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