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1Bison News
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4Changes in version 1.875e:
5
6* The option `--report=lookahead' was changed to `--report=look-ahead'.
7 The old spelling still works, but is not documented and will be removed.
8
e476c87d 9Changes in version 1.875d, 2004-05-21:
1452af69 10
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11* Unescaped newlines are no longer allowed in character constants or
12 string literals. They were never portable, and GCC 3.4.0 has
13 dropped support for them. Better diagnostics are now generated if
14 forget a closing quote.
15
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16* NUL bytes are no longer allowed in Bison string literals, unfortunately.
17
18* %token numbers can now be hexadecimal integers, e.g., `%token FOO 0x12d'.
19 This is a GNU extension.
20
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21* A new directive "%expect-rr N" specifies the expected number of
22 reduce/reduce conflicts in GLR parsers.
23
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24* Experimental %destructor support has been added to lalr1.cc.
25
26Changes in version 1.875c, 2003-08-25:
27
28 (Just bug fixes.)
6040d338 29
3473d0f8 30Changes in version 1.875b, 2003-06-17:
d5a3fe37 31
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32* GLR grammars now support locations.
33
34* Semicolon changes:
35 - Semicolons are now allowed before "|" in grammar rules, as POSIX requires.
36 - Stray semicolons are no longer allowed at the start of a grammar.
37 - Semicolons are now required after in-grammar declarations.
829fd4c7 38
92898986 39Changes in version 1.875a, 2003-02-01:
d600ee67 40
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41* For now, %expect-count violations are now just warnings, not errors.
42 This is for compatibility with Bison 1.75 and earlier (when there are
69363a9e 43 reduce/reduce conflicts) and with Bison 1.30 and earlier (when there
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44 are too many or too few shift/reduce conflicts). However, in future
45 versions of Bison we plan to improve the %expect machinery so that
46 these violations will become errors again.
69363a9e 47
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48* New configure option --disable-yacc, to disable installation of the
49 yacc command and -ly library introduced in 1.875 for POSIX conformance.
50\f
dc546b0f 51Changes in version 1.875, 2003-01-01:
963fcc17 52
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53* The documentation license has been upgraded to version 1.2
54 of the GNU Free Documentation License.
75eb3bc4 55
dc546b0f 56* syntax error processing
75eb3bc4 57
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58 - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error
59 locations too. This fixes bugs in error-location computation.
75eb3bc4 60
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61 - %destructor
62 It is now possible to reclaim the memory associated to symbols
63 discarded during error recovery. This feature is still experimental.
20daca06 64
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65 - %error-verbose
66 This new directive is preferred over YYERROR_VERBOSE.
74724a70 67
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68 - #defining yyerror to steal internal variables is discouraged.
69 It is not guaranteed to work forever.
d1de5372 70
dc546b0f 71* POSIX conformance
d1de5372 72
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73 - Semicolons are once again optional at the end of grammar rules.
74 This reverts to the behavior of Bison 1.33 and earlier, and improves
75 compatibility with Yacc.
74724a70 76
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77 - `parse error' -> `syntax error'
78 Bison now uniformly uses the term `syntax error'; formerly, the code
79 and manual sometimes used the term `parse error' instead. POSIX
80 requires `syntax error' in diagnostics, and it was thought better to
81 be consistent.
74724a70 82
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83 - The documentation now emphasizes that yylex and yyerror must be
84 declared before use. C99 requires this.
d1de5372 85
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86 - Bison now parses C99 lexical constructs like UCNs and
87 backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires.
d1de5372 88
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89 - File names are properly escaped in C output. E.g., foo\bar.y is
90 output as "foo\\bar.y".
6780ca7a 91
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92 - Yacc command and library now available
93 The Bison distribution now installs a `yacc' command, as POSIX requires.
94 Also, Bison now installs a small library liby.a containing
95 implementations of Yacc-compatible yyerror and main functions.
96 This library is normally not useful, but POSIX requires it.
6e649e65 97
dc546b0f 98 - Type clashes now generate warnings, not errors.
6e649e65 99
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100 - If the user does not define YYSTYPE as a macro, Bison now declares it
101 using typedef instead of defining it as a macro.
102 For consistency, YYLTYPE is also declared instead of defined.
9501dc6e 103
dc546b0f 104* Other compatibility issues
886a425c 105
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106 - %union directives can now have a tag before the `{', e.g., the
107 directive `%union foo {...}' now generates the C code
108 `typedef union foo { ... } YYSTYPE;'; this is for Yacc compatibility.
109 The default union tag is `YYSTYPE', for compatibility with Solaris 9 Yacc.
110 For consistency, YYLTYPE's struct tag is now `YYLTYPE' not `yyltype'.
111 This is for compatibility with both Yacc and Bison 1.35.
72f889cc 112
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113 - `;' is output before the terminating `}' of an action, for
114 compatibility with Bison 1.35.
886a425c 115
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116 - Bison now uses a Yacc-style format for conflict reports, e.g.,
117 `conflicts: 2 shift/reduce, 1 reduce/reduce'.
437c2d80 118
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119 - `yystype' and `yyltype' are now obsolescent macros instead of being
120 typedefs or tags; they are no longer documented and are planned to be
121 withdrawn in a future release.
2a8d363a 122
dc546b0f 123* GLR parser notes
2a8d363a 124
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125 - GLR and inline
126 Users of Bison have to decide how they handle the portability of the
127 C keyword `inline'.
959e5f51 128
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129 - `parsing stack overflow...' -> `parser stack overflow'
130 GLR parsers now report `parser stack overflow' as per the Bison manual.
900c5db5 131
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132* Bison now warns if it detects conflicting outputs to the same file,
133 e.g., it generates a warning for `bison -d -o foo.h foo.y' since
134 that command outputs both code and header to foo.h.
6e40b4eb 135
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136* #line in output files
137 - --no-line works properly.
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138
139* Bison can no longer be built by a K&R C compiler; it requires C89 or
140 later to be built. This change originally took place a few versions
141 ago, but nobody noticed until we recently asked someone to try
142 building Bison with a K&R C compiler.
d600ee67 143\f
5c16c6b1 144Changes in version 1.75, 2002-10-14:
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145
146* Bison should now work on 64-bit hosts.
147
b7195100 148* Indonesian translation thanks to Tedi Heriyanto.
7933f2b5 149
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150* GLR parsers
151 Fix spurious parse errors.
152
153* Pure parsers
154 Some people redefine yyerror to steal yyparse' private variables.
155 Reenable this trick until an official feature replaces it.
156
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157* Type Clashes
158 In agreement with POSIX and with other Yaccs, leaving a default
159 action is valid when $$ is untyped, and $1 typed:
160
161 untyped: ... typed;
162
163 but the converse remains an error:
164
165 typed: ... untyped;
166
167* Values of mid-rule actions
168 The following code:
169
170 foo: { ... } { $$ = $1; } ...
171
172 was incorrectly rejected: $1 is defined in the second mid-rule
173 action, and is equal to the $$ of the first mid-rule action.
d600ee67 174\f
420f93c8 175Changes in version 1.50, 2002-10-04:
adc8c848 176
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177* GLR parsing
178 The declaration
179 %glr-parser
180 causes Bison to produce a Generalized LR (GLR) parser, capable of handling
181 almost any context-free grammar, ambiguous or not. The new declarations
e8832397 182 %dprec and %merge on grammar rules allow parse-time resolution of
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183 ambiguities. Contributed by Paul Hilfinger.
184
7933f2b5 185 Unfortunately Bison 1.50 does not work properly on 64-bit hosts
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186 like the Alpha, so please stick to 32-bit hosts for now.
187
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188* Output Directory
189 When not in Yacc compatibility mode, when the output file was not
e88dbdbf 190 specified, running `bison foo/bar.y' created `foo/bar.c'. It
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191 now creates `bar.c'.
192
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193* Undefined token
194 The undefined token was systematically mapped to 2 which prevented
e88dbdbf 195 the use of 2 by the user. This is no longer the case.
007a50a4 196
77714df2 197* Unknown token numbers
e88dbdbf 198 If yylex returned an out of range value, yyparse could die. This is
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199 no longer the case.
200
23c5a174 201* Error token
e88dbdbf 202 According to POSIX, the error token must be 256.
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203 Bison extends this requirement by making it a preference: *if* the
204 user specified that one of her tokens is numbered 256, then error
205 will be mapped onto another number.
206
217598da 207* Verbose error messages
e88dbdbf 208 They no longer report `..., expecting error or...' for states where
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209 error recovery is possible.
210
211* End token
212 Defaults to `$end' instead of `$'.
213
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214* Error recovery now conforms to documentation and to POSIX
215 When a Bison-generated parser encounters a syntax error, it now pops
216 the stack until it finds a state that allows shifting the error
217 token. Formerly, it popped the stack until it found a state that
218 allowed some non-error action other than a default reduction on the
219 error token. The new behavior has long been the documented behavior,
220 and has long been required by POSIX. For more details, please see
221 <http://mail.gnu.org/pipermail/bug-bison/2002-May/001452.html>.
222
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223* Traces
224 Popped tokens and nonterminals are now reported.
225
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226* Larger grammars
227 Larger grammars are now supported (larger token numbers, larger grammar
228 size (= sum of the LHS and RHS lengths), larger LALR tables).
229 Formerly, many of these numbers ran afoul of 16-bit limits;
230 now these limits are 32 bits on most hosts.
355e7c1c 231
77714df2 232* Explicit initial rule
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233 Bison used to play hacks with the initial rule, which the user does
234 not write. It is now explicit, and visible in the reports and
235 graphs as rule 0.
23c5a174 236
77714df2 237* Useless rules
643a5994 238 Before, Bison reported the useless rules, but, although not used,
77714df2 239 included them in the parsers. They are now actually removed.
23c5a174 240
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241* Useless rules, useless nonterminals
242 They are now reported, as a warning, with their locations.
243
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244* Rules never reduced
245 Rules that can never be reduced because of conflicts are now
246 reported.
247
77714df2 248* Incorrect `Token not used'
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249 On a grammar such as
250
251 %token useless useful
252 %%
253 exp: '0' %prec useful;
254
255 where a token was used to set the precedence of the last rule,
256 bison reported both `useful' and `useless' as useless tokens.
257
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258* Revert the C++ namespace changes introduced in 1.31
259 as they caused too many portability hassles.
0179dd65 260
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261* Default locations
262 By an accident of design, the default computation of @$ was
263 performed after another default computation was performed: @$ = @1.
264 The latter is now removed: YYLLOC_DEFAULT is fully responsible of
265 the computation of @$.
adc8c848 266
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267* Token end-of-file
268 The token end of file may be specified by the user, in which case,
269 the user symbol is used in the reports, the graphs, and the verbose
a861a339 270 error messages instead of `$end', which remains being the default.
b7c49edf 271 For instance
7bd6c77e 272 %token MYEOF 0
b7c49edf 273 or
7bd6c77e 274 %token MYEOF 0 "end of file"
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275
276* Semantic parser
277 This old option, which has been broken for ages, is removed.
278
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279* New translations
280 Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
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281 Croatian, thanks to Denis Lackovic.
282
77714df2 283* Incorrect token definitions
e88dbdbf 284 When given `%token 'a' "A"', Bison used to output `#define 'a' 65'.
b87f8b21 285
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286* Token definitions as enums
287 Tokens are output both as the traditional #define's, and, provided
288 the compiler supports ANSI C or is a C++ compiler, as enums.
e88dbdbf 289 This lets debuggers display names instead of integers.
77714df2 290
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291* Reports
292 In addition to --verbose, bison supports --report=THINGS, which
293 produces additional information:
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294 - itemset
295 complete the core item sets with their closure
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296 - lookahead [changed to `look-ahead' in 1.875e and later]
297 explicitly associate look-ahead tokens to items
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298 - solved
299 describe shift/reduce conflicts solving.
300 Bison used to systematically output this information on top of
301 the report. Solved conflicts are now attached to their states.
ec3bc396 302
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303* Type clashes
304 Previous versions don't complain when there is a type clash on
305 the default action if the rule has a mid-rule action, such as in:
306
307 %type <foo> bar
308 %%
309 bar: '0' {} '0';
310
311 This is fixed.
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312
313* GNU M4 is now required when using Bison.
f987e9d2 314\f
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315Changes in version 1.35, 2002-03-25:
316
317* C Skeleton
318 Some projects use Bison's C parser with C++ compilers, and define
319 YYSTYPE as a class. The recent adjustment of C parsers for data
320 alignment and 64 bit architectures made this impossible.
321
322 Because for the time being no real solution for C++ parser
323 generation exists, kludges were implemented in the parser to
324 maintain this use. In the future, when Bison has C++ parsers, this
325 kludge will be disabled.
326
327 This kludge also addresses some C++ problems when the stack was
328 extended.
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329\f
330Changes in version 1.34, 2002-03-12:
331
332* File name clashes are detected
333 $ bison foo.y -d -o foo.x
334 fatal error: header and parser would both be named `foo.x'
335
336* A missing `;' at the end of a rule triggers a warning
337 In accordance with POSIX, and in agreement with other
338 Yacc implementations, Bison will mandate this semicolon in the near
339 future. This eases the implementation of a Bison parser of Bison
340 grammars by making this grammar LALR(1) instead of LR(2). To
341 facilitate the transition, this release introduces a warning.
342
343* Revert the C++ namespace changes introduced in 1.31, as they caused too
344 many portability hassles.
345
346* DJGPP support added.
347
348* Fix test suite portability problems.
349\f
350Changes in version 1.33, 2002-02-07:
351
352* Fix C++ issues
353 Groff could not be compiled for the definition of size_t was lacking
354 under some conditions.
355
356* Catch invalid @n
357 As is done with $n.
358\f
359Changes in version 1.32, 2002-01-23:
360
361* Fix Yacc output file names
362
363* Portability fixes
364
365* Italian, Dutch translations
366\f
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367Changes in version 1.31, 2002-01-14:
368
369* Many Bug Fixes
370
371* GNU Gettext and %expect
372 GNU Gettext asserts 10 s/r conflicts, but there are 7. Now that
373 Bison dies on incorrect %expectations, we fear there will be
374 too many bug reports for Gettext, so _for the time being_, %expect
375 does not trigger an error when the input file is named `plural.y'.
376
377* Use of alloca in parsers
378 If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use
379 malloc exclusively. Since 1.29, but was not NEWS'ed.
380
381 alloca is used only when compiled with GCC, to avoid portability
382 problems as on AIX.
383
384* When the generated parser lacks debugging code, YYDEBUG is now 0
385 (as POSIX requires) instead of being undefined.
386
387* User Actions
388 Bison has always permitted actions such as { $$ = $1 }: it adds the
389 ending semicolon. Now if in Yacc compatibility mode, the semicolon
390 is no longer output: one has to write { $$ = $1; }.
391
392* Better C++ compliance
393 The output parsers try to respect C++ namespaces.
76551463 394 [This turned out to be a failed experiment, and it was reverted later.]
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395
396* Reduced Grammars
397 Fixed bugs when reporting useless nonterminals.
398
399* 64 bit hosts
400 The parsers work properly on 64 bit hosts.
401
402* Error messages
403 Some calls to strerror resulted in scrambled or missing error messages.
404
405* %expect
406 When the number of shift/reduce conflicts is correct, don't issue
407 any warning.
408
409* The verbose report includes the rule line numbers.
410
411* Rule line numbers are fixed in traces.
412
413* Swedish translation
414
415* Parse errors
416 Verbose parse error messages from the parsers are better looking.
417 Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'(''
418 Now: parse error: unexpected '/', expecting "number" or '-' or '('
419
420* Fixed parser memory leaks.
421 When the generated parser was using malloc to extend its stacks, the
422 previous allocations were not freed.
423
424* Fixed verbose output file.
425 Some newlines were missing.
426 Some conflicts in state descriptions were missing.
427
428* Fixed conflict report.
429 Option -v was needed to get the result.
430
431* %expect
432 Was not used.
433 Mismatches are errors, not warnings.
434
435* Fixed incorrect processing of some invalid input.
436
437* Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H.
438
439* Fixed some typos in the documentation.
440
441* %token MY_EOF 0 is supported.
442 Before, MY_EOF was silently renumbered as 257.
443
444* doc/refcard.tex is updated.
445
446* %output, %file-prefix, %name-prefix.
447 New.
448
449* --output
450 New, aliasing `--output-file'.
451\f
76551463 452Changes in version 1.30, 2001-10-26:
342b8b6e 453
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454* `--defines' and `--graph' have now an optional argument which is the
455 output file name. `-d' and `-g' do not change; they do not take any
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456 argument.
457
458* `%source_extension' and `%header_extension' are removed, failed
459 experiment.
460
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461* Portability fixes.
462\f
9f4503d6 463Changes in version 1.29, 2001-09-07:
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464
465* The output file does not define const, as this caused problems when used
466 with common autoconfiguration schemes. If you still use ancient compilers
467 that lack const, compile with the equivalent of the C compiler option
468 `-Dconst='. autoconf's AC_C_CONST macro provides one way to do this.
469
470* Added `-g' and `--graph'.
f87a2205 471
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472* The Bison manual is now distributed under the terms of the GNU FDL.
473
f1c63ced 474* The input and the output files has automatically a similar extension.
234a3be3 475
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476* Russian translation added.
477
478* NLS support updated; should hopefully be less troublesome.
479
480* Added the old Bison reference card.
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481
482* Added `--locations' and `%locations'.
6deb4447 483
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484* Added `-S' and `--skeleton'.
485
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486* `%raw', `-r', `--raw' is disabled.
487
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488* Special characters are escaped when output. This solves the problems
489 of the #line lines with path names including backslashes.
490
6deb4447 491* New directives.
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492 `%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose',
493 `%debug', `%source_extension' and `%header_extension'.
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494
495* @$
496 Automatic location tracking.
f87a2205 497\f
9f4503d6 498Changes in version 1.28, 1999-07-06:
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499
500* Should compile better now with K&R compilers.
501
502* Added NLS.
503
504* Fixed a problem with escaping the double quote character.
505
506* There is now a FAQ.
507\f
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508Changes in version 1.27:
509
510* The make rule which prevented bison.simple from being created on
511 some systems has been fixed.
512\f
513Changes in version 1.26:
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514
515* Bison now uses automake.
516
517* New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
518
519* Token numbers now start at 257 as previously documented, not 258.
520
521* Bison honors the TMPDIR environment variable.
522
523* A couple of buffer overruns have been fixed.
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524
525* Problems when closing files should now be reported.
526
527* Generated parsers should now work even on operating systems which do
528 not provide alloca().
4be07551 529\f
9f4503d6 530Changes in version 1.25, 1995-10-16:
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531
532* Errors in the input grammar are not fatal; Bison keeps reading
533the grammar file, and reports all the errors found in it.
8c44d3ec 534
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535* Tokens can now be specified as multiple-character strings: for
536example, you could use "<=" for a token which looks like <=, instead
537of chosing a name like LESSEQ.
538
539* The %token_table declaration says to write a table of tokens (names
540and numbers) into the parser file. The yylex function can use this
541table to recognize multiple-character string tokens, or for other
542purposes.
543
544* The %no_lines declaration says not to generate any #line preprocessor
545directives in the parser file.
546
547* The %raw declaration says to use internal Bison token numbers, not
548Yacc-compatible token numbers, when token names are defined as macros.
549
550* The --no-parser option produces the parser tables without including
551the parser engine; a project can now use its own parser engine.
552The actions go into a separate file called NAME.act, in the form of
553a switch statement body.
554\f
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555Changes in version 1.23:
556
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557The user can define YYPARSE_PARAM as the name of an argument to be
558passed into yyparse. The argument should have type void *. It should
559actually point to an object. Grammar actions can access the variable
560by casting it to the proper pointer type.
6780ca7a 561
6780ca7a 562Line numbers in output file corrected.
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563\f
564Changes in version 1.22:
565
566--help option added.
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567\f
568Changes in version 1.20:
569
570Output file does not redefine const for C++.
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571
572Local Variables:
573mode: outline
574End:
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575
576-----
577
1452af69 578Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
dc546b0f 579Free Software Foundation, Inc.
76551463 580
75eb3bc4 581This file is part of Bison, the GNU Compiler Compiler.
76551463 582
75eb3bc4 583Bison is free software; you can redistribute it and/or modify
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584it under the terms of the GNU General Public License as published by
585the Free Software Foundation; either version 2, or (at your option)
586any later version.
587
75eb3bc4 588Bison is distributed in the hope that it will be useful,
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589but WITHOUT ANY WARRANTY; without even the implied warranty of
590MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
591GNU General Public License for more details.
592
593You should have received a copy of the GNU General Public License
594along with autoconf; see the file COPYING. If not, write to
595the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
596Boston, MA 02111-1307, USA.