NEWS

   1 Bison News
   2 ----------
   3
   4 Changes in version 1.875d:
   5
   6 * NUL bytes are no longer allowed in Bison string literals, unfortunately.
   7
   8 * %token numbers can now be hexadecimal integers, e.g., `%token FOO 0x12d'.
   9   This is a GNU extension.
  10
  11 * Experimental %destructor support has been added to lalr1.cc.
  12
  13 Changes in version 1.875c, 2003-08-25:
  14
  15   (Just bug fixes.)
  16
  17 Changes in version 1.875b, 2003-06-17:
  18
  19 * GLR grammars now support locations.
  20
  21 * Semicolon changes:
  22   - Semicolons are now allowed before "|" in grammar rules, as POSIX requires.
  23   - Stray semicolons are no longer allowed at the start of a grammar.
  24   - Semicolons are now required after in-grammar declarations.
  25
  26 Changes in version 1.875a, 2003-02-01:
  27
  28 * For now, %expect-count violations are now just warnings, not errors.
  29   This is for compatibility with Bison 1.75 and earlier (when there are
  30   reduce/reduce conflicts) and with Bison 1.30 and earlier (when there
  31   are too many or too few shift/reduce conflicts).  However, in future
  32   versions of Bison we plan to improve the %expect machinery so that
  33   these violations will become errors again.
  34
  35 * New configure option --disable-yacc, to disable installation of the
  36   yacc command and -ly library introduced in 1.875 for POSIX conformance.
  37 \f
  38 Changes in version 1.875, 2003-01-01:
  39
  40 * The documentation license has been upgraded to version 1.2
  41   of the GNU Free Documentation License.
  42
  43 * syntax error processing
  44
  45   - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error
  46     locations too.  This fixes bugs in error-location computation.
  47
  48   - %destructor
  49     It is now possible to reclaim the memory associated to symbols
  50     discarded during error recovery.  This feature is still experimental.
  51
  52   - %error-verbose
  53     This new directive is preferred over YYERROR_VERBOSE.
  54
  55   - #defining yyerror to steal internal variables is discouraged.
  56     It is not guaranteed to work forever.
  57
  58 * POSIX conformance
  59
  60   - Semicolons are once again optional at the end of grammar rules.
  61     This reverts to the behavior of Bison 1.33 and earlier, and improves
  62     compatibility with Yacc.
  63
  64   - `parse error' -> `syntax error'
  65     Bison now uniformly uses the term `syntax error'; formerly, the code
  66     and manual sometimes used the term `parse error' instead.  POSIX
  67     requires `syntax error' in diagnostics, and it was thought better to
  68     be consistent.
  69
  70   - The documentation now emphasizes that yylex and yyerror must be
  71     declared before use.  C99 requires this.
  72
  73   - Bison now parses C99 lexical constructs like UCNs and
  74     backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires.
  75
  76   - File names are properly escaped in C output.  E.g., foo\bar.y is
  77     output as "foo\\bar.y".
  78
  79   - Yacc command and library now available
  80     The Bison distribution now installs a `yacc' command, as POSIX requires.
  81     Also, Bison now installs a small library liby.a containing
  82     implementations of Yacc-compatible yyerror and main functions.
  83     This library is normally not useful, but POSIX requires it.
  84
  85   - Type clashes now generate warnings, not errors.
  86
  87   - If the user does not define YYSTYPE as a macro, Bison now declares it
  88     using typedef instead of defining it as a macro.
  89     For consistency, YYLTYPE is also declared instead of defined.
  90
  91 * Other compatibility issues
  92
  93   - %union directives can now have a tag before the `{', e.g., the
  94     directive `%union foo {...}' now generates the C code
  95     `typedef union foo { ... } YYSTYPE;'; this is for Yacc compatibility.
  96     The default union tag is `YYSTYPE', for compatibility with Solaris 9 Yacc.
  97     For consistency, YYLTYPE's struct tag is now `YYLTYPE' not `yyltype'.
  98     This is for compatibility with both Yacc and Bison 1.35.
  99
 100   - `;' is output before the terminating `}' of an action, for
 101     compatibility with Bison 1.35.
 102
 103   - Bison now uses a Yacc-style format for conflict reports, e.g.,
 104     `conflicts: 2 shift/reduce, 1 reduce/reduce'.
 105
 106   - `yystype' and `yyltype' are now obsolescent macros instead of being
 107     typedefs or tags; they are no longer documented and are planned to be
 108     withdrawn in a future release.
 109
 110 * GLR parser notes
 111
 112   - GLR and inline
 113     Users of Bison have to decide how they handle the portability of the
 114     C keyword `inline'.
 115
 116   - `parsing stack overflow...' -> `parser stack overflow'
 117     GLR parsers now report `parser stack overflow' as per the Bison manual.
 118
 119 * Bison now warns if it detects conflicting outputs to the same file,
 120   e.g., it generates a warning for `bison -d -o foo.h foo.y' since
 121   that command outputs both code and header to foo.h.
 122
 123 * #line in output files
 124   - --no-line works properly.
 125
 126 * Bison can no longer be built by a K&R C compiler; it requires C89 or
 127   later to be built.  This change originally took place a few versions
 128   ago, but nobody noticed until we recently asked someone to try
 129   building Bison with a K&R C compiler.
 130 \f
 131 Changes in version 1.75, 2002-10-14:
 132
 133 * Bison should now work on 64-bit hosts.
 134
 135 * Indonesian translation thanks to Tedi Heriyanto.
 136
 137 * GLR parsers
 138   Fix spurious parse errors.
 139
 140 * Pure parsers
 141   Some people redefine yyerror to steal yyparse' private variables.
 142   Reenable this trick until an official feature replaces it.
 143
 144 * Type Clashes
 145   In agreement with POSIX and with other Yaccs, leaving a default
 146   action is valid when $$ is untyped, and $1 typed:
 147
 148         untyped: ... typed;
 149
 150   but the converse remains an error:
 151
 152         typed: ... untyped;
 153
 154 * Values of mid-rule actions
 155   The following code:
 156
 157         foo: { ... } { $$ = $1; } ...
 158
 159   was incorrectly rejected: $1 is defined in the second mid-rule
 160   action, and is equal to the $$ of the first mid-rule action.
 161 \f
 162 Changes in version 1.50, 2002-10-04:
 163
 164 * GLR parsing
 165   The declaration
 166      %glr-parser
 167   causes Bison to produce a Generalized LR (GLR) parser, capable of handling
 168   almost any context-free grammar, ambiguous or not.  The new declarations
 169   %dprec and %merge on grammar rules allow parse-time resolution of
 170   ambiguities.  Contributed by Paul Hilfinger.
 171
 172   Unfortunately Bison 1.50 does not work properly on 64-bit hosts
 173   like the Alpha, so please stick to 32-bit hosts for now.
 174
 175 * Output Directory
 176   When not in Yacc compatibility mode, when the output file was not
 177   specified, running `bison foo/bar.y' created `foo/bar.c'.  It
 178   now creates `bar.c'.
 179
 180 * Undefined token
 181   The undefined token was systematically mapped to 2 which prevented
 182   the use of 2 by the user.  This is no longer the case.
 183
 184 * Unknown token numbers
 185   If yylex returned an out of range value, yyparse could die.  This is
 186   no longer the case.
 187
 188 * Error token
 189   According to POSIX, the error token must be 256.
 190   Bison extends this requirement by making it a preference: *if* the
 191   user specified that one of her tokens is numbered 256, then error
 192   will be mapped onto another number.
 193
 194 * Verbose error messages
 195   They no longer report `..., expecting error or...' for states where
 196   error recovery is possible.
 197
 198 * End token
 199   Defaults to `$end' instead of `$'.
 200
 201 * Error recovery now conforms to documentation and to POSIX
 202   When a Bison-generated parser encounters a syntax error, it now pops
 203   the stack until it finds a state that allows shifting the error
 204   token.  Formerly, it popped the stack until it found a state that
 205   allowed some non-error action other than a default reduction on the
 206   error token.  The new behavior has long been the documented behavior,
 207   and has long been required by POSIX.  For more details, please see
 208   <http://mail.gnu.org/pipermail/bug-bison/2002-May/001452.html>.
 209
 210 * Traces
 211   Popped tokens and nonterminals are now reported.
 212
 213 * Larger grammars
 214   Larger grammars are now supported (larger token numbers, larger grammar
 215   size (= sum of the LHS and RHS lengths), larger LALR tables).
 216   Formerly, many of these numbers ran afoul of 16-bit limits;
 217   now these limits are 32 bits on most hosts.
 218
 219 * Explicit initial rule
 220   Bison used to play hacks with the initial rule, which the user does
 221   not write.  It is now explicit, and visible in the reports and
 222   graphs as rule 0.
 223
 224 * Useless rules
 225   Before, Bison reported the useless rules, but, although not used,
 226   included them in the parsers.  They are now actually removed.
 227
 228 * Useless rules, useless nonterminals
 229   They are now reported, as a warning, with their locations.
 230
 231 * Rules never reduced
 232   Rules that can never be reduced because of conflicts are now
 233   reported.
 234
 235 * Incorrect `Token not used'
 236   On a grammar such as
 237
 238            %token useless useful
 239            %%
 240            exp: '0' %prec useful;
 241
 242   where a token was used to set the precedence of the last rule,
 243   bison reported both `useful' and `useless' as useless tokens.
 244
 245 * Revert the C++ namespace changes introduced in 1.31
 246   as they caused too many portability hassles.
 247
 248 * Default locations
 249   By an accident of design, the default computation of @$ was
 250   performed after another default computation was performed: @$ = @1.
 251   The latter is now removed: YYLLOC_DEFAULT is fully responsible of
 252   the computation of @$.
 253
 254 * Token end-of-file
 255   The token end of file may be specified by the user, in which case,
 256   the user symbol is used in the reports, the graphs, and the verbose
 257   error messages instead of `$end', which remains being the default.
 258   For instance
 259      %token MYEOF 0
 260   or
 261      %token MYEOF 0 "end of file"
 262
 263 * Semantic parser
 264   This old option, which has been broken for ages, is removed.
 265
 266 * New translations
 267   Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
 268   Croatian, thanks to Denis Lackovic.
 269
 270 * Incorrect token definitions
 271   When given `%token 'a' "A"', Bison used to output `#define 'a' 65'.
 272
 273 * Token definitions as enums
 274   Tokens are output both as the traditional #define's, and, provided
 275   the compiler supports ANSI C or is a C++ compiler, as enums.
 276   This lets debuggers display names instead of integers.
 277
 278 * Reports
 279   In addition to --verbose, bison supports --report=THINGS, which
 280   produces additional information:
 281   - itemset
 282     complete the core item sets with their closure
 283   - lookahead
 284     explicitly associate lookaheads to items
 285   - solved
 286     describe shift/reduce conflicts solving.
 287     Bison used to systematically output this information on top of
 288     the report.  Solved conflicts are now attached to their states.
 289
 290 * Type clashes
 291   Previous versions don't complain when there is a type clash on
 292   the default action if the rule has a mid-rule action, such as in:
 293
 294       %type <foo> bar
 295       %%
 296       bar: '0' {} '0';
 297
 298   This is fixed.
 299
 300 * GNU M4 is now required when using Bison.
 301 \f
 302 Changes in version 1.35, 2002-03-25:
 303
 304 * C Skeleton
 305   Some projects use Bison's C parser with C++ compilers, and define
 306   YYSTYPE as a class.  The recent adjustment of C parsers for data
 307   alignment and 64 bit architectures made this impossible.
 308
 309   Because for the time being no real solution for C++ parser
 310   generation exists, kludges were implemented in the parser to
 311   maintain this use.  In the future, when Bison has C++ parsers, this
 312   kludge will be disabled.
 313
 314   This kludge also addresses some C++ problems when the stack was
 315   extended.
 316 \f
 317 Changes in version 1.34, 2002-03-12:
 318
 319 * File name clashes are detected
 320   $ bison foo.y -d -o foo.x
 321   fatal error: header and parser would both be named `foo.x'
 322
 323 * A missing `;' at the end of a rule triggers a warning
 324   In accordance with POSIX, and in agreement with other
 325   Yacc implementations, Bison will mandate this semicolon in the near
 326   future.  This eases the implementation of a Bison parser of Bison
 327   grammars by making this grammar LALR(1) instead of LR(2).  To
 328   facilitate the transition, this release introduces a warning.
 329
 330 * Revert the C++ namespace changes introduced in 1.31, as they caused too
 331   many portability hassles.
 332
 333 * DJGPP support added.
 334
 335 * Fix test suite portability problems.
 336 \f
 337 Changes in version 1.33, 2002-02-07:
 338
 339 * Fix C++ issues
 340   Groff could not be compiled for the definition of size_t was lacking
 341   under some conditions.
 342
 343 * Catch invalid @n
 344   As is done with $n.
 345 \f
 346 Changes in version 1.32, 2002-01-23:
 347
 348 * Fix Yacc output file names
 349
 350 * Portability fixes
 351
 352 * Italian, Dutch translations
 353 \f
 354 Changes in version 1.31, 2002-01-14:
 355
 356 * Many Bug Fixes
 357
 358 * GNU Gettext and %expect
 359   GNU Gettext asserts 10 s/r conflicts, but there are 7.  Now that
 360   Bison dies on incorrect %expectations, we fear there will be
 361   too many bug reports for Gettext, so _for the time being_, %expect
 362   does not trigger an error when the input file is named `plural.y'.
 363
 364 * Use of alloca in parsers
 365   If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use
 366   malloc exclusively.  Since 1.29, but was not NEWS'ed.
 367
 368   alloca is used only when compiled with GCC, to avoid portability
 369   problems as on AIX.
 370
 371 * When the generated parser lacks debugging code, YYDEBUG is now 0
 372   (as POSIX requires) instead of being undefined.
 373
 374 * User Actions
 375   Bison has always permitted actions such as { $$ = $1 }: it adds the
 376   ending semicolon.  Now if in Yacc compatibility mode, the semicolon
 377   is no longer output: one has to write { $$ = $1; }.
 378
 379 * Better C++ compliance
 380   The output parsers try to respect C++ namespaces.
 381   [This turned out to be a failed experiment, and it was reverted later.]
 382
 383 * Reduced Grammars
 384   Fixed bugs when reporting useless nonterminals.
 385
 386 * 64 bit hosts
 387   The parsers work properly on 64 bit hosts.
 388
 389 * Error messages
 390   Some calls to strerror resulted in scrambled or missing error messages.
 391
 392 * %expect
 393   When the number of shift/reduce conflicts is correct, don't issue
 394   any warning.
 395
 396 * The verbose report includes the rule line numbers.
 397
 398 * Rule line numbers are fixed in traces.
 399
 400 * Swedish translation
 401
 402 * Parse errors
 403   Verbose parse error messages from the parsers are better looking.
 404   Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'(''
 405      Now: parse error: unexpected '/', expecting "number" or '-' or '('
 406
 407 * Fixed parser memory leaks.
 408   When the generated parser was using malloc to extend its stacks, the
 409   previous allocations were not freed.
 410
 411 * Fixed verbose output file.
 412   Some newlines were missing.
 413   Some conflicts in state descriptions were missing.
 414
 415 * Fixed conflict report.
 416   Option -v was needed to get the result.
 417
 418 * %expect
 419   Was not used.
 420   Mismatches are errors, not warnings.
 421
 422 * Fixed incorrect processing of some invalid input.
 423
 424 * Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H.
 425
 426 * Fixed some typos in the documentation.
 427
 428 * %token MY_EOF 0 is supported.
 429   Before, MY_EOF was silently renumbered as 257.
 430
 431 * doc/refcard.tex is updated.
 432
 433 * %output, %file-prefix, %name-prefix.
 434   New.
 435
 436 * --output
 437   New, aliasing `--output-file'.
 438 \f
 439 Changes in version 1.30, 2001-10-26:
 440
 441 * `--defines' and `--graph' have now an optional argument which is the
 442   output file name. `-d' and `-g' do not change; they do not take any
 443   argument.
 444
 445 * `%source_extension' and `%header_extension' are removed, failed
 446   experiment.
 447
 448 * Portability fixes.
 449 \f
 450 Changes in version 1.29, 2001-09-07:
 451
 452 * The output file does not define const, as this caused problems when used
 453   with common autoconfiguration schemes.  If you still use ancient compilers
 454   that lack const, compile with the equivalent of the C compiler option
 455   `-Dconst='.  autoconf's AC_C_CONST macro provides one way to do this.
 456
 457 * Added `-g' and `--graph'.
 458
 459 * The Bison manual is now distributed under the terms of the GNU FDL.
 460
 461 * The input and the output files has automatically a similar extension.
 462
 463 * Russian translation added.
 464
 465 * NLS support updated; should hopefully be less troublesome.
 466
 467 * Added the old Bison reference card.
 468
 469 * Added `--locations' and `%locations'.
 470
 471 * Added `-S' and `--skeleton'.
 472
 473 * `%raw', `-r', `--raw' is disabled.
 474
 475 * Special characters are escaped when output.  This solves the problems
 476   of the #line lines with path names including backslashes.
 477
 478 * New directives.
 479   `%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose',
 480   `%debug', `%source_extension' and `%header_extension'.
 481
 482 * @$
 483   Automatic location tracking.
 484 \f
 485 Changes in version 1.28, 1999-07-06:
 486
 487 * Should compile better now with K&R compilers.
 488
 489 * Added NLS.
 490
 491 * Fixed a problem with escaping the double quote character.
 492
 493 * There is now a FAQ.
 494 \f
 495 Changes in version 1.27:
 496
 497 * The make rule which prevented bison.simple from being created on
 498   some systems has been fixed.
 499 \f
 500 Changes in version 1.26:
 501
 502 * Bison now uses automake.
 503
 504 * New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
 505
 506 * Token numbers now start at 257 as previously documented, not 258.
 507
 508 * Bison honors the TMPDIR environment variable.
 509
 510 * A couple of buffer overruns have been fixed.
 511
 512 * Problems when closing files should now be reported.
 513
 514 * Generated parsers should now work even on operating systems which do
 515   not provide alloca().
 516 \f
 517 Changes in version 1.25, 1995-10-16:
 518
 519 * Errors in the input grammar are not fatal; Bison keeps reading
 520 the grammar file, and reports all the errors found in it.
 521
 522 * Tokens can now be specified as multiple-character strings: for
 523 example, you could use "<=" for a token which looks like <=, instead
 524 of chosing a name like LESSEQ.
 525
 526 * The %token_table declaration says to write a table of tokens (names
 527 and numbers) into the parser file.  The yylex function can use this
 528 table to recognize multiple-character string tokens, or for other
 529 purposes.
 530
 531 * The %no_lines declaration says not to generate any #line preprocessor
 532 directives in the parser file.
 533
 534 * The %raw declaration says to use internal Bison token numbers, not
 535 Yacc-compatible token numbers, when token names are defined as macros.
 536
 537 * The --no-parser option produces the parser tables without including
 538 the parser engine; a project can now use its own parser engine.
 539 The actions go into a separate file called NAME.act, in the form of
 540 a switch statement body.
 541 \f
 542 Changes in version 1.23:
 543
 544 The user can define YYPARSE_PARAM as the name of an argument to be
 545 passed into yyparse.  The argument should have type void *.  It should
 546 actually point to an object.  Grammar actions can access the variable
 547 by casting it to the proper pointer type.
 548
 549 Line numbers in output file corrected.
 550 \f
 551 Changes in version 1.22:
 552
 553 --help option added.
 554 \f
 555 Changes in version 1.20:
 556
 557 Output file does not redefine const for C++.
 558
 559 Local Variables:
 560 mode: outline
 561 End:
 562
 563 -----
 564
 565 Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
 566 Free Software Foundation, Inc.
 567
 568 This file is part of Bison, the GNU Compiler Compiler.
 569
 570 Bison is free software; you can redistribute it and/or modify
 571 it under the terms of the GNU General Public License as published by
 572 the Free Software Foundation; either version 2, or (at your option)
 573 any later version.
 574
 575 Bison is distributed in the hope that it will be useful,
 576 but WITHOUT ANY WARRANTY; without even the implied warranty of
 577 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 578 GNU General Public License for more details.
 579
 580 You should have received a copy of the GNU General Public License
 581 along with autoconf; see the file COPYING.  If not, write to
 582 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 583 Boston, MA 02111-1307, USA.