NEWS

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