NEWS

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