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