NEWS

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