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4* Changes in version ?.? (????-??-??):
5
6* Changes in version 2.4.2 (????-??-??):
7
8* Changes in version 2.4.1 (2008-12-11):
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10* Java skeleton improvements:
11
12 The constants for token names were moved to the Lexer interface.
13 Also, it is possible to add code to the parser's constructors using
14 "%code init" and "%define init_throws".
c9ba9e59 15
402b123d 16* Changes in version 2.4 (2008-11-02):
7bd1665a 17
402b123d 18** %language is an experimental feature.
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19
20 We first introduced this feature in test release 2.3b as a cleaner
21 alternative to %skeleton. Since then, we have discussed the possibility of
22 modifying its effect on Bison's output file names. Thus, in this release,
23 we consider %language to be an experimental feature that will likely evolve
24 in future releases.
7bd1665a 25
402b123d 26** Forward compatibility with GNU M4 has been improved.
241fda7a 27
402b123d 28** Several bugs in the C++ skeleton and the experimental Java skeleton have been
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29 fixed.
30
402b123d 31* Changes in version 2.3b (2008-05-27):
35fe0834 32
402b123d 33** The quotes around NAME that used to be required in the following directive
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34 are now deprecated:
35
36 %define NAME "VALUE"
37
402b123d 38** The directive `%pure-parser' is now deprecated in favor of:
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39
40 %define api.pure
41
42 which has the same effect except that Bison is more careful to warn about
43 unreasonable usage in the latter case.
44
402b123d 45** Push Parsing
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46
47 Bison can now generate an LALR(1) parser in C with a push interface. That
ef1b4273 48 is, instead of invoking `yyparse', which pulls tokens from `yylex', you can
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49 push one token at a time to the parser using `yypush_parse', which will
50 return to the caller after processing each token. By default, the push
51 interface is disabled. Either of the following directives will enable it:
52
53 %define api.push_pull "push" // Just push; does not require yylex.
54 %define api.push_pull "both" // Push and pull; requires yylex.
55
56 See the new section `A Push Parser' in the Bison manual for details.
57
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58 The current push parsing interface is experimental and may evolve. More user
59 feedback will help to stabilize it.
60
402b123d 61** The -g and --graph options now output graphs in Graphviz DOT format,
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62 not VCG format. Like --graph, -g now also takes an optional FILE argument
63 and thus cannot be bundled with other short options.
c373bf8b 64
402b123d 65** Java
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66
67 Bison can now generate an LALR(1) parser in Java. The skeleton is
68 `data/lalr1.java'. Consider using the new %language directive instead of
69 %skeleton to select it.
70
71 See the new section `Java Parsers' in the Bison manual for details.
72
73 The current Java interface is experimental and may evolve. More user
74 feedback will help to stabilize it.
75
402b123d 76** %language
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77
78 This new directive specifies the programming language of the generated
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79 parser, which can be C (the default), C++, or Java. Besides the skeleton
80 that Bison uses, the directive affects the names of the generated files if
81 the grammar file's name ends in ".y".
59da312b 82
402b123d 83** XML Automaton Report
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84
85 Bison can now generate an XML report of the LALR(1) automaton using the new
86 `--xml' option. The current XML schema is experimental and may evolve. More
87 user feedback will help to stabilize it.
c373bf8b 88
402b123d 89** The grammar file may now specify the name of the parser header file using
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90 %defines. For example:
91
92 %defines "parser.h"
93
402b123d 94** When reporting useless rules, useless nonterminals, and unused terminals,
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95 Bison now employs the terms "useless in grammar" instead of "useless",
96 "useless in parser" instead of "never reduced", and "unused in grammar"
97 instead of "unused".
cff03fb2 98
402b123d 99** Unreachable State Removal
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100
101 Previously, Bison sometimes generated parser tables containing unreachable
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102 states. A state can become unreachable during conflict resolution if Bison
103 disables a shift action leading to it from a predecessor state. Bison now:
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104
105 1. Removes unreachable states.
106
107 2. Does not report any conflicts that appeared in unreachable states.
108 WARNING: As a result, you may need to update %expect and %expect-rr
109 directives in existing grammar files.
110
111 3. For any rule used only in such states, Bison now reports the rule as
cff03fb2 112 "useless in parser due to conflicts".
75ad86ee 113
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114 This feature can be disabled with the following directive:
115
116 %define lr.keep_unreachable_states
117
118 See the %define entry in the `Bison Declaration Summary' in the Bison manual
119 for further discussion.
120
402b123d 121** Lookahead Set Correction in the `.output' Report
b1cc23c4 122
c373bf8b 123 When instructed to generate a `.output' file including lookahead sets
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124 (using `--report=lookahead', for example), Bison now prints each reduction's
125 lookahead set only next to the associated state's one item that (1) is
126 associated with the same rule as the reduction and (2) has its dot at the end
127 of its RHS. Previously, Bison also erroneously printed the lookahead set
128 next to all of the state's other items associated with the same rule. This
129 bug affected only the `.output' file and not the generated parser source
130 code.
131
402b123d 132** --report-file=FILE is a new option to override the default `.output' file
59da312b 133 name.
1bb2bd75 134
402b123d 135** The `=' that used to be required in the following directives is now
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136 deprecated:
137
138 %file-prefix "parser"
139 %name-prefix "c_"
140 %output "parser.c"
141
402b123d 142** An Alternative to `%{...%}' -- `%code QUALIFIER {CODE}'
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143
144 Bison 2.3a provided a new set of directives as a more flexible alternative to
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145 the traditional Yacc prologue blocks. Those have now been consolidated into
146 a single %code directive with an optional qualifier field, which identifies
147 the purpose of the code and thus the location(s) where Bison should generate
148 it:
149
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150 1. `%code {CODE}' replaces `%after-header {CODE}'
151 2. `%code requires {CODE}' replaces `%start-header {CODE}'
152 3. `%code provides {CODE}' replaces `%end-header {CODE}'
153 4. `%code top {CODE}' replaces `%before-header {CODE}'
8e0a5e9e 154
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155 See the %code entries in section `Bison Declaration Summary' in the Bison
156 manual for a summary of the new functionality. See the new section `Prologue
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157 Alternatives' for a detailed discussion including the advantages of %code
158 over the traditional Yacc prologues.
159
160 The prologue alternatives are experimental. More user feedback will help to
161 determine whether they should become permanent features.
162
402b123d 163** Revised warning: unset or unused mid-rule values
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164
165 Since Bison 2.2, Bison has warned about mid-rule values that are set but not
166 used within any of the actions of the parent rule. For example, Bison warns
167 about unused $2 in:
168
169 exp: '1' { $$ = 1; } '+' exp { $$ = $1 + $4; };
170
171 Now, Bison also warns about mid-rule values that are used but not set. For
172 example, Bison warns about unset $$ in the mid-rule action in:
173
174 exp: '1' { $1 = 1; } '+' exp { $$ = $2 + $4; };
175
176 However, Bison now disables both of these warnings by default since they
177 sometimes prove to be false alarms in existing grammars employing the Yacc
178 constructs $0 or $-N (where N is some positive integer).
179
59da312b 180 To enable these warnings, specify the option `--warnings=midrule-values' or
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181 `-W', which is a synonym for `--warnings=all'.
182
402b123d 183** Default %destructor or %printer with `<*>' or `<>'
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184
185 Bison now recognizes two separate kinds of default %destructor's and
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186 %printer's:
187
188 1. Place `<*>' in a %destructor/%printer symbol list to define a default
189 %destructor/%printer for all grammar symbols for which you have formally
190 declared semantic type tags.
191
3ebecc24 192 2. Place `<>' in a %destructor/%printer symbol list to define a default
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193 %destructor/%printer for all grammar symbols without declared semantic
194 type tags.
195
196 Bison no longer supports the `%symbol-default' notation from Bison 2.3a.
3ebecc24 197 `<*>' and `<>' combined achieve the same effect with one exception: Bison no
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198 longer applies any %destructor to a mid-rule value if that mid-rule value is
199 not actually ever referenced using either $$ or $n in a semantic action.
200
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201 The default %destructor's and %printer's are experimental. More user
202 feedback will help to determine whether they should become permanent
203 features.
204
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205 See the section `Freeing Discarded Symbols' in the Bison manual for further
206 details.
207
402b123d 208** %left, %right, and %nonassoc can now declare token numbers. This is required
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209 by POSIX. However, see the end of section `Operator Precedence' in the Bison
210 manual for a caveat concerning the treatment of literal strings.
211
402b123d 212** The nonfunctional --no-parser, -n, and %no-parser options have been
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213 completely removed from Bison.
214
402b123d 215* Changes in version 2.3a, 2006-09-13:
742e4900 216
402b123d 217** Instead of %union, you can define and use your own union type
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218 YYSTYPE if your grammar contains at least one <type> tag.
219 Your YYSTYPE need not be a macro; it can be a typedef.
220 This change is for compatibility with other Yacc implementations,
221 and is required by POSIX.
222
402b123d 223** Locations columns and lines start at 1.
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224 In accordance with the GNU Coding Standards and Emacs.
225
402b123d 226** You may now declare per-type and default %destructor's and %printer's:
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227
228 For example:
229
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230 %union { char *string; }
231 %token <string> STRING1
232 %token <string> STRING2
233 %type <string> string1
234 %type <string> string2
235 %union { char character; }
236 %token <character> CHR
237 %type <character> chr
238 %destructor { free ($$); } %symbol-default
239 %destructor { free ($$); printf ("%d", @$.first_line); } STRING1 string1
240 %destructor { } <character>
241
242 guarantees that, when the parser discards any user-defined symbol that has a
243 semantic type tag other than `<character>', it passes its semantic value to
244 `free'. However, when the parser discards a `STRING1' or a `string1', it
245 also prints its line number to `stdout'. It performs only the second
246 `%destructor' in this case, so it invokes `free' only once.
ec5479ce 247
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248 [Although we failed to mention this here in the 2.3a release, the default
249 %destructor's and %printer's were experimental, and they were rewritten in
250 future versions.]
251
402b123d 252** Except for LALR(1) parsers in C with POSIX Yacc emulation enabled (with `-y',
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253 `--yacc', or `%yacc'), Bison no longer generates #define statements for
254 associating token numbers with token names. Removing the #define statements
255 helps to sanitize the global namespace during preprocessing, but POSIX Yacc
256 requires them. Bison still generates an enum for token names in all cases.
257
402b123d 258** Handling of traditional Yacc prologue blocks is now more consistent but
34f98f46 259 potentially incompatible with previous releases of Bison.
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260
261 As before, you declare prologue blocks in your grammar file with the
262 `%{ ... %}' syntax. To generate the pre-prologue, Bison concatenates all
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263 prologue blocks that you've declared before the first %union. To generate
264 the post-prologue, Bison concatenates all prologue blocks that you've
ddc8ede1 265 declared after the first %union.
9bc0dd67 266
34f98f46 267 Previous releases of Bison inserted the pre-prologue into both the header
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268 file and the code file in all cases except for LALR(1) parsers in C. In the
269 latter case, Bison inserted it only into the code file. For parsers in C++,
270 the point of insertion was before any token definitions (which associate
271 token numbers with names). For parsers in C, the point of insertion was
272 after the token definitions.
273
274 Now, Bison never inserts the pre-prologue into the header file. In the code
275 file, it always inserts it before the token definitions.
276
402b123d 277** Bison now provides a more flexible alternative to the traditional Yacc
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278 prologue blocks: %before-header, %start-header, %end-header, and
279 %after-header.
280
281 For example, the following declaration order in the grammar file reflects the
282 order in which Bison will output these code blocks. However, you are free to
283 declare these code blocks in your grammar file in whatever order is most
284 convenient for you:
285
286 %before-header {
287 /* Bison treats this block like a pre-prologue block: it inserts it into
288 * the code file before the contents of the header file. It does *not*
289 * insert it into the header file. This is a good place to put
290 * #include's that you want at the top of your code file. A common
291 * example is `#include "system.h"'. */
292 }
293 %start-header {
294 /* Bison inserts this block into both the header file and the code file.
295 * In both files, the point of insertion is before any Bison-generated
296 * token, semantic type, location type, and class definitions. This is a
297 * good place to define %union dependencies, for example. */
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298 }
299 %union {
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300 /* Unlike the traditional Yacc prologue blocks, the output order for the
301 * new %*-header blocks is not affected by their declaration position
302 * relative to any %union in the grammar file. */
9bc0dd67 303 }
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304 %end-header {
305 /* Bison inserts this block into both the header file and the code file.
306 * In both files, the point of insertion is after the Bison-generated
307 * definitions. This is a good place to declare or define public
308 * functions or data structures that depend on the Bison-generated
309 * definitions. */
9bc0dd67 310 }
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311 %after-header {
312 /* Bison treats this block like a post-prologue block: it inserts it into
313 * the code file after the contents of the header file. It does *not*
314 * insert it into the header file. This is a good place to declare or
315 * define internal functions or data structures that depend on the
316 * Bison-generated definitions. */
317 }
318
319 If you have multiple occurrences of any one of the above declarations, Bison
320 will concatenate the contents in declaration order.
9bc0dd67 321
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322 [Although we failed to mention this here in the 2.3a release, the prologue
323 alternatives were experimental, and they were rewritten in future versions.]
324
402b123d 325** The option `--report=look-ahead' has been changed to `--report=lookahead'.
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326 The old spelling still works, but is not documented and may be removed
327 in a future release.
742e4900 328
402b123d 329* Changes in version 2.3, 2006-06-05:
4ad3ed84 330
402b123d 331** GLR grammars should now use `YYRECOVERING ()' instead of `YYRECOVERING',
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332 for compatibility with LALR(1) grammars.
333
402b123d 334** It is now documented that any definition of YYSTYPE or YYLTYPE should
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335 be to a type name that does not contain parentheses or brackets.
336
402b123d 337* Changes in version 2.2, 2006-05-19:
193d7c70 338
402b123d 339** The distribution terms for all Bison-generated parsers now permit
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340 using the parsers in nonfree programs. Previously, this permission
341 was granted only for Bison-generated LALR(1) parsers in C.
5f4236a0 342
402b123d 343** %name-prefix changes the namespace name in C++ outputs.
aa08666d 344
402b123d 345** The C++ parsers export their token_type.
5f4236a0 346
402b123d 347** Bison now allows multiple %union declarations, and concatenates
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348 their contents together.
349
402b123d 350** New warning: unused values
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351 Right-hand side symbols whose values are not used are reported,
352 if the symbols have destructors. For instance:
affac613 353
8f3596a6 354 exp: exp "?" exp ":" exp { $1 ? $1 : $3; }
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355 | exp "+" exp
356 ;
affac613 357
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358 will trigger a warning about $$ and $5 in the first rule, and $3 in
359 the second ($1 is copied to $$ by the default rule). This example
4e26c69e 360 most likely contains three errors, and could be rewritten as:
affac613 361
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362 exp: exp "?" exp ":" exp
363 { $$ = $1 ? $3 : $5; free ($1 ? $5 : $3); free ($1); }
364 | exp "+" exp
365 { $$ = $1 ? $1 : $3; if ($1) free ($3); }
721be13c 366 ;
affac613 367
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368 However, if the original actions were really intended, memory leaks
369 and all, the warnings can be suppressed by letting Bison believe the
370 values are used, e.g.:
721be13c 371
8f3596a6 372 exp: exp "?" exp ":" exp { $1 ? $1 : $3; (void) ($$, $5); }
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373 | exp "+" exp { $$ = $1; (void) $3; }
374 ;
375
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376 If there are mid-rule actions, the warning is issued if no action
377 uses it. The following triggers no warning: $1 and $3 are used.
378
379 exp: exp { push ($1); } '+' exp { push ($3); sum (); };
380
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381 The warning is intended to help catching lost values and memory leaks.
382 If a value is ignored, its associated memory typically is not reclaimed.
affac613 383
402b123d 384** %destructor vs. YYABORT, YYACCEPT, and YYERROR.
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385 Destructors are now called when user code invokes YYABORT, YYACCEPT,
386 and YYERROR, for all objects on the stack, other than objects
387 corresponding to the right-hand side of the current rule.
a85284cf 388
402b123d 389** %expect, %expect-rr
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390 Incorrect numbers of expected conflicts are now actual errors,
391 instead of warnings.
392
402b123d 393** GLR, YACC parsers.
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394 The %parse-params are available in the destructors (and the
395 experimental printers) as per the documentation.
4b367315 396
402b123d 397** Bison now warns if it finds a stray `$' or `@' in an action.
ad6a9b97 398
402b123d 399** %require "VERSION"
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400 This specifies that the grammar file depends on features implemented
401 in Bison version VERSION or higher.
b50d2359 402
402b123d 403** lalr1.cc: The token and value types are now class members.
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404 The tokens were defined as free form enums and cpp macros. YYSTYPE
405 was defined as a free form union. They are now class members:
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406 tokens are enumerations of the `yy::parser::token' struct, and the
407 semantic values have the `yy::parser::semantic_type' type.
408
409 If you do not want or can update to this scheme, the directive
410 `%define "global_tokens_and_yystype" "1"' triggers the global
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411 definition of tokens and YYSTYPE. This change is suitable both
412 for previous releases of Bison, and this one.
fb9712a9 413
b50d2359 414 If you wish to update, then make sure older version of Bison will
ab8d9dc5 415 fail using `%require "2.2"'.
fb9712a9 416
402b123d 417** DJGPP support added.
193d7c70 418\f
402b123d 419* Changes in version 2.1, 2005-09-16:
1ce59070 420
402b123d 421** The C++ lalr1.cc skeleton supports %lex-param.
e14d0ab6 422
402b123d 423** Bison-generated parsers now support the translation of diagnostics like
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424 "syntax error" into languages other than English. The default
425 language is still English. For details, please see the new
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426 Internationalization section of the Bison manual. Software
427 distributors should also see the new PACKAGING file. Thanks to
428 Bruno Haible for this new feature.
1ce59070 429
402b123d 430** Wording in the Bison-generated parsers has been changed slightly to
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431 simplify translation. In particular, the message "memory exhausted"
432 has replaced "parser stack overflow", as the old message was not
433 always accurate for modern Bison-generated parsers.
434
402b123d 435** Destructors are now called when the parser aborts, for all symbols left
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436 behind on the stack. Also, the start symbol is now destroyed after a
437 successful parse. In both cases, the behavior was formerly inconsistent.
438
402b123d 439** When generating verbose diagnostics, Bison-generated parsers no longer
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440 quote the literal strings associated with tokens. For example, for
441 a syntax error associated with '%token NUM "number"' they might
442 print 'syntax error, unexpected number' instead of 'syntax error,
443 unexpected "number"'.
193d7c70 444\f
402b123d 445* Changes in version 2.0, 2004-12-25:
efeed023 446
402b123d 447** Possibly-incompatible changes
d7e14fc0 448
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449 - Bison-generated parsers no longer default to using the alloca function
450 (when available) to extend the parser stack, due to widespread
451 problems in unchecked stack-overflow detection. You can "#define
452 YYSTACK_USE_ALLOCA 1" to require the use of alloca, but please read
453 the manual to determine safe values for YYMAXDEPTH in that case.
8dd162d3 454
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455 - Error token location.
456 During error recovery, the location of the syntax error is updated
457 to cover the whole sequence covered by the error token: it includes
458 the shifted symbols thrown away during the first part of the error
459 recovery, and the lookahead rejected during the second part.
18d192f0 460
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461 - Semicolon changes:
462 . Stray semicolons are no longer allowed at the start of a grammar.
463 . Semicolons are now required after in-grammar declarations.
e342c3be 464
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465 - Unescaped newlines are no longer allowed in character constants or
466 string literals. They were never portable, and GCC 3.4.0 has
467 dropped support for them. Better diagnostics are now generated if
468 forget a closing quote.
8dd162d3 469
82de6b0d 470 - NUL bytes are no longer allowed in Bison string literals, unfortunately.
f74b6f91 471
402b123d 472** New features
1452af69 473
82de6b0d 474 - GLR grammars now support locations.
4febdd96 475
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476 - New directive: %initial-action.
477 This directive allows the user to run arbitrary code (including
478 initializing @$) from yyparse before parsing starts.
1452af69 479
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480 - A new directive "%expect-rr N" specifies the expected number of
481 reduce/reduce conflicts in GLR parsers.
1452af69 482
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483 - %token numbers can now be hexadecimal integers, e.g., `%token FOO 0x12d'.
484 This is a GNU extension.
4febdd96 485
82de6b0d 486 - The option `--report=lookahead' was changed to `--report=look-ahead'.
9e6e7ed2 487 [However, this was changed back after 2.3.]
1452af69 488
82de6b0d 489 - Experimental %destructor support has been added to lalr1.cc.
1452af69 490
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491 - New configure option --disable-yacc, to disable installation of the
492 yacc command and -ly library introduced in 1.875 for POSIX conformance.
6040d338 493
402b123d 494** Bug fixes
d5a3fe37 495
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496 - For now, %expect-count violations are now just warnings, not errors.
497 This is for compatibility with Bison 1.75 and earlier (when there are
498 reduce/reduce conflicts) and with Bison 1.30 and earlier (when there
499 are too many or too few shift/reduce conflicts). However, in future
500 versions of Bison we plan to improve the %expect machinery so that
501 these violations will become errors again.
3473d0f8 502
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503 - Within Bison itself, numbers (e.g., goto numbers) are no longer
504 arbitrarily limited to 16-bit counts.
d600ee67 505
82de6b0d 506 - Semicolons are now allowed before "|" in grammar rules, as POSIX requires.
d600ee67 507\f
402b123d 508* Changes in version 1.875, 2003-01-01:
963fcc17 509
402b123d 510** The documentation license has been upgraded to version 1.2
dc546b0f 511 of the GNU Free Documentation License.
75eb3bc4 512
402b123d 513** syntax error processing
75eb3bc4 514
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515 - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error
516 locations too. This fixes bugs in error-location computation.
75eb3bc4 517
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518 - %destructor
519 It is now possible to reclaim the memory associated to symbols
520 discarded during error recovery. This feature is still experimental.
20daca06 521
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522 - %error-verbose
523 This new directive is preferred over YYERROR_VERBOSE.
74724a70 524
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525 - #defining yyerror to steal internal variables is discouraged.
526 It is not guaranteed to work forever.
d1de5372 527
402b123d 528** POSIX conformance
d1de5372 529
dc546b0f
PE
530 - Semicolons are once again optional at the end of grammar rules.
531 This reverts to the behavior of Bison 1.33 and earlier, and improves
532 compatibility with Yacc.
74724a70 533
dc546b0f
PE
534 - `parse error' -> `syntax error'
535 Bison now uniformly uses the term `syntax error'; formerly, the code
536 and manual sometimes used the term `parse error' instead. POSIX
537 requires `syntax error' in diagnostics, and it was thought better to
538 be consistent.
74724a70 539
dc546b0f
PE
540 - The documentation now emphasizes that yylex and yyerror must be
541 declared before use. C99 requires this.
d1de5372 542
dc546b0f
PE
543 - Bison now parses C99 lexical constructs like UCNs and
544 backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires.
d1de5372 545
dc546b0f
PE
546 - File names are properly escaped in C output. E.g., foo\bar.y is
547 output as "foo\\bar.y".
6780ca7a 548
dc546b0f
PE
549 - Yacc command and library now available
550 The Bison distribution now installs a `yacc' command, as POSIX requires.
551 Also, Bison now installs a small library liby.a containing
552 implementations of Yacc-compatible yyerror and main functions.
553 This library is normally not useful, but POSIX requires it.
6e649e65 554
dc546b0f 555 - Type clashes now generate warnings, not errors.
6e649e65 556
dc546b0f
PE
557 - If the user does not define YYSTYPE as a macro, Bison now declares it
558 using typedef instead of defining it as a macro.
559 For consistency, YYLTYPE is also declared instead of defined.
9501dc6e 560
402b123d 561** Other compatibility issues
886a425c 562
dc546b0f
PE
563 - %union directives can now have a tag before the `{', e.g., the
564 directive `%union foo {...}' now generates the C code
565 `typedef union foo { ... } YYSTYPE;'; this is for Yacc compatibility.
566 The default union tag is `YYSTYPE', for compatibility with Solaris 9 Yacc.
567 For consistency, YYLTYPE's struct tag is now `YYLTYPE' not `yyltype'.
568 This is for compatibility with both Yacc and Bison 1.35.
72f889cc 569
dc546b0f
PE
570 - `;' is output before the terminating `}' of an action, for
571 compatibility with Bison 1.35.
886a425c 572
dc546b0f
PE
573 - Bison now uses a Yacc-style format for conflict reports, e.g.,
574 `conflicts: 2 shift/reduce, 1 reduce/reduce'.
437c2d80 575
dc546b0f
PE
576 - `yystype' and `yyltype' are now obsolescent macros instead of being
577 typedefs or tags; they are no longer documented and are planned to be
578 withdrawn in a future release.
2a8d363a 579
402b123d 580** GLR parser notes
2a8d363a 581
dc546b0f
PE
582 - GLR and inline
583 Users of Bison have to decide how they handle the portability of the
584 C keyword `inline'.
959e5f51 585
dc546b0f
PE
586 - `parsing stack overflow...' -> `parser stack overflow'
587 GLR parsers now report `parser stack overflow' as per the Bison manual.
900c5db5 588
402b123d 589** Bison now warns if it detects conflicting outputs to the same file,
dc546b0f
PE
590 e.g., it generates a warning for `bison -d -o foo.h foo.y' since
591 that command outputs both code and header to foo.h.
6e40b4eb 592
402b123d 593** #line in output files
dc546b0f 594 - --no-line works properly.
6e40b4eb 595
402b123d 596** Bison can no longer be built by a K&R C compiler; it requires C89 or
6e40b4eb
AD
597 later to be built. This change originally took place a few versions
598 ago, but nobody noticed until we recently asked someone to try
599 building Bison with a K&R C compiler.
d600ee67 600\f
402b123d 601* Changes in version 1.75, 2002-10-14:
7933f2b5 602
402b123d 603** Bison should now work on 64-bit hosts.
7933f2b5 604
402b123d 605** Indonesian translation thanks to Tedi Heriyanto.
7933f2b5 606
402b123d 607** GLR parsers
f50adbbd
AD
608 Fix spurious parse errors.
609
402b123d 610** Pure parsers
f50adbbd
AD
611 Some people redefine yyerror to steal yyparse' private variables.
612 Reenable this trick until an official feature replaces it.
613
402b123d 614** Type Clashes
d90c934c
AD
615 In agreement with POSIX and with other Yaccs, leaving a default
616 action is valid when $$ is untyped, and $1 typed:
617
618 untyped: ... typed;
619
620 but the converse remains an error:
621
622 typed: ... untyped;
623
402b123d 624** Values of mid-rule actions
d90c934c
AD
625 The following code:
626
627 foo: { ... } { $$ = $1; } ...
628
629 was incorrectly rejected: $1 is defined in the second mid-rule
630 action, and is equal to the $$ of the first mid-rule action.
d600ee67 631\f
402b123d 632* Changes in version 1.50, 2002-10-04:
adc8c848 633
402b123d 634** GLR parsing
676385e2
PH
635 The declaration
636 %glr-parser
637 causes Bison to produce a Generalized LR (GLR) parser, capable of handling
638 almost any context-free grammar, ambiguous or not. The new declarations
e8832397 639 %dprec and %merge on grammar rules allow parse-time resolution of
676385e2
PH
640 ambiguities. Contributed by Paul Hilfinger.
641
7933f2b5 642 Unfortunately Bison 1.50 does not work properly on 64-bit hosts
420f93c8
PE
643 like the Alpha, so please stick to 32-bit hosts for now.
644
402b123d 645** Output Directory
8c165d89 646 When not in Yacc compatibility mode, when the output file was not
e88dbdbf 647 specified, running `bison foo/bar.y' created `foo/bar.c'. It
8c165d89
AD
648 now creates `bar.c'.
649
402b123d 650** Undefined token
007a50a4 651 The undefined token was systematically mapped to 2 which prevented
e88dbdbf 652 the use of 2 by the user. This is no longer the case.
007a50a4 653
402b123d 654** Unknown token numbers
e88dbdbf 655 If yylex returned an out of range value, yyparse could die. This is
007a50a4
AD
656 no longer the case.
657
402b123d 658** Error token
e88dbdbf 659 According to POSIX, the error token must be 256.
23c5a174
AD
660 Bison extends this requirement by making it a preference: *if* the
661 user specified that one of her tokens is numbered 256, then error
662 will be mapped onto another number.
663
402b123d 664** Verbose error messages
e88dbdbf 665 They no longer report `..., expecting error or...' for states where
217598da
AD
666 error recovery is possible.
667
402b123d 668** End token
217598da
AD
669 Defaults to `$end' instead of `$'.
670
402b123d 671** Error recovery now conforms to documentation and to POSIX
68cd8af3
PE
672 When a Bison-generated parser encounters a syntax error, it now pops
673 the stack until it finds a state that allows shifting the error
674 token. Formerly, it popped the stack until it found a state that
675 allowed some non-error action other than a default reduction on the
676 error token. The new behavior has long been the documented behavior,
677 and has long been required by POSIX. For more details, please see
337116ba
PE
678 Paul Eggert, "Reductions during Bison error handling" (2002-05-20)
679 <http://lists.gnu.org/archive/html/bug-bison/2002-05/msg00038.html>.
68cd8af3 680
402b123d 681** Traces
5504898e
AD
682 Popped tokens and nonterminals are now reported.
683
402b123d 684** Larger grammars
a861a339
PE
685 Larger grammars are now supported (larger token numbers, larger grammar
686 size (= sum of the LHS and RHS lengths), larger LALR tables).
687 Formerly, many of these numbers ran afoul of 16-bit limits;
688 now these limits are 32 bits on most hosts.
355e7c1c 689
402b123d 690** Explicit initial rule
643a5994
AD
691 Bison used to play hacks with the initial rule, which the user does
692 not write. It is now explicit, and visible in the reports and
693 graphs as rule 0.
23c5a174 694
402b123d 695** Useless rules
643a5994 696 Before, Bison reported the useless rules, but, although not used,
77714df2 697 included them in the parsers. They are now actually removed.
23c5a174 698
402b123d 699** Useless rules, useless nonterminals
6b98e4b5
AD
700 They are now reported, as a warning, with their locations.
701
402b123d 702** Rules never reduced
e8832397
AD
703 Rules that can never be reduced because of conflicts are now
704 reported.
705
402b123d 706** Incorrect `Token not used'
11652ab3
AD
707 On a grammar such as
708
709 %token useless useful
710 %%
711 exp: '0' %prec useful;
712
713 where a token was used to set the precedence of the last rule,
714 bison reported both `useful' and `useless' as useless tokens.
715
402b123d 716** Revert the C++ namespace changes introduced in 1.31
77714df2 717 as they caused too many portability hassles.
0179dd65 718
402b123d 719** Default locations
b2d52318
AD
720 By an accident of design, the default computation of @$ was
721 performed after another default computation was performed: @$ = @1.
722 The latter is now removed: YYLLOC_DEFAULT is fully responsible of
723 the computation of @$.
adc8c848 724
402b123d 725** Token end-of-file
b7c49edf
AD
726 The token end of file may be specified by the user, in which case,
727 the user symbol is used in the reports, the graphs, and the verbose
a861a339 728 error messages instead of `$end', which remains being the default.
b7c49edf 729 For instance
7bd6c77e 730 %token MYEOF 0
b7c49edf 731 or
7bd6c77e 732 %token MYEOF 0 "end of file"
fdbcd8e2 733
402b123d 734** Semantic parser
fdbcd8e2
AD
735 This old option, which has been broken for ages, is removed.
736
402b123d 737** New translations
a861a339 738 Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
84614e13
AD
739 Croatian, thanks to Denis Lackovic.
740
402b123d 741** Incorrect token definitions
e88dbdbf 742 When given `%token 'a' "A"', Bison used to output `#define 'a' 65'.
b87f8b21 743
402b123d 744** Token definitions as enums
77714df2
AD
745 Tokens are output both as the traditional #define's, and, provided
746 the compiler supports ANSI C or is a C++ compiler, as enums.
e88dbdbf 747 This lets debuggers display names instead of integers.
77714df2 748
402b123d 749** Reports
ec3bc396
AD
750 In addition to --verbose, bison supports --report=THINGS, which
751 produces additional information:
b408954b
AD
752 - itemset
753 complete the core item sets with their closure
9e6e7ed2
PE
754 - lookahead [changed to `look-ahead' in 1.875e through 2.3, but changed back]
755 explicitly associate lookahead tokens to items
b408954b
AD
756 - solved
757 describe shift/reduce conflicts solving.
758 Bison used to systematically output this information on top of
759 the report. Solved conflicts are now attached to their states.
ec3bc396 760
402b123d 761** Type clashes
9af3fbce
AD
762 Previous versions don't complain when there is a type clash on
763 the default action if the rule has a mid-rule action, such as in:
764
765 %type <foo> bar
766 %%
767 bar: '0' {} '0';
768
769 This is fixed.
a861a339 770
402b123d 771** GNU M4 is now required when using Bison.
f987e9d2 772\f
402b123d 773* Changes in version 1.35, 2002-03-25:
76551463 774
402b123d 775** C Skeleton
76551463
AD
776 Some projects use Bison's C parser with C++ compilers, and define
777 YYSTYPE as a class. The recent adjustment of C parsers for data
778 alignment and 64 bit architectures made this impossible.
779
780 Because for the time being no real solution for C++ parser
781 generation exists, kludges were implemented in the parser to
782 maintain this use. In the future, when Bison has C++ parsers, this
783 kludge will be disabled.
784
785 This kludge also addresses some C++ problems when the stack was
786 extended.
76551463 787\f
402b123d 788* Changes in version 1.34, 2002-03-12:
76551463 789
402b123d 790** File name clashes are detected
76551463
AD
791 $ bison foo.y -d -o foo.x
792 fatal error: header and parser would both be named `foo.x'
793
402b123d 794** A missing `;' at the end of a rule triggers a warning
76551463
AD
795 In accordance with POSIX, and in agreement with other
796 Yacc implementations, Bison will mandate this semicolon in the near
797 future. This eases the implementation of a Bison parser of Bison
798 grammars by making this grammar LALR(1) instead of LR(2). To
799 facilitate the transition, this release introduces a warning.
800
402b123d 801** Revert the C++ namespace changes introduced in 1.31, as they caused too
76551463
AD
802 many portability hassles.
803
402b123d 804** DJGPP support added.
76551463 805
402b123d 806** Fix test suite portability problems.
76551463 807\f
402b123d 808* Changes in version 1.33, 2002-02-07:
76551463 809
402b123d 810** Fix C++ issues
76551463
AD
811 Groff could not be compiled for the definition of size_t was lacking
812 under some conditions.
813
402b123d 814** Catch invalid @n
76551463
AD
815 As is done with $n.
816\f
402b123d 817* Changes in version 1.32, 2002-01-23:
76551463 818
402b123d 819** Fix Yacc output file names
76551463 820
402b123d 821** Portability fixes
76551463 822
402b123d 823** Italian, Dutch translations
76551463 824\f
402b123d 825* Changes in version 1.31, 2002-01-14:
52d1aeee 826
402b123d 827** Many Bug Fixes
52d1aeee 828
402b123d 829** GNU Gettext and %expect
52d1aeee
MA
830 GNU Gettext asserts 10 s/r conflicts, but there are 7. Now that
831 Bison dies on incorrect %expectations, we fear there will be
832 too many bug reports for Gettext, so _for the time being_, %expect
833 does not trigger an error when the input file is named `plural.y'.
834
402b123d 835** Use of alloca in parsers
52d1aeee
MA
836 If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use
837 malloc exclusively. Since 1.29, but was not NEWS'ed.
838
839 alloca is used only when compiled with GCC, to avoid portability
840 problems as on AIX.
841
402b123d 842** yyparse now returns 2 if memory is exhausted; formerly it dumped core.
b47dbebe 843
402b123d 844** When the generated parser lacks debugging code, YYDEBUG is now 0
52d1aeee
MA
845 (as POSIX requires) instead of being undefined.
846
402b123d 847** User Actions
52d1aeee
MA
848 Bison has always permitted actions such as { $$ = $1 }: it adds the
849 ending semicolon. Now if in Yacc compatibility mode, the semicolon
850 is no longer output: one has to write { $$ = $1; }.
851
402b123d 852** Better C++ compliance
52d1aeee 853 The output parsers try to respect C++ namespaces.
76551463 854 [This turned out to be a failed experiment, and it was reverted later.]
52d1aeee 855
402b123d 856** Reduced Grammars
52d1aeee
MA
857 Fixed bugs when reporting useless nonterminals.
858
402b123d 859** 64 bit hosts
52d1aeee
MA
860 The parsers work properly on 64 bit hosts.
861
402b123d 862** Error messages
52d1aeee
MA
863 Some calls to strerror resulted in scrambled or missing error messages.
864
402b123d 865** %expect
52d1aeee
MA
866 When the number of shift/reduce conflicts is correct, don't issue
867 any warning.
868
402b123d 869** The verbose report includes the rule line numbers.
52d1aeee 870
402b123d 871** Rule line numbers are fixed in traces.
52d1aeee 872
402b123d 873** Swedish translation
52d1aeee 874
402b123d 875** Parse errors
52d1aeee
MA
876 Verbose parse error messages from the parsers are better looking.
877 Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'(''
878 Now: parse error: unexpected '/', expecting "number" or '-' or '('
879
402b123d 880** Fixed parser memory leaks.
52d1aeee
MA
881 When the generated parser was using malloc to extend its stacks, the
882 previous allocations were not freed.
883
402b123d 884** Fixed verbose output file.
52d1aeee
MA
885 Some newlines were missing.
886 Some conflicts in state descriptions were missing.
887
402b123d 888** Fixed conflict report.
52d1aeee
MA
889 Option -v was needed to get the result.
890
402b123d 891** %expect
52d1aeee
MA
892 Was not used.
893 Mismatches are errors, not warnings.
894
402b123d 895** Fixed incorrect processing of some invalid input.
52d1aeee 896
402b123d 897** Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H.
52d1aeee 898
402b123d 899** Fixed some typos in the documentation.
52d1aeee 900
402b123d 901** %token MY_EOF 0 is supported.
52d1aeee
MA
902 Before, MY_EOF was silently renumbered as 257.
903
402b123d 904** doc/refcard.tex is updated.
52d1aeee 905
402b123d 906** %output, %file-prefix, %name-prefix.
52d1aeee
MA
907 New.
908
402b123d 909** --output
52d1aeee
MA
910 New, aliasing `--output-file'.
911\f
402b123d 912* Changes in version 1.30, 2001-10-26:
342b8b6e 913
402b123d 914** `--defines' and `--graph' have now an optional argument which is the
fdac0091 915 output file name. `-d' and `-g' do not change; they do not take any
342b8b6e
AD
916 argument.
917
402b123d 918** `%source_extension' and `%header_extension' are removed, failed
342b8b6e
AD
919 experiment.
920
402b123d 921** Portability fixes.
f987e9d2 922\f
402b123d 923* Changes in version 1.29, 2001-09-07:
342b8b6e 924
402b123d 925** The output file does not define const, as this caused problems when used
342b8b6e
AD
926 with common autoconfiguration schemes. If you still use ancient compilers
927 that lack const, compile with the equivalent of the C compiler option
928 `-Dconst='. autoconf's AC_C_CONST macro provides one way to do this.
929
402b123d 930** Added `-g' and `--graph'.
f87a2205 931
402b123d 932** The Bison manual is now distributed under the terms of the GNU FDL.
f2b5126e 933
402b123d 934** The input and the output files has automatically a similar extension.
234a3be3 935
402b123d 936** Russian translation added.
f87a2205 937
402b123d 938** NLS support updated; should hopefully be less troublesome.
f87a2205 939
402b123d 940** Added the old Bison reference card.
c33638bb 941
402b123d 942** Added `--locations' and `%locations'.
6deb4447 943
402b123d 944** Added `-S' and `--skeleton'.
cd5bd6ac 945
402b123d 946** `%raw', `-r', `--raw' is disabled.
62ab6972 947
402b123d 948** Special characters are escaped when output. This solves the problems
cd5bd6ac
AD
949 of the #line lines with path names including backslashes.
950
402b123d 951** New directives.
4ecbf796
MA
952 `%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose',
953 `%debug', `%source_extension' and `%header_extension'.
f987e9d2 954
402b123d 955** @$
f987e9d2 956 Automatic location tracking.
f87a2205 957\f
402b123d 958* Changes in version 1.28, 1999-07-06:
d2e00347 959
402b123d 960** Should compile better now with K&R compilers.
d2e00347 961
402b123d 962** Added NLS.
d2e00347 963
402b123d 964** Fixed a problem with escaping the double quote character.
d2e00347 965
402b123d 966** There is now a FAQ.
d2e00347 967\f
402b123d 968* Changes in version 1.27:
5c31c3c2 969
402b123d 970** The make rule which prevented bison.simple from being created on
5c31c3c2
JT
971 some systems has been fixed.
972\f
402b123d 973* Changes in version 1.26:
4be07551 974
402b123d 975** Bison now uses automake.
4be07551 976
402b123d 977** New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
4be07551 978
402b123d 979** Token numbers now start at 257 as previously documented, not 258.
4be07551 980
402b123d 981** Bison honors the TMPDIR environment variable.
4be07551 982
402b123d 983** A couple of buffer overruns have been fixed.
f51dbca1 984
402b123d 985** Problems when closing files should now be reported.
f51dbca1 986
402b123d 987** Generated parsers should now work even on operating systems which do
f51dbca1 988 not provide alloca().
4be07551 989\f
402b123d 990* Changes in version 1.25, 1995-10-16:
df8878c5 991
402b123d 992** Errors in the input grammar are not fatal; Bison keeps reading
df8878c5 993the grammar file, and reports all the errors found in it.
8c44d3ec 994
402b123d 995** Tokens can now be specified as multiple-character strings: for
df8878c5
RS
996example, you could use "<=" for a token which looks like <=, instead
997of chosing a name like LESSEQ.
998
402b123d 999** The %token_table declaration says to write a table of tokens (names
df8878c5
RS
1000and numbers) into the parser file. The yylex function can use this
1001table to recognize multiple-character string tokens, or for other
1002purposes.
1003
402b123d 1004** The %no_lines declaration says not to generate any #line preprocessor
df8878c5
RS
1005directives in the parser file.
1006
402b123d 1007** The %raw declaration says to use internal Bison token numbers, not
df8878c5
RS
1008Yacc-compatible token numbers, when token names are defined as macros.
1009
402b123d 1010** The --no-parser option produces the parser tables without including
df8878c5
RS
1011the parser engine; a project can now use its own parser engine.
1012The actions go into a separate file called NAME.act, in the form of
1013a switch statement body.
1014\f
402b123d 1015* Changes in version 1.23:
6780ca7a 1016
4d019228
DM
1017The user can define YYPARSE_PARAM as the name of an argument to be
1018passed into yyparse. The argument should have type void *. It should
1019actually point to an object. Grammar actions can access the variable
1020by casting it to the proper pointer type.
6780ca7a 1021
6780ca7a 1022Line numbers in output file corrected.
6780ca7a 1023\f
402b123d 1024* Changes in version 1.22:
6780ca7a
DM
1025
1026--help option added.
6780ca7a 1027\f
402b123d 1028* Changes in version 1.20:
6780ca7a
DM
1029
1030Output file does not redefine const for C++.
9f4503d6
AD
1031
1032Local Variables:
1033mode: outline
1034End:
76551463
AD
1035
1036-----
1037
d6ca7905 1038Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
74553c98 10392004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
76551463 1040
74553c98 1041This file is part of Bison, the GNU Parser Generator.
76551463 1042
f16b0819 1043This program is free software: you can redistribute it and/or modify
76551463 1044it under the terms of the GNU General Public License as published by
f16b0819
PE
1045the Free Software Foundation, either version 3 of the License, or
1046(at your option) any later version.
76551463 1047
f16b0819 1048This program is distributed in the hope that it will be useful,
76551463
AD
1049but WITHOUT ANY WARRANTY; without even the implied warranty of
1050MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
1051GNU General Public License for more details.
1052
1053You should have received a copy of the GNU General Public License
f16b0819 1054along with this program. If not, see <http://www.gnu.org/licenses/>.