NEWS

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