build: don't require src/bison during bootstrap.
[bison.git] / NEWS
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4* Changes in version ?.? (????-??-??):
5
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6** Additional yylex/yyparse arguments
7
8 The new directive %param declare additional argument to both yylex
9 and yyparse. The %lex-param, %parse-param, and %param directive
10 support one or more arguments. Instead of
11
12 %lex-param {arg1_type *arg1}
13 %lex-param {arg2_type *arg2}
14 %parse-param {arg1_type *arg1}
15 %parse-param {arg2_type *arg2}
16
17 one may now declare
18
19 %param {arg1_type *arg1} {arg2_type *arg2}
20
21** Java skeleton improvements
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22
23 The constants for token names were moved to the Lexer interface.
24 Also, it is possible to add code to the parser's constructors using
25 "%code init" and "%define init_throws".
26
4c6622c2 27** Variable api.tokens.prefix
99c08fb6 28
4c6622c2 29 The variable api.tokens.prefix changes the way tokens are identified in
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30 the generated files. This is especially useful to avoid collisions
31 with identifiers in the target language. For instance
32
33 %token FILE for ERROR
4c6622c2 34 %define api.tokens.prefix "TOK_"
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35 %%
36 start: FILE for ERROR;
37
38 will generate the definition of the symbols TOK_FILE, TOK_for, and
39 TOK_ERROR in the generated sources. In particular, the scanner must
40 use these prefixed token names, although the grammar itself still
41 uses the short names (as in the sample rule given above).
42
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43** Variable api.namespace
44
45 The "namespace" variable is renamed "api.namespace". Backward
46 compatibility is ensured, but upgrading is recommended.
47
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48** Variable parse.error
49
50 The variable error controls the verbosity of error messages. The
51 use of the %error-verbose directive is deprecated in favor of
52 %define parse.error "verbose".
53
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54* Changes in version 2.5 (????-??-??):
55
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56** Named References Support
57
58 Historically, Yacc and Bison have supported positional references
59 ($n, $$) to allow access to symbol values from inside of semantic
60 actions code.
61
62 Starting from this version, Bison can also accept named references.
63 When no ambiguity is possible, original symbol names may be used
64 as named references:
65
66 if_stmt : 'if' cond_expr 'then' then_stmt ';'
67 { $if_stmt = mk_if_stmt($cond_expr, $then_stmt); }
68
69 In the more common case, explicit names may be declared:
70
71 stmt[res] : 'if' expr[cond] 'then' stmt[then] 'else' stmt[else] ';'
72 { $res = mk_if_stmt($cond, $then, $else); }
73
5b1ff423 74 Location information is also accessible using @name syntax. When
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75 accessing symbol names containing dots or dashes, explicit bracketing
76 ($[sym.1]) must be used.
77
5b1ff423 78 These features are experimental in this version. More user feedback
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79 will help to stabilize them.
80
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81** IELR(1) and Canonical LR(1) Support
82
83 IELR(1) is a minimal LR(1) parser table generation algorithm. That
84 is, given any context-free grammar, IELR(1) generates parser tables
85 with the full language recognition power of canonical LR(1) but with
86 nearly the same number of parser states as LALR(1). This reduction in
87 parser states is often an order of magnitude. More importantly,
88 because canonical LR(1)'s extra parser states may contain duplicate
89 conflicts in the case of non-LR(1) grammars, the number of conflicts
90 for IELR(1) is often an order of magnitude less as well. This can
91 significantly reduce the complexity of developing of a grammar.
92
93 Bison can now generate IELR(1) and canonical LR(1) parser tables in
94 place of its traditional LALR(1) parser tables, which remain the
95 default. You can specify the type of parser tables in the grammar
96 file with these directives:
97
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98 %define lr.type lalr
99 %define lr.type ielr
100 %define lr.type canonical-lr
eb45ef3b 101
110ef36a 102 The default reduction optimization in the parser tables can also be
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103 adjusted using `%define lr.default-reductions'. See the documentation
104 for `%define lr.type' and `%define lr.default-reductions' in the
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105 section `Bison Declaration Summary' in the Bison manual for the
106 details.
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107
108 These features are experimental. More user feedback will help to
109 stabilize them.
110
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111** Unrecognized %code qualifiers are now an error not a warning.
112
cf499cff 113** %define improvements.
0b6d43c5 114
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115*** Unrecognized variables are now an error not a warning.
116
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117*** Multiple invocations for any variable is now an error not a warning.
118
119*** Can now be invoked via the command line.
50cca368 120
de5ab940 121 Each of these command-line options
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123 -D NAME[=VALUE]
124 --define=NAME[=VALUE]
125
126 -F NAME[=VALUE]
127 --force-define=NAME[=VALUE]
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128
129 is equivalent to this grammar file declaration
130
de5ab940 131 %define NAME ["VALUE"]
50cca368 132
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133 except that the manner in which Bison processes multiple definitions
134 for the same NAME differs. Most importantly, -F and --force-define
135 quietly override %define, but -D and --define do not. For further
136 details, see the section "Bison Options" in the Bison manual.
50cca368 137
cf499cff 138*** Variables renamed.
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139
140 The following %define variables
141
142 api.push_pull
143 lr.keep_unreachable_states
144
145 have been renamed to
146
147 api.push-pull
148 lr.keep-unreachable-states
149
150 The old names are now deprecated but will be maintained indefinitely
151 for backward compatibility.
152
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153*** Values no longer need to be quoted in grammar file.
154
155 If a %define value is an identifier, it no longer needs to be placed
156 within quotations marks. For example,
157
158 %define api.push-pull "push"
159
160 can be rewritten as
161
162 %define api.push-pull push
163
164** Symbol names.
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165
166 Consistently with directives (such as %error-verbose) and variables
167 (e.g. push-pull), symbol names may include dashes in any position,
168 similarly to periods and underscores. This is GNU extension over
169 POSIX Yacc whose use is reported by -Wyacc, and rejected in Yacc
170 mode (--yacc).
171
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172** YYFAIL now produces warnings and Java parsers no longer implement it.
173
174 YYFAIL has existed for many years as an undocumented feature of
175 deterministic parsers in C generated by Bison. More recently, it was
176 a documented feature of Bison's experimental Java parsers. As
177 promised in Bison 2.4.2's NEWS entry, any appearance of YYFAIL in a
178 semantic action now produces a deprecation warning, and Java parsers
179 no longer implement YYFAIL at all. For further details, including a
180 discussion of how to suppress C preprocessor warnings about YYFAIL
181 being unused, see the Bison 2.4.2 NEWS entry.
182
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183** `%prec IDENTIFIER' requires IDENTIFIER to be defined separately.
184
185 As promised in Bison 2.4.2's NEWS entry, it is now an error if a token
186 that appears after a %prec directive is not defined by %token, %left,
187 %right, or %nonassoc. This is required by POSIX.
188
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189** Temporary hack for adding a semicolon to the user action.
190
191 Previously, Bison appended a semicolon to every user action for
192 reductions when the output language defaulted to C (specifically, when
193 neither %yacc, %language, %skeleton, or equivalent command-line
194 options were specified). This allowed actions such as
195
196 exp: exp "+" exp { $$ = $1 + $3 };
197
198 instead of
199
200 exp: exp "+" exp { $$ = $1 + $3; };
201
202 As a first step in removing this misfeature, Bison now issues a
203 warning when it appends a semicolon. Moreover, in cases where Bison
204 cannot easily determine whether a semicolon is needed (for example, an
205 action ending with a cpp directive or a braced compound initializer),
206 it no longer appends one. Thus, the C compiler might now complain
207 about a missing semicolon where it did not before. Future releases of
208 Bison will cease to append semicolons entirely.
209
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210** Character literals not of length one.
211
212 Previously, Bison quietly converted all character literals to length
213 one. For example, without warning, Bison interpreted the operators in
214 the following grammar to be the same token:
215
216 exp: exp '++'
217 | exp '+' exp
218 ;
219
220 Bison now warns when a character literal is not of length one. In
221 some future release, Bison will report an error instead.
222
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223** Verbose error messages fixed for nonassociative tokens.
224
225 When %error-verbose is specified, syntax error messages produced by
226 the generated parser include the unexpected token as well as a list of
227 expected tokens. Previously, this list erroneously included tokens
228 that would actually induce a syntax error because conflicts for them
229 were resolved with %nonassoc. Such tokens are now properly omitted
230 from the list.
231
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232** Destructor calls fixed for lookaheads altered in semantic actions.
233
234 Previously for deterministic parsers in C, if a user semantic action
235 altered yychar, the parser in some cases used the old yychar value to
236 determine which destructor to call for the lookahead upon a syntax
237 error or upon parser return. This bug has been fixed.
238
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239* Changes in version 2.4.3 (????-??-??):
240
241** Problems with spawning M4 on at least FreeBSD 8 and FreeBSD 9 have
242 been fixed.
243
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244** Failures in the test suite for GCC 4.5 have been fixed.
245
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246** Failures in the test suite for some versions of Sun Studio C++ have
247 been fixed.
248
e19a049c 249* Changes in version 2.4.2 (2010-03-20):
74553c98 250
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251** Some portability problems that resulted in failures and livelocks
252 in the test suite on some versions of at least Solaris, AIX, HP-UX,
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253 RHEL4, and Tru64 have been addressed. As a result, fatal Bison
254 errors should no longer cause M4 to report a broken pipe on the
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255 affected platforms.
256
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257** `%prec IDENTIFIER' requires IDENTIFIER to be defined separately.
258
259 POSIX specifies that an error be reported for any identifier that does
260 not appear on the LHS of a grammar rule and that is not defined by
261 %token, %left, %right, or %nonassoc. Bison 2.3b and later lost this
262 error report for the case when an identifier appears only after a
263 %prec directive. It is now restored. However, for backward
264 compatibility with recent Bison releases, it is only a warning for
265 now. In Bison 2.5 and later, it will return to being an error.
266
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267** Detection of GNU M4 1.4.6 or newer during configure is improved.
268
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269** Warnings from gcc's -Wundef option about undefined YYENABLE_NLS,
270 YYLTYPE_IS_TRIVIAL, and __STRICT_ANSI__ in C/C++ parsers are now
271 avoided.
c938d650 272
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273** %code is now a permanent feature.
274
275 A traditional Yacc prologue directive is written in the form:
276
277 %{CODE%}
278
279 To provide a more flexible alternative, Bison 2.3b introduced the
280 %code directive with the following forms for C/C++:
281
282 %code {CODE}
283 %code requires {CODE}
284 %code provides {CODE}
285 %code top {CODE}
286
287 These forms are now considered permanent features of Bison. See the
288 %code entries in the section "Bison Declaration Summary" in the Bison
289 manual for a summary of their functionality. See the section
290 "Prologue Alternatives" for a detailed discussion including the
291 advantages of %code over the traditional Yacc prologue directive.
292
293 Bison's Java feature as a whole including its current usage of %code
294 is still considered experimental.
295
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296** YYFAIL is deprecated and will eventually be removed.
297
298 YYFAIL has existed for many years as an undocumented feature of
299 deterministic parsers in C generated by Bison. Previously, it was
300 documented for Bison's experimental Java parsers. YYFAIL is no longer
301 documented for Java parsers and is formally deprecated in both cases.
302 Users are strongly encouraged to migrate to YYERROR, which is
303 specified by POSIX.
304
305 Like YYERROR, you can invoke YYFAIL from a semantic action in order to
306 induce a syntax error. The most obvious difference from YYERROR is
307 that YYFAIL will automatically invoke yyerror to report the syntax
308 error so that you don't have to. However, there are several other
309 subtle differences between YYERROR and YYFAIL, and YYFAIL suffers from
310 inherent flaws when %error-verbose or `#define YYERROR_VERBOSE' is
311 used. For a more detailed discussion, see:
312
313 http://lists.gnu.org/archive/html/bison-patches/2009-12/msg00024.html
314
315 The upcoming Bison 2.5 will remove YYFAIL from Java parsers, but
316 deterministic parsers in C will continue to implement it. However,
317 because YYFAIL is already flawed, it seems futile to try to make new
318 Bison features compatible with it. Thus, during parser generation,
319 Bison 2.5 will produce a warning whenever it discovers YYFAIL in a
320 rule action. In a later release, YYFAIL will be disabled for
321 %error-verbose and `#define YYERROR_VERBOSE'. Eventually, YYFAIL will
322 be removed altogether.
323
324 There exists at least one case where Bison 2.5's YYFAIL warning will
325 be a false positive. Some projects add phony uses of YYFAIL and other
326 Bison-defined macros for the sole purpose of suppressing C
327 preprocessor warnings (from GCC cpp's -Wunused-macros, for example).
328 To avoid Bison's future warning, such YYFAIL uses can be moved to the
329 epilogue (that is, after the second `%%') in the Bison input file. In
330 this release (2.4.2), Bison already generates its own code to suppress
331 C preprocessor warnings for YYFAIL, so projects can remove their own
332 phony uses of YYFAIL if compatibility with Bison releases prior to
333 2.4.2 is not necessary.
334
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335** Internationalization.
336
337 Fix a regression introduced in Bison 2.4: Under some circumstances,
338 message translations were not installed although supported by the
339 host system.
340
74553c98 341* Changes in version 2.4.1 (2008-12-11):
c9ba9e59 342
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343** In the GLR defines file, unexpanded M4 macros in the yylval and yylloc
344 declarations have been fixed.
1979121c 345
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346** Temporary hack for adding a semicolon to the user action.
347
348 Bison used to prepend a trailing semicolon at the end of the user
349 action for reductions. This allowed actions such as
350
351 exp: exp "+" exp { $$ = $1 + $3 };
352
353 instead of
354
355 exp: exp "+" exp { $$ = $1 + $3; };
356
357 Some grammars still depend on this `feature'. Bison 2.4.1 restores
358 the previous behavior in the case of C output (specifically, when
359 neither %language or %skeleton or equivalent command-line options
360 are used) to leave more time for grammars depending on the old
361 behavior to be adjusted. Future releases of Bison will disable this
362 feature.
363
364** A few minor improvements to the Bison manual.
c9ba9e59 365
402b123d 366* Changes in version 2.4 (2008-11-02):
7bd1665a 367
402b123d 368** %language is an experimental feature.
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369
370 We first introduced this feature in test release 2.3b as a cleaner
371 alternative to %skeleton. Since then, we have discussed the possibility of
372 modifying its effect on Bison's output file names. Thus, in this release,
373 we consider %language to be an experimental feature that will likely evolve
374 in future releases.
7bd1665a 375
402b123d 376** Forward compatibility with GNU M4 has been improved.
241fda7a 377
402b123d 378** Several bugs in the C++ skeleton and the experimental Java skeleton have been
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379 fixed.
380
402b123d 381* Changes in version 2.3b (2008-05-27):
35fe0834 382
402b123d 383** The quotes around NAME that used to be required in the following directive
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384 are now deprecated:
385
386 %define NAME "VALUE"
387
402b123d 388** The directive `%pure-parser' is now deprecated in favor of:
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389
390 %define api.pure
391
392 which has the same effect except that Bison is more careful to warn about
393 unreasonable usage in the latter case.
394
402b123d 395** Push Parsing
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396
397 Bison can now generate an LALR(1) parser in C with a push interface. That
ef1b4273 398 is, instead of invoking `yyparse', which pulls tokens from `yylex', you can
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399 push one token at a time to the parser using `yypush_parse', which will
400 return to the caller after processing each token. By default, the push
401 interface is disabled. Either of the following directives will enable it:
402
403 %define api.push_pull "push" // Just push; does not require yylex.
404 %define api.push_pull "both" // Push and pull; requires yylex.
405
406 See the new section `A Push Parser' in the Bison manual for details.
407
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408 The current push parsing interface is experimental and may evolve. More user
409 feedback will help to stabilize it.
410
402b123d 411** The -g and --graph options now output graphs in Graphviz DOT format,
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412 not VCG format. Like --graph, -g now also takes an optional FILE argument
413 and thus cannot be bundled with other short options.
c373bf8b 414
402b123d 415** Java
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416
417 Bison can now generate an LALR(1) parser in Java. The skeleton is
418 `data/lalr1.java'. Consider using the new %language directive instead of
419 %skeleton to select it.
420
421 See the new section `Java Parsers' in the Bison manual for details.
422
423 The current Java interface is experimental and may evolve. More user
424 feedback will help to stabilize it.
425
402b123d 426** %language
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427
428 This new directive specifies the programming language of the generated
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429 parser, which can be C (the default), C++, or Java. Besides the skeleton
430 that Bison uses, the directive affects the names of the generated files if
431 the grammar file's name ends in ".y".
59da312b 432
402b123d 433** XML Automaton Report
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434
435 Bison can now generate an XML report of the LALR(1) automaton using the new
436 `--xml' option. The current XML schema is experimental and may evolve. More
437 user feedback will help to stabilize it.
c373bf8b 438
402b123d 439** The grammar file may now specify the name of the parser header file using
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440 %defines. For example:
441
442 %defines "parser.h"
443
402b123d 444** When reporting useless rules, useless nonterminals, and unused terminals,
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445 Bison now employs the terms "useless in grammar" instead of "useless",
446 "useless in parser" instead of "never reduced", and "unused in grammar"
447 instead of "unused".
cff03fb2 448
402b123d 449** Unreachable State Removal
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450
451 Previously, Bison sometimes generated parser tables containing unreachable
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452 states. A state can become unreachable during conflict resolution if Bison
453 disables a shift action leading to it from a predecessor state. Bison now:
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454
455 1. Removes unreachable states.
456
457 2. Does not report any conflicts that appeared in unreachable states.
458 WARNING: As a result, you may need to update %expect and %expect-rr
459 directives in existing grammar files.
460
461 3. For any rule used only in such states, Bison now reports the rule as
cff03fb2 462 "useless in parser due to conflicts".
75ad86ee 463
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464 This feature can be disabled with the following directive:
465
466 %define lr.keep_unreachable_states
467
468 See the %define entry in the `Bison Declaration Summary' in the Bison manual
469 for further discussion.
470
402b123d 471** Lookahead Set Correction in the `.output' Report
b1cc23c4 472
c373bf8b 473 When instructed to generate a `.output' file including lookahead sets
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474 (using `--report=lookahead', for example), Bison now prints each reduction's
475 lookahead set only next to the associated state's one item that (1) is
476 associated with the same rule as the reduction and (2) has its dot at the end
477 of its RHS. Previously, Bison also erroneously printed the lookahead set
478 next to all of the state's other items associated with the same rule. This
479 bug affected only the `.output' file and not the generated parser source
480 code.
481
402b123d 482** --report-file=FILE is a new option to override the default `.output' file
59da312b 483 name.
1bb2bd75 484
402b123d 485** The `=' that used to be required in the following directives is now
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486 deprecated:
487
488 %file-prefix "parser"
489 %name-prefix "c_"
490 %output "parser.c"
491
402b123d 492** An Alternative to `%{...%}' -- `%code QUALIFIER {CODE}'
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493
494 Bison 2.3a provided a new set of directives as a more flexible alternative to
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495 the traditional Yacc prologue blocks. Those have now been consolidated into
496 a single %code directive with an optional qualifier field, which identifies
497 the purpose of the code and thus the location(s) where Bison should generate
498 it:
499
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500 1. `%code {CODE}' replaces `%after-header {CODE}'
501 2. `%code requires {CODE}' replaces `%start-header {CODE}'
502 3. `%code provides {CODE}' replaces `%end-header {CODE}'
503 4. `%code top {CODE}' replaces `%before-header {CODE}'
8e0a5e9e 504
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505 See the %code entries in section `Bison Declaration Summary' in the Bison
506 manual for a summary of the new functionality. See the new section `Prologue
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507 Alternatives' for a detailed discussion including the advantages of %code
508 over the traditional Yacc prologues.
509
510 The prologue alternatives are experimental. More user feedback will help to
511 determine whether they should become permanent features.
512
402b123d 513** Revised warning: unset or unused mid-rule values
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514
515 Since Bison 2.2, Bison has warned about mid-rule values that are set but not
516 used within any of the actions of the parent rule. For example, Bison warns
517 about unused $2 in:
518
519 exp: '1' { $$ = 1; } '+' exp { $$ = $1 + $4; };
520
521 Now, Bison also warns about mid-rule values that are used but not set. For
522 example, Bison warns about unset $$ in the mid-rule action in:
523
524 exp: '1' { $1 = 1; } '+' exp { $$ = $2 + $4; };
525
526 However, Bison now disables both of these warnings by default since they
527 sometimes prove to be false alarms in existing grammars employing the Yacc
528 constructs $0 or $-N (where N is some positive integer).
529
59da312b 530 To enable these warnings, specify the option `--warnings=midrule-values' or
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531 `-W', which is a synonym for `--warnings=all'.
532
402b123d 533** Default %destructor or %printer with `<*>' or `<>'
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534
535 Bison now recognizes two separate kinds of default %destructor's and
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536 %printer's:
537
538 1. Place `<*>' in a %destructor/%printer symbol list to define a default
539 %destructor/%printer for all grammar symbols for which you have formally
540 declared semantic type tags.
541
3ebecc24 542 2. Place `<>' in a %destructor/%printer symbol list to define a default
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543 %destructor/%printer for all grammar symbols without declared semantic
544 type tags.
545
546 Bison no longer supports the `%symbol-default' notation from Bison 2.3a.
3ebecc24 547 `<*>' and `<>' combined achieve the same effect with one exception: Bison no
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548 longer applies any %destructor to a mid-rule value if that mid-rule value is
549 not actually ever referenced using either $$ or $n in a semantic action.
550
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551 The default %destructor's and %printer's are experimental. More user
552 feedback will help to determine whether they should become permanent
553 features.
554
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555 See the section `Freeing Discarded Symbols' in the Bison manual for further
556 details.
557
402b123d 558** %left, %right, and %nonassoc can now declare token numbers. This is required
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559 by POSIX. However, see the end of section `Operator Precedence' in the Bison
560 manual for a caveat concerning the treatment of literal strings.
561
402b123d 562** The nonfunctional --no-parser, -n, and %no-parser options have been
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563 completely removed from Bison.
564
402b123d 565* Changes in version 2.3a, 2006-09-13:
742e4900 566
402b123d 567** Instead of %union, you can define and use your own union type
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568 YYSTYPE if your grammar contains at least one <type> tag.
569 Your YYSTYPE need not be a macro; it can be a typedef.
570 This change is for compatibility with other Yacc implementations,
571 and is required by POSIX.
572
402b123d 573** Locations columns and lines start at 1.
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574 In accordance with the GNU Coding Standards and Emacs.
575
402b123d 576** You may now declare per-type and default %destructor's and %printer's:
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577
578 For example:
579
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580 %union { char *string; }
581 %token <string> STRING1
582 %token <string> STRING2
583 %type <string> string1
584 %type <string> string2
585 %union { char character; }
586 %token <character> CHR
587 %type <character> chr
588 %destructor { free ($$); } %symbol-default
589 %destructor { free ($$); printf ("%d", @$.first_line); } STRING1 string1
590 %destructor { } <character>
591
592 guarantees that, when the parser discards any user-defined symbol that has a
593 semantic type tag other than `<character>', it passes its semantic value to
594 `free'. However, when the parser discards a `STRING1' or a `string1', it
595 also prints its line number to `stdout'. It performs only the second
596 `%destructor' in this case, so it invokes `free' only once.
ec5479ce 597
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598 [Although we failed to mention this here in the 2.3a release, the default
599 %destructor's and %printer's were experimental, and they were rewritten in
600 future versions.]
601
402b123d 602** Except for LALR(1) parsers in C with POSIX Yacc emulation enabled (with `-y',
b931235e
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603 `--yacc', or `%yacc'), Bison no longer generates #define statements for
604 associating token numbers with token names. Removing the #define statements
605 helps to sanitize the global namespace during preprocessing, but POSIX Yacc
606 requires them. Bison still generates an enum for token names in all cases.
607
402b123d 608** Handling of traditional Yacc prologue blocks is now more consistent but
34f98f46 609 potentially incompatible with previous releases of Bison.
9bc0dd67
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610
611 As before, you declare prologue blocks in your grammar file with the
612 `%{ ... %}' syntax. To generate the pre-prologue, Bison concatenates all
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613 prologue blocks that you've declared before the first %union. To generate
614 the post-prologue, Bison concatenates all prologue blocks that you've
ddc8ede1 615 declared after the first %union.
9bc0dd67 616
34f98f46 617 Previous releases of Bison inserted the pre-prologue into both the header
9bc0dd67
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618 file and the code file in all cases except for LALR(1) parsers in C. In the
619 latter case, Bison inserted it only into the code file. For parsers in C++,
620 the point of insertion was before any token definitions (which associate
621 token numbers with names). For parsers in C, the point of insertion was
622 after the token definitions.
623
624 Now, Bison never inserts the pre-prologue into the header file. In the code
625 file, it always inserts it before the token definitions.
626
402b123d 627** Bison now provides a more flexible alternative to the traditional Yacc
34f98f46
JD
628 prologue blocks: %before-header, %start-header, %end-header, and
629 %after-header.
630
631 For example, the following declaration order in the grammar file reflects the
632 order in which Bison will output these code blocks. However, you are free to
633 declare these code blocks in your grammar file in whatever order is most
634 convenient for you:
635
636 %before-header {
637 /* Bison treats this block like a pre-prologue block: it inserts it into
638 * the code file before the contents of the header file. It does *not*
639 * insert it into the header file. This is a good place to put
640 * #include's that you want at the top of your code file. A common
641 * example is `#include "system.h"'. */
642 }
643 %start-header {
644 /* Bison inserts this block into both the header file and the code file.
645 * In both files, the point of insertion is before any Bison-generated
646 * token, semantic type, location type, and class definitions. This is a
647 * good place to define %union dependencies, for example. */
9bc0dd67
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648 }
649 %union {
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650 /* Unlike the traditional Yacc prologue blocks, the output order for the
651 * new %*-header blocks is not affected by their declaration position
652 * relative to any %union in the grammar file. */
9bc0dd67 653 }
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654 %end-header {
655 /* Bison inserts this block into both the header file and the code file.
656 * In both files, the point of insertion is after the Bison-generated
657 * definitions. This is a good place to declare or define public
658 * functions or data structures that depend on the Bison-generated
659 * definitions. */
9bc0dd67 660 }
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661 %after-header {
662 /* Bison treats this block like a post-prologue block: it inserts it into
663 * the code file after the contents of the header file. It does *not*
664 * insert it into the header file. This is a good place to declare or
665 * define internal functions or data structures that depend on the
666 * Bison-generated definitions. */
667 }
668
669 If you have multiple occurrences of any one of the above declarations, Bison
670 will concatenate the contents in declaration order.
9bc0dd67 671
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672 [Although we failed to mention this here in the 2.3a release, the prologue
673 alternatives were experimental, and they were rewritten in future versions.]
674
402b123d 675** The option `--report=look-ahead' has been changed to `--report=lookahead'.
9e6e7ed2
PE
676 The old spelling still works, but is not documented and may be removed
677 in a future release.
742e4900 678
402b123d 679* Changes in version 2.3, 2006-06-05:
4ad3ed84 680
402b123d 681** GLR grammars should now use `YYRECOVERING ()' instead of `YYRECOVERING',
4ad3ed84
PE
682 for compatibility with LALR(1) grammars.
683
402b123d 684** It is now documented that any definition of YYSTYPE or YYLTYPE should
4ad3ed84
PE
685 be to a type name that does not contain parentheses or brackets.
686
402b123d 687* Changes in version 2.2, 2006-05-19:
193d7c70 688
402b123d 689** The distribution terms for all Bison-generated parsers now permit
193d7c70
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690 using the parsers in nonfree programs. Previously, this permission
691 was granted only for Bison-generated LALR(1) parsers in C.
5f4236a0 692
402b123d 693** %name-prefix changes the namespace name in C++ outputs.
aa08666d 694
402b123d 695** The C++ parsers export their token_type.
5f4236a0 696
402b123d 697** Bison now allows multiple %union declarations, and concatenates
d6ca7905
PE
698 their contents together.
699
402b123d 700** New warning: unused values
4d7bc38c
PE
701 Right-hand side symbols whose values are not used are reported,
702 if the symbols have destructors. For instance:
affac613 703
8f3596a6 704 exp: exp "?" exp ":" exp { $1 ? $1 : $3; }
721be13c
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705 | exp "+" exp
706 ;
affac613 707
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708 will trigger a warning about $$ and $5 in the first rule, and $3 in
709 the second ($1 is copied to $$ by the default rule). This example
4e26c69e 710 most likely contains three errors, and could be rewritten as:
affac613 711
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PE
712 exp: exp "?" exp ":" exp
713 { $$ = $1 ? $3 : $5; free ($1 ? $5 : $3); free ($1); }
714 | exp "+" exp
715 { $$ = $1 ? $1 : $3; if ($1) free ($3); }
721be13c 716 ;
affac613 717
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PE
718 However, if the original actions were really intended, memory leaks
719 and all, the warnings can be suppressed by letting Bison believe the
720 values are used, e.g.:
721be13c 721
8f3596a6 722 exp: exp "?" exp ":" exp { $1 ? $1 : $3; (void) ($$, $5); }
721be13c
PE
723 | exp "+" exp { $$ = $1; (void) $3; }
724 ;
725
84866159
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726 If there are mid-rule actions, the warning is issued if no action
727 uses it. The following triggers no warning: $1 and $3 are used.
728
729 exp: exp { push ($1); } '+' exp { push ($3); sum (); };
730
721be13c
PE
731 The warning is intended to help catching lost values and memory leaks.
732 If a value is ignored, its associated memory typically is not reclaimed.
affac613 733
402b123d 734** %destructor vs. YYABORT, YYACCEPT, and YYERROR.
9d9b8b70
PE
735 Destructors are now called when user code invokes YYABORT, YYACCEPT,
736 and YYERROR, for all objects on the stack, other than objects
737 corresponding to the right-hand side of the current rule.
a85284cf 738
402b123d 739** %expect, %expect-rr
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PE
740 Incorrect numbers of expected conflicts are now actual errors,
741 instead of warnings.
742
402b123d 743** GLR, YACC parsers.
4e26c69e
PE
744 The %parse-params are available in the destructors (and the
745 experimental printers) as per the documentation.
4b367315 746
402b123d 747** Bison now warns if it finds a stray `$' or `@' in an action.
ad6a9b97 748
402b123d 749** %require "VERSION"
4e26c69e
PE
750 This specifies that the grammar file depends on features implemented
751 in Bison version VERSION or higher.
b50d2359 752
402b123d 753** lalr1.cc: The token and value types are now class members.
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754 The tokens were defined as free form enums and cpp macros. YYSTYPE
755 was defined as a free form union. They are now class members:
fb9712a9
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756 tokens are enumerations of the `yy::parser::token' struct, and the
757 semantic values have the `yy::parser::semantic_type' type.
758
759 If you do not want or can update to this scheme, the directive
760 `%define "global_tokens_and_yystype" "1"' triggers the global
b50d2359
AD
761 definition of tokens and YYSTYPE. This change is suitable both
762 for previous releases of Bison, and this one.
fb9712a9 763
b50d2359 764 If you wish to update, then make sure older version of Bison will
ab8d9dc5 765 fail using `%require "2.2"'.
fb9712a9 766
402b123d 767** DJGPP support added.
193d7c70 768\f
402b123d 769* Changes in version 2.1, 2005-09-16:
1ce59070 770
402b123d 771** The C++ lalr1.cc skeleton supports %lex-param.
e14d0ab6 772
402b123d 773** Bison-generated parsers now support the translation of diagnostics like
baf785db
PE
774 "syntax error" into languages other than English. The default
775 language is still English. For details, please see the new
0410a6e0
PE
776 Internationalization section of the Bison manual. Software
777 distributors should also see the new PACKAGING file. Thanks to
778 Bruno Haible for this new feature.
1ce59070 779
402b123d 780** Wording in the Bison-generated parsers has been changed slightly to
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PE
781 simplify translation. In particular, the message "memory exhausted"
782 has replaced "parser stack overflow", as the old message was not
783 always accurate for modern Bison-generated parsers.
784
402b123d 785** Destructors are now called when the parser aborts, for all symbols left
258b75ca
PE
786 behind on the stack. Also, the start symbol is now destroyed after a
787 successful parse. In both cases, the behavior was formerly inconsistent.
788
402b123d 789** When generating verbose diagnostics, Bison-generated parsers no longer
72f000b0
PE
790 quote the literal strings associated with tokens. For example, for
791 a syntax error associated with '%token NUM "number"' they might
792 print 'syntax error, unexpected number' instead of 'syntax error,
793 unexpected "number"'.
193d7c70 794\f
402b123d 795* Changes in version 2.0, 2004-12-25:
efeed023 796
402b123d 797** Possibly-incompatible changes
d7e14fc0 798
82de6b0d
PE
799 - Bison-generated parsers no longer default to using the alloca function
800 (when available) to extend the parser stack, due to widespread
801 problems in unchecked stack-overflow detection. You can "#define
802 YYSTACK_USE_ALLOCA 1" to require the use of alloca, but please read
803 the manual to determine safe values for YYMAXDEPTH in that case.
8dd162d3 804
82de6b0d
PE
805 - Error token location.
806 During error recovery, the location of the syntax error is updated
807 to cover the whole sequence covered by the error token: it includes
808 the shifted symbols thrown away during the first part of the error
809 recovery, and the lookahead rejected during the second part.
18d192f0 810
82de6b0d
PE
811 - Semicolon changes:
812 . Stray semicolons are no longer allowed at the start of a grammar.
813 . Semicolons are now required after in-grammar declarations.
e342c3be 814
82de6b0d
PE
815 - Unescaped newlines are no longer allowed in character constants or
816 string literals. They were never portable, and GCC 3.4.0 has
817 dropped support for them. Better diagnostics are now generated if
818 forget a closing quote.
8dd162d3 819
82de6b0d 820 - NUL bytes are no longer allowed in Bison string literals, unfortunately.
f74b6f91 821
402b123d 822** New features
1452af69 823
82de6b0d 824 - GLR grammars now support locations.
4febdd96 825
82de6b0d
PE
826 - New directive: %initial-action.
827 This directive allows the user to run arbitrary code (including
828 initializing @$) from yyparse before parsing starts.
1452af69 829
82de6b0d
PE
830 - A new directive "%expect-rr N" specifies the expected number of
831 reduce/reduce conflicts in GLR parsers.
1452af69 832
82de6b0d
PE
833 - %token numbers can now be hexadecimal integers, e.g., `%token FOO 0x12d'.
834 This is a GNU extension.
4febdd96 835
82de6b0d 836 - The option `--report=lookahead' was changed to `--report=look-ahead'.
9e6e7ed2 837 [However, this was changed back after 2.3.]
1452af69 838
82de6b0d 839 - Experimental %destructor support has been added to lalr1.cc.
1452af69 840
82de6b0d
PE
841 - New configure option --disable-yacc, to disable installation of the
842 yacc command and -ly library introduced in 1.875 for POSIX conformance.
6040d338 843
402b123d 844** Bug fixes
d5a3fe37 845
82de6b0d
PE
846 - For now, %expect-count violations are now just warnings, not errors.
847 This is for compatibility with Bison 1.75 and earlier (when there are
848 reduce/reduce conflicts) and with Bison 1.30 and earlier (when there
849 are too many or too few shift/reduce conflicts). However, in future
850 versions of Bison we plan to improve the %expect machinery so that
851 these violations will become errors again.
3473d0f8 852
82de6b0d
PE
853 - Within Bison itself, numbers (e.g., goto numbers) are no longer
854 arbitrarily limited to 16-bit counts.
d600ee67 855
82de6b0d 856 - Semicolons are now allowed before "|" in grammar rules, as POSIX requires.
d600ee67 857\f
402b123d 858* Changes in version 1.875, 2003-01-01:
963fcc17 859
402b123d 860** The documentation license has been upgraded to version 1.2
dc546b0f 861 of the GNU Free Documentation License.
75eb3bc4 862
402b123d 863** syntax error processing
75eb3bc4 864
dc546b0f
PE
865 - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error
866 locations too. This fixes bugs in error-location computation.
75eb3bc4 867
dc546b0f
PE
868 - %destructor
869 It is now possible to reclaim the memory associated to symbols
870 discarded during error recovery. This feature is still experimental.
20daca06 871
dc546b0f
PE
872 - %error-verbose
873 This new directive is preferred over YYERROR_VERBOSE.
74724a70 874
dc546b0f
PE
875 - #defining yyerror to steal internal variables is discouraged.
876 It is not guaranteed to work forever.
d1de5372 877
402b123d 878** POSIX conformance
d1de5372 879
dc546b0f
PE
880 - Semicolons are once again optional at the end of grammar rules.
881 This reverts to the behavior of Bison 1.33 and earlier, and improves
882 compatibility with Yacc.
74724a70 883
dc546b0f
PE
884 - `parse error' -> `syntax error'
885 Bison now uniformly uses the term `syntax error'; formerly, the code
886 and manual sometimes used the term `parse error' instead. POSIX
887 requires `syntax error' in diagnostics, and it was thought better to
888 be consistent.
74724a70 889
dc546b0f
PE
890 - The documentation now emphasizes that yylex and yyerror must be
891 declared before use. C99 requires this.
d1de5372 892
dc546b0f
PE
893 - Bison now parses C99 lexical constructs like UCNs and
894 backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires.
d1de5372 895
dc546b0f
PE
896 - File names are properly escaped in C output. E.g., foo\bar.y is
897 output as "foo\\bar.y".
6780ca7a 898
dc546b0f
PE
899 - Yacc command and library now available
900 The Bison distribution now installs a `yacc' command, as POSIX requires.
901 Also, Bison now installs a small library liby.a containing
902 implementations of Yacc-compatible yyerror and main functions.
903 This library is normally not useful, but POSIX requires it.
6e649e65 904
dc546b0f 905 - Type clashes now generate warnings, not errors.
6e649e65 906
dc546b0f
PE
907 - If the user does not define YYSTYPE as a macro, Bison now declares it
908 using typedef instead of defining it as a macro.
909 For consistency, YYLTYPE is also declared instead of defined.
9501dc6e 910
402b123d 911** Other compatibility issues
886a425c 912
dc546b0f
PE
913 - %union directives can now have a tag before the `{', e.g., the
914 directive `%union foo {...}' now generates the C code
915 `typedef union foo { ... } YYSTYPE;'; this is for Yacc compatibility.
916 The default union tag is `YYSTYPE', for compatibility with Solaris 9 Yacc.
917 For consistency, YYLTYPE's struct tag is now `YYLTYPE' not `yyltype'.
918 This is for compatibility with both Yacc and Bison 1.35.
72f889cc 919
dc546b0f
PE
920 - `;' is output before the terminating `}' of an action, for
921 compatibility with Bison 1.35.
886a425c 922
dc546b0f
PE
923 - Bison now uses a Yacc-style format for conflict reports, e.g.,
924 `conflicts: 2 shift/reduce, 1 reduce/reduce'.
437c2d80 925
dc546b0f
PE
926 - `yystype' and `yyltype' are now obsolescent macros instead of being
927 typedefs or tags; they are no longer documented and are planned to be
928 withdrawn in a future release.
2a8d363a 929
402b123d 930** GLR parser notes
2a8d363a 931
dc546b0f
PE
932 - GLR and inline
933 Users of Bison have to decide how they handle the portability of the
934 C keyword `inline'.
959e5f51 935
dc546b0f
PE
936 - `parsing stack overflow...' -> `parser stack overflow'
937 GLR parsers now report `parser stack overflow' as per the Bison manual.
900c5db5 938
402b123d 939** Bison now warns if it detects conflicting outputs to the same file,
dc546b0f
PE
940 e.g., it generates a warning for `bison -d -o foo.h foo.y' since
941 that command outputs both code and header to foo.h.
6e40b4eb 942
402b123d 943** #line in output files
dc546b0f 944 - --no-line works properly.
6e40b4eb 945
402b123d 946** Bison can no longer be built by a K&R C compiler; it requires C89 or
6e40b4eb
AD
947 later to be built. This change originally took place a few versions
948 ago, but nobody noticed until we recently asked someone to try
949 building Bison with a K&R C compiler.
d600ee67 950\f
402b123d 951* Changes in version 1.75, 2002-10-14:
7933f2b5 952
402b123d 953** Bison should now work on 64-bit hosts.
7933f2b5 954
402b123d 955** Indonesian translation thanks to Tedi Heriyanto.
7933f2b5 956
402b123d 957** GLR parsers
f50adbbd
AD
958 Fix spurious parse errors.
959
402b123d 960** Pure parsers
f50adbbd
AD
961 Some people redefine yyerror to steal yyparse' private variables.
962 Reenable this trick until an official feature replaces it.
963
402b123d 964** Type Clashes
d90c934c
AD
965 In agreement with POSIX and with other Yaccs, leaving a default
966 action is valid when $$ is untyped, and $1 typed:
967
968 untyped: ... typed;
969
970 but the converse remains an error:
971
972 typed: ... untyped;
973
402b123d 974** Values of mid-rule actions
d90c934c
AD
975 The following code:
976
977 foo: { ... } { $$ = $1; } ...
978
979 was incorrectly rejected: $1 is defined in the second mid-rule
980 action, and is equal to the $$ of the first mid-rule action.
d600ee67 981\f
402b123d 982* Changes in version 1.50, 2002-10-04:
adc8c848 983
402b123d 984** GLR parsing
676385e2
PH
985 The declaration
986 %glr-parser
987 causes Bison to produce a Generalized LR (GLR) parser, capable of handling
988 almost any context-free grammar, ambiguous or not. The new declarations
e8832397 989 %dprec and %merge on grammar rules allow parse-time resolution of
676385e2
PH
990 ambiguities. Contributed by Paul Hilfinger.
991
7933f2b5 992 Unfortunately Bison 1.50 does not work properly on 64-bit hosts
420f93c8
PE
993 like the Alpha, so please stick to 32-bit hosts for now.
994
402b123d 995** Output Directory
8c165d89 996 When not in Yacc compatibility mode, when the output file was not
e88dbdbf 997 specified, running `bison foo/bar.y' created `foo/bar.c'. It
8c165d89
AD
998 now creates `bar.c'.
999
402b123d 1000** Undefined token
007a50a4 1001 The undefined token was systematically mapped to 2 which prevented
e88dbdbf 1002 the use of 2 by the user. This is no longer the case.
007a50a4 1003
402b123d 1004** Unknown token numbers
e88dbdbf 1005 If yylex returned an out of range value, yyparse could die. This is
007a50a4
AD
1006 no longer the case.
1007
402b123d 1008** Error token
e88dbdbf 1009 According to POSIX, the error token must be 256.
23c5a174
AD
1010 Bison extends this requirement by making it a preference: *if* the
1011 user specified that one of her tokens is numbered 256, then error
1012 will be mapped onto another number.
1013
402b123d 1014** Verbose error messages
e88dbdbf 1015 They no longer report `..., expecting error or...' for states where
217598da
AD
1016 error recovery is possible.
1017
402b123d 1018** End token
217598da
AD
1019 Defaults to `$end' instead of `$'.
1020
402b123d 1021** Error recovery now conforms to documentation and to POSIX
68cd8af3
PE
1022 When a Bison-generated parser encounters a syntax error, it now pops
1023 the stack until it finds a state that allows shifting the error
1024 token. Formerly, it popped the stack until it found a state that
1025 allowed some non-error action other than a default reduction on the
1026 error token. The new behavior has long been the documented behavior,
1027 and has long been required by POSIX. For more details, please see
337116ba
PE
1028 Paul Eggert, "Reductions during Bison error handling" (2002-05-20)
1029 <http://lists.gnu.org/archive/html/bug-bison/2002-05/msg00038.html>.
68cd8af3 1030
402b123d 1031** Traces
5504898e
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1032 Popped tokens and nonterminals are now reported.
1033
402b123d 1034** Larger grammars
a861a339
PE
1035 Larger grammars are now supported (larger token numbers, larger grammar
1036 size (= sum of the LHS and RHS lengths), larger LALR tables).
1037 Formerly, many of these numbers ran afoul of 16-bit limits;
1038 now these limits are 32 bits on most hosts.
355e7c1c 1039
402b123d 1040** Explicit initial rule
643a5994
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1041 Bison used to play hacks with the initial rule, which the user does
1042 not write. It is now explicit, and visible in the reports and
1043 graphs as rule 0.
23c5a174 1044
402b123d 1045** Useless rules
643a5994 1046 Before, Bison reported the useless rules, but, although not used,
77714df2 1047 included them in the parsers. They are now actually removed.
23c5a174 1048
402b123d 1049** Useless rules, useless nonterminals
6b98e4b5
AD
1050 They are now reported, as a warning, with their locations.
1051
402b123d 1052** Rules never reduced
e8832397
AD
1053 Rules that can never be reduced because of conflicts are now
1054 reported.
1055
402b123d 1056** Incorrect `Token not used'
11652ab3
AD
1057 On a grammar such as
1058
1059 %token useless useful
1060 %%
1061 exp: '0' %prec useful;
1062
1063 where a token was used to set the precedence of the last rule,
1064 bison reported both `useful' and `useless' as useless tokens.
1065
402b123d 1066** Revert the C++ namespace changes introduced in 1.31
77714df2 1067 as they caused too many portability hassles.
0179dd65 1068
402b123d 1069** Default locations
b2d52318
AD
1070 By an accident of design, the default computation of @$ was
1071 performed after another default computation was performed: @$ = @1.
1072 The latter is now removed: YYLLOC_DEFAULT is fully responsible of
1073 the computation of @$.
adc8c848 1074
402b123d 1075** Token end-of-file
b7c49edf
AD
1076 The token end of file may be specified by the user, in which case,
1077 the user symbol is used in the reports, the graphs, and the verbose
a861a339 1078 error messages instead of `$end', which remains being the default.
b7c49edf 1079 For instance
7bd6c77e 1080 %token MYEOF 0
b7c49edf 1081 or
7bd6c77e 1082 %token MYEOF 0 "end of file"
fdbcd8e2 1083
402b123d 1084** Semantic parser
fdbcd8e2
AD
1085 This old option, which has been broken for ages, is removed.
1086
402b123d 1087** New translations
a861a339 1088 Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
84614e13
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1089 Croatian, thanks to Denis Lackovic.
1090
402b123d 1091** Incorrect token definitions
e88dbdbf 1092 When given `%token 'a' "A"', Bison used to output `#define 'a' 65'.
b87f8b21 1093
402b123d 1094** Token definitions as enums
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1095 Tokens are output both as the traditional #define's, and, provided
1096 the compiler supports ANSI C or is a C++ compiler, as enums.
e88dbdbf 1097 This lets debuggers display names instead of integers.
77714df2 1098
402b123d 1099** Reports
ec3bc396
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1100 In addition to --verbose, bison supports --report=THINGS, which
1101 produces additional information:
b408954b
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1102 - itemset
1103 complete the core item sets with their closure
9e6e7ed2
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1104 - lookahead [changed to `look-ahead' in 1.875e through 2.3, but changed back]
1105 explicitly associate lookahead tokens to items
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AD
1106 - solved
1107 describe shift/reduce conflicts solving.
1108 Bison used to systematically output this information on top of
1109 the report. Solved conflicts are now attached to their states.
ec3bc396 1110
402b123d 1111** Type clashes
9af3fbce
AD
1112 Previous versions don't complain when there is a type clash on
1113 the default action if the rule has a mid-rule action, such as in:
1114
1115 %type <foo> bar
1116 %%
1117 bar: '0' {} '0';
1118
1119 This is fixed.
a861a339 1120
402b123d 1121** GNU M4 is now required when using Bison.
f987e9d2 1122\f
402b123d 1123* Changes in version 1.35, 2002-03-25:
76551463 1124
402b123d 1125** C Skeleton
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1126 Some projects use Bison's C parser with C++ compilers, and define
1127 YYSTYPE as a class. The recent adjustment of C parsers for data
1128 alignment and 64 bit architectures made this impossible.
1129
1130 Because for the time being no real solution for C++ parser
1131 generation exists, kludges were implemented in the parser to
1132 maintain this use. In the future, when Bison has C++ parsers, this
1133 kludge will be disabled.
1134
1135 This kludge also addresses some C++ problems when the stack was
1136 extended.
76551463 1137\f
402b123d 1138* Changes in version 1.34, 2002-03-12:
76551463 1139
402b123d 1140** File name clashes are detected
76551463
AD
1141 $ bison foo.y -d -o foo.x
1142 fatal error: header and parser would both be named `foo.x'
1143
402b123d 1144** A missing `;' at the end of a rule triggers a warning
76551463
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1145 In accordance with POSIX, and in agreement with other
1146 Yacc implementations, Bison will mandate this semicolon in the near
1147 future. This eases the implementation of a Bison parser of Bison
1148 grammars by making this grammar LALR(1) instead of LR(2). To
1149 facilitate the transition, this release introduces a warning.
1150
402b123d 1151** Revert the C++ namespace changes introduced in 1.31, as they caused too
76551463
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1152 many portability hassles.
1153
402b123d 1154** DJGPP support added.
76551463 1155
402b123d 1156** Fix test suite portability problems.
76551463 1157\f
402b123d 1158* Changes in version 1.33, 2002-02-07:
76551463 1159
402b123d 1160** Fix C++ issues
76551463
AD
1161 Groff could not be compiled for the definition of size_t was lacking
1162 under some conditions.
1163
402b123d 1164** Catch invalid @n
76551463
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1165 As is done with $n.
1166\f
402b123d 1167* Changes in version 1.32, 2002-01-23:
76551463 1168
402b123d 1169** Fix Yacc output file names
76551463 1170
402b123d 1171** Portability fixes
76551463 1172
402b123d 1173** Italian, Dutch translations
76551463 1174\f
402b123d 1175* Changes in version 1.31, 2002-01-14:
52d1aeee 1176
402b123d 1177** Many Bug Fixes
52d1aeee 1178
402b123d 1179** GNU Gettext and %expect
52d1aeee
MA
1180 GNU Gettext asserts 10 s/r conflicts, but there are 7. Now that
1181 Bison dies on incorrect %expectations, we fear there will be
1182 too many bug reports for Gettext, so _for the time being_, %expect
1183 does not trigger an error when the input file is named `plural.y'.
1184
402b123d 1185** Use of alloca in parsers
52d1aeee
MA
1186 If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use
1187 malloc exclusively. Since 1.29, but was not NEWS'ed.
1188
1189 alloca is used only when compiled with GCC, to avoid portability
1190 problems as on AIX.
1191
402b123d 1192** yyparse now returns 2 if memory is exhausted; formerly it dumped core.
b47dbebe 1193
402b123d 1194** When the generated parser lacks debugging code, YYDEBUG is now 0
52d1aeee
MA
1195 (as POSIX requires) instead of being undefined.
1196
402b123d 1197** User Actions
52d1aeee
MA
1198 Bison has always permitted actions such as { $$ = $1 }: it adds the
1199 ending semicolon. Now if in Yacc compatibility mode, the semicolon
1200 is no longer output: one has to write { $$ = $1; }.
1201
402b123d 1202** Better C++ compliance
52d1aeee 1203 The output parsers try to respect C++ namespaces.
76551463 1204 [This turned out to be a failed experiment, and it was reverted later.]
52d1aeee 1205
402b123d 1206** Reduced Grammars
52d1aeee
MA
1207 Fixed bugs when reporting useless nonterminals.
1208
402b123d 1209** 64 bit hosts
52d1aeee
MA
1210 The parsers work properly on 64 bit hosts.
1211
402b123d 1212** Error messages
52d1aeee
MA
1213 Some calls to strerror resulted in scrambled or missing error messages.
1214
402b123d 1215** %expect
52d1aeee
MA
1216 When the number of shift/reduce conflicts is correct, don't issue
1217 any warning.
1218
402b123d 1219** The verbose report includes the rule line numbers.
52d1aeee 1220
402b123d 1221** Rule line numbers are fixed in traces.
52d1aeee 1222
402b123d 1223** Swedish translation
52d1aeee 1224
402b123d 1225** Parse errors
52d1aeee
MA
1226 Verbose parse error messages from the parsers are better looking.
1227 Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'(''
1228 Now: parse error: unexpected '/', expecting "number" or '-' or '('
1229
402b123d 1230** Fixed parser memory leaks.
52d1aeee
MA
1231 When the generated parser was using malloc to extend its stacks, the
1232 previous allocations were not freed.
1233
402b123d 1234** Fixed verbose output file.
52d1aeee
MA
1235 Some newlines were missing.
1236 Some conflicts in state descriptions were missing.
1237
402b123d 1238** Fixed conflict report.
52d1aeee
MA
1239 Option -v was needed to get the result.
1240
402b123d 1241** %expect
52d1aeee
MA
1242 Was not used.
1243 Mismatches are errors, not warnings.
1244
402b123d 1245** Fixed incorrect processing of some invalid input.
52d1aeee 1246
402b123d 1247** Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H.
52d1aeee 1248
402b123d 1249** Fixed some typos in the documentation.
52d1aeee 1250
402b123d 1251** %token MY_EOF 0 is supported.
52d1aeee
MA
1252 Before, MY_EOF was silently renumbered as 257.
1253
402b123d 1254** doc/refcard.tex is updated.
52d1aeee 1255
402b123d 1256** %output, %file-prefix, %name-prefix.
52d1aeee
MA
1257 New.
1258
402b123d 1259** --output
52d1aeee
MA
1260 New, aliasing `--output-file'.
1261\f
402b123d 1262* Changes in version 1.30, 2001-10-26:
342b8b6e 1263
402b123d 1264** `--defines' and `--graph' have now an optional argument which is the
fdac0091 1265 output file name. `-d' and `-g' do not change; they do not take any
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AD
1266 argument.
1267
402b123d 1268** `%source_extension' and `%header_extension' are removed, failed
342b8b6e
AD
1269 experiment.
1270
402b123d 1271** Portability fixes.
f987e9d2 1272\f
402b123d 1273* Changes in version 1.29, 2001-09-07:
342b8b6e 1274
402b123d 1275** The output file does not define const, as this caused problems when used
342b8b6e
AD
1276 with common autoconfiguration schemes. If you still use ancient compilers
1277 that lack const, compile with the equivalent of the C compiler option
1278 `-Dconst='. autoconf's AC_C_CONST macro provides one way to do this.
1279
402b123d 1280** Added `-g' and `--graph'.
f87a2205 1281
402b123d 1282** The Bison manual is now distributed under the terms of the GNU FDL.
f2b5126e 1283
402b123d 1284** The input and the output files has automatically a similar extension.
234a3be3 1285
402b123d 1286** Russian translation added.
f87a2205 1287
402b123d 1288** NLS support updated; should hopefully be less troublesome.
f87a2205 1289
402b123d 1290** Added the old Bison reference card.
c33638bb 1291
402b123d 1292** Added `--locations' and `%locations'.
6deb4447 1293
402b123d 1294** Added `-S' and `--skeleton'.
cd5bd6ac 1295
402b123d 1296** `%raw', `-r', `--raw' is disabled.
62ab6972 1297
402b123d 1298** Special characters are escaped when output. This solves the problems
cd5bd6ac
AD
1299 of the #line lines with path names including backslashes.
1300
402b123d 1301** New directives.
4ecbf796
MA
1302 `%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose',
1303 `%debug', `%source_extension' and `%header_extension'.
f987e9d2 1304
402b123d 1305** @$
f987e9d2 1306 Automatic location tracking.
f87a2205 1307\f
402b123d 1308* Changes in version 1.28, 1999-07-06:
d2e00347 1309
402b123d 1310** Should compile better now with K&R compilers.
d2e00347 1311
402b123d 1312** Added NLS.
d2e00347 1313
402b123d 1314** Fixed a problem with escaping the double quote character.
d2e00347 1315
402b123d 1316** There is now a FAQ.
d2e00347 1317\f
402b123d 1318* Changes in version 1.27:
5c31c3c2 1319
402b123d 1320** The make rule which prevented bison.simple from being created on
5c31c3c2
JT
1321 some systems has been fixed.
1322\f
402b123d 1323* Changes in version 1.26:
4be07551 1324
402b123d 1325** Bison now uses automake.
4be07551 1326
402b123d 1327** New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
4be07551 1328
402b123d 1329** Token numbers now start at 257 as previously documented, not 258.
4be07551 1330
402b123d 1331** Bison honors the TMPDIR environment variable.
4be07551 1332
402b123d 1333** A couple of buffer overruns have been fixed.
f51dbca1 1334
402b123d 1335** Problems when closing files should now be reported.
f51dbca1 1336
402b123d 1337** Generated parsers should now work even on operating systems which do
f51dbca1 1338 not provide alloca().
4be07551 1339\f
402b123d 1340* Changes in version 1.25, 1995-10-16:
df8878c5 1341
402b123d 1342** Errors in the input grammar are not fatal; Bison keeps reading
df8878c5 1343the grammar file, and reports all the errors found in it.
8c44d3ec 1344
402b123d 1345** Tokens can now be specified as multiple-character strings: for
df8878c5
RS
1346example, you could use "<=" for a token which looks like <=, instead
1347of chosing a name like LESSEQ.
1348
402b123d 1349** The %token_table declaration says to write a table of tokens (names
df8878c5
RS
1350and numbers) into the parser file. The yylex function can use this
1351table to recognize multiple-character string tokens, or for other
1352purposes.
1353
402b123d 1354** The %no_lines declaration says not to generate any #line preprocessor
df8878c5
RS
1355directives in the parser file.
1356
402b123d 1357** The %raw declaration says to use internal Bison token numbers, not
df8878c5
RS
1358Yacc-compatible token numbers, when token names are defined as macros.
1359
402b123d 1360** The --no-parser option produces the parser tables without including
df8878c5
RS
1361the parser engine; a project can now use its own parser engine.
1362The actions go into a separate file called NAME.act, in the form of
1363a switch statement body.
1364\f
402b123d 1365* Changes in version 1.23:
6780ca7a 1366
4d019228
DM
1367The user can define YYPARSE_PARAM as the name of an argument to be
1368passed into yyparse. The argument should have type void *. It should
1369actually point to an object. Grammar actions can access the variable
1370by casting it to the proper pointer type.
6780ca7a 1371
6780ca7a 1372Line numbers in output file corrected.
6780ca7a 1373\f
402b123d 1374* Changes in version 1.22:
6780ca7a
DM
1375
1376--help option added.
6780ca7a 1377\f
402b123d 1378* Changes in version 1.20:
6780ca7a
DM
1379
1380Output file does not redefine const for C++.
9f4503d6
AD
1381
1382Local Variables:
1383mode: outline
1384End:
76551463
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1385
1386-----
1387
e141f4d4 1388Copyright (C) 1995-2010 Free Software Foundation, Inc.
76551463 1389
74553c98 1390This file is part of Bison, the GNU Parser Generator.
76551463 1391
f16b0819 1392This program is free software: you can redistribute it and/or modify
76551463 1393it under the terms of the GNU General Public License as published by
f16b0819
PE
1394the Free Software Foundation, either version 3 of the License, or
1395(at your option) any later version.
76551463 1396
f16b0819 1397This program is distributed in the hope that it will be useful,
76551463
AD
1398but WITHOUT ANY WARRANTY; without even the implied warranty of
1399MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
1400GNU General Public License for more details.
1401
1402You should have received a copy of the GNU General Public License
f16b0819 1403along with this program. If not, see <http://www.gnu.org/licenses/>.