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