NEWS

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