NEWS

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