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* src/scan-skel.l (at_directive_perform): Fix switch statements for last patch.
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1Bison News
2----------
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4Changes in version 2.3a+ (????-??-??):
5
6* The -g and --graph options now output graphs in Graphviz DOT format,
7 not VCG format.
8
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9* An experimental directive %language specifies the language of the
10 generated parser, which can be C (the default) or C++. This
11 directive affects the skeleton used, and the names of the generated
12 files if the grammar file's name ends in ".y".
13
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14* The grammar file may now specify the name of the parser header file using
15 %defines. For example:
16
17 %defines "parser.h"
18
16dc6a9e 19* The `=' that used to be required in the following directives is now
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20 deprecated:
21
22 %file-prefix "parser"
23 %name-prefix "c_"
24 %output "parser.c"
25
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26* The quotes around NAME that used to be required in the following directive
27 are now deprecated:
28
29 %define NAME "VALUE"
30
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31* Bison 2.3a provided a new set of directives as a more flexible alternative to
32 the traditional Yacc prologue blocks. Those have now been consolidated into
33 a single %code directive with an optional qualifier field, which identifies
34 the purpose of the code and thus the location(s) where Bison should generate
35 it:
36
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37 1. `%code {CODE}' replaces `%after-header {CODE}'
38 2. `%code requires {CODE}' replaces `%start-header {CODE}'
39 3. `%code provides {CODE}' replaces `%end-header {CODE}'
40 4. `%code top {CODE}' replaces `%before-header {CODE}'
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41
42 See the %code entries in `Appendix A Bison Symbols' in the Bison manual for a
43 summary of the new functionality. See the new section `Prologue
44 Alternatives' for a detailed discussion including the advantages of %code
45 over the traditional Yacc prologues.
46
47 The prologue alternatives are experimental. More user feedback will help to
48 determine whether they should become permanent features.
49
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50* Revised warning: unset or unused mid-rule values
51
52 Since Bison 2.2, Bison has warned about mid-rule values that are set but not
53 used within any of the actions of the parent rule. For example, Bison warns
54 about unused $2 in:
55
56 exp: '1' { $$ = 1; } '+' exp { $$ = $1 + $4; };
57
58 Now, Bison also warns about mid-rule values that are used but not set. For
59 example, Bison warns about unset $$ in the mid-rule action in:
60
61 exp: '1' { $1 = 1; } '+' exp { $$ = $2 + $4; };
62
63 However, Bison now disables both of these warnings by default since they
64 sometimes prove to be false alarms in existing grammars employing the Yacc
65 constructs $0 or $-N (where N is some positive integer).
66
67 To enable these warnings, specify the flag `--warnings=midrule-values' or
68 `-W', which is a synonym for `--warnings=all'.
69
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70* Bison now recognizes two separate kinds of default %destructor's and
71 %printer's:
72
73 1. Place `<*>' in a %destructor/%printer symbol list to define a default
74 %destructor/%printer for all grammar symbols for which you have formally
75 declared semantic type tags.
76
3ebecc24 77 2. Place `<>' in a %destructor/%printer symbol list to define a default
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78 %destructor/%printer for all grammar symbols without declared semantic
79 type tags.
80
81 Bison no longer supports the `%symbol-default' notation from Bison 2.3a.
3ebecc24 82 `<*>' and `<>' combined achieve the same effect with one exception: Bison no
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83 longer applies any %destructor to a mid-rule value if that mid-rule value is
84 not actually ever referenced using either $$ or $n in a semantic action.
85
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86 The default %destructor's and %printer's are experimental. More user
87 feedback will help to determine whether they should become permanent
88 features.
89
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90 See the section `Freeing Discarded Symbols' in the Bison manual for further
91 details.
92
21fe08ca 93Changes in version 2.3a, 2006-09-13:
742e4900 94
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95* Instead of %union, you can define and use your own union type
96 YYSTYPE if your grammar contains at least one <type> tag.
97 Your YYSTYPE need not be a macro; it can be a typedef.
98 This change is for compatibility with other Yacc implementations,
99 and is required by POSIX.
100
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101* Locations columns and lines start at 1.
102 In accordance with the GNU Coding Standards and Emacs.
103
b2a0b7ca 104* You may now declare per-type and default %destructor's and %printer's:
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105
106 For example:
107
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108 %union { char *string; }
109 %token <string> STRING1
110 %token <string> STRING2
111 %type <string> string1
112 %type <string> string2
113 %union { char character; }
114 %token <character> CHR
115 %type <character> chr
116 %destructor { free ($$); } %symbol-default
117 %destructor { free ($$); printf ("%d", @$.first_line); } STRING1 string1
118 %destructor { } <character>
119
120 guarantees that, when the parser discards any user-defined symbol that has a
121 semantic type tag other than `<character>', it passes its semantic value to
122 `free'. However, when the parser discards a `STRING1' or a `string1', it
123 also prints its line number to `stdout'. It performs only the second
124 `%destructor' in this case, so it invokes `free' only once.
ec5479ce 125
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126 [Although we failed to mention this here in the 2.3a release, the default
127 %destructor's and %printer's were experimental, and they were rewritten in
128 future versions.]
129
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130* Except for LALR(1) parsers in C with POSIX Yacc emulation enabled (with `-y',
131 `--yacc', or `%yacc'), Bison no longer generates #define statements for
132 associating token numbers with token names. Removing the #define statements
133 helps to sanitize the global namespace during preprocessing, but POSIX Yacc
134 requires them. Bison still generates an enum for token names in all cases.
135
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136* Handling of traditional Yacc prologue blocks is now more consistent but
137 potentially incompatible with previous releases of Bison.
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138
139 As before, you declare prologue blocks in your grammar file with the
140 `%{ ... %}' syntax. To generate the pre-prologue, Bison concatenates all
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141 prologue blocks that you've declared before the first %union. To generate
142 the post-prologue, Bison concatenates all prologue blocks that you've
ddc8ede1 143 declared after the first %union.
9bc0dd67 144
34f98f46 145 Previous releases of Bison inserted the pre-prologue into both the header
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146 file and the code file in all cases except for LALR(1) parsers in C. In the
147 latter case, Bison inserted it only into the code file. For parsers in C++,
148 the point of insertion was before any token definitions (which associate
149 token numbers with names). For parsers in C, the point of insertion was
150 after the token definitions.
151
152 Now, Bison never inserts the pre-prologue into the header file. In the code
153 file, it always inserts it before the token definitions.
154
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155* Bison now provides a more flexible alternative to the traditional Yacc
156 prologue blocks: %before-header, %start-header, %end-header, and
157 %after-header.
158
159 For example, the following declaration order in the grammar file reflects the
160 order in which Bison will output these code blocks. However, you are free to
161 declare these code blocks in your grammar file in whatever order is most
162 convenient for you:
163
164 %before-header {
165 /* Bison treats this block like a pre-prologue block: it inserts it into
166 * the code file before the contents of the header file. It does *not*
167 * insert it into the header file. This is a good place to put
168 * #include's that you want at the top of your code file. A common
169 * example is `#include "system.h"'. */
170 }
171 %start-header {
172 /* Bison inserts this block into both the header file and the code file.
173 * In both files, the point of insertion is before any Bison-generated
174 * token, semantic type, location type, and class definitions. This is a
175 * good place to define %union dependencies, for example. */
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176 }
177 %union {
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178 /* Unlike the traditional Yacc prologue blocks, the output order for the
179 * new %*-header blocks is not affected by their declaration position
180 * relative to any %union in the grammar file. */
9bc0dd67 181 }
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182 %end-header {
183 /* Bison inserts this block into both the header file and the code file.
184 * In both files, the point of insertion is after the Bison-generated
185 * definitions. This is a good place to declare or define public
186 * functions or data structures that depend on the Bison-generated
187 * definitions. */
9bc0dd67 188 }
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189 %after-header {
190 /* Bison treats this block like a post-prologue block: it inserts it into
191 * the code file after the contents of the header file. It does *not*
192 * insert it into the header file. This is a good place to declare or
193 * define internal functions or data structures that depend on the
194 * Bison-generated definitions. */
195 }
196
197 If you have multiple occurrences of any one of the above declarations, Bison
198 will concatenate the contents in declaration order.
9bc0dd67 199
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200 [Although we failed to mention this here in the 2.3a release, the prologue
201 alternatives were experimental, and they were rewritten in future versions.]
202
742e4900 203* The option `--report=look-ahead' has been changed to `--report=lookahead'.
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204 The old spelling still works, but is not documented and may be removed
205 in a future release.
742e4900 206
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207Changes in version 2.3, 2006-06-05:
208
209* GLR grammars should now use `YYRECOVERING ()' instead of `YYRECOVERING',
210 for compatibility with LALR(1) grammars.
211
212* It is now documented that any definition of YYSTYPE or YYLTYPE should
213 be to a type name that does not contain parentheses or brackets.
214
ab8d9dc5 215Changes in version 2.2, 2006-05-19:
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216
217* The distribution terms for all Bison-generated parsers now permit
218 using the parsers in nonfree programs. Previously, this permission
219 was granted only for Bison-generated LALR(1) parsers in C.
5f4236a0 220
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221* %name-prefix changes the namespace name in C++ outputs.
222
223* The C++ parsers export their token_type.
5f4236a0 224
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225* Bison now allows multiple %union declarations, and concatenates
226 their contents together.
227
affac613 228* New warning: unused values
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229 Right-hand side symbols whose values are not used are reported,
230 if the symbols have destructors. For instance:
affac613 231
8f3596a6 232 exp: exp "?" exp ":" exp { $1 ? $1 : $3; }
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233 | exp "+" exp
234 ;
affac613 235
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236 will trigger a warning about $$ and $5 in the first rule, and $3 in
237 the second ($1 is copied to $$ by the default rule). This example
4e26c69e 238 most likely contains three errors, and could be rewritten as:
affac613 239
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240 exp: exp "?" exp ":" exp
241 { $$ = $1 ? $3 : $5; free ($1 ? $5 : $3); free ($1); }
242 | exp "+" exp
243 { $$ = $1 ? $1 : $3; if ($1) free ($3); }
721be13c 244 ;
affac613 245
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246 However, if the original actions were really intended, memory leaks
247 and all, the warnings can be suppressed by letting Bison believe the
248 values are used, e.g.:
721be13c 249
8f3596a6 250 exp: exp "?" exp ":" exp { $1 ? $1 : $3; (void) ($$, $5); }
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251 | exp "+" exp { $$ = $1; (void) $3; }
252 ;
253
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254 If there are mid-rule actions, the warning is issued if no action
255 uses it. The following triggers no warning: $1 and $3 are used.
256
257 exp: exp { push ($1); } '+' exp { push ($3); sum (); };
258
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259 The warning is intended to help catching lost values and memory leaks.
260 If a value is ignored, its associated memory typically is not reclaimed.
affac613 261
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262* %destructor vs. YYABORT, YYACCEPT, and YYERROR.
263 Destructors are now called when user code invokes YYABORT, YYACCEPT,
264 and YYERROR, for all objects on the stack, other than objects
265 corresponding to the right-hand side of the current rule.
a85284cf 266
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267* %expect, %expect-rr
268 Incorrect numbers of expected conflicts are now actual errors,
269 instead of warnings.
270
4b367315 271* GLR, YACC parsers.
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272 The %parse-params are available in the destructors (and the
273 experimental printers) as per the documentation.
4b367315 274
302c0aee 275* Bison now warns if it finds a stray `$' or `@' in an action.
ad6a9b97 276
b50d2359 277* %require "VERSION"
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278 This specifies that the grammar file depends on features implemented
279 in Bison version VERSION or higher.
b50d2359 280
fb9712a9 281* lalr1.cc: The token and value types are now class members.
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282 The tokens were defined as free form enums and cpp macros. YYSTYPE
283 was defined as a free form union. They are now class members:
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284 tokens are enumerations of the `yy::parser::token' struct, and the
285 semantic values have the `yy::parser::semantic_type' type.
286
287 If you do not want or can update to this scheme, the directive
288 `%define "global_tokens_and_yystype" "1"' triggers the global
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289 definition of tokens and YYSTYPE. This change is suitable both
290 for previous releases of Bison, and this one.
fb9712a9 291
b50d2359 292 If you wish to update, then make sure older version of Bison will
ab8d9dc5 293 fail using `%require "2.2"'.
fb9712a9 294
302c0aee 295* DJGPP support added.
193d7c70 296\f
1bd0deda 297Changes in version 2.1, 2005-09-16:
1ce59070 298
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299* The C++ lalr1.cc skeleton supports %lex-param.
300
a7db4add 301* Bison-generated parsers now support the translation of diagnostics like
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302 "syntax error" into languages other than English. The default
303 language is still English. For details, please see the new
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304 Internationalization section of the Bison manual. Software
305 distributors should also see the new PACKAGING file. Thanks to
306 Bruno Haible for this new feature.
1ce59070 307
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308* Wording in the Bison-generated parsers has been changed slightly to
309 simplify translation. In particular, the message "memory exhausted"
310 has replaced "parser stack overflow", as the old message was not
311 always accurate for modern Bison-generated parsers.
312
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313* Destructors are now called when the parser aborts, for all symbols left
314 behind on the stack. Also, the start symbol is now destroyed after a
315 successful parse. In both cases, the behavior was formerly inconsistent.
316
a7db4add 317* When generating verbose diagnostics, Bison-generated parsers no longer
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318 quote the literal strings associated with tokens. For example, for
319 a syntax error associated with '%token NUM "number"' they might
320 print 'syntax error, unexpected number' instead of 'syntax error,
321 unexpected "number"'.
193d7c70 322\f
82de6b0d 323Changes in version 2.0, 2004-12-25:
efeed023 324
82de6b0d 325* Possibly-incompatible changes
d7e14fc0 326
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327 - Bison-generated parsers no longer default to using the alloca function
328 (when available) to extend the parser stack, due to widespread
329 problems in unchecked stack-overflow detection. You can "#define
330 YYSTACK_USE_ALLOCA 1" to require the use of alloca, but please read
331 the manual to determine safe values for YYMAXDEPTH in that case.
8dd162d3 332
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333 - Error token location.
334 During error recovery, the location of the syntax error is updated
335 to cover the whole sequence covered by the error token: it includes
336 the shifted symbols thrown away during the first part of the error
337 recovery, and the lookahead rejected during the second part.
18d192f0 338
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339 - Semicolon changes:
340 . Stray semicolons are no longer allowed at the start of a grammar.
341 . Semicolons are now required after in-grammar declarations.
e342c3be 342
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343 - Unescaped newlines are no longer allowed in character constants or
344 string literals. They were never portable, and GCC 3.4.0 has
345 dropped support for them. Better diagnostics are now generated if
346 forget a closing quote.
8dd162d3 347
82de6b0d 348 - NUL bytes are no longer allowed in Bison string literals, unfortunately.
f74b6f91 349
82de6b0d 350* New features
1452af69 351
82de6b0d 352 - GLR grammars now support locations.
4febdd96 353
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354 - New directive: %initial-action.
355 This directive allows the user to run arbitrary code (including
356 initializing @$) from yyparse before parsing starts.
1452af69 357
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358 - A new directive "%expect-rr N" specifies the expected number of
359 reduce/reduce conflicts in GLR parsers.
1452af69 360
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361 - %token numbers can now be hexadecimal integers, e.g., `%token FOO 0x12d'.
362 This is a GNU extension.
4febdd96 363
82de6b0d 364 - The option `--report=lookahead' was changed to `--report=look-ahead'.
9e6e7ed2 365 [However, this was changed back after 2.3.]
1452af69 366
82de6b0d 367 - Experimental %destructor support has been added to lalr1.cc.
1452af69 368
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369 - New configure option --disable-yacc, to disable installation of the
370 yacc command and -ly library introduced in 1.875 for POSIX conformance.
6040d338 371
82de6b0d 372* Bug fixes
d5a3fe37 373
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374 - For now, %expect-count violations are now just warnings, not errors.
375 This is for compatibility with Bison 1.75 and earlier (when there are
376 reduce/reduce conflicts) and with Bison 1.30 and earlier (when there
377 are too many or too few shift/reduce conflicts). However, in future
378 versions of Bison we plan to improve the %expect machinery so that
379 these violations will become errors again.
3473d0f8 380
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381 - Within Bison itself, numbers (e.g., goto numbers) are no longer
382 arbitrarily limited to 16-bit counts.
d600ee67 383
82de6b0d 384 - Semicolons are now allowed before "|" in grammar rules, as POSIX requires.
d600ee67 385\f
dc546b0f 386Changes in version 1.875, 2003-01-01:
963fcc17 387
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388* The documentation license has been upgraded to version 1.2
389 of the GNU Free Documentation License.
75eb3bc4 390
dc546b0f 391* syntax error processing
75eb3bc4 392
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393 - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error
394 locations too. This fixes bugs in error-location computation.
75eb3bc4 395
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396 - %destructor
397 It is now possible to reclaim the memory associated to symbols
398 discarded during error recovery. This feature is still experimental.
20daca06 399
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400 - %error-verbose
401 This new directive is preferred over YYERROR_VERBOSE.
74724a70 402
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403 - #defining yyerror to steal internal variables is discouraged.
404 It is not guaranteed to work forever.
d1de5372 405
dc546b0f 406* POSIX conformance
d1de5372 407
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408 - Semicolons are once again optional at the end of grammar rules.
409 This reverts to the behavior of Bison 1.33 and earlier, and improves
410 compatibility with Yacc.
74724a70 411
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412 - `parse error' -> `syntax error'
413 Bison now uniformly uses the term `syntax error'; formerly, the code
414 and manual sometimes used the term `parse error' instead. POSIX
415 requires `syntax error' in diagnostics, and it was thought better to
416 be consistent.
74724a70 417
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418 - The documentation now emphasizes that yylex and yyerror must be
419 declared before use. C99 requires this.
d1de5372 420
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421 - Bison now parses C99 lexical constructs like UCNs and
422 backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires.
d1de5372 423
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424 - File names are properly escaped in C output. E.g., foo\bar.y is
425 output as "foo\\bar.y".
6780ca7a 426
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427 - Yacc command and library now available
428 The Bison distribution now installs a `yacc' command, as POSIX requires.
429 Also, Bison now installs a small library liby.a containing
430 implementations of Yacc-compatible yyerror and main functions.
431 This library is normally not useful, but POSIX requires it.
6e649e65 432
dc546b0f 433 - Type clashes now generate warnings, not errors.
6e649e65 434
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435 - If the user does not define YYSTYPE as a macro, Bison now declares it
436 using typedef instead of defining it as a macro.
437 For consistency, YYLTYPE is also declared instead of defined.
9501dc6e 438
dc546b0f 439* Other compatibility issues
886a425c 440
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441 - %union directives can now have a tag before the `{', e.g., the
442 directive `%union foo {...}' now generates the C code
443 `typedef union foo { ... } YYSTYPE;'; this is for Yacc compatibility.
444 The default union tag is `YYSTYPE', for compatibility with Solaris 9 Yacc.
445 For consistency, YYLTYPE's struct tag is now `YYLTYPE' not `yyltype'.
446 This is for compatibility with both Yacc and Bison 1.35.
72f889cc 447
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448 - `;' is output before the terminating `}' of an action, for
449 compatibility with Bison 1.35.
886a425c 450
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451 - Bison now uses a Yacc-style format for conflict reports, e.g.,
452 `conflicts: 2 shift/reduce, 1 reduce/reduce'.
437c2d80 453
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454 - `yystype' and `yyltype' are now obsolescent macros instead of being
455 typedefs or tags; they are no longer documented and are planned to be
456 withdrawn in a future release.
2a8d363a 457
dc546b0f 458* GLR parser notes
2a8d363a 459
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460 - GLR and inline
461 Users of Bison have to decide how they handle the portability of the
462 C keyword `inline'.
959e5f51 463
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464 - `parsing stack overflow...' -> `parser stack overflow'
465 GLR parsers now report `parser stack overflow' as per the Bison manual.
900c5db5 466
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467* Bison now warns if it detects conflicting outputs to the same file,
468 e.g., it generates a warning for `bison -d -o foo.h foo.y' since
469 that command outputs both code and header to foo.h.
6e40b4eb 470
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471* #line in output files
472 - --no-line works properly.
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473
474* Bison can no longer be built by a K&R C compiler; it requires C89 or
475 later to be built. This change originally took place a few versions
476 ago, but nobody noticed until we recently asked someone to try
477 building Bison with a K&R C compiler.
d600ee67 478\f
5c16c6b1 479Changes in version 1.75, 2002-10-14:
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480
481* Bison should now work on 64-bit hosts.
482
b7195100 483* Indonesian translation thanks to Tedi Heriyanto.
7933f2b5 484
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485* GLR parsers
486 Fix spurious parse errors.
487
488* Pure parsers
489 Some people redefine yyerror to steal yyparse' private variables.
490 Reenable this trick until an official feature replaces it.
491
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492* Type Clashes
493 In agreement with POSIX and with other Yaccs, leaving a default
494 action is valid when $$ is untyped, and $1 typed:
495
496 untyped: ... typed;
497
498 but the converse remains an error:
499
500 typed: ... untyped;
501
502* Values of mid-rule actions
503 The following code:
504
505 foo: { ... } { $$ = $1; } ...
506
507 was incorrectly rejected: $1 is defined in the second mid-rule
508 action, and is equal to the $$ of the first mid-rule action.
d600ee67 509\f
420f93c8 510Changes in version 1.50, 2002-10-04:
adc8c848 511
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512* GLR parsing
513 The declaration
514 %glr-parser
515 causes Bison to produce a Generalized LR (GLR) parser, capable of handling
516 almost any context-free grammar, ambiguous or not. The new declarations
e8832397 517 %dprec and %merge on grammar rules allow parse-time resolution of
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518 ambiguities. Contributed by Paul Hilfinger.
519
7933f2b5 520 Unfortunately Bison 1.50 does not work properly on 64-bit hosts
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521 like the Alpha, so please stick to 32-bit hosts for now.
522
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523* Output Directory
524 When not in Yacc compatibility mode, when the output file was not
e88dbdbf 525 specified, running `bison foo/bar.y' created `foo/bar.c'. It
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526 now creates `bar.c'.
527
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528* Undefined token
529 The undefined token was systematically mapped to 2 which prevented
e88dbdbf 530 the use of 2 by the user. This is no longer the case.
007a50a4 531
77714df2 532* Unknown token numbers
e88dbdbf 533 If yylex returned an out of range value, yyparse could die. This is
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534 no longer the case.
535
23c5a174 536* Error token
e88dbdbf 537 According to POSIX, the error token must be 256.
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538 Bison extends this requirement by making it a preference: *if* the
539 user specified that one of her tokens is numbered 256, then error
540 will be mapped onto another number.
541
217598da 542* Verbose error messages
e88dbdbf 543 They no longer report `..., expecting error or...' for states where
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544 error recovery is possible.
545
546* End token
547 Defaults to `$end' instead of `$'.
548
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549* Error recovery now conforms to documentation and to POSIX
550 When a Bison-generated parser encounters a syntax error, it now pops
551 the stack until it finds a state that allows shifting the error
552 token. Formerly, it popped the stack until it found a state that
553 allowed some non-error action other than a default reduction on the
554 error token. The new behavior has long been the documented behavior,
555 and has long been required by POSIX. For more details, please see
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556 Paul Eggert, "Reductions during Bison error handling" (2002-05-20)
557 <http://lists.gnu.org/archive/html/bug-bison/2002-05/msg00038.html>.
68cd8af3 558
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559* Traces
560 Popped tokens and nonterminals are now reported.
561
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562* Larger grammars
563 Larger grammars are now supported (larger token numbers, larger grammar
564 size (= sum of the LHS and RHS lengths), larger LALR tables).
565 Formerly, many of these numbers ran afoul of 16-bit limits;
566 now these limits are 32 bits on most hosts.
355e7c1c 567
77714df2 568* Explicit initial rule
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569 Bison used to play hacks with the initial rule, which the user does
570 not write. It is now explicit, and visible in the reports and
571 graphs as rule 0.
23c5a174 572
77714df2 573* Useless rules
643a5994 574 Before, Bison reported the useless rules, but, although not used,
77714df2 575 included them in the parsers. They are now actually removed.
23c5a174 576
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577* Useless rules, useless nonterminals
578 They are now reported, as a warning, with their locations.
579
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580* Rules never reduced
581 Rules that can never be reduced because of conflicts are now
582 reported.
583
77714df2 584* Incorrect `Token not used'
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585 On a grammar such as
586
587 %token useless useful
588 %%
589 exp: '0' %prec useful;
590
591 where a token was used to set the precedence of the last rule,
592 bison reported both `useful' and `useless' as useless tokens.
593
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594* Revert the C++ namespace changes introduced in 1.31
595 as they caused too many portability hassles.
0179dd65 596
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597* Default locations
598 By an accident of design, the default computation of @$ was
599 performed after another default computation was performed: @$ = @1.
600 The latter is now removed: YYLLOC_DEFAULT is fully responsible of
601 the computation of @$.
adc8c848 602
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603* Token end-of-file
604 The token end of file may be specified by the user, in which case,
605 the user symbol is used in the reports, the graphs, and the verbose
a861a339 606 error messages instead of `$end', which remains being the default.
b7c49edf 607 For instance
7bd6c77e 608 %token MYEOF 0
b7c49edf 609 or
7bd6c77e 610 %token MYEOF 0 "end of file"
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611
612* Semantic parser
613 This old option, which has been broken for ages, is removed.
614
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615* New translations
616 Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
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617 Croatian, thanks to Denis Lackovic.
618
77714df2 619* Incorrect token definitions
e88dbdbf 620 When given `%token 'a' "A"', Bison used to output `#define 'a' 65'.
b87f8b21 621
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622* Token definitions as enums
623 Tokens are output both as the traditional #define's, and, provided
624 the compiler supports ANSI C or is a C++ compiler, as enums.
e88dbdbf 625 This lets debuggers display names instead of integers.
77714df2 626
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627* Reports
628 In addition to --verbose, bison supports --report=THINGS, which
629 produces additional information:
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630 - itemset
631 complete the core item sets with their closure
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632 - lookahead [changed to `look-ahead' in 1.875e through 2.3, but changed back]
633 explicitly associate lookahead tokens to items
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634 - solved
635 describe shift/reduce conflicts solving.
636 Bison used to systematically output this information on top of
637 the report. Solved conflicts are now attached to their states.
ec3bc396 638
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639* Type clashes
640 Previous versions don't complain when there is a type clash on
641 the default action if the rule has a mid-rule action, such as in:
642
643 %type <foo> bar
644 %%
645 bar: '0' {} '0';
646
647 This is fixed.
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648
649* GNU M4 is now required when using Bison.
f987e9d2 650\f
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651Changes in version 1.35, 2002-03-25:
652
653* C Skeleton
654 Some projects use Bison's C parser with C++ compilers, and define
655 YYSTYPE as a class. The recent adjustment of C parsers for data
656 alignment and 64 bit architectures made this impossible.
657
658 Because for the time being no real solution for C++ parser
659 generation exists, kludges were implemented in the parser to
660 maintain this use. In the future, when Bison has C++ parsers, this
661 kludge will be disabled.
662
663 This kludge also addresses some C++ problems when the stack was
664 extended.
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665\f
666Changes in version 1.34, 2002-03-12:
667
668* File name clashes are detected
669 $ bison foo.y -d -o foo.x
670 fatal error: header and parser would both be named `foo.x'
671
672* A missing `;' at the end of a rule triggers a warning
673 In accordance with POSIX, and in agreement with other
674 Yacc implementations, Bison will mandate this semicolon in the near
675 future. This eases the implementation of a Bison parser of Bison
676 grammars by making this grammar LALR(1) instead of LR(2). To
677 facilitate the transition, this release introduces a warning.
678
679* Revert the C++ namespace changes introduced in 1.31, as they caused too
680 many portability hassles.
681
682* DJGPP support added.
683
684* Fix test suite portability problems.
685\f
686Changes in version 1.33, 2002-02-07:
687
688* Fix C++ issues
689 Groff could not be compiled for the definition of size_t was lacking
690 under some conditions.
691
692* Catch invalid @n
693 As is done with $n.
694\f
695Changes in version 1.32, 2002-01-23:
696
697* Fix Yacc output file names
698
699* Portability fixes
700
701* Italian, Dutch translations
702\f
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703Changes in version 1.31, 2002-01-14:
704
705* Many Bug Fixes
706
707* GNU Gettext and %expect
708 GNU Gettext asserts 10 s/r conflicts, but there are 7. Now that
709 Bison dies on incorrect %expectations, we fear there will be
710 too many bug reports for Gettext, so _for the time being_, %expect
711 does not trigger an error when the input file is named `plural.y'.
712
713* Use of alloca in parsers
714 If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use
715 malloc exclusively. Since 1.29, but was not NEWS'ed.
716
717 alloca is used only when compiled with GCC, to avoid portability
718 problems as on AIX.
719
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720* yyparse now returns 2 if memory is exhausted; formerly it dumped core.
721
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722* When the generated parser lacks debugging code, YYDEBUG is now 0
723 (as POSIX requires) instead of being undefined.
724
725* User Actions
726 Bison has always permitted actions such as { $$ = $1 }: it adds the
727 ending semicolon. Now if in Yacc compatibility mode, the semicolon
728 is no longer output: one has to write { $$ = $1; }.
729
730* Better C++ compliance
731 The output parsers try to respect C++ namespaces.
76551463 732 [This turned out to be a failed experiment, and it was reverted later.]
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733
734* Reduced Grammars
735 Fixed bugs when reporting useless nonterminals.
736
737* 64 bit hosts
738 The parsers work properly on 64 bit hosts.
739
740* Error messages
741 Some calls to strerror resulted in scrambled or missing error messages.
742
743* %expect
744 When the number of shift/reduce conflicts is correct, don't issue
745 any warning.
746
747* The verbose report includes the rule line numbers.
748
749* Rule line numbers are fixed in traces.
750
751* Swedish translation
752
753* Parse errors
754 Verbose parse error messages from the parsers are better looking.
755 Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'(''
756 Now: parse error: unexpected '/', expecting "number" or '-' or '('
757
758* Fixed parser memory leaks.
759 When the generated parser was using malloc to extend its stacks, the
760 previous allocations were not freed.
761
762* Fixed verbose output file.
763 Some newlines were missing.
764 Some conflicts in state descriptions were missing.
765
766* Fixed conflict report.
767 Option -v was needed to get the result.
768
769* %expect
770 Was not used.
771 Mismatches are errors, not warnings.
772
773* Fixed incorrect processing of some invalid input.
774
775* Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H.
776
777* Fixed some typos in the documentation.
778
779* %token MY_EOF 0 is supported.
780 Before, MY_EOF was silently renumbered as 257.
781
782* doc/refcard.tex is updated.
783
784* %output, %file-prefix, %name-prefix.
785 New.
786
787* --output
788 New, aliasing `--output-file'.
789\f
76551463 790Changes in version 1.30, 2001-10-26:
342b8b6e 791
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792* `--defines' and `--graph' have now an optional argument which is the
793 output file name. `-d' and `-g' do not change; they do not take any
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794 argument.
795
796* `%source_extension' and `%header_extension' are removed, failed
797 experiment.
798
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799* Portability fixes.
800\f
9f4503d6 801Changes in version 1.29, 2001-09-07:
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802
803* The output file does not define const, as this caused problems when used
804 with common autoconfiguration schemes. If you still use ancient compilers
805 that lack const, compile with the equivalent of the C compiler option
806 `-Dconst='. autoconf's AC_C_CONST macro provides one way to do this.
807
808* Added `-g' and `--graph'.
f87a2205 809
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810* The Bison manual is now distributed under the terms of the GNU FDL.
811
f1c63ced 812* The input and the output files has automatically a similar extension.
234a3be3 813
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814* Russian translation added.
815
816* NLS support updated; should hopefully be less troublesome.
817
818* Added the old Bison reference card.
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819
820* Added `--locations' and `%locations'.
6deb4447 821
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822* Added `-S' and `--skeleton'.
823
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824* `%raw', `-r', `--raw' is disabled.
825
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826* Special characters are escaped when output. This solves the problems
827 of the #line lines with path names including backslashes.
828
6deb4447 829* New directives.
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830 `%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose',
831 `%debug', `%source_extension' and `%header_extension'.
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832
833* @$
834 Automatic location tracking.
f87a2205 835\f
9f4503d6 836Changes in version 1.28, 1999-07-06:
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837
838* Should compile better now with K&R compilers.
839
840* Added NLS.
841
842* Fixed a problem with escaping the double quote character.
843
844* There is now a FAQ.
845\f
5c31c3c2
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846Changes in version 1.27:
847
848* The make rule which prevented bison.simple from being created on
849 some systems has been fixed.
850\f
851Changes in version 1.26:
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852
853* Bison now uses automake.
854
855* New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
856
857* Token numbers now start at 257 as previously documented, not 258.
858
859* Bison honors the TMPDIR environment variable.
860
861* A couple of buffer overruns have been fixed.
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862
863* Problems when closing files should now be reported.
864
865* Generated parsers should now work even on operating systems which do
866 not provide alloca().
4be07551 867\f
9f4503d6 868Changes in version 1.25, 1995-10-16:
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869
870* Errors in the input grammar are not fatal; Bison keeps reading
871the grammar file, and reports all the errors found in it.
8c44d3ec 872
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873* Tokens can now be specified as multiple-character strings: for
874example, you could use "<=" for a token which looks like <=, instead
875of chosing a name like LESSEQ.
876
877* The %token_table declaration says to write a table of tokens (names
878and numbers) into the parser file. The yylex function can use this
879table to recognize multiple-character string tokens, or for other
880purposes.
881
882* The %no_lines declaration says not to generate any #line preprocessor
883directives in the parser file.
884
885* The %raw declaration says to use internal Bison token numbers, not
886Yacc-compatible token numbers, when token names are defined as macros.
887
888* The --no-parser option produces the parser tables without including
889the parser engine; a project can now use its own parser engine.
890The actions go into a separate file called NAME.act, in the form of
891a switch statement body.
892\f
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893Changes in version 1.23:
894
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895The user can define YYPARSE_PARAM as the name of an argument to be
896passed into yyparse. The argument should have type void *. It should
897actually point to an object. Grammar actions can access the variable
898by casting it to the proper pointer type.
6780ca7a 899
6780ca7a 900Line numbers in output file corrected.
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901\f
902Changes in version 1.22:
903
904--help option added.
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905\f
906Changes in version 1.20:
907
908Output file does not redefine const for C++.
9f4503d6
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909
910Local Variables:
911mode: outline
912End:
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913
914-----
915
d6ca7905 916Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
279cabb6 9172004, 2005, 2006, 2007 Free Software Foundation, Inc.
76551463 918
75eb3bc4 919This file is part of Bison, the GNU Compiler Compiler.
76551463 920
75eb3bc4 921Bison is free software; you can redistribute it and/or modify
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922it under the terms of the GNU General Public License as published by
923the Free Software Foundation; either version 2, or (at your option)
924any later version.
925
75eb3bc4 926Bison is distributed in the hope that it will be useful,
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927but WITHOUT ANY WARRANTY; without even the implied warranty of
928MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
929GNU General Public License for more details.
930
931You should have received a copy of the GNU General Public License
932along with autoconf; see the file COPYING. If not, write to
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933the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
934Boston, MA 02110-1301, USA.