NEWS

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