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1 | Bison News | |
2 | ---------- | |
3 | ||
4 | * Changes in version ?.? (????-??-??): | |
5 | ||
6 | ** Java skeleton improvements: | |
7 | ||
8 | The constants for token names were moved to the Lexer interface. | |
9 | Also, it is possible to add code to the parser's constructors using | |
10 | "%code init" and "%define init_throws". | |
11 | ||
12 | ** Variable api.tokens.prefix | |
13 | ||
14 | The variable api.tokens.prefix changes the way tokens are identified in | |
15 | the generated files. This is especially useful to avoid collisions | |
16 | with identifiers in the target language. For instance | |
17 | ||
18 | %token FILE for ERROR | |
19 | %define api.tokens.prefix "TOK_" | |
20 | %% | |
21 | start: FILE for ERROR; | |
22 | ||
23 | will generate the definition of the symbols TOK_FILE, TOK_for, and | |
24 | TOK_ERROR in the generated sources. In particular, the scanner must | |
25 | use these prefixed token names, although the grammar itself still | |
26 | uses the short names (as in the sample rule given above). | |
27 | ||
28 | ** Variable api.namespace | |
29 | ||
30 | The "namespace" variable is renamed "api.namespace". Backward | |
31 | compatibility is ensured, but upgrading is recommended. | |
32 | ||
33 | ** Variable parse.error | |
34 | ||
35 | The variable error controls the verbosity of error messages. The | |
36 | use of the %error-verbose directive is deprecated in favor of | |
37 | %define parse.error "verbose". | |
38 | ||
39 | * Changes in version 2.5 (????-??-??): | |
40 | ||
41 | ** IELR(1) and Canonical LR(1) Support | |
42 | ||
43 | IELR(1) is a minimal LR(1) parser table generation algorithm. That | |
44 | is, given any context-free grammar, IELR(1) generates parser tables | |
45 | with the full language recognition power of canonical LR(1) but with | |
46 | nearly the same number of parser states as LALR(1). This reduction in | |
47 | parser states is often an order of magnitude. More importantly, | |
48 | because canonical LR(1)'s extra parser states may contain duplicate | |
49 | conflicts in the case of non-LR(1) grammars, the number of conflicts | |
50 | for IELR(1) is often an order of magnitude less as well. This can | |
51 | significantly reduce the complexity of developing of a grammar. | |
52 | ||
53 | Bison can now generate IELR(1) and canonical LR(1) parser tables in | |
54 | place of its traditional LALR(1) parser tables, which remain the | |
55 | default. You can specify the type of parser tables in the grammar | |
56 | file with these directives: | |
57 | ||
58 | %define lr.type "LALR" | |
59 | %define lr.type "IELR" | |
60 | %define lr.type "canonical LR" | |
61 | ||
62 | The default reduction optimization in the parser tables can also be | |
63 | adjusted using `%define lr.default-reductions'. See the documentation | |
64 | for `%define lr.type' and `%define lr.default-reductions' in the | |
65 | section `Bison Declaration Summary' in the Bison manual for the | |
66 | details. | |
67 | ||
68 | These features are experimental. More user feedback will help to | |
69 | stabilize them. | |
70 | ||
71 | ** Multiple %define's for any variable is now an error not a warning. | |
72 | ||
73 | ** %define can now be invoked via the command line. | |
74 | ||
75 | Each of these command-line options | |
76 | ||
77 | -D NAME[=VALUE] | |
78 | --define=NAME[=VALUE] | |
79 | ||
80 | -F NAME[=VALUE] | |
81 | --force-define=NAME[=VALUE] | |
82 | ||
83 | is equivalent to this grammar file declaration | |
84 | ||
85 | %define NAME ["VALUE"] | |
86 | ||
87 | except that the manner in which Bison processes multiple definitions | |
88 | for the same NAME differs. Most importantly, -F and --force-define | |
89 | quietly override %define, but -D and --define do not. For further | |
90 | details, see the section "Bison Options" in the Bison manual. | |
91 | ||
92 | ** %define variables renamed. | |
93 | ||
94 | The following %define variables | |
95 | ||
96 | api.push_pull | |
97 | lr.keep_unreachable_states | |
98 | ||
99 | have been renamed to | |
100 | ||
101 | api.push-pull | |
102 | lr.keep-unreachable-states | |
103 | ||
104 | The old names are now deprecated but will be maintained indefinitely | |
105 | for backward compatibility. | |
106 | ||
107 | ** Symbols names | |
108 | ||
109 | Consistently with directives (such as %error-verbose) and variables | |
110 | (e.g. push-pull), symbol names may include dashes in any position, | |
111 | similarly to periods and underscores. This is GNU extension over | |
112 | POSIX Yacc whose use is reported by -Wyacc, and rejected in Yacc | |
113 | mode (--yacc). | |
114 | ||
115 | ** Temporary hack for adding a semicolon to the user action. | |
116 | ||
117 | Previously, Bison appended a semicolon to every user action for | |
118 | reductions when the output language defaulted to C (specifically, when | |
119 | neither %yacc, %language, %skeleton, or equivalent command-line | |
120 | options were specified). This allowed actions such as | |
121 | ||
122 | exp: exp "+" exp { $$ = $1 + $3 }; | |
123 | ||
124 | instead of | |
125 | ||
126 | exp: exp "+" exp { $$ = $1 + $3; }; | |
127 | ||
128 | As a first step in removing this misfeature, Bison now issues a | |
129 | warning when it appends a semicolon. Moreover, in cases where Bison | |
130 | cannot easily determine whether a semicolon is needed (for example, an | |
131 | action ending with a cpp directive or a braced compound initializer), | |
132 | it no longer appends one. Thus, the C compiler might now complain | |
133 | about a missing semicolon where it did not before. Future releases of | |
134 | Bison will cease to append semicolons entirely. | |
135 | ||
136 | ** Character literals not of length one. | |
137 | ||
138 | Previously, Bison quietly converted all character literals to length | |
139 | one. For example, without warning, Bison interpreted the operators in | |
140 | the following grammar to be the same token: | |
141 | ||
142 | exp: exp '++' | |
143 | | exp '+' exp | |
144 | ; | |
145 | ||
146 | Bison now warns when a character literal is not of length one. In | |
147 | some future release, Bison will report an error instead. | |
148 | ||
149 | ** Verbose error messages fixed for nonassociative tokens. | |
150 | ||
151 | When %error-verbose is specified, syntax error messages produced by | |
152 | the generated parser include the unexpected token as well as a list of | |
153 | expected tokens. Previously, this list erroneously included tokens | |
154 | that would actually induce a syntax error because conflicts for them | |
155 | were resolved with %nonassoc. Such tokens are now properly omitted | |
156 | from the list. | |
157 | ||
158 | * Changes in version 2.4.2 (????-??-??): | |
159 | ||
160 | ** Detection of GNU M4 1.4.6 or newer during configure is improved. | |
161 | ||
162 | ** %code is now a permanent feature. | |
163 | ||
164 | A traditional Yacc prologue directive is written in the form: | |
165 | ||
166 | %{CODE%} | |
167 | ||
168 | To provide a more flexible alternative, Bison 2.3b introduced the | |
169 | %code directive with the following forms for C/C++: | |
170 | ||
171 | %code {CODE} | |
172 | %code requires {CODE} | |
173 | %code provides {CODE} | |
174 | %code top {CODE} | |
175 | ||
176 | These forms are now considered permanent features of Bison. See the | |
177 | %code entries in the section "Bison Declaration Summary" in the Bison | |
178 | manual for a summary of their functionality. See the section | |
179 | "Prologue Alternatives" for a detailed discussion including the | |
180 | advantages of %code over the traditional Yacc prologue directive. | |
181 | ||
182 | Bison's Java feature as a whole including its current usage of %code | |
183 | is still considered experimental. | |
184 | ||
185 | * Changes in version 2.4.1 (2008-12-11): | |
186 | ||
187 | ** In the GLR defines file, unexpanded M4 macros in the yylval and yylloc | |
188 | declarations have been fixed. | |
189 | ||
190 | ** Temporary hack for adding a semicolon to the user action. | |
191 | ||
192 | Bison used to prepend a trailing semicolon at the end of the user | |
193 | action for reductions. This allowed actions such as | |
194 | ||
195 | exp: exp "+" exp { $$ = $1 + $3 }; | |
196 | ||
197 | instead of | |
198 | ||
199 | exp: exp "+" exp { $$ = $1 + $3; }; | |
200 | ||
201 | Some grammars still depend on this `feature'. Bison 2.4.1 restores | |
202 | the previous behavior in the case of C output (specifically, when | |
203 | neither %language or %skeleton or equivalent command-line options | |
204 | are used) to leave more time for grammars depending on the old | |
205 | behavior to be adjusted. Future releases of Bison will disable this | |
206 | feature. | |
207 | ||
208 | ** A few minor improvements to the Bison manual. | |
209 | ||
210 | * Changes in version 2.4 (2008-11-02): | |
211 | ||
212 | ** %language is an experimental feature. | |
213 | ||
214 | We first introduced this feature in test release 2.3b as a cleaner | |
215 | alternative to %skeleton. Since then, we have discussed the possibility of | |
216 | modifying its effect on Bison's output file names. Thus, in this release, | |
217 | we consider %language to be an experimental feature that will likely evolve | |
218 | in future releases. | |
219 | ||
220 | ** Forward compatibility with GNU M4 has been improved. | |
221 | ||
222 | ** Several bugs in the C++ skeleton and the experimental Java skeleton have been | |
223 | fixed. | |
224 | ||
225 | * Changes in version 2.3b (2008-05-27): | |
226 | ||
227 | ** The quotes around NAME that used to be required in the following directive | |
228 | are now deprecated: | |
229 | ||
230 | %define NAME "VALUE" | |
231 | ||
232 | ** The directive `%pure-parser' is now deprecated in favor of: | |
233 | ||
234 | %define api.pure | |
235 | ||
236 | which has the same effect except that Bison is more careful to warn about | |
237 | unreasonable usage in the latter case. | |
238 | ||
239 | ** Push Parsing | |
240 | ||
241 | Bison can now generate an LALR(1) parser in C with a push interface. That | |
242 | is, instead of invoking `yyparse', which pulls tokens from `yylex', you can | |
243 | push one token at a time to the parser using `yypush_parse', which will | |
244 | return to the caller after processing each token. By default, the push | |
245 | interface is disabled. Either of the following directives will enable it: | |
246 | ||
247 | %define api.push_pull "push" // Just push; does not require yylex. | |
248 | %define api.push_pull "both" // Push and pull; requires yylex. | |
249 | ||
250 | See the new section `A Push Parser' in the Bison manual for details. | |
251 | ||
252 | The current push parsing interface is experimental and may evolve. More user | |
253 | feedback will help to stabilize it. | |
254 | ||
255 | ** The -g and --graph options now output graphs in Graphviz DOT format, | |
256 | not VCG format. Like --graph, -g now also takes an optional FILE argument | |
257 | and thus cannot be bundled with other short options. | |
258 | ||
259 | ** Java | |
260 | ||
261 | Bison can now generate an LALR(1) parser in Java. The skeleton is | |
262 | `data/lalr1.java'. Consider using the new %language directive instead of | |
263 | %skeleton to select it. | |
264 | ||
265 | See the new section `Java Parsers' in the Bison manual for details. | |
266 | ||
267 | The current Java interface is experimental and may evolve. More user | |
268 | feedback will help to stabilize it. | |
269 | ||
270 | ** %language | |
271 | ||
272 | This new directive specifies the programming language of the generated | |
273 | parser, which can be C (the default), C++, or Java. Besides the skeleton | |
274 | that Bison uses, the directive affects the names of the generated files if | |
275 | the grammar file's name ends in ".y". | |
276 | ||
277 | ** XML Automaton Report | |
278 | ||
279 | Bison can now generate an XML report of the LALR(1) automaton using the new | |
280 | `--xml' option. The current XML schema is experimental and may evolve. More | |
281 | user feedback will help to stabilize it. | |
282 | ||
283 | ** The grammar file may now specify the name of the parser header file using | |
284 | %defines. For example: | |
285 | ||
286 | %defines "parser.h" | |
287 | ||
288 | ** When reporting useless rules, useless nonterminals, and unused terminals, | |
289 | Bison now employs the terms "useless in grammar" instead of "useless", | |
290 | "useless in parser" instead of "never reduced", and "unused in grammar" | |
291 | instead of "unused". | |
292 | ||
293 | ** Unreachable State Removal | |
294 | ||
295 | Previously, Bison sometimes generated parser tables containing unreachable | |
296 | states. A state can become unreachable during conflict resolution if Bison | |
297 | disables a shift action leading to it from a predecessor state. Bison now: | |
298 | ||
299 | 1. Removes unreachable states. | |
300 | ||
301 | 2. Does not report any conflicts that appeared in unreachable states. | |
302 | WARNING: As a result, you may need to update %expect and %expect-rr | |
303 | directives in existing grammar files. | |
304 | ||
305 | 3. For any rule used only in such states, Bison now reports the rule as | |
306 | "useless in parser due to conflicts". | |
307 | ||
308 | This feature can be disabled with the following directive: | |
309 | ||
310 | %define lr.keep_unreachable_states | |
311 | ||
312 | See the %define entry in the `Bison Declaration Summary' in the Bison manual | |
313 | for further discussion. | |
314 | ||
315 | ** Lookahead Set Correction in the `.output' Report | |
316 | ||
317 | When instructed to generate a `.output' file including lookahead sets | |
318 | (using `--report=lookahead', for example), Bison now prints each reduction's | |
319 | lookahead set only next to the associated state's one item that (1) is | |
320 | associated with the same rule as the reduction and (2) has its dot at the end | |
321 | of its RHS. Previously, Bison also erroneously printed the lookahead set | |
322 | next to all of the state's other items associated with the same rule. This | |
323 | bug affected only the `.output' file and not the generated parser source | |
324 | code. | |
325 | ||
326 | ** --report-file=FILE is a new option to override the default `.output' file | |
327 | name. | |
328 | ||
329 | ** The `=' that used to be required in the following directives is now | |
330 | deprecated: | |
331 | ||
332 | %file-prefix "parser" | |
333 | %name-prefix "c_" | |
334 | %output "parser.c" | |
335 | ||
336 | ** An Alternative to `%{...%}' -- `%code QUALIFIER {CODE}' | |
337 | ||
338 | Bison 2.3a provided a new set of directives as a more flexible alternative to | |
339 | the traditional Yacc prologue blocks. Those have now been consolidated into | |
340 | a single %code directive with an optional qualifier field, which identifies | |
341 | the purpose of the code and thus the location(s) where Bison should generate | |
342 | it: | |
343 | ||
344 | 1. `%code {CODE}' replaces `%after-header {CODE}' | |
345 | 2. `%code requires {CODE}' replaces `%start-header {CODE}' | |
346 | 3. `%code provides {CODE}' replaces `%end-header {CODE}' | |
347 | 4. `%code top {CODE}' replaces `%before-header {CODE}' | |
348 | ||
349 | See the %code entries in section `Bison Declaration Summary' in the Bison | |
350 | manual for a summary of the new functionality. See the new section `Prologue | |
351 | Alternatives' for a detailed discussion including the advantages of %code | |
352 | over the traditional Yacc prologues. | |
353 | ||
354 | The prologue alternatives are experimental. More user feedback will help to | |
355 | determine whether they should become permanent features. | |
356 | ||
357 | ** Revised warning: unset or unused mid-rule values | |
358 | ||
359 | Since Bison 2.2, Bison has warned about mid-rule values that are set but not | |
360 | used within any of the actions of the parent rule. For example, Bison warns | |
361 | about unused $2 in: | |
362 | ||
363 | exp: '1' { $$ = 1; } '+' exp { $$ = $1 + $4; }; | |
364 | ||
365 | Now, Bison also warns about mid-rule values that are used but not set. For | |
366 | example, Bison warns about unset $$ in the mid-rule action in: | |
367 | ||
368 | exp: '1' { $1 = 1; } '+' exp { $$ = $2 + $4; }; | |
369 | ||
370 | However, Bison now disables both of these warnings by default since they | |
371 | sometimes prove to be false alarms in existing grammars employing the Yacc | |
372 | constructs $0 or $-N (where N is some positive integer). | |
373 | ||
374 | To enable these warnings, specify the option `--warnings=midrule-values' or | |
375 | `-W', which is a synonym for `--warnings=all'. | |
376 | ||
377 | ** Default %destructor or %printer with `<*>' or `<>' | |
378 | ||
379 | Bison now recognizes two separate kinds of default %destructor's and | |
380 | %printer's: | |
381 | ||
382 | 1. Place `<*>' in a %destructor/%printer symbol list to define a default | |
383 | %destructor/%printer for all grammar symbols for which you have formally | |
384 | declared semantic type tags. | |
385 | ||
386 | 2. Place `<>' in a %destructor/%printer symbol list to define a default | |
387 | %destructor/%printer for all grammar symbols without declared semantic | |
388 | type tags. | |
389 | ||
390 | Bison no longer supports the `%symbol-default' notation from Bison 2.3a. | |
391 | `<*>' and `<>' combined achieve the same effect with one exception: Bison no | |
392 | longer applies any %destructor to a mid-rule value if that mid-rule value is | |
393 | not actually ever referenced using either $$ or $n in a semantic action. | |
394 | ||
395 | The default %destructor's and %printer's are experimental. More user | |
396 | feedback will help to determine whether they should become permanent | |
397 | features. | |
398 | ||
399 | See the section `Freeing Discarded Symbols' in the Bison manual for further | |
400 | details. | |
401 | ||
402 | ** %left, %right, and %nonassoc can now declare token numbers. This is required | |
403 | by POSIX. However, see the end of section `Operator Precedence' in the Bison | |
404 | manual for a caveat concerning the treatment of literal strings. | |
405 | ||
406 | ** The nonfunctional --no-parser, -n, and %no-parser options have been | |
407 | completely removed from Bison. | |
408 | ||
409 | * Changes in version 2.3a, 2006-09-13: | |
410 | ||
411 | ** Instead of %union, you can define and use your own union type | |
412 | YYSTYPE if your grammar contains at least one <type> tag. | |
413 | Your YYSTYPE need not be a macro; it can be a typedef. | |
414 | This change is for compatibility with other Yacc implementations, | |
415 | and is required by POSIX. | |
416 | ||
417 | ** Locations columns and lines start at 1. | |
418 | In accordance with the GNU Coding Standards and Emacs. | |
419 | ||
420 | ** You may now declare per-type and default %destructor's and %printer's: | |
421 | ||
422 | For example: | |
423 | ||
424 | %union { char *string; } | |
425 | %token <string> STRING1 | |
426 | %token <string> STRING2 | |
427 | %type <string> string1 | |
428 | %type <string> string2 | |
429 | %union { char character; } | |
430 | %token <character> CHR | |
431 | %type <character> chr | |
432 | %destructor { free ($$); } %symbol-default | |
433 | %destructor { free ($$); printf ("%d", @$.first_line); } STRING1 string1 | |
434 | %destructor { } <character> | |
435 | ||
436 | guarantees that, when the parser discards any user-defined symbol that has a | |
437 | semantic type tag other than `<character>', it passes its semantic value to | |
438 | `free'. However, when the parser discards a `STRING1' or a `string1', it | |
439 | also prints its line number to `stdout'. It performs only the second | |
440 | `%destructor' in this case, so it invokes `free' only once. | |
441 | ||
442 | [Although we failed to mention this here in the 2.3a release, the default | |
443 | %destructor's and %printer's were experimental, and they were rewritten in | |
444 | future versions.] | |
445 | ||
446 | ** Except for LALR(1) parsers in C with POSIX Yacc emulation enabled (with `-y', | |
447 | `--yacc', or `%yacc'), Bison no longer generates #define statements for | |
448 | associating token numbers with token names. Removing the #define statements | |
449 | helps to sanitize the global namespace during preprocessing, but POSIX Yacc | |
450 | requires them. Bison still generates an enum for token names in all cases. | |
451 | ||
452 | ** Handling of traditional Yacc prologue blocks is now more consistent but | |
453 | potentially incompatible with previous releases of Bison. | |
454 | ||
455 | As before, you declare prologue blocks in your grammar file with the | |
456 | `%{ ... %}' syntax. To generate the pre-prologue, Bison concatenates all | |
457 | prologue blocks that you've declared before the first %union. To generate | |
458 | the post-prologue, Bison concatenates all prologue blocks that you've | |
459 | declared after the first %union. | |
460 | ||
461 | Previous releases of Bison inserted the pre-prologue into both the header | |
462 | file and the code file in all cases except for LALR(1) parsers in C. In the | |
463 | latter case, Bison inserted it only into the code file. For parsers in C++, | |
464 | the point of insertion was before any token definitions (which associate | |
465 | token numbers with names). For parsers in C, the point of insertion was | |
466 | after the token definitions. | |
467 | ||
468 | Now, Bison never inserts the pre-prologue into the header file. In the code | |
469 | file, it always inserts it before the token definitions. | |
470 | ||
471 | ** Bison now provides a more flexible alternative to the traditional Yacc | |
472 | prologue blocks: %before-header, %start-header, %end-header, and | |
473 | %after-header. | |
474 | ||
475 | For example, the following declaration order in the grammar file reflects the | |
476 | order in which Bison will output these code blocks. However, you are free to | |
477 | declare these code blocks in your grammar file in whatever order is most | |
478 | convenient for you: | |
479 | ||
480 | %before-header { | |
481 | /* Bison treats this block like a pre-prologue block: it inserts it into | |
482 | * the code file before the contents of the header file. It does *not* | |
483 | * insert it into the header file. This is a good place to put | |
484 | * #include's that you want at the top of your code file. A common | |
485 | * example is `#include "system.h"'. */ | |
486 | } | |
487 | %start-header { | |
488 | /* Bison inserts this block into both the header file and the code file. | |
489 | * In both files, the point of insertion is before any Bison-generated | |
490 | * token, semantic type, location type, and class definitions. This is a | |
491 | * good place to define %union dependencies, for example. */ | |
492 | } | |
493 | %union { | |
494 | /* Unlike the traditional Yacc prologue blocks, the output order for the | |
495 | * new %*-header blocks is not affected by their declaration position | |
496 | * relative to any %union in the grammar file. */ | |
497 | } | |
498 | %end-header { | |
499 | /* Bison inserts this block into both the header file and the code file. | |
500 | * In both files, the point of insertion is after the Bison-generated | |
501 | * definitions. This is a good place to declare or define public | |
502 | * functions or data structures that depend on the Bison-generated | |
503 | * definitions. */ | |
504 | } | |
505 | %after-header { | |
506 | /* Bison treats this block like a post-prologue block: it inserts it into | |
507 | * the code file after the contents of the header file. It does *not* | |
508 | * insert it into the header file. This is a good place to declare or | |
509 | * define internal functions or data structures that depend on the | |
510 | * Bison-generated definitions. */ | |
511 | } | |
512 | ||
513 | If you have multiple occurrences of any one of the above declarations, Bison | |
514 | will concatenate the contents in declaration order. | |
515 | ||
516 | [Although we failed to mention this here in the 2.3a release, the prologue | |
517 | alternatives were experimental, and they were rewritten in future versions.] | |
518 | ||
519 | ** The option `--report=look-ahead' has been changed to `--report=lookahead'. | |
520 | The old spelling still works, but is not documented and may be removed | |
521 | in a future release. | |
522 | ||
523 | * Changes in version 2.3, 2006-06-05: | |
524 | ||
525 | ** GLR grammars should now use `YYRECOVERING ()' instead of `YYRECOVERING', | |
526 | for compatibility with LALR(1) grammars. | |
527 | ||
528 | ** It is now documented that any definition of YYSTYPE or YYLTYPE should | |
529 | be to a type name that does not contain parentheses or brackets. | |
530 | ||
531 | * Changes in version 2.2, 2006-05-19: | |
532 | ||
533 | ** The distribution terms for all Bison-generated parsers now permit | |
534 | using the parsers in nonfree programs. Previously, this permission | |
535 | was granted only for Bison-generated LALR(1) parsers in C. | |
536 | ||
537 | ** %name-prefix changes the namespace name in C++ outputs. | |
538 | ||
539 | ** The C++ parsers export their token_type. | |
540 | ||
541 | ** Bison now allows multiple %union declarations, and concatenates | |
542 | their contents together. | |
543 | ||
544 | ** New warning: unused values | |
545 | Right-hand side symbols whose values are not used are reported, | |
546 | if the symbols have destructors. For instance: | |
547 | ||
548 | exp: exp "?" exp ":" exp { $1 ? $1 : $3; } | |
549 | | exp "+" exp | |
550 | ; | |
551 | ||
552 | will trigger a warning about $$ and $5 in the first rule, and $3 in | |
553 | the second ($1 is copied to $$ by the default rule). This example | |
554 | most likely contains three errors, and could be rewritten as: | |
555 | ||
556 | exp: exp "?" exp ":" exp | |
557 | { $$ = $1 ? $3 : $5; free ($1 ? $5 : $3); free ($1); } | |
558 | | exp "+" exp | |
559 | { $$ = $1 ? $1 : $3; if ($1) free ($3); } | |
560 | ; | |
561 | ||
562 | However, if the original actions were really intended, memory leaks | |
563 | and all, the warnings can be suppressed by letting Bison believe the | |
564 | values are used, e.g.: | |
565 | ||
566 | exp: exp "?" exp ":" exp { $1 ? $1 : $3; (void) ($$, $5); } | |
567 | | exp "+" exp { $$ = $1; (void) $3; } | |
568 | ; | |
569 | ||
570 | If there are mid-rule actions, the warning is issued if no action | |
571 | uses it. The following triggers no warning: $1 and $3 are used. | |
572 | ||
573 | exp: exp { push ($1); } '+' exp { push ($3); sum (); }; | |
574 | ||
575 | The warning is intended to help catching lost values and memory leaks. | |
576 | If a value is ignored, its associated memory typically is not reclaimed. | |
577 | ||
578 | ** %destructor vs. YYABORT, YYACCEPT, and YYERROR. | |
579 | Destructors are now called when user code invokes YYABORT, YYACCEPT, | |
580 | and YYERROR, for all objects on the stack, other than objects | |
581 | corresponding to the right-hand side of the current rule. | |
582 | ||
583 | ** %expect, %expect-rr | |
584 | Incorrect numbers of expected conflicts are now actual errors, | |
585 | instead of warnings. | |
586 | ||
587 | ** GLR, YACC parsers. | |
588 | The %parse-params are available in the destructors (and the | |
589 | experimental printers) as per the documentation. | |
590 | ||
591 | ** Bison now warns if it finds a stray `$' or `@' in an action. | |
592 | ||
593 | ** %require "VERSION" | |
594 | This specifies that the grammar file depends on features implemented | |
595 | in Bison version VERSION or higher. | |
596 | ||
597 | ** lalr1.cc: The token and value types are now class members. | |
598 | The tokens were defined as free form enums and cpp macros. YYSTYPE | |
599 | was defined as a free form union. They are now class members: | |
600 | tokens are enumerations of the `yy::parser::token' struct, and the | |
601 | semantic values have the `yy::parser::semantic_type' type. | |
602 | ||
603 | If you do not want or can update to this scheme, the directive | |
604 | `%define "global_tokens_and_yystype" "1"' triggers the global | |
605 | definition of tokens and YYSTYPE. This change is suitable both | |
606 | for previous releases of Bison, and this one. | |
607 | ||
608 | If you wish to update, then make sure older version of Bison will | |
609 | fail using `%require "2.2"'. | |
610 | ||
611 | ** DJGPP support added. | |
612 | \f | |
613 | * Changes in version 2.1, 2005-09-16: | |
614 | ||
615 | ** The C++ lalr1.cc skeleton supports %lex-param. | |
616 | ||
617 | ** Bison-generated parsers now support the translation of diagnostics like | |
618 | "syntax error" into languages other than English. The default | |
619 | language is still English. For details, please see the new | |
620 | Internationalization section of the Bison manual. Software | |
621 | distributors should also see the new PACKAGING file. Thanks to | |
622 | Bruno Haible for this new feature. | |
623 | ||
624 | ** Wording in the Bison-generated parsers has been changed slightly to | |
625 | simplify translation. In particular, the message "memory exhausted" | |
626 | has replaced "parser stack overflow", as the old message was not | |
627 | always accurate for modern Bison-generated parsers. | |
628 | ||
629 | ** Destructors are now called when the parser aborts, for all symbols left | |
630 | behind on the stack. Also, the start symbol is now destroyed after a | |
631 | successful parse. In both cases, the behavior was formerly inconsistent. | |
632 | ||
633 | ** When generating verbose diagnostics, Bison-generated parsers no longer | |
634 | quote the literal strings associated with tokens. For example, for | |
635 | a syntax error associated with '%token NUM "number"' they might | |
636 | print 'syntax error, unexpected number' instead of 'syntax error, | |
637 | unexpected "number"'. | |
638 | \f | |
639 | * Changes in version 2.0, 2004-12-25: | |
640 | ||
641 | ** Possibly-incompatible changes | |
642 | ||
643 | - Bison-generated parsers no longer default to using the alloca function | |
644 | (when available) to extend the parser stack, due to widespread | |
645 | problems in unchecked stack-overflow detection. You can "#define | |
646 | YYSTACK_USE_ALLOCA 1" to require the use of alloca, but please read | |
647 | the manual to determine safe values for YYMAXDEPTH in that case. | |
648 | ||
649 | - Error token location. | |
650 | During error recovery, the location of the syntax error is updated | |
651 | to cover the whole sequence covered by the error token: it includes | |
652 | the shifted symbols thrown away during the first part of the error | |
653 | recovery, and the lookahead rejected during the second part. | |
654 | ||
655 | - Semicolon changes: | |
656 | . Stray semicolons are no longer allowed at the start of a grammar. | |
657 | . Semicolons are now required after in-grammar declarations. | |
658 | ||
659 | - Unescaped newlines are no longer allowed in character constants or | |
660 | string literals. They were never portable, and GCC 3.4.0 has | |
661 | dropped support for them. Better diagnostics are now generated if | |
662 | forget a closing quote. | |
663 | ||
664 | - NUL bytes are no longer allowed in Bison string literals, unfortunately. | |
665 | ||
666 | ** New features | |
667 | ||
668 | - GLR grammars now support locations. | |
669 | ||
670 | - New directive: %initial-action. | |
671 | This directive allows the user to run arbitrary code (including | |
672 | initializing @$) from yyparse before parsing starts. | |
673 | ||
674 | - A new directive "%expect-rr N" specifies the expected number of | |
675 | reduce/reduce conflicts in GLR parsers. | |
676 | ||
677 | - %token numbers can now be hexadecimal integers, e.g., `%token FOO 0x12d'. | |
678 | This is a GNU extension. | |
679 | ||
680 | - The option `--report=lookahead' was changed to `--report=look-ahead'. | |
681 | [However, this was changed back after 2.3.] | |
682 | ||
683 | - Experimental %destructor support has been added to lalr1.cc. | |
684 | ||
685 | - New configure option --disable-yacc, to disable installation of the | |
686 | yacc command and -ly library introduced in 1.875 for POSIX conformance. | |
687 | ||
688 | ** Bug fixes | |
689 | ||
690 | - For now, %expect-count violations are now just warnings, not errors. | |
691 | This is for compatibility with Bison 1.75 and earlier (when there are | |
692 | reduce/reduce conflicts) and with Bison 1.30 and earlier (when there | |
693 | are too many or too few shift/reduce conflicts). However, in future | |
694 | versions of Bison we plan to improve the %expect machinery so that | |
695 | these violations will become errors again. | |
696 | ||
697 | - Within Bison itself, numbers (e.g., goto numbers) are no longer | |
698 | arbitrarily limited to 16-bit counts. | |
699 | ||
700 | - Semicolons are now allowed before "|" in grammar rules, as POSIX requires. | |
701 | \f | |
702 | * Changes in version 1.875, 2003-01-01: | |
703 | ||
704 | ** The documentation license has been upgraded to version 1.2 | |
705 | of the GNU Free Documentation License. | |
706 | ||
707 | ** syntax error processing | |
708 | ||
709 | - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error | |
710 | locations too. This fixes bugs in error-location computation. | |
711 | ||
712 | - %destructor | |
713 | It is now possible to reclaim the memory associated to symbols | |
714 | discarded during error recovery. This feature is still experimental. | |
715 | ||
716 | - %error-verbose | |
717 | This new directive is preferred over YYERROR_VERBOSE. | |
718 | ||
719 | - #defining yyerror to steal internal variables is discouraged. | |
720 | It is not guaranteed to work forever. | |
721 | ||
722 | ** POSIX conformance | |
723 | ||
724 | - Semicolons are once again optional at the end of grammar rules. | |
725 | This reverts to the behavior of Bison 1.33 and earlier, and improves | |
726 | compatibility with Yacc. | |
727 | ||
728 | - `parse error' -> `syntax error' | |
729 | Bison now uniformly uses the term `syntax error'; formerly, the code | |
730 | and manual sometimes used the term `parse error' instead. POSIX | |
731 | requires `syntax error' in diagnostics, and it was thought better to | |
732 | be consistent. | |
733 | ||
734 | - The documentation now emphasizes that yylex and yyerror must be | |
735 | declared before use. C99 requires this. | |
736 | ||
737 | - Bison now parses C99 lexical constructs like UCNs and | |
738 | backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires. | |
739 | ||
740 | - File names are properly escaped in C output. E.g., foo\bar.y is | |
741 | output as "foo\\bar.y". | |
742 | ||
743 | - Yacc command and library now available | |
744 | The Bison distribution now installs a `yacc' command, as POSIX requires. | |
745 | Also, Bison now installs a small library liby.a containing | |
746 | implementations of Yacc-compatible yyerror and main functions. | |
747 | This library is normally not useful, but POSIX requires it. | |
748 | ||
749 | - Type clashes now generate warnings, not errors. | |
750 | ||
751 | - If the user does not define YYSTYPE as a macro, Bison now declares it | |
752 | using typedef instead of defining it as a macro. | |
753 | For consistency, YYLTYPE is also declared instead of defined. | |
754 | ||
755 | ** Other compatibility issues | |
756 | ||
757 | - %union directives can now have a tag before the `{', e.g., the | |
758 | directive `%union foo {...}' now generates the C code | |
759 | `typedef union foo { ... } YYSTYPE;'; this is for Yacc compatibility. | |
760 | The default union tag is `YYSTYPE', for compatibility with Solaris 9 Yacc. | |
761 | For consistency, YYLTYPE's struct tag is now `YYLTYPE' not `yyltype'. | |
762 | This is for compatibility with both Yacc and Bison 1.35. | |
763 | ||
764 | - `;' is output before the terminating `}' of an action, for | |
765 | compatibility with Bison 1.35. | |
766 | ||
767 | - Bison now uses a Yacc-style format for conflict reports, e.g., | |
768 | `conflicts: 2 shift/reduce, 1 reduce/reduce'. | |
769 | ||
770 | - `yystype' and `yyltype' are now obsolescent macros instead of being | |
771 | typedefs or tags; they are no longer documented and are planned to be | |
772 | withdrawn in a future release. | |
773 | ||
774 | ** GLR parser notes | |
775 | ||
776 | - GLR and inline | |
777 | Users of Bison have to decide how they handle the portability of the | |
778 | C keyword `inline'. | |
779 | ||
780 | - `parsing stack overflow...' -> `parser stack overflow' | |
781 | GLR parsers now report `parser stack overflow' as per the Bison manual. | |
782 | ||
783 | ** Bison now warns if it detects conflicting outputs to the same file, | |
784 | e.g., it generates a warning for `bison -d -o foo.h foo.y' since | |
785 | that command outputs both code and header to foo.h. | |
786 | ||
787 | ** #line in output files | |
788 | - --no-line works properly. | |
789 | ||
790 | ** Bison can no longer be built by a K&R C compiler; it requires C89 or | |
791 | later to be built. This change originally took place a few versions | |
792 | ago, but nobody noticed until we recently asked someone to try | |
793 | building Bison with a K&R C compiler. | |
794 | \f | |
795 | * Changes in version 1.75, 2002-10-14: | |
796 | ||
797 | ** Bison should now work on 64-bit hosts. | |
798 | ||
799 | ** Indonesian translation thanks to Tedi Heriyanto. | |
800 | ||
801 | ** GLR parsers | |
802 | Fix spurious parse errors. | |
803 | ||
804 | ** Pure parsers | |
805 | Some people redefine yyerror to steal yyparse' private variables. | |
806 | Reenable this trick until an official feature replaces it. | |
807 | ||
808 | ** Type Clashes | |
809 | In agreement with POSIX and with other Yaccs, leaving a default | |
810 | action is valid when $$ is untyped, and $1 typed: | |
811 | ||
812 | untyped: ... typed; | |
813 | ||
814 | but the converse remains an error: | |
815 | ||
816 | typed: ... untyped; | |
817 | ||
818 | ** Values of mid-rule actions | |
819 | The following code: | |
820 | ||
821 | foo: { ... } { $$ = $1; } ... | |
822 | ||
823 | was incorrectly rejected: $1 is defined in the second mid-rule | |
824 | action, and is equal to the $$ of the first mid-rule action. | |
825 | \f | |
826 | * Changes in version 1.50, 2002-10-04: | |
827 | ||
828 | ** GLR parsing | |
829 | The declaration | |
830 | %glr-parser | |
831 | causes Bison to produce a Generalized LR (GLR) parser, capable of handling | |
832 | almost any context-free grammar, ambiguous or not. The new declarations | |
833 | %dprec and %merge on grammar rules allow parse-time resolution of | |
834 | ambiguities. Contributed by Paul Hilfinger. | |
835 | ||
836 | Unfortunately Bison 1.50 does not work properly on 64-bit hosts | |
837 | like the Alpha, so please stick to 32-bit hosts for now. | |
838 | ||
839 | ** Output Directory | |
840 | When not in Yacc compatibility mode, when the output file was not | |
841 | specified, running `bison foo/bar.y' created `foo/bar.c'. It | |
842 | now creates `bar.c'. | |
843 | ||
844 | ** Undefined token | |
845 | The undefined token was systematically mapped to 2 which prevented | |
846 | the use of 2 by the user. This is no longer the case. | |
847 | ||
848 | ** Unknown token numbers | |
849 | If yylex returned an out of range value, yyparse could die. This is | |
850 | no longer the case. | |
851 | ||
852 | ** Error token | |
853 | According to POSIX, the error token must be 256. | |
854 | Bison extends this requirement by making it a preference: *if* the | |
855 | user specified that one of her tokens is numbered 256, then error | |
856 | will be mapped onto another number. | |
857 | ||
858 | ** Verbose error messages | |
859 | They no longer report `..., expecting error or...' for states where | |
860 | error recovery is possible. | |
861 | ||
862 | ** End token | |
863 | Defaults to `$end' instead of `$'. | |
864 | ||
865 | ** Error recovery now conforms to documentation and to POSIX | |
866 | When a Bison-generated parser encounters a syntax error, it now pops | |
867 | the stack until it finds a state that allows shifting the error | |
868 | token. Formerly, it popped the stack until it found a state that | |
869 | allowed some non-error action other than a default reduction on the | |
870 | error token. The new behavior has long been the documented behavior, | |
871 | and has long been required by POSIX. For more details, please see | |
872 | Paul Eggert, "Reductions during Bison error handling" (2002-05-20) | |
873 | <http://lists.gnu.org/archive/html/bug-bison/2002-05/msg00038.html>. | |
874 | ||
875 | ** Traces | |
876 | Popped tokens and nonterminals are now reported. | |
877 | ||
878 | ** Larger grammars | |
879 | Larger grammars are now supported (larger token numbers, larger grammar | |
880 | size (= sum of the LHS and RHS lengths), larger LALR tables). | |
881 | Formerly, many of these numbers ran afoul of 16-bit limits; | |
882 | now these limits are 32 bits on most hosts. | |
883 | ||
884 | ** Explicit initial rule | |
885 | Bison used to play hacks with the initial rule, which the user does | |
886 | not write. It is now explicit, and visible in the reports and | |
887 | graphs as rule 0. | |
888 | ||
889 | ** Useless rules | |
890 | Before, Bison reported the useless rules, but, although not used, | |
891 | included them in the parsers. They are now actually removed. | |
892 | ||
893 | ** Useless rules, useless nonterminals | |
894 | They are now reported, as a warning, with their locations. | |
895 | ||
896 | ** Rules never reduced | |
897 | Rules that can never be reduced because of conflicts are now | |
898 | reported. | |
899 | ||
900 | ** Incorrect `Token not used' | |
901 | On a grammar such as | |
902 | ||
903 | %token useless useful | |
904 | %% | |
905 | exp: '0' %prec useful; | |
906 | ||
907 | where a token was used to set the precedence of the last rule, | |
908 | bison reported both `useful' and `useless' as useless tokens. | |
909 | ||
910 | ** Revert the C++ namespace changes introduced in 1.31 | |
911 | as they caused too many portability hassles. | |
912 | ||
913 | ** Default locations | |
914 | By an accident of design, the default computation of @$ was | |
915 | performed after another default computation was performed: @$ = @1. | |
916 | The latter is now removed: YYLLOC_DEFAULT is fully responsible of | |
917 | the computation of @$. | |
918 | ||
919 | ** Token end-of-file | |
920 | The token end of file may be specified by the user, in which case, | |
921 | the user symbol is used in the reports, the graphs, and the verbose | |
922 | error messages instead of `$end', which remains being the default. | |
923 | For instance | |
924 | %token MYEOF 0 | |
925 | or | |
926 | %token MYEOF 0 "end of file" | |
927 | ||
928 | ** Semantic parser | |
929 | This old option, which has been broken for ages, is removed. | |
930 | ||
931 | ** New translations | |
932 | Brazilian Portuguese, thanks to Alexandre Folle de Menezes. | |
933 | Croatian, thanks to Denis Lackovic. | |
934 | ||
935 | ** Incorrect token definitions | |
936 | When given `%token 'a' "A"', Bison used to output `#define 'a' 65'. | |
937 | ||
938 | ** Token definitions as enums | |
939 | Tokens are output both as the traditional #define's, and, provided | |
940 | the compiler supports ANSI C or is a C++ compiler, as enums. | |
941 | This lets debuggers display names instead of integers. | |
942 | ||
943 | ** Reports | |
944 | In addition to --verbose, bison supports --report=THINGS, which | |
945 | produces additional information: | |
946 | - itemset | |
947 | complete the core item sets with their closure | |
948 | - lookahead [changed to `look-ahead' in 1.875e through 2.3, but changed back] | |
949 | explicitly associate lookahead tokens to items | |
950 | - solved | |
951 | describe shift/reduce conflicts solving. | |
952 | Bison used to systematically output this information on top of | |
953 | the report. Solved conflicts are now attached to their states. | |
954 | ||
955 | ** Type clashes | |
956 | Previous versions don't complain when there is a type clash on | |
957 | the default action if the rule has a mid-rule action, such as in: | |
958 | ||
959 | %type <foo> bar | |
960 | %% | |
961 | bar: '0' {} '0'; | |
962 | ||
963 | This is fixed. | |
964 | ||
965 | ** GNU M4 is now required when using Bison. | |
966 | \f | |
967 | * Changes in version 1.35, 2002-03-25: | |
968 | ||
969 | ** C Skeleton | |
970 | Some projects use Bison's C parser with C++ compilers, and define | |
971 | YYSTYPE as a class. The recent adjustment of C parsers for data | |
972 | alignment and 64 bit architectures made this impossible. | |
973 | ||
974 | Because for the time being no real solution for C++ parser | |
975 | generation exists, kludges were implemented in the parser to | |
976 | maintain this use. In the future, when Bison has C++ parsers, this | |
977 | kludge will be disabled. | |
978 | ||
979 | This kludge also addresses some C++ problems when the stack was | |
980 | extended. | |
981 | \f | |
982 | * Changes in version 1.34, 2002-03-12: | |
983 | ||
984 | ** File name clashes are detected | |
985 | $ bison foo.y -d -o foo.x | |
986 | fatal error: header and parser would both be named `foo.x' | |
987 | ||
988 | ** A missing `;' at the end of a rule triggers a warning | |
989 | In accordance with POSIX, and in agreement with other | |
990 | Yacc implementations, Bison will mandate this semicolon in the near | |
991 | future. This eases the implementation of a Bison parser of Bison | |
992 | grammars by making this grammar LALR(1) instead of LR(2). To | |
993 | facilitate the transition, this release introduces a warning. | |
994 | ||
995 | ** Revert the C++ namespace changes introduced in 1.31, as they caused too | |
996 | many portability hassles. | |
997 | ||
998 | ** DJGPP support added. | |
999 | ||
1000 | ** Fix test suite portability problems. | |
1001 | \f | |
1002 | * Changes in version 1.33, 2002-02-07: | |
1003 | ||
1004 | ** Fix C++ issues | |
1005 | Groff could not be compiled for the definition of size_t was lacking | |
1006 | under some conditions. | |
1007 | ||
1008 | ** Catch invalid @n | |
1009 | As is done with $n. | |
1010 | \f | |
1011 | * Changes in version 1.32, 2002-01-23: | |
1012 | ||
1013 | ** Fix Yacc output file names | |
1014 | ||
1015 | ** Portability fixes | |
1016 | ||
1017 | ** Italian, Dutch translations | |
1018 | \f | |
1019 | * Changes in version 1.31, 2002-01-14: | |
1020 | ||
1021 | ** Many Bug Fixes | |
1022 | ||
1023 | ** GNU Gettext and %expect | |
1024 | GNU Gettext asserts 10 s/r conflicts, but there are 7. Now that | |
1025 | Bison dies on incorrect %expectations, we fear there will be | |
1026 | too many bug reports for Gettext, so _for the time being_, %expect | |
1027 | does not trigger an error when the input file is named `plural.y'. | |
1028 | ||
1029 | ** Use of alloca in parsers | |
1030 | If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use | |
1031 | malloc exclusively. Since 1.29, but was not NEWS'ed. | |
1032 | ||
1033 | alloca is used only when compiled with GCC, to avoid portability | |
1034 | problems as on AIX. | |
1035 | ||
1036 | ** yyparse now returns 2 if memory is exhausted; formerly it dumped core. | |
1037 | ||
1038 | ** When the generated parser lacks debugging code, YYDEBUG is now 0 | |
1039 | (as POSIX requires) instead of being undefined. | |
1040 | ||
1041 | ** User Actions | |
1042 | Bison has always permitted actions such as { $$ = $1 }: it adds the | |
1043 | ending semicolon. Now if in Yacc compatibility mode, the semicolon | |
1044 | is no longer output: one has to write { $$ = $1; }. | |
1045 | ||
1046 | ** Better C++ compliance | |
1047 | The output parsers try to respect C++ namespaces. | |
1048 | [This turned out to be a failed experiment, and it was reverted later.] | |
1049 | ||
1050 | ** Reduced Grammars | |
1051 | Fixed bugs when reporting useless nonterminals. | |
1052 | ||
1053 | ** 64 bit hosts | |
1054 | The parsers work properly on 64 bit hosts. | |
1055 | ||
1056 | ** Error messages | |
1057 | Some calls to strerror resulted in scrambled or missing error messages. | |
1058 | ||
1059 | ** %expect | |
1060 | When the number of shift/reduce conflicts is correct, don't issue | |
1061 | any warning. | |
1062 | ||
1063 | ** The verbose report includes the rule line numbers. | |
1064 | ||
1065 | ** Rule line numbers are fixed in traces. | |
1066 | ||
1067 | ** Swedish translation | |
1068 | ||
1069 | ** Parse errors | |
1070 | Verbose parse error messages from the parsers are better looking. | |
1071 | Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'('' | |
1072 | Now: parse error: unexpected '/', expecting "number" or '-' or '(' | |
1073 | ||
1074 | ** Fixed parser memory leaks. | |
1075 | When the generated parser was using malloc to extend its stacks, the | |
1076 | previous allocations were not freed. | |
1077 | ||
1078 | ** Fixed verbose output file. | |
1079 | Some newlines were missing. | |
1080 | Some conflicts in state descriptions were missing. | |
1081 | ||
1082 | ** Fixed conflict report. | |
1083 | Option -v was needed to get the result. | |
1084 | ||
1085 | ** %expect | |
1086 | Was not used. | |
1087 | Mismatches are errors, not warnings. | |
1088 | ||
1089 | ** Fixed incorrect processing of some invalid input. | |
1090 | ||
1091 | ** Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H. | |
1092 | ||
1093 | ** Fixed some typos in the documentation. | |
1094 | ||
1095 | ** %token MY_EOF 0 is supported. | |
1096 | Before, MY_EOF was silently renumbered as 257. | |
1097 | ||
1098 | ** doc/refcard.tex is updated. | |
1099 | ||
1100 | ** %output, %file-prefix, %name-prefix. | |
1101 | New. | |
1102 | ||
1103 | ** --output | |
1104 | New, aliasing `--output-file'. | |
1105 | \f | |
1106 | * Changes in version 1.30, 2001-10-26: | |
1107 | ||
1108 | ** `--defines' and `--graph' have now an optional argument which is the | |
1109 | output file name. `-d' and `-g' do not change; they do not take any | |
1110 | argument. | |
1111 | ||
1112 | ** `%source_extension' and `%header_extension' are removed, failed | |
1113 | experiment. | |
1114 | ||
1115 | ** Portability fixes. | |
1116 | \f | |
1117 | * Changes in version 1.29, 2001-09-07: | |
1118 | ||
1119 | ** The output file does not define const, as this caused problems when used | |
1120 | with common autoconfiguration schemes. If you still use ancient compilers | |
1121 | that lack const, compile with the equivalent of the C compiler option | |
1122 | `-Dconst='. autoconf's AC_C_CONST macro provides one way to do this. | |
1123 | ||
1124 | ** Added `-g' and `--graph'. | |
1125 | ||
1126 | ** The Bison manual is now distributed under the terms of the GNU FDL. | |
1127 | ||
1128 | ** The input and the output files has automatically a similar extension. | |
1129 | ||
1130 | ** Russian translation added. | |
1131 | ||
1132 | ** NLS support updated; should hopefully be less troublesome. | |
1133 | ||
1134 | ** Added the old Bison reference card. | |
1135 | ||
1136 | ** Added `--locations' and `%locations'. | |
1137 | ||
1138 | ** Added `-S' and `--skeleton'. | |
1139 | ||
1140 | ** `%raw', `-r', `--raw' is disabled. | |
1141 | ||
1142 | ** Special characters are escaped when output. This solves the problems | |
1143 | of the #line lines with path names including backslashes. | |
1144 | ||
1145 | ** New directives. | |
1146 | `%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose', | |
1147 | `%debug', `%source_extension' and `%header_extension'. | |
1148 | ||
1149 | ** @$ | |
1150 | Automatic location tracking. | |
1151 | \f | |
1152 | * Changes in version 1.28, 1999-07-06: | |
1153 | ||
1154 | ** Should compile better now with K&R compilers. | |
1155 | ||
1156 | ** Added NLS. | |
1157 | ||
1158 | ** Fixed a problem with escaping the double quote character. | |
1159 | ||
1160 | ** There is now a FAQ. | |
1161 | \f | |
1162 | * Changes in version 1.27: | |
1163 | ||
1164 | ** The make rule which prevented bison.simple from being created on | |
1165 | some systems has been fixed. | |
1166 | \f | |
1167 | * Changes in version 1.26: | |
1168 | ||
1169 | ** Bison now uses automake. | |
1170 | ||
1171 | ** New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>. | |
1172 | ||
1173 | ** Token numbers now start at 257 as previously documented, not 258. | |
1174 | ||
1175 | ** Bison honors the TMPDIR environment variable. | |
1176 | ||
1177 | ** A couple of buffer overruns have been fixed. | |
1178 | ||
1179 | ** Problems when closing files should now be reported. | |
1180 | ||
1181 | ** Generated parsers should now work even on operating systems which do | |
1182 | not provide alloca(). | |
1183 | \f | |
1184 | * Changes in version 1.25, 1995-10-16: | |
1185 | ||
1186 | ** Errors in the input grammar are not fatal; Bison keeps reading | |
1187 | the grammar file, and reports all the errors found in it. | |
1188 | ||
1189 | ** Tokens can now be specified as multiple-character strings: for | |
1190 | example, you could use "<=" for a token which looks like <=, instead | |
1191 | of chosing a name like LESSEQ. | |
1192 | ||
1193 | ** The %token_table declaration says to write a table of tokens (names | |
1194 | and numbers) into the parser file. The yylex function can use this | |
1195 | table to recognize multiple-character string tokens, or for other | |
1196 | purposes. | |
1197 | ||
1198 | ** The %no_lines declaration says not to generate any #line preprocessor | |
1199 | directives in the parser file. | |
1200 | ||
1201 | ** The %raw declaration says to use internal Bison token numbers, not | |
1202 | Yacc-compatible token numbers, when token names are defined as macros. | |
1203 | ||
1204 | ** The --no-parser option produces the parser tables without including | |
1205 | the parser engine; a project can now use its own parser engine. | |
1206 | The actions go into a separate file called NAME.act, in the form of | |
1207 | a switch statement body. | |
1208 | \f | |
1209 | * Changes in version 1.23: | |
1210 | ||
1211 | The user can define YYPARSE_PARAM as the name of an argument to be | |
1212 | passed into yyparse. The argument should have type void *. It should | |
1213 | actually point to an object. Grammar actions can access the variable | |
1214 | by casting it to the proper pointer type. | |
1215 | ||
1216 | Line numbers in output file corrected. | |
1217 | \f | |
1218 | * Changes in version 1.22: | |
1219 | ||
1220 | --help option added. | |
1221 | \f | |
1222 | * Changes in version 1.20: | |
1223 | ||
1224 | Output file does not redefine const for C++. | |
1225 | ||
1226 | Local Variables: | |
1227 | mode: outline | |
1228 | End: | |
1229 | ||
1230 | ----- | |
1231 | ||
1232 | Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, | |
1233 | 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc. | |
1234 | ||
1235 | This file is part of Bison, the GNU Parser Generator. | |
1236 | ||
1237 | This program is free software: you can redistribute it and/or modify | |
1238 | it under the terms of the GNU General Public License as published by | |
1239 | the Free Software Foundation, either version 3 of the License, or | |
1240 | (at your option) any later version. | |
1241 | ||
1242 | This program is distributed in the hope that it will be useful, | |
1243 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
1244 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
1245 | GNU General Public License for more details. | |
1246 | ||
1247 | You should have received a copy of the GNU General Public License | |
1248 | along with this program. If not, see <http://www.gnu.org/licenses/>. |