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1GNU Bison NEWS
2
3* Noteworthy changes in release ?.? (????-??-??) [?]
4
5** Incompatible changes
6
7*** Obsolete features
8
9 Support for YYFAIL is removed (deprecated in Bison 2.4.2).
10 Support for yystype and yyltype (instead of YYSTYPE and YYLTYPE)
11 is removed (deprecated in Bison 1.875).
12 Support for YYPARSE_PARAM is removed (deprecated in Bison 1.875).
13
14** Warnings
15
16*** Deprecated constructs
17
18 The new 'deprecated' warning category flags obsolete constructs whose
19 support will be discontinued. It is enabled by default. These warnings
20 used to be reported as 'other' warnings.
21
22*** Warning categories are now displayed
23
24 For instance:
25
26 foo.y:4.6: warning: type clash on default action: <foo> != <bar> [-Wother]
27
28*** Useless semantic types
29
30 Bison now warns about useless (uninhabited) semantic types. Since
31 semantic types are not declared to Bison (they are defined in the opaque
32 %union structure), it is %printer/%destructor directives about useless
33 types that trigger the warning:
34
35 %token <type1> term
36 %type <type2> nterm
37 %printer {} <type1> <type3>
38 %destructor {} <type2> <type4>
39 %%
40 nterm: term { $$ = $1; };
41
42 3.28-34: warning: type <type3> is used, but is not associated to any symbol
43 4.28-34: warning: type <type4> is used, but is not associated to any symbol
44
45*** Undefined but unused symbols
46
47 Bison used to raise an error for undefined symbols that are not used in
48 the grammar. This is now only a warning.
49
50 %printer {} symbol1
51 %destructor {} symbol2
52 %type <type> symbol3
53 %%
54 exp: "a";
55
56*** Useless destructors or printers
57
58 Bison now warns about useless destructors or printers. In the following
59 example, the printer for <type1>, and the destructor for <type2> are
60 useless: all symbols of <type1> (token1) already have a printer, and all
61 symbols of type <type2> (token2) already have a destructor.
62
63 %token <type1> token1
64 <type2> token2
65 <type3> token3
66 <type4> token4
67 %printer {} token1 <type1> <type3>
68 %destructor {} token2 <type2> <type4>
69
70*** Conflicts
71
72 The warnings and error messages about shift/reduce and reduce/reduce
73 conflicts have been normalized. For instance on the following foo.y file:
74
75 %glr-parser
76 %%
77 exp: exp '+' exp | '0' | '0';
78
79 compare the previous version of bison:
80
81 $ bison foo.y
82 foo.y: conflicts: 1 shift/reduce, 2 reduce/reduce
83 $ bison -Werror foo.y
84 bison: warnings being treated as errors
85 foo.y: conflicts: 1 shift/reduce, 2 reduce/reduce
86
87 with the new behavior:
88
89 $ bison foo.y
90 foo.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
91 foo.y: warning: 2 reduce/reduce conflicts [-Wconflicts-rr]
92 $ bison -Werror foo.y
93 foo.y: error: 1 shift/reduce conflict [-Werror=conflicts-sr]
94 foo.y: error: 2 reduce/reduce conflicts [-Werror=conflicts-rr]
95
96 When %expect or %expect-rr is used, such as with bar.y:
97
98 %expect 0
99 %glr-parser
100 %%
101 exp: exp '+' exp | '0' | '0';
102
103 Former behavior:
104
105 $ bison bar.y
106 bar.y: conflicts: 1 shift/reduce, 2 reduce/reduce
107 bar.y: expected 0 shift/reduce conflicts
108 bar.y: expected 0 reduce/reduce conflicts
109
110 New one:
111
112 $ bison bar.y
113 bar.y: error: shift/reduce conflicts: 1 found, 0 expected
114 bar.y: error: reduce/reduce conflicts: 2 found, 0 expected
115
116** Additional yylex/yyparse arguments
117
118 The new directive %param declares additional arguments to both yylex and
119 yyparse. The %lex-param, %parse-param, and %param directives support one
120 or more arguments. Instead of
121
122 %lex-param {arg1_type *arg1}
123 %lex-param {arg2_type *arg2}
124 %parse-param {arg1_type *arg1}
125 %parse-param {arg2_type *arg2}
126
127 one may now declare
128
129 %param {arg1_type *arg1} {arg2_type *arg2}
130
131** Java skeleton improvements
132
133 The constants for token names were moved to the Lexer interface. Also, it
134 is possible to add code to the parser's constructors using "%code init"
135 and "%define init_throws".
136
137** C++ skeletons improvements
138
139*** The parser header is no longer mandatory (lalr1.cc, glr.cc)
140
141 Using %defines is now optional. Without it, the needed support classes
142 are defined in the generated parser, instead of additional files (such as
143 location.hh, position.hh and stack.hh).
144
145*** Locations are no longer mandatory (lalr1.cc, glr.cc)
146
147 Both lalr1.cc and glr.cc no longer require %location.
148
149*** syntax_error exception (lalr1.cc)
150
151 The C++ parser features a syntax_error exception, which can be
152 thrown from the scanner or from user rules to raise syntax errors.
153 This facilitates reporting errors caught in sub-functions (e.g.,
154 rejecting too large integral literals from a conversion function
155 used by the scanner, or rejecting invalid combinations from a
156 factory invoked by the user actions).
157
158** Variable api.tokens.prefix
159
160 The variable api.tokens.prefix changes the way tokens are identified in
161 the generated files. This is especially useful to avoid collisions
162 with identifiers in the target language. For instance
163
164 %token FILE for ERROR
165 %define api.tokens.prefix "TOK_"
166 %%
167 start: FILE for ERROR;
168
169 will generate the definition of the symbols TOK_FILE, TOK_for, and
170 TOK_ERROR in the generated sources. In particular, the scanner must
171 use these prefixed token names, although the grammar itself still
172 uses the short names (as in the sample rule given above).
173
174** Variable api.namespace
175
176 The 'namespace' variable is renamed 'api.namespace'. Backward
177 compatibility is ensured, but upgrading is recommended.
178
179** Variable parse.error
180
181 This variable controls the verbosity of error messages. The use of the
182 %error-verbose directive is deprecated in favor of "%define parse.error
183 verbose".
184
185** Semantic predicates
186
187 The new, experimental, semantic-predicate feature allows actions of the
188 form "%?{ BOOLEAN-EXPRESSION }", which cause syntax errors (as for
189 YYERROR) if the expression evaluates to 0, and are evaluated immediately
190 in GLR parsers, rather than being deferred. The result is that they allow
191 the programmer to prune possible parses based on the values of run-time
192 expressions.
193
194** The directive %expect-rr is now an error in non GLR mode
195
196 It used to be an error only if used in non GLR mode, _and_ if there are
197 reduce/reduce conflicts.
198
199* Noteworthy changes in release ?.? (????-??-??) [?]
200
201** Bug fixes
202
203 Bugs in the test suite have been fixed.
204
205 Some errors in translations have been addressed, and --help now directs
206 users to the appropriate place to report them.
207
208 Stray Info files shipped by accident are removed.
209
210 Incorrect definitions of YY_, issued by yacc.c when no parser header is
211 generated, are removed.
212
213** Changes in the format of errors and exceptions output
214
215 This used to be the format of many error reports:
216
217 foo.y:5.10-24: result type clash on merge function 'merge': <t3> != <t2>
218 foo.y:4.13-27: previous declaration
219
220 It is now:
221
222 foo.y:5.10-25: result type clash on merge function 'merge': <t3> != <t2>
223 foo.y:4.13-27: previous declaration
224
225* Noteworthy changes in release 2.6.2 (2012-08-03) [stable]
226
227** Bug fixes
228
229 Buffer overruns, complaints from Flex, and portability issues in the test
230 suite have been fixed.
231
232** Spaces in %lex- and %parse-param (lalr1.cc, glr.cc)
233
234 Trailing end-of-lines in %parse-param or %lex-param would result in
235 invalid C++. This is fixed.
236
237** Spurious spaces and end-of-lines
238
239 The generated files no longer end (nor start) with empty lines.
240
241* Noteworthy changes in release 2.6.1 (2012-07-30) [stable]
242
243 Bison no longer executes user-specified M4 code when processing a grammar.
244
245** Future Changes
246
247 In addition to the removal of the features announced in Bison 2.6, the
248 next major release will remove the "Temporary hack for adding a semicolon
249 to the user action", as announced in the release 2.5. Instead of:
250
251 exp: exp "+" exp { $$ = $1 + $3 };
252
253 write:
254
255 exp: exp "+" exp { $$ = $1 + $3; };
256
257** Bug fixes
258
259*** Type names are now properly escaped.
260
261*** glr.cc: set_debug_level and debug_level work as expected.
262
263*** Stray @ or $ in actions
264
265 While Bison used to warn about stray $ or @ in action rules, it did not
266 for other actions such as printers, destructors, or initial actions. It
267 now does.
268
269** Type names in actions
270
271 For consistency with rule actions, it is now possible to qualify $$ by a
272 type-name in destructors, printers, and initial actions. For instance:
273
274 %printer { fprintf (yyo, "(%d, %f)", $<ival>$, $<fval>$); } <*> <>;
275
276 will display two values for each typed and untyped symbol (provided
277 that YYSTYPE has both "ival" and "fval" fields).
278
279* Noteworthy changes in release 2.6 (2012-07-19) [stable]
280
281** Future changes:
282
283 The next major release of Bison will drop support for the following
284 deprecated features. Please report disagreements to bug-bison@gnu.org.
285
286*** K&R C parsers
287
288 Support for generating parsers in K&R C will be removed. Parsers
289 generated for C support ISO C90, and are tested with ISO C99 and ISO C11
290 compilers.
291
292*** Features deprecated since Bison 1.875
293
294 The definitions of yystype and yyltype will be removed; use YYSTYPE and
295 YYLTYPE.
296
297 YYPARSE_PARAM and YYLEX_PARAM, deprecated in favor of %parse-param and
298 %lex-param, will no longer be supported.
299
300 Support for the preprocessor symbol YYERROR_VERBOSE will be removed, use
301 %error-verbose.
302
303*** The generated header will be included (yacc.c)
304
305 Instead of duplicating the content of the generated header (definition of
306 YYSTYPE, yyparse declaration etc.), the generated parser will include it,
307 as is already the case for GLR or C++ parsers. This change is deferred
308 because existing versions of ylwrap (e.g., Automake 1.12.1) do not support
309 it.
310
311** Generated Parser Headers
312
313*** Guards (yacc.c, glr.c, glr.cc)
314
315 The generated headers are now guarded, as is already the case for C++
316 parsers (lalr1.cc). For instance, with --defines=foo.h:
317
318 #ifndef YY_FOO_H
319 # define YY_FOO_H
320 ...
321 #endif /* !YY_FOO_H */
322
323*** New declarations (yacc.c, glr.c)
324
325 The generated header now declares yydebug and yyparse. Both honor
326 --name-prefix=bar_, and yield
327
328 int bar_parse (void);
329
330 rather than
331
332 #define yyparse bar_parse
333 int yyparse (void);
334
335 in order to facilitate the inclusion of several parser headers inside a
336 single compilation unit.
337
338*** Exported symbols in C++
339
340 The symbols YYTOKEN_TABLE and YYERROR_VERBOSE, which were defined in the
341 header, are removed, as they prevent the possibility of including several
342 generated headers from a single compilation unit.
343
344*** YYLSP_NEEDED
345
346 For the same reasons, the undocumented and unused macro YYLSP_NEEDED is no
347 longer defined.
348
349** New %define variable: api.prefix
350
351 Now that the generated headers are more complete and properly protected
352 against multiple inclusions, constant names, such as YYSTYPE are a
353 problem. While yyparse and others are properly renamed by %name-prefix,
354 YYSTYPE, YYDEBUG and others have never been affected by it. Because it
355 would introduce backward compatibility issues in projects not expecting
356 YYSTYPE to be renamed, instead of changing the behavior of %name-prefix,
357 it is deprecated in favor of a new %define variable: api.prefix.
358
359 The following examples compares both:
360
361 %name-prefix "bar_" | %define api.prefix "bar_"
362 %token <ival> FOO %token <ival> FOO
363 %union { int ival; } %union { int ival; }
364 %% %%
365 exp: 'a'; exp: 'a';
366
367 bison generates:
368
369 #ifndef BAR_FOO_H #ifndef BAR_FOO_H
370 # define BAR_FOO_H # define BAR_FOO_H
371
372 /* Enabling traces. */ /* Enabling traces. */
373 # ifndef YYDEBUG | # ifndef BAR_DEBUG
374 > # if defined YYDEBUG
375 > # if YYDEBUG
376 > # define BAR_DEBUG 1
377 > # else
378 > # define BAR_DEBUG 0
379 > # endif
380 > # else
381 # define YYDEBUG 0 | # define BAR_DEBUG 0
382 > # endif
383 # endif | # endif
384
385 # if YYDEBUG | # if BAR_DEBUG
386 extern int bar_debug; extern int bar_debug;
387 # endif # endif
388
389 /* Tokens. */ /* Tokens. */
390 # ifndef YYTOKENTYPE | # ifndef BAR_TOKENTYPE
391 # define YYTOKENTYPE | # define BAR_TOKENTYPE
392 enum yytokentype { | enum bar_tokentype {
393 FOO = 258 FOO = 258
394 }; };
395 # endif # endif
396
397 #if ! defined YYSTYPE \ | #if ! defined BAR_STYPE \
398 && ! defined YYSTYPE_IS_DECLARED | && ! defined BAR_STYPE_IS_DECLARED
399 typedef union YYSTYPE | typedef union BAR_STYPE
400 { {
401 int ival; int ival;
402 } YYSTYPE; | } BAR_STYPE;
403 # define YYSTYPE_IS_DECLARED 1 | # define BAR_STYPE_IS_DECLARED 1
404 #endif #endif
405
406 extern YYSTYPE bar_lval; | extern BAR_STYPE bar_lval;
407
408 int bar_parse (void); int bar_parse (void);
409
410 #endif /* !BAR_FOO_H */ #endif /* !BAR_FOO_H */
411
412* Noteworthy changes in release 2.5.1 (2012-06-05) [stable]
413
414** Future changes:
415
416 The next major release will drop support for generating parsers in K&R C.
417
418** yacc.c: YYBACKUP works as expected.
419
420** glr.c improvements:
421
422*** Location support is eliminated when not requested:
423
424 GLR parsers used to include location-related code even when locations were
425 not requested, and therefore not even usable.
426
427*** __attribute__ is preserved:
428
429 __attribute__ is no longer disabled when __STRICT_ANSI__ is defined (i.e.,
430 when -std is passed to GCC).
431
432** lalr1.java: several fixes:
433
434 The Java parser no longer throws ArrayIndexOutOfBoundsException if the
435 first token leads to a syntax error. Some minor clean ups.
436
437** Changes for C++:
438
439*** C++11 compatibility:
440
441 C and C++ parsers use "nullptr" instead of "0" when __cplusplus is 201103L
442 or higher.
443
444*** Header guards
445
446 The header files such as "parser.hh", "location.hh", etc. used a constant
447 name for preprocessor guards, for instance:
448
449 #ifndef BISON_LOCATION_HH
450 # define BISON_LOCATION_HH
451 ...
452 #endif // !BISON_LOCATION_HH
453
454 The inclusion guard is now computed from "PREFIX/FILE-NAME", where lower
455 case characters are converted to upper case, and series of
456 non-alphanumerical characters are converted to an underscore.
457
458 With "bison -o lang++/parser.cc", "location.hh" would now include:
459
460 #ifndef YY_LANG_LOCATION_HH
461 # define YY_LANG_LOCATION_HH
462 ...
463 #endif // !YY_LANG_LOCATION_HH
464
465*** C++ locations:
466
467 The position and location constructors (and their initialize methods)
468 accept new arguments for line and column. Several issues in the
469 documentation were fixed.
470
471** liby is no longer asking for "rpl_fprintf" on some platforms.
472
473** Changes in the manual:
474
475*** %printer is documented
476
477 The "%printer" directive, supported since at least Bison 1.50, is finally
478 documented. The "mfcalc" example is extended to demonstrate it.
479
480 For consistency with the C skeletons, the C++ parsers now also support
481 "yyoutput" (as an alias to "debug_stream ()").
482
483*** Several improvements have been made:
484
485 The layout for grammar excerpts was changed to a more compact scheme.
486 Named references are motivated. The description of the automaton
487 description file (*.output) is updated to the current format. Incorrect
488 index entries were fixed. Some other errors were fixed.
489
490** Building bison:
491
492*** Conflicting prototypes with recent/modified Flex.
493
494 Fixed build problems with the current, unreleased, version of Flex, and
495 some modified versions of 2.5.35, which have modified function prototypes.
496
497*** Warnings during the build procedure have been eliminated.
498
499*** Several portability problems in the test suite have been fixed:
500
501 This includes warnings with some compilers, unexpected behavior of tools
502 such as diff, warning messages from the test suite itself, etc.
503
504*** The install-pdf target works properly:
505
506 Running "make install-pdf" (or -dvi, -html, -info, and -ps) no longer
507 halts in the middle of its course.
508
509* Changes in version 2.5 (2011-05-14):
510
511** Grammar symbol names can now contain non-initial dashes:
512
513 Consistently with directives (such as %error-verbose) and with
514 %define variables (e.g. push-pull), grammar symbol names may contain
515 dashes in any position except the beginning. This is a GNU
516 extension over POSIX Yacc. Thus, use of this extension is reported
517 by -Wyacc and rejected in Yacc mode (--yacc).
518
519** Named references:
520
521 Historically, Yacc and Bison have supported positional references
522 ($n, $$) to allow access to symbol values from inside of semantic
523 actions code.
524
525 Starting from this version, Bison can also accept named references.
526 When no ambiguity is possible, original symbol names may be used
527 as named references:
528
529 if_stmt : "if" cond_expr "then" then_stmt ';'
530 { $if_stmt = mk_if_stmt($cond_expr, $then_stmt); }
531
532 In the more common case, explicit names may be declared:
533
534 stmt[res] : "if" expr[cond] "then" stmt[then] "else" stmt[else] ';'
535 { $res = mk_if_stmt($cond, $then, $else); }
536
537 Location information is also accessible using @name syntax. When
538 accessing symbol names containing dots or dashes, explicit bracketing
539 ($[sym.1]) must be used.
540
541 These features are experimental in this version. More user feedback
542 will help to stabilize them.
543
544** IELR(1) and canonical LR(1):
545
546 IELR(1) is a minimal LR(1) parser table generation algorithm. That
547 is, given any context-free grammar, IELR(1) generates parser tables
548 with the full language-recognition power of canonical LR(1) but with
549 nearly the same number of parser states as LALR(1). This reduction
550 in parser states is often an order of magnitude. More importantly,
551 because canonical LR(1)'s extra parser states may contain duplicate
552 conflicts in the case of non-LR(1) grammars, the number of conflicts
553 for IELR(1) is often an order of magnitude less as well. This can
554 significantly reduce the complexity of developing of a grammar.
555
556 Bison can now generate IELR(1) and canonical LR(1) parser tables in
557 place of its traditional LALR(1) parser tables, which remain the
558 default. You can specify the type of parser tables in the grammar
559 file with these directives:
560
561 %define lr.type lalr
562 %define lr.type ielr
563 %define lr.type canonical-lr
564
565 The default-reduction optimization in the parser tables can also be
566 adjusted using "%define lr.default-reductions". For details on both
567 of these features, see the new section "Tuning LR" in the Bison
568 manual.
569
570 These features are experimental. More user feedback will help to
571 stabilize them.
572
573** LAC (Lookahead Correction) for syntax error handling:
574
575 Canonical LR, IELR, and LALR can suffer from a couple of problems
576 upon encountering a syntax error. First, the parser might perform
577 additional parser stack reductions before discovering the syntax
578 error. Such reductions can perform user semantic actions that are
579 unexpected because they are based on an invalid token, and they
580 cause error recovery to begin in a different syntactic context than
581 the one in which the invalid token was encountered. Second, when
582 verbose error messages are enabled (with %error-verbose or the
583 obsolete "#define YYERROR_VERBOSE"), the expected token list in the
584 syntax error message can both contain invalid tokens and omit valid
585 tokens.
586
587 The culprits for the above problems are %nonassoc, default
588 reductions in inconsistent states, and parser state merging. Thus,
589 IELR and LALR suffer the most. Canonical LR can suffer only if
590 %nonassoc is used or if default reductions are enabled for
591 inconsistent states.
592
593 LAC is a new mechanism within the parsing algorithm that solves
594 these problems for canonical LR, IELR, and LALR without sacrificing
595 %nonassoc, default reductions, or state merging. When LAC is in
596 use, canonical LR and IELR behave almost exactly the same for both
597 syntactically acceptable and syntactically unacceptable input.
598 While LALR still does not support the full language-recognition
599 power of canonical LR and IELR, LAC at least enables LALR's syntax
600 error handling to correctly reflect LALR's language-recognition
601 power.
602
603 Currently, LAC is only supported for deterministic parsers in C.
604 You can enable LAC with the following directive:
605
606 %define parse.lac full
607
608 See the new section "LAC" in the Bison manual for additional
609 details including a few caveats.
610
611 LAC is an experimental feature. More user feedback will help to
612 stabilize it.
613
614** %define improvements:
615
616*** Can now be invoked via the command line:
617
618 Each of these command-line options
619
620 -D NAME[=VALUE]
621 --define=NAME[=VALUE]
622
623 -F NAME[=VALUE]
624 --force-define=NAME[=VALUE]
625
626 is equivalent to this grammar file declaration
627
628 %define NAME ["VALUE"]
629
630 except that the manner in which Bison processes multiple definitions
631 for the same NAME differs. Most importantly, -F and --force-define
632 quietly override %define, but -D and --define do not. For further
633 details, see the section "Bison Options" in the Bison manual.
634
635*** Variables renamed:
636
637 The following %define variables
638
639 api.push_pull
640 lr.keep_unreachable_states
641
642 have been renamed to
643
644 api.push-pull
645 lr.keep-unreachable-states
646
647 The old names are now deprecated but will be maintained indefinitely
648 for backward compatibility.
649
650*** Values no longer need to be quoted in the grammar file:
651
652 If a %define value is an identifier, it no longer needs to be placed
653 within quotations marks. For example,
654
655 %define api.push-pull "push"
656
657 can be rewritten as
658
659 %define api.push-pull push
660
661*** Unrecognized variables are now errors not warnings.
662
663*** Multiple invocations for any variable is now an error not a warning.
664
665** Unrecognized %code qualifiers are now errors not warnings.
666
667** Character literals not of length one:
668
669 Previously, Bison quietly converted all character literals to length
670 one. For example, without warning, Bison interpreted the operators in
671 the following grammar to be the same token:
672
673 exp: exp '++'
674 | exp '+' exp
675 ;
676
677 Bison now warns when a character literal is not of length one. In
678 some future release, Bison will start reporting an error instead.
679
680** Destructor calls fixed for lookaheads altered in semantic actions:
681
682 Previously for deterministic parsers in C, if a user semantic action
683 altered yychar, the parser in some cases used the old yychar value to
684 determine which destructor to call for the lookahead upon a syntax
685 error or upon parser return. This bug has been fixed.
686
687** C++ parsers use YYRHSLOC:
688
689 Similarly to the C parsers, the C++ parsers now define the YYRHSLOC
690 macro and use it in the default YYLLOC_DEFAULT. You are encouraged
691 to use it. If, for instance, your location structure has "first"
692 and "last" members, instead of
693
694 # define YYLLOC_DEFAULT(Current, Rhs, N) \
695 do \
696 if (N) \
697 { \
698 (Current).first = (Rhs)[1].location.first; \
699 (Current).last = (Rhs)[N].location.last; \
700 } \
701 else \
702 { \
703 (Current).first = (Current).last = (Rhs)[0].location.last; \
704 } \
705 while (false)
706
707 use:
708
709 # define YYLLOC_DEFAULT(Current, Rhs, N) \
710 do \
711 if (N) \
712 { \
713 (Current).first = YYRHSLOC (Rhs, 1).first; \
714 (Current).last = YYRHSLOC (Rhs, N).last; \
715 } \
716 else \
717 { \
718 (Current).first = (Current).last = YYRHSLOC (Rhs, 0).last; \
719 } \
720 while (false)
721
722** YYLLOC_DEFAULT in C++:
723
724 The default implementation of YYLLOC_DEFAULT used to be issued in
725 the header file. It is now output in the implementation file, after
726 the user %code sections so that its #ifndef guard does not try to
727 override the user's YYLLOC_DEFAULT if provided.
728
729** YYFAIL now produces warnings and Java parsers no longer implement it:
730
731 YYFAIL has existed for many years as an undocumented feature of
732 deterministic parsers in C generated by Bison. More recently, it was
733 a documented feature of Bison's experimental Java parsers. As
734 promised in Bison 2.4.2's NEWS entry, any appearance of YYFAIL in a
735 semantic action now produces a deprecation warning, and Java parsers
736 no longer implement YYFAIL at all. For further details, including a
737 discussion of how to suppress C preprocessor warnings about YYFAIL
738 being unused, see the Bison 2.4.2 NEWS entry.
739
740** Temporary hack for adding a semicolon to the user action:
741
742 Previously, Bison appended a semicolon to every user action for
743 reductions when the output language defaulted to C (specifically, when
744 neither %yacc, %language, %skeleton, or equivalent command-line
745 options were specified). This allowed actions such as
746
747 exp: exp "+" exp { $$ = $1 + $3 };
748
749 instead of
750
751 exp: exp "+" exp { $$ = $1 + $3; };
752
753 As a first step in removing this misfeature, Bison now issues a
754 warning when it appends a semicolon. Moreover, in cases where Bison
755 cannot easily determine whether a semicolon is needed (for example, an
756 action ending with a cpp directive or a braced compound initializer),
757 it no longer appends one. Thus, the C compiler might now complain
758 about a missing semicolon where it did not before. Future releases of
759 Bison will cease to append semicolons entirely.
760
761** Verbose syntax error message fixes:
762
763 When %error-verbose or the obsolete "#define YYERROR_VERBOSE" is
764 specified, syntax error messages produced by the generated parser
765 include the unexpected token as well as a list of expected tokens.
766 The effect of %nonassoc on these verbose messages has been corrected
767 in two ways, but a more complete fix requires LAC, described above:
768
769*** When %nonassoc is used, there can exist parser states that accept no
770 tokens, and so the parser does not always require a lookahead token
771 in order to detect a syntax error. Because no unexpected token or
772 expected tokens can then be reported, the verbose syntax error
773 message described above is suppressed, and the parser instead
774 reports the simpler message, "syntax error". Previously, this
775 suppression was sometimes erroneously triggered by %nonassoc when a
776 lookahead was actually required. Now verbose messages are
777 suppressed only when all previous lookaheads have already been
778 shifted or discarded.
779
780*** Previously, the list of expected tokens erroneously included tokens
781 that would actually induce a syntax error because conflicts for them
782 were resolved with %nonassoc in the current parser state. Such
783 tokens are now properly omitted from the list.
784
785*** Expected token lists are still often wrong due to state merging
786 (from LALR or IELR) and default reductions, which can both add
787 invalid tokens and subtract valid tokens. Canonical LR almost
788 completely fixes this problem by eliminating state merging and
789 default reductions. However, there is one minor problem left even
790 when using canonical LR and even after the fixes above. That is,
791 if the resolution of a conflict with %nonassoc appears in a later
792 parser state than the one at which some syntax error is
793 discovered, the conflicted token is still erroneously included in
794 the expected token list. Bison's new LAC implementation,
795 described above, eliminates this problem and the need for
796 canonical LR. However, LAC is still experimental and is disabled
797 by default.
798
799** Java skeleton fixes:
800
801*** A location handling bug has been fixed.
802
803*** The top element of each of the value stack and location stack is now
804 cleared when popped so that it can be garbage collected.
805
806*** Parser traces now print the top element of the stack.
807
808** -W/--warnings fixes:
809
810*** Bison now properly recognizes the "no-" versions of categories:
811
812 For example, given the following command line, Bison now enables all
813 warnings except warnings for incompatibilities with POSIX Yacc:
814
815 bison -Wall,no-yacc gram.y
816
817*** Bison now treats S/R and R/R conflicts like other warnings:
818
819 Previously, conflict reports were independent of Bison's normal
820 warning system. Now, Bison recognizes the warning categories
821 "conflicts-sr" and "conflicts-rr". This change has important
822 consequences for the -W and --warnings command-line options. For
823 example:
824
825 bison -Wno-conflicts-sr gram.y # S/R conflicts not reported
826 bison -Wno-conflicts-rr gram.y # R/R conflicts not reported
827 bison -Wnone gram.y # no conflicts are reported
828 bison -Werror gram.y # any conflict is an error
829
830 However, as before, if the %expect or %expect-rr directive is
831 specified, an unexpected number of conflicts is an error, and an
832 expected number of conflicts is not reported, so -W and --warning
833 then have no effect on the conflict report.
834
835*** The "none" category no longer disables a preceding "error":
836
837 For example, for the following command line, Bison now reports
838 errors instead of warnings for incompatibilities with POSIX Yacc:
839
840 bison -Werror,none,yacc gram.y
841
842*** The "none" category now disables all Bison warnings:
843
844 Previously, the "none" category disabled only Bison warnings for
845 which there existed a specific -W/--warning category. However,
846 given the following command line, Bison is now guaranteed to
847 suppress all warnings:
848
849 bison -Wnone gram.y
850
851** Precedence directives can now assign token number 0:
852
853 Since Bison 2.3b, which restored the ability of precedence
854 directives to assign token numbers, doing so for token number 0 has
855 produced an assertion failure. For example:
856
857 %left END 0
858
859 This bug has been fixed.
860
861* Changes in version 2.4.3 (2010-08-05):
862
863** Bison now obeys -Werror and --warnings=error for warnings about
864 grammar rules that are useless in the parser due to conflicts.
865
866** Problems with spawning M4 on at least FreeBSD 8 and FreeBSD 9 have
867 been fixed.
868
869** Failures in the test suite for GCC 4.5 have been fixed.
870
871** Failures in the test suite for some versions of Sun Studio C++ have
872 been fixed.
873
874** Contrary to Bison 2.4.2's NEWS entry, it has been decided that
875 warnings about undefined %prec identifiers will not be converted to
876 errors in Bison 2.5. They will remain warnings, which should be
877 sufficient for POSIX while avoiding backward compatibility issues.
878
879** Minor documentation fixes.
880
881* Changes in version 2.4.2 (2010-03-20):
882
883** Some portability problems that resulted in failures and livelocks
884 in the test suite on some versions of at least Solaris, AIX, HP-UX,
885 RHEL4, and Tru64 have been addressed. As a result, fatal Bison
886 errors should no longer cause M4 to report a broken pipe on the
887 affected platforms.
888
889** "%prec IDENTIFIER" requires IDENTIFIER to be defined separately.
890
891 POSIX specifies that an error be reported for any identifier that does
892 not appear on the LHS of a grammar rule and that is not defined by
893 %token, %left, %right, or %nonassoc. Bison 2.3b and later lost this
894 error report for the case when an identifier appears only after a
895 %prec directive. It is now restored. However, for backward
896 compatibility with recent Bison releases, it is only a warning for
897 now. In Bison 2.5 and later, it will return to being an error.
898 [Between the 2.4.2 and 2.4.3 releases, it was decided that this
899 warning will not be converted to an error in Bison 2.5.]
900
901** Detection of GNU M4 1.4.6 or newer during configure is improved.
902
903** Warnings from gcc's -Wundef option about undefined YYENABLE_NLS,
904 YYLTYPE_IS_TRIVIAL, and __STRICT_ANSI__ in C/C++ parsers are now
905 avoided.
906
907** %code is now a permanent feature.
908
909 A traditional Yacc prologue directive is written in the form:
910
911 %{CODE%}
912
913 To provide a more flexible alternative, Bison 2.3b introduced the
914 %code directive with the following forms for C/C++:
915
916 %code {CODE}
917 %code requires {CODE}
918 %code provides {CODE}
919 %code top {CODE}
920
921 These forms are now considered permanent features of Bison. See the
922 %code entries in the section "Bison Declaration Summary" in the Bison
923 manual for a summary of their functionality. See the section
924 "Prologue Alternatives" for a detailed discussion including the
925 advantages of %code over the traditional Yacc prologue directive.
926
927 Bison's Java feature as a whole including its current usage of %code
928 is still considered experimental.
929
930** YYFAIL is deprecated and will eventually be removed.
931
932 YYFAIL has existed for many years as an undocumented feature of
933 deterministic parsers in C generated by Bison. Previously, it was
934 documented for Bison's experimental Java parsers. YYFAIL is no longer
935 documented for Java parsers and is formally deprecated in both cases.
936 Users are strongly encouraged to migrate to YYERROR, which is
937 specified by POSIX.
938
939 Like YYERROR, you can invoke YYFAIL from a semantic action in order to
940 induce a syntax error. The most obvious difference from YYERROR is
941 that YYFAIL will automatically invoke yyerror to report the syntax
942 error so that you don't have to. However, there are several other
943 subtle differences between YYERROR and YYFAIL, and YYFAIL suffers from
944 inherent flaws when %error-verbose or "#define YYERROR_VERBOSE" is
945 used. For a more detailed discussion, see:
946
947 http://lists.gnu.org/archive/html/bison-patches/2009-12/msg00024.html
948
949 The upcoming Bison 2.5 will remove YYFAIL from Java parsers, but
950 deterministic parsers in C will continue to implement it. However,
951 because YYFAIL is already flawed, it seems futile to try to make new
952 Bison features compatible with it. Thus, during parser generation,
953 Bison 2.5 will produce a warning whenever it discovers YYFAIL in a
954 rule action. In a later release, YYFAIL will be disabled for
955 %error-verbose and "#define YYERROR_VERBOSE". Eventually, YYFAIL will
956 be removed altogether.
957
958 There exists at least one case where Bison 2.5's YYFAIL warning will
959 be a false positive. Some projects add phony uses of YYFAIL and other
960 Bison-defined macros for the sole purpose of suppressing C
961 preprocessor warnings (from GCC cpp's -Wunused-macros, for example).
962 To avoid Bison's future warning, such YYFAIL uses can be moved to the
963 epilogue (that is, after the second "%%") in the Bison input file. In
964 this release (2.4.2), Bison already generates its own code to suppress
965 C preprocessor warnings for YYFAIL, so projects can remove their own
966 phony uses of YYFAIL if compatibility with Bison releases prior to
967 2.4.2 is not necessary.
968
969** Internationalization.
970
971 Fix a regression introduced in Bison 2.4: Under some circumstances,
972 message translations were not installed although supported by the
973 host system.
974
975* Changes in version 2.4.1 (2008-12-11):
976
977** In the GLR defines file, unexpanded M4 macros in the yylval and yylloc
978 declarations have been fixed.
979
980** Temporary hack for adding a semicolon to the user action.
981
982 Bison used to prepend a trailing semicolon at the end of the user
983 action for reductions. This allowed actions such as
984
985 exp: exp "+" exp { $$ = $1 + $3 };
986
987 instead of
988
989 exp: exp "+" exp { $$ = $1 + $3; };
990
991 Some grammars still depend on this "feature". Bison 2.4.1 restores
992 the previous behavior in the case of C output (specifically, when
993 neither %language or %skeleton or equivalent command-line options
994 are used) to leave more time for grammars depending on the old
995 behavior to be adjusted. Future releases of Bison will disable this
996 feature.
997
998** A few minor improvements to the Bison manual.
999
1000* Changes in version 2.4 (2008-11-02):
1001
1002** %language is an experimental feature.
1003
1004 We first introduced this feature in test release 2.3b as a cleaner
1005 alternative to %skeleton. Since then, we have discussed the possibility of
1006 modifying its effect on Bison's output file names. Thus, in this release,
1007 we consider %language to be an experimental feature that will likely evolve
1008 in future releases.
1009
1010** Forward compatibility with GNU M4 has been improved.
1011
1012** Several bugs in the C++ skeleton and the experimental Java skeleton have been
1013 fixed.
1014
1015* Changes in version 2.3b (2008-05-27):
1016
1017** The quotes around NAME that used to be required in the following directive
1018 are now deprecated:
1019
1020 %define NAME "VALUE"
1021
1022** The directive "%pure-parser" is now deprecated in favor of:
1023
1024 %define api.pure
1025
1026 which has the same effect except that Bison is more careful to warn about
1027 unreasonable usage in the latter case.
1028
1029** Push Parsing
1030
1031 Bison can now generate an LALR(1) parser in C with a push interface. That
1032 is, instead of invoking "yyparse", which pulls tokens from "yylex", you can
1033 push one token at a time to the parser using "yypush_parse", which will
1034 return to the caller after processing each token. By default, the push
1035 interface is disabled. Either of the following directives will enable it:
1036
1037 %define api.push_pull "push" // Just push; does not require yylex.
1038 %define api.push_pull "both" // Push and pull; requires yylex.
1039
1040 See the new section "A Push Parser" in the Bison manual for details.
1041
1042 The current push parsing interface is experimental and may evolve. More user
1043 feedback will help to stabilize it.
1044
1045** The -g and --graph options now output graphs in Graphviz DOT format,
1046 not VCG format. Like --graph, -g now also takes an optional FILE argument
1047 and thus cannot be bundled with other short options.
1048
1049** Java
1050
1051 Bison can now generate an LALR(1) parser in Java. The skeleton is
1052 "data/lalr1.java". Consider using the new %language directive instead of
1053 %skeleton to select it.
1054
1055 See the new section "Java Parsers" in the Bison manual for details.
1056
1057 The current Java interface is experimental and may evolve. More user
1058 feedback will help to stabilize it.
1059
1060** %language
1061
1062 This new directive specifies the programming language of the generated
1063 parser, which can be C (the default), C++, or Java. Besides the skeleton
1064 that Bison uses, the directive affects the names of the generated files if
1065 the grammar file's name ends in ".y".
1066
1067** XML Automaton Report
1068
1069 Bison can now generate an XML report of the LALR(1) automaton using the new
1070 "--xml" option. The current XML schema is experimental and may evolve. More
1071 user feedback will help to stabilize it.
1072
1073** The grammar file may now specify the name of the parser header file using
1074 %defines. For example:
1075
1076 %defines "parser.h"
1077
1078** When reporting useless rules, useless nonterminals, and unused terminals,
1079 Bison now employs the terms "useless in grammar" instead of "useless",
1080 "useless in parser" instead of "never reduced", and "unused in grammar"
1081 instead of "unused".
1082
1083** Unreachable State Removal
1084
1085 Previously, Bison sometimes generated parser tables containing unreachable
1086 states. A state can become unreachable during conflict resolution if Bison
1087 disables a shift action leading to it from a predecessor state. Bison now:
1088
1089 1. Removes unreachable states.
1090
1091 2. Does not report any conflicts that appeared in unreachable states.
1092 WARNING: As a result, you may need to update %expect and %expect-rr
1093 directives in existing grammar files.
1094
1095 3. For any rule used only in such states, Bison now reports the rule as
1096 "useless in parser due to conflicts".
1097
1098 This feature can be disabled with the following directive:
1099
1100 %define lr.keep_unreachable_states
1101
1102 See the %define entry in the "Bison Declaration Summary" in the Bison manual
1103 for further discussion.
1104
1105** Lookahead Set Correction in the ".output" Report
1106
1107 When instructed to generate a ".output" file including lookahead sets
1108 (using "--report=lookahead", for example), Bison now prints each reduction's
1109 lookahead set only next to the associated state's one item that (1) is
1110 associated with the same rule as the reduction and (2) has its dot at the end
1111 of its RHS. Previously, Bison also erroneously printed the lookahead set
1112 next to all of the state's other items associated with the same rule. This
1113 bug affected only the ".output" file and not the generated parser source
1114 code.
1115
1116** --report-file=FILE is a new option to override the default ".output" file
1117 name.
1118
1119** The "=" that used to be required in the following directives is now
1120 deprecated:
1121
1122 %file-prefix "parser"
1123 %name-prefix "c_"
1124 %output "parser.c"
1125
1126** An Alternative to "%{...%}" -- "%code QUALIFIER {CODE}"
1127
1128 Bison 2.3a provided a new set of directives as a more flexible alternative to
1129 the traditional Yacc prologue blocks. Those have now been consolidated into
1130 a single %code directive with an optional qualifier field, which identifies
1131 the purpose of the code and thus the location(s) where Bison should generate
1132 it:
1133
1134 1. "%code {CODE}" replaces "%after-header {CODE}"
1135 2. "%code requires {CODE}" replaces "%start-header {CODE}"
1136 3. "%code provides {CODE}" replaces "%end-header {CODE}"
1137 4. "%code top {CODE}" replaces "%before-header {CODE}"
1138
1139 See the %code entries in section "Bison Declaration Summary" in the Bison
1140 manual for a summary of the new functionality. See the new section "Prologue
1141 Alternatives" for a detailed discussion including the advantages of %code
1142 over the traditional Yacc prologues.
1143
1144 The prologue alternatives are experimental. More user feedback will help to
1145 determine whether they should become permanent features.
1146
1147** Revised warning: unset or unused mid-rule values
1148
1149 Since Bison 2.2, Bison has warned about mid-rule values that are set but not
1150 used within any of the actions of the parent rule. For example, Bison warns
1151 about unused $2 in:
1152
1153 exp: '1' { $$ = 1; } '+' exp { $$ = $1 + $4; };
1154
1155 Now, Bison also warns about mid-rule values that are used but not set. For
1156 example, Bison warns about unset $$ in the mid-rule action in:
1157
1158 exp: '1' { $1 = 1; } '+' exp { $$ = $2 + $4; };
1159
1160 However, Bison now disables both of these warnings by default since they
1161 sometimes prove to be false alarms in existing grammars employing the Yacc
1162 constructs $0 or $-N (where N is some positive integer).
1163
1164 To enable these warnings, specify the option "--warnings=midrule-values" or
1165 "-W", which is a synonym for "--warnings=all".
1166
1167** Default %destructor or %printer with "<*>" or "<>"
1168
1169 Bison now recognizes two separate kinds of default %destructor's and
1170 %printer's:
1171
1172 1. Place "<*>" in a %destructor/%printer symbol list to define a default
1173 %destructor/%printer for all grammar symbols for which you have formally
1174 declared semantic type tags.
1175
1176 2. Place "<>" in a %destructor/%printer symbol list to define a default
1177 %destructor/%printer for all grammar symbols without declared semantic
1178 type tags.
1179
1180 Bison no longer supports the "%symbol-default" notation from Bison 2.3a.
1181 "<*>" and "<>" combined achieve the same effect with one exception: Bison no
1182 longer applies any %destructor to a mid-rule value if that mid-rule value is
1183 not actually ever referenced using either $$ or $n in a semantic action.
1184
1185 The default %destructor's and %printer's are experimental. More user
1186 feedback will help to determine whether they should become permanent
1187 features.
1188
1189 See the section "Freeing Discarded Symbols" in the Bison manual for further
1190 details.
1191
1192** %left, %right, and %nonassoc can now declare token numbers. This is required
1193 by POSIX. However, see the end of section "Operator Precedence" in the Bison
1194 manual for a caveat concerning the treatment of literal strings.
1195
1196** The nonfunctional --no-parser, -n, and %no-parser options have been
1197 completely removed from Bison.
1198
1199* Changes in version 2.3a, 2006-09-13:
1200
1201** Instead of %union, you can define and use your own union type
1202 YYSTYPE if your grammar contains at least one <type> tag.
1203 Your YYSTYPE need not be a macro; it can be a typedef.
1204 This change is for compatibility with other Yacc implementations,
1205 and is required by POSIX.
1206
1207** Locations columns and lines start at 1.
1208 In accordance with the GNU Coding Standards and Emacs.
1209
1210** You may now declare per-type and default %destructor's and %printer's:
1211
1212 For example:
1213
1214 %union { char *string; }
1215 %token <string> STRING1
1216 %token <string> STRING2
1217 %type <string> string1
1218 %type <string> string2
1219 %union { char character; }
1220 %token <character> CHR
1221 %type <character> chr
1222 %destructor { free ($$); } %symbol-default
1223 %destructor { free ($$); printf ("%d", @$.first_line); } STRING1 string1
1224 %destructor { } <character>
1225
1226 guarantees that, when the parser discards any user-defined symbol that has a
1227 semantic type tag other than "<character>", it passes its semantic value to
1228 "free". However, when the parser discards a "STRING1" or a "string1", it
1229 also prints its line number to "stdout". It performs only the second
1230 "%destructor" in this case, so it invokes "free" only once.
1231
1232 [Although we failed to mention this here in the 2.3a release, the default
1233 %destructor's and %printer's were experimental, and they were rewritten in
1234 future versions.]
1235
1236** Except for LALR(1) parsers in C with POSIX Yacc emulation enabled (with "-y",
1237 "--yacc", or "%yacc"), Bison no longer generates #define statements for
1238 associating token numbers with token names. Removing the #define statements
1239 helps to sanitize the global namespace during preprocessing, but POSIX Yacc
1240 requires them. Bison still generates an enum for token names in all cases.
1241
1242** Handling of traditional Yacc prologue blocks is now more consistent but
1243 potentially incompatible with previous releases of Bison.
1244
1245 As before, you declare prologue blocks in your grammar file with the
1246 "%{ ... %}" syntax. To generate the pre-prologue, Bison concatenates all
1247 prologue blocks that you've declared before the first %union. To generate
1248 the post-prologue, Bison concatenates all prologue blocks that you've
1249 declared after the first %union.
1250
1251 Previous releases of Bison inserted the pre-prologue into both the header
1252 file and the code file in all cases except for LALR(1) parsers in C. In the
1253 latter case, Bison inserted it only into the code file. For parsers in C++,
1254 the point of insertion was before any token definitions (which associate
1255 token numbers with names). For parsers in C, the point of insertion was
1256 after the token definitions.
1257
1258 Now, Bison never inserts the pre-prologue into the header file. In the code
1259 file, it always inserts it before the token definitions.
1260
1261** Bison now provides a more flexible alternative to the traditional Yacc
1262 prologue blocks: %before-header, %start-header, %end-header, and
1263 %after-header.
1264
1265 For example, the following declaration order in the grammar file reflects the
1266 order in which Bison will output these code blocks. However, you are free to
1267 declare these code blocks in your grammar file in whatever order is most
1268 convenient for you:
1269
1270 %before-header {
1271 /* Bison treats this block like a pre-prologue block: it inserts it into
1272 * the code file before the contents of the header file. It does *not*
1273 * insert it into the header file. This is a good place to put
1274 * #include's that you want at the top of your code file. A common
1275 * example is '#include "system.h"'. */
1276 }
1277 %start-header {
1278 /* Bison inserts this block into both the header file and the code file.
1279 * In both files, the point of insertion is before any Bison-generated
1280 * token, semantic type, location type, and class definitions. This is a
1281 * good place to define %union dependencies, for example. */
1282 }
1283 %union {
1284 /* Unlike the traditional Yacc prologue blocks, the output order for the
1285 * new %*-header blocks is not affected by their declaration position
1286 * relative to any %union in the grammar file. */
1287 }
1288 %end-header {
1289 /* Bison inserts this block into both the header file and the code file.
1290 * In both files, the point of insertion is after the Bison-generated
1291 * definitions. This is a good place to declare or define public
1292 * functions or data structures that depend on the Bison-generated
1293 * definitions. */
1294 }
1295 %after-header {
1296 /* Bison treats this block like a post-prologue block: it inserts it into
1297 * the code file after the contents of the header file. It does *not*
1298 * insert it into the header file. This is a good place to declare or
1299 * define internal functions or data structures that depend on the
1300 * Bison-generated definitions. */
1301 }
1302
1303 If you have multiple occurrences of any one of the above declarations, Bison
1304 will concatenate the contents in declaration order.
1305
1306 [Although we failed to mention this here in the 2.3a release, the prologue
1307 alternatives were experimental, and they were rewritten in future versions.]
1308
1309** The option "--report=look-ahead" has been changed to "--report=lookahead".
1310 The old spelling still works, but is not documented and may be removed
1311 in a future release.
1312
1313* Changes in version 2.3, 2006-06-05:
1314
1315** GLR grammars should now use "YYRECOVERING ()" instead of "YYRECOVERING",
1316 for compatibility with LALR(1) grammars.
1317
1318** It is now documented that any definition of YYSTYPE or YYLTYPE should
1319 be to a type name that does not contain parentheses or brackets.
1320
1321* Changes in version 2.2, 2006-05-19:
1322
1323** The distribution terms for all Bison-generated parsers now permit
1324 using the parsers in nonfree programs. Previously, this permission
1325 was granted only for Bison-generated LALR(1) parsers in C.
1326
1327** %name-prefix changes the namespace name in C++ outputs.
1328
1329** The C++ parsers export their token_type.
1330
1331** Bison now allows multiple %union declarations, and concatenates
1332 their contents together.
1333
1334** New warning: unused values
1335 Right-hand side symbols whose values are not used are reported,
1336 if the symbols have destructors. For instance:
1337
1338 exp: exp "?" exp ":" exp { $1 ? $1 : $3; }
1339 | exp "+" exp
1340 ;
1341
1342 will trigger a warning about $$ and $5 in the first rule, and $3 in
1343 the second ($1 is copied to $$ by the default rule). This example
1344 most likely contains three errors, and could be rewritten as:
1345
1346 exp: exp "?" exp ":" exp
1347 { $$ = $1 ? $3 : $5; free ($1 ? $5 : $3); free ($1); }
1348 | exp "+" exp
1349 { $$ = $1 ? $1 : $3; if ($1) free ($3); }
1350 ;
1351
1352 However, if the original actions were really intended, memory leaks
1353 and all, the warnings can be suppressed by letting Bison believe the
1354 values are used, e.g.:
1355
1356 exp: exp "?" exp ":" exp { $1 ? $1 : $3; (void) ($$, $5); }
1357 | exp "+" exp { $$ = $1; (void) $3; }
1358 ;
1359
1360 If there are mid-rule actions, the warning is issued if no action
1361 uses it. The following triggers no warning: $1 and $3 are used.
1362
1363 exp: exp { push ($1); } '+' exp { push ($3); sum (); };
1364
1365 The warning is intended to help catching lost values and memory leaks.
1366 If a value is ignored, its associated memory typically is not reclaimed.
1367
1368** %destructor vs. YYABORT, YYACCEPT, and YYERROR.
1369 Destructors are now called when user code invokes YYABORT, YYACCEPT,
1370 and YYERROR, for all objects on the stack, other than objects
1371 corresponding to the right-hand side of the current rule.
1372
1373** %expect, %expect-rr
1374 Incorrect numbers of expected conflicts are now actual errors,
1375 instead of warnings.
1376
1377** GLR, YACC parsers.
1378 The %parse-params are available in the destructors (and the
1379 experimental printers) as per the documentation.
1380
1381** Bison now warns if it finds a stray "$" or "@" in an action.
1382
1383** %require "VERSION"
1384 This specifies that the grammar file depends on features implemented
1385 in Bison version VERSION or higher.
1386
1387** lalr1.cc: The token and value types are now class members.
1388 The tokens were defined as free form enums and cpp macros. YYSTYPE
1389 was defined as a free form union. They are now class members:
1390 tokens are enumerations of the "yy::parser::token" struct, and the
1391 semantic values have the "yy::parser::semantic_type" type.
1392
1393 If you do not want or can update to this scheme, the directive
1394 '%define "global_tokens_and_yystype" "1"' triggers the global
1395 definition of tokens and YYSTYPE. This change is suitable both
1396 for previous releases of Bison, and this one.
1397
1398 If you wish to update, then make sure older version of Bison will
1399 fail using '%require "2.2"'.
1400
1401** DJGPP support added.
1402\f
1403* Changes in version 2.1, 2005-09-16:
1404
1405** The C++ lalr1.cc skeleton supports %lex-param.
1406
1407** Bison-generated parsers now support the translation of diagnostics like
1408 "syntax error" into languages other than English. The default
1409 language is still English. For details, please see the new
1410 Internationalization section of the Bison manual. Software
1411 distributors should also see the new PACKAGING file. Thanks to
1412 Bruno Haible for this new feature.
1413
1414** Wording in the Bison-generated parsers has been changed slightly to
1415 simplify translation. In particular, the message "memory exhausted"
1416 has replaced "parser stack overflow", as the old message was not
1417 always accurate for modern Bison-generated parsers.
1418
1419** Destructors are now called when the parser aborts, for all symbols left
1420 behind on the stack. Also, the start symbol is now destroyed after a
1421 successful parse. In both cases, the behavior was formerly inconsistent.
1422
1423** When generating verbose diagnostics, Bison-generated parsers no longer
1424 quote the literal strings associated with tokens. For example, for
1425 a syntax error associated with '%token NUM "number"' they might
1426 print 'syntax error, unexpected number' instead of 'syntax error,
1427 unexpected "number"'.
1428\f
1429* Changes in version 2.0, 2004-12-25:
1430
1431** Possibly-incompatible changes
1432
1433 - Bison-generated parsers no longer default to using the alloca function
1434 (when available) to extend the parser stack, due to widespread
1435 problems in unchecked stack-overflow detection. You can "#define
1436 YYSTACK_USE_ALLOCA 1" to require the use of alloca, but please read
1437 the manual to determine safe values for YYMAXDEPTH in that case.
1438
1439 - Error token location.
1440 During error recovery, the location of the syntax error is updated
1441 to cover the whole sequence covered by the error token: it includes
1442 the shifted symbols thrown away during the first part of the error
1443 recovery, and the lookahead rejected during the second part.
1444
1445 - Semicolon changes:
1446 . Stray semicolons are no longer allowed at the start of a grammar.
1447 . Semicolons are now required after in-grammar declarations.
1448
1449 - Unescaped newlines are no longer allowed in character constants or
1450 string literals. They were never portable, and GCC 3.4.0 has
1451 dropped support for them. Better diagnostics are now generated if
1452 forget a closing quote.
1453
1454 - NUL bytes are no longer allowed in Bison string literals, unfortunately.
1455
1456** New features
1457
1458 - GLR grammars now support locations.
1459
1460 - New directive: %initial-action.
1461 This directive allows the user to run arbitrary code (including
1462 initializing @$) from yyparse before parsing starts.
1463
1464 - A new directive "%expect-rr N" specifies the expected number of
1465 reduce/reduce conflicts in GLR parsers.
1466
1467 - %token numbers can now be hexadecimal integers, e.g., "%token FOO 0x12d".
1468 This is a GNU extension.
1469
1470 - The option "--report=lookahead" was changed to "--report=look-ahead".
1471 [However, this was changed back after 2.3.]
1472
1473 - Experimental %destructor support has been added to lalr1.cc.
1474
1475 - New configure option --disable-yacc, to disable installation of the
1476 yacc command and -ly library introduced in 1.875 for POSIX conformance.
1477
1478** Bug fixes
1479
1480 - For now, %expect-count violations are now just warnings, not errors.
1481 This is for compatibility with Bison 1.75 and earlier (when there are
1482 reduce/reduce conflicts) and with Bison 1.30 and earlier (when there
1483 are too many or too few shift/reduce conflicts). However, in future
1484 versions of Bison we plan to improve the %expect machinery so that
1485 these violations will become errors again.
1486
1487 - Within Bison itself, numbers (e.g., goto numbers) are no longer
1488 arbitrarily limited to 16-bit counts.
1489
1490 - Semicolons are now allowed before "|" in grammar rules, as POSIX requires.
1491\f
1492* Changes in version 1.875, 2003-01-01:
1493
1494** The documentation license has been upgraded to version 1.2
1495 of the GNU Free Documentation License.
1496
1497** syntax error processing
1498
1499 - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error
1500 locations too. This fixes bugs in error-location computation.
1501
1502 - %destructor
1503 It is now possible to reclaim the memory associated to symbols
1504 discarded during error recovery. This feature is still experimental.
1505
1506 - %error-verbose
1507 This new directive is preferred over YYERROR_VERBOSE.
1508
1509 - #defining yyerror to steal internal variables is discouraged.
1510 It is not guaranteed to work forever.
1511
1512** POSIX conformance
1513
1514 - Semicolons are once again optional at the end of grammar rules.
1515 This reverts to the behavior of Bison 1.33 and earlier, and improves
1516 compatibility with Yacc.
1517
1518 - "parse error" -> "syntax error"
1519 Bison now uniformly uses the term "syntax error"; formerly, the code
1520 and manual sometimes used the term "parse error" instead. POSIX
1521 requires "syntax error" in diagnostics, and it was thought better to
1522 be consistent.
1523
1524 - The documentation now emphasizes that yylex and yyerror must be
1525 declared before use. C99 requires this.
1526
1527 - Bison now parses C99 lexical constructs like UCNs and
1528 backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires.
1529
1530 - File names are properly escaped in C output. E.g., foo\bar.y is
1531 output as "foo\\bar.y".
1532
1533 - Yacc command and library now available
1534 The Bison distribution now installs a "yacc" command, as POSIX requires.
1535 Also, Bison now installs a small library liby.a containing
1536 implementations of Yacc-compatible yyerror and main functions.
1537 This library is normally not useful, but POSIX requires it.
1538
1539 - Type clashes now generate warnings, not errors.
1540
1541 - If the user does not define YYSTYPE as a macro, Bison now declares it
1542 using typedef instead of defining it as a macro.
1543 For consistency, YYLTYPE is also declared instead of defined.
1544
1545** Other compatibility issues
1546
1547 - %union directives can now have a tag before the "{", e.g., the
1548 directive "%union foo {...}" now generates the C code
1549 "typedef union foo { ... } YYSTYPE;"; this is for Yacc compatibility.
1550 The default union tag is "YYSTYPE", for compatibility with Solaris 9 Yacc.
1551 For consistency, YYLTYPE's struct tag is now "YYLTYPE" not "yyltype".
1552 This is for compatibility with both Yacc and Bison 1.35.
1553
1554 - ";" is output before the terminating "}" of an action, for
1555 compatibility with Bison 1.35.
1556
1557 - Bison now uses a Yacc-style format for conflict reports, e.g.,
1558 "conflicts: 2 shift/reduce, 1 reduce/reduce".
1559
1560 - "yystype" and "yyltype" are now obsolescent macros instead of being
1561 typedefs or tags; they are no longer documented and are planned to be
1562 withdrawn in a future release.
1563
1564** GLR parser notes
1565
1566 - GLR and inline
1567 Users of Bison have to decide how they handle the portability of the
1568 C keyword "inline".
1569
1570 - "parsing stack overflow..." -> "parser stack overflow"
1571 GLR parsers now report "parser stack overflow" as per the Bison manual.
1572
1573** %parse-param and %lex-param
1574 The macros YYPARSE_PARAM and YYLEX_PARAM provide a means to pass
1575 additional context to yyparse and yylex. They suffer from several
1576 shortcomings:
1577
1578 - a single argument only can be added,
1579 - their types are weak (void *),
1580 - this context is not passed to ancillary functions such as yyerror,
1581 - only yacc.c parsers support them.
1582
1583 The new %parse-param/%lex-param directives provide a more precise control.
1584 For instance:
1585
1586 %parse-param {int *nastiness}
1587 %lex-param {int *nastiness}
1588 %parse-param {int *randomness}
1589
1590 results in the following signatures:
1591
1592 int yylex (int *nastiness);
1593 int yyparse (int *nastiness, int *randomness);
1594
1595 or, if both %pure-parser and %locations are used:
1596
1597 int yylex (YYSTYPE *lvalp, YYLTYPE *llocp, int *nastiness);
1598 int yyparse (int *nastiness, int *randomness);
1599
1600** Bison now warns if it detects conflicting outputs to the same file,
1601 e.g., it generates a warning for "bison -d -o foo.h foo.y" since
1602 that command outputs both code and header to foo.h.
1603
1604** #line in output files
1605 - --no-line works properly.
1606
1607** Bison can no longer be built by a K&R C compiler; it requires C89 or
1608 later to be built. This change originally took place a few versions
1609 ago, but nobody noticed until we recently asked someone to try
1610 building Bison with a K&R C compiler.
1611\f
1612* Changes in version 1.75, 2002-10-14:
1613
1614** Bison should now work on 64-bit hosts.
1615
1616** Indonesian translation thanks to Tedi Heriyanto.
1617
1618** GLR parsers
1619 Fix spurious parse errors.
1620
1621** Pure parsers
1622 Some people redefine yyerror to steal yyparse' private variables.
1623 Reenable this trick until an official feature replaces it.
1624
1625** Type Clashes
1626 In agreement with POSIX and with other Yaccs, leaving a default
1627 action is valid when $$ is untyped, and $1 typed:
1628
1629 untyped: ... typed;
1630
1631 but the converse remains an error:
1632
1633 typed: ... untyped;
1634
1635** Values of mid-rule actions
1636 The following code:
1637
1638 foo: { ... } { $$ = $1; } ...
1639
1640 was incorrectly rejected: $1 is defined in the second mid-rule
1641 action, and is equal to the $$ of the first mid-rule action.
1642\f
1643* Changes in version 1.50, 2002-10-04:
1644
1645** GLR parsing
1646 The declaration
1647 %glr-parser
1648 causes Bison to produce a Generalized LR (GLR) parser, capable of handling
1649 almost any context-free grammar, ambiguous or not. The new declarations
1650 %dprec and %merge on grammar rules allow parse-time resolution of
1651 ambiguities. Contributed by Paul Hilfinger.
1652
1653 Unfortunately Bison 1.50 does not work properly on 64-bit hosts
1654 like the Alpha, so please stick to 32-bit hosts for now.
1655
1656** Output Directory
1657 When not in Yacc compatibility mode, when the output file was not
1658 specified, running "bison foo/bar.y" created "foo/bar.c". It
1659 now creates "bar.c".
1660
1661** Undefined token
1662 The undefined token was systematically mapped to 2 which prevented
1663 the use of 2 by the user. This is no longer the case.
1664
1665** Unknown token numbers
1666 If yylex returned an out of range value, yyparse could die. This is
1667 no longer the case.
1668
1669** Error token
1670 According to POSIX, the error token must be 256.
1671 Bison extends this requirement by making it a preference: *if* the
1672 user specified that one of her tokens is numbered 256, then error
1673 will be mapped onto another number.
1674
1675** Verbose error messages
1676 They no longer report "..., expecting error or..." for states where
1677 error recovery is possible.
1678
1679** End token
1680 Defaults to "$end" instead of "$".
1681
1682** Error recovery now conforms to documentation and to POSIX
1683 When a Bison-generated parser encounters a syntax error, it now pops
1684 the stack until it finds a state that allows shifting the error
1685 token. Formerly, it popped the stack until it found a state that
1686 allowed some non-error action other than a default reduction on the
1687 error token. The new behavior has long been the documented behavior,
1688 and has long been required by POSIX. For more details, please see
1689 Paul Eggert, "Reductions during Bison error handling" (2002-05-20)
1690 <http://lists.gnu.org/archive/html/bug-bison/2002-05/msg00038.html>.
1691
1692** Traces
1693 Popped tokens and nonterminals are now reported.
1694
1695** Larger grammars
1696 Larger grammars are now supported (larger token numbers, larger grammar
1697 size (= sum of the LHS and RHS lengths), larger LALR tables).
1698 Formerly, many of these numbers ran afoul of 16-bit limits;
1699 now these limits are 32 bits on most hosts.
1700
1701** Explicit initial rule
1702 Bison used to play hacks with the initial rule, which the user does
1703 not write. It is now explicit, and visible in the reports and
1704 graphs as rule 0.
1705
1706** Useless rules
1707 Before, Bison reported the useless rules, but, although not used,
1708 included them in the parsers. They are now actually removed.
1709
1710** Useless rules, useless nonterminals
1711 They are now reported, as a warning, with their locations.
1712
1713** Rules never reduced
1714 Rules that can never be reduced because of conflicts are now
1715 reported.
1716
1717** Incorrect "Token not used"
1718 On a grammar such as
1719
1720 %token useless useful
1721 %%
1722 exp: '0' %prec useful;
1723
1724 where a token was used to set the precedence of the last rule,
1725 bison reported both "useful" and "useless" as useless tokens.
1726
1727** Revert the C++ namespace changes introduced in 1.31
1728 as they caused too many portability hassles.
1729
1730** Default locations
1731 By an accident of design, the default computation of @$ was
1732 performed after another default computation was performed: @$ = @1.
1733 The latter is now removed: YYLLOC_DEFAULT is fully responsible of
1734 the computation of @$.
1735
1736** Token end-of-file
1737 The token end of file may be specified by the user, in which case,
1738 the user symbol is used in the reports, the graphs, and the verbose
1739 error messages instead of "$end", which remains being the default.
1740 For instance
1741 %token MYEOF 0
1742 or
1743 %token MYEOF 0 "end of file"
1744
1745** Semantic parser
1746 This old option, which has been broken for ages, is removed.
1747
1748** New translations
1749 Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
1750 Croatian, thanks to Denis Lackovic.
1751
1752** Incorrect token definitions
1753 When given
1754 %token 'a' "A"
1755 bison used to output
1756 #define 'a' 65
1757
1758** Token definitions as enums
1759 Tokens are output both as the traditional #define's, and, provided
1760 the compiler supports ANSI C or is a C++ compiler, as enums.
1761 This lets debuggers display names instead of integers.
1762
1763** Reports
1764 In addition to --verbose, bison supports --report=THINGS, which
1765 produces additional information:
1766 - itemset
1767 complete the core item sets with their closure
1768 - lookahead [changed to "look-ahead" in 1.875e through 2.3, but changed back]
1769 explicitly associate lookahead tokens to items
1770 - solved
1771 describe shift/reduce conflicts solving.
1772 Bison used to systematically output this information on top of
1773 the report. Solved conflicts are now attached to their states.
1774
1775** Type clashes
1776 Previous versions don't complain when there is a type clash on
1777 the default action if the rule has a mid-rule action, such as in:
1778
1779 %type <foo> bar
1780 %%
1781 bar: '0' {} '0';
1782
1783 This is fixed.
1784
1785** GNU M4 is now required when using Bison.
1786\f
1787* Changes in version 1.35, 2002-03-25:
1788
1789** C Skeleton
1790 Some projects use Bison's C parser with C++ compilers, and define
1791 YYSTYPE as a class. The recent adjustment of C parsers for data
1792 alignment and 64 bit architectures made this impossible.
1793
1794 Because for the time being no real solution for C++ parser
1795 generation exists, kludges were implemented in the parser to
1796 maintain this use. In the future, when Bison has C++ parsers, this
1797 kludge will be disabled.
1798
1799 This kludge also addresses some C++ problems when the stack was
1800 extended.
1801\f
1802* Changes in version 1.34, 2002-03-12:
1803
1804** File name clashes are detected
1805 $ bison foo.y -d -o foo.x
1806 fatal error: header and parser would both be named "foo.x"
1807
1808** A missing ";" at the end of a rule triggers a warning
1809 In accordance with POSIX, and in agreement with other
1810 Yacc implementations, Bison will mandate this semicolon in the near
1811 future. This eases the implementation of a Bison parser of Bison
1812 grammars by making this grammar LALR(1) instead of LR(2). To
1813 facilitate the transition, this release introduces a warning.
1814
1815** Revert the C++ namespace changes introduced in 1.31, as they caused too
1816 many portability hassles.
1817
1818** DJGPP support added.
1819
1820** Fix test suite portability problems.
1821\f
1822* Changes in version 1.33, 2002-02-07:
1823
1824** Fix C++ issues
1825 Groff could not be compiled for the definition of size_t was lacking
1826 under some conditions.
1827
1828** Catch invalid @n
1829 As is done with $n.
1830\f
1831* Changes in version 1.32, 2002-01-23:
1832
1833** Fix Yacc output file names
1834
1835** Portability fixes
1836
1837** Italian, Dutch translations
1838\f
1839* Changes in version 1.31, 2002-01-14:
1840
1841** Many Bug Fixes
1842
1843** GNU Gettext and %expect
1844 GNU Gettext asserts 10 s/r conflicts, but there are 7. Now that
1845 Bison dies on incorrect %expectations, we fear there will be
1846 too many bug reports for Gettext, so _for the time being_, %expect
1847 does not trigger an error when the input file is named "plural.y".
1848
1849** Use of alloca in parsers
1850 If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use
1851 malloc exclusively. Since 1.29, but was not NEWS'ed.
1852
1853 alloca is used only when compiled with GCC, to avoid portability
1854 problems as on AIX.
1855
1856** yyparse now returns 2 if memory is exhausted; formerly it dumped core.
1857
1858** When the generated parser lacks debugging code, YYDEBUG is now 0
1859 (as POSIX requires) instead of being undefined.
1860
1861** User Actions
1862 Bison has always permitted actions such as { $$ = $1 }: it adds the
1863 ending semicolon. Now if in Yacc compatibility mode, the semicolon
1864 is no longer output: one has to write { $$ = $1; }.
1865
1866** Better C++ compliance
1867 The output parsers try to respect C++ namespaces.
1868 [This turned out to be a failed experiment, and it was reverted later.]
1869
1870** Reduced Grammars
1871 Fixed bugs when reporting useless nonterminals.
1872
1873** 64 bit hosts
1874 The parsers work properly on 64 bit hosts.
1875
1876** Error messages
1877 Some calls to strerror resulted in scrambled or missing error messages.
1878
1879** %expect
1880 When the number of shift/reduce conflicts is correct, don't issue
1881 any warning.
1882
1883** The verbose report includes the rule line numbers.
1884
1885** Rule line numbers are fixed in traces.
1886
1887** Swedish translation
1888
1889** Parse errors
1890 Verbose parse error messages from the parsers are better looking.
1891 Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'(''
1892 Now: parse error: unexpected '/', expecting "number" or '-' or '('
1893
1894** Fixed parser memory leaks.
1895 When the generated parser was using malloc to extend its stacks, the
1896 previous allocations were not freed.
1897
1898** Fixed verbose output file.
1899 Some newlines were missing.
1900 Some conflicts in state descriptions were missing.
1901
1902** Fixed conflict report.
1903 Option -v was needed to get the result.
1904
1905** %expect
1906 Was not used.
1907 Mismatches are errors, not warnings.
1908
1909** Fixed incorrect processing of some invalid input.
1910
1911** Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H.
1912
1913** Fixed some typos in the documentation.
1914
1915** %token MY_EOF 0 is supported.
1916 Before, MY_EOF was silently renumbered as 257.
1917
1918** doc/refcard.tex is updated.
1919
1920** %output, %file-prefix, %name-prefix.
1921 New.
1922
1923** --output
1924 New, aliasing "--output-file".
1925\f
1926* Changes in version 1.30, 2001-10-26:
1927
1928** "--defines" and "--graph" have now an optional argument which is the
1929 output file name. "-d" and "-g" do not change; they do not take any
1930 argument.
1931
1932** "%source_extension" and "%header_extension" are removed, failed
1933 experiment.
1934
1935** Portability fixes.
1936\f
1937* Changes in version 1.29, 2001-09-07:
1938
1939** The output file does not define const, as this caused problems when used
1940 with common autoconfiguration schemes. If you still use ancient compilers
1941 that lack const, compile with the equivalent of the C compiler option
1942 "-Dconst=". Autoconf's AC_C_CONST macro provides one way to do this.
1943
1944** Added "-g" and "--graph".
1945
1946** The Bison manual is now distributed under the terms of the GNU FDL.
1947
1948** The input and the output files has automatically a similar extension.
1949
1950** Russian translation added.
1951
1952** NLS support updated; should hopefully be less troublesome.
1953
1954** Added the old Bison reference card.
1955
1956** Added "--locations" and "%locations".
1957
1958** Added "-S" and "--skeleton".
1959
1960** "%raw", "-r", "--raw" is disabled.
1961
1962** Special characters are escaped when output. This solves the problems
1963 of the #line lines with path names including backslashes.
1964
1965** New directives.
1966 "%yacc", "%fixed_output_files", "%defines", "%no_parser", "%verbose",
1967 "%debug", "%source_extension" and "%header_extension".
1968
1969** @$
1970 Automatic location tracking.
1971\f
1972* Changes in version 1.28, 1999-07-06:
1973
1974** Should compile better now with K&R compilers.
1975
1976** Added NLS.
1977
1978** Fixed a problem with escaping the double quote character.
1979
1980** There is now a FAQ.
1981\f
1982* Changes in version 1.27:
1983
1984** The make rule which prevented bison.simple from being created on
1985 some systems has been fixed.
1986\f
1987* Changes in version 1.26:
1988
1989** Bison now uses Automake.
1990
1991** New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
1992
1993** Token numbers now start at 257 as previously documented, not 258.
1994
1995** Bison honors the TMPDIR environment variable.
1996
1997** A couple of buffer overruns have been fixed.
1998
1999** Problems when closing files should now be reported.
2000
2001** Generated parsers should now work even on operating systems which do
2002 not provide alloca().
2003\f
2004* Changes in version 1.25, 1995-10-16:
2005
2006** Errors in the input grammar are not fatal; Bison keeps reading
2007the grammar file, and reports all the errors found in it.
2008
2009** Tokens can now be specified as multiple-character strings: for
2010example, you could use "<=" for a token which looks like <=, instead
2011of choosing a name like LESSEQ.
2012
2013** The %token_table declaration says to write a table of tokens (names
2014and numbers) into the parser file. The yylex function can use this
2015table to recognize multiple-character string tokens, or for other
2016purposes.
2017
2018** The %no_lines declaration says not to generate any #line preprocessor
2019directives in the parser file.
2020
2021** The %raw declaration says to use internal Bison token numbers, not
2022Yacc-compatible token numbers, when token names are defined as macros.
2023
2024** The --no-parser option produces the parser tables without including
2025the parser engine; a project can now use its own parser engine.
2026The actions go into a separate file called NAME.act, in the form of
2027a switch statement body.
2028\f
2029* Changes in version 1.23:
2030
2031The user can define YYPARSE_PARAM as the name of an argument to be
2032passed into yyparse. The argument should have type void *. It should
2033actually point to an object. Grammar actions can access the variable
2034by casting it to the proper pointer type.
2035
2036Line numbers in output file corrected.
2037\f
2038* Changes in version 1.22:
2039
2040--help option added.
2041\f
2042* Changes in version 1.20:
2043
2044Output file does not redefine const for C++.
2045
2046-----
2047
2048Copyright (C) 1995-2012 Free Software Foundation, Inc.
2049
2050This file is part of Bison, the GNU Parser Generator.
2051
2052This program is free software: you can redistribute it and/or modify
2053it under the terms of the GNU General Public License as published by
2054the Free Software Foundation, either version 3 of the License, or
2055(at your option) any later version.
2056
2057This program is distributed in the hope that it will be useful,
2058but WITHOUT ANY WARRANTY; without even the implied warranty of
2059MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
2060GNU General Public License for more details.
2061
2062You should have received a copy of the GNU General Public License
2063along with this program. If not, see <http://www.gnu.org/licenses/>.
2064
2065 LocalWords: yacc YYBACKUP glr GCC lalr ArrayIndexOutOfBoundsException nullptr
2066 LocalWords: cplusplus liby rpl fprintf mfcalc Wyacc stmt cond expr mk sym lr
2067 LocalWords: IELR ielr Lookahead YYERROR nonassoc LALR's api lookaheads yychar
2068 LocalWords: destructor lookahead YYRHSLOC YYLLOC Rhs ifndef YYFAIL cpp sr rr
2069 LocalWords: preprocessor initializer Wno Wnone Werror FreeBSD prec livelocks
2070 LocalWords: Solaris AIX UX RHEL Tru LHS gcc's Wundef YYENABLE NLS YYLTYPE VCG
2071 LocalWords: yyerror cpp's Wunused yylval yylloc prepend yyparse yylex yypush
2072 LocalWords: Graphviz xml nonterminals midrule destructor's YYSTYPE typedef ly
2073 LocalWords: CHR chr printf stdout namespace preprocessing enum pre include's
2074 LocalWords: YYRECOVERING nonfree destructors YYABORT YYACCEPT params enums de
2075 LocalWords: struct yystype DJGPP lex param Haible NUM alloca YYSTACK NUL goto
2076 LocalWords: YYMAXDEPTH Unescaped UCNs YYLTYPE's yyltype typedefs inline Yaccs
2077 LocalWords: Heriyanto Reenable dprec Hilfinger Eggert MYEOF Folle Menezes EOF
2078 LocalWords: Lackovic define's itemset Groff Gettext malloc NEWS'ed YYDEBUG YY
2079 LocalWords: namespaces strerror const autoconfiguration Dconst Autoconf's FDL
2080 LocalWords: Automake TMPDIR LESSEQ ylwrap endif yydebug YYTOKEN YYLSP ival hh
2081 LocalWords: extern YYTOKENTYPE TOKENTYPE yytokentype tokentype STYPE lval pdf
2082 LocalWords: lang yyoutput dvi html ps POSIX lvalp llocp Wother nterm arg init
2083 LocalWords: TOK
2084
2085Local Variables:
2086mode: outline
2087fill-column: 76
2088End: