NEWS

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