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 * Type clashes
 100   Previous versions don't complain when there is a type clash on
 101   the default action if the rule has a mid-rule action, such as in:
 102
 103       %type <foo> bar
 104       %%
 105       bar: '0' {} '0';
 106
 107   This is fixed.
 108 \f
 109 Changes in version 1.35, 2002-03-25:
 110
 111 * C Skeleton
 112   Some projects use Bison's C parser with C++ compilers, and define
 113   YYSTYPE as a class.  The recent adjustment of C parsers for data
 114   alignment and 64 bit architectures made this impossible.
 115
 116   Because for the time being no real solution for C++ parser
 117   generation exists, kludges were implemented in the parser to
 118   maintain this use.  In the future, when Bison has C++ parsers, this
 119   kludge will be disabled.
 120
 121   This kludge also addresses some C++ problems when the stack was
 122   extended.
 123
 124 \f
 125 Changes in version 1.34, 2002-03-12:
 126
 127 * File name clashes are detected
 128   $ bison foo.y -d -o foo.x
 129   fatal error: header and parser would both be named `foo.x'
 130
 131 * A missing `;' at the end of a rule triggers a warning
 132   In accordance with POSIX, and in agreement with other
 133   Yacc implementations, Bison will mandate this semicolon in the near
 134   future.  This eases the implementation of a Bison parser of Bison
 135   grammars by making this grammar LALR(1) instead of LR(2).  To
 136   facilitate the transition, this release introduces a warning.
 137
 138 * Revert the C++ namespace changes introduced in 1.31, as they caused too
 139   many portability hassles.
 140
 141 * DJGPP support added.
 142
 143 * Fix test suite portability problems.
 144 \f
 145 Changes in version 1.33, 2002-02-07:
 146
 147 * Fix C++ issues
 148   Groff could not be compiled for the definition of size_t was lacking
 149   under some conditions.
 150
 151 * Catch invalid @n
 152   As is done with $n.
 153 \f
 154 Changes in version 1.32, 2002-01-23:
 155
 156 * Fix Yacc output file names
 157
 158 * Portability fixes
 159
 160 * Italian, Dutch translations
 161 \f
 162 Changes in version 1.31, 2002-01-14:
 163
 164 * Many Bug Fixes
 165
 166 * GNU Gettext and %expect
 167   GNU Gettext asserts 10 s/r conflicts, but there are 7.  Now that
 168   Bison dies on incorrect %expectations, we fear there will be
 169   too many bug reports for Gettext, so _for the time being_, %expect
 170   does not trigger an error when the input file is named `plural.y'.
 171
 172 * Use of alloca in parsers
 173   If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use
 174   malloc exclusively.  Since 1.29, but was not NEWS'ed.
 175
 176   alloca is used only when compiled with GCC, to avoid portability
 177   problems as on AIX.
 178
 179 * When the generated parser lacks debugging code, YYDEBUG is now 0
 180   (as POSIX requires) instead of being undefined.
 181
 182 * User Actions
 183   Bison has always permitted actions such as { $$ = $1 }: it adds the
 184   ending semicolon.  Now if in Yacc compatibility mode, the semicolon
 185   is no longer output: one has to write { $$ = $1; }.
 186
 187 * Better C++ compliance
 188   The output parsers try to respect C++ namespaces.
 189   [This turned out to be a failed experiment, and it was reverted later.]
 190
 191 * Reduced Grammars
 192   Fixed bugs when reporting useless nonterminals.
 193
 194 * 64 bit hosts
 195   The parsers work properly on 64 bit hosts.
 196
 197 * Error messages
 198   Some calls to strerror resulted in scrambled or missing error messages.
 199
 200 * %expect
 201   When the number of shift/reduce conflicts is correct, don't issue
 202   any warning.
 203
 204 * The verbose report includes the rule line numbers.
 205
 206 * Rule line numbers are fixed in traces.
 207
 208 * Swedish translation
 209
 210 * Parse errors
 211   Verbose parse error messages from the parsers are better looking.
 212   Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'(''
 213      Now: parse error: unexpected '/', expecting "number" or '-' or '('
 214
 215 * Fixed parser memory leaks.
 216   When the generated parser was using malloc to extend its stacks, the
 217   previous allocations were not freed.
 218
 219 * Fixed verbose output file.
 220   Some newlines were missing.
 221   Some conflicts in state descriptions were missing.
 222
 223 * Fixed conflict report.
 224   Option -v was needed to get the result.
 225
 226 * %expect
 227   Was not used.
 228   Mismatches are errors, not warnings.
 229
 230 * Fixed incorrect processing of some invalid input.
 231
 232 * Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H.
 233
 234 * Fixed some typos in the documentation.
 235
 236 * %token MY_EOF 0 is supported.
 237   Before, MY_EOF was silently renumbered as 257.
 238
 239 * doc/refcard.tex is updated.
 240
 241 * %output, %file-prefix, %name-prefix.
 242   New.
 243
 244 * --output
 245   New, aliasing `--output-file'.
 246 \f
 247 Changes in version 1.30, 2001-10-26:
 248
 249 * `--defines' and `--graph' have now an optionnal argument which is the
 250   output file name. `-d' and `-g' do not change, they do not take any
 251   argument.
 252
 253 * `%source_extension' and `%header_extension' are removed, failed
 254   experiment.
 255
 256 * Portability fixes.
 257 \f
 258 Changes in version 1.29, 2001-09-07:
 259
 260 * The output file does not define const, as this caused problems when used
 261   with common autoconfiguration schemes.  If you still use ancient compilers
 262   that lack const, compile with the equivalent of the C compiler option
 263   `-Dconst='.  autoconf's AC_C_CONST macro provides one way to do this.
 264
 265 * Added `-g' and `--graph'.
 266
 267 * The Bison manual is now distributed under the terms of the GNU FDL.
 268
 269 * The input and the output files has automatically a similar extension.
 270
 271 * Russian translation added.
 272
 273 * NLS support updated; should hopefully be less troublesome.
 274
 275 * Added the old Bison reference card.
 276
 277 * Added `--locations' and `%locations'.
 278
 279 * Added `-S' and `--skeleton'.
 280
 281 * `%raw', `-r', `--raw' is disabled.
 282
 283 * Special characters are escaped when output.  This solves the problems
 284   of the #line lines with path names including backslashes.
 285
 286 * New directives.
 287   `%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose',
 288   `%debug', `%source_extension' and `%header_extension'.
 289
 290 * @$
 291   Automatic location tracking.
 292 \f
 293 Changes in version 1.28, 1999-07-06:
 294
 295 * Should compile better now with K&R compilers.
 296
 297 * Added NLS.
 298
 299 * Fixed a problem with escaping the double quote character.
 300
 301 * There is now a FAQ.
 302 \f
 303 Changes in version 1.27:
 304
 305 * The make rule which prevented bison.simple from being created on
 306   some systems has been fixed.
 307 \f
 308 Changes in version 1.26:
 309
 310 * Bison now uses automake.
 311
 312 * New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
 313
 314 * Token numbers now start at 257 as previously documented, not 258.
 315
 316 * Bison honors the TMPDIR environment variable.
 317
 318 * A couple of buffer overruns have been fixed.
 319
 320 * Problems when closing files should now be reported.
 321
 322 * Generated parsers should now work even on operating systems which do
 323   not provide alloca().
 324 \f
 325 Changes in version 1.25, 1995-10-16:
 326
 327 * Errors in the input grammar are not fatal; Bison keeps reading
 328 the grammar file, and reports all the errors found in it.
 329
 330 * Tokens can now be specified as multiple-character strings: for
 331 example, you could use "<=" for a token which looks like <=, instead
 332 of chosing a name like LESSEQ.
 333
 334 * The %token_table declaration says to write a table of tokens (names
 335 and numbers) into the parser file.  The yylex function can use this
 336 table to recognize multiple-character string tokens, or for other
 337 purposes.
 338
 339 * The %no_lines declaration says not to generate any #line preprocessor
 340 directives in the parser file.
 341
 342 * The %raw declaration says to use internal Bison token numbers, not
 343 Yacc-compatible token numbers, when token names are defined as macros.
 344
 345 * The --no-parser option produces the parser tables without including
 346 the parser engine; a project can now use its own parser engine.
 347 The actions go into a separate file called NAME.act, in the form of
 348 a switch statement body.
 349 \f
 350 Changes in version 1.23:
 351
 352 The user can define YYPARSE_PARAM as the name of an argument to be
 353 passed into yyparse.  The argument should have type void *.  It should
 354 actually point to an object.  Grammar actions can access the variable
 355 by casting it to the proper pointer type.
 356
 357 Line numbers in output file corrected.
 358 \f
 359 Changes in version 1.22:
 360
 361 --help option added.
 362 \f
 363 Changes in version 1.20:
 364
 365 Output file does not redefine const for C++.
 366
 367 Local Variables:
 368 mode: outline
 369 End:
 370
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