NEWS

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