NEWS

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