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ed7658fe 1GNU Bison NEWS
3af4feb2 2
52718713 3* Noteworthy changes in release ?.? (????-??-??) [?]
74553c98 4
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5** Incompatible changes
6
7*** Obsolete features
8
9 Support for YYFAIL is removed, as announced since Bison 2.4.2.
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10 Support for yystype and yyltype (instead of YYSTYPE and YYLTYPE)
11 is removed, as announced in Bison 1.875.
47db7ed1 12
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13** Warnings
14
34904c57 15*** Warning categories are now displayed
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16
17 For instance:
18
19 foo.y:4.6: warning: type clash on default action: <foo> != <bar> [-Wother]
20
21*** Useless semantic types
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22
23 Bison now warns about useless (uninhabited) semantic types. Since
24 semantic types are not declared to Bison (they are defined in the opaque
25 %union structure), it is %printer/%destructor directives about useless
26 types that trigger the warning:
27
28 %token <type1> term
29 %type <type2> nterm
30 %printer {} <type1> <type3>
31 %destructor {} <type2> <type4>
32 %%
33 nterm: term { $$ = $1; };
34
35 3.28-34: warning: type <type3> is used, but is not associated to any symbol
36 4.28-34: warning: type <type4> is used, but is not associated to any symbol
37
73370a9d 38*** Undeclared symbols
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39
40 Bison used to raise an error for %printer and %destructor directives for
41 undefined symbols.
42
43 %printer {} symbol1
44 %destructor {} symbol2
45 %%
46 exp: "a";
47
48 This is now only a warning.
49
73370a9d 50*** Useless destructors or printers
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51
52 Bison now warns about useless destructors or printers. In the following
53 example, the printer for <type1>, and the destructor for <type2> are
54 useless: all symbols of <type1> (token1) already have a printer, and all
55 symbols of type <type2> (token2) already have a destructor.
56
57 %token <type1> token1
58 <type2> token2
59 <type3> token3
60 <type4> token4
61 %printer {} token1 <type1> <type3>
62 %destructor {} token2 <type2> <type4>
63
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64** Additional yylex/yyparse arguments
65
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66 The new directive %param declares additional arguments to both yylex and
67 yyparse. The %lex-param, %parse-param, and %param directives support one
68 or more arguments. Instead of
2055a44e 69
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70 %lex-param {arg1_type *arg1}
71 %lex-param {arg2_type *arg2}
72 %parse-param {arg1_type *arg1}
73 %parse-param {arg2_type *arg2}
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74
75 one may now declare
76
e436fa67 77 %param {arg1_type *arg1} {arg2_type *arg2}
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78
79** Java skeleton improvements
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80
81 The constants for token names were moved to the Lexer interface.
82 Also, it is possible to add code to the parser's constructors using
83 "%code init" and "%define init_throws".
84
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85** C++ skeletons improvements
86
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87*** parser header (%defines) is no longer mandatory (lalr1.cc)
88
89 In which case, if needed, the support classes are defined in the generated
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90 parser, instead of additional files (location.hh, position.hh and
91 stack.hh).
93549bcd 92
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93*** locations are no longer mandatory (lalr1.cc, glr.cc)
94
95 Both lalr1.cc and glr.cc no longer require %location.
96
97*** syntax_error exception (lalr1.cc)
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98
99 The C++ parser features a syntax_error exception, which can be
100 thrown from the scanner or from user rules to raise syntax errors.
101 This facilitates reporting errors caught in sub-functions (e.g.,
102 rejecting too large integral literals from a conversion function
103 used by the scanner, or rejecting invalid combinations from a
104 factory invoked by the user actions).
105
4c6622c2 106** Variable api.tokens.prefix
99c08fb6 107
4c6622c2 108 The variable api.tokens.prefix changes the way tokens are identified in
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109 the generated files. This is especially useful to avoid collisions
110 with identifiers in the target language. For instance
111
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112 %token FILE for ERROR
113 %define api.tokens.prefix "TOK_"
114 %%
115 start: FILE for ERROR;
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116
117 will generate the definition of the symbols TOK_FILE, TOK_for, and
118 TOK_ERROR in the generated sources. In particular, the scanner must
119 use these prefixed token names, although the grammar itself still
120 uses the short names (as in the sample rule given above).
121
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122** Variable api.namespace
123
124 The "namespace" variable is renamed "api.namespace". Backward
125 compatibility is ensured, but upgrading is recommended.
126
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127** Variable parse.error
128
129 The variable error controls the verbosity of error messages. The
130 use of the %error-verbose directive is deprecated in favor of
131 %define parse.error "verbose".
132
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133** Semantic predicates
134
135 The new, experimental, semantic-predicate feature allows actions of
136 the form %?{ BOOLEAN-EXPRESSION }, which cause syntax errors (as for
137 YYERROR) if the expression evaluates to 0, and are evaluated immediately
138 in GLR parsers, rather than being deferred. The result is that they
139 allow the programmer to prune possible parses based on the values of
dcb366b1 140 run-time expressions.
ca2a6d15 141
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142* Noteworthy changes in release ?.? (????-??-??) [?]
143
9c26b8fc 144
77b214ef 145* Noteworthy changes in release 2.6.1 (2012-07-30) [stable]
a4107f24 146
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147 Bison no longer executes user-specified M4 code when processing a grammar.
148
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149** Future Changes
150
151 In addition to the removal of the features announced in Bison 2.6, the
152 next major release will remove the "Temporary hack for adding a semicolon
153 to the user action", as announced in the release 2.5. Instead of:
154
155 exp: exp "+" exp { $$ = $1 + $3 };
156
157 write:
158
159 exp: exp "+" exp { $$ = $1 + $3; };
160
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161** Bug fixes
162
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163*** Type names are now properly escaped.
164
165*** glr.cc: set_debug_level and debug_level work as expected.
a4107f24 166
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167*** Stray @ or $ in actions
168
169 While Bison used to warn about stray $ or @ in action rules, it did not
170 for other actions such as printers, destructors, or initial actions. It
171 now does.
172
cd735a8c 173** Type names in actions
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174
175 For consistency with rule actions, it is now possible to qualify $$ by a
cd735a8c 176 type-name in destructors, printers, and initial actions. For instance:
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177
178 %printer { fprintf (yyo, "(%d, %f)", $<ival>$, $<fval>$); } <*> <>;
179
180 will display two values for each typed and untyped symbol (provided
cd735a8c 181 that YYSTYPE has both "ival" and "fval" fields).
60aa04a2 182
1505e8bb 183* Noteworthy changes in release 2.6 (2012-07-19) [stable]
0f11eec2 184
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185** Future changes:
186
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187 The next major release of Bison will drop support for the following
188 deprecated features. Please report disagreements to bug-bison@gnu.org.
0f11eec2 189
aaf61036 190*** K&R C parsers
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191
192 Support for generating parsers in K&R C will be removed. Parsers
242cc08e 193 generated for C support ISO C90, and are tested with ISO C99 and ISO C11
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194 compilers.
195
258cddbc 196*** Features deprecated since Bison 1.875
0f11eec2 197
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198 The definitions of yystype and yyltype will be removed; use YYSTYPE and
199 YYLTYPE.
0f11eec2 200
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201 YYPARSE_PARAM and YYLEX_PARAM, deprecated in favor of %parse-param and
202 %lex-param, will no longer be supported.
203
204 Support for the preprocessor symbol YYERROR_VERBOSE will be removed, use
205 %error-verbose.
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206
207*** The generated header will be included (yacc.c)
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208
209 Instead of duplicating the content of the generated header (definition of
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210 YYSTYPE, yyparse declaration etc.), the generated parser will include it,
211 as is already the case for GLR or C++ parsers. This change is deferred
212 because existing versions of ylwrap (e.g., Automake 1.12.1) do not support
213 it.
0f11eec2 214
c2425191 215** Generated Parser Headers
56ca3d8f 216
258cddbc 217*** Guards (yacc.c, glr.c, glr.cc)
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218
219 The generated headers are now guarded, as is already the case for C++
242cc08e 220 parsers (lalr1.cc). For instance, with --defines=foo.h:
c3e9f08f 221
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222 #ifndef YY_FOO_H
223 # define YY_FOO_H
224 ...
225 #endif /* !YY_FOO_H */
c3e9f08f 226
258cddbc 227*** New declarations (yacc.c, glr.c)
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228
229 The generated header now declares yydebug and yyparse. Both honor
230 --name-prefix=bar_, and yield
231
e29f0771 232 int bar_parse (void);
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233
234 rather than
235
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236 #define yyparse bar_parse
237 int yyparse (void);
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238
239 in order to facilitate the inclusion of several parser headers inside a
240 single compilation unit.
c3e9f08f 241
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242*** Exported symbols in C++
243
244 The symbols YYTOKEN_TABLE and YYERROR_VERBOSE, which were defined in the
245 header, are removed, as they prevent the possibility of including several
246 generated headers from a single compilation unit.
247
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248*** YYLSP_NEEDED
249
250 For the same reasons, the undocumented and unused macro YYLSP_NEEDED is no
251 longer defined.
252
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253** New %define variable: api.prefix
254
255 Now that the generated headers are more complete and properly protected
256 against multiple inclusions, constant names, such as YYSTYPE are a
257 problem. While yyparse and others are properly renamed by %name-prefix,
258 YYSTYPE, YYDEBUG and others have never been affected by it. Because it
259 would introduce backward compatibility issues in projects not expecting
260 YYSTYPE to be renamed, instead of changing the behavior of %name-prefix,
261 it is deprecated in favor of a new %define variable: api.prefix.
262
263 The following examples compares both:
264
265 %name-prefix "bar_" | %define api.prefix "bar_"
266 %token <ival> FOO %token <ival> FOO
267 %union { int ival; } %union { int ival; }
268 %% %%
269 exp: 'a'; exp: 'a';
270
271 bison generates:
272
273 #ifndef BAR_FOO_H #ifndef BAR_FOO_H
274 # define BAR_FOO_H # define BAR_FOO_H
275
276 /* Enabling traces. */ /* Enabling traces. */
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277 # ifndef YYDEBUG | # ifndef BAR_DEBUG
278 > # if defined YYDEBUG
279 > # if YYDEBUG
280 > # define BAR_DEBUG 1
281 > # else
282 > # define BAR_DEBUG 0
283 > # endif
284 > # else
285 # define YYDEBUG 0 | # define BAR_DEBUG 0
286 > # endif
287 # endif | # endif
288
289 # if YYDEBUG | # if BAR_DEBUG
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290 extern int bar_debug; extern int bar_debug;
291 # endif # endif
292
293 /* Tokens. */ /* Tokens. */
294 # ifndef YYTOKENTYPE | # ifndef BAR_TOKENTYPE
295 # define YYTOKENTYPE | # define BAR_TOKENTYPE
296 enum yytokentype { | enum bar_tokentype {
297 FOO = 258 FOO = 258
298 }; };
299 # endif # endif
300
301 #if ! defined YYSTYPE \ | #if ! defined BAR_STYPE \
302 && ! defined YYSTYPE_IS_DECLARED | && ! defined BAR_STYPE_IS_DECLARED
303 typedef union YYSTYPE | typedef union BAR_STYPE
304 { {
305 int ival; int ival;
306 } YYSTYPE; | } BAR_STYPE;
307 # define YYSTYPE_IS_DECLARED 1 | # define BAR_STYPE_IS_DECLARED 1
308 #endif #endif
309
310 extern YYSTYPE bar_lval; | extern BAR_STYPE bar_lval;
311
312 int bar_parse (void); int bar_parse (void);
313
314 #endif /* !BAR_FOO_H */ #endif /* !BAR_FOO_H */
315
dfaac272 316* Noteworthy changes in release 2.5.1 (2012-06-05) [stable]
df6e3db0 317
debe2c03 318** Future changes:
765e1bd4 319
e4ab1254 320 The next major release will drop support for generating parsers in K&R C.
041308d0 321
466b4cf2 322** yacc.c: YYBACKUP works as expected.
ef51bfa7 323
d834eca0 324** glr.c improvements:
041308d0 325
d834eca0 326*** Location support is eliminated when not requested:
041308d0 327
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328 GLR parsers used to include location-related code even when locations were
329 not requested, and therefore not even usable.
378e917c 330
d834eca0 331*** __attribute__ is preserved:
d115aad9 332
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333 __attribute__ is no longer disabled when __STRICT_ANSI__ is defined (i.e.,
334 when -std is passed to GCC).
041308d0 335
466b4cf2 336** lalr1.java: several fixes:
041308d0 337
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338 The Java parser no longer throws ArrayIndexOutOfBoundsException if the
339 first token leads to a syntax error. Some minor clean ups.
041308d0 340
22172d47 341** Changes for C++:
ef51bfa7 342
22172d47 343*** C++11 compatibility:
ef51bfa7 344
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345 C and C++ parsers use "nullptr" instead of "0" when __cplusplus is 201103L
346 or higher.
936c88d1 347
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348*** Header guards
349
350 The header files such as "parser.hh", "location.hh", etc. used a constant
351 name for preprocessor guards, for instance:
352
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353 #ifndef BISON_LOCATION_HH
354 # define BISON_LOCATION_HH
355 ...
356 #endif // !BISON_LOCATION_HH
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357
358 The inclusion guard is now computed from "PREFIX/FILE-NAME", where lower
359 case characters are converted to upper case, and series of
360 non-alphanumerical characters are converted to an underscore.
361
362 With "bison -o lang++/parser.cc", "location.hh" would now include:
363
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364 #ifndef YY_LANG_LOCATION_HH
365 # define YY_LANG_LOCATION_HH
366 ...
367 #endif // !YY_LANG_LOCATION_HH
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368
369*** C++ locations:
936c88d1 370
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371 The position and location constructors (and their initialize methods)
372 accept new arguments for line and column. Several issues in the
373 documentation were fixed.
936c88d1 374
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375** liby is no longer asking for "rpl_fprintf" on some platforms.
376
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377** Changes in the manual:
378
379*** %printer is documented
380
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381 The "%printer" directive, supported since at least Bison 1.50, is finally
382 documented. The "mfcalc" example is extended to demonstrate it.
7e508a2b 383
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384 For consistency with the C skeletons, the C++ parsers now also support
385 "yyoutput" (as an alias to "debug_stream ()").
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386
387*** Several improvements have been made:
466b4cf2 388
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389 The layout for grammar excerpts was changed to a more compact scheme.
390 Named references are motivated. The description of the automaton
391 description file (*.output) is updated to the current format. Incorrect
392 index entries were fixed. Some other errors were fixed.
466b4cf2 393
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394** Building bison:
395
396*** Conflicting prototypes with recent/modified Flex.
466b4cf2 397
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398 Fixed build problems with the current, unreleased, version of Flex, and
399 some modified versions of 2.5.35, which have modified function prototypes.
466b4cf2 400
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401*** Warnings during the build procedure have been eliminated.
402
403*** Several portability problems in the test suite have been fixed:
466b4cf2 404
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405 This includes warnings with some compilers, unexpected behavior of tools
406 such as diff, warning messages from the test suite itself, etc.
466b4cf2 407
91aadcc7 408*** The install-pdf target works properly:
8ef26c2a 409
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410 Running "make install-pdf" (or -dvi, -html, -info, and -ps) no longer
411 halts in the middle of its course.
8ef26c2a 412
28801043 413* Changes in version 2.5 (2011-05-14):
50cca368 414
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415** Grammar symbol names can now contain non-initial dashes:
416
417 Consistently with directives (such as %error-verbose) and with
418 %define variables (e.g. push-pull), grammar symbol names may contain
419 dashes in any position except the beginning. This is a GNU
420 extension over POSIX Yacc. Thus, use of this extension is reported
421 by -Wyacc and rejected in Yacc mode (--yacc).
422
f1b238df 423** Named references:
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424
425 Historically, Yacc and Bison have supported positional references
426 ($n, $$) to allow access to symbol values from inside of semantic
427 actions code.
428
429 Starting from this version, Bison can also accept named references.
430 When no ambiguity is possible, original symbol names may be used
431 as named references:
432
4b568fc0 433 if_stmt : "if" cond_expr "then" then_stmt ';'
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434 { $if_stmt = mk_if_stmt($cond_expr, $then_stmt); }
435
436 In the more common case, explicit names may be declared:
437
4b568fc0 438 stmt[res] : "if" expr[cond] "then" stmt[then] "else" stmt[else] ';'
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439 { $res = mk_if_stmt($cond, $then, $else); }
440
5b1ff423 441 Location information is also accessible using @name syntax. When
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442 accessing symbol names containing dots or dashes, explicit bracketing
443 ($[sym.1]) must be used.
444
5b1ff423 445 These features are experimental in this version. More user feedback
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446 will help to stabilize them.
447
f1b238df 448** IELR(1) and canonical LR(1):
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449
450 IELR(1) is a minimal LR(1) parser table generation algorithm. That
451 is, given any context-free grammar, IELR(1) generates parser tables
7262f54f 452 with the full language-recognition power of canonical LR(1) but with
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453 nearly the same number of parser states as LALR(1). This reduction
454 in parser states is often an order of magnitude. More importantly,
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455 because canonical LR(1)'s extra parser states may contain duplicate
456 conflicts in the case of non-LR(1) grammars, the number of conflicts
457 for IELR(1) is often an order of magnitude less as well. This can
458 significantly reduce the complexity of developing of a grammar.
459
460 Bison can now generate IELR(1) and canonical LR(1) parser tables in
461 place of its traditional LALR(1) parser tables, which remain the
462 default. You can specify the type of parser tables in the grammar
463 file with these directives:
464
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465 %define lr.type lalr
466 %define lr.type ielr
467 %define lr.type canonical-lr
eb45ef3b 468
7fceb615 469 The default-reduction optimization in the parser tables can also be
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470 adjusted using "%define lr.default-reductions". For details on both
471 of these features, see the new section "Tuning LR" in the Bison
7fceb615 472 manual.
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473
474 These features are experimental. More user feedback will help to
475 stabilize them.
476
7fceb615 477** LAC (Lookahead Correction) for syntax error handling:
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478
479 Canonical LR, IELR, and LALR can suffer from a couple of problems
480 upon encountering a syntax error. First, the parser might perform
481 additional parser stack reductions before discovering the syntax
7fceb615 482 error. Such reductions can perform user semantic actions that are
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483 unexpected because they are based on an invalid token, and they
484 cause error recovery to begin in a different syntactic context than
485 the one in which the invalid token was encountered. Second, when
7fceb615 486 verbose error messages are enabled (with %error-verbose or the
e4ab1254 487 obsolete "#define YYERROR_VERBOSE"), the expected token list in the
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488 syntax error message can both contain invalid tokens and omit valid
489 tokens.
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490
491 The culprits for the above problems are %nonassoc, default
492 reductions in inconsistent states, and parser state merging. Thus,
493 IELR and LALR suffer the most. Canonical LR can suffer only if
494 %nonassoc is used or if default reductions are enabled for
495 inconsistent states.
496
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497 LAC is a new mechanism within the parsing algorithm that solves
498 these problems for canonical LR, IELR, and LALR without sacrificing
499 %nonassoc, default reductions, or state merging. When LAC is in
500 use, canonical LR and IELR behave almost exactly the same for both
501 syntactically acceptable and syntactically unacceptable input.
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502 While LALR still does not support the full language-recognition
503 power of canonical LR and IELR, LAC at least enables LALR's syntax
504 error handling to correctly reflect LALR's language-recognition
505 power.
506
507 Currently, LAC is only supported for deterministic parsers in C.
508 You can enable LAC with the following directive:
509
510 %define parse.lac full
511
e4ab1254 512 See the new section "LAC" in the Bison manual for additional
7fceb615 513 details including a few caveats.
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514
515 LAC is an experimental feature. More user feedback will help to
516 stabilize it.
517
d397d9f0 518** %define improvements:
cf499cff 519
f1b238df 520*** Can now be invoked via the command line:
50cca368 521
de5ab940 522 Each of these command-line options
50cca368 523
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524 -D NAME[=VALUE]
525 --define=NAME[=VALUE]
526
527 -F NAME[=VALUE]
528 --force-define=NAME[=VALUE]
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529
530 is equivalent to this grammar file declaration
531
de5ab940 532 %define NAME ["VALUE"]
50cca368 533
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534 except that the manner in which Bison processes multiple definitions
535 for the same NAME differs. Most importantly, -F and --force-define
536 quietly override %define, but -D and --define do not. For further
e4ab1254 537 details, see the section "Bison Options" in the Bison manual.
50cca368 538
f1b238df 539*** Variables renamed:
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540
541 The following %define variables
542
543 api.push_pull
544 lr.keep_unreachable_states
545
546 have been renamed to
547
548 api.push-pull
549 lr.keep-unreachable-states
550
551 The old names are now deprecated but will be maintained indefinitely
552 for backward compatibility.
553
7262f54f 554*** Values no longer need to be quoted in the grammar file:
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555
556 If a %define value is an identifier, it no longer needs to be placed
557 within quotations marks. For example,
558
559 %define api.push-pull "push"
560
561 can be rewritten as
562
563 %define api.push-pull push
564
d397d9f0 565*** Unrecognized variables are now errors not warnings.
cdf3f113 566
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567*** Multiple invocations for any variable is now an error not a warning.
568
569** Unrecognized %code qualifiers are now errors not warnings.
570
571** Character literals not of length one:
572
573 Previously, Bison quietly converted all character literals to length
574 one. For example, without warning, Bison interpreted the operators in
575 the following grammar to be the same token:
576
577 exp: exp '++'
578 | exp '+' exp
579 ;
580
581 Bison now warns when a character literal is not of length one. In
582 some future release, Bison will start reporting an error instead.
583
584** Destructor calls fixed for lookaheads altered in semantic actions:
585
586 Previously for deterministic parsers in C, if a user semantic action
587 altered yychar, the parser in some cases used the old yychar value to
588 determine which destructor to call for the lookahead upon a syntax
589 error or upon parser return. This bug has been fixed.
590
591** C++ parsers use YYRHSLOC:
592
593 Similarly to the C parsers, the C++ parsers now define the YYRHSLOC
594 macro and use it in the default YYLLOC_DEFAULT. You are encouraged
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595 to use it. If, for instance, your location structure has "first"
596 and "last" members, instead of
d397d9f0 597
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598 # define YYLLOC_DEFAULT(Current, Rhs, N) \
599 do \
600 if (N) \
601 { \
602 (Current).first = (Rhs)[1].location.first; \
603 (Current).last = (Rhs)[N].location.last; \
604 } \
605 else \
606 { \
607 (Current).first = (Current).last = (Rhs)[0].location.last; \
608 } \
609 while (false)
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610
611 use:
612
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613 # define YYLLOC_DEFAULT(Current, Rhs, N) \
614 do \
615 if (N) \
616 { \
617 (Current).first = YYRHSLOC (Rhs, 1).first; \
618 (Current).last = YYRHSLOC (Rhs, N).last; \
619 } \
620 else \
621 { \
622 (Current).first = (Current).last = YYRHSLOC (Rhs, 0).last; \
623 } \
624 while (false)
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625
626** YYLLOC_DEFAULT in C++:
627
628 The default implementation of YYLLOC_DEFAULT used to be issued in
629 the header file. It is now output in the implementation file, after
630 the user %code sections so that its #ifndef guard does not try to
631 override the user's YYLLOC_DEFAULT if provided.
cdf3f113 632
f1b238df 633** YYFAIL now produces warnings and Java parsers no longer implement it:
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634
635 YYFAIL has existed for many years as an undocumented feature of
636 deterministic parsers in C generated by Bison. More recently, it was
637 a documented feature of Bison's experimental Java parsers. As
638 promised in Bison 2.4.2's NEWS entry, any appearance of YYFAIL in a
639 semantic action now produces a deprecation warning, and Java parsers
640 no longer implement YYFAIL at all. For further details, including a
641 discussion of how to suppress C preprocessor warnings about YYFAIL
642 being unused, see the Bison 2.4.2 NEWS entry.
643
f1b238df 644** Temporary hack for adding a semicolon to the user action:
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645
646 Previously, Bison appended a semicolon to every user action for
647 reductions when the output language defaulted to C (specifically, when
648 neither %yacc, %language, %skeleton, or equivalent command-line
649 options were specified). This allowed actions such as
650
651 exp: exp "+" exp { $$ = $1 + $3 };
652
653 instead of
654
655 exp: exp "+" exp { $$ = $1 + $3; };
656
657 As a first step in removing this misfeature, Bison now issues a
658 warning when it appends a semicolon. Moreover, in cases where Bison
659 cannot easily determine whether a semicolon is needed (for example, an
660 action ending with a cpp directive or a braced compound initializer),
661 it no longer appends one. Thus, the C compiler might now complain
662 about a missing semicolon where it did not before. Future releases of
663 Bison will cease to append semicolons entirely.
664
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665** Verbose syntax error message fixes:
666
e4ab1254 667 When %error-verbose or the obsolete "#define YYERROR_VERBOSE" is
7fceb615
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668 specified, syntax error messages produced by the generated parser
669 include the unexpected token as well as a list of expected tokens.
670 The effect of %nonassoc on these verbose messages has been corrected
671 in two ways, but a more complete fix requires LAC, described above:
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672
673*** When %nonassoc is used, there can exist parser states that accept no
674 tokens, and so the parser does not always require a lookahead token
675 in order to detect a syntax error. Because no unexpected token or
676 expected tokens can then be reported, the verbose syntax error
677 message described above is suppressed, and the parser instead
e4ab1254 678 reports the simpler message, "syntax error". Previously, this
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679 suppression was sometimes erroneously triggered by %nonassoc when a
680 lookahead was actually required. Now verbose messages are
681 suppressed only when all previous lookaheads have already been
682 shifted or discarded.
683
684*** Previously, the list of expected tokens erroneously included tokens
685 that would actually induce a syntax error because conflicts for them
686 were resolved with %nonassoc in the current parser state. Such
687 tokens are now properly omitted from the list.
688
689*** Expected token lists are still often wrong due to state merging
fcf834f9
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690 (from LALR or IELR) and default reductions, which can both add
691 invalid tokens and subtract valid tokens. Canonical LR almost
692 completely fixes this problem by eliminating state merging and
693 default reductions. However, there is one minor problem left even
694 when using canonical LR and even after the fixes above. That is,
695 if the resolution of a conflict with %nonassoc appears in a later
696 parser state than the one at which some syntax error is
697 discovered, the conflicted token is still erroneously included in
698 the expected token list. Bison's new LAC implementation,
699 described above, eliminates this problem and the need for
700 canonical LR. However, LAC is still experimental and is disabled
701 by default.
53f036ce 702
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703** Java skeleton fixes:
704
705*** A location handling bug has been fixed.
706
707*** The top element of each of the value stack and location stack is now
708 cleared when popped so that it can be garbage collected.
6771a463 709
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710*** Parser traces now print the top element of the stack.
711
86408959
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712** -W/--warnings fixes:
713
e4ab1254 714*** Bison now properly recognizes the "no-" versions of categories:
86408959
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715
716 For example, given the following command line, Bison now enables all
717 warnings except warnings for incompatibilities with POSIX Yacc:
718
719 bison -Wall,no-yacc gram.y
720
786743d5
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721*** Bison now treats S/R and R/R conflicts like other warnings:
722
723 Previously, conflict reports were independent of Bison's normal
724 warning system. Now, Bison recognizes the warning categories
e4ab1254 725 "conflicts-sr" and "conflicts-rr". This change has important
786743d5
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726 consequences for the -W and --warnings command-line options. For
727 example:
728
729 bison -Wno-conflicts-sr gram.y # S/R conflicts not reported
730 bison -Wno-conflicts-rr gram.y # R/R conflicts not reported
731 bison -Wnone gram.y # no conflicts are reported
732 bison -Werror gram.y # any conflict is an error
733
734 However, as before, if the %expect or %expect-rr directive is
735 specified, an unexpected number of conflicts is an error, and an
736 expected number of conflicts is not reported, so -W and --warning
737 then have no effect on the conflict report.
738
e4ab1254 739*** The "none" category no longer disables a preceding "error":
bf0e44e8
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740
741 For example, for the following command line, Bison now reports
742 errors instead of warnings for incompatibilities with POSIX Yacc:
743
744 bison -Werror,none,yacc gram.y
745
e4ab1254 746*** The "none" category now disables all Bison warnings:
c39014ae 747
e4ab1254 748 Previously, the "none" category disabled only Bison warnings for
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749 which there existed a specific -W/--warning category. However,
750 given the following command line, Bison is now guaranteed to
751 suppress all warnings:
752
753 bison -Wnone gram.y
754
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755** Precedence directives can now assign token number 0:
756
757 Since Bison 2.3b, which restored the ability of precedence
758 directives to assign token numbers, doing so for token number 0 has
759 produced an assertion failure. For example:
760
761 %left END 0
762
763 This bug has been fixed.
764
64877e5e 765* Changes in version 2.4.3 (2010-08-05):
8b9e021f 766
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767** Bison now obeys -Werror and --warnings=error for warnings about
768 grammar rules that are useless in the parser due to conflicts.
769
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770** Problems with spawning M4 on at least FreeBSD 8 and FreeBSD 9 have
771 been fixed.
772
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773** Failures in the test suite for GCC 4.5 have been fixed.
774
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775** Failures in the test suite for some versions of Sun Studio C++ have
776 been fixed.
777
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778** Contrary to Bison 2.4.2's NEWS entry, it has been decided that
779 warnings about undefined %prec identifiers will not be converted to
780 errors in Bison 2.5. They will remain warnings, which should be
781 sufficient for POSIX while avoiding backward compatibility issues.
782
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783** Minor documentation fixes.
784
e19a049c 785* Changes in version 2.4.2 (2010-03-20):
74553c98 786
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787** Some portability problems that resulted in failures and livelocks
788 in the test suite on some versions of at least Solaris, AIX, HP-UX,
e19a049c
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789 RHEL4, and Tru64 have been addressed. As a result, fatal Bison
790 errors should no longer cause M4 to report a broken pipe on the
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791 affected platforms.
792
e4ab1254 793** "%prec IDENTIFIER" requires IDENTIFIER to be defined separately.
8bb3a2e7
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794
795 POSIX specifies that an error be reported for any identifier that does
796 not appear on the LHS of a grammar rule and that is not defined by
797 %token, %left, %right, or %nonassoc. Bison 2.3b and later lost this
798 error report for the case when an identifier appears only after a
799 %prec directive. It is now restored. However, for backward
800 compatibility with recent Bison releases, it is only a warning for
801 now. In Bison 2.5 and later, it will return to being an error.
9b5049bd
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802 [Between the 2.4.2 and 2.4.3 releases, it was decided that this
803 warning will not be converted to an error in Bison 2.5.]
8bb3a2e7 804
d8911864
EB
805** Detection of GNU M4 1.4.6 or newer during configure is improved.
806
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807** Warnings from gcc's -Wundef option about undefined YYENABLE_NLS,
808 YYLTYPE_IS_TRIVIAL, and __STRICT_ANSI__ in C/C++ parsers are now
809 avoided.
c938d650 810
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811** %code is now a permanent feature.
812
813 A traditional Yacc prologue directive is written in the form:
814
815 %{CODE%}
816
817 To provide a more flexible alternative, Bison 2.3b introduced the
818 %code directive with the following forms for C/C++:
819
820 %code {CODE}
821 %code requires {CODE}
822 %code provides {CODE}
823 %code top {CODE}
824
825 These forms are now considered permanent features of Bison. See the
826 %code entries in the section "Bison Declaration Summary" in the Bison
827 manual for a summary of their functionality. See the section
828 "Prologue Alternatives" for a detailed discussion including the
829 advantages of %code over the traditional Yacc prologue directive.
830
831 Bison's Java feature as a whole including its current usage of %code
832 is still considered experimental.
833
1625df5b
JD
834** YYFAIL is deprecated and will eventually be removed.
835
836 YYFAIL has existed for many years as an undocumented feature of
837 deterministic parsers in C generated by Bison. Previously, it was
838 documented for Bison's experimental Java parsers. YYFAIL is no longer
839 documented for Java parsers and is formally deprecated in both cases.
840 Users are strongly encouraged to migrate to YYERROR, which is
841 specified by POSIX.
842
843 Like YYERROR, you can invoke YYFAIL from a semantic action in order to
844 induce a syntax error. The most obvious difference from YYERROR is
845 that YYFAIL will automatically invoke yyerror to report the syntax
846 error so that you don't have to. However, there are several other
847 subtle differences between YYERROR and YYFAIL, and YYFAIL suffers from
e4ab1254 848 inherent flaws when %error-verbose or "#define YYERROR_VERBOSE" is
1625df5b
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849 used. For a more detailed discussion, see:
850
851 http://lists.gnu.org/archive/html/bison-patches/2009-12/msg00024.html
852
853 The upcoming Bison 2.5 will remove YYFAIL from Java parsers, but
854 deterministic parsers in C will continue to implement it. However,
855 because YYFAIL is already flawed, it seems futile to try to make new
856 Bison features compatible with it. Thus, during parser generation,
857 Bison 2.5 will produce a warning whenever it discovers YYFAIL in a
858 rule action. In a later release, YYFAIL will be disabled for
e4ab1254 859 %error-verbose and "#define YYERROR_VERBOSE". Eventually, YYFAIL will
1625df5b
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860 be removed altogether.
861
862 There exists at least one case where Bison 2.5's YYFAIL warning will
863 be a false positive. Some projects add phony uses of YYFAIL and other
864 Bison-defined macros for the sole purpose of suppressing C
865 preprocessor warnings (from GCC cpp's -Wunused-macros, for example).
866 To avoid Bison's future warning, such YYFAIL uses can be moved to the
e4ab1254 867 epilogue (that is, after the second "%%") in the Bison input file. In
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JD
868 this release (2.4.2), Bison already generates its own code to suppress
869 C preprocessor warnings for YYFAIL, so projects can remove their own
870 phony uses of YYFAIL if compatibility with Bison releases prior to
871 2.4.2 is not necessary.
872
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873** Internationalization.
874
875 Fix a regression introduced in Bison 2.4: Under some circumstances,
876 message translations were not installed although supported by the
877 host system.
878
74553c98 879* Changes in version 2.4.1 (2008-12-11):
c9ba9e59 880
0ea583d2
AD
881** In the GLR defines file, unexpanded M4 macros in the yylval and yylloc
882 declarations have been fixed.
1979121c 883
0ea583d2
AD
884** Temporary hack for adding a semicolon to the user action.
885
886 Bison used to prepend a trailing semicolon at the end of the user
887 action for reductions. This allowed actions such as
888
889 exp: exp "+" exp { $$ = $1 + $3 };
890
891 instead of
892
893 exp: exp "+" exp { $$ = $1 + $3; };
894
e4ab1254 895 Some grammars still depend on this "feature". Bison 2.4.1 restores
0ea583d2
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896 the previous behavior in the case of C output (specifically, when
897 neither %language or %skeleton or equivalent command-line options
898 are used) to leave more time for grammars depending on the old
899 behavior to be adjusted. Future releases of Bison will disable this
900 feature.
901
902** A few minor improvements to the Bison manual.
c9ba9e59 903
402b123d 904* Changes in version 2.4 (2008-11-02):
7bd1665a 905
402b123d 906** %language is an experimental feature.
ed4d67dc
JD
907
908 We first introduced this feature in test release 2.3b as a cleaner
909 alternative to %skeleton. Since then, we have discussed the possibility of
910 modifying its effect on Bison's output file names. Thus, in this release,
911 we consider %language to be an experimental feature that will likely evolve
912 in future releases.
7bd1665a 913
402b123d 914** Forward compatibility with GNU M4 has been improved.
241fda7a 915
402b123d 916** Several bugs in the C++ skeleton and the experimental Java skeleton have been
241fda7a
JD
917 fixed.
918
402b123d 919* Changes in version 2.3b (2008-05-27):
35fe0834 920
402b123d 921** The quotes around NAME that used to be required in the following directive
d9df47b6
JD
922 are now deprecated:
923
924 %define NAME "VALUE"
925
e4ab1254 926** The directive "%pure-parser" is now deprecated in favor of:
d9df47b6
JD
927
928 %define api.pure
929
930 which has the same effect except that Bison is more careful to warn about
931 unreasonable usage in the latter case.
932
402b123d 933** Push Parsing
c373bf8b
JD
934
935 Bison can now generate an LALR(1) parser in C with a push interface. That
e4ab1254
AD
936 is, instead of invoking "yyparse", which pulls tokens from "yylex", you can
937 push one token at a time to the parser using "yypush_parse", which will
c373bf8b
JD
938 return to the caller after processing each token. By default, the push
939 interface is disabled. Either of the following directives will enable it:
940
941 %define api.push_pull "push" // Just push; does not require yylex.
942 %define api.push_pull "both" // Push and pull; requires yylex.
943
e4ab1254 944 See the new section "A Push Parser" in the Bison manual for details.
c373bf8b 945
59da312b
JD
946 The current push parsing interface is experimental and may evolve. More user
947 feedback will help to stabilize it.
948
402b123d 949** The -g and --graph options now output graphs in Graphviz DOT format,
8e55b3aa
JD
950 not VCG format. Like --graph, -g now also takes an optional FILE argument
951 and thus cannot be bundled with other short options.
c373bf8b 952
402b123d 953** Java
59da312b
JD
954
955 Bison can now generate an LALR(1) parser in Java. The skeleton is
e4ab1254 956 "data/lalr1.java". Consider using the new %language directive instead of
59da312b
JD
957 %skeleton to select it.
958
e4ab1254 959 See the new section "Java Parsers" in the Bison manual for details.
59da312b
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960
961 The current Java interface is experimental and may evolve. More user
962 feedback will help to stabilize it.
963
402b123d 964** %language
59da312b
JD
965
966 This new directive specifies the programming language of the generated
d43f77e7
PB
967 parser, which can be C (the default), C++, or Java. Besides the skeleton
968 that Bison uses, the directive affects the names of the generated files if
969 the grammar file's name ends in ".y".
59da312b 970
402b123d 971** XML Automaton Report
59da312b
JD
972
973 Bison can now generate an XML report of the LALR(1) automaton using the new
e4ab1254 974 "--xml" option. The current XML schema is experimental and may evolve. More
59da312b 975 user feedback will help to stabilize it.
c373bf8b 976
402b123d 977** The grammar file may now specify the name of the parser header file using
c373bf8b
JD
978 %defines. For example:
979
980 %defines "parser.h"
981
402b123d 982** When reporting useless rules, useless nonterminals, and unused terminals,
d80fb37a
JD
983 Bison now employs the terms "useless in grammar" instead of "useless",
984 "useless in parser" instead of "never reduced", and "unused in grammar"
985 instead of "unused".
cff03fb2 986
402b123d 987** Unreachable State Removal
c373bf8b
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988
989 Previously, Bison sometimes generated parser tables containing unreachable
31984206
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990 states. A state can become unreachable during conflict resolution if Bison
991 disables a shift action leading to it from a predecessor state. Bison now:
75ad86ee
JD
992
993 1. Removes unreachable states.
994
995 2. Does not report any conflicts that appeared in unreachable states.
996 WARNING: As a result, you may need to update %expect and %expect-rr
997 directives in existing grammar files.
998
999 3. For any rule used only in such states, Bison now reports the rule as
cff03fb2 1000 "useless in parser due to conflicts".
75ad86ee 1001
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JD
1002 This feature can be disabled with the following directive:
1003
1004 %define lr.keep_unreachable_states
1005
e4ab1254 1006 See the %define entry in the "Bison Declaration Summary" in the Bison manual
31984206
JD
1007 for further discussion.
1008
e4ab1254 1009** Lookahead Set Correction in the ".output" Report
b1cc23c4 1010
e4ab1254
AD
1011 When instructed to generate a ".output" file including lookahead sets
1012 (using "--report=lookahead", for example), Bison now prints each reduction's
88c78747
JD
1013 lookahead set only next to the associated state's one item that (1) is
1014 associated with the same rule as the reduction and (2) has its dot at the end
1015 of its RHS. Previously, Bison also erroneously printed the lookahead set
1016 next to all of the state's other items associated with the same rule. This
e4ab1254 1017 bug affected only the ".output" file and not the generated parser source
88c78747
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1018 code.
1019
e4ab1254 1020** --report-file=FILE is a new option to override the default ".output" file
59da312b 1021 name.
1bb2bd75 1022
e4ab1254 1023** The "=" that used to be required in the following directives is now
02975b9a
JD
1024 deprecated:
1025
1026 %file-prefix "parser"
1027 %name-prefix "c_"
1028 %output "parser.c"
1029
e4ab1254 1030** An Alternative to "%{...%}" -- "%code QUALIFIER {CODE}"
c373bf8b
JD
1031
1032 Bison 2.3a provided a new set of directives as a more flexible alternative to
8e0a5e9e
JD
1033 the traditional Yacc prologue blocks. Those have now been consolidated into
1034 a single %code directive with an optional qualifier field, which identifies
1035 the purpose of the code and thus the location(s) where Bison should generate
1036 it:
1037
e4ab1254
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1038 1. "%code {CODE}" replaces "%after-header {CODE}"
1039 2. "%code requires {CODE}" replaces "%start-header {CODE}"
1040 3. "%code provides {CODE}" replaces "%end-header {CODE}"
1041 4. "%code top {CODE}" replaces "%before-header {CODE}"
8e0a5e9e 1042
e4ab1254
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1043 See the %code entries in section "Bison Declaration Summary" in the Bison
1044 manual for a summary of the new functionality. See the new section "Prologue
1045 Alternatives" for a detailed discussion including the advantages of %code
8e0a5e9e
JD
1046 over the traditional Yacc prologues.
1047
1048 The prologue alternatives are experimental. More user feedback will help to
1049 determine whether they should become permanent features.
1050
402b123d 1051** Revised warning: unset or unused mid-rule values
17bd8a73
JD
1052
1053 Since Bison 2.2, Bison has warned about mid-rule values that are set but not
1054 used within any of the actions of the parent rule. For example, Bison warns
1055 about unused $2 in:
1056
1057 exp: '1' { $$ = 1; } '+' exp { $$ = $1 + $4; };
1058
1059 Now, Bison also warns about mid-rule values that are used but not set. For
1060 example, Bison warns about unset $$ in the mid-rule action in:
1061
1062 exp: '1' { $1 = 1; } '+' exp { $$ = $2 + $4; };
1063
1064 However, Bison now disables both of these warnings by default since they
1065 sometimes prove to be false alarms in existing grammars employing the Yacc
1066 constructs $0 or $-N (where N is some positive integer).
1067
e4ab1254
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1068 To enable these warnings, specify the option "--warnings=midrule-values" or
1069 "-W", which is a synonym for "--warnings=all".
17bd8a73 1070
e4ab1254 1071** Default %destructor or %printer with "<*>" or "<>"
c373bf8b
JD
1072
1073 Bison now recognizes two separate kinds of default %destructor's and
12e35840
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1074 %printer's:
1075
e4ab1254 1076 1. Place "<*>" in a %destructor/%printer symbol list to define a default
12e35840
JD
1077 %destructor/%printer for all grammar symbols for which you have formally
1078 declared semantic type tags.
1079
e4ab1254 1080 2. Place "<>" in a %destructor/%printer symbol list to define a default
12e35840
JD
1081 %destructor/%printer for all grammar symbols without declared semantic
1082 type tags.
1083
e4ab1254
AD
1084 Bison no longer supports the "%symbol-default" notation from Bison 2.3a.
1085 "<*>" and "<>" combined achieve the same effect with one exception: Bison no
12e35840
JD
1086 longer applies any %destructor to a mid-rule value if that mid-rule value is
1087 not actually ever referenced using either $$ or $n in a semantic action.
1088
85894313
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1089 The default %destructor's and %printer's are experimental. More user
1090 feedback will help to determine whether they should become permanent
1091 features.
1092
e4ab1254 1093 See the section "Freeing Discarded Symbols" in the Bison manual for further
12e35840
JD
1094 details.
1095
402b123d 1096** %left, %right, and %nonassoc can now declare token numbers. This is required
e4ab1254 1097 by POSIX. However, see the end of section "Operator Precedence" in the Bison
ab7f29f8
JD
1098 manual for a caveat concerning the treatment of literal strings.
1099
402b123d 1100** The nonfunctional --no-parser, -n, and %no-parser options have been
b1cc23c4
JD
1101 completely removed from Bison.
1102
402b123d 1103* Changes in version 2.3a, 2006-09-13:
742e4900 1104
402b123d 1105** Instead of %union, you can define and use your own union type
ddc8ede1
PE
1106 YYSTYPE if your grammar contains at least one <type> tag.
1107 Your YYSTYPE need not be a macro; it can be a typedef.
1108 This change is for compatibility with other Yacc implementations,
1109 and is required by POSIX.
1110
402b123d 1111** Locations columns and lines start at 1.
cd48d21d
AD
1112 In accordance with the GNU Coding Standards and Emacs.
1113
402b123d 1114** You may now declare per-type and default %destructor's and %printer's:
ec5479ce
JD
1115
1116 For example:
1117
b2a0b7ca
JD
1118 %union { char *string; }
1119 %token <string> STRING1
1120 %token <string> STRING2
1121 %type <string> string1
1122 %type <string> string2
1123 %union { char character; }
1124 %token <character> CHR
1125 %type <character> chr
1126 %destructor { free ($$); } %symbol-default
1127 %destructor { free ($$); printf ("%d", @$.first_line); } STRING1 string1
1128 %destructor { } <character>
1129
1130 guarantees that, when the parser discards any user-defined symbol that has a
e4ab1254
AD
1131 semantic type tag other than "<character>", it passes its semantic value to
1132 "free". However, when the parser discards a "STRING1" or a "string1", it
1133 also prints its line number to "stdout". It performs only the second
1134 "%destructor" in this case, so it invokes "free" only once.
ec5479ce 1135
85894313
JD
1136 [Although we failed to mention this here in the 2.3a release, the default
1137 %destructor's and %printer's were experimental, and they were rewritten in
1138 future versions.]
1139
e4ab1254
AD
1140** Except for LALR(1) parsers in C with POSIX Yacc emulation enabled (with "-y",
1141 "--yacc", or "%yacc"), Bison no longer generates #define statements for
b931235e
JD
1142 associating token numbers with token names. Removing the #define statements
1143 helps to sanitize the global namespace during preprocessing, but POSIX Yacc
1144 requires them. Bison still generates an enum for token names in all cases.
1145
402b123d 1146** Handling of traditional Yacc prologue blocks is now more consistent but
34f98f46 1147 potentially incompatible with previous releases of Bison.
9bc0dd67
JD
1148
1149 As before, you declare prologue blocks in your grammar file with the
e4ab1254 1150 "%{ ... %}" syntax. To generate the pre-prologue, Bison concatenates all
34f98f46
JD
1151 prologue blocks that you've declared before the first %union. To generate
1152 the post-prologue, Bison concatenates all prologue blocks that you've
ddc8ede1 1153 declared after the first %union.
9bc0dd67 1154
34f98f46 1155 Previous releases of Bison inserted the pre-prologue into both the header
9bc0dd67
JD
1156 file and the code file in all cases except for LALR(1) parsers in C. In the
1157 latter case, Bison inserted it only into the code file. For parsers in C++,
1158 the point of insertion was before any token definitions (which associate
1159 token numbers with names). For parsers in C, the point of insertion was
1160 after the token definitions.
1161
1162 Now, Bison never inserts the pre-prologue into the header file. In the code
1163 file, it always inserts it before the token definitions.
1164
402b123d 1165** Bison now provides a more flexible alternative to the traditional Yacc
34f98f46
JD
1166 prologue blocks: %before-header, %start-header, %end-header, and
1167 %after-header.
1168
1169 For example, the following declaration order in the grammar file reflects the
1170 order in which Bison will output these code blocks. However, you are free to
1171 declare these code blocks in your grammar file in whatever order is most
1172 convenient for you:
1173
1174 %before-header {
1175 /* Bison treats this block like a pre-prologue block: it inserts it into
1176 * the code file before the contents of the header file. It does *not*
1177 * insert it into the header file. This is a good place to put
1178 * #include's that you want at the top of your code file. A common
e4ab1254 1179 * example is '#include "system.h"'. */
34f98f46
JD
1180 }
1181 %start-header {
1182 /* Bison inserts this block into both the header file and the code file.
1183 * In both files, the point of insertion is before any Bison-generated
1184 * token, semantic type, location type, and class definitions. This is a
1185 * good place to define %union dependencies, for example. */
9bc0dd67
JD
1186 }
1187 %union {
34f98f46
JD
1188 /* Unlike the traditional Yacc prologue blocks, the output order for the
1189 * new %*-header blocks is not affected by their declaration position
1190 * relative to any %union in the grammar file. */
9bc0dd67 1191 }
34f98f46
JD
1192 %end-header {
1193 /* Bison inserts this block into both the header file and the code file.
1194 * In both files, the point of insertion is after the Bison-generated
1195 * definitions. This is a good place to declare or define public
1196 * functions or data structures that depend on the Bison-generated
1197 * definitions. */
9bc0dd67 1198 }
34f98f46
JD
1199 %after-header {
1200 /* Bison treats this block like a post-prologue block: it inserts it into
1201 * the code file after the contents of the header file. It does *not*
1202 * insert it into the header file. This is a good place to declare or
1203 * define internal functions or data structures that depend on the
1204 * Bison-generated definitions. */
1205 }
1206
1207 If you have multiple occurrences of any one of the above declarations, Bison
1208 will concatenate the contents in declaration order.
9bc0dd67 1209
85894313
JD
1210 [Although we failed to mention this here in the 2.3a release, the prologue
1211 alternatives were experimental, and they were rewritten in future versions.]
1212
e4ab1254 1213** The option "--report=look-ahead" has been changed to "--report=lookahead".
9e6e7ed2
PE
1214 The old spelling still works, but is not documented and may be removed
1215 in a future release.
742e4900 1216
402b123d 1217* Changes in version 2.3, 2006-06-05:
4ad3ed84 1218
e4ab1254 1219** GLR grammars should now use "YYRECOVERING ()" instead of "YYRECOVERING",
4ad3ed84
PE
1220 for compatibility with LALR(1) grammars.
1221
402b123d 1222** It is now documented that any definition of YYSTYPE or YYLTYPE should
4ad3ed84
PE
1223 be to a type name that does not contain parentheses or brackets.
1224
402b123d 1225* Changes in version 2.2, 2006-05-19:
193d7c70 1226
402b123d 1227** The distribution terms for all Bison-generated parsers now permit
193d7c70
PE
1228 using the parsers in nonfree programs. Previously, this permission
1229 was granted only for Bison-generated LALR(1) parsers in C.
5f4236a0 1230
402b123d 1231** %name-prefix changes the namespace name in C++ outputs.
aa08666d 1232
402b123d 1233** The C++ parsers export their token_type.
5f4236a0 1234
402b123d 1235** Bison now allows multiple %union declarations, and concatenates
d6ca7905
PE
1236 their contents together.
1237
402b123d 1238** New warning: unused values
4d7bc38c
PE
1239 Right-hand side symbols whose values are not used are reported,
1240 if the symbols have destructors. For instance:
affac613 1241
8f3596a6 1242 exp: exp "?" exp ":" exp { $1 ? $1 : $3; }
e9690142
JD
1243 | exp "+" exp
1244 ;
affac613 1245
8f3596a6
AD
1246 will trigger a warning about $$ and $5 in the first rule, and $3 in
1247 the second ($1 is copied to $$ by the default rule). This example
4e26c69e 1248 most likely contains three errors, and could be rewritten as:
affac613 1249
4e26c69e 1250 exp: exp "?" exp ":" exp
e9690142
JD
1251 { $$ = $1 ? $3 : $5; free ($1 ? $5 : $3); free ($1); }
1252 | exp "+" exp
1253 { $$ = $1 ? $1 : $3; if ($1) free ($3); }
1254 ;
affac613 1255
4e26c69e
PE
1256 However, if the original actions were really intended, memory leaks
1257 and all, the warnings can be suppressed by letting Bison believe the
1258 values are used, e.g.:
721be13c 1259
8f3596a6 1260 exp: exp "?" exp ":" exp { $1 ? $1 : $3; (void) ($$, $5); }
e9690142
JD
1261 | exp "+" exp { $$ = $1; (void) $3; }
1262 ;
721be13c 1263
84866159
AD
1264 If there are mid-rule actions, the warning is issued if no action
1265 uses it. The following triggers no warning: $1 and $3 are used.
1266
1267 exp: exp { push ($1); } '+' exp { push ($3); sum (); };
1268
721be13c
PE
1269 The warning is intended to help catching lost values and memory leaks.
1270 If a value is ignored, its associated memory typically is not reclaimed.
affac613 1271
402b123d 1272** %destructor vs. YYABORT, YYACCEPT, and YYERROR.
9d9b8b70
PE
1273 Destructors are now called when user code invokes YYABORT, YYACCEPT,
1274 and YYERROR, for all objects on the stack, other than objects
1275 corresponding to the right-hand side of the current rule.
a85284cf 1276
402b123d 1277** %expect, %expect-rr
035aa4a0
PE
1278 Incorrect numbers of expected conflicts are now actual errors,
1279 instead of warnings.
1280
402b123d 1281** GLR, YACC parsers.
4e26c69e
PE
1282 The %parse-params are available in the destructors (and the
1283 experimental printers) as per the documentation.
4b367315 1284
e4ab1254 1285** Bison now warns if it finds a stray "$" or "@" in an action.
ad6a9b97 1286
402b123d 1287** %require "VERSION"
4e26c69e
PE
1288 This specifies that the grammar file depends on features implemented
1289 in Bison version VERSION or higher.
b50d2359 1290
402b123d 1291** lalr1.cc: The token and value types are now class members.
e14d0ab6
AD
1292 The tokens were defined as free form enums and cpp macros. YYSTYPE
1293 was defined as a free form union. They are now class members:
e4ab1254
AD
1294 tokens are enumerations of the "yy::parser::token" struct, and the
1295 semantic values have the "yy::parser::semantic_type" type.
fb9712a9
AD
1296
1297 If you do not want or can update to this scheme, the directive
e4ab1254 1298 '%define "global_tokens_and_yystype" "1"' triggers the global
b50d2359
AD
1299 definition of tokens and YYSTYPE. This change is suitable both
1300 for previous releases of Bison, and this one.
fb9712a9 1301
b50d2359 1302 If you wish to update, then make sure older version of Bison will
e4ab1254 1303 fail using '%require "2.2"'.
fb9712a9 1304
402b123d 1305** DJGPP support added.
193d7c70 1306\f
402b123d 1307* Changes in version 2.1, 2005-09-16:
1ce59070 1308
402b123d 1309** The C++ lalr1.cc skeleton supports %lex-param.
e14d0ab6 1310
402b123d 1311** Bison-generated parsers now support the translation of diagnostics like
baf785db
PE
1312 "syntax error" into languages other than English. The default
1313 language is still English. For details, please see the new
0410a6e0
PE
1314 Internationalization section of the Bison manual. Software
1315 distributors should also see the new PACKAGING file. Thanks to
1316 Bruno Haible for this new feature.
1ce59070 1317
402b123d 1318** Wording in the Bison-generated parsers has been changed slightly to
1a059451
PE
1319 simplify translation. In particular, the message "memory exhausted"
1320 has replaced "parser stack overflow", as the old message was not
1321 always accurate for modern Bison-generated parsers.
1322
402b123d 1323** Destructors are now called when the parser aborts, for all symbols left
258b75ca
PE
1324 behind on the stack. Also, the start symbol is now destroyed after a
1325 successful parse. In both cases, the behavior was formerly inconsistent.
1326
402b123d 1327** When generating verbose diagnostics, Bison-generated parsers no longer
72f000b0
PE
1328 quote the literal strings associated with tokens. For example, for
1329 a syntax error associated with '%token NUM "number"' they might
1330 print 'syntax error, unexpected number' instead of 'syntax error,
1331 unexpected "number"'.
193d7c70 1332\f
402b123d 1333* Changes in version 2.0, 2004-12-25:
efeed023 1334
402b123d 1335** Possibly-incompatible changes
d7e14fc0 1336
82de6b0d
PE
1337 - Bison-generated parsers no longer default to using the alloca function
1338 (when available) to extend the parser stack, due to widespread
1339 problems in unchecked stack-overflow detection. You can "#define
1340 YYSTACK_USE_ALLOCA 1" to require the use of alloca, but please read
1341 the manual to determine safe values for YYMAXDEPTH in that case.
8dd162d3 1342
82de6b0d
PE
1343 - Error token location.
1344 During error recovery, the location of the syntax error is updated
1345 to cover the whole sequence covered by the error token: it includes
1346 the shifted symbols thrown away during the first part of the error
1347 recovery, and the lookahead rejected during the second part.
18d192f0 1348
82de6b0d
PE
1349 - Semicolon changes:
1350 . Stray semicolons are no longer allowed at the start of a grammar.
1351 . Semicolons are now required after in-grammar declarations.
e342c3be 1352
82de6b0d
PE
1353 - Unescaped newlines are no longer allowed in character constants or
1354 string literals. They were never portable, and GCC 3.4.0 has
1355 dropped support for them. Better diagnostics are now generated if
1356 forget a closing quote.
8dd162d3 1357
82de6b0d 1358 - NUL bytes are no longer allowed in Bison string literals, unfortunately.
f74b6f91 1359
402b123d 1360** New features
1452af69 1361
82de6b0d 1362 - GLR grammars now support locations.
4febdd96 1363
82de6b0d
PE
1364 - New directive: %initial-action.
1365 This directive allows the user to run arbitrary code (including
1366 initializing @$) from yyparse before parsing starts.
1452af69 1367
82de6b0d
PE
1368 - A new directive "%expect-rr N" specifies the expected number of
1369 reduce/reduce conflicts in GLR parsers.
1452af69 1370
e4ab1254 1371 - %token numbers can now be hexadecimal integers, e.g., "%token FOO 0x12d".
82de6b0d 1372 This is a GNU extension.
4febdd96 1373
e4ab1254 1374 - The option "--report=lookahead" was changed to "--report=look-ahead".
9e6e7ed2 1375 [However, this was changed back after 2.3.]
1452af69 1376
82de6b0d 1377 - Experimental %destructor support has been added to lalr1.cc.
1452af69 1378
82de6b0d
PE
1379 - New configure option --disable-yacc, to disable installation of the
1380 yacc command and -ly library introduced in 1.875 for POSIX conformance.
6040d338 1381
402b123d 1382** Bug fixes
d5a3fe37 1383
82de6b0d
PE
1384 - For now, %expect-count violations are now just warnings, not errors.
1385 This is for compatibility with Bison 1.75 and earlier (when there are
1386 reduce/reduce conflicts) and with Bison 1.30 and earlier (when there
1387 are too many or too few shift/reduce conflicts). However, in future
1388 versions of Bison we plan to improve the %expect machinery so that
1389 these violations will become errors again.
3473d0f8 1390
82de6b0d
PE
1391 - Within Bison itself, numbers (e.g., goto numbers) are no longer
1392 arbitrarily limited to 16-bit counts.
d600ee67 1393
82de6b0d 1394 - Semicolons are now allowed before "|" in grammar rules, as POSIX requires.
d600ee67 1395\f
402b123d 1396* Changes in version 1.875, 2003-01-01:
963fcc17 1397
402b123d 1398** The documentation license has been upgraded to version 1.2
dc546b0f 1399 of the GNU Free Documentation License.
75eb3bc4 1400
402b123d 1401** syntax error processing
75eb3bc4 1402
dc546b0f
PE
1403 - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error
1404 locations too. This fixes bugs in error-location computation.
75eb3bc4 1405
dc546b0f
PE
1406 - %destructor
1407 It is now possible to reclaim the memory associated to symbols
1408 discarded during error recovery. This feature is still experimental.
20daca06 1409
dc546b0f
PE
1410 - %error-verbose
1411 This new directive is preferred over YYERROR_VERBOSE.
74724a70 1412
dc546b0f
PE
1413 - #defining yyerror to steal internal variables is discouraged.
1414 It is not guaranteed to work forever.
d1de5372 1415
402b123d 1416** POSIX conformance
d1de5372 1417
dc546b0f
PE
1418 - Semicolons are once again optional at the end of grammar rules.
1419 This reverts to the behavior of Bison 1.33 and earlier, and improves
1420 compatibility with Yacc.
74724a70 1421
e4ab1254
AD
1422 - "parse error" -> "syntax error"
1423 Bison now uniformly uses the term "syntax error"; formerly, the code
1424 and manual sometimes used the term "parse error" instead. POSIX
1425 requires "syntax error" in diagnostics, and it was thought better to
dc546b0f 1426 be consistent.
74724a70 1427
dc546b0f
PE
1428 - The documentation now emphasizes that yylex and yyerror must be
1429 declared before use. C99 requires this.
d1de5372 1430
dc546b0f
PE
1431 - Bison now parses C99 lexical constructs like UCNs and
1432 backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires.
d1de5372 1433
dc546b0f
PE
1434 - File names are properly escaped in C output. E.g., foo\bar.y is
1435 output as "foo\\bar.y".
6780ca7a 1436
dc546b0f 1437 - Yacc command and library now available
e4ab1254 1438 The Bison distribution now installs a "yacc" command, as POSIX requires.
dc546b0f
PE
1439 Also, Bison now installs a small library liby.a containing
1440 implementations of Yacc-compatible yyerror and main functions.
1441 This library is normally not useful, but POSIX requires it.
6e649e65 1442
dc546b0f 1443 - Type clashes now generate warnings, not errors.
6e649e65 1444
dc546b0f
PE
1445 - If the user does not define YYSTYPE as a macro, Bison now declares it
1446 using typedef instead of defining it as a macro.
1447 For consistency, YYLTYPE is also declared instead of defined.
9501dc6e 1448
402b123d 1449** Other compatibility issues
886a425c 1450
e4ab1254
AD
1451 - %union directives can now have a tag before the "{", e.g., the
1452 directive "%union foo {...}" now generates the C code
1453 "typedef union foo { ... } YYSTYPE;"; this is for Yacc compatibility.
1454 The default union tag is "YYSTYPE", for compatibility with Solaris 9 Yacc.
1455 For consistency, YYLTYPE's struct tag is now "YYLTYPE" not "yyltype".
dc546b0f 1456 This is for compatibility with both Yacc and Bison 1.35.
72f889cc 1457
e4ab1254 1458 - ";" is output before the terminating "}" of an action, for
dc546b0f 1459 compatibility with Bison 1.35.
886a425c 1460
dc546b0f 1461 - Bison now uses a Yacc-style format for conflict reports, e.g.,
e4ab1254 1462 "conflicts: 2 shift/reduce, 1 reduce/reduce".
437c2d80 1463
e4ab1254 1464 - "yystype" and "yyltype" are now obsolescent macros instead of being
dc546b0f
PE
1465 typedefs or tags; they are no longer documented and are planned to be
1466 withdrawn in a future release.
2a8d363a 1467
402b123d 1468** GLR parser notes
2a8d363a 1469
dc546b0f
PE
1470 - GLR and inline
1471 Users of Bison have to decide how they handle the portability of the
e4ab1254 1472 C keyword "inline".
959e5f51 1473
e4ab1254
AD
1474 - "parsing stack overflow..." -> "parser stack overflow"
1475 GLR parsers now report "parser stack overflow" as per the Bison manual.
900c5db5 1476
18ad57b3
AD
1477** %parse-param and %lex-param
1478 The macros YYPARSE_PARAM and YYLEX_PARAM provide a means to pass
1479 additional context to yyparse and yylex. They suffer from several
1480 shortcomings:
1481
1482 - a single argument only can be added,
1483 - their types are weak (void *),
242cc08e 1484 - this context is not passed to ancillary functions such as yyerror,
18ad57b3
AD
1485 - only yacc.c parsers support them.
1486
1487 The new %parse-param/%lex-param directives provide a more precise control.
1488 For instance:
1489
1490 %parse-param {int *nastiness}
1491 %lex-param {int *nastiness}
1492 %parse-param {int *randomness}
1493
1494 results in the following signatures:
1495
1496 int yylex (int *nastiness);
1497 int yyparse (int *nastiness, int *randomness);
1498
1499 or, if both %pure-parser and %locations are used:
1500
1501 int yylex (YYSTYPE *lvalp, YYLTYPE *llocp, int *nastiness);
1502 int yyparse (int *nastiness, int *randomness);
1503
402b123d 1504** Bison now warns if it detects conflicting outputs to the same file,
e4ab1254 1505 e.g., it generates a warning for "bison -d -o foo.h foo.y" since
dc546b0f 1506 that command outputs both code and header to foo.h.
6e40b4eb 1507
402b123d 1508** #line in output files
dc546b0f 1509 - --no-line works properly.
6e40b4eb 1510
402b123d 1511** Bison can no longer be built by a K&R C compiler; it requires C89 or
6e40b4eb
AD
1512 later to be built. This change originally took place a few versions
1513 ago, but nobody noticed until we recently asked someone to try
1514 building Bison with a K&R C compiler.
d600ee67 1515\f
402b123d 1516* Changes in version 1.75, 2002-10-14:
7933f2b5 1517
402b123d 1518** Bison should now work on 64-bit hosts.
7933f2b5 1519
402b123d 1520** Indonesian translation thanks to Tedi Heriyanto.
7933f2b5 1521
402b123d 1522** GLR parsers
f50adbbd
AD
1523 Fix spurious parse errors.
1524
402b123d 1525** Pure parsers
f50adbbd
AD
1526 Some people redefine yyerror to steal yyparse' private variables.
1527 Reenable this trick until an official feature replaces it.
1528
402b123d 1529** Type Clashes
d90c934c
AD
1530 In agreement with POSIX and with other Yaccs, leaving a default
1531 action is valid when $$ is untyped, and $1 typed:
1532
e9690142 1533 untyped: ... typed;
d90c934c
AD
1534
1535 but the converse remains an error:
1536
e9690142 1537 typed: ... untyped;
d90c934c 1538
402b123d 1539** Values of mid-rule actions
d90c934c
AD
1540 The following code:
1541
e9690142 1542 foo: { ... } { $$ = $1; } ...
d90c934c
AD
1543
1544 was incorrectly rejected: $1 is defined in the second mid-rule
1545 action, and is equal to the $$ of the first mid-rule action.
d600ee67 1546\f
402b123d 1547* Changes in version 1.50, 2002-10-04:
adc8c848 1548
402b123d 1549** GLR parsing
676385e2
PH
1550 The declaration
1551 %glr-parser
1552 causes Bison to produce a Generalized LR (GLR) parser, capable of handling
1553 almost any context-free grammar, ambiguous or not. The new declarations
e8832397 1554 %dprec and %merge on grammar rules allow parse-time resolution of
676385e2
PH
1555 ambiguities. Contributed by Paul Hilfinger.
1556
7933f2b5 1557 Unfortunately Bison 1.50 does not work properly on 64-bit hosts
420f93c8
PE
1558 like the Alpha, so please stick to 32-bit hosts for now.
1559
402b123d 1560** Output Directory
8c165d89 1561 When not in Yacc compatibility mode, when the output file was not
e4ab1254
AD
1562 specified, running "bison foo/bar.y" created "foo/bar.c". It
1563 now creates "bar.c".
8c165d89 1564
402b123d 1565** Undefined token
007a50a4 1566 The undefined token was systematically mapped to 2 which prevented
e88dbdbf 1567 the use of 2 by the user. This is no longer the case.
007a50a4 1568
402b123d 1569** Unknown token numbers
e88dbdbf 1570 If yylex returned an out of range value, yyparse could die. This is
007a50a4
AD
1571 no longer the case.
1572
402b123d 1573** Error token
e88dbdbf 1574 According to POSIX, the error token must be 256.
23c5a174
AD
1575 Bison extends this requirement by making it a preference: *if* the
1576 user specified that one of her tokens is numbered 256, then error
1577 will be mapped onto another number.
1578
402b123d 1579** Verbose error messages
e4ab1254 1580 They no longer report "..., expecting error or..." for states where
217598da
AD
1581 error recovery is possible.
1582
402b123d 1583** End token
e4ab1254 1584 Defaults to "$end" instead of "$".
217598da 1585
402b123d 1586** Error recovery now conforms to documentation and to POSIX
68cd8af3
PE
1587 When a Bison-generated parser encounters a syntax error, it now pops
1588 the stack until it finds a state that allows shifting the error
1589 token. Formerly, it popped the stack until it found a state that
1590 allowed some non-error action other than a default reduction on the
1591 error token. The new behavior has long been the documented behavior,
1592 and has long been required by POSIX. For more details, please see
337116ba
PE
1593 Paul Eggert, "Reductions during Bison error handling" (2002-05-20)
1594 <http://lists.gnu.org/archive/html/bug-bison/2002-05/msg00038.html>.
68cd8af3 1595
402b123d 1596** Traces
5504898e
AD
1597 Popped tokens and nonterminals are now reported.
1598
402b123d 1599** Larger grammars
a861a339
PE
1600 Larger grammars are now supported (larger token numbers, larger grammar
1601 size (= sum of the LHS and RHS lengths), larger LALR tables).
1602 Formerly, many of these numbers ran afoul of 16-bit limits;
1603 now these limits are 32 bits on most hosts.
355e7c1c 1604
402b123d 1605** Explicit initial rule
643a5994
AD
1606 Bison used to play hacks with the initial rule, which the user does
1607 not write. It is now explicit, and visible in the reports and
1608 graphs as rule 0.
23c5a174 1609
402b123d 1610** Useless rules
643a5994 1611 Before, Bison reported the useless rules, but, although not used,
77714df2 1612 included them in the parsers. They are now actually removed.
23c5a174 1613
402b123d 1614** Useless rules, useless nonterminals
6b98e4b5
AD
1615 They are now reported, as a warning, with their locations.
1616
402b123d 1617** Rules never reduced
e8832397
AD
1618 Rules that can never be reduced because of conflicts are now
1619 reported.
1620
e4ab1254 1621** Incorrect "Token not used"
11652ab3
AD
1622 On a grammar such as
1623
e29f0771
AD
1624 %token useless useful
1625 %%
1626 exp: '0' %prec useful;
11652ab3
AD
1627
1628 where a token was used to set the precedence of the last rule,
e4ab1254 1629 bison reported both "useful" and "useless" as useless tokens.
11652ab3 1630
402b123d 1631** Revert the C++ namespace changes introduced in 1.31
77714df2 1632 as they caused too many portability hassles.
0179dd65 1633
402b123d 1634** Default locations
b2d52318
AD
1635 By an accident of design, the default computation of @$ was
1636 performed after another default computation was performed: @$ = @1.
1637 The latter is now removed: YYLLOC_DEFAULT is fully responsible of
1638 the computation of @$.
adc8c848 1639
402b123d 1640** Token end-of-file
b7c49edf
AD
1641 The token end of file may be specified by the user, in which case,
1642 the user symbol is used in the reports, the graphs, and the verbose
e4ab1254 1643 error messages instead of "$end", which remains being the default.
b7c49edf 1644 For instance
e29f0771 1645 %token MYEOF 0
b7c49edf 1646 or
e29f0771 1647 %token MYEOF 0 "end of file"
fdbcd8e2 1648
402b123d 1649** Semantic parser
fdbcd8e2
AD
1650 This old option, which has been broken for ages, is removed.
1651
402b123d 1652** New translations
a861a339 1653 Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
84614e13
AD
1654 Croatian, thanks to Denis Lackovic.
1655
402b123d 1656** Incorrect token definitions
e4ab1254
AD
1657 When given
1658 %token 'a' "A"
1659 bison used to output
1660 #define 'a' 65
b87f8b21 1661
402b123d 1662** Token definitions as enums
77714df2
AD
1663 Tokens are output both as the traditional #define's, and, provided
1664 the compiler supports ANSI C or is a C++ compiler, as enums.
e88dbdbf 1665 This lets debuggers display names instead of integers.
77714df2 1666
402b123d 1667** Reports
ec3bc396
AD
1668 In addition to --verbose, bison supports --report=THINGS, which
1669 produces additional information:
b408954b
AD
1670 - itemset
1671 complete the core item sets with their closure
e4ab1254 1672 - lookahead [changed to "look-ahead" in 1.875e through 2.3, but changed back]
9e6e7ed2 1673 explicitly associate lookahead tokens to items
b408954b
AD
1674 - solved
1675 describe shift/reduce conflicts solving.
1676 Bison used to systematically output this information on top of
1677 the report. Solved conflicts are now attached to their states.
ec3bc396 1678
402b123d 1679** Type clashes
9af3fbce
AD
1680 Previous versions don't complain when there is a type clash on
1681 the default action if the rule has a mid-rule action, such as in:
1682
e29f0771
AD
1683 %type <foo> bar
1684 %%
1685 bar: '0' {} '0';
9af3fbce
AD
1686
1687 This is fixed.
a861a339 1688
402b123d 1689** GNU M4 is now required when using Bison.
f987e9d2 1690\f
402b123d 1691* Changes in version 1.35, 2002-03-25:
76551463 1692
402b123d 1693** C Skeleton
76551463
AD
1694 Some projects use Bison's C parser with C++ compilers, and define
1695 YYSTYPE as a class. The recent adjustment of C parsers for data
1696 alignment and 64 bit architectures made this impossible.
1697
1698 Because for the time being no real solution for C++ parser
1699 generation exists, kludges were implemented in the parser to
1700 maintain this use. In the future, when Bison has C++ parsers, this
1701 kludge will be disabled.
1702
1703 This kludge also addresses some C++ problems when the stack was
1704 extended.
76551463 1705\f
402b123d 1706* Changes in version 1.34, 2002-03-12:
76551463 1707
402b123d 1708** File name clashes are detected
76551463 1709 $ bison foo.y -d -o foo.x
e4ab1254 1710 fatal error: header and parser would both be named "foo.x"
76551463 1711
e4ab1254 1712** A missing ";" at the end of a rule triggers a warning
76551463
AD
1713 In accordance with POSIX, and in agreement with other
1714 Yacc implementations, Bison will mandate this semicolon in the near
1715 future. This eases the implementation of a Bison parser of Bison
1716 grammars by making this grammar LALR(1) instead of LR(2). To
1717 facilitate the transition, this release introduces a warning.
1718
402b123d 1719** Revert the C++ namespace changes introduced in 1.31, as they caused too
76551463
AD
1720 many portability hassles.
1721
402b123d 1722** DJGPP support added.
76551463 1723
402b123d 1724** Fix test suite portability problems.
76551463 1725\f
402b123d 1726* Changes in version 1.33, 2002-02-07:
76551463 1727
402b123d 1728** Fix C++ issues
76551463
AD
1729 Groff could not be compiled for the definition of size_t was lacking
1730 under some conditions.
1731
402b123d 1732** Catch invalid @n
76551463
AD
1733 As is done with $n.
1734\f
402b123d 1735* Changes in version 1.32, 2002-01-23:
76551463 1736
402b123d 1737** Fix Yacc output file names
76551463 1738
402b123d 1739** Portability fixes
76551463 1740
402b123d 1741** Italian, Dutch translations
76551463 1742\f
402b123d 1743* Changes in version 1.31, 2002-01-14:
52d1aeee 1744
402b123d 1745** Many Bug Fixes
52d1aeee 1746
402b123d 1747** GNU Gettext and %expect
52d1aeee
MA
1748 GNU Gettext asserts 10 s/r conflicts, but there are 7. Now that
1749 Bison dies on incorrect %expectations, we fear there will be
1750 too many bug reports for Gettext, so _for the time being_, %expect
e4ab1254 1751 does not trigger an error when the input file is named "plural.y".
52d1aeee 1752
402b123d 1753** Use of alloca in parsers
52d1aeee
MA
1754 If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use
1755 malloc exclusively. Since 1.29, but was not NEWS'ed.
1756
1757 alloca is used only when compiled with GCC, to avoid portability
1758 problems as on AIX.
1759
402b123d 1760** yyparse now returns 2 if memory is exhausted; formerly it dumped core.
b47dbebe 1761
402b123d 1762** When the generated parser lacks debugging code, YYDEBUG is now 0
52d1aeee
MA
1763 (as POSIX requires) instead of being undefined.
1764
402b123d 1765** User Actions
52d1aeee
MA
1766 Bison has always permitted actions such as { $$ = $1 }: it adds the
1767 ending semicolon. Now if in Yacc compatibility mode, the semicolon
1768 is no longer output: one has to write { $$ = $1; }.
1769
402b123d 1770** Better C++ compliance
52d1aeee 1771 The output parsers try to respect C++ namespaces.
76551463 1772 [This turned out to be a failed experiment, and it was reverted later.]
52d1aeee 1773
402b123d 1774** Reduced Grammars
52d1aeee
MA
1775 Fixed bugs when reporting useless nonterminals.
1776
402b123d 1777** 64 bit hosts
52d1aeee
MA
1778 The parsers work properly on 64 bit hosts.
1779
402b123d 1780** Error messages
52d1aeee
MA
1781 Some calls to strerror resulted in scrambled or missing error messages.
1782
402b123d 1783** %expect
52d1aeee
MA
1784 When the number of shift/reduce conflicts is correct, don't issue
1785 any warning.
1786
402b123d 1787** The verbose report includes the rule line numbers.
52d1aeee 1788
402b123d 1789** Rule line numbers are fixed in traces.
52d1aeee 1790
402b123d 1791** Swedish translation
52d1aeee 1792
402b123d 1793** Parse errors
52d1aeee
MA
1794 Verbose parse error messages from the parsers are better looking.
1795 Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'(''
1796 Now: parse error: unexpected '/', expecting "number" or '-' or '('
1797
402b123d 1798** Fixed parser memory leaks.
52d1aeee
MA
1799 When the generated parser was using malloc to extend its stacks, the
1800 previous allocations were not freed.
1801
402b123d 1802** Fixed verbose output file.
52d1aeee
MA
1803 Some newlines were missing.
1804 Some conflicts in state descriptions were missing.
1805
402b123d 1806** Fixed conflict report.
52d1aeee
MA
1807 Option -v was needed to get the result.
1808
402b123d 1809** %expect
52d1aeee
MA
1810 Was not used.
1811 Mismatches are errors, not warnings.
1812
402b123d 1813** Fixed incorrect processing of some invalid input.
52d1aeee 1814
402b123d 1815** Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H.
52d1aeee 1816
402b123d 1817** Fixed some typos in the documentation.
52d1aeee 1818
402b123d 1819** %token MY_EOF 0 is supported.
52d1aeee
MA
1820 Before, MY_EOF was silently renumbered as 257.
1821
402b123d 1822** doc/refcard.tex is updated.
52d1aeee 1823
402b123d 1824** %output, %file-prefix, %name-prefix.
52d1aeee
MA
1825 New.
1826
402b123d 1827** --output
e4ab1254 1828 New, aliasing "--output-file".
52d1aeee 1829\f
402b123d 1830* Changes in version 1.30, 2001-10-26:
342b8b6e 1831
e4ab1254
AD
1832** "--defines" and "--graph" have now an optional argument which is the
1833 output file name. "-d" and "-g" do not change; they do not take any
342b8b6e
AD
1834 argument.
1835
e4ab1254 1836** "%source_extension" and "%header_extension" are removed, failed
342b8b6e
AD
1837 experiment.
1838
402b123d 1839** Portability fixes.
f987e9d2 1840\f
402b123d 1841* Changes in version 1.29, 2001-09-07:
342b8b6e 1842
402b123d 1843** The output file does not define const, as this caused problems when used
342b8b6e
AD
1844 with common autoconfiguration schemes. If you still use ancient compilers
1845 that lack const, compile with the equivalent of the C compiler option
e4ab1254 1846 "-Dconst=". Autoconf's AC_C_CONST macro provides one way to do this.
342b8b6e 1847
e4ab1254 1848** Added "-g" and "--graph".
f87a2205 1849
402b123d 1850** The Bison manual is now distributed under the terms of the GNU FDL.
f2b5126e 1851
402b123d 1852** The input and the output files has automatically a similar extension.
234a3be3 1853
402b123d 1854** Russian translation added.
f87a2205 1855
402b123d 1856** NLS support updated; should hopefully be less troublesome.
f87a2205 1857
402b123d 1858** Added the old Bison reference card.
c33638bb 1859
e4ab1254 1860** Added "--locations" and "%locations".
6deb4447 1861
e4ab1254 1862** Added "-S" and "--skeleton".
cd5bd6ac 1863
e4ab1254 1864** "%raw", "-r", "--raw" is disabled.
62ab6972 1865
402b123d 1866** Special characters are escaped when output. This solves the problems
cd5bd6ac
AD
1867 of the #line lines with path names including backslashes.
1868
402b123d 1869** New directives.
e4ab1254
AD
1870 "%yacc", "%fixed_output_files", "%defines", "%no_parser", "%verbose",
1871 "%debug", "%source_extension" and "%header_extension".
f987e9d2 1872
402b123d 1873** @$
f987e9d2 1874 Automatic location tracking.
f87a2205 1875\f
402b123d 1876* Changes in version 1.28, 1999-07-06:
d2e00347 1877
402b123d 1878** Should compile better now with K&R compilers.
d2e00347 1879
402b123d 1880** Added NLS.
d2e00347 1881
402b123d 1882** Fixed a problem with escaping the double quote character.
d2e00347 1883
402b123d 1884** There is now a FAQ.
d2e00347 1885\f
402b123d 1886* Changes in version 1.27:
5c31c3c2 1887
402b123d 1888** The make rule which prevented bison.simple from being created on
5c31c3c2
JT
1889 some systems has been fixed.
1890\f
402b123d 1891* Changes in version 1.26:
4be07551 1892
7e508a2b 1893** Bison now uses Automake.
4be07551 1894
402b123d 1895** New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
4be07551 1896
402b123d 1897** Token numbers now start at 257 as previously documented, not 258.
4be07551 1898
402b123d 1899** Bison honors the TMPDIR environment variable.
4be07551 1900
402b123d 1901** A couple of buffer overruns have been fixed.
f51dbca1 1902
402b123d 1903** Problems when closing files should now be reported.
f51dbca1 1904
402b123d 1905** Generated parsers should now work even on operating systems which do
f51dbca1 1906 not provide alloca().
4be07551 1907\f
402b123d 1908* Changes in version 1.25, 1995-10-16:
df8878c5 1909
402b123d 1910** Errors in the input grammar are not fatal; Bison keeps reading
df8878c5 1911the grammar file, and reports all the errors found in it.
8c44d3ec 1912
402b123d 1913** Tokens can now be specified as multiple-character strings: for
df8878c5 1914example, you could use "<=" for a token which looks like <=, instead
7e508a2b 1915of choosing a name like LESSEQ.
df8878c5 1916
402b123d 1917** The %token_table declaration says to write a table of tokens (names
df8878c5
RS
1918and numbers) into the parser file. The yylex function can use this
1919table to recognize multiple-character string tokens, or for other
1920purposes.
1921
402b123d 1922** The %no_lines declaration says not to generate any #line preprocessor
df8878c5
RS
1923directives in the parser file.
1924
402b123d 1925** The %raw declaration says to use internal Bison token numbers, not
df8878c5
RS
1926Yacc-compatible token numbers, when token names are defined as macros.
1927
402b123d 1928** The --no-parser option produces the parser tables without including
df8878c5
RS
1929the parser engine; a project can now use its own parser engine.
1930The actions go into a separate file called NAME.act, in the form of
1931a switch statement body.
1932\f
402b123d 1933* Changes in version 1.23:
6780ca7a 1934
4d019228
DM
1935The user can define YYPARSE_PARAM as the name of an argument to be
1936passed into yyparse. The argument should have type void *. It should
1937actually point to an object. Grammar actions can access the variable
1938by casting it to the proper pointer type.
6780ca7a 1939
6780ca7a 1940Line numbers in output file corrected.
6780ca7a 1941\f
402b123d 1942* Changes in version 1.22:
6780ca7a
DM
1943
1944--help option added.
6780ca7a 1945\f
402b123d 1946* Changes in version 1.20:
6780ca7a
DM
1947
1948Output file does not redefine const for C++.
9f4503d6 1949
76551463
AD
1950-----
1951
34136e65 1952Copyright (C) 1995-2012 Free Software Foundation, Inc.
76551463 1953
74553c98 1954This file is part of Bison, the GNU Parser Generator.
76551463 1955
f16b0819 1956This program is free software: you can redistribute it and/or modify
76551463 1957it under the terms of the GNU General Public License as published by
f16b0819
PE
1958the Free Software Foundation, either version 3 of the License, or
1959(at your option) any later version.
76551463 1960
f16b0819 1961This program is distributed in the hope that it will be useful,
76551463
AD
1962but WITHOUT ANY WARRANTY; without even the implied warranty of
1963MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
1964GNU General Public License for more details.
1965
1966You should have received a copy of the GNU General Public License
f16b0819 1967along with this program. If not, see <http://www.gnu.org/licenses/>.
7e508a2b
AD
1968
1969 LocalWords: yacc YYBACKUP glr GCC lalr ArrayIndexOutOfBoundsException nullptr
1970 LocalWords: cplusplus liby rpl fprintf mfcalc Wyacc stmt cond expr mk sym lr
1971 LocalWords: IELR ielr Lookahead YYERROR nonassoc LALR's api lookaheads yychar
1972 LocalWords: destructor lookahead YYRHSLOC YYLLOC Rhs ifndef YYFAIL cpp sr rr
1973 LocalWords: preprocessor initializer Wno Wnone Werror FreeBSD prec livelocks
1974 LocalWords: Solaris AIX UX RHEL Tru LHS gcc's Wundef YYENABLE NLS YYLTYPE VCG
1975 LocalWords: yyerror cpp's Wunused yylval yylloc prepend yyparse yylex yypush
1976 LocalWords: Graphviz xml nonterminals midrule destructor's YYSTYPE typedef ly
1977 LocalWords: CHR chr printf stdout namespace preprocessing enum pre include's
1978 LocalWords: YYRECOVERING nonfree destructors YYABORT YYACCEPT params enums de
1979 LocalWords: struct yystype DJGPP lex param Haible NUM alloca YYSTACK NUL goto
1980 LocalWords: YYMAXDEPTH Unescaped UCNs YYLTYPE's yyltype typedefs inline Yaccs
1981 LocalWords: Heriyanto Reenable dprec Hilfinger Eggert MYEOF Folle Menezes EOF
242cc08e 1982 LocalWords: Lackovic define's itemset Groff Gettext malloc NEWS'ed YYDEBUG YY
7e508a2b 1983 LocalWords: namespaces strerror const autoconfiguration Dconst Autoconf's FDL
242cc08e
AD
1984 LocalWords: Automake TMPDIR LESSEQ ylwrap endif yydebug YYTOKEN YYLSP ival hh
1985 LocalWords: extern YYTOKENTYPE TOKENTYPE yytokentype tokentype STYPE lval pdf
dcb366b1
AD
1986 LocalWords: lang yyoutput dvi html ps POSIX lvalp llocp Wother nterm arg init
1987 LocalWords: TOK
7e508a2b
AD
1988
1989Local Variables:
1990mode: outline
e4ab1254 1991fill-column: 76
7e508a2b 1992End: