NEWS

   1 Bison News
   2 ----------
   3
   4 Changes in version 1.49c:
   5
   6
   7 Changes in version 1.49b, 2002-08-12:
   8
   9 * GLR parsing
  10   The declaration
  11      %glr-parser
  12   causes Bison to produce a Generalized LR (GLR) parser, capable of handling
  13   almost any context-free grammar, ambiguous or not.  The new declarations
  14   %dprec and %merge on grammar rules allow parse-time resolution of
  15   ambiguities.  Contributed by Paul Hilfinger.
  16
  17 * Output Directory
  18   When not in Yacc compatibility mode, when the output file was not
  19   specified, runnning `bison foo/bar.y' created `foo/bar.c'.  It
  20   now creates `bar.c'.
  21
  22 * Undefined token
  23   The undefined token was systematically mapped to 2 which prevented
  24   the use of 2 from the user.  This is no longer the case.
  25
  26 * Unknown token numbers
  27   If yylex returned a code out of range, yyparse could die.  This is
  28   no longer the case.
  29
  30 * Error token
  31   According to POSIX, the error token should be numbered as 256.
  32   Bison extends this requirement by making it a preference: *if* the
  33   user specified that one of her tokens is numbered 256, then error
  34   will be mapped onto another number.
  35
  36 * Verbose error messages
  37   They no longer report `..., expecting error or...' for state where
  38   error recovery is possible.
  39
  40 * End token
  41   Defaults to `$end' instead of `$'.
  42
  43 * Error recovery now conforms to documentation and to POSIX
  44   When a Bison-generated parser encounters a syntax error, it now pops
  45   the stack until it finds a state that allows shifting the error
  46   token.  Formerly, it popped the stack until it found a state that
  47   allowed some non-error action other than a default reduction on the
  48   error token.  The new behavior has long been the documented behavior,
  49   and has long been required by POSIX.  For more details, please see
  50   <http://mail.gnu.org/pipermail/bug-bison/2002-May/001452.html>.
  51
  52 * Traces
  53   Popped tokens and nonterminals are now reported.
  54
  55 * Larger grammars
  56   Larger grammars are now supported (larger token numbers, larger grammar
  57   size (= sum of the LHS and RHS lengths), larger LALR tables).
  58   Formerly, many of these numbers ran afoul of 16-bit limits;
  59   now these limits are 32 bits on most hosts.
  60
  61 * Explicit initial rule
  62   Bison used to play hacks with the initial rule, which the user does
  63   not write.  It is now explicit, and visible in the reports and
  64   graphs as rule 0.
  65
  66 * Useless rules
  67   Before, Bison reported the useless rules, but, although not used,
  68   included them in the parsers.  They are now actually removed.
  69
  70 * Useless rules, useless nonterminals
  71   They are now reported, as a warning, with their locations.
  72
  73 * Rules never reduced
  74   Rules that can never be reduced because of conflicts are now
  75   reported.
  76
  77 * Incorrect `Token not used'
  78   On a grammar such as
  79
  80            %token useless useful
  81            %%
  82            exp: '0' %prec useful;
  83
  84   where a token was used to set the precedence of the last rule,
  85   bison reported both `useful' and `useless' as useless tokens.
  86
  87 * Revert the C++ namespace changes introduced in 1.31
  88   as they caused too many portability hassles.
  89
  90 * Default locations
  91   By an accident of design, the default computation of @$ was
  92   performed after another default computation was performed: @$ = @1.
  93   The latter is now removed: YYLLOC_DEFAULT is fully responsible of
  94   the computation of @$.
  95
  96 * Token end-of-file
  97   The token end of file may be specified by the user, in which case,
  98   the user symbol is used in the reports, the graphs, and the verbose
  99   error messages instead of `$end', which remains being the default.
 100   For instance
 101      %token YYEOF 0
 102   or
 103      %token YYEOF 0 "end of file"
 104
 105 * Semantic parser
 106   This old option, which has been broken for ages, is removed.
 107
 108 * New translations
 109   Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
 110   Croatian, thanks to Denis Lackovic.
 111
 112 * Incorrect token definitions
 113   When fed with `%token 'a' "A"', Bison used to output `#define 'a' 65'.
 114
 115 * Token definitions as enums
 116   Tokens are output both as the traditional #define's, and, provided
 117   the compiler supports ANSI C or is a C++ compiler, as enums.
 118   This helps debuggers producing symbols instead of values.
 119
 120 * Reports
 121   In addition to --verbose, bison supports --report=THINGS, which
 122   produces additional information:
 123   - itemset
 124     complete the core item sets with their closure
 125   - lookahead
 126     explicitly associate lookaheads to items
 127   - solved
 128     describe shift/reduce conflicts solving.
 129     Bison used to systematically output this information on top of
 130     the report.  Solved conflicts are now attached to their states.
 131
 132 * Type clashes
 133   Previous versions don't complain when there is a type clash on
 134   the default action if the rule has a mid-rule action, such as in:
 135
 136       %type <foo> bar
 137       %%
 138       bar: '0' {} '0';
 139
 140   This is fixed.
 141
 142 * GNU M4 is now required when using Bison.
 143 \f
 144 Changes in version 1.35, 2002-03-25:
 145
 146 * C Skeleton
 147   Some projects use Bison's C parser with C++ compilers, and define
 148   YYSTYPE as a class.  The recent adjustment of C parsers for data
 149   alignment and 64 bit architectures made this impossible.
 150
 151   Because for the time being no real solution for C++ parser
 152   generation exists, kludges were implemented in the parser to
 153   maintain this use.  In the future, when Bison has C++ parsers, this
 154   kludge will be disabled.
 155
 156   This kludge also addresses some C++ problems when the stack was
 157   extended.
 158
 159 \f
 160 Changes in version 1.34, 2002-03-12:
 161
 162 * File name clashes are detected
 163   $ bison foo.y -d -o foo.x
 164   fatal error: header and parser would both be named `foo.x'
 165
 166 * A missing `;' at the end of a rule triggers a warning
 167   In accordance with POSIX, and in agreement with other
 168   Yacc implementations, Bison will mandate this semicolon in the near
 169   future.  This eases the implementation of a Bison parser of Bison
 170   grammars by making this grammar LALR(1) instead of LR(2).  To
 171   facilitate the transition, this release introduces a warning.
 172
 173 * Revert the C++ namespace changes introduced in 1.31, as they caused too
 174   many portability hassles.
 175
 176 * DJGPP support added.
 177
 178 * Fix test suite portability problems.
 179 \f
 180 Changes in version 1.33, 2002-02-07:
 181
 182 * Fix C++ issues
 183   Groff could not be compiled for the definition of size_t was lacking
 184   under some conditions.
 185
 186 * Catch invalid @n
 187   As is done with $n.
 188 \f
 189 Changes in version 1.32, 2002-01-23:
 190
 191 * Fix Yacc output file names
 192
 193 * Portability fixes
 194
 195 * Italian, Dutch translations
 196 \f
 197 Changes in version 1.31, 2002-01-14:
 198
 199 * Many Bug Fixes
 200
 201 * GNU Gettext and %expect
 202   GNU Gettext asserts 10 s/r conflicts, but there are 7.  Now that
 203   Bison dies on incorrect %expectations, we fear there will be
 204   too many bug reports for Gettext, so _for the time being_, %expect
 205   does not trigger an error when the input file is named `plural.y'.
 206
 207 * Use of alloca in parsers
 208   If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use
 209   malloc exclusively.  Since 1.29, but was not NEWS'ed.
 210
 211   alloca is used only when compiled with GCC, to avoid portability
 212   problems as on AIX.
 213
 214 * When the generated parser lacks debugging code, YYDEBUG is now 0
 215   (as POSIX requires) instead of being undefined.
 216
 217 * User Actions
 218   Bison has always permitted actions such as { $$ = $1 }: it adds the
 219   ending semicolon.  Now if in Yacc compatibility mode, the semicolon
 220   is no longer output: one has to write { $$ = $1; }.
 221
 222 * Better C++ compliance
 223   The output parsers try to respect C++ namespaces.
 224   [This turned out to be a failed experiment, and it was reverted later.]
 225
 226 * Reduced Grammars
 227   Fixed bugs when reporting useless nonterminals.
 228
 229 * 64 bit hosts
 230   The parsers work properly on 64 bit hosts.
 231
 232 * Error messages
 233   Some calls to strerror resulted in scrambled or missing error messages.
 234
 235 * %expect
 236   When the number of shift/reduce conflicts is correct, don't issue
 237   any warning.
 238
 239 * The verbose report includes the rule line numbers.
 240
 241 * Rule line numbers are fixed in traces.
 242
 243 * Swedish translation
 244
 245 * Parse errors
 246   Verbose parse error messages from the parsers are better looking.
 247   Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'(''
 248      Now: parse error: unexpected '/', expecting "number" or '-' or '('
 249
 250 * Fixed parser memory leaks.
 251   When the generated parser was using malloc to extend its stacks, the
 252   previous allocations were not freed.
 253
 254 * Fixed verbose output file.
 255   Some newlines were missing.
 256   Some conflicts in state descriptions were missing.
 257
 258 * Fixed conflict report.
 259   Option -v was needed to get the result.
 260
 261 * %expect
 262   Was not used.
 263   Mismatches are errors, not warnings.
 264
 265 * Fixed incorrect processing of some invalid input.
 266
 267 * Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H.
 268
 269 * Fixed some typos in the documentation.
 270
 271 * %token MY_EOF 0 is supported.
 272   Before, MY_EOF was silently renumbered as 257.
 273
 274 * doc/refcard.tex is updated.
 275
 276 * %output, %file-prefix, %name-prefix.
 277   New.
 278
 279 * --output
 280   New, aliasing `--output-file'.
 281 \f
 282 Changes in version 1.30, 2001-10-26:
 283
 284 * `--defines' and `--graph' have now an optionnal argument which is the
 285   output file name. `-d' and `-g' do not change, they do not take any
 286   argument.
 287
 288 * `%source_extension' and `%header_extension' are removed, failed
 289   experiment.
 290
 291 * Portability fixes.
 292 \f
 293 Changes in version 1.29, 2001-09-07:
 294
 295 * The output file does not define const, as this caused problems when used
 296   with common autoconfiguration schemes.  If you still use ancient compilers
 297   that lack const, compile with the equivalent of the C compiler option
 298   `-Dconst='.  autoconf's AC_C_CONST macro provides one way to do this.
 299
 300 * Added `-g' and `--graph'.
 301
 302 * The Bison manual is now distributed under the terms of the GNU FDL.
 303
 304 * The input and the output files has automatically a similar extension.
 305
 306 * Russian translation added.
 307
 308 * NLS support updated; should hopefully be less troublesome.
 309
 310 * Added the old Bison reference card.
 311
 312 * Added `--locations' and `%locations'.
 313
 314 * Added `-S' and `--skeleton'.
 315
 316 * `%raw', `-r', `--raw' is disabled.
 317
 318 * Special characters are escaped when output.  This solves the problems
 319   of the #line lines with path names including backslashes.
 320
 321 * New directives.
 322   `%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose',
 323   `%debug', `%source_extension' and `%header_extension'.
 324
 325 * @$
 326   Automatic location tracking.
 327 \f
 328 Changes in version 1.28, 1999-07-06:
 329
 330 * Should compile better now with K&R compilers.
 331
 332 * Added NLS.
 333
 334 * Fixed a problem with escaping the double quote character.
 335
 336 * There is now a FAQ.
 337 \f
 338 Changes in version 1.27:
 339
 340 * The make rule which prevented bison.simple from being created on
 341   some systems has been fixed.
 342 \f
 343 Changes in version 1.26:
 344
 345 * Bison now uses automake.
 346
 347 * New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
 348
 349 * Token numbers now start at 257 as previously documented, not 258.
 350
 351 * Bison honors the TMPDIR environment variable.
 352
 353 * A couple of buffer overruns have been fixed.
 354
 355 * Problems when closing files should now be reported.
 356
 357 * Generated parsers should now work even on operating systems which do
 358   not provide alloca().
 359 \f
 360 Changes in version 1.25, 1995-10-16:
 361
 362 * Errors in the input grammar are not fatal; Bison keeps reading
 363 the grammar file, and reports all the errors found in it.
 364
 365 * Tokens can now be specified as multiple-character strings: for
 366 example, you could use "<=" for a token which looks like <=, instead
 367 of chosing a name like LESSEQ.
 368
 369 * The %token_table declaration says to write a table of tokens (names
 370 and numbers) into the parser file.  The yylex function can use this
 371 table to recognize multiple-character string tokens, or for other
 372 purposes.
 373
 374 * The %no_lines declaration says not to generate any #line preprocessor
 375 directives in the parser file.
 376
 377 * The %raw declaration says to use internal Bison token numbers, not
 378 Yacc-compatible token numbers, when token names are defined as macros.
 379
 380 * The --no-parser option produces the parser tables without including
 381 the parser engine; a project can now use its own parser engine.
 382 The actions go into a separate file called NAME.act, in the form of
 383 a switch statement body.
 384 \f
 385 Changes in version 1.23:
 386
 387 The user can define YYPARSE_PARAM as the name of an argument to be
 388 passed into yyparse.  The argument should have type void *.  It should
 389 actually point to an object.  Grammar actions can access the variable
 390 by casting it to the proper pointer type.
 391
 392 Line numbers in output file corrected.
 393 \f
 394 Changes in version 1.22:
 395
 396 --help option added.
 397 \f
 398 Changes in version 1.20:
 399
 400 Output file does not redefine const for C++.
 401
 402 Local Variables:
 403 mode: outline
 404 End:
 405
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