Commit | Line | Data |
---|---|---|
ed7658fe | 1 | GNU Bison NEWS |
3af4feb2 | 2 | |
933ec544 AD |
3 | * Noteworthy changes in release ?.? (????-??-??) [?] |
4 | ||
5a05f42e | 5 | ** Changes in the format of error messages |
cbaea010 TR |
6 | |
7 | This used to be the format of many error reports: | |
8 | ||
9 | foo.y:5.10-24: result type clash on merge function 'merge': <t3> != <t2> | |
10 | foo.y:4.13-27: previous declaration | |
11 | ||
12 | It is now: | |
13 | ||
14 | foo.y:5.10-25: result type clash on merge function 'merge': <t3> != <t2> | |
15 | foo.y:4.13-27: previous declaration | |
16 | ||
d3e4409a AD |
17 | ** Exception safety (lalr1.cc) |
18 | ||
19 | The parse function now catches exceptions, uses the %destructors to | |
20 | release memory (the lookahead symbol and the symbols pushed on the stack) | |
7287be84 | 21 | before re-throwing the exception. |
d3e4409a AD |
22 | |
23 | This feature is somewhat experimental. User feedback would be | |
24 | appreciated. | |
25 | ||
7287be84 | 26 | ** New %define variable: api.location.type (glr.cc, lalr1.cc, lalr1.java) |
db8ab2be AD |
27 | |
28 | The %define variable api.location.type defines the name of the type to use | |
29 | for locations. When defined, Bison no longer generates the position.hh | |
30 | and location.hh files, nor does the parser will include them: the user is | |
31 | then responsible to define her type. | |
32 | ||
33 | This can be used in programs with several parsers to factor their location | |
7287be84 AD |
34 | and position files: let one of them generate them, and the others just use |
35 | them. | |
db8ab2be AD |
36 | |
37 | This feature was actually introduced, but not documented, in Bison 2.5, | |
38 | under the name "location_type" (which is maintained for backward | |
39 | compatibility). | |
40 | ||
7287be84 AD |
41 | For consistency, lalr1.java's %define variables location_type and |
42 | position_type are deprecated in favor of api.location.type and | |
43 | api.position.type. | |
44 | ||
9c16d399 | 45 | ** Graph improvements in DOT and XSLT |
fc4fdd62 TR |
46 | |
47 | The graphical presentation of the states is more readable: their shape is | |
48 | now rectangular, the state number is clearly displayed, and the items are | |
49 | numbered and left-justified. | |
50 | ||
51 | The reductions are now explicitly represented as transitions to other | |
52 | diamond shaped nodes. | |
53 | ||
9c16d399 TR |
54 | These changes are present in both --graph output and xml2dot.xsl XSLT |
55 | processing, with minor (documented) differences. | |
56 | ||
57 | Two nodes were added to the documentation: Xml and Graphviz. | |
58 | ||
9d3f7eaf | 59 | * Noteworthy changes in release 2.6.5 (2012-11-07) [stable] |
6f1360bd | 60 | |
a68b1f23 AD |
61 | We consider compiler warnings about Bison generated parsers to be bugs. |
62 | Rather than working around them in your own project, please consider | |
63 | reporting them to us. | |
64 | ||
65 | ** Bug fixes | |
66 | ||
67 | Warnings about uninitialized yylval and/or yylloc for push parsers with a | |
68 | pure interface have been fixed for GCC 4.0 up to 4.8, and Clang 2.9 to | |
69 | 3.2. | |
70 | ||
71 | Other issues in the test suite have been addressed. | |
6f1360bd | 72 | |
95066e92 AD |
73 | Nul characters are correctly displayed in error messages. |
74 | ||
a1d1ab50 AD |
75 | When possible, yylloc is correctly initialized before calling yylex. It |
76 | is no longer necessary to initialize it in the %initial-action. | |
77 | ||
0ac15849 | 78 | * Noteworthy changes in release 2.6.4 (2012-10-23) [stable] |
a4eb820f | 79 | |
468455e1 | 80 | Bison 2.6.3's --version was incorrect. This release fixes this issue. |
a4eb820f | 81 | |
6eb8f74f | 82 | * Noteworthy changes in release 2.6.3 (2012-10-22) [stable] |
933ec544 | 83 | |
6b4cb804 AD |
84 | ** Bug fixes |
85 | ||
9a50c55a | 86 | Bugs and portability issues in the test suite have been fixed. |
6b4cb804 AD |
87 | |
88 | Some errors in translations have been addressed, and --help now directs | |
89 | users to the appropriate place to report them. | |
90 | ||
91 | Stray Info files shipped by accident are removed. | |
92 | ||
93 | Incorrect definitions of YY_, issued by yacc.c when no parser header is | |
94 | generated, are removed. | |
933ec544 | 95 | |
90b1335a TR |
96 | All the generated headers are self-contained. |
97 | ||
6192d2c6 AD |
98 | ** Header guards (yacc.c, glr.c, glr.cc) |
99 | ||
100 | In order to avoid collisions, the header guards are now | |
101 | YY_<PREFIX>_<FILE>_INCLUDED, instead of merely <PREFIX>_<FILE>. | |
102 | For instance the header generated from | |
103 | ||
104 | %define api.prefix "calc" | |
105 | %defines "lib/parse.h" | |
106 | ||
107 | will use YY_CALC_LIB_PARSE_H_INCLUDED as guard. | |
108 | ||
7b70847e | 109 | ** Fix compiler warnings in the generated parser (yacc.c, glr.c) |
8f8439ce AD |
110 | |
111 | The compilation of pure parsers (%define api.pure) can trigger GCC | |
112 | warnings such as: | |
113 | ||
114 | input.c: In function 'yyparse': | |
115 | input.c:1503:12: warning: 'yylval' may be used uninitialized in this | |
116 | function [-Wmaybe-uninitialized] | |
117 | *++yyvsp = yylval; | |
118 | ^ | |
119 | ||
120 | This is now fixed; pragmas to avoid these warnings are no longer needed. | |
121 | ||
7b70847e AD |
122 | Warnings from clang ("equality comparison with extraneous parentheses" and |
123 | "function declared 'noreturn' should not return") have also been | |
124 | addressed. | |
125 | ||
e1eeecd3 | 126 | * Noteworthy changes in release 2.6.2 (2012-08-03) [stable] |
9c26b8fc | 127 | |
43ca8040 AD |
128 | ** Bug fixes |
129 | ||
130 | Buffer overruns, complaints from Flex, and portability issues in the test | |
131 | suite have been fixed. | |
132 | ||
c9d546b2 AD |
133 | ** Spaces in %lex- and %parse-param (lalr1.cc, glr.cc) |
134 | ||
135 | Trailing end-of-lines in %parse-param or %lex-param would result in | |
136 | invalid C++. This is fixed. | |
9c26b8fc | 137 | |
dcd5344d AD |
138 | ** Spurious spaces and end-of-lines |
139 | ||
140 | The generated files no longer end (nor start) with empty lines. | |
141 | ||
77b214ef | 142 | * Noteworthy changes in release 2.6.1 (2012-07-30) [stable] |
a4107f24 | 143 | |
cbaea010 | 144 | Bison no longer executes user-specified M4 code when processing a grammar. |
8617d87e | 145 | |
e20e6a50 AD |
146 | ** Future Changes |
147 | ||
148 | In addition to the removal of the features announced in Bison 2.6, the | |
149 | next major release will remove the "Temporary hack for adding a semicolon | |
150 | to the user action", as announced in the release 2.5. Instead of: | |
151 | ||
152 | exp: exp "+" exp { $$ = $1 + $3 }; | |
153 | ||
154 | write: | |
155 | ||
156 | exp: exp "+" exp { $$ = $1 + $3; }; | |
157 | ||
8617d87e AD |
158 | ** Bug fixes |
159 | ||
0e164d43 AD |
160 | *** Type names are now properly escaped. |
161 | ||
162 | *** glr.cc: set_debug_level and debug_level work as expected. | |
a4107f24 | 163 | |
26313726 AD |
164 | *** Stray @ or $ in actions |
165 | ||
166 | While Bison used to warn about stray $ or @ in action rules, it did not | |
167 | for other actions such as printers, destructors, or initial actions. It | |
168 | now does. | |
169 | ||
cd735a8c | 170 | ** Type names in actions |
4982f078 AD |
171 | |
172 | For consistency with rule actions, it is now possible to qualify $$ by a | |
cd735a8c | 173 | type-name in destructors, printers, and initial actions. For instance: |
4982f078 AD |
174 | |
175 | %printer { fprintf (yyo, "(%d, %f)", $<ival>$, $<fval>$); } <*> <>; | |
176 | ||
177 | will display two values for each typed and untyped symbol (provided | |
cd735a8c | 178 | that YYSTYPE has both "ival" and "fval" fields). |
4982f078 | 179 | |
1505e8bb | 180 | * Noteworthy changes in release 2.6 (2012-07-19) [stable] |
ad6b775f | 181 | |
c2425191 | 182 | ** Future Changes |
0f11eec2 | 183 | |
55d1006f AD |
184 | The next major release of Bison will drop support for the following |
185 | deprecated features. Please report disagreements to bug-bison@gnu.org. | |
0f11eec2 | 186 | |
aaf61036 | 187 | *** K&R C parsers |
55d1006f AD |
188 | |
189 | Support for generating parsers in K&R C will be removed. Parsers | |
242cc08e | 190 | generated for C support ISO C90, and are tested with ISO C99 and ISO C11 |
55d1006f AD |
191 | compilers. |
192 | ||
258cddbc | 193 | *** Features deprecated since Bison 1.875 |
55d1006f | 194 | |
258cddbc AD |
195 | The definitions of yystype and yyltype will be removed; use YYSTYPE and |
196 | YYLTYPE. | |
55d1006f | 197 | |
258cddbc AD |
198 | YYPARSE_PARAM and YYLEX_PARAM, deprecated in favor of %parse-param and |
199 | %lex-param, will no longer be supported. | |
200 | ||
201 | Support for the preprocessor symbol YYERROR_VERBOSE will be removed, use | |
202 | %error-verbose. | |
55d1006f AD |
203 | |
204 | *** The generated header will be included (yacc.c) | |
0f11eec2 AD |
205 | |
206 | Instead of duplicating the content of the generated header (definition of | |
55d1006f AD |
207 | YYSTYPE, yyparse declaration etc.), the generated parser will include it, |
208 | as is already the case for GLR or C++ parsers. This change is deferred | |
209 | because existing versions of ylwrap (e.g., Automake 1.12.1) do not support | |
210 | it. | |
0f11eec2 | 211 | |
c2425191 | 212 | ** Generated Parser Headers |
56ca3d8f | 213 | |
258cddbc | 214 | *** Guards (yacc.c, glr.c, glr.cc) |
c3e9f08f AD |
215 | |
216 | The generated headers are now guarded, as is already the case for C++ | |
242cc08e | 217 | parsers (lalr1.cc). For instance, with --defines=foo.h: |
c3e9f08f | 218 | |
e29f0771 AD |
219 | #ifndef YY_FOO_H |
220 | # define YY_FOO_H | |
221 | ... | |
222 | #endif /* !YY_FOO_H */ | |
c3e9f08f | 223 | |
258cddbc | 224 | *** New declarations (yacc.c, glr.c) |
56ca3d8f AD |
225 | |
226 | The generated header now declares yydebug and yyparse. Both honor | |
227 | --name-prefix=bar_, and yield | |
228 | ||
e29f0771 | 229 | int bar_parse (void); |
56ca3d8f AD |
230 | |
231 | rather than | |
232 | ||
e29f0771 AD |
233 | #define yyparse bar_parse |
234 | int yyparse (void); | |
56ca3d8f AD |
235 | |
236 | in order to facilitate the inclusion of several parser headers inside a | |
237 | single compilation unit. | |
c3e9f08f | 238 | |
258cddbc AD |
239 | *** Exported symbols in C++ |
240 | ||
241 | The symbols YYTOKEN_TABLE and YYERROR_VERBOSE, which were defined in the | |
242 | header, are removed, as they prevent the possibility of including several | |
243 | generated headers from a single compilation unit. | |
244 | ||
694af10c AD |
245 | *** YYLSP_NEEDED |
246 | ||
247 | For the same reasons, the undocumented and unused macro YYLSP_NEEDED is no | |
248 | longer defined. | |
249 | ||
4b3847c3 AD |
250 | ** New %define variable: api.prefix |
251 | ||
252 | Now that the generated headers are more complete and properly protected | |
253 | against multiple inclusions, constant names, such as YYSTYPE are a | |
254 | problem. While yyparse and others are properly renamed by %name-prefix, | |
255 | YYSTYPE, YYDEBUG and others have never been affected by it. Because it | |
256 | would introduce backward compatibility issues in projects not expecting | |
257 | YYSTYPE to be renamed, instead of changing the behavior of %name-prefix, | |
258 | it is deprecated in favor of a new %define variable: api.prefix. | |
259 | ||
260 | The following examples compares both: | |
261 | ||
262 | %name-prefix "bar_" | %define api.prefix "bar_" | |
263 | %token <ival> FOO %token <ival> FOO | |
264 | %union { int ival; } %union { int ival; } | |
265 | %% %% | |
266 | exp: 'a'; exp: 'a'; | |
267 | ||
268 | bison generates: | |
269 | ||
270 | #ifndef BAR_FOO_H #ifndef BAR_FOO_H | |
271 | # define BAR_FOO_H # define BAR_FOO_H | |
272 | ||
273 | /* Enabling traces. */ /* Enabling traces. */ | |
5f108727 AD |
274 | # ifndef YYDEBUG | # ifndef BAR_DEBUG |
275 | > # if defined YYDEBUG | |
276 | > # if YYDEBUG | |
277 | > # define BAR_DEBUG 1 | |
278 | > # else | |
279 | > # define BAR_DEBUG 0 | |
280 | > # endif | |
281 | > # else | |
282 | # define YYDEBUG 0 | # define BAR_DEBUG 0 | |
283 | > # endif | |
284 | # endif | # endif | |
285 | ||
286 | # if YYDEBUG | # if BAR_DEBUG | |
4b3847c3 AD |
287 | extern int bar_debug; extern int bar_debug; |
288 | # endif # endif | |
289 | ||
290 | /* Tokens. */ /* Tokens. */ | |
291 | # ifndef YYTOKENTYPE | # ifndef BAR_TOKENTYPE | |
292 | # define YYTOKENTYPE | # define BAR_TOKENTYPE | |
293 | enum yytokentype { | enum bar_tokentype { | |
294 | FOO = 258 FOO = 258 | |
295 | }; }; | |
296 | # endif # endif | |
297 | ||
298 | #if ! defined YYSTYPE \ | #if ! defined BAR_STYPE \ | |
299 | && ! defined YYSTYPE_IS_DECLARED | && ! defined BAR_STYPE_IS_DECLARED | |
300 | typedef union YYSTYPE | typedef union BAR_STYPE | |
301 | { { | |
302 | int ival; int ival; | |
303 | } YYSTYPE; | } BAR_STYPE; | |
304 | # define YYSTYPE_IS_DECLARED 1 | # define BAR_STYPE_IS_DECLARED 1 | |
305 | #endif #endif | |
306 | ||
307 | extern YYSTYPE bar_lval; | extern BAR_STYPE bar_lval; | |
308 | ||
309 | int bar_parse (void); int bar_parse (void); | |
310 | ||
311 | #endif /* !BAR_FOO_H */ #endif /* !BAR_FOO_H */ | |
312 | ||
dfaac272 | 313 | * Noteworthy changes in release 2.5.1 (2012-06-05) [stable] |
90dcd415 | 314 | |
debe2c03 | 315 | ** Future changes: |
041308d0 | 316 | |
e4ab1254 | 317 | The next major release will drop support for generating parsers in K&R C. |
ef51bfa7 | 318 | |
466b4cf2 | 319 | ** yacc.c: YYBACKUP works as expected. |
94556574 | 320 | |
d834eca0 AD |
321 | ** glr.c improvements: |
322 | ||
323 | *** Location support is eliminated when not requested: | |
324 | ||
e4ab1254 AD |
325 | GLR parsers used to include location-related code even when locations were |
326 | not requested, and therefore not even usable. | |
d834eca0 AD |
327 | |
328 | *** __attribute__ is preserved: | |
debe2c03 | 329 | |
e4ab1254 AD |
330 | __attribute__ is no longer disabled when __STRICT_ANSI__ is defined (i.e., |
331 | when -std is passed to GCC). | |
debe2c03 | 332 | |
466b4cf2 | 333 | ** lalr1.java: several fixes: |
041308d0 | 334 | |
e4ab1254 AD |
335 | The Java parser no longer throws ArrayIndexOutOfBoundsException if the |
336 | first token leads to a syntax error. Some minor clean ups. | |
041308d0 | 337 | |
22172d47 AD |
338 | ** Changes for C++: |
339 | ||
340 | *** C++11 compatibility: | |
ef51bfa7 | 341 | |
e4ab1254 AD |
342 | C and C++ parsers use "nullptr" instead of "0" when __cplusplus is 201103L |
343 | or higher. | |
ef51bfa7 | 344 | |
22172d47 AD |
345 | *** Header guards |
346 | ||
347 | The header files such as "parser.hh", "location.hh", etc. used a constant | |
348 | name for preprocessor guards, for instance: | |
349 | ||
e29f0771 AD |
350 | #ifndef BISON_LOCATION_HH |
351 | # define BISON_LOCATION_HH | |
352 | ... | |
353 | #endif // !BISON_LOCATION_HH | |
22172d47 AD |
354 | |
355 | The inclusion guard is now computed from "PREFIX/FILE-NAME", where lower | |
356 | case characters are converted to upper case, and series of | |
357 | non-alphanumerical characters are converted to an underscore. | |
358 | ||
359 | With "bison -o lang++/parser.cc", "location.hh" would now include: | |
360 | ||
e29f0771 AD |
361 | #ifndef YY_LANG_LOCATION_HH |
362 | # define YY_LANG_LOCATION_HH | |
363 | ... | |
364 | #endif // !YY_LANG_LOCATION_HH | |
22172d47 AD |
365 | |
366 | *** C++ locations: | |
936c88d1 | 367 | |
e4ab1254 AD |
368 | The position and location constructors (and their initialize methods) |
369 | accept new arguments for line and column. Several issues in the | |
370 | documentation were fixed. | |
936c88d1 | 371 | |
466b4cf2 AD |
372 | ** liby is no longer asking for "rpl_fprintf" on some platforms. |
373 | ||
7e508a2b AD |
374 | ** Changes in the manual: |
375 | ||
376 | *** %printer is documented | |
377 | ||
e4ab1254 AD |
378 | The "%printer" directive, supported since at least Bison 1.50, is finally |
379 | documented. The "mfcalc" example is extended to demonstrate it. | |
7e508a2b | 380 | |
e4ab1254 AD |
381 | For consistency with the C skeletons, the C++ parsers now also support |
382 | "yyoutput" (as an alias to "debug_stream ()"). | |
7e508a2b AD |
383 | |
384 | *** Several improvements have been made: | |
466b4cf2 | 385 | |
e4ab1254 AD |
386 | The layout for grammar excerpts was changed to a more compact scheme. |
387 | Named references are motivated. The description of the automaton | |
388 | description file (*.output) is updated to the current format. Incorrect | |
389 | index entries were fixed. Some other errors were fixed. | |
466b4cf2 | 390 | |
86b08b49 AD |
391 | ** Building bison: |
392 | ||
393 | *** Conflicting prototypes with recent/modified Flex. | |
394 | ||
e4ab1254 AD |
395 | Fixed build problems with the current, unreleased, version of Flex, and |
396 | some modified versions of 2.5.35, which have modified function prototypes. | |
466b4cf2 | 397 | |
8ef26c2a AD |
398 | *** Warnings during the build procedure have been eliminated. |
399 | ||
400 | *** Several portability problems in the test suite have been fixed: | |
466b4cf2 | 401 | |
e4ab1254 AD |
402 | This includes warnings with some compilers, unexpected behavior of tools |
403 | such as diff, warning messages from the test suite itself, etc. | |
466b4cf2 | 404 | |
91aadcc7 | 405 | *** The install-pdf target works properly: |
8ef26c2a | 406 | |
e4ab1254 AD |
407 | Running "make install-pdf" (or -dvi, -html, -info, and -ps) no longer |
408 | halts in the middle of its course. | |
8ef26c2a | 409 | |
b2bc8a1b | 410 | * Changes in version 2.5 (2011-05-14): |
006faedf | 411 | |
eb8c66bb JD |
412 | ** Grammar symbol names can now contain non-initial dashes: |
413 | ||
414 | Consistently with directives (such as %error-verbose) and with | |
415 | %define variables (e.g. push-pull), grammar symbol names may contain | |
416 | dashes in any position except the beginning. This is a GNU | |
417 | extension over POSIX Yacc. Thus, use of this extension is reported | |
418 | by -Wyacc and rejected in Yacc mode (--yacc). | |
419 | ||
3b1977ea | 420 | ** Named references: |
348f5608 AR |
421 | |
422 | Historically, Yacc and Bison have supported positional references | |
423 | ($n, $$) to allow access to symbol values from inside of semantic | |
424 | actions code. | |
425 | ||
426 | Starting from this version, Bison can also accept named references. | |
427 | When no ambiguity is possible, original symbol names may be used | |
428 | as named references: | |
429 | ||
ac3297d5 | 430 | if_stmt : "if" cond_expr "then" then_stmt ';' |
348f5608 AR |
431 | { $if_stmt = mk_if_stmt($cond_expr, $then_stmt); } |
432 | ||
433 | In the more common case, explicit names may be declared: | |
434 | ||
ac3297d5 | 435 | stmt[res] : "if" expr[cond] "then" stmt[then] "else" stmt[else] ';' |
348f5608 AR |
436 | { $res = mk_if_stmt($cond, $then, $else); } |
437 | ||
f840c05a | 438 | Location information is also accessible using @name syntax. When |
348f5608 AR |
439 | accessing symbol names containing dots or dashes, explicit bracketing |
440 | ($[sym.1]) must be used. | |
441 | ||
f840c05a | 442 | These features are experimental in this version. More user feedback |
348f5608 AR |
443 | will help to stabilize them. |
444 | ||
3b1977ea | 445 | ** IELR(1) and canonical LR(1): |
34a6c2d1 JD |
446 | |
447 | IELR(1) is a minimal LR(1) parser table generation algorithm. That | |
448 | is, given any context-free grammar, IELR(1) generates parser tables | |
723206df | 449 | with the full language-recognition power of canonical LR(1) but with |
3b1977ea JD |
450 | nearly the same number of parser states as LALR(1). This reduction |
451 | in parser states is often an order of magnitude. More importantly, | |
34a6c2d1 JD |
452 | because canonical LR(1)'s extra parser states may contain duplicate |
453 | conflicts in the case of non-LR(1) grammars, the number of conflicts | |
454 | for IELR(1) is often an order of magnitude less as well. This can | |
455 | significantly reduce the complexity of developing of a grammar. | |
456 | ||
457 | Bison can now generate IELR(1) and canonical LR(1) parser tables in | |
458 | place of its traditional LALR(1) parser tables, which remain the | |
459 | default. You can specify the type of parser tables in the grammar | |
460 | file with these directives: | |
461 | ||
f37495f6 JD |
462 | %define lr.type lalr |
463 | %define lr.type ielr | |
464 | %define lr.type canonical-lr | |
34a6c2d1 | 465 | |
6f04ee6c | 466 | The default-reduction optimization in the parser tables can also be |
e4ab1254 AD |
467 | adjusted using "%define lr.default-reductions". For details on both |
468 | of these features, see the new section "Tuning LR" in the Bison | |
6f04ee6c | 469 | manual. |
34a6c2d1 JD |
470 | |
471 | These features are experimental. More user feedback will help to | |
472 | stabilize them. | |
473 | ||
6f04ee6c | 474 | ** LAC (Lookahead Correction) for syntax error handling: |
4c38b19e JD |
475 | |
476 | Canonical LR, IELR, and LALR can suffer from a couple of problems | |
477 | upon encountering a syntax error. First, the parser might perform | |
478 | additional parser stack reductions before discovering the syntax | |
6f04ee6c | 479 | error. Such reductions can perform user semantic actions that are |
4c38b19e JD |
480 | unexpected because they are based on an invalid token, and they |
481 | cause error recovery to begin in a different syntactic context than | |
482 | the one in which the invalid token was encountered. Second, when | |
6f04ee6c | 483 | verbose error messages are enabled (with %error-verbose or the |
e4ab1254 | 484 | obsolete "#define YYERROR_VERBOSE"), the expected token list in the |
6f04ee6c JD |
485 | syntax error message can both contain invalid tokens and omit valid |
486 | tokens. | |
4c38b19e JD |
487 | |
488 | The culprits for the above problems are %nonassoc, default | |
489 | reductions in inconsistent states, and parser state merging. Thus, | |
490 | IELR and LALR suffer the most. Canonical LR can suffer only if | |
491 | %nonassoc is used or if default reductions are enabled for | |
492 | inconsistent states. | |
493 | ||
6f04ee6c JD |
494 | LAC is a new mechanism within the parsing algorithm that solves |
495 | these problems for canonical LR, IELR, and LALR without sacrificing | |
496 | %nonassoc, default reductions, or state merging. When LAC is in | |
497 | use, canonical LR and IELR behave almost exactly the same for both | |
498 | syntactically acceptable and syntactically unacceptable input. | |
4c38b19e JD |
499 | While LALR still does not support the full language-recognition |
500 | power of canonical LR and IELR, LAC at least enables LALR's syntax | |
501 | error handling to correctly reflect LALR's language-recognition | |
502 | power. | |
503 | ||
504 | Currently, LAC is only supported for deterministic parsers in C. | |
505 | You can enable LAC with the following directive: | |
506 | ||
507 | %define parse.lac full | |
508 | ||
e4ab1254 | 509 | See the new section "LAC" in the Bison manual for additional |
6f04ee6c | 510 | details including a few caveats. |
4c38b19e JD |
511 | |
512 | LAC is an experimental feature. More user feedback will help to | |
513 | stabilize it. | |
514 | ||
6ee881f6 | 515 | ** %define improvements: |
f37495f6 | 516 | |
3b1977ea | 517 | *** Can now be invoked via the command line: |
4ecd3681 | 518 | |
34d41938 | 519 | Each of these command-line options |
4ecd3681 | 520 | |
34d41938 JD |
521 | -D NAME[=VALUE] |
522 | --define=NAME[=VALUE] | |
523 | ||
524 | -F NAME[=VALUE] | |
525 | --force-define=NAME[=VALUE] | |
4ecd3681 JD |
526 | |
527 | is equivalent to this grammar file declaration | |
528 | ||
34d41938 | 529 | %define NAME ["VALUE"] |
4ecd3681 | 530 | |
34d41938 JD |
531 | except that the manner in which Bison processes multiple definitions |
532 | for the same NAME differs. Most importantly, -F and --force-define | |
533 | quietly override %define, but -D and --define do not. For further | |
e4ab1254 | 534 | details, see the section "Bison Options" in the Bison manual. |
4ecd3681 | 535 | |
3b1977ea | 536 | *** Variables renamed: |
812775a0 JD |
537 | |
538 | The following %define variables | |
539 | ||
540 | api.push_pull | |
541 | lr.keep_unreachable_states | |
542 | ||
543 | have been renamed to | |
544 | ||
545 | api.push-pull | |
546 | lr.keep-unreachable-states | |
547 | ||
548 | The old names are now deprecated but will be maintained indefinitely | |
549 | for backward compatibility. | |
550 | ||
723206df | 551 | *** Values no longer need to be quoted in the grammar file: |
f37495f6 JD |
552 | |
553 | If a %define value is an identifier, it no longer needs to be placed | |
554 | within quotations marks. For example, | |
555 | ||
556 | %define api.push-pull "push" | |
557 | ||
558 | can be rewritten as | |
559 | ||
560 | %define api.push-pull push | |
561 | ||
6ee881f6 | 562 | *** Unrecognized variables are now errors not warnings. |
c046698e | 563 | |
6ee881f6 JD |
564 | *** Multiple invocations for any variable is now an error not a warning. |
565 | ||
566 | ** Unrecognized %code qualifiers are now errors not warnings. | |
567 | ||
568 | ** Character literals not of length one: | |
569 | ||
570 | Previously, Bison quietly converted all character literals to length | |
571 | one. For example, without warning, Bison interpreted the operators in | |
572 | the following grammar to be the same token: | |
573 | ||
574 | exp: exp '++' | |
575 | | exp '+' exp | |
576 | ; | |
577 | ||
578 | Bison now warns when a character literal is not of length one. In | |
579 | some future release, Bison will start reporting an error instead. | |
580 | ||
581 | ** Destructor calls fixed for lookaheads altered in semantic actions: | |
582 | ||
583 | Previously for deterministic parsers in C, if a user semantic action | |
584 | altered yychar, the parser in some cases used the old yychar value to | |
585 | determine which destructor to call for the lookahead upon a syntax | |
586 | error or upon parser return. This bug has been fixed. | |
587 | ||
588 | ** C++ parsers use YYRHSLOC: | |
589 | ||
590 | Similarly to the C parsers, the C++ parsers now define the YYRHSLOC | |
591 | macro and use it in the default YYLLOC_DEFAULT. You are encouraged | |
e4ab1254 AD |
592 | to use it. If, for instance, your location structure has "first" |
593 | and "last" members, instead of | |
6ee881f6 | 594 | |
e29f0771 AD |
595 | # define YYLLOC_DEFAULT(Current, Rhs, N) \ |
596 | do \ | |
597 | if (N) \ | |
598 | { \ | |
599 | (Current).first = (Rhs)[1].location.first; \ | |
600 | (Current).last = (Rhs)[N].location.last; \ | |
601 | } \ | |
602 | else \ | |
603 | { \ | |
604 | (Current).first = (Current).last = (Rhs)[0].location.last; \ | |
605 | } \ | |
606 | while (false) | |
6ee881f6 JD |
607 | |
608 | use: | |
609 | ||
e29f0771 AD |
610 | # define YYLLOC_DEFAULT(Current, Rhs, N) \ |
611 | do \ | |
612 | if (N) \ | |
613 | { \ | |
614 | (Current).first = YYRHSLOC (Rhs, 1).first; \ | |
615 | (Current).last = YYRHSLOC (Rhs, N).last; \ | |
616 | } \ | |
617 | else \ | |
618 | { \ | |
619 | (Current).first = (Current).last = YYRHSLOC (Rhs, 0).last; \ | |
620 | } \ | |
621 | while (false) | |
6ee881f6 JD |
622 | |
623 | ** YYLLOC_DEFAULT in C++: | |
624 | ||
625 | The default implementation of YYLLOC_DEFAULT used to be issued in | |
626 | the header file. It is now output in the implementation file, after | |
627 | the user %code sections so that its #ifndef guard does not try to | |
628 | override the user's YYLLOC_DEFAULT if provided. | |
c046698e | 629 | |
3b1977ea | 630 | ** YYFAIL now produces warnings and Java parsers no longer implement it: |
62efdd2a JD |
631 | |
632 | YYFAIL has existed for many years as an undocumented feature of | |
633 | deterministic parsers in C generated by Bison. More recently, it was | |
634 | a documented feature of Bison's experimental Java parsers. As | |
635 | promised in Bison 2.4.2's NEWS entry, any appearance of YYFAIL in a | |
636 | semantic action now produces a deprecation warning, and Java parsers | |
637 | no longer implement YYFAIL at all. For further details, including a | |
638 | discussion of how to suppress C preprocessor warnings about YYFAIL | |
639 | being unused, see the Bison 2.4.2 NEWS entry. | |
640 | ||
3b1977ea | 641 | ** Temporary hack for adding a semicolon to the user action: |
a2d05674 JD |
642 | |
643 | Previously, Bison appended a semicolon to every user action for | |
644 | reductions when the output language defaulted to C (specifically, when | |
645 | neither %yacc, %language, %skeleton, or equivalent command-line | |
646 | options were specified). This allowed actions such as | |
647 | ||
648 | exp: exp "+" exp { $$ = $1 + $3 }; | |
649 | ||
650 | instead of | |
651 | ||
652 | exp: exp "+" exp { $$ = $1 + $3; }; | |
653 | ||
654 | As a first step in removing this misfeature, Bison now issues a | |
655 | warning when it appends a semicolon. Moreover, in cases where Bison | |
656 | cannot easily determine whether a semicolon is needed (for example, an | |
657 | action ending with a cpp directive or a braced compound initializer), | |
658 | it no longer appends one. Thus, the C compiler might now complain | |
659 | about a missing semicolon where it did not before. Future releases of | |
660 | Bison will cease to append semicolons entirely. | |
661 | ||
095a1d11 JD |
662 | ** Verbose syntax error message fixes: |
663 | ||
e4ab1254 | 664 | When %error-verbose or the obsolete "#define YYERROR_VERBOSE" is |
6f04ee6c JD |
665 | specified, syntax error messages produced by the generated parser |
666 | include the unexpected token as well as a list of expected tokens. | |
667 | The effect of %nonassoc on these verbose messages has been corrected | |
668 | in two ways, but a more complete fix requires LAC, described above: | |
095a1d11 JD |
669 | |
670 | *** When %nonassoc is used, there can exist parser states that accept no | |
671 | tokens, and so the parser does not always require a lookahead token | |
672 | in order to detect a syntax error. Because no unexpected token or | |
673 | expected tokens can then be reported, the verbose syntax error | |
674 | message described above is suppressed, and the parser instead | |
e4ab1254 | 675 | reports the simpler message, "syntax error". Previously, this |
095a1d11 JD |
676 | suppression was sometimes erroneously triggered by %nonassoc when a |
677 | lookahead was actually required. Now verbose messages are | |
678 | suppressed only when all previous lookaheads have already been | |
679 | shifted or discarded. | |
680 | ||
681 | *** Previously, the list of expected tokens erroneously included tokens | |
682 | that would actually induce a syntax error because conflicts for them | |
683 | were resolved with %nonassoc in the current parser state. Such | |
684 | tokens are now properly omitted from the list. | |
685 | ||
686 | *** Expected token lists are still often wrong due to state merging | |
4c38b19e JD |
687 | (from LALR or IELR) and default reductions, which can both add |
688 | invalid tokens and subtract valid tokens. Canonical LR almost | |
689 | completely fixes this problem by eliminating state merging and | |
690 | default reductions. However, there is one minor problem left even | |
691 | when using canonical LR and even after the fixes above. That is, | |
692 | if the resolution of a conflict with %nonassoc appears in a later | |
693 | parser state than the one at which some syntax error is | |
694 | discovered, the conflicted token is still erroneously included in | |
695 | the expected token list. Bison's new LAC implementation, | |
696 | described above, eliminates this problem and the need for | |
697 | canonical LR. However, LAC is still experimental and is disabled | |
698 | by default. | |
1fa30307 | 699 | |
4c2a6e42 JD |
700 | ** Java skeleton fixes: |
701 | ||
702 | *** A location handling bug has been fixed. | |
703 | ||
704 | *** The top element of each of the value stack and location stack is now | |
705 | cleared when popped so that it can be garbage collected. | |
77768165 | 706 | |
f0e2c228 JD |
707 | *** Parser traces now print the top element of the stack. |
708 | ||
248dba53 JD |
709 | ** -W/--warnings fixes: |
710 | ||
e4ab1254 | 711 | *** Bison now properly recognizes the "no-" versions of categories: |
248dba53 JD |
712 | |
713 | For example, given the following command line, Bison now enables all | |
714 | warnings except warnings for incompatibilities with POSIX Yacc: | |
715 | ||
716 | bison -Wall,no-yacc gram.y | |
717 | ||
6f8bdce2 JD |
718 | *** Bison now treats S/R and R/R conflicts like other warnings: |
719 | ||
720 | Previously, conflict reports were independent of Bison's normal | |
721 | warning system. Now, Bison recognizes the warning categories | |
e4ab1254 | 722 | "conflicts-sr" and "conflicts-rr". This change has important |
6f8bdce2 JD |
723 | consequences for the -W and --warnings command-line options. For |
724 | example: | |
725 | ||
726 | bison -Wno-conflicts-sr gram.y # S/R conflicts not reported | |
727 | bison -Wno-conflicts-rr gram.y # R/R conflicts not reported | |
728 | bison -Wnone gram.y # no conflicts are reported | |
729 | bison -Werror gram.y # any conflict is an error | |
730 | ||
731 | However, as before, if the %expect or %expect-rr directive is | |
732 | specified, an unexpected number of conflicts is an error, and an | |
733 | expected number of conflicts is not reported, so -W and --warning | |
734 | then have no effect on the conflict report. | |
735 | ||
e4ab1254 | 736 | *** The "none" category no longer disables a preceding "error": |
dab96632 JD |
737 | |
738 | For example, for the following command line, Bison now reports | |
739 | errors instead of warnings for incompatibilities with POSIX Yacc: | |
740 | ||
741 | bison -Werror,none,yacc gram.y | |
742 | ||
e4ab1254 | 743 | *** The "none" category now disables all Bison warnings: |
8ffd7912 | 744 | |
e4ab1254 | 745 | Previously, the "none" category disabled only Bison warnings for |
8ffd7912 JD |
746 | which there existed a specific -W/--warning category. However, |
747 | given the following command line, Bison is now guaranteed to | |
748 | suppress all warnings: | |
749 | ||
750 | bison -Wnone gram.y | |
751 | ||
9d6af153 JD |
752 | ** Precedence directives can now assign token number 0: |
753 | ||
754 | Since Bison 2.3b, which restored the ability of precedence | |
755 | directives to assign token numbers, doing so for token number 0 has | |
756 | produced an assertion failure. For example: | |
757 | ||
758 | %left END 0 | |
759 | ||
760 | This bug has been fixed. | |
761 | ||
7527c744 | 762 | * Changes in version 2.4.3 (2010-08-05): |
7a9c3cb3 | 763 | |
4631c34f JD |
764 | ** Bison now obeys -Werror and --warnings=error for warnings about |
765 | grammar rules that are useless in the parser due to conflicts. | |
766 | ||
7a9c3cb3 JD |
767 | ** Problems with spawning M4 on at least FreeBSD 8 and FreeBSD 9 have |
768 | been fixed. | |
769 | ||
132247cd JD |
770 | ** Failures in the test suite for GCC 4.5 have been fixed. |
771 | ||
88bb35d6 JD |
772 | ** Failures in the test suite for some versions of Sun Studio C++ have |
773 | been fixed. | |
774 | ||
43fdc9fd JD |
775 | ** Contrary to Bison 2.4.2's NEWS entry, it has been decided that |
776 | warnings about undefined %prec identifiers will not be converted to | |
777 | errors in Bison 2.5. They will remain warnings, which should be | |
778 | sufficient for POSIX while avoiding backward compatibility issues. | |
779 | ||
cf22447c JD |
780 | ** Minor documentation fixes. |
781 | ||
ea66d039 | 782 | * Changes in version 2.4.2 (2010-03-20): |
8defe11b | 783 | |
47fa5747 JD |
784 | ** Some portability problems that resulted in failures and livelocks |
785 | in the test suite on some versions of at least Solaris, AIX, HP-UX, | |
ea66d039 JD |
786 | RHEL4, and Tru64 have been addressed. As a result, fatal Bison |
787 | errors should no longer cause M4 to report a broken pipe on the | |
47fa5747 JD |
788 | affected platforms. |
789 | ||
e4ab1254 | 790 | ** "%prec IDENTIFIER" requires IDENTIFIER to be defined separately. |
2c203528 JD |
791 | |
792 | POSIX specifies that an error be reported for any identifier that does | |
793 | not appear on the LHS of a grammar rule and that is not defined by | |
794 | %token, %left, %right, or %nonassoc. Bison 2.3b and later lost this | |
795 | error report for the case when an identifier appears only after a | |
796 | %prec directive. It is now restored. However, for backward | |
797 | compatibility with recent Bison releases, it is only a warning for | |
798 | now. In Bison 2.5 and later, it will return to being an error. | |
43fdc9fd JD |
799 | [Between the 2.4.2 and 2.4.3 releases, it was decided that this |
800 | warning will not be converted to an error in Bison 2.5.] | |
2c203528 | 801 | |
c5196098 EB |
802 | ** Detection of GNU M4 1.4.6 or newer during configure is improved. |
803 | ||
34731471 JD |
804 | ** Warnings from gcc's -Wundef option about undefined YYENABLE_NLS, |
805 | YYLTYPE_IS_TRIVIAL, and __STRICT_ANSI__ in C/C++ parsers are now | |
806 | avoided. | |
af2ffe5c | 807 | |
966aba65 JD |
808 | ** %code is now a permanent feature. |
809 | ||
810 | A traditional Yacc prologue directive is written in the form: | |
811 | ||
812 | %{CODE%} | |
813 | ||
814 | To provide a more flexible alternative, Bison 2.3b introduced the | |
815 | %code directive with the following forms for C/C++: | |
816 | ||
817 | %code {CODE} | |
818 | %code requires {CODE} | |
819 | %code provides {CODE} | |
820 | %code top {CODE} | |
821 | ||
822 | These forms are now considered permanent features of Bison. See the | |
823 | %code entries in the section "Bison Declaration Summary" in the Bison | |
824 | manual for a summary of their functionality. See the section | |
825 | "Prologue Alternatives" for a detailed discussion including the | |
826 | advantages of %code over the traditional Yacc prologue directive. | |
827 | ||
828 | Bison's Java feature as a whole including its current usage of %code | |
829 | is still considered experimental. | |
830 | ||
41d35e54 JD |
831 | ** YYFAIL is deprecated and will eventually be removed. |
832 | ||
833 | YYFAIL has existed for many years as an undocumented feature of | |
834 | deterministic parsers in C generated by Bison. Previously, it was | |
835 | documented for Bison's experimental Java parsers. YYFAIL is no longer | |
836 | documented for Java parsers and is formally deprecated in both cases. | |
837 | Users are strongly encouraged to migrate to YYERROR, which is | |
838 | specified by POSIX. | |
839 | ||
840 | Like YYERROR, you can invoke YYFAIL from a semantic action in order to | |
841 | induce a syntax error. The most obvious difference from YYERROR is | |
842 | that YYFAIL will automatically invoke yyerror to report the syntax | |
843 | error so that you don't have to. However, there are several other | |
844 | subtle differences between YYERROR and YYFAIL, and YYFAIL suffers from | |
e4ab1254 | 845 | inherent flaws when %error-verbose or "#define YYERROR_VERBOSE" is |
41d35e54 JD |
846 | used. For a more detailed discussion, see: |
847 | ||
848 | http://lists.gnu.org/archive/html/bison-patches/2009-12/msg00024.html | |
849 | ||
850 | The upcoming Bison 2.5 will remove YYFAIL from Java parsers, but | |
851 | deterministic parsers in C will continue to implement it. However, | |
852 | because YYFAIL is already flawed, it seems futile to try to make new | |
853 | Bison features compatible with it. Thus, during parser generation, | |
854 | Bison 2.5 will produce a warning whenever it discovers YYFAIL in a | |
855 | rule action. In a later release, YYFAIL will be disabled for | |
e4ab1254 | 856 | %error-verbose and "#define YYERROR_VERBOSE". Eventually, YYFAIL will |
41d35e54 JD |
857 | be removed altogether. |
858 | ||
859 | There exists at least one case where Bison 2.5's YYFAIL warning will | |
860 | be a false positive. Some projects add phony uses of YYFAIL and other | |
861 | Bison-defined macros for the sole purpose of suppressing C | |
862 | preprocessor warnings (from GCC cpp's -Wunused-macros, for example). | |
863 | To avoid Bison's future warning, such YYFAIL uses can be moved to the | |
e4ab1254 | 864 | epilogue (that is, after the second "%%") in the Bison input file. In |
41d35e54 JD |
865 | this release (2.4.2), Bison already generates its own code to suppress |
866 | C preprocessor warnings for YYFAIL, so projects can remove their own | |
867 | phony uses of YYFAIL if compatibility with Bison releases prior to | |
868 | 2.4.2 is not necessary. | |
869 | ||
dac8cc0d AD |
870 | ** Internationalization. |
871 | ||
872 | Fix a regression introduced in Bison 2.4: Under some circumstances, | |
873 | message translations were not installed although supported by the | |
874 | host system. | |
875 | ||
41930e7a | 876 | * Changes in version 2.4.1 (2008-12-11): |
c9ba9e59 | 877 | |
a957d06c JD |
878 | ** In the GLR defines file, unexpanded M4 macros in the yylval and yylloc |
879 | declarations have been fixed. | |
880 | ||
738cde3e AD |
881 | ** Temporary hack for adding a semicolon to the user action. |
882 | ||
883 | Bison used to prepend a trailing semicolon at the end of the user | |
884 | action for reductions. This allowed actions such as | |
885 | ||
886 | exp: exp "+" exp { $$ = $1 + $3 }; | |
887 | ||
888 | instead of | |
889 | ||
890 | exp: exp "+" exp { $$ = $1 + $3; }; | |
891 | ||
e4ab1254 | 892 | Some grammars still depend on this "feature". Bison 2.4.1 restores |
d07932ef JD |
893 | the previous behavior in the case of C output (specifically, when |
894 | neither %language or %skeleton or equivalent command-line options | |
895 | are used) to leave more time for grammars depending on the old | |
896 | behavior to be adjusted. Future releases of Bison will disable this | |
897 | feature. | |
a957d06c JD |
898 | |
899 | ** A few minor improvements to the Bison manual. | |
c9ba9e59 | 900 | |
d6fb461d | 901 | * Changes in version 2.4 (2008-11-02): |
7bd1665a | 902 | |
d6fb461d | 903 | ** %language is an experimental feature. |
ed4d67dc JD |
904 | |
905 | We first introduced this feature in test release 2.3b as a cleaner | |
906 | alternative to %skeleton. Since then, we have discussed the possibility of | |
907 | modifying its effect on Bison's output file names. Thus, in this release, | |
908 | we consider %language to be an experimental feature that will likely evolve | |
909 | in future releases. | |
7bd1665a | 910 | |
d6fb461d | 911 | ** Forward compatibility with GNU M4 has been improved. |
241fda7a | 912 | |
d6fb461d | 913 | ** Several bugs in the C++ skeleton and the experimental Java skeleton have been |
241fda7a JD |
914 | fixed. |
915 | ||
d6fb461d | 916 | * Changes in version 2.3b (2008-05-27): |
35fe0834 | 917 | |
d6fb461d | 918 | ** The quotes around NAME that used to be required in the following directive |
d9df47b6 JD |
919 | are now deprecated: |
920 | ||
921 | %define NAME "VALUE" | |
922 | ||
e4ab1254 | 923 | ** The directive "%pure-parser" is now deprecated in favor of: |
d9df47b6 JD |
924 | |
925 | %define api.pure | |
926 | ||
927 | which has the same effect except that Bison is more careful to warn about | |
928 | unreasonable usage in the latter case. | |
929 | ||
d6fb461d | 930 | ** Push Parsing |
c373bf8b JD |
931 | |
932 | Bison can now generate an LALR(1) parser in C with a push interface. That | |
e4ab1254 AD |
933 | is, instead of invoking "yyparse", which pulls tokens from "yylex", you can |
934 | push one token at a time to the parser using "yypush_parse", which will | |
c373bf8b JD |
935 | return to the caller after processing each token. By default, the push |
936 | interface is disabled. Either of the following directives will enable it: | |
937 | ||
938 | %define api.push_pull "push" // Just push; does not require yylex. | |
939 | %define api.push_pull "both" // Push and pull; requires yylex. | |
940 | ||
e4ab1254 | 941 | See the new section "A Push Parser" in the Bison manual for details. |
c373bf8b | 942 | |
59da312b JD |
943 | The current push parsing interface is experimental and may evolve. More user |
944 | feedback will help to stabilize it. | |
945 | ||
d6fb461d | 946 | ** The -g and --graph options now output graphs in Graphviz DOT format, |
8e55b3aa JD |
947 | not VCG format. Like --graph, -g now also takes an optional FILE argument |
948 | and thus cannot be bundled with other short options. | |
c373bf8b | 949 | |
d6fb461d | 950 | ** Java |
59da312b JD |
951 | |
952 | Bison can now generate an LALR(1) parser in Java. The skeleton is | |
e4ab1254 | 953 | "data/lalr1.java". Consider using the new %language directive instead of |
59da312b JD |
954 | %skeleton to select it. |
955 | ||
e4ab1254 | 956 | See the new section "Java Parsers" in the Bison manual for details. |
59da312b JD |
957 | |
958 | The current Java interface is experimental and may evolve. More user | |
959 | feedback will help to stabilize it. | |
960 | ||
d6fb461d | 961 | ** %language |
59da312b JD |
962 | |
963 | This new directive specifies the programming language of the generated | |
d43f77e7 PB |
964 | parser, which can be C (the default), C++, or Java. Besides the skeleton |
965 | that Bison uses, the directive affects the names of the generated files if | |
966 | the grammar file's name ends in ".y". | |
59da312b | 967 | |
d6fb461d | 968 | ** XML Automaton Report |
59da312b JD |
969 | |
970 | Bison can now generate an XML report of the LALR(1) automaton using the new | |
e4ab1254 | 971 | "--xml" option. The current XML schema is experimental and may evolve. More |
59da312b | 972 | user feedback will help to stabilize it. |
c373bf8b | 973 | |
d6fb461d | 974 | ** The grammar file may now specify the name of the parser header file using |
c373bf8b JD |
975 | %defines. For example: |
976 | ||
977 | %defines "parser.h" | |
978 | ||
d6fb461d | 979 | ** When reporting useless rules, useless nonterminals, and unused terminals, |
d80fb37a JD |
980 | Bison now employs the terms "useless in grammar" instead of "useless", |
981 | "useless in parser" instead of "never reduced", and "unused in grammar" | |
982 | instead of "unused". | |
cff03fb2 | 983 | |
d6fb461d | 984 | ** Unreachable State Removal |
c373bf8b JD |
985 | |
986 | Previously, Bison sometimes generated parser tables containing unreachable | |
31984206 JD |
987 | states. A state can become unreachable during conflict resolution if Bison |
988 | disables a shift action leading to it from a predecessor state. Bison now: | |
75ad86ee JD |
989 | |
990 | 1. Removes unreachable states. | |
991 | ||
992 | 2. Does not report any conflicts that appeared in unreachable states. | |
993 | WARNING: As a result, you may need to update %expect and %expect-rr | |
994 | directives in existing grammar files. | |
995 | ||
996 | 3. For any rule used only in such states, Bison now reports the rule as | |
cff03fb2 | 997 | "useless in parser due to conflicts". |
75ad86ee | 998 | |
31984206 JD |
999 | This feature can be disabled with the following directive: |
1000 | ||
1001 | %define lr.keep_unreachable_states | |
1002 | ||
e4ab1254 | 1003 | See the %define entry in the "Bison Declaration Summary" in the Bison manual |
31984206 JD |
1004 | for further discussion. |
1005 | ||
e4ab1254 | 1006 | ** Lookahead Set Correction in the ".output" Report |
b1cc23c4 | 1007 | |
e4ab1254 AD |
1008 | When instructed to generate a ".output" file including lookahead sets |
1009 | (using "--report=lookahead", for example), Bison now prints each reduction's | |
88c78747 JD |
1010 | lookahead set only next to the associated state's one item that (1) is |
1011 | associated with the same rule as the reduction and (2) has its dot at the end | |
1012 | of its RHS. Previously, Bison also erroneously printed the lookahead set | |
1013 | next to all of the state's other items associated with the same rule. This | |
e4ab1254 | 1014 | bug affected only the ".output" file and not the generated parser source |
88c78747 JD |
1015 | code. |
1016 | ||
e4ab1254 | 1017 | ** --report-file=FILE is a new option to override the default ".output" file |
59da312b | 1018 | name. |
1bb2bd75 | 1019 | |
e4ab1254 | 1020 | ** The "=" that used to be required in the following directives is now |
02975b9a JD |
1021 | deprecated: |
1022 | ||
1023 | %file-prefix "parser" | |
1024 | %name-prefix "c_" | |
1025 | %output "parser.c" | |
1026 | ||
e4ab1254 | 1027 | ** An Alternative to "%{...%}" -- "%code QUALIFIER {CODE}" |
c373bf8b JD |
1028 | |
1029 | Bison 2.3a provided a new set of directives as a more flexible alternative to | |
8e0a5e9e JD |
1030 | the traditional Yacc prologue blocks. Those have now been consolidated into |
1031 | a single %code directive with an optional qualifier field, which identifies | |
1032 | the purpose of the code and thus the location(s) where Bison should generate | |
1033 | it: | |
1034 | ||
e4ab1254 AD |
1035 | 1. "%code {CODE}" replaces "%after-header {CODE}" |
1036 | 2. "%code requires {CODE}" replaces "%start-header {CODE}" | |
1037 | 3. "%code provides {CODE}" replaces "%end-header {CODE}" | |
1038 | 4. "%code top {CODE}" replaces "%before-header {CODE}" | |
8e0a5e9e | 1039 | |
e4ab1254 AD |
1040 | See the %code entries in section "Bison Declaration Summary" in the Bison |
1041 | manual for a summary of the new functionality. See the new section "Prologue | |
1042 | Alternatives" for a detailed discussion including the advantages of %code | |
8e0a5e9e JD |
1043 | over the traditional Yacc prologues. |
1044 | ||
1045 | The prologue alternatives are experimental. More user feedback will help to | |
1046 | determine whether they should become permanent features. | |
1047 | ||
d6fb461d | 1048 | ** Revised warning: unset or unused mid-rule values |
17bd8a73 JD |
1049 | |
1050 | Since Bison 2.2, Bison has warned about mid-rule values that are set but not | |
1051 | used within any of the actions of the parent rule. For example, Bison warns | |
1052 | about unused $2 in: | |
1053 | ||
1054 | exp: '1' { $$ = 1; } '+' exp { $$ = $1 + $4; }; | |
1055 | ||
1056 | Now, Bison also warns about mid-rule values that are used but not set. For | |
1057 | example, Bison warns about unset $$ in the mid-rule action in: | |
1058 | ||
1059 | exp: '1' { $1 = 1; } '+' exp { $$ = $2 + $4; }; | |
1060 | ||
1061 | However, Bison now disables both of these warnings by default since they | |
1062 | sometimes prove to be false alarms in existing grammars employing the Yacc | |
1063 | constructs $0 or $-N (where N is some positive integer). | |
1064 | ||
e4ab1254 AD |
1065 | To enable these warnings, specify the option "--warnings=midrule-values" or |
1066 | "-W", which is a synonym for "--warnings=all". | |
17bd8a73 | 1067 | |
e4ab1254 | 1068 | ** Default %destructor or %printer with "<*>" or "<>" |
c373bf8b JD |
1069 | |
1070 | Bison now recognizes two separate kinds of default %destructor's and | |
12e35840 JD |
1071 | %printer's: |
1072 | ||
e4ab1254 | 1073 | 1. Place "<*>" in a %destructor/%printer symbol list to define a default |
12e35840 JD |
1074 | %destructor/%printer for all grammar symbols for which you have formally |
1075 | declared semantic type tags. | |
1076 | ||
e4ab1254 | 1077 | 2. Place "<>" in a %destructor/%printer symbol list to define a default |
12e35840 JD |
1078 | %destructor/%printer for all grammar symbols without declared semantic |
1079 | type tags. | |
1080 | ||
e4ab1254 AD |
1081 | Bison no longer supports the "%symbol-default" notation from Bison 2.3a. |
1082 | "<*>" and "<>" combined achieve the same effect with one exception: Bison no | |
12e35840 JD |
1083 | longer applies any %destructor to a mid-rule value if that mid-rule value is |
1084 | not actually ever referenced using either $$ or $n in a semantic action. | |
1085 | ||
85894313 JD |
1086 | The default %destructor's and %printer's are experimental. More user |
1087 | feedback will help to determine whether they should become permanent | |
1088 | features. | |
1089 | ||
e4ab1254 | 1090 | See the section "Freeing Discarded Symbols" in the Bison manual for further |
12e35840 JD |
1091 | details. |
1092 | ||
d6fb461d | 1093 | ** %left, %right, and %nonassoc can now declare token numbers. This is required |
e4ab1254 | 1094 | by POSIX. However, see the end of section "Operator Precedence" in the Bison |
ab7f29f8 JD |
1095 | manual for a caveat concerning the treatment of literal strings. |
1096 | ||
d6fb461d | 1097 | ** The nonfunctional --no-parser, -n, and %no-parser options have been |
b1cc23c4 JD |
1098 | completely removed from Bison. |
1099 | ||
d6fb461d | 1100 | * Changes in version 2.3a, 2006-09-13: |
742e4900 | 1101 | |
d6fb461d | 1102 | ** Instead of %union, you can define and use your own union type |
ddc8ede1 PE |
1103 | YYSTYPE if your grammar contains at least one <type> tag. |
1104 | Your YYSTYPE need not be a macro; it can be a typedef. | |
1105 | This change is for compatibility with other Yacc implementations, | |
1106 | and is required by POSIX. | |
1107 | ||
d6fb461d | 1108 | ** Locations columns and lines start at 1. |
cd48d21d AD |
1109 | In accordance with the GNU Coding Standards and Emacs. |
1110 | ||
d6fb461d | 1111 | ** You may now declare per-type and default %destructor's and %printer's: |
ec5479ce JD |
1112 | |
1113 | For example: | |
1114 | ||
b2a0b7ca JD |
1115 | %union { char *string; } |
1116 | %token <string> STRING1 | |
1117 | %token <string> STRING2 | |
1118 | %type <string> string1 | |
1119 | %type <string> string2 | |
1120 | %union { char character; } | |
1121 | %token <character> CHR | |
1122 | %type <character> chr | |
1123 | %destructor { free ($$); } %symbol-default | |
1124 | %destructor { free ($$); printf ("%d", @$.first_line); } STRING1 string1 | |
1125 | %destructor { } <character> | |
1126 | ||
1127 | guarantees that, when the parser discards any user-defined symbol that has a | |
e4ab1254 AD |
1128 | semantic type tag other than "<character>", it passes its semantic value to |
1129 | "free". However, when the parser discards a "STRING1" or a "string1", it | |
1130 | also prints its line number to "stdout". It performs only the second | |
1131 | "%destructor" in this case, so it invokes "free" only once. | |
ec5479ce | 1132 | |
85894313 JD |
1133 | [Although we failed to mention this here in the 2.3a release, the default |
1134 | %destructor's and %printer's were experimental, and they were rewritten in | |
1135 | future versions.] | |
1136 | ||
e4ab1254 AD |
1137 | ** Except for LALR(1) parsers in C with POSIX Yacc emulation enabled (with "-y", |
1138 | "--yacc", or "%yacc"), Bison no longer generates #define statements for | |
b931235e JD |
1139 | associating token numbers with token names. Removing the #define statements |
1140 | helps to sanitize the global namespace during preprocessing, but POSIX Yacc | |
1141 | requires them. Bison still generates an enum for token names in all cases. | |
1142 | ||
d6fb461d | 1143 | ** Handling of traditional Yacc prologue blocks is now more consistent but |
34f98f46 | 1144 | potentially incompatible with previous releases of Bison. |
9bc0dd67 JD |
1145 | |
1146 | As before, you declare prologue blocks in your grammar file with the | |
e4ab1254 | 1147 | "%{ ... %}" syntax. To generate the pre-prologue, Bison concatenates all |
34f98f46 JD |
1148 | prologue blocks that you've declared before the first %union. To generate |
1149 | the post-prologue, Bison concatenates all prologue blocks that you've | |
ddc8ede1 | 1150 | declared after the first %union. |
9bc0dd67 | 1151 | |
34f98f46 | 1152 | Previous releases of Bison inserted the pre-prologue into both the header |
9bc0dd67 JD |
1153 | file and the code file in all cases except for LALR(1) parsers in C. In the |
1154 | latter case, Bison inserted it only into the code file. For parsers in C++, | |
1155 | the point of insertion was before any token definitions (which associate | |
1156 | token numbers with names). For parsers in C, the point of insertion was | |
1157 | after the token definitions. | |
1158 | ||
1159 | Now, Bison never inserts the pre-prologue into the header file. In the code | |
1160 | file, it always inserts it before the token definitions. | |
1161 | ||
d6fb461d | 1162 | ** Bison now provides a more flexible alternative to the traditional Yacc |
34f98f46 JD |
1163 | prologue blocks: %before-header, %start-header, %end-header, and |
1164 | %after-header. | |
1165 | ||
1166 | For example, the following declaration order in the grammar file reflects the | |
1167 | order in which Bison will output these code blocks. However, you are free to | |
1168 | declare these code blocks in your grammar file in whatever order is most | |
1169 | convenient for you: | |
1170 | ||
1171 | %before-header { | |
1172 | /* Bison treats this block like a pre-prologue block: it inserts it into | |
1173 | * the code file before the contents of the header file. It does *not* | |
1174 | * insert it into the header file. This is a good place to put | |
1175 | * #include's that you want at the top of your code file. A common | |
e4ab1254 | 1176 | * example is '#include "system.h"'. */ |
34f98f46 JD |
1177 | } |
1178 | %start-header { | |
1179 | /* Bison inserts this block into both the header file and the code file. | |
1180 | * In both files, the point of insertion is before any Bison-generated | |
1181 | * token, semantic type, location type, and class definitions. This is a | |
1182 | * good place to define %union dependencies, for example. */ | |
9bc0dd67 JD |
1183 | } |
1184 | %union { | |
34f98f46 JD |
1185 | /* Unlike the traditional Yacc prologue blocks, the output order for the |
1186 | * new %*-header blocks is not affected by their declaration position | |
1187 | * relative to any %union in the grammar file. */ | |
9bc0dd67 | 1188 | } |
34f98f46 JD |
1189 | %end-header { |
1190 | /* Bison inserts this block into both the header file and the code file. | |
1191 | * In both files, the point of insertion is after the Bison-generated | |
1192 | * definitions. This is a good place to declare or define public | |
1193 | * functions or data structures that depend on the Bison-generated | |
1194 | * definitions. */ | |
9bc0dd67 | 1195 | } |
34f98f46 JD |
1196 | %after-header { |
1197 | /* Bison treats this block like a post-prologue block: it inserts it into | |
1198 | * the code file after the contents of the header file. It does *not* | |
1199 | * insert it into the header file. This is a good place to declare or | |
1200 | * define internal functions or data structures that depend on the | |
1201 | * Bison-generated definitions. */ | |
1202 | } | |
1203 | ||
1204 | If you have multiple occurrences of any one of the above declarations, Bison | |
1205 | will concatenate the contents in declaration order. | |
9bc0dd67 | 1206 | |
85894313 JD |
1207 | [Although we failed to mention this here in the 2.3a release, the prologue |
1208 | alternatives were experimental, and they were rewritten in future versions.] | |
1209 | ||
e4ab1254 | 1210 | ** The option "--report=look-ahead" has been changed to "--report=lookahead". |
9e6e7ed2 PE |
1211 | The old spelling still works, but is not documented and may be removed |
1212 | in a future release. | |
742e4900 | 1213 | |
d6fb461d | 1214 | * Changes in version 2.3, 2006-06-05: |
4ad3ed84 | 1215 | |
e4ab1254 | 1216 | ** GLR grammars should now use "YYRECOVERING ()" instead of "YYRECOVERING", |
4ad3ed84 PE |
1217 | for compatibility with LALR(1) grammars. |
1218 | ||
d6fb461d | 1219 | ** It is now documented that any definition of YYSTYPE or YYLTYPE should |
4ad3ed84 PE |
1220 | be to a type name that does not contain parentheses or brackets. |
1221 | ||
d6fb461d | 1222 | * Changes in version 2.2, 2006-05-19: |
193d7c70 | 1223 | |
d6fb461d | 1224 | ** The distribution terms for all Bison-generated parsers now permit |
193d7c70 PE |
1225 | using the parsers in nonfree programs. Previously, this permission |
1226 | was granted only for Bison-generated LALR(1) parsers in C. | |
5f4236a0 | 1227 | |
d6fb461d | 1228 | ** %name-prefix changes the namespace name in C++ outputs. |
aa08666d | 1229 | |
d6fb461d | 1230 | ** The C++ parsers export their token_type. |
5f4236a0 | 1231 | |
d6fb461d | 1232 | ** Bison now allows multiple %union declarations, and concatenates |
d6ca7905 PE |
1233 | their contents together. |
1234 | ||
d6fb461d | 1235 | ** New warning: unused values |
4d7bc38c PE |
1236 | Right-hand side symbols whose values are not used are reported, |
1237 | if the symbols have destructors. For instance: | |
affac613 | 1238 | |
8f3596a6 | 1239 | exp: exp "?" exp ":" exp { $1 ? $1 : $3; } |
e29f0771 AD |
1240 | | exp "+" exp |
1241 | ; | |
affac613 | 1242 | |
8f3596a6 AD |
1243 | will trigger a warning about $$ and $5 in the first rule, and $3 in |
1244 | the second ($1 is copied to $$ by the default rule). This example | |
4e26c69e | 1245 | most likely contains three errors, and could be rewritten as: |
affac613 | 1246 | |
4e26c69e | 1247 | exp: exp "?" exp ":" exp |
e29f0771 AD |
1248 | { $$ = $1 ? $3 : $5; free ($1 ? $5 : $3); free ($1); } |
1249 | | exp "+" exp | |
1250 | { $$ = $1 ? $1 : $3; if ($1) free ($3); } | |
1251 | ; | |
affac613 | 1252 | |
4e26c69e PE |
1253 | However, if the original actions were really intended, memory leaks |
1254 | and all, the warnings can be suppressed by letting Bison believe the | |
1255 | values are used, e.g.: | |
721be13c | 1256 | |
8f3596a6 | 1257 | exp: exp "?" exp ":" exp { $1 ? $1 : $3; (void) ($$, $5); } |
e29f0771 AD |
1258 | | exp "+" exp { $$ = $1; (void) $3; } |
1259 | ; | |
721be13c | 1260 | |
84866159 AD |
1261 | If there are mid-rule actions, the warning is issued if no action |
1262 | uses it. The following triggers no warning: $1 and $3 are used. | |
1263 | ||
1264 | exp: exp { push ($1); } '+' exp { push ($3); sum (); }; | |
1265 | ||
721be13c PE |
1266 | The warning is intended to help catching lost values and memory leaks. |
1267 | If a value is ignored, its associated memory typically is not reclaimed. | |
affac613 | 1268 | |
d6fb461d | 1269 | ** %destructor vs. YYABORT, YYACCEPT, and YYERROR. |
9d9b8b70 PE |
1270 | Destructors are now called when user code invokes YYABORT, YYACCEPT, |
1271 | and YYERROR, for all objects on the stack, other than objects | |
1272 | corresponding to the right-hand side of the current rule. | |
a85284cf | 1273 | |
d6fb461d | 1274 | ** %expect, %expect-rr |
035aa4a0 PE |
1275 | Incorrect numbers of expected conflicts are now actual errors, |
1276 | instead of warnings. | |
1277 | ||
d6fb461d | 1278 | ** GLR, YACC parsers. |
4e26c69e PE |
1279 | The %parse-params are available in the destructors (and the |
1280 | experimental printers) as per the documentation. | |
4b367315 | 1281 | |
e4ab1254 | 1282 | ** Bison now warns if it finds a stray "$" or "@" in an action. |
ad6a9b97 | 1283 | |
d6fb461d | 1284 | ** %require "VERSION" |
4e26c69e PE |
1285 | This specifies that the grammar file depends on features implemented |
1286 | in Bison version VERSION or higher. | |
b50d2359 | 1287 | |
d6fb461d | 1288 | ** lalr1.cc: The token and value types are now class members. |
e14d0ab6 AD |
1289 | The tokens were defined as free form enums and cpp macros. YYSTYPE |
1290 | was defined as a free form union. They are now class members: | |
e4ab1254 AD |
1291 | tokens are enumerations of the "yy::parser::token" struct, and the |
1292 | semantic values have the "yy::parser::semantic_type" type. | |
fb9712a9 AD |
1293 | |
1294 | If you do not want or can update to this scheme, the directive | |
e4ab1254 | 1295 | '%define "global_tokens_and_yystype" "1"' triggers the global |
b50d2359 AD |
1296 | definition of tokens and YYSTYPE. This change is suitable both |
1297 | for previous releases of Bison, and this one. | |
fb9712a9 | 1298 | |
b50d2359 | 1299 | If you wish to update, then make sure older version of Bison will |
e4ab1254 | 1300 | fail using '%require "2.2"'. |
fb9712a9 | 1301 | |
d6fb461d | 1302 | ** DJGPP support added. |
193d7c70 | 1303 | \f |
d6fb461d | 1304 | * Changes in version 2.1, 2005-09-16: |
1ce59070 | 1305 | |
d6fb461d | 1306 | ** The C++ lalr1.cc skeleton supports %lex-param. |
e14d0ab6 | 1307 | |
d6fb461d | 1308 | ** Bison-generated parsers now support the translation of diagnostics like |
baf785db PE |
1309 | "syntax error" into languages other than English. The default |
1310 | language is still English. For details, please see the new | |
0410a6e0 PE |
1311 | Internationalization section of the Bison manual. Software |
1312 | distributors should also see the new PACKAGING file. Thanks to | |
1313 | Bruno Haible for this new feature. | |
1ce59070 | 1314 | |
d6fb461d | 1315 | ** Wording in the Bison-generated parsers has been changed slightly to |
1a059451 PE |
1316 | simplify translation. In particular, the message "memory exhausted" |
1317 | has replaced "parser stack overflow", as the old message was not | |
1318 | always accurate for modern Bison-generated parsers. | |
1319 | ||
d6fb461d | 1320 | ** Destructors are now called when the parser aborts, for all symbols left |
258b75ca PE |
1321 | behind on the stack. Also, the start symbol is now destroyed after a |
1322 | successful parse. In both cases, the behavior was formerly inconsistent. | |
1323 | ||
d6fb461d | 1324 | ** When generating verbose diagnostics, Bison-generated parsers no longer |
72f000b0 PE |
1325 | quote the literal strings associated with tokens. For example, for |
1326 | a syntax error associated with '%token NUM "number"' they might | |
1327 | print 'syntax error, unexpected number' instead of 'syntax error, | |
1328 | unexpected "number"'. | |
193d7c70 | 1329 | \f |
d6fb461d | 1330 | * Changes in version 2.0, 2004-12-25: |
efeed023 | 1331 | |
d6fb461d | 1332 | ** Possibly-incompatible changes |
d7e14fc0 | 1333 | |
82de6b0d PE |
1334 | - Bison-generated parsers no longer default to using the alloca function |
1335 | (when available) to extend the parser stack, due to widespread | |
1336 | problems in unchecked stack-overflow detection. You can "#define | |
1337 | YYSTACK_USE_ALLOCA 1" to require the use of alloca, but please read | |
1338 | the manual to determine safe values for YYMAXDEPTH in that case. | |
8dd162d3 | 1339 | |
82de6b0d PE |
1340 | - Error token location. |
1341 | During error recovery, the location of the syntax error is updated | |
1342 | to cover the whole sequence covered by the error token: it includes | |
1343 | the shifted symbols thrown away during the first part of the error | |
1344 | recovery, and the lookahead rejected during the second part. | |
18d192f0 | 1345 | |
82de6b0d PE |
1346 | - Semicolon changes: |
1347 | . Stray semicolons are no longer allowed at the start of a grammar. | |
1348 | . Semicolons are now required after in-grammar declarations. | |
e342c3be | 1349 | |
82de6b0d PE |
1350 | - Unescaped newlines are no longer allowed in character constants or |
1351 | string literals. They were never portable, and GCC 3.4.0 has | |
1352 | dropped support for them. Better diagnostics are now generated if | |
1353 | forget a closing quote. | |
8dd162d3 | 1354 | |
82de6b0d | 1355 | - NUL bytes are no longer allowed in Bison string literals, unfortunately. |
f74b6f91 | 1356 | |
d6fb461d | 1357 | ** New features |
1452af69 | 1358 | |
82de6b0d | 1359 | - GLR grammars now support locations. |
4febdd96 | 1360 | |
82de6b0d PE |
1361 | - New directive: %initial-action. |
1362 | This directive allows the user to run arbitrary code (including | |
1363 | initializing @$) from yyparse before parsing starts. | |
1452af69 | 1364 | |
82de6b0d PE |
1365 | - A new directive "%expect-rr N" specifies the expected number of |
1366 | reduce/reduce conflicts in GLR parsers. | |
1452af69 | 1367 | |
e4ab1254 | 1368 | - %token numbers can now be hexadecimal integers, e.g., "%token FOO 0x12d". |
82de6b0d | 1369 | This is a GNU extension. |
4febdd96 | 1370 | |
e4ab1254 | 1371 | - The option "--report=lookahead" was changed to "--report=look-ahead". |
9e6e7ed2 | 1372 | [However, this was changed back after 2.3.] |
1452af69 | 1373 | |
82de6b0d | 1374 | - Experimental %destructor support has been added to lalr1.cc. |
1452af69 | 1375 | |
82de6b0d PE |
1376 | - New configure option --disable-yacc, to disable installation of the |
1377 | yacc command and -ly library introduced in 1.875 for POSIX conformance. | |
6040d338 | 1378 | |
d6fb461d | 1379 | ** Bug fixes |
d5a3fe37 | 1380 | |
82de6b0d PE |
1381 | - For now, %expect-count violations are now just warnings, not errors. |
1382 | This is for compatibility with Bison 1.75 and earlier (when there are | |
1383 | reduce/reduce conflicts) and with Bison 1.30 and earlier (when there | |
1384 | are too many or too few shift/reduce conflicts). However, in future | |
1385 | versions of Bison we plan to improve the %expect machinery so that | |
1386 | these violations will become errors again. | |
3473d0f8 | 1387 | |
82de6b0d PE |
1388 | - Within Bison itself, numbers (e.g., goto numbers) are no longer |
1389 | arbitrarily limited to 16-bit counts. | |
d600ee67 | 1390 | |
82de6b0d | 1391 | - Semicolons are now allowed before "|" in grammar rules, as POSIX requires. |
d600ee67 | 1392 | \f |
d6fb461d | 1393 | * Changes in version 1.875, 2003-01-01: |
963fcc17 | 1394 | |
d6fb461d | 1395 | ** The documentation license has been upgraded to version 1.2 |
dc546b0f | 1396 | of the GNU Free Documentation License. |
75eb3bc4 | 1397 | |
d6fb461d | 1398 | ** syntax error processing |
75eb3bc4 | 1399 | |
dc546b0f PE |
1400 | - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error |
1401 | locations too. This fixes bugs in error-location computation. | |
75eb3bc4 | 1402 | |
dc546b0f PE |
1403 | - %destructor |
1404 | It is now possible to reclaim the memory associated to symbols | |
1405 | discarded during error recovery. This feature is still experimental. | |
20daca06 | 1406 | |
dc546b0f PE |
1407 | - %error-verbose |
1408 | This new directive is preferred over YYERROR_VERBOSE. | |
74724a70 | 1409 | |
dc546b0f PE |
1410 | - #defining yyerror to steal internal variables is discouraged. |
1411 | It is not guaranteed to work forever. | |
d1de5372 | 1412 | |
d6fb461d | 1413 | ** POSIX conformance |
d1de5372 | 1414 | |
dc546b0f PE |
1415 | - Semicolons are once again optional at the end of grammar rules. |
1416 | This reverts to the behavior of Bison 1.33 and earlier, and improves | |
1417 | compatibility with Yacc. | |
74724a70 | 1418 | |
e4ab1254 AD |
1419 | - "parse error" -> "syntax error" |
1420 | Bison now uniformly uses the term "syntax error"; formerly, the code | |
1421 | and manual sometimes used the term "parse error" instead. POSIX | |
1422 | requires "syntax error" in diagnostics, and it was thought better to | |
dc546b0f | 1423 | be consistent. |
74724a70 | 1424 | |
dc546b0f PE |
1425 | - The documentation now emphasizes that yylex and yyerror must be |
1426 | declared before use. C99 requires this. | |
d1de5372 | 1427 | |
dc546b0f PE |
1428 | - Bison now parses C99 lexical constructs like UCNs and |
1429 | backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires. | |
d1de5372 | 1430 | |
dc546b0f PE |
1431 | - File names are properly escaped in C output. E.g., foo\bar.y is |
1432 | output as "foo\\bar.y". | |
6780ca7a | 1433 | |
dc546b0f | 1434 | - Yacc command and library now available |
e4ab1254 | 1435 | The Bison distribution now installs a "yacc" command, as POSIX requires. |
dc546b0f PE |
1436 | Also, Bison now installs a small library liby.a containing |
1437 | implementations of Yacc-compatible yyerror and main functions. | |
1438 | This library is normally not useful, but POSIX requires it. | |
6e649e65 | 1439 | |
dc546b0f | 1440 | - Type clashes now generate warnings, not errors. |
6e649e65 | 1441 | |
dc546b0f PE |
1442 | - If the user does not define YYSTYPE as a macro, Bison now declares it |
1443 | using typedef instead of defining it as a macro. | |
1444 | For consistency, YYLTYPE is also declared instead of defined. | |
9501dc6e | 1445 | |
d6fb461d | 1446 | ** Other compatibility issues |
886a425c | 1447 | |
e4ab1254 AD |
1448 | - %union directives can now have a tag before the "{", e.g., the |
1449 | directive "%union foo {...}" now generates the C code | |
1450 | "typedef union foo { ... } YYSTYPE;"; this is for Yacc compatibility. | |
1451 | The default union tag is "YYSTYPE", for compatibility with Solaris 9 Yacc. | |
1452 | For consistency, YYLTYPE's struct tag is now "YYLTYPE" not "yyltype". | |
dc546b0f | 1453 | This is for compatibility with both Yacc and Bison 1.35. |
72f889cc | 1454 | |
e4ab1254 | 1455 | - ";" is output before the terminating "}" of an action, for |
dc546b0f | 1456 | compatibility with Bison 1.35. |
886a425c | 1457 | |
dc546b0f | 1458 | - Bison now uses a Yacc-style format for conflict reports, e.g., |
e4ab1254 | 1459 | "conflicts: 2 shift/reduce, 1 reduce/reduce". |
437c2d80 | 1460 | |
e4ab1254 | 1461 | - "yystype" and "yyltype" are now obsolescent macros instead of being |
dc546b0f PE |
1462 | typedefs or tags; they are no longer documented and are planned to be |
1463 | withdrawn in a future release. | |
2a8d363a | 1464 | |
d6fb461d | 1465 | ** GLR parser notes |
2a8d363a | 1466 | |
dc546b0f PE |
1467 | - GLR and inline |
1468 | Users of Bison have to decide how they handle the portability of the | |
e4ab1254 | 1469 | C keyword "inline". |
959e5f51 | 1470 | |
e4ab1254 AD |
1471 | - "parsing stack overflow..." -> "parser stack overflow" |
1472 | GLR parsers now report "parser stack overflow" as per the Bison manual. | |
900c5db5 | 1473 | |
18ad57b3 AD |
1474 | ** %parse-param and %lex-param |
1475 | The macros YYPARSE_PARAM and YYLEX_PARAM provide a means to pass | |
1476 | additional context to yyparse and yylex. They suffer from several | |
1477 | shortcomings: | |
1478 | ||
1479 | - a single argument only can be added, | |
1480 | - their types are weak (void *), | |
242cc08e | 1481 | - this context is not passed to ancillary functions such as yyerror, |
18ad57b3 AD |
1482 | - only yacc.c parsers support them. |
1483 | ||
1484 | The new %parse-param/%lex-param directives provide a more precise control. | |
1485 | For instance: | |
1486 | ||
1487 | %parse-param {int *nastiness} | |
1488 | %lex-param {int *nastiness} | |
1489 | %parse-param {int *randomness} | |
1490 | ||
1491 | results in the following signatures: | |
1492 | ||
1493 | int yylex (int *nastiness); | |
1494 | int yyparse (int *nastiness, int *randomness); | |
1495 | ||
1496 | or, if both %pure-parser and %locations are used: | |
1497 | ||
1498 | int yylex (YYSTYPE *lvalp, YYLTYPE *llocp, int *nastiness); | |
1499 | int yyparse (int *nastiness, int *randomness); | |
1500 | ||
d6fb461d | 1501 | ** Bison now warns if it detects conflicting outputs to the same file, |
e4ab1254 | 1502 | e.g., it generates a warning for "bison -d -o foo.h foo.y" since |
dc546b0f | 1503 | that command outputs both code and header to foo.h. |
6e40b4eb | 1504 | |
d6fb461d | 1505 | ** #line in output files |
dc546b0f | 1506 | - --no-line works properly. |
6e40b4eb | 1507 | |
d6fb461d | 1508 | ** Bison can no longer be built by a K&R C compiler; it requires C89 or |
6e40b4eb AD |
1509 | later to be built. This change originally took place a few versions |
1510 | ago, but nobody noticed until we recently asked someone to try | |
1511 | building Bison with a K&R C compiler. | |
d600ee67 | 1512 | \f |
d6fb461d | 1513 | * Changes in version 1.75, 2002-10-14: |
7933f2b5 | 1514 | |
d6fb461d | 1515 | ** Bison should now work on 64-bit hosts. |
7933f2b5 | 1516 | |
d6fb461d | 1517 | ** Indonesian translation thanks to Tedi Heriyanto. |
7933f2b5 | 1518 | |
d6fb461d | 1519 | ** GLR parsers |
f50adbbd AD |
1520 | Fix spurious parse errors. |
1521 | ||
d6fb461d | 1522 | ** Pure parsers |
f50adbbd AD |
1523 | Some people redefine yyerror to steal yyparse' private variables. |
1524 | Reenable this trick until an official feature replaces it. | |
1525 | ||
d6fb461d | 1526 | ** Type Clashes |
d90c934c AD |
1527 | In agreement with POSIX and with other Yaccs, leaving a default |
1528 | action is valid when $$ is untyped, and $1 typed: | |
1529 | ||
e29f0771 | 1530 | untyped: ... typed; |
d90c934c AD |
1531 | |
1532 | but the converse remains an error: | |
1533 | ||
e29f0771 | 1534 | typed: ... untyped; |
d90c934c | 1535 | |
d6fb461d | 1536 | ** Values of mid-rule actions |
d90c934c AD |
1537 | The following code: |
1538 | ||
e29f0771 | 1539 | foo: { ... } { $$ = $1; } ... |
d90c934c AD |
1540 | |
1541 | was incorrectly rejected: $1 is defined in the second mid-rule | |
1542 | action, and is equal to the $$ of the first mid-rule action. | |
d600ee67 | 1543 | \f |
d6fb461d | 1544 | * Changes in version 1.50, 2002-10-04: |
adc8c848 | 1545 | |
d6fb461d | 1546 | ** GLR parsing |
676385e2 PH |
1547 | The declaration |
1548 | %glr-parser | |
1549 | causes Bison to produce a Generalized LR (GLR) parser, capable of handling | |
1550 | almost any context-free grammar, ambiguous or not. The new declarations | |
e8832397 | 1551 | %dprec and %merge on grammar rules allow parse-time resolution of |
676385e2 PH |
1552 | ambiguities. Contributed by Paul Hilfinger. |
1553 | ||
7933f2b5 | 1554 | Unfortunately Bison 1.50 does not work properly on 64-bit hosts |
420f93c8 PE |
1555 | like the Alpha, so please stick to 32-bit hosts for now. |
1556 | ||
d6fb461d | 1557 | ** Output Directory |
8c165d89 | 1558 | When not in Yacc compatibility mode, when the output file was not |
e4ab1254 AD |
1559 | specified, running "bison foo/bar.y" created "foo/bar.c". It |
1560 | now creates "bar.c". | |
8c165d89 | 1561 | |
d6fb461d | 1562 | ** Undefined token |
007a50a4 | 1563 | The undefined token was systematically mapped to 2 which prevented |
e88dbdbf | 1564 | the use of 2 by the user. This is no longer the case. |
007a50a4 | 1565 | |
d6fb461d | 1566 | ** Unknown token numbers |
e88dbdbf | 1567 | If yylex returned an out of range value, yyparse could die. This is |
007a50a4 AD |
1568 | no longer the case. |
1569 | ||
d6fb461d | 1570 | ** Error token |
e88dbdbf | 1571 | According to POSIX, the error token must be 256. |
23c5a174 AD |
1572 | Bison extends this requirement by making it a preference: *if* the |
1573 | user specified that one of her tokens is numbered 256, then error | |
1574 | will be mapped onto another number. | |
1575 | ||
d6fb461d | 1576 | ** Verbose error messages |
e4ab1254 | 1577 | They no longer report "..., expecting error or..." for states where |
217598da AD |
1578 | error recovery is possible. |
1579 | ||
d6fb461d | 1580 | ** End token |
e4ab1254 | 1581 | Defaults to "$end" instead of "$". |
217598da | 1582 | |
d6fb461d | 1583 | ** Error recovery now conforms to documentation and to POSIX |
68cd8af3 PE |
1584 | When a Bison-generated parser encounters a syntax error, it now pops |
1585 | the stack until it finds a state that allows shifting the error | |
1586 | token. Formerly, it popped the stack until it found a state that | |
1587 | allowed some non-error action other than a default reduction on the | |
1588 | error token. The new behavior has long been the documented behavior, | |
1589 | and has long been required by POSIX. For more details, please see | |
337116ba PE |
1590 | Paul Eggert, "Reductions during Bison error handling" (2002-05-20) |
1591 | <http://lists.gnu.org/archive/html/bug-bison/2002-05/msg00038.html>. | |
68cd8af3 | 1592 | |
d6fb461d | 1593 | ** Traces |
5504898e AD |
1594 | Popped tokens and nonterminals are now reported. |
1595 | ||
d6fb461d | 1596 | ** Larger grammars |
a861a339 PE |
1597 | Larger grammars are now supported (larger token numbers, larger grammar |
1598 | size (= sum of the LHS and RHS lengths), larger LALR tables). | |
1599 | Formerly, many of these numbers ran afoul of 16-bit limits; | |
1600 | now these limits are 32 bits on most hosts. | |
355e7c1c | 1601 | |
d6fb461d | 1602 | ** Explicit initial rule |
643a5994 AD |
1603 | Bison used to play hacks with the initial rule, which the user does |
1604 | not write. It is now explicit, and visible in the reports and | |
1605 | graphs as rule 0. | |
23c5a174 | 1606 | |
d6fb461d | 1607 | ** Useless rules |
643a5994 | 1608 | Before, Bison reported the useless rules, but, although not used, |
77714df2 | 1609 | included them in the parsers. They are now actually removed. |
23c5a174 | 1610 | |
d6fb461d | 1611 | ** Useless rules, useless nonterminals |
6b98e4b5 AD |
1612 | They are now reported, as a warning, with their locations. |
1613 | ||
d6fb461d | 1614 | ** Rules never reduced |
e8832397 AD |
1615 | Rules that can never be reduced because of conflicts are now |
1616 | reported. | |
1617 | ||
e4ab1254 | 1618 | ** Incorrect "Token not used" |
11652ab3 AD |
1619 | On a grammar such as |
1620 | ||
e29f0771 AD |
1621 | %token useless useful |
1622 | %% | |
1623 | exp: '0' %prec useful; | |
11652ab3 AD |
1624 | |
1625 | where a token was used to set the precedence of the last rule, | |
e4ab1254 | 1626 | bison reported both "useful" and "useless" as useless tokens. |
11652ab3 | 1627 | |
d6fb461d | 1628 | ** Revert the C++ namespace changes introduced in 1.31 |
77714df2 | 1629 | as they caused too many portability hassles. |
0179dd65 | 1630 | |
d6fb461d | 1631 | ** Default locations |
b2d52318 AD |
1632 | By an accident of design, the default computation of @$ was |
1633 | performed after another default computation was performed: @$ = @1. | |
1634 | The latter is now removed: YYLLOC_DEFAULT is fully responsible of | |
1635 | the computation of @$. | |
adc8c848 | 1636 | |
d6fb461d | 1637 | ** Token end-of-file |
b7c49edf AD |
1638 | The token end of file may be specified by the user, in which case, |
1639 | the user symbol is used in the reports, the graphs, and the verbose | |
e4ab1254 | 1640 | error messages instead of "$end", which remains being the default. |
b7c49edf | 1641 | For instance |
e29f0771 | 1642 | %token MYEOF 0 |
b7c49edf | 1643 | or |
e29f0771 | 1644 | %token MYEOF 0 "end of file" |
fdbcd8e2 | 1645 | |
d6fb461d | 1646 | ** Semantic parser |
fdbcd8e2 AD |
1647 | This old option, which has been broken for ages, is removed. |
1648 | ||
d6fb461d | 1649 | ** New translations |
a861a339 | 1650 | Brazilian Portuguese, thanks to Alexandre Folle de Menezes. |
84614e13 AD |
1651 | Croatian, thanks to Denis Lackovic. |
1652 | ||
d6fb461d | 1653 | ** Incorrect token definitions |
e4ab1254 AD |
1654 | When given |
1655 | %token 'a' "A" | |
1656 | bison used to output | |
1657 | #define 'a' 65 | |
b87f8b21 | 1658 | |
d6fb461d | 1659 | ** Token definitions as enums |
77714df2 AD |
1660 | Tokens are output both as the traditional #define's, and, provided |
1661 | the compiler supports ANSI C or is a C++ compiler, as enums. | |
e88dbdbf | 1662 | This lets debuggers display names instead of integers. |
77714df2 | 1663 | |
d6fb461d | 1664 | ** Reports |
ec3bc396 AD |
1665 | In addition to --verbose, bison supports --report=THINGS, which |
1666 | produces additional information: | |
b408954b AD |
1667 | - itemset |
1668 | complete the core item sets with their closure | |
e4ab1254 | 1669 | - lookahead [changed to "look-ahead" in 1.875e through 2.3, but changed back] |
9e6e7ed2 | 1670 | explicitly associate lookahead tokens to items |
b408954b AD |
1671 | - solved |
1672 | describe shift/reduce conflicts solving. | |
1673 | Bison used to systematically output this information on top of | |
1674 | the report. Solved conflicts are now attached to their states. | |
ec3bc396 | 1675 | |
d6fb461d | 1676 | ** Type clashes |
9af3fbce AD |
1677 | Previous versions don't complain when there is a type clash on |
1678 | the default action if the rule has a mid-rule action, such as in: | |
1679 | ||
e29f0771 AD |
1680 | %type <foo> bar |
1681 | %% | |
1682 | bar: '0' {} '0'; | |
9af3fbce AD |
1683 | |
1684 | This is fixed. | |
a861a339 | 1685 | |
d6fb461d | 1686 | ** GNU M4 is now required when using Bison. |
f987e9d2 | 1687 | \f |
d6fb461d | 1688 | * Changes in version 1.35, 2002-03-25: |
76551463 | 1689 | |
d6fb461d | 1690 | ** C Skeleton |
76551463 AD |
1691 | Some projects use Bison's C parser with C++ compilers, and define |
1692 | YYSTYPE as a class. The recent adjustment of C parsers for data | |
1693 | alignment and 64 bit architectures made this impossible. | |
1694 | ||
1695 | Because for the time being no real solution for C++ parser | |
1696 | generation exists, kludges were implemented in the parser to | |
1697 | maintain this use. In the future, when Bison has C++ parsers, this | |
1698 | kludge will be disabled. | |
1699 | ||
1700 | This kludge also addresses some C++ problems when the stack was | |
1701 | extended. | |
76551463 | 1702 | \f |
d6fb461d | 1703 | * Changes in version 1.34, 2002-03-12: |
76551463 | 1704 | |
d6fb461d | 1705 | ** File name clashes are detected |
76551463 | 1706 | $ bison foo.y -d -o foo.x |
e4ab1254 | 1707 | fatal error: header and parser would both be named "foo.x" |
76551463 | 1708 | |
e4ab1254 | 1709 | ** A missing ";" at the end of a rule triggers a warning |
76551463 AD |
1710 | In accordance with POSIX, and in agreement with other |
1711 | Yacc implementations, Bison will mandate this semicolon in the near | |
1712 | future. This eases the implementation of a Bison parser of Bison | |
1713 | grammars by making this grammar LALR(1) instead of LR(2). To | |
1714 | facilitate the transition, this release introduces a warning. | |
1715 | ||
d6fb461d | 1716 | ** Revert the C++ namespace changes introduced in 1.31, as they caused too |
76551463 AD |
1717 | many portability hassles. |
1718 | ||
d6fb461d | 1719 | ** DJGPP support added. |
76551463 | 1720 | |
d6fb461d | 1721 | ** Fix test suite portability problems. |
76551463 | 1722 | \f |
d6fb461d | 1723 | * Changes in version 1.33, 2002-02-07: |
76551463 | 1724 | |
d6fb461d | 1725 | ** Fix C++ issues |
76551463 AD |
1726 | Groff could not be compiled for the definition of size_t was lacking |
1727 | under some conditions. | |
1728 | ||
d6fb461d | 1729 | ** Catch invalid @n |
76551463 AD |
1730 | As is done with $n. |
1731 | \f | |
d6fb461d | 1732 | * Changes in version 1.32, 2002-01-23: |
76551463 | 1733 | |
d6fb461d | 1734 | ** Fix Yacc output file names |
76551463 | 1735 | |
d6fb461d | 1736 | ** Portability fixes |
76551463 | 1737 | |
d6fb461d | 1738 | ** Italian, Dutch translations |
76551463 | 1739 | \f |
d6fb461d | 1740 | * Changes in version 1.31, 2002-01-14: |
52d1aeee | 1741 | |
d6fb461d | 1742 | ** Many Bug Fixes |
52d1aeee | 1743 | |
d6fb461d | 1744 | ** GNU Gettext and %expect |
52d1aeee MA |
1745 | GNU Gettext asserts 10 s/r conflicts, but there are 7. Now that |
1746 | Bison dies on incorrect %expectations, we fear there will be | |
1747 | too many bug reports for Gettext, so _for the time being_, %expect | |
e4ab1254 | 1748 | does not trigger an error when the input file is named "plural.y". |
52d1aeee | 1749 | |
d6fb461d | 1750 | ** Use of alloca in parsers |
52d1aeee MA |
1751 | If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use |
1752 | malloc exclusively. Since 1.29, but was not NEWS'ed. | |
1753 | ||
1754 | alloca is used only when compiled with GCC, to avoid portability | |
1755 | problems as on AIX. | |
1756 | ||
d6fb461d | 1757 | ** yyparse now returns 2 if memory is exhausted; formerly it dumped core. |
b47dbebe | 1758 | |
d6fb461d | 1759 | ** When the generated parser lacks debugging code, YYDEBUG is now 0 |
52d1aeee MA |
1760 | (as POSIX requires) instead of being undefined. |
1761 | ||
d6fb461d | 1762 | ** User Actions |
52d1aeee MA |
1763 | Bison has always permitted actions such as { $$ = $1 }: it adds the |
1764 | ending semicolon. Now if in Yacc compatibility mode, the semicolon | |
1765 | is no longer output: one has to write { $$ = $1; }. | |
1766 | ||
d6fb461d | 1767 | ** Better C++ compliance |
52d1aeee | 1768 | The output parsers try to respect C++ namespaces. |
76551463 | 1769 | [This turned out to be a failed experiment, and it was reverted later.] |
52d1aeee | 1770 | |
d6fb461d | 1771 | ** Reduced Grammars |
52d1aeee MA |
1772 | Fixed bugs when reporting useless nonterminals. |
1773 | ||
d6fb461d | 1774 | ** 64 bit hosts |
52d1aeee MA |
1775 | The parsers work properly on 64 bit hosts. |
1776 | ||
d6fb461d | 1777 | ** Error messages |
52d1aeee MA |
1778 | Some calls to strerror resulted in scrambled or missing error messages. |
1779 | ||
d6fb461d | 1780 | ** %expect |
52d1aeee MA |
1781 | When the number of shift/reduce conflicts is correct, don't issue |
1782 | any warning. | |
1783 | ||
d6fb461d | 1784 | ** The verbose report includes the rule line numbers. |
52d1aeee | 1785 | |
d6fb461d | 1786 | ** Rule line numbers are fixed in traces. |
52d1aeee | 1787 | |
d6fb461d | 1788 | ** Swedish translation |
52d1aeee | 1789 | |
d6fb461d | 1790 | ** Parse errors |
52d1aeee MA |
1791 | Verbose parse error messages from the parsers are better looking. |
1792 | Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'('' | |
1793 | Now: parse error: unexpected '/', expecting "number" or '-' or '(' | |
1794 | ||
d6fb461d | 1795 | ** Fixed parser memory leaks. |
52d1aeee MA |
1796 | When the generated parser was using malloc to extend its stacks, the |
1797 | previous allocations were not freed. | |
1798 | ||
d6fb461d | 1799 | ** Fixed verbose output file. |
52d1aeee MA |
1800 | Some newlines were missing. |
1801 | Some conflicts in state descriptions were missing. | |
1802 | ||
d6fb461d | 1803 | ** Fixed conflict report. |
52d1aeee MA |
1804 | Option -v was needed to get the result. |
1805 | ||
d6fb461d | 1806 | ** %expect |
52d1aeee MA |
1807 | Was not used. |
1808 | Mismatches are errors, not warnings. | |
1809 | ||
d6fb461d | 1810 | ** Fixed incorrect processing of some invalid input. |
52d1aeee | 1811 | |
d6fb461d | 1812 | ** Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H. |
52d1aeee | 1813 | |
d6fb461d | 1814 | ** Fixed some typos in the documentation. |
52d1aeee | 1815 | |
d6fb461d | 1816 | ** %token MY_EOF 0 is supported. |
52d1aeee MA |
1817 | Before, MY_EOF was silently renumbered as 257. |
1818 | ||
d6fb461d | 1819 | ** doc/refcard.tex is updated. |
52d1aeee | 1820 | |
d6fb461d | 1821 | ** %output, %file-prefix, %name-prefix. |
52d1aeee MA |
1822 | New. |
1823 | ||
d6fb461d | 1824 | ** --output |
e4ab1254 | 1825 | New, aliasing "--output-file". |
52d1aeee | 1826 | \f |
d6fb461d | 1827 | * Changes in version 1.30, 2001-10-26: |
342b8b6e | 1828 | |
e4ab1254 AD |
1829 | ** "--defines" and "--graph" have now an optional argument which is the |
1830 | output file name. "-d" and "-g" do not change; they do not take any | |
342b8b6e AD |
1831 | argument. |
1832 | ||
e4ab1254 | 1833 | ** "%source_extension" and "%header_extension" are removed, failed |
342b8b6e AD |
1834 | experiment. |
1835 | ||
d6fb461d | 1836 | ** Portability fixes. |
f987e9d2 | 1837 | \f |
d6fb461d | 1838 | * Changes in version 1.29, 2001-09-07: |
342b8b6e | 1839 | |
d6fb461d | 1840 | ** The output file does not define const, as this caused problems when used |
342b8b6e AD |
1841 | with common autoconfiguration schemes. If you still use ancient compilers |
1842 | that lack const, compile with the equivalent of the C compiler option | |
e4ab1254 | 1843 | "-Dconst=". Autoconf's AC_C_CONST macro provides one way to do this. |
342b8b6e | 1844 | |
e4ab1254 | 1845 | ** Added "-g" and "--graph". |
f87a2205 | 1846 | |
d6fb461d | 1847 | ** The Bison manual is now distributed under the terms of the GNU FDL. |
f2b5126e | 1848 | |
d6fb461d | 1849 | ** The input and the output files has automatically a similar extension. |
234a3be3 | 1850 | |
d6fb461d | 1851 | ** Russian translation added. |
f87a2205 | 1852 | |
d6fb461d | 1853 | ** NLS support updated; should hopefully be less troublesome. |
f87a2205 | 1854 | |
d6fb461d | 1855 | ** Added the old Bison reference card. |
c33638bb | 1856 | |
e4ab1254 | 1857 | ** Added "--locations" and "%locations". |
6deb4447 | 1858 | |
e4ab1254 | 1859 | ** Added "-S" and "--skeleton". |
cd5bd6ac | 1860 | |
e4ab1254 | 1861 | ** "%raw", "-r", "--raw" is disabled. |
62ab6972 | 1862 | |
d6fb461d | 1863 | ** Special characters are escaped when output. This solves the problems |
cd5bd6ac AD |
1864 | of the #line lines with path names including backslashes. |
1865 | ||
d6fb461d | 1866 | ** New directives. |
e4ab1254 AD |
1867 | "%yacc", "%fixed_output_files", "%defines", "%no_parser", "%verbose", |
1868 | "%debug", "%source_extension" and "%header_extension". | |
f987e9d2 | 1869 | |
d6fb461d | 1870 | ** @$ |
f987e9d2 | 1871 | Automatic location tracking. |
f87a2205 | 1872 | \f |
d6fb461d | 1873 | * Changes in version 1.28, 1999-07-06: |
d2e00347 | 1874 | |
d6fb461d | 1875 | ** Should compile better now with K&R compilers. |
d2e00347 | 1876 | |
d6fb461d | 1877 | ** Added NLS. |
d2e00347 | 1878 | |
d6fb461d | 1879 | ** Fixed a problem with escaping the double quote character. |
d2e00347 | 1880 | |
d6fb461d | 1881 | ** There is now a FAQ. |
d2e00347 | 1882 | \f |
d6fb461d | 1883 | * Changes in version 1.27: |
5c31c3c2 | 1884 | |
d6fb461d | 1885 | ** The make rule which prevented bison.simple from being created on |
5c31c3c2 JT |
1886 | some systems has been fixed. |
1887 | \f | |
d6fb461d | 1888 | * Changes in version 1.26: |
4be07551 | 1889 | |
7e508a2b | 1890 | ** Bison now uses Automake. |
4be07551 | 1891 | |
d6fb461d | 1892 | ** New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>. |
4be07551 | 1893 | |
d6fb461d | 1894 | ** Token numbers now start at 257 as previously documented, not 258. |
4be07551 | 1895 | |
d6fb461d | 1896 | ** Bison honors the TMPDIR environment variable. |
4be07551 | 1897 | |
d6fb461d | 1898 | ** A couple of buffer overruns have been fixed. |
f51dbca1 | 1899 | |
d6fb461d | 1900 | ** Problems when closing files should now be reported. |
f51dbca1 | 1901 | |
d6fb461d | 1902 | ** Generated parsers should now work even on operating systems which do |
f51dbca1 | 1903 | not provide alloca(). |
4be07551 | 1904 | \f |
d6fb461d | 1905 | * Changes in version 1.25, 1995-10-16: |
df8878c5 | 1906 | |
d6fb461d | 1907 | ** Errors in the input grammar are not fatal; Bison keeps reading |
df8878c5 | 1908 | the grammar file, and reports all the errors found in it. |
8c44d3ec | 1909 | |
d6fb461d | 1910 | ** Tokens can now be specified as multiple-character strings: for |
df8878c5 | 1911 | example, you could use "<=" for a token which looks like <=, instead |
7e508a2b | 1912 | of choosing a name like LESSEQ. |
df8878c5 | 1913 | |
d6fb461d | 1914 | ** The %token_table declaration says to write a table of tokens (names |
df8878c5 RS |
1915 | and numbers) into the parser file. The yylex function can use this |
1916 | table to recognize multiple-character string tokens, or for other | |
1917 | purposes. | |
1918 | ||
d6fb461d | 1919 | ** The %no_lines declaration says not to generate any #line preprocessor |
df8878c5 RS |
1920 | directives in the parser file. |
1921 | ||
d6fb461d | 1922 | ** The %raw declaration says to use internal Bison token numbers, not |
df8878c5 RS |
1923 | Yacc-compatible token numbers, when token names are defined as macros. |
1924 | ||
d6fb461d | 1925 | ** The --no-parser option produces the parser tables without including |
df8878c5 RS |
1926 | the parser engine; a project can now use its own parser engine. |
1927 | The actions go into a separate file called NAME.act, in the form of | |
1928 | a switch statement body. | |
1929 | \f | |
d6fb461d | 1930 | * Changes in version 1.23: |
6780ca7a | 1931 | |
4d019228 DM |
1932 | The user can define YYPARSE_PARAM as the name of an argument to be |
1933 | passed into yyparse. The argument should have type void *. It should | |
1934 | actually point to an object. Grammar actions can access the variable | |
1935 | by casting it to the proper pointer type. | |
6780ca7a | 1936 | |
6780ca7a | 1937 | Line numbers in output file corrected. |
6780ca7a | 1938 | \f |
d6fb461d | 1939 | * Changes in version 1.22: |
6780ca7a DM |
1940 | |
1941 | --help option added. | |
6780ca7a | 1942 | \f |
d6fb461d | 1943 | * Changes in version 1.20: |
6780ca7a DM |
1944 | |
1945 | Output file does not redefine const for C++. | |
9f4503d6 | 1946 | |
76551463 AD |
1947 | ----- |
1948 | ||
c932d613 | 1949 | Copyright (C) 1995-2012 Free Software Foundation, Inc. |
76551463 | 1950 | |
8defe11b | 1951 | This file is part of Bison, the GNU Parser Generator. |
76551463 | 1952 | |
f16b0819 | 1953 | This program is free software: you can redistribute it and/or modify |
76551463 | 1954 | it under the terms of the GNU General Public License as published by |
f16b0819 PE |
1955 | the Free Software Foundation, either version 3 of the License, or |
1956 | (at your option) any later version. | |
76551463 | 1957 | |
f16b0819 | 1958 | This program is distributed in the hope that it will be useful, |
76551463 AD |
1959 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
1960 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
1961 | GNU General Public License for more details. | |
1962 | ||
1963 | You should have received a copy of the GNU General Public License | |
f16b0819 | 1964 | along with this program. If not, see <http://www.gnu.org/licenses/>. |
7e508a2b AD |
1965 | |
1966 | LocalWords: yacc YYBACKUP glr GCC lalr ArrayIndexOutOfBoundsException nullptr | |
1967 | LocalWords: cplusplus liby rpl fprintf mfcalc Wyacc stmt cond expr mk sym lr | |
1968 | LocalWords: IELR ielr Lookahead YYERROR nonassoc LALR's api lookaheads yychar | |
1969 | LocalWords: destructor lookahead YYRHSLOC YYLLOC Rhs ifndef YYFAIL cpp sr rr | |
1970 | LocalWords: preprocessor initializer Wno Wnone Werror FreeBSD prec livelocks | |
1971 | LocalWords: Solaris AIX UX RHEL Tru LHS gcc's Wundef YYENABLE NLS YYLTYPE VCG | |
1972 | LocalWords: yyerror cpp's Wunused yylval yylloc prepend yyparse yylex yypush | |
1973 | LocalWords: Graphviz xml nonterminals midrule destructor's YYSTYPE typedef ly | |
1974 | LocalWords: CHR chr printf stdout namespace preprocessing enum pre include's | |
1975 | LocalWords: YYRECOVERING nonfree destructors YYABORT YYACCEPT params enums de | |
1976 | LocalWords: struct yystype DJGPP lex param Haible NUM alloca YYSTACK NUL goto | |
1977 | LocalWords: YYMAXDEPTH Unescaped UCNs YYLTYPE's yyltype typedefs inline Yaccs | |
1978 | LocalWords: Heriyanto Reenable dprec Hilfinger Eggert MYEOF Folle Menezes EOF | |
242cc08e | 1979 | LocalWords: Lackovic define's itemset Groff Gettext malloc NEWS'ed YYDEBUG YY |
7e508a2b | 1980 | LocalWords: namespaces strerror const autoconfiguration Dconst Autoconf's FDL |
242cc08e AD |
1981 | LocalWords: Automake TMPDIR LESSEQ ylwrap endif yydebug YYTOKEN YYLSP ival hh |
1982 | LocalWords: extern YYTOKENTYPE TOKENTYPE yytokentype tokentype STYPE lval pdf | |
7287be84 AD |
1983 | LocalWords: lang yyoutput dvi html ps POSIX lvalp llocp calc yyo fval Wmaybe |
1984 | LocalWords: yyvsp pragmas noreturn java's | |
7e508a2b AD |
1985 | |
1986 | Local Variables: | |
1987 | mode: outline | |
e4ab1254 | 1988 | fill-column: 76 |
7e508a2b | 1989 | End: |