclaration for exp
689 input.y:1.7-12: previous declaration
690
691 *** New format for error reports: carets
692
693 Caret errors have been added to Bison:
694
695 input.y:2.7-12: error: %type redeclaration for exp
696 %type <sval> exp
697 ^^^^^^
698 input.y:1.7-12: previous declaration
699 %type <ival> exp
700 ^^^^^^
701
702 or
703
704 input.y:3.20-23: error: ambiguous reference: '$exp'
705 exp: exp '+' exp { $exp = $1 + $3; };
706 ^^^^
707 input.y:3.1-3: refers to: $exp at $$
708 exp: exp '+' exp { $exp = $1 + $3; };
709 ^^^
710 input.y:3.6-8: refers to: $exp at $1
711 exp: exp '+' exp { $exp = $1 + $3; };
712 ^^^
713 input.y:3.14-16: refers to: $exp at $3
714 exp: exp '+' exp { $exp = $1 + $3; };
715 ^^^
716
717 The default behavior for now is still not to display these unless
718 explicitly asked with -fcaret (or -fall). However, in a later release, it
719 will be made the default behavior (but may still be deactivated with
720 -fno-caret).
721
722 ** New value for %define variable: api.pure full
723
724 The %define variable api.pure requests a pure (reentrant) parser. However,
725 for historical reasons, using it in a location-tracking Yacc parser
726 resulted in a yyerror function that did not take a location as a
727 parameter. With this new value, the user may request a better pure parser,
728 where yyerror does take a location as a parameter (in location-tracking
729 parsers).
730
731 The use of "%define api.pure true" is deprecated in favor of this new
732 "%define api.pure full".
733
734 ** New %define variable: api.location.type (glr.cc, lalr1.cc, lalr1.java)
735
736 The %define variable api.location.type defines the name of the type to use
737 for locations. When defined, Bison no longer generates the position.hh
738 and location.hh files, nor does the parser will include them: the user is
739 then responsible to define her type.
740
741 This can be used in programs with several parsers to factor their location
742 and position files: let one of them generate them, and the others just use
743 them.
744
745 This feature was actually introduced, but not documented, in Bison 2.5,
746 under the name "location_type" (which is maintained for backward
747 compatibility).
748
749 For consistency, lalr1.java's %define variables location_type and
750 position_type are deprecated in favor of api.location.type and
751 api.position.type.
752
753 ** Exception safety (lalr1.cc)
754
755 The parse function now catches exceptions, uses the %destructors to
756 release memory (the lookahead symbol and the symbols pushed on the stack)
757 before re-throwing the exception.
758
759 This feature is somewhat experimental. User feedback would be
760 appreciated.
761
762 ** Graph improvements in DOT and XSLT
763
764 Contributed by Théophile Ranquet.
765
766 The graphical presentation of the states is more readable: their shape is
767 now rectangular, the state number is clearly displayed, and the items are
768 numbered and left-justified.
769
770 The reductions are now explicitly represented as transitions to other
771 diamond shaped nodes.
772
773 These changes are present in both --graph output and xml2dot.xsl XSLT
774 processing, with minor (documented) differences.
775
776 ** %language is no longer an experimental feature.
777
778 The introduction of this feature, in 2.4, was four years ago. The
779 --language option and the %language directive are no longer experimental.
780
781 ** Documentation
782
783 The sections about shift/reduce and reduce/reduce conflicts resolution
784 have been fixed and extended.
785
786 Although introduced more than four years ago, XML and Graphviz reports
787 were not properly documented.
788
789 The translation of mid-rule actions is now described.
790
791 * Noteworthy changes in release 2.6.5 (2012-11-07) [stable]
792
793 We consider compiler warnings about Bison generated parsers to be bugs.
794 Rather than working around them in your own project, please consider
795 reporting them to us.
796
797 ** Bug fixes
798
799 Warnings about uninitialized yylval and/or yylloc for push parsers with a
800 pure interface have been fixed for GCC 4.0 up to 4.8, and Clang 2.9 to
801 3.2.
802
803 Other issues in the test suite have been addressed.
804
805 Null characters are correctly displayed in error messages.
806
807 When possible, yylloc is correctly initialized before calling yylex. It
808 is no longer necessary to initialize it in the %initial-action.
809
810 * Noteworthy changes in release 2.6.4 (2012-10-23) [stable]
811
812 Bison 2.6.3's --version was incorrect. This release fixes this issue.
813
814 * Noteworthy changes in release 2.6.3 (2012-10-22) [stable]
815
816 ** Bug fixes
817
818 Bugs and portability issues in the test suite have been fixed.
819
820 Some errors in translations have been addressed, and --help now directs
821 users to the appropriate place to report them.
822
823 Stray Info files shipped by accident are removed.
824
825 Incorrect definitions of YY_, issued by yacc.c when no parser header is
826 generated, are removed.
827
828 All the generated headers are self-contained.
829
830 ** Header guards (yacc.c, glr.c, glr.cc)
831
832 In order to avoid collisions, the header guards are now
833 YY_<PREFIX>_<FILE>_INCLUDED, instead of merely <PREFIX>_<FILE>.
834 For instance the header generated from
835
836 %define api.prefix "calc"
837 %defines "lib/parse.h"
838
839 will use YY_CALC_LIB_PARSE_H_INCLUDED as guard.
840
841 ** Fix compiler warnings in the generated parser (yacc.c, glr.c)
842
843 The compilation of pure parsers (%define api.pure) can trigger GCC
844 warnings such as:
845
846 input.c: In function 'yyparse':
847 input.c:1503:12: warning: 'yylval' may be used uninitialized in this
848 function [-Wmaybe-uninitialized]
849 *++yyvsp = yylval;
850 ^
851
852 This is now fixed; pragmas to avoid these warnings are no longer needed.
853
854 Warnings from clang ("equality comparison with extraneous parentheses" and
855 "function declared 'noreturn' should not return") have also been
856 addressed.
857
858 * Noteworthy changes in release 2.6.2 (2012-08-03) [stable]
859
860 ** Bug fixes
861
862 Buffer overruns, complaints from Flex, and portability issues in the test
863 suite have been fixed.
864
865 ** Spaces in %lex- and %parse-param (lalr1.cc, glr.cc)
866
867 Trailing end-of-lines in %parse-param or %lex-param would result in
868 invalid C++. This is fixed.
869
870 ** Spurious spaces and end-of-lines
871
872 The generated files no longer end (nor start) with empty lines.
873
874 * Noteworthy changes in release 2.6.1 (2012-07-30) [stable]
875
876 Bison no longer executes user-specified M4 code when processing a grammar.
877
878 ** Future Changes
879
880 In addition to the removal of the features announced in Bison 2.6, the
881 next major release will remove the "Temporary hack for adding a semicolon
882 to the user action", as announced in the release 2.5. Instead of:
883
884 exp: exp "+" exp { $$ = $1 + $3 };
885
886 write:
887
888 exp: exp "+" exp { $$ = $1 + $3; };
889
890 ** Bug fixes
891
892 *** Type names are now properly escaped.
893
894 *** glr.cc: set_debug_level and debug_level work as expected.
895
896 *** Stray @ or $ in actions
897
898 While Bison used to warn about stray $ or @ in action rules, it did not
899 for other actions such as printers, destructors, or initial actions. It
900 now does.
901
902 ** Type names in actions
903
904 For consistency with rule actions, it is now possible to qualify $$ by a
905 type-name in destructors, printers, and initial actions. For instance:
906
907 %printer { fprintf (yyo, "(%d, %f)", $<ival>$, $<fval>$); } <*> <>;
908
909 will display two values for each typed and untyped symbol (provided
910 that YYSTYPE has both "ival" and "fval" fields).
911
912 * Noteworthy changes in release 2.6 (2012-07-19) [stable]
913
914 ** Future changes
915
916 The next major release of Bison will drop support for the following
917 deprecated features. Please report disagreements to bug-bison@gnu.org.
918
919 *** K&R C parsers
920
921 Support for generating parsers in K&R C will be removed. Parsers
922 generated for C support ISO C90, and are tested with ISO C99 and ISO C11
923 compilers.
924
925 *** Features deprecated since Bison 1.875
926
927 The definitions of yystype and yyltype will be removed; use YYSTYPE and
928 YYLTYPE.
929
930 YYPARSE_PARAM and YYLEX_PARAM, deprecated in favor of %parse-param and
931 %lex-param, will no longer be supported.
932
933 Support for the preprocessor symbol YYERROR_VERBOSE will be removed, use
934 %error-verbose.
935
936 *** The generated header will be included (yacc.c)
937
938 Instead of duplicating the content of the generated header (definition of
939 YYSTYPE, yyparse declaration etc.), the generated parser will include it,
940 as is already the case for GLR or C++ parsers. This change is deferred
941 because existing versions of ylwrap (e.g., Automake 1.12.1) do not support
942 it.
943
944 ** Generated Parser Headers
945
946 *** Guards (yacc.c, glr.c, glr.cc)
947
948 The generated headers are now guarded, as is already the case for C++
949 parsers (lalr1.cc). For instance, with --defines=foo.h:
950
951 #ifndef YY_FOO_H
952 # define YY_FOO_H
953 ...
954 #endif /* !YY_FOO_H */
955
956 *** New declarations (yacc.c, glr.c)
957
958 The generated header now declares yydebug and yyparse. Both honor
959 --name-prefix=bar_, and yield
960
961 int bar_parse (void);
962
963 rather than
964
965 #define yyparse bar_parse
966 int yyparse (void);
967
968 in order to facilitate the inclusion of several parser headers inside a
969 single compilation unit.
970
971 *** Exported symbols in C++
972
973 The symbols YYTOKEN_TABLE and YYERROR_VERBOSE, which were defined in the
974 header, are removed, as they prevent the possibility of including several
975 generated headers from a single compilation unit.
976
977 *** YYLSP_NEEDED
978
979 For the same reasons, the undocumented and unused macro YYLSP_NEEDED is no
980 longer defined.
981
982 ** New %define variable: api.prefix
983
984 Now that the generated headers are more complete and properly protected
985 against multiple inclusions, constant names, such as YYSTYPE are a
986 problem. While yyparse and others are properly renamed by %name-prefix,
987 YYSTYPE, YYDEBUG and others have never been affected by it. Because it
988 would introduce backward compatibility issues in projects not expecting
989 YYSTYPE to be renamed, instead of changing the behavior of %name-prefix,
990 it is deprecated in favor of a new %define variable: api.prefix.
991
992 The following examples compares both:
993
994 %name-prefix "bar_" | %define api.prefix "bar_"
995 %token <ival> FOO %token <ival> FOO
996 %union { int ival; } %union { int ival; }
997 %% %%
998 exp: 'a'; exp: 'a';
999
1000 bison generates:
1001
1002 #ifndef BAR_FOO_H #ifndef BAR_FOO_H
1003 # define BAR_FOO_H # define BAR_FOO_H
1004
1005 /* Enabling traces. */ /* Enabling traces. */
1006 # ifndef YYDEBUG | # ifndef BAR_DEBUG
1007 > # if defined YYDEBUG
1008 > # if YYDEBUG
1009 > # define BAR_DEBUG 1
1010 > # else
1011 > # define BAR_DEBUG 0
1012 > # endif
1013 > # else
1014 # define YYDEBUG 0 | # define BAR_DEBUG 0
1015 > # endif
1016 # endif | # endif
1017
1018 # if YYDEBUG | # if BAR_DEBUG
1019 extern int bar_debug; extern int bar_debug;
1020 # endif # endif
1021
1022 /* Tokens. */ /* Tokens. */
1023 # ifndef YYTOKENTYPE | # ifndef BAR_TOKENTYPE
1024 # define YYTOKENTYPE | # define BAR_TOKENTYPE
1025 enum yytokentype { | enum bar_tokentype {
1026 FOO = 258 FOO = 258
1027 }; };
1028 # endif # endif
1029
1030 #if ! defined YYSTYPE \ | #if ! defined BAR_STYPE \
1031 && ! defined YYSTYPE_IS_DECLARED | && ! defined BAR_STYPE_IS_DECLARED
1032 typedef union YYSTYPE | typedef union BAR_STYPE
1033 { {
1034 int ival; int ival;
1035 } YYSTYPE; | } BAR_STYPE;
1036 # define YYSTYPE_IS_DECLARED 1 | # define BAR_STYPE_IS_DECLARED 1
1037 #endif #endif
1038
1039 extern YYSTYPE bar_lval; | extern BAR_STYPE bar_lval;
1040
1041 int bar_parse (void); int bar_parse (void);
1042
1043 #endif /* !BAR_FOO_H */ #endif /* !BAR_FOO_H */
1044
1045 * Noteworthy changes in release 2.5.1 (2012-06-05) [stable]
1046
1047 ** Future changes:
1048
1049 The next major release will drop support for generating parsers in K&R C.
1050
1051 ** yacc.c: YYBACKUP works as expected.
1052
1053 ** glr.c improvements:
1054
1055 *** Location support is eliminated when not requested:
1056
1057 GLR parsers used to include location-related code even when locations were
1058 not requested, and therefore not even usable.
1059
1060 *** __attribute__ is preserved:
1061
1062 __attribute__ is no longer disabled when __STRICT_ANSI__ is defined (i.e.,
1063 when -std is passed to GCC).
1064
1065 ** lalr1.java: several fixes:
1066
1067 The Java parser no longer throws ArrayIndexOutOfBoundsException if the
1068 first token leads to a syntax error. Some minor clean ups.
1069
1070 ** Changes for C++:
1071
1072 *** C++11 compatibility:
1073
1074 C and C++ parsers use "nullptr" instead of "0" when __cplusplus is 201103L
1075 or higher.
1076
1077 *** Header guards
1078
1079 The header files such as "parser.hh", "location.hh", etc. used a constant
1080 name for preprocessor guards, for instance:
1081
1082 #ifndef BISON_LOCATION_HH
1083 # define BISON_LOCATION_HH
1084 ...
1085 #endif // !BISON_LOCATION_HH
1086
1087 The inclusion guard is now computed from "PREFIX/FILE-NAME", where lower
1088 case characters are converted to upper case, and series of
1089 non-alphanumerical characters are converted to an underscore.
1090
1091 With "bison -o lang++/parser.cc", "location.hh" would now include:
1092
1093 #ifndef YY_LANG_LOCATION_HH
1094 # define YY_LANG_LOCATION_HH
1095 ...
1096 #endif // !YY_LANG_LOCATION_HH
1097
1098 *** C++ locations:
1099
1100 The position and location constructors (and their initialize methods)
1101 accept new arguments for line and column. Several issues in the
1102 documentation were fixed.
1103
1104 ** liby is no longer asking for "rpl_fprintf" on some platforms.
1105
1106 ** Changes in the manual:
1107
1108 *** %printer is documented
1109
1110 The "%printer" directive, supported since at least Bison 1.50, is finally
1111 documented. The "mfcalc" example is extended to demonstrate it.
1112
1113 For consistency with the C skeletons, the C++ parsers now also support
1114 "yyoutput" (as an alias to "debug_stream ()").
1115
1116 *** Several improvements have been made:
1117
1118 The layout for grammar excerpts was changed to a more compact scheme.
1119 Named references are motivated. The description of the automaton
1120 description file (*.output) is updated to the current format. Incorrect
1121 index entries were fixed. Some other errors were fixed.
1122
1123 ** Building bison:
1124
1125 *** Conflicting prototypes with recent/modified Flex.
1126
1127 Fixed build problems with the current, unreleased, version of Flex, and
1128 some modified versions of 2.5.35, which have modified function prototypes.
1129
1130 *** Warnings during the build procedure have been eliminated.
1131
1132 *** Several portability problems in the test suite have been fixed:
1133
1134 This includes warnings with some compilers, unexpected behavior of tools
1135 such as diff, warning messages from the test suite itself, etc.
1136
1137 *** The install-pdf target works properly:
1138
1139 Running "make install-pdf" (or -dvi, -html, -info, and -ps) no longer
1140 halts in the middle of its course.
1141
1142 * Changes in version 2.5 (2011-05-14):
1143
1144 ** Grammar symbol names can now contain non-initial dashes:
1145
1146 Consistently with directives (such as %error-verbose) and with
1147 %define variables (e.g. push-pull), grammar symbol names may contain
1148 dashes in any position except the beginning. This is a GNU
1149 extension over POSIX Yacc. Thus, use of this extension is reported
1150 by -Wyacc and rejected in Yacc mode (--yacc).
1151
1152 ** Named references:
1153
1154 Historically, Yacc and Bison have supported positional references
1155 ($n, $$) to allow access to symbol values from inside of semantic
1156 actions code.
1157
1158 Starting from this version, Bison can also accept named references.
1159 When no ambiguity is possible, original symbol names may be used
1160 as named references:
1161
1162 if_stmt : "if" cond_expr "then" then_stmt ';'
1163 { $if_stmt = mk_if_stmt($cond_expr, $then_stmt); }
1164
1165 In the more common case, explicit names may be declared:
1166
1167 stmt[res] : "if" expr[cond] "then" stmt[then] "else" stmt[else] ';'
1168 { $res = mk_if_stmt($cond, $then, $else); }
1169
1170 Location information is also accessible using @name syntax. When
1171 accessing symbol names containing dots or dashes, explicit bracketing
1172 ($[sym.1]) must be used.
1173
1174 These features are experimental in this version. More user feedback
1175 will help to stabilize them.
1176 Contributed by Alex Rozenman.
1177
1178 ** IELR(1) and canonical LR(1):
1179
1180 IELR(1) is a minimal LR(1) parser table generation algorithm. That
1181 is, given any context-free grammar, IELR(1) generates parser tables
1182 with the full language-recognition power of canonical LR(1) but with
1183 nearly the same number of parser states as LALR(1). This reduction
1184 in parser states is often an order of magnitude. More importantly,
1185 because canonical LR(1)'s extra parser states may contain duplicate
1186 conflicts in the case of non-LR(1) grammars, the number of conflicts
1187 for IELR(1) is often an order of magnitude less as well. This can
1188 significantly reduce the complexity of developing of a grammar.
1189
1190 Bison can now generate IELR(1) and canonical LR(1) parser tables in
1191 place of its traditional LALR(1) parser tables, which remain the
1192 default. You can specify the type of parser tables in the grammar
1193 file with these directives:
1194
1195 %define lr.type lalr
1196 %define lr.type ielr
1197 %define lr.type canonical-lr
1198
1199 The default-reduction optimization in the parser tables can also be
1200 adjusted using "%define lr.default-reductions". For details on both
1201 of these features, see the new section "Tuning LR" in the Bison
1202 manual.
1203
1204 These features are experimental. More user feedback will help to
1205 stabilize them.
1206
1207 ** LAC (Lookahead Correction) for syntax error handling
1208
1209 Contributed by Joel E. Denny.
1210
1211 Canonical LR, IELR, and LALR can suffer from a couple of problems
1212 upon encountering a syntax error. First, the parser might perform
1213 additional parser stack reductions before discovering the syntax
1214 error. Such reductions can perform user semantic actions that are
1215 unexpected because they are based on an invalid token, and they
1216 cause error recovery to begin in a different syntactic context than
1217 the one in which the invalid token was encountered. Second, when
1218 verbose error messages are enabled (with %error-verbose or the
1219 obsolete "#define YYERROR_VERBOSE"), the expected token list in the
1220 syntax error message can both contain invalid tokens and omit valid
1221 tokens.
1222
1223 The culprits for the above problems are %nonassoc, default
1224 reductions in inconsistent states, and parser state merging. Thus,
1225 IELR and LALR suffer the most. Canonical LR can suffer only if
1226 %nonassoc is used or if default reductions are enabled for
1227 inconsistent states.
1228
1229 LAC is a new mechanism within the parsing algorithm that solves
1230 these problems for canonical LR, IELR, and LALR without sacrificing
1231 %nonassoc, default reductions, or state merging. When LAC is in
1232 use, canonical LR and IELR behave almost exactly the same for both
1233 syntactically acceptable and syntactically unacceptable input.
1234 While LALR still does not support the full language-recognition
1235 power of canonical LR and IELR, LAC at least enables LALR's syntax
1236 error handling to correctly reflect LALR's language-recognition
1237 power.
1238
1239 Currently, LAC is only supported for deterministic parsers in C.
1240 You can enable LAC with the following directive:
1241
1242 %define parse.lac full
1243
1244 See the new section "LAC" in the Bison manual for additional
1245 details including a few caveats.
1246
1247 LAC is an experimental feature. More user feedback will help to
1248 stabilize it.
1249
1250 ** %define improvements:
1251
1252 *** Can now be invoked via the command line:
1253
1254 Each of these command-line options
1255
1256 -D NAME[=VALUE]
1257 --define=NAME[=VALUE]
1258
1259 -F NAME[=VALUE]
1260 --force-define=NAME[=VALUE]
1261
1262 is equivalent to this grammar file declaration
1263
1264 %define NAME ["VALUE"]
1265
1266 except that the manner in which Bison processes multiple definitions
1267 for the same NAME differs. Most importantly, -F and --force-define
1268 quietly override %define, but -D and --define do not. For further
1269 details, see the section "Bison Options" in the Bison manual.
1270
1271 *** Variables renamed:
1272
1273 The following %define variables
1274
1275 api.push_pull
1276 lr.keep_unreachable_states
1277
1278 have been renamed to
1279
1280 api.push-pull
1281 lr.keep-unreachable-states
1282
1283 The old names are now deprecated but will be maintained indefinitely
1284 for backward compatibility.
1285
1286 *** Values no longer need to be quoted in the grammar file:
1287
1288 If a %define value is an identifier, it no longer needs to be placed
1289 within quotations marks. For example,
1290
1291 %define api.push-pull "push"
1292
1293 can be rewritten as
1294
1295 %define api.push-pull push
1296
1297 *** Unrecognized variables are now errors not warnings.
1298
1299 *** Multiple invocations for any variable is now an error not a warning.
1300
1301 ** Unrecognized %code qualifiers are now errors not warnings.
1302
1303 ** Character literals not of length one:
1304
1305 Previously, Bison quietly converted all character literals to length
1306 one. For example, without warning, Bison interpreted the operators in
1307 the following grammar to be the same token:
1308
1309 exp: exp '++'
1310 | exp '+' exp
1311 ;
1312
1313 Bison now warns when a character literal is not of length one. In
1314 some future release, Bison will start reporting an error instead.
1315
1316 ** Destructor calls fixed for lookaheads altered in semantic actions:
1317
1318 Previously for deterministic parsers in C, if a user semantic action
1319 altered yychar, the parser in some cases used the old yychar value to
1320 determine which destructor to call for the lookahead upon a syntax
1321 error or upon parser return. This bug has been fixed.
1322
1323 ** C++ parsers use YYRHSLOC:
1324
1325 Similarly to the C parsers, the C++ parsers now define the YYRHSLOC
1326 macro and use it in the default YYLLOC_DEFAULT. You are encouraged
1327 to use it. If, for instance, your location structure has "first"
1328 and "last" members, instead of
1329
1330 # define YYLLOC_DEFAULT(Current, Rhs, N) \
1331 do \
1332 if (N) \
1333 { \
1334 (Current).first = (Rhs)[1].location.first; \
1335 (Current).last = (Rhs)[N].location.last; \
1336 } \
1337 else \
1338 { \
1339 (Current).first = (Current).last = (Rhs)[0].location.last; \
1340 } \
1341 while (false)
1342
1343 use:
1344
1345 # define YYLLOC_DEFAULT(Current, Rhs, N) \
1346 do \
1347 if (N) \
1348 { \
1349 (Current).first = YYRHSLOC (Rhs, 1).first; \
1350 (Current).last = YYRHSLOC (Rhs, N).last; \
1351 } \
1352 else \
1353 { \
1354 (Current).first = (Current).last = YYRHSLOC (Rhs, 0).last; \
1355 } \
1356 while (false)
1357
1358 ** YYLLOC_DEFAULT in C++:
1359
1360 The default implementation of YYLLOC_DEFAULT used to be issued in
1361 the header file. It is now output in the implementation file, after
1362 the user %code sections so that its #ifndef guard does not try to
1363 override the user's YYLLOC_DEFAULT if provided.
1364
1365 ** YYFAIL now produces warnings and Java parsers no longer implement it:
1366
1367 YYFAIL has existed for many years as an undocumented feature of
1368 deterministic parsers in C generated by Bison. More recently, it was
1369 a documented feature of Bison's experimental Java parsers. As
1370 promised in Bison 2.4.2's NEWS entry, any appearance of YYFAIL in a
1371 semantic action now produces a deprecation warning, and Java parsers
1372 no longer implement YYFAIL at all. For further details, including a
1373 discussion of how to suppress C preprocessor warnings about YYFAIL
1374 being unused, see the Bison 2.4.2 NEWS entry.
1375
1376 ** Temporary hack for adding a semicolon to the user action:
1377
1378 Previously, Bison appended a semicolon to every user action for
1379 reductions when the output language defaulted to C (specifically, when
1380 neither %yacc, %language, %skeleton, or equivalent command-line
1381 options were specified). This allowed actions such as
1382
1383 exp: exp "+" exp { $$ = $1 + $3 };
1384
1385 instead of
1386
1387 exp: exp "+" exp { $$ = $1 + $3; };
1388
1389 As a first step in removing this misfeature, Bison now issues a
1390 warning when it appends a semicolon. Moreover, in cases where Bison
1391 cannot easily determine whether a semicolon is needed (for example, an
1392 action ending with a cpp directive or a braced compound initializer),
1393 it no longer appends one. Thus, the C compiler might now complain
1394 about a missing semicolon where it did not before. Future releases of
1395 Bison will cease to append semicolons entirely.
1396
1397 ** Verbose syntax error message fixes:
1398
1399 When %error-verbose or the obsolete "#define YYERROR_VERBOSE" is
1400 specified, syntax error messages produced by the generated parser
1401 include the unexpected token as well as a list of expected tokens.
1402 The effect of %nonassoc on these verbose messages has been corrected
1403 in two ways, but a more complete fix requires LAC, described above:
1404
1405 *** When %nonassoc is used, there can exist parser states that accept no
1406 tokens, and so the parser does not always require a lookahead token
1407 in order to detect a syntax error. Because no unexpected token or
1408 expected tokens can then be reported, the verbose syntax error
1409 message described above is suppressed, and the parser instead
1410 reports the simpler message, "syntax error". Previously, this
1411 suppression was sometimes erroneously triggered by %nonassoc when a
1412 lookahead was actually required. Now verbose messages are
1413 suppressed only when all previous lookaheads have already been
1414 shifted or discarded.
1415
1416 *** Previously, the list of expected tokens erroneously included tokens
1417 that would actually induce a syntax error because conflicts for them
1418 were resolved with %nonassoc in the current parser state. Such
1419 tokens are now properly omitted from the list.
1420
1421 *** Expected token lists are still often wrong due to state merging
1422 (from LALR or IELR) and default reductions, which can both add
1423 invalid tokens and subtract valid tokens. Canonical LR almost
1424 completely fixes this problem by eliminating state merging and
1425 default reductions. However, there is one minor problem left even
1426 when using canonical LR and even after the fixes above. That is,
1427 if the resolution of a conflict with %nonassoc appears in a later
1428 parser state than the one at which some syntax error is
1429 discovered, the conflicted token is still erroneously included in
1430 the expected token list. Bison's new LAC implementation,
1431 described above, eliminates this problem and the need for
1432 canonical LR. However, LAC is still experimental and is disabled
1433 by default.
1434
1435 ** Java skeleton fixes:
1436
1437 *** A location handling bug has been fixed.
1438
1439 *** The top element of each of the value stack and location stack is now
1440 cleared when popped so that it can be garbage collected.
1441
1442 *** Parser traces now print the top element of the stack.
1443
1444 ** -W/--warnings fixes:
1445
1446 *** Bison now properly recognizes the "no-" versions of categories:
1447
1448 For example, given the following command line, Bison now enables all
1449 warnings except warnings for incompatibilities with POSIX Yacc:
1450
1451 bison -Wall,no-yacc gram.y
1452
1453 *** Bison now treats S/R and R/R conflicts like other warnings:
1454
1455 Previously, conflict reports were independent of Bison's normal
1456 warning system. Now, Bison recognizes the warning categories
1457 "conflicts-sr" and "conflicts-rr". This change has important
1458 consequences for the -W and --warnings command-line options. For
1459 example:
1460
1461 bison -Wno-conflicts-sr gram.y # S/R conflicts not reported
1462 bison -Wno-conflicts-rr gram.y # R/R conflicts not reported
1463 bison -Wnone gram.y # no conflicts are reported
1464 bison -Werror gram.y # any conflict is an error
1465
1466 However, as before, if the %expect or %expect-rr directive is
1467 specified, an unexpected number of conflicts is an error, and an
1468 expected number of conflicts is not reported, so -W and --warning
1469 then have no effect on the conflict report.
1470
1471 *** The "none" category no longer disables a preceding "error":
1472
1473 For example, for the following command line, Bison now reports
1474 errors instead of warnings for incompatibilities with POSIX Yacc:
1475
1476 bison -Werror,none,yacc gram.y
1477
1478 *** The "none" category now disables all Bison warnings:
1479
1480 Previously, the "none" category disabled only Bison warnings for
1481 which there existed a specific -W/--warning category. However,
1482 given the following command line, Bison is now guaranteed to
1483 suppress all warnings:
1484
1485 bison -Wnone gram.y
1486
1487 ** Precedence directives can now assign token number 0:
1488
1489 Since Bison 2.3b, which restored the ability of precedence
1490 directives to assign token numbers, doing so for token number 0 has
1491 produced an assertion failure. For example:
1492
1493 %left END 0
1494
1495 This bug has been fixed.
1496
1497 * Changes in version 2.4.3 (2010-08-05):
1498
1499 ** Bison now obeys -Werror and --warnings=error for warnings about
1500 grammar rules that are useless in the parser due to conflicts.
1501
1502 ** Problems with spawning M4 on at least FreeBSD 8 and FreeBSD 9 have
1503 been fixed.
1504
1505 ** Failures in the test suite for GCC 4.5 have been fixed.
1506
1507 ** Failures in the test suite for some versions of Sun Studio C++ have
1508 been fixed.
1509
1510 ** Contrary to Bison 2.4.2's NEWS entry, it has been decided that
1511 warnings about undefined %prec identifiers will not be converted to
1512 errors in Bison 2.5. They will remain warnings, which should be
1513 sufficient for POSIX while avoiding backward compatibility issues.
1514
1515 ** Minor documentation fixes.
1516
1517 * Changes in version 2.4.2 (2010-03-20):
1518
1519 ** Some portability problems that resulted in failures and livelocks
1520 in the test suite on some versions of at least Solaris, AIX, HP-UX,
1521 RHEL4, and Tru64 have been addressed. As a result, fatal Bison
1522 errors should no longer cause M4 to report a broken pipe on the
1523 affected platforms.
1524
1525 ** "%prec IDENTIFIER" requires IDENTIFIER to be defined separately.
1526
1527 POSIX specifies that an error be reported for any identifier that does
1528 not appear on the LHS of a grammar rule and that is not defined by
1529 %token, %left, %right, or %nonassoc. Bison 2.3b and later lost this
1530 error report for the case when an identifier appears only after a
1531 %prec directive. It is now restored. However, for backward
1532 compatibility with recent Bison releases, it is only a warning for
1533 now. In Bison 2.5 and later, it will return to being an error.
1534 [Between the 2.4.2 and 2.4.3 releases, it was decided that this
1535 warning will not be converted to an error in Bison 2.5.]
1536
1537 ** Detection of GNU M4 1.4.6 or newer during configure is improved.
1538
1539 ** Warnings from gcc's -Wundef option about undefined YYENABLE_NLS,
1540 YYLTYPE_IS_TRIVIAL, and __STRICT_ANSI__ in C/C++ parsers are now
1541 avoided.
1542
1543 ** %code is now a permanent feature.
1544
1545 A traditional Yacc prologue directive is written in the form:
1546
1547 %{CODE%}
1548
1549 To provide a more flexible alternative, Bison 2.3b introduced the
1550 %code directive with the following forms for C/C++:
1551
1552 %code {CODE}
1553 %code requires {CODE}
1554 %code provides {CODE}
1555 %code top {CODE}
1556
1557 These forms are now considered permanent features of Bison. See the
1558 %code entries in the section "Bison Declaration Summary" in the Bison
1559 manual for a summary of their functionality. See the section
1560 "Prologue Alternatives" for a detailed discussion including the
1561 advantages of %code over the traditional Yacc prologue directive.
1562
1563 Bison's Java feature as a whole including its current usage of %code
1564 is still considered experimental.
1565
1566 ** YYFAIL is deprecated and will eventually be removed.
1567
1568 YYFAIL has existed for many years as an undocumented feature of
1569 deterministic parsers in C generated by Bison. Previously, it was
1570 documented for Bison's experimental Java parsers. YYFAIL is no longer
1571 documented for Java parsers and is formally deprecated in both cases.
1572 Users are strongly encouraged to migrate to YYERROR, which is
1573 specified by POSIX.
1574
1575 Like YYERROR, you can invoke YYFAIL from a semantic action in order to
1576 induce a syntax error. The most obvious difference from YYERROR is
1577 that YYFAIL will automatically invoke yyerror to report the syntax
1578 error so that you don't have to. However, there are several other
1579 subtle differences between YYERROR and YYFAIL, and YYFAIL suffers from
1580 inherent flaws when %error-verbose or "#define YYERROR_VERBOSE" is
1581 used. For a more detailed discussion, see:
1582
1583 http://lists.gnu.org/archive/html/bison-patches/2009-12/msg00024.html
1584
1585 The upcoming Bison 2.5 will remove YYFAIL from Java parsers, but
1586 deterministic parsers in C will continue to implement it. However,
1587 because YYFAIL is already flawed, it seems futile to try to make new
1588 Bison features compatible with it. Thus, during parser generation,
1589 Bison 2.5 will produce a warning whenever it discovers YYFAIL in a
1590 rule action. In a later release, YYFAIL will be disabled for
1591 %error-verbose and "#define YYERROR_VERBOSE". Eventually, YYFAIL will
1592 be removed altogether.
1593
1594 There exists at least one case where Bison 2.5's YYFAIL warning will
1595 be a false positive. Some projects add phony uses of YYFAIL and other
1596 Bison-defined macros for the sole purpose of suppressing C
1597 preprocessor warnings (from GCC cpp's -Wunused-macros, for example).
1598 To avoid Bison's future warning, such YYFAIL uses can be moved to the
1599 epilogue (that is, after the second "%%") in the Bison input file. In
1600 this release (2.4.2), Bison already generates its own code to suppress
1601 C preprocessor warnings for YYFAIL, so projects can remove their own
1602 phony uses of YYFAIL if compatibility with Bison releases prior to
1603 2.4.2 is not necessary.
1604
1605 ** Internationalization.
1606
1607 Fix a regression introduced in Bison 2.4: Under some circumstances,
1608 message translations were not installed although supported by the
1609 host system.
1610
1611 * Changes in version 2.4.1 (2008-12-11):
1612
1613 ** In the GLR defines file, unexpanded M4 macros in the yylval and yylloc
1614 declarations have been fixed.
1615
1616 ** Temporary hack for adding a semicolon to the user action.
1617
1618 Bison used to prepend a trailing semicolon at the end of the user
1619 action for reductions. This allowed actions such as
1620
1621 exp: exp "+" exp { $$ = $1 + $3 };
1622
1623 instead of
1624
1625 exp: exp "+" exp { $$ = $1 + $3; };
1626
1627 Some grammars still depend on this "feature". Bison 2.4.1 restores
1628 the previous behavior in the case of C output (specifically, when
1629 neither %language or %skeleton or equivalent command-line options
1630 are used) to leave more time for grammars depending on the old
1631 behavior to be adjusted. Future releases of Bison will disable this
1632 feature.
1633
1634 ** A few minor improvements to the Bison manual.
1635
1636 * Changes in version 2.4 (2008-11-02):
1637
1638 ** %language is an experimental feature.
1639
1640 We first introduced this feature in test release 2.3b as a cleaner
1641 alternative to %skeleton. Since then, we have discussed the possibility of
1642 modifying its effect on Bison's output file names. Thus, in this release,
1643 we consider %language to be an experimental feature that will likely evolve
1644 in future releases.
1645
1646 ** Forward compatibility with GNU M4 has been improved.
1647
1648 ** Several bugs in the C++ skeleton and the experimental Java skeleton have been
1649 fixed.
1650
1651 * Changes in version 2.3b (2008-05-27):
1652
1653 ** The quotes around NAME that used to be required in the following directive
1654 are now deprecated:
1655
1656 %define NAME "VALUE"
1657
1658 ** The directive "%pure-parser" is now deprecated in favor of:
1659
1660 %define api.pure
1661
1662 which has the same effect except that Bison is more careful to warn about
1663 unreasonable usage in the latter case.
1664
1665 ** Push Parsing
1666
1667 Bison can now generate an LALR(1) parser in C with a push interface. That
1668 is, instead of invoking "yyparse", which pulls tokens from "yylex", you can
1669 push one token at a time to the parser using "yypush_parse", which will
1670 return to the caller after processing each token. By default, the push
1671 interface is disabled. Either of the following directives will enable it:
1672
1673 %define api.push_pull "push" // Just push; does not require yylex.
1674 %define api.push_pull "both" // Push and pull; requires yylex.
1675
1676 See the new section "A Push Parser" in the Bison manual for details.
1677
1678 The current push parsing interface is experimental and may evolve. More user
1679 feedback will help to stabilize it.
1680
1681 ** The -g and --graph options now output graphs in Graphviz DOT format,
1682 not VCG format. Like --graph, -g now also takes an optional FILE argument
1683 and thus cannot be bundled with other short options.
1684
1685 ** Java
1686
1687 Bison can now generate an LALR(1) parser in Java. The skeleton is
1688 "data/lalr1.java". Consider using the new %language directive instead of
1689 %skeleton to select it.
1690
1691 See the new section "Java Parsers" in the Bison manual for details.
1692
1693 The current Java interface is experimental and may evolve. More user
1694 feedback will help to stabilize it.
1695 Contributed by Paolo Bonzini.
1696
1697 ** %language
1698
1699 This new directive specifies the programming language of the generated
1700 parser, which can be C (the default), C++, or Java. Besides the skeleton
1701 that Bison uses, the directive affects the names of the generated files if
1702 the grammar file's name ends in ".y".
1703
1704 ** XML Automaton Report
1705
1706 Bison can now generate an XML report of the LALR(1) automaton using the new
1707 "--xml" option. The current XML schema is experimental and may evolve. More
1708 user feedback will help to stabilize it.
1709 Contributed by Wojciech Polak.
1710
1711 ** The grammar file may now specify the name of the parser header file using
1712 %defines. For example:
1713
1714 %defines "parser.h"
1715
1716 ** When reporting useless rules, useless nonterminals, and unused terminals,
1717 Bison now employs the terms "useless in grammar" instead of "useless",
1718 "useless in parser" instead of "never reduced", and "unused in grammar"
1719 instead of "unused".
1720
1721 ** Unreachable State Removal
1722
1723 Previously, Bison sometimes generated parser tables containing unreachable
1724 states. A state can become unreachable during conflict resolution if Bison
1725 disables a shift action leading to it from a predecessor state. Bison now:
1726
1727 1. Removes unreachable states.
1728
1729 2. Does not report any conflicts that appeared in unreachable states.
1730 WARNING: As a result, you may need to update %expect and %expect-rr
1731 directives in existing grammar files.
1732
1733 3. For any rule used only in such states, Bison now reports the rule as
1734 "useless in parser due to conflicts".
1735
1736 This feature can be disabled with the following directive:
1737
1738 %define lr.keep_unreachable_states
1739
1740 See the %define entry in the "Bison Declaration Summary" in the Bison manual
1741 for further discussion.
1742
1743 ** Lookahead Set Correction in the ".output" Report
1744
1745 When instructed to generate a ".output" file including lookahead sets
1746 (using "--report=lookahead", for example), Bison now prints each reduction's
1747 lookahead set only next to the associated state's one item that (1) is
1748 associated with the same rule as the reduction and (2) has its dot at the end
1749 of its RHS. Previously, Bison also erroneously printed the lookahead set
1750 next to all of the state's other items associated with the same rule. This
1751 bug affected only the ".output" file and not the generated parser source
1752 code.
1753
1754 ** --report-file=FILE is a new option to override the default ".output" file
1755 name.
1756
1757 ** The "=" that used to be required in the following directives is now
1758 deprecated:
1759
1760 %file-prefix "parser"
1761 %name-prefix "c_"
1762 %output "parser.c"
1763
1764 ** An Alternative to "%{...%}" -- "%code QUALIFIER {CODE}"
1765
1766 Bison 2.3a provided a new set of directives as a more flexible alternative to
1767 the traditional Yacc prologue blocks. Those have now been consolidated into
1768 a single %code directive with an optional qualifier field, which identifies
1769 the purpose of the code and thus the location(s) where Bison should generate
1770 it:
1771
1772 1. "%code {CODE}" replaces "%after-header {CODE}"
1773 2. "%code requires {CODE}" replaces "%start-header {CODE}"
1774 3. "%code provides {CODE}" replaces "%end-header {CODE}"
1775 4. "%code top {CODE}" replaces "%before-header {CODE}"
1776
1777 See the %code entries in section "Bison Declaration Summary" in the Bison
1778 manual for a summary of the new functionality. See the new section "Prologue
1779 Alternatives" for a detailed discussion including the advantages of %code
1780 over the traditional Yacc prologues.
1781
1782 The prologue alternatives are experimental. More user feedback will help to
1783 determine whether they should become permanent features.
1784
1785 ** Revised warning: unset or unused mid-rule values
1786
1787 Since Bison 2.2, Bison has warned about mid-rule values that are set but not
1788 used within any of the actions of the parent rule. For example, Bison warns
1789 about unused $2 in:
1790
1791 exp: '1' { $$ = 1; } '+' exp { $$ = $1 + $4; };
1792
1793 Now, Bison also warns about mid-rule values that are used but not set. For
1794 example, Bison warns about unset $$ in the mid-rule action in:
1795
1796 exp: '1' { $1 = 1; } '+' exp { $$ = $2 + $4; };
1797
1798 However, Bison now disables both of these warnings by default since they
1799 sometimes prove to be false alarms in existing grammars employing the Yacc
1800 constructs $0 or $-N (where N is some positive integer).
1801
1802 To enable these warnings, specify the option "--warnings=midrule-values" or
1803 "-W", which is a synonym for "--warnings=all".
1804
1805 ** Default %destructor or %printer with "<*>" or "<>"
1806
1807 Bison now recognizes two separate kinds of default %destructor's and
1808 %printer's:
1809
1810 1. Place "<*>" in a %destructor/%printer symbol list to define a default
1811 %destructor/%printer for all grammar symbols for which you have formally
1812 declared semantic type tags.
1813
1814 2. Place "<>" in a %destructor/%printer symbol list to define a default
1815 %destructor/%printer for all grammar symbols without declared semantic
1816 type tags.
1817
1818 Bison no longer supports the "%symbol-default" notation from Bison 2.3a.
1819 "<*>" and "<>" combined achieve the same effect with one exception: Bison no
1820 longer applies any %destructor to a mid-rule value if that mid-rule value is
1821 not actually ever referenced using either $$ or $n in a semantic action.
1822
1823 The default %destructor's and %printer's are experimental. More user
1824 feedback will help to determine whether they should become permanent
1825 features.
1826
1827 See the section "Freeing Discarded Symbols" in the Bison manual for further
1828 details.
1829
1830 ** %left, %right, and %nonassoc can now declare token numbers. This is required
1831 by POSIX. However, see the end of section "Operator Precedence" in the Bison
1832 manual for a caveat concerning the treatment of literal strings.
1833
1834 ** The nonfunctional --no-parser, -n, and %no-parser options have been
1835 completely removed from Bison.
1836
1837 * Changes in version 2.3a, 2006-09-13:
1838
1839 ** Instead of %union, you can define and use your own union type
1840 YYSTYPE if your grammar contains at least one <type> tag.
1841 Your YYSTYPE need not be a macro; it can be a typedef.
1842 This change is for compatibility with other Yacc implementations,
1843 and is required by POSIX.
1844
1845 ** Locations columns and lines start at 1.
1846 In accordance with the GNU Coding Standards and Emacs.
1847
1848 ** You may now declare per-type and default %destructor's and %printer's:
1849
1850 For example:
1851
1852 %union { char *string; }
1853 %token <string> STRING1
1854 %token <string> STRING2
1855 %type <string> string1
1856 %type <string> string2
1857 %union { char character; }
1858 %token <character> CHR
1859 %type <character> chr
1860 %destructor { free ($$); } %symbol-default
1861 %destructor { free ($$); printf ("%d", @$.first_line); } STRING1 string1
1862 %destructor { } <character>
1863
1864 guarantees that, when the parser discards any user-defined symbol that has a
1865 semantic type tag other than "<character>", it passes its semantic value to
1866 "free". However, when the parser discards a "STRING1" or a "string1", it
1867 also prints its line number to "stdout". It performs only the second
1868 "%destructor" in this case, so it invokes "free" only once.
1869
1870 [Although we failed to mention this here in the 2.3a release, the default
1871 %destructor's and %printer's were experimental, and they were rewritten in
1872 future versions.]
1873
1874 ** Except for LALR(1) parsers in C with POSIX Yacc emulation enabled (with "-y",
1875 "--yacc", or "%yacc"), Bison no longer generates #define statements for
1876 associating token numbers with token names. Removing the #define statements
1877 helps to sanitize the global namespace during preprocessing, but POSIX Yacc
1878 requires them. Bison still generates an enum for token names in all cases.
1879
1880 ** Handling of traditional Yacc prologue blocks is now more consistent but
1881 potentially incompatible with previous releases of Bison.
1882
1883 As before, you declare prologue blocks in your grammar file with the
1884 "%{ ... %}" syntax. To generate the pre-prologue, Bison concatenates all
1885 prologue blocks that you've declared before the first %union. To generate
1886 the post-prologue, Bison concatenates all prologue blocks that you've
1887 declared after the first %union.
1888
1889 Previous releases of Bison inserted the pre-prologue into both the header
1890 file and the code file in all cases except for LALR(1) parsers in C. In the
1891 latter case, Bison inserted it only into the code file. For parsers in C++,
1892 the point of insertion was before any token definitions (which associate
1893 token numbers with names). For parsers in C, the point of insertion was
1894 after the token definitions.
1895
1896 Now, Bison never inserts the pre-prologue into the header file. In the code
1897 file, it always inserts it before the token definitions.
1898
1899 ** Bison now provides a more flexible alternative to the traditional Yacc
1900 prologue blocks: %before-header, %start-header, %end-header, and
1901 %after-header.
1902
1903 For example, the following declaration order in the grammar file reflects the
1904 order in which Bison will output these code blocks. However, you are free to
1905 declare these code blocks in your grammar file in whatever order is most
1906 convenient for you:
1907
1908 %before-header {
1909 /* Bison treats this block like a pre-prologue block: it inserts it into
1910 * the code file before the contents of the header file. It does *not*
1911 * insert it into the header file. This is a good place to put
1912 * #include's that you want at the top of your code file. A common
1913 * example is '#include "system.h"'. */
1914 }
1915 %start-header {
1916 /* Bison inserts this block into both the header file and the code file.
1917 * In both files, the point of insertion is before any Bison-generated
1918 * token, semantic type, location type, and class definitions. This is a
1919 * good place to define %union dependencies, for example. */
1920 }
1921 %union {
1922 /* Unlike the traditional Yacc prologue blocks, the output order for the
1923 * new %*-header blocks is not affected by their declaration position
1924 * relative to any %union in the grammar file. */
1925 }
1926 %end-header {
1927 /* Bison inserts this block into both the header file and the code file.
1928 * In both files, the point of insertion is after the Bison-generated
1929 * definitions. This is a good place to declare or define public
1930 * functions or data structures that depend on the Bison-generated
1931 * definitions. */
1932 }
1933 %after-header {
1934 /* Bison treats this block like a post-prologue block: it inserts it into
1935 * the code file after the contents of the header file. It does *not*
1936 * insert it into the header file. This is a good place to declare or
1937 * define internal functions or data structures that depend on the
1938 * Bison-generated definitions. */
1939 }
1940
1941 If you have multiple occurrences of any one of the above declarations, Bison
1942 will concatenate the contents in declaration order.
1943
1944 [Although we failed to mention this here in the 2.3a release, the prologue
1945 alternatives were experimental, and they were rewritten in future versions.]
1946
1947 ** The option "--report=look-ahead" has been changed to "--report=lookahead".
1948 The old spelling still works, but is not documented and may be removed
1949 in a future release.
1950
1951 * Changes in version 2.3, 2006-06-05:
1952
1953 ** GLR grammars should now use "YYRECOVERING ()" instead of "YYRECOVERING",
1954 for compatibility with LALR(1) grammars.
1955
1956 ** It is now documented that any definition of YYSTYPE or YYLTYPE should
1957 be to a type name that does not contain parentheses or brackets.
1958
1959 * Changes in version 2.2, 2006-05-19:
1960
1961 ** The distribution terms for all Bison-generated parsers now permit
1962 using the parsers in nonfree programs. Previously, this permission
1963 was granted only for Bison-generated LALR(1) parsers in C.
1964
1965 ** %name-prefix changes the namespace name in C++ outputs.
1966
1967 ** The C++ parsers export their token_type.
1968
1969 ** Bison now allows multiple %union declarations, and concatenates
1970 their contents together.
1971
1972 ** New warning: unused values
1973 Right-hand side symbols whose values are not used are reported,
1974 if the symbols have destructors. For instance:
1975
1976 exp: exp "?" exp ":" exp { $1 ? $1 : $3; }
1977 | exp "+" exp
1978 ;
1979
1980 will trigger a warning about $$ and $5 in the first rule, and $3 in
1981 the second ($1 is copied to $$ by the default rule). This example
1982 most likely contains three errors, and could be rewritten as:
1983
1984 exp: exp "?" exp ":" exp
1985 { $$ = $1 ? $3 : $5; free ($1 ? $5 : $3); free ($1); }
1986 | exp "+" exp
1987 { $$ = $1 ? $1 : $3; if ($1) free ($3); }
1988 ;
1989
1990 However, if the original actions were really intended, memory leaks
1991 and all, the warnings can be suppressed by letting Bison believe the
1992 values are used, e.g.:
1993
1994 exp: exp "?" exp ":" exp { $1 ? $1 : $3; (void) ($$, $5); }
1995 | exp "+" exp { $$ = $1; (void) $3; }
1996 ;
1997
1998 If there are mid-rule actions, the warning is issued if no action
1999 uses it. The following triggers no warning: $1 and $3 are used.
2000
2001 exp: exp { push ($1); } '+' exp { push ($3); sum (); };
2002
2003 The warning is intended to help catching lost values and memory leaks.
2004 If a value is ignored, its associated memory typically is not reclaimed.
2005
2006 ** %destructor vs. YYABORT, YYACCEPT, and YYERROR.
2007 Destructors are now called when user code invokes YYABORT, YYACCEPT,
2008 and YYERROR, for all objects on the stack, other than objects
2009 corresponding to the right-hand side of the current rule.
2010
2011 ** %expect, %expect-rr
2012 Incorrect numbers of expected conflicts are now actual errors,
2013 instead of warnings.
2014
2015 ** GLR, YACC parsers.
2016 The %parse-params are available in the destructors (and the
2017 experimental printers) as per the documentation.
2018
2019 ** Bison now warns if it finds a stray "$" or "@" in an action.
2020
2021 ** %require "VERSION"
2022 This specifies that the grammar file depends on features implemented
2023 in Bison version VERSION or higher.
2024
2025 ** lalr1.cc: The token and value types are now class members.
2026 The tokens were defined as free form enums and cpp macros. YYSTYPE
2027 was defined as a free form union. They are now class members:
2028 tokens are enumerations of the "yy::parser::token" struct, and the
2029 semantic values have the "yy::parser::semantic_type" type.
2030
2031 If you do not want or can update to this scheme, the directive
2032 '%define "global_tokens_and_yystype" "1"' triggers the global
2033 definition of tokens and YYSTYPE. This change is suitable both
2034 for previous releases of Bison, and this one.
2035
2036 If you wish to update, then make sure older version of Bison will
2037 fail using '%require "2.2"'.
2038
2039 ** DJGPP support added.
2040 \f
2041 * Changes in version 2.1, 2005-09-16:
2042
2043 ** The C++ lalr1.cc skeleton supports %lex-param.
2044
2045 ** Bison-generated parsers now support the translation of diagnostics like
2046 "syntax error" into languages other than English. The default
2047 language is still English. For details, please see the new
2048 Internationalization section of the Bison manual. Software
2049 distributors should also see the new PACKAGING file. Thanks to
2050 Bruno Haible for this new feature.
2051
2052 ** Wording in the Bison-generated parsers has been changed slightly to
2053 simplify translation. In particular, the message "memory exhausted"
2054 has replaced "parser stack overflow", as the old message was not
2055 always accurate for modern Bison-generated parsers.
2056
2057 ** Destructors are now called when the parser aborts, for all symbols left
2058 behind on the stack. Also, the start symbol is now destroyed after a
2059 successful parse. In both cases, the behavior was formerly inconsistent.
2060
2061 ** When generating verbose diagnostics, Bison-generated parsers no longer
2062 quote the literal strings associated with tokens. For example, for
2063 a syntax error associated with '%token NUM "number"' they might
2064 print 'syntax error, unexpected number' instead of 'syntax error,
2065 unexpected "number"'.
2066 \f
2067 * Changes in version 2.0, 2004-12-25:
2068
2069 ** Possibly-incompatible changes
2070
2071 - Bison-generated parsers no longer default to using the alloca function
2072 (when available) to extend the parser stack, due to widespread
2073 problems in unchecked stack-overflow detection. You can "#define
2074 YYSTACK_USE_ALLOCA 1" to require the use of alloca, but please read
2075 the manual to determine safe values for YYMAXDEPTH in that case.
2076
2077 - Error token location.
2078 During error recovery, the location of the syntax error is updated
2079 to cover the whole sequence covered by the error token: it includes
2080 the shifted symbols thrown away during the first part of the error
2081 recovery, and the lookahead rejected during the second part.
2082
2083 - Semicolon changes:
2084 . Stray semicolons are no longer allowed at the start of a grammar.
2085 . Semicolons are now required after in-grammar declarations.
2086
2087 - Unescaped newlines are no longer allowed in character constants or
2088 string literals. They were never portable, and GCC 3.4.0 has
2089 dropped support for them. Better diagnostics are now generated if
2090 forget a closing quote.
2091
2092 - NUL bytes are no longer allowed in Bison string literals, unfortunately.
2093
2094 ** New features
2095
2096 - GLR grammars now support locations.
2097
2098 - New directive: %initial-action.
2099 This directive allows the user to run arbitrary code (including
2100 initializing @$) from yyparse before parsing starts.
2101
2102 - A new directive "%expect-rr N" specifies the expected number of
2103 reduce/reduce conflicts in GLR parsers.
2104
2105 - %token numbers can now be hexadecimal integers, e.g., "%token FOO 0x12d".
2106 This is a GNU extension.
2107
2108 - The option "--report=lookahead" was changed to "--report=look-ahead".
2109 [However, this was changed back after 2.3.]
2110
2111 - Experimental %destructor support has been added to lalr1.cc.
2112
2113 - New configure option --disable-yacc, to disable installation of the
2114 yacc command and -ly library introduced in 1.875 for POSIX conformance.
2115
2116 ** Bug fixes
2117
2118 - For now, %expect-count violations are now just warnings, not errors.
2119 This is for compatibility with Bison 1.75 and earlier (when there are
2120 reduce/reduce conflicts) and with Bison 1.30 and earlier (when there
2121 are too many or too few shift/reduce conflicts). However, in future
2122 versions of Bison we plan to improve the %expect machinery so that
2123 these violations will become errors again.
2124
2125 - Within Bison itself, numbers (e.g., goto numbers) are no longer
2126 arbitrarily limited to 16-bit counts.
2127
2128 - Semicolons are now allowed before "|" in grammar rules, as POSIX requires.
2129 \f
2130 * Changes in version 1.875, 2003-01-01:
2131
2132 ** The documentation license has been upgraded to version 1.2
2133 of the GNU Free Documentation License.
2134
2135 ** syntax error processing
2136
2137 - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error
2138 locations too. This fixes bugs in error-location computation.
2139
2140 - %destructor
2141 It is now possible to reclaim the memory associated to symbols
2142 discarded during error recovery. This feature is still experimental.
2143
2144 - %error-verbose
2145 This new directive is preferred over YYERROR_VERBOSE.
2146
2147 - #defining yyerror to steal internal variables is discouraged.
2148 It is not guaranteed to work forever.
2149
2150 ** POSIX conformance
2151
2152 - Semicolons are once again optional at the end of grammar rules.
2153 This reverts to the behavior of Bison 1.33 and earlier, and improves
2154 compatibility with Yacc.
2155
2156 - "parse error" -> "syntax error"
2157 Bison now uniformly uses the term "syntax error"; formerly, the code
2158 and manual sometimes used the term "parse error" instead. POSIX
2159 requires "syntax error" in diagnostics, and it was thought better to
2160 be consistent.
2161
2162 - The documentation now emphasizes that yylex and yyerror must be
2163 declared before use. C99 requires this.
2164
2165 - Bison now parses C99 lexical constructs like UCNs and
2166 backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires.
2167
2168 - File names are properly escaped in C output. E.g., foo\bar.y is
2169 output as "foo\\bar.y".
2170
2171 - Yacc command and library now available
2172 The Bison distribution now installs a "yacc" command, as POSIX requires.
2173 Also, Bison now installs a small library liby.a containing
2174 implementations of Yacc-compatible yyerror and main functions.
2175 This library is normally not useful, but POSIX requires it.
2176
2177 - Type clashes now generate warnings, not errors.
2178
2179 - If the user does not define YYSTYPE as a macro, Bison now declares it
2180 using typedef instead of defining it as a macro.
2181 For consistency, YYLTYPE is also declared instead of defined.
2182
2183 ** Other compatibility issues
2184
2185 - %union directives can now have a tag before the "{", e.g., the
2186 directive "%union foo {...}" now generates the C code
2187 "typedef union foo { ... } YYSTYPE;"; this is for Yacc compatibility.
2188 The default union tag is "YYSTYPE", for compatibility with Solaris 9 Yacc.
2189 For consistency, YYLTYPE's struct tag is now "YYLTYPE" not "yyltype".
2190 This is for compatibility with both Yacc and Bison 1.35.
2191
2192 - ";" is output before the terminating "}" of an action, for
2193 compatibility with Bison 1.35.
2194
2195 - Bison now uses a Yacc-style format for conflict reports, e.g.,
2196 "conflicts: 2 shift/reduce, 1 reduce/reduce".
2197
2198 - "yystype" and "yyltype" are now obsolescent macros instead of being
2199 typedefs or tags; they are no longer documented and are planned to be
2200 withdrawn in a future release.
2201
2202 ** GLR parser notes
2203
2204 - GLR and inline
2205 Users of Bison have to decide how they handle the portability of the
2206 C keyword "inline".
2207
2208 - "parsing stack overflow..." -> "parser stack overflow"
2209 GLR parsers now report "parser stack overflow" as per the Bison manual.
2210
2211 ** %parse-param and %lex-param
2212 The macros YYPARSE_PARAM and YYLEX_PARAM provide a means to pass
2213 additional context to yyparse and yylex. They suffer from several
2214 shortcomings:
2215
2216 - a single argument only can be added,
2217 - their types are weak (void *),
2218 - this context is not passed to ancillary functions such as yyerror,
2219 - only yacc.c parsers support them.
2220
2221 The new %parse-param/%lex-param directives provide a more precise control.
2222 For instance:
2223
2224 %parse-param {int *nastiness}
2225 %lex-param {int *nastiness}
2226 %parse-param {int *randomness}
2227
2228 results in the following signatures:
2229
2230 int yylex (int *nastiness);
2231 int yyparse (int *nastiness, int *randomness);
2232
2233 or, if both %pure-parser and %locations are used:
2234
2235 int yylex (YYSTYPE *lvalp, YYLTYPE *llocp, int *nastiness);
2236 int yyparse (int *nastiness, int *randomness);
2237
2238 ** Bison now warns if it detects conflicting outputs to the same file,
2239 e.g., it generates a warning for "bison -d -o foo.h foo.y" since
2240 that command outputs both code and header to foo.h.
2241
2242 ** #line in output files
2243 - --no-line works properly.
2244
2245 ** Bison can no longer be built by a K&R C compiler; it requires C89 or
2246 later to be built. This change originally took place a few versions
2247 ago, but nobody noticed until we recently asked someone to try
2248 building Bison with a K&R C compiler.
2249 \f
2250 * Changes in version 1.75, 2002-10-14:
2251
2252 ** Bison should now work on 64-bit hosts.
2253
2254 ** Indonesian translation thanks to Tedi Heriyanto.
2255
2256 ** GLR parsers
2257 Fix spurious parse errors.
2258
2259 ** Pure parsers
2260 Some people redefine yyerror to steal yyparse' private variables.
2261 Reenable this trick until an official feature replaces it.
2262
2263 ** Type Clashes
2264 In agreement with POSIX and with other Yaccs, leaving a default
2265 action is valid when $$ is untyped, and $1 typed:
2266
2267 untyped: ... typed;
2268
2269 but the converse remains an error:
2270
2271 typed: ... untyped;
2272
2273 ** Values of mid-rule actions
2274 The following code:
2275
2276 foo: { ... } { $$ = $1; } ...
2277
2278 was incorrectly rejected: $1 is defined in the second mid-rule
2279 action, and is equal to the $$ of the first mid-rule action.
2280 \f
2281 * Changes in version 1.50, 2002-10-04:
2282
2283 ** GLR parsing
2284 The declaration
2285 %glr-parser
2286 causes Bison to produce a Generalized LR (GLR) parser, capable of handling
2287 almost any context-free grammar, ambiguous or not. The new declarations
2288 %dprec and %merge on grammar rules allow parse-time resolution of
2289 ambiguities. Contributed by Paul Hilfinger.
2290
2291 Unfortunately Bison 1.50 does not work properly on 64-bit hosts
2292 like the Alpha, so please stick to 32-bit hosts for now.
2293
2294 ** Output Directory
2295 When not in Yacc compatibility mode, when the output file was not
2296 specified, running "bison foo/bar.y" created "foo/bar.c". It
2297 now creates "bar.c".
2298
2299 ** Undefined token
2300 The undefined token was systematically mapped to 2 which prevented
2301 the use of 2 by the user. This is no longer the case.
2302
2303 ** Unknown token numbers
2304 If yylex returned an out of range value, yyparse could die. This is
2305 no longer the case.
2306
2307 ** Error token
2308 According to POSIX, the error token must be 256.
2309 Bison extends this requirement by making it a preference: *if* the
2310 user specified that one of her tokens is numbered 256, then error
2311 will be mapped onto another number.
2312
2313 ** Verbose error messages
2314 They no longer report "..., expecting error or..." for states where
2315 error recovery is possible.
2316
2317 ** End token
2318 Defaults to "$end" instead of "$".
2319
2320 ** Error recovery now conforms to documentation and to POSIX
2321 When a Bison-generated parser encounters a syntax error, it now pops
2322 the stack until it finds a state that allows shifting the error
2323 token. Formerly, it popped the stack until it found a state that
2324 allowed some non-error action other than a default reduction on the
2325 error token. The new behavior has long been the documented behavior,
2326 and has long been required by POSIX. For more details, please see
2327 Paul Eggert, "Reductions during Bison error handling" (2002-05-20)
2328 <http://lists.gnu.org/archive/html/bug-bison/2002-05/msg00038.html>.
2329
2330 ** Traces
2331 Popped tokens and nonterminals are now reported.
2332
2333 ** Larger grammars
2334 Larger grammars are now supported (larger token numbers, larger grammar
2335 size (= sum of the LHS and RHS lengths), larger LALR tables).
2336 Formerly, many of these numbers ran afoul of 16-bit limits;
2337 now these limits are 32 bits on most hosts.
2338
2339 ** Explicit initial rule
2340 Bison used to play hacks with the initial rule, which the user does
2341 not write. It is now explicit, and visible in the reports and
2342 graphs as rule 0.
2343
2344 ** Useless rules
2345 Before, Bison reported the useless rules, but, although not used,
2346 included them in the parsers. They are now actually removed.
2347
2348 ** Useless rules, useless nonterminals
2349 They are now reported, as a warning, with their locations.
2350
2351 ** Rules never reduced
2352 Rules that can never be reduced because of conflicts are now
2353 reported.
2354
2355 ** Incorrect "Token not used"
2356 On a grammar such as
2357
2358 %token useless useful
2359 %%
2360 exp: '0' %prec useful;
2361
2362 where a token was used to set the precedence of the last rule,
2363 bison reported both "useful" and "useless" as useless tokens.
2364
2365 ** Revert the C++ namespace changes introduced in 1.31
2366 as they caused too many portability hassles.
2367
2368 ** Default locations
2369 By an accident of design, the default computation of @$ was
2370 performed after another default computation was performed: @$ = @1.
2371 The latter is now removed: YYLLOC_DEFAULT is fully responsible of
2372 the computation of @$.
2373
2374 ** Token end-of-file
2375 The token end of file may be specified by the user, in which case,
2376 the user symbol is used in the reports, the graphs, and the verbose
2377 error messages instead of "$end", which remains being the default.
2378 For instance
2379 %token MYEOF 0
2380 or
2381 %token MYEOF 0 "end of file"
2382
2383 ** Semantic parser
2384 This old option, which has been broken for ages, is removed.
2385
2386 ** New translations
2387 Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
2388 Croatian, thanks to Denis Lackovic.
2389
2390 ** Incorrect token definitions
2391 When given
2392 %token 'a' "A"
2393 bison used to output
2394 #define 'a' 65
2395
2396 ** Token definitions as enums
2397 Tokens are output both as the traditional #define's, and, provided
2398 the compiler supports ANSI C or is a C++ compiler, as enums.
2399 This lets debuggers display names instead of integers.
2400
2401 ** Reports
2402 In addition to --verbose, bison supports --report=THINGS, which
2403 produces additional information:
2404 - itemset
2405 complete the core item sets with their closure
2406 - lookahead [changed to "look-ahead" in 1.875e through 2.3, but changed back]
2407 explicitly associate lookahead tokens to items
2408 - solved
2409 describe shift/reduce conflicts solving.
2410 Bison used to systematically output this information on top of
2411 the report. Solved conflicts are now attached to their states.
2412
2413 ** Type clashes
2414 Previous versions don't complain when there is a type clash on
2415 the default action if the rule has a mid-rule action, such as in:
2416
2417 %type <foo> bar
2418 %%
2419 bar: '0' {} '0';
2420
2421 This is fixed.
2422
2423 ** GNU M4 is now required when using Bison.
2424 \f
2425 * Changes in version 1.35, 2002-03-25:
2426
2427 ** C Skeleton
2428 Some projects use Bison's C parser with C++ compilers, and define
2429 YYSTYPE as a class. The recent adjustment of C parsers for data
2430 alignment and 64 bit architectures made this impossible.
2431
2432 Because for the time being no real solution for C++ parser
2433 generation exists, kludges were implemented in the parser to
2434 maintain this use. In the future, when Bison has C++ parsers, this
2435 kludge will be disabled.
2436
2437 This kludge also addresses some C++ problems when the stack was
2438 extended.
2439 \f
2440 * Changes in version 1.34, 2002-03-12:
2441
2442 ** File name clashes are detected
2443 $ bison foo.y -d -o foo.x
2444 fatal error: header and parser would both be named "foo.x"
2445
2446 ** A missing ";" at the end of a rule triggers a warning
2447 In accordance with POSIX, and in agreement with other
2448 Yacc implementations, Bison will mandate this semicolon in the near
2449 future. This eases the implementation of a Bison parser of Bison
2450 grammars by making this grammar LALR(1) instead of LR(2). To
2451 facilitate the transition, this release introduces a warning.
2452
2453 ** Revert the C++ namespace changes introduced in 1.31, as they caused too
2454 many portability hassles.
2455
2456 ** DJGPP support added.
2457
2458 ** Fix test suite portability problems.
2459 \f
2460 * Changes in version 1.33, 2002-02-07:
2461
2462 ** Fix C++ issues
2463 Groff could not be compiled for the definition of size_t was lacking
2464 under some conditions.
2465
2466 ** Catch invalid @n
2467 As is done with $n.
2468 \f
2469 * Changes in version 1.32, 2002-01-23:
2470
2471 ** Fix Yacc output file names
2472
2473 ** Portability fixes
2474
2475 ** Italian, Dutch translations
2476 \f
2477 * Changes in version 1.31, 2002-01-14:
2478
2479 ** Many Bug Fixes
2480
2481 ** GNU Gettext and %expect
2482 GNU Gettext asserts 10 s/r conflicts, but there are 7. Now that
2483 Bison dies on incorrect %expectations, we fear there will be
2484 too many bug reports for Gettext, so _for the time being_, %expect
2485 does not trigger an error when the input file is named "plural.y".
2486
2487 ** Use of alloca in parsers
2488 If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use
2489 malloc exclusively. Since 1.29, but was not NEWS'ed.
2490
2491 alloca is used only when compiled with GCC, to avoid portability
2492 problems as on AIX.
2493
2494 ** yyparse now returns 2 if memory is exhausted; formerly it dumped core.
2495
2496 ** When the generated parser lacks debugging code, YYDEBUG is now 0
2497 (as POSIX requires) instead of being undefined.
2498
2499 ** User Actions
2500 Bison has always permitted actions such as { $$ = $1 }: it adds the
2501 ending semicolon. Now if in Yacc compatibility mode, the semicolon
2502 is no longer output: one has to write { $$ = $1; }.
2503
2504 ** Better C++ compliance
2505 The output parsers try to respect C++ namespaces.
2506 [This turned out to be a failed experiment, and it was reverted later.]
2507
2508 ** Reduced Grammars
2509 Fixed bugs when reporting useless nonterminals.
2510
2511 ** 64 bit hosts
2512 The parsers work properly on 64 bit hosts.
2513
2514 ** Error messages
2515 Some calls to strerror resulted in scrambled or missing error messages.
2516
2517 ** %expect
2518 When the number of shift/reduce conflicts is correct, don't issue
2519 any warning.
2520
2521 ** The verbose report includes the rule line numbers.
2522
2523 ** Rule line numbers are fixed in traces.
2524
2525 ** Swedish translation
2526
2527 ** Parse errors
2528 Verbose parse error messages from the parsers are better looking.
2529 Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'(''
2530 Now: parse error: unexpected '/', expecting "number" or '-' or '('
2531
2532 ** Fixed parser memory leaks.
2533 When the generated parser was using malloc to extend its stacks, the
2534 previous allocations were not freed.
2535
2536 ** Fixed verbose output file.
2537 Some newlines were missing.
2538 Some conflicts in state descriptions were missing.
2539
2540 ** Fixed conflict report.
2541 Option -v was needed to get the result.
2542
2543 ** %expect
2544 Was not used.
2545 Mismatches are errors, not warnings.
2546
2547 ** Fixed incorrect processing of some invalid input.
2548
2549 ** Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H.
2550
2551 ** Fixed some typos in the documentation.
2552
2553 ** %token MY_EOF 0 is supported.
2554 Before, MY_EOF was silently renumbered as 257.
2555
2556 ** doc/refcard.tex is updated.
2557
2558 ** %output, %file-prefix, %name-prefix.
2559 New.
2560
2561 ** --output
2562 New, aliasing "--output-file".
2563 \f
2564 * Changes in version 1.30, 2001-10-26:
2565
2566 ** "--defines" and "--graph" have now an optional argument which is the
2567 output file name. "-d" and "-g" do not change; they do not take any
2568 argument.
2569
2570 ** "%source_extension" and "%header_extension" are removed, failed
2571 experiment.
2572
2573 ** Portability fixes.
2574 \f
2575 * Changes in version 1.29, 2001-09-07:
2576
2577 ** The output file does not define const, as this caused problems when used
2578 with common autoconfiguration schemes. If you still use ancient compilers
2579 that lack const, compile with the equivalent of the C compiler option
2580 "-Dconst=". Autoconf's AC_C_CONST macro provides one way to do this.
2581
2582 ** Added "-g" and "--graph".
2583
2584 ** The Bison manual is now distributed under the terms of the GNU FDL.
2585
2586 ** The input and the output files has automatically a similar extension.
2587
2588 ** Russian translation added.
2589
2590 ** NLS support updated; should hopefully be less troublesome.
2591
2592 ** Added the old Bison reference card.
2593
2594 ** Added "--locations" and "%locations".
2595
2596 ** Added "-S" and "--skeleton".
2597
2598 ** "%raw", "-r", "--raw" is disabled.
2599
2600 ** Special characters are escaped when output. This solves the problems
2601 of the #line lines with path names including backslashes.
2602
2603 ** New directives.
2604 "%yacc", "%fixed_output_files", "%defines", "%no_parser", "%verbose",
2605 "%debug", "%source_extension" and "%header_extension".
2606
2607 ** @$
2608 Automatic location tracking.
2609 \f
2610 * Changes in version 1.28, 1999-07-06:
2611
2612 ** Should compile better now with K&R compilers.
2613
2614 ** Added NLS.
2615
2616 ** Fixed a problem with escaping the double quote character.
2617
2618 ** There is now a FAQ.
2619 \f
2620 * Changes in version 1.27:
2621
2622 ** The make rule which prevented bison.simple from being created on
2623 some systems has been fixed.
2624 \f
2625 * Changes in version 1.26:
2626
2627 ** Bison now uses Automake.
2628
2629 ** New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
2630
2631 ** Token numbers now start at 257 as previously documented, not 258.
2632
2633 ** Bison honors the TMPDIR environment variable.
2634
2635 ** A couple of buffer overruns have been fixed.
2636
2637 ** Problems when closing files should now be reported.
2638
2639 ** Generated parsers should now work even on operating systems which do
2640 not provide alloca().
2641 \f
2642 * Changes in version 1.25, 1995-10-16:
2643
2644 ** Errors in the input grammar are not fatal; Bison keeps reading
2645 the grammar file, and reports all the errors found in it.
2646
2647 ** Tokens can now be specified as multiple-character strings: for
2648 example, you could use "<=" for a token which looks like <=, instead
2649 of choosing a name like LESSEQ.
2650
2651 ** The %token_table declaration says to write a table of tokens (names
2652 and numbers) into the parser file. The yylex function can use this
2653 table to recognize multiple-character string tokens, or for other
2654 purposes.
2655
2656 ** The %no_lines declaration says not to generate any #line preprocessor
2657 directives in the parser file.
2658
2659 ** The %raw declaration says to use internal Bison token numbers, not
2660 Yacc-compatible token numbers, when token names are defined as macros.
2661
2662 ** The --no-parser option produces the parser tables without including
2663 the parser engine; a project can now use its own parser engine.
2664 The actions go into a separate file called NAME.act, in the form of
2665 a switch statement body.
2666 \f
2667 * Changes in version 1.23:
2668
2669 The user can define YYPARSE_PARAM as the name of an argument to be
2670 passed into yyparse. The argument should have type void *. It should
2671 actually point to an object. Grammar actions can access the variable
2672 by casting it to the proper pointer type.
2673
2674 Line numbers in output file corrected.
2675 \f
2676 * Changes in version 1.22:
2677
2678 --help option added.
2679 \f
2680 * Changes in version 1.20:
2681
2682 Output file does not redefine const for C++.
2683
2684 -----
2685
2686 Copyright (C) 1995-2013 Free Software Foundation, Inc.
2687
2688 This file is part of Bison, the GNU Parser Generator.
2689
2690 This program is free software: you can redistribute it and/or modify
2691 it under the terms of the GNU General Public License as published by
2692 the Free Software Foundation, either version 3 of the License, or
2693 (at your option) any later version.
2694
2695 This program is distributed in the hope that it will be useful,
2696 but WITHOUT ANY WARRANTY; without even the implied warranty of
2697 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
2698 GNU General Public License for more details.
2699
2700 You should have received a copy of the GNU General Public License
2701 along with this program. If not, see <http://www.gnu.org/licenses/>.
2702
2703 LocalWords: yacc YYBACKUP glr GCC lalr ArrayIndexOutOfBoundsException nullptr
2704 LocalWords: cplusplus liby rpl fprintf mfcalc Wyacc stmt cond expr mk sym lr
2705 LocalWords: IELR ielr Lookahead YYERROR nonassoc LALR's api lookaheads yychar
2706 LocalWords: destructor lookahead YYRHSLOC YYLLOC Rhs ifndef YYFAIL cpp sr rr
2707 LocalWords: preprocessor initializer Wno Wnone Werror FreeBSD prec livelocks
2708 LocalWords: Solaris AIX UX RHEL Tru LHS gcc's Wundef YYENABLE NLS YYLTYPE VCG
2709 LocalWords: yyerror cpp's Wunused yylval yylloc prepend yyparse yylex yypush
2710 LocalWords: Graphviz xml nonterminals midrule destructor's YYSTYPE typedef ly
2711 LocalWords: CHR chr printf stdout namespace preprocessing enum pre include's
2712 LocalWords: YYRECOVERING nonfree destructors YYABORT YYACCEPT params enums de
2713 LocalWords: struct yystype DJGPP lex param Haible NUM alloca YYSTACK NUL goto
2714 LocalWords: YYMAXDEPTH Unescaped UCNs YYLTYPE's yyltype typedefs inline Yaccs
2715 LocalWords: Heriyanto Reenable dprec Hilfinger Eggert MYEOF Folle Menezes EOF
2716 LocalWords: Lackovic define's itemset Groff Gettext malloc NEWS'ed YYDEBUG YY
2717 LocalWords: namespaces strerror const autoconfiguration Dconst Autoconf's FDL
2718 LocalWords: Automake TMPDIR LESSEQ ylwrap endif yydebug YYTOKEN YYLSP ival hh
2719 LocalWords: extern YYTOKENTYPE TOKENTYPE yytokentype tokentype STYPE lval pdf
2720 LocalWords: lang yyoutput dvi html ps POSIX lvalp llocp Wother nterm arg init
2721 LocalWords: TOK calc yyo fval Wconflicts parsers yystackp yyval yynerrs
2722 LocalWords: Théophile Ranquet Santet fno fnone stype associativity Tolmer
2723 LocalWords: Wprecedence Rassoul Wempty Paolo Bonzini parser's Michiel loc
2724 LocalWords: redeclaration sval fcaret reentrant XSLT xsl Wmaybe yyvsp Tedi
2725 LocalWords: pragmas noreturn untyped Rozenman unexpanded Wojciech Polak
2726 LocalWords: Alexandre MERCHANTABILITY yytype
2727
2728 Local Variables:
2729 mode: outline
2730 fill-column: 76
2731 End: