NEWS

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