NEWS

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