NEWS

   1 Bison News
   2 ----------
   3
   4 Changes in version 2.1a:
   5
   6 * %destructor vs. YYABORT, YYACCEPT, and YYERROR.
   7   Destructors are now called when user code invokes YYABORT, YYACCEPT,
   8   and YYERROR, for all objects on the stack, other than objects
   9   corresponding to the right-hand side of the current rule.
  10
  11 * GLR, C++ LALR(1) parsers.
  12   These parser skeletons are now distributed with the same special
  13   license exception that the C LALR(1) parser skeleton has had since
  14   Bison 1.24.  Hence the FSF imposes no copyright restriction on the
  15   output of Bison when it is generating such parsers.
  16
  17 * %expect, %expect-rr
  18   Incorrect numbers of expected conflicts are now actual errors,
  19   instead of warnings.
  20
  21 * GLR, YACC parsers.
  22   The %parse-params are available in the %destructor's (and the
  23   experimental %printer's) as per the documentation.
  24
  25 * Bison now warns if it finds a stray `$' or `@' in an action.
  26
  27 * %require "VERSION"
  28   To specify that the grammar file depends on features implemented in
  29   Bison version VERSION or higher.
  30
  31 * lalr1.cc: The token and value types are now class members.
  32   The tokens were defined as free form enums and cpp macros.  YYSTYPE
  33   was defined as a free form union.  They are now class members:
  34   tokens are enumerations of the `yy::parser::token' struct, and the
  35   semantic values have the `yy::parser::semantic_type' type.
  36
  37   If you do not want or can update to this scheme, the directive
  38   `%define "global_tokens_and_yystype" "1"' triggers the global
  39   definition of tokens and YYSTYPE.  This change is suitable both
  40   for previous releases of Bison, and this one.
  41
  42   If you wish to update, then make sure older version of Bison will
  43   fail using `%require "2.1a"'.
  44
  45 * DJGPP support added.
  46
  47 Changes in version 2.1, 2005-09-16:
  48
  49 * The C++ lalr1.cc skeleton supports %lex-param.
  50
  51 * Bison-generated parsers now support the translation of diagnostics like
  52   "syntax error" into languages other than English.  The default
  53   language is still English.  For details, please see the new
  54   Internationalization section of the Bison manual.  Software
  55   distributors should also see the new PACKAGING file.  Thanks to
  56   Bruno Haible for this new feature.
  57
  58 * Wording in the Bison-generated parsers has been changed slightly to
  59   simplify translation.  In particular, the message "memory exhausted"
  60   has replaced "parser stack overflow", as the old message was not
  61   always accurate for modern Bison-generated parsers.
  62
  63 * Destructors are now called when the parser aborts, for all symbols left
  64   behind on the stack.  Also, the start symbol is now destroyed after a
  65   successful parse.  In both cases, the behavior was formerly inconsistent.
  66
  67 * When generating verbose diagnostics, Bison-generated parsers no longer
  68   quote the literal strings associated with tokens.  For example, for
  69   a syntax error associated with '%token NUM "number"' they might
  70   print 'syntax error, unexpected number' instead of 'syntax error,
  71   unexpected "number"'.
  72
  73 Changes in version 2.0, 2004-12-25:
  74
  75 * Possibly-incompatible changes
  76
  77   - Bison-generated parsers no longer default to using the alloca function
  78     (when available) to extend the parser stack, due to widespread
  79     problems in unchecked stack-overflow detection.  You can "#define
  80     YYSTACK_USE_ALLOCA 1" to require the use of alloca, but please read
  81     the manual to determine safe values for YYMAXDEPTH in that case.
  82
  83   - Error token location.
  84     During error recovery, the location of the syntax error is updated
  85     to cover the whole sequence covered by the error token: it includes
  86     the shifted symbols thrown away during the first part of the error
  87     recovery, and the lookahead rejected during the second part.
  88
  89   - Semicolon changes:
  90     . Stray semicolons are no longer allowed at the start of a grammar.
  91     . Semicolons are now required after in-grammar declarations.
  92
  93   - Unescaped newlines are no longer allowed in character constants or
  94     string literals.  They were never portable, and GCC 3.4.0 has
  95     dropped support for them.  Better diagnostics are now generated if
  96     forget a closing quote.
  97
  98   - NUL bytes are no longer allowed in Bison string literals, unfortunately.
  99
 100 * New features
 101
 102   - GLR grammars now support locations.
 103
 104   - New directive: %initial-action.
 105     This directive allows the user to run arbitrary code (including
 106     initializing @$) from yyparse before parsing starts.
 107
 108   - A new directive "%expect-rr N" specifies the expected number of
 109     reduce/reduce conflicts in GLR parsers.
 110
 111   - %token numbers can now be hexadecimal integers, e.g., `%token FOO 0x12d'.
 112     This is a GNU extension.
 113
 114   - The option `--report=lookahead' was changed to `--report=look-ahead'.
 115     The old spelling still works, but is not documented and will be
 116     removed.
 117
 118   - Experimental %destructor support has been added to lalr1.cc.
 119
 120   - New configure option --disable-yacc, to disable installation of the
 121     yacc command and -ly library introduced in 1.875 for POSIX conformance.
 122
 123 * Bug fixes
 124
 125   - For now, %expect-count violations are now just warnings, not errors.
 126     This is for compatibility with Bison 1.75 and earlier (when there are
 127     reduce/reduce conflicts) and with Bison 1.30 and earlier (when there
 128     are too many or too few shift/reduce conflicts).  However, in future
 129     versions of Bison we plan to improve the %expect machinery so that
 130     these violations will become errors again.
 131
 132   - Within Bison itself, numbers (e.g., goto numbers) are no longer
 133     arbitrarily limited to 16-bit counts.
 134
 135   - Semicolons are now allowed before "|" in grammar rules, as POSIX requires.
 136 \f
 137 Changes in version 1.875, 2003-01-01:
 138
 139 * The documentation license has been upgraded to version 1.2
 140   of the GNU Free Documentation License.
 141
 142 * syntax error processing
 143
 144   - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error
 145     locations too.  This fixes bugs in error-location computation.
 146
 147   - %destructor
 148     It is now possible to reclaim the memory associated to symbols
 149     discarded during error recovery.  This feature is still experimental.
 150
 151   - %error-verbose
 152     This new directive is preferred over YYERROR_VERBOSE.
 153
 154   - #defining yyerror to steal internal variables is discouraged.
 155     It is not guaranteed to work forever.
 156
 157 * POSIX conformance
 158
 159   - Semicolons are once again optional at the end of grammar rules.
 160     This reverts to the behavior of Bison 1.33 and earlier, and improves
 161     compatibility with Yacc.
 162
 163   - `parse error' -> `syntax error'
 164     Bison now uniformly uses the term `syntax error'; formerly, the code
 165     and manual sometimes used the term `parse error' instead.  POSIX
 166     requires `syntax error' in diagnostics, and it was thought better to
 167     be consistent.
 168
 169   - The documentation now emphasizes that yylex and yyerror must be
 170     declared before use.  C99 requires this.
 171
 172   - Bison now parses C99 lexical constructs like UCNs and
 173     backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires.
 174
 175   - File names are properly escaped in C output.  E.g., foo\bar.y is
 176     output as "foo\\bar.y".
 177
 178   - Yacc command and library now available
 179     The Bison distribution now installs a `yacc' command, as POSIX requires.
 180     Also, Bison now installs a small library liby.a containing
 181     implementations of Yacc-compatible yyerror and main functions.
 182     This library is normally not useful, but POSIX requires it.
 183
 184   - Type clashes now generate warnings, not errors.
 185
 186   - If the user does not define YYSTYPE as a macro, Bison now declares it
 187     using typedef instead of defining it as a macro.
 188     For consistency, YYLTYPE is also declared instead of defined.
 189
 190 * Other compatibility issues
 191
 192   - %union directives can now have a tag before the `{', e.g., the
 193     directive `%union foo {...}' now generates the C code
 194     `typedef union foo { ... } YYSTYPE;'; this is for Yacc compatibility.
 195     The default union tag is `YYSTYPE', for compatibility with Solaris 9 Yacc.
 196     For consistency, YYLTYPE's struct tag is now `YYLTYPE' not `yyltype'.
 197     This is for compatibility with both Yacc and Bison 1.35.
 198
 199   - `;' is output before the terminating `}' of an action, for
 200     compatibility with Bison 1.35.
 201
 202   - Bison now uses a Yacc-style format for conflict reports, e.g.,
 203     `conflicts: 2 shift/reduce, 1 reduce/reduce'.
 204
 205   - `yystype' and `yyltype' are now obsolescent macros instead of being
 206     typedefs or tags; they are no longer documented and are planned to be
 207     withdrawn in a future release.
 208
 209 * GLR parser notes
 210
 211   - GLR and inline
 212     Users of Bison have to decide how they handle the portability of the
 213     C keyword `inline'.
 214
 215   - `parsing stack overflow...' -> `parser stack overflow'
 216     GLR parsers now report `parser stack overflow' as per the Bison manual.
 217
 218 * Bison now warns if it detects conflicting outputs to the same file,
 219   e.g., it generates a warning for `bison -d -o foo.h foo.y' since
 220   that command outputs both code and header to foo.h.
 221
 222 * #line in output files
 223   - --no-line works properly.
 224
 225 * Bison can no longer be built by a K&R C compiler; it requires C89 or
 226   later to be built.  This change originally took place a few versions
 227   ago, but nobody noticed until we recently asked someone to try
 228   building Bison with a K&R C compiler.
 229 \f
 230 Changes in version 1.75, 2002-10-14:
 231
 232 * Bison should now work on 64-bit hosts.
 233
 234 * Indonesian translation thanks to Tedi Heriyanto.
 235
 236 * GLR parsers
 237   Fix spurious parse errors.
 238
 239 * Pure parsers
 240   Some people redefine yyerror to steal yyparse' private variables.
 241   Reenable this trick until an official feature replaces it.
 242
 243 * Type Clashes
 244   In agreement with POSIX and with other Yaccs, leaving a default
 245   action is valid when $$ is untyped, and $1 typed:
 246
 247         untyped: ... typed;
 248
 249   but the converse remains an error:
 250
 251         typed: ... untyped;
 252
 253 * Values of mid-rule actions
 254   The following code:
 255
 256         foo: { ... } { $$ = $1; } ...
 257
 258   was incorrectly rejected: $1 is defined in the second mid-rule
 259   action, and is equal to the $$ of the first mid-rule action.
 260 \f
 261 Changes in version 1.50, 2002-10-04:
 262
 263 * GLR parsing
 264   The declaration
 265      %glr-parser
 266   causes Bison to produce a Generalized LR (GLR) parser, capable of handling
 267   almost any context-free grammar, ambiguous or not.  The new declarations
 268   %dprec and %merge on grammar rules allow parse-time resolution of
 269   ambiguities.  Contributed by Paul Hilfinger.
 270
 271   Unfortunately Bison 1.50 does not work properly on 64-bit hosts
 272   like the Alpha, so please stick to 32-bit hosts for now.
 273
 274 * Output Directory
 275   When not in Yacc compatibility mode, when the output file was not
 276   specified, running `bison foo/bar.y' created `foo/bar.c'.  It
 277   now creates `bar.c'.
 278
 279 * Undefined token
 280   The undefined token was systematically mapped to 2 which prevented
 281   the use of 2 by the user.  This is no longer the case.
 282
 283 * Unknown token numbers
 284   If yylex returned an out of range value, yyparse could die.  This is
 285   no longer the case.
 286
 287 * Error token
 288   According to POSIX, the error token must be 256.
 289   Bison extends this requirement by making it a preference: *if* the
 290   user specified that one of her tokens is numbered 256, then error
 291   will be mapped onto another number.
 292
 293 * Verbose error messages
 294   They no longer report `..., expecting error or...' for states where
 295   error recovery is possible.
 296
 297 * End token
 298   Defaults to `$end' instead of `$'.
 299
 300 * Error recovery now conforms to documentation and to POSIX
 301   When a Bison-generated parser encounters a syntax error, it now pops
 302   the stack until it finds a state that allows shifting the error
 303   token.  Formerly, it popped the stack until it found a state that
 304   allowed some non-error action other than a default reduction on the
 305   error token.  The new behavior has long been the documented behavior,
 306   and has long been required by POSIX.  For more details, please see
 307   Paul Eggert, "Reductions during Bison error handling" (2002-05-20)
 308   <http://lists.gnu.org/archive/html/bug-bison/2002-05/msg00038.html>.
 309
 310 * Traces
 311   Popped tokens and nonterminals are now reported.
 312
 313 * Larger grammars
 314   Larger grammars are now supported (larger token numbers, larger grammar
 315   size (= sum of the LHS and RHS lengths), larger LALR tables).
 316   Formerly, many of these numbers ran afoul of 16-bit limits;
 317   now these limits are 32 bits on most hosts.
 318
 319 * Explicit initial rule
 320   Bison used to play hacks with the initial rule, which the user does
 321   not write.  It is now explicit, and visible in the reports and
 322   graphs as rule 0.
 323
 324 * Useless rules
 325   Before, Bison reported the useless rules, but, although not used,
 326   included them in the parsers.  They are now actually removed.
 327
 328 * Useless rules, useless nonterminals
 329   They are now reported, as a warning, with their locations.
 330
 331 * Rules never reduced
 332   Rules that can never be reduced because of conflicts are now
 333   reported.
 334
 335 * Incorrect `Token not used'
 336   On a grammar such as
 337
 338            %token useless useful
 339            %%
 340            exp: '0' %prec useful;
 341
 342   where a token was used to set the precedence of the last rule,
 343   bison reported both `useful' and `useless' as useless tokens.
 344
 345 * Revert the C++ namespace changes introduced in 1.31
 346   as they caused too many portability hassles.
 347
 348 * Default locations
 349   By an accident of design, the default computation of @$ was
 350   performed after another default computation was performed: @$ = @1.
 351   The latter is now removed: YYLLOC_DEFAULT is fully responsible of
 352   the computation of @$.
 353
 354 * Token end-of-file
 355   The token end of file may be specified by the user, in which case,
 356   the user symbol is used in the reports, the graphs, and the verbose
 357   error messages instead of `$end', which remains being the default.
 358   For instance
 359      %token MYEOF 0
 360   or
 361      %token MYEOF 0 "end of file"
 362
 363 * Semantic parser
 364   This old option, which has been broken for ages, is removed.
 365
 366 * New translations
 367   Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
 368   Croatian, thanks to Denis Lackovic.
 369
 370 * Incorrect token definitions
 371   When given `%token 'a' "A"', Bison used to output `#define 'a' 65'.
 372
 373 * Token definitions as enums
 374   Tokens are output both as the traditional #define's, and, provided
 375   the compiler supports ANSI C or is a C++ compiler, as enums.
 376   This lets debuggers display names instead of integers.
 377
 378 * Reports
 379   In addition to --verbose, bison supports --report=THINGS, which
 380   produces additional information:
 381   - itemset
 382     complete the core item sets with their closure
 383   - lookahead [changed to `look-ahead' in 1.875e and later]
 384     explicitly associate look-ahead tokens to items
 385   - solved
 386     describe shift/reduce conflicts solving.
 387     Bison used to systematically output this information on top of
 388     the report.  Solved conflicts are now attached to their states.
 389
 390 * Type clashes
 391   Previous versions don't complain when there is a type clash on
 392   the default action if the rule has a mid-rule action, such as in:
 393
 394       %type <foo> bar
 395       %%
 396       bar: '0' {} '0';
 397
 398   This is fixed.
 399
 400 * GNU M4 is now required when using Bison.
 401 \f
 402 Changes in version 1.35, 2002-03-25:
 403
 404 * C Skeleton
 405   Some projects use Bison's C parser with C++ compilers, and define
 406   YYSTYPE as a class.  The recent adjustment of C parsers for data
 407   alignment and 64 bit architectures made this impossible.
 408
 409   Because for the time being no real solution for C++ parser
 410   generation exists, kludges were implemented in the parser to
 411   maintain this use.  In the future, when Bison has C++ parsers, this
 412   kludge will be disabled.
 413
 414   This kludge also addresses some C++ problems when the stack was
 415   extended.
 416 \f
 417 Changes in version 1.34, 2002-03-12:
 418
 419 * File name clashes are detected
 420   $ bison foo.y -d -o foo.x
 421   fatal error: header and parser would both be named `foo.x'
 422
 423 * A missing `;' at the end of a rule triggers a warning
 424   In accordance with POSIX, and in agreement with other
 425   Yacc implementations, Bison will mandate this semicolon in the near
 426   future.  This eases the implementation of a Bison parser of Bison
 427   grammars by making this grammar LALR(1) instead of LR(2).  To
 428   facilitate the transition, this release introduces a warning.
 429
 430 * Revert the C++ namespace changes introduced in 1.31, as they caused too
 431   many portability hassles.
 432
 433 * DJGPP support added.
 434
 435 * Fix test suite portability problems.
 436 \f
 437 Changes in version 1.33, 2002-02-07:
 438
 439 * Fix C++ issues
 440   Groff could not be compiled for the definition of size_t was lacking
 441   under some conditions.
 442
 443 * Catch invalid @n
 444   As is done with $n.
 445 \f
 446 Changes in version 1.32, 2002-01-23:
 447
 448 * Fix Yacc output file names
 449
 450 * Portability fixes
 451
 452 * Italian, Dutch translations
 453 \f
 454 Changes in version 1.31, 2002-01-14:
 455
 456 * Many Bug Fixes
 457
 458 * GNU Gettext and %expect
 459   GNU Gettext asserts 10 s/r conflicts, but there are 7.  Now that
 460   Bison dies on incorrect %expectations, we fear there will be
 461   too many bug reports for Gettext, so _for the time being_, %expect
 462   does not trigger an error when the input file is named `plural.y'.
 463
 464 * Use of alloca in parsers
 465   If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use
 466   malloc exclusively.  Since 1.29, but was not NEWS'ed.
 467
 468   alloca is used only when compiled with GCC, to avoid portability
 469   problems as on AIX.
 470
 471 * yyparse now returns 2 if memory is exhausted; formerly it dumped core.
 472
 473 * When the generated parser lacks debugging code, YYDEBUG is now 0
 474   (as POSIX requires) instead of being undefined.
 475
 476 * User Actions
 477   Bison has always permitted actions such as { $$ = $1 }: it adds the
 478   ending semicolon.  Now if in Yacc compatibility mode, the semicolon
 479   is no longer output: one has to write { $$ = $1; }.
 480
 481 * Better C++ compliance
 482   The output parsers try to respect C++ namespaces.
 483   [This turned out to be a failed experiment, and it was reverted later.]
 484
 485 * Reduced Grammars
 486   Fixed bugs when reporting useless nonterminals.
 487
 488 * 64 bit hosts
 489   The parsers work properly on 64 bit hosts.
 490
 491 * Error messages
 492   Some calls to strerror resulted in scrambled or missing error messages.
 493
 494 * %expect
 495   When the number of shift/reduce conflicts is correct, don't issue
 496   any warning.
 497
 498 * The verbose report includes the rule line numbers.
 499
 500 * Rule line numbers are fixed in traces.
 501
 502 * Swedish translation
 503
 504 * Parse errors
 505   Verbose parse error messages from the parsers are better looking.
 506   Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'(''
 507      Now: parse error: unexpected '/', expecting "number" or '-' or '('
 508
 509 * Fixed parser memory leaks.
 510   When the generated parser was using malloc to extend its stacks, the
 511   previous allocations were not freed.
 512
 513 * Fixed verbose output file.
 514   Some newlines were missing.
 515   Some conflicts in state descriptions were missing.
 516
 517 * Fixed conflict report.
 518   Option -v was needed to get the result.
 519
 520 * %expect
 521   Was not used.
 522   Mismatches are errors, not warnings.
 523
 524 * Fixed incorrect processing of some invalid input.
 525
 526 * Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H.
 527
 528 * Fixed some typos in the documentation.
 529
 530 * %token MY_EOF 0 is supported.
 531   Before, MY_EOF was silently renumbered as 257.
 532
 533 * doc/refcard.tex is updated.
 534
 535 * %output, %file-prefix, %name-prefix.
 536   New.
 537
 538 * --output
 539   New, aliasing `--output-file'.
 540 \f
 541 Changes in version 1.30, 2001-10-26:
 542
 543 * `--defines' and `--graph' have now an optional argument which is the
 544   output file name. `-d' and `-g' do not change; they do not take any
 545   argument.
 546
 547 * `%source_extension' and `%header_extension' are removed, failed
 548   experiment.
 549
 550 * Portability fixes.
 551 \f
 552 Changes in version 1.29, 2001-09-07:
 553
 554 * The output file does not define const, as this caused problems when used
 555   with common autoconfiguration schemes.  If you still use ancient compilers
 556   that lack const, compile with the equivalent of the C compiler option
 557   `-Dconst='.  autoconf's AC_C_CONST macro provides one way to do this.
 558
 559 * Added `-g' and `--graph'.
 560
 561 * The Bison manual is now distributed under the terms of the GNU FDL.
 562
 563 * The input and the output files has automatically a similar extension.
 564
 565 * Russian translation added.
 566
 567 * NLS support updated; should hopefully be less troublesome.
 568
 569 * Added the old Bison reference card.
 570
 571 * Added `--locations' and `%locations'.
 572
 573 * Added `-S' and `--skeleton'.
 574
 575 * `%raw', `-r', `--raw' is disabled.
 576
 577 * Special characters are escaped when output.  This solves the problems
 578   of the #line lines with path names including backslashes.
 579
 580 * New directives.
 581   `%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose',
 582   `%debug', `%source_extension' and `%header_extension'.
 583
 584 * @$
 585   Automatic location tracking.
 586 \f
 587 Changes in version 1.28, 1999-07-06:
 588
 589 * Should compile better now with K&R compilers.
 590
 591 * Added NLS.
 592
 593 * Fixed a problem with escaping the double quote character.
 594
 595 * There is now a FAQ.
 596 \f
 597 Changes in version 1.27:
 598
 599 * The make rule which prevented bison.simple from being created on
 600   some systems has been fixed.
 601 \f
 602 Changes in version 1.26:
 603
 604 * Bison now uses automake.
 605
 606 * New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
 607
 608 * Token numbers now start at 257 as previously documented, not 258.
 609
 610 * Bison honors the TMPDIR environment variable.
 611
 612 * A couple of buffer overruns have been fixed.
 613
 614 * Problems when closing files should now be reported.
 615
 616 * Generated parsers should now work even on operating systems which do
 617   not provide alloca().
 618 \f
 619 Changes in version 1.25, 1995-10-16:
 620
 621 * Errors in the input grammar are not fatal; Bison keeps reading
 622 the grammar file, and reports all the errors found in it.
 623
 624 * Tokens can now be specified as multiple-character strings: for
 625 example, you could use "<=" for a token which looks like <=, instead
 626 of chosing a name like LESSEQ.
 627
 628 * The %token_table declaration says to write a table of tokens (names
 629 and numbers) into the parser file.  The yylex function can use this
 630 table to recognize multiple-character string tokens, or for other
 631 purposes.
 632
 633 * The %no_lines declaration says not to generate any #line preprocessor
 634 directives in the parser file.
 635
 636 * The %raw declaration says to use internal Bison token numbers, not
 637 Yacc-compatible token numbers, when token names are defined as macros.
 638
 639 * The --no-parser option produces the parser tables without including
 640 the parser engine; a project can now use its own parser engine.
 641 The actions go into a separate file called NAME.act, in the form of
 642 a switch statement body.
 643 \f
 644 Changes in version 1.23:
 645
 646 The user can define YYPARSE_PARAM as the name of an argument to be
 647 passed into yyparse.  The argument should have type void *.  It should
 648 actually point to an object.  Grammar actions can access the variable
 649 by casting it to the proper pointer type.
 650
 651 Line numbers in output file corrected.
 652 \f
 653 Changes in version 1.22:
 654
 655 --help option added.
 656 \f
 657 Changes in version 1.20:
 658
 659 Output file does not redefine const for C++.
 660
 661 Local Variables:
 662 mode: outline
 663 End:
 664
 665 -----
 666
 667 Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
 668 Free Software Foundation, Inc.
 669
 670 This file is part of Bison, the GNU Compiler Compiler.
 671
 672 Bison is free software; you can redistribute it and/or modify
 673 it under the terms of the GNU General Public License as published by
 674 the Free Software Foundation; either version 2, or (at your option)
 675 any later version.
 676
 677 Bison is distributed in the hope that it will be useful,
 678 but WITHOUT ANY WARRANTY; without even the implied warranty of
 679 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 680 GNU General Public License for more details.
 681
 682 You should have received a copy of the GNU General Public License
 683 along with autoconf; see the file COPYING.  If not, write to
 684 the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 685 Boston, MA 02110-1301, USA.