NEWS

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