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