NEWS

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