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