NEWS

   1 Bison News
   2 ----------
   3
   4 Changes in version 2.3a+ (????-??-??):
   5
   6 * The -g and --graph options now output graphs in Graphviz DOT format,
   7   not VCG format.
   8
   9 * An experimental directive %language specifies the language of the
  10   generated parser, which can be C (the default) or C++.  This
  11   directive affects the skeleton used, and the names of the generated
  12   files if the grammar file's name ends in ".y".
  13
  14 * The grammar file may now specify the name of the parser header file using
  15   %defines.  For example:
  16
  17     %defines "parser.h"
  18
  19 * The `=' that used to be required in the following directives is now
  20   deprecated:
  21
  22     %file-prefix "parser"
  23     %name-prefix "c_"
  24     %output "parser.c"
  25
  26 * The quotes around NAME that used to be required in the following directive
  27   are now deprecated:
  28
  29     %define NAME "VALUE"
  30
  31 * Bison 2.3a provided a new set of directives as a more flexible alternative to
  32   the traditional Yacc prologue blocks.  Those have now been consolidated into
  33   a single %code directive with an optional qualifier field, which identifies
  34   the purpose of the code and thus the location(s) where Bison should generate
  35   it:
  36
  37     1. `%code          {CODE}' replaces `%after-header  {CODE}'
  38     2. `%code requires {CODE}' replaces `%start-header  {CODE}'
  39     3. `%code provides {CODE}' replaces `%end-header    {CODE}'
  40     4. `%code top      {CODE}' replaces `%before-header {CODE}'
  41
  42   See the %code entries in `Appendix A Bison Symbols' in the Bison manual for a
  43   summary of the new functionality.  See the new section `Prologue
  44   Alternatives' for a detailed discussion including the advantages of %code
  45   over the traditional Yacc prologues.
  46
  47   The prologue alternatives are experimental.  More user feedback will help to
  48   determine whether they should become permanent features.
  49
  50 * Revised warning: unset or unused mid-rule values
  51
  52   Since Bison 2.2, Bison has warned about mid-rule values that are set but not
  53   used within any of the actions of the parent rule.  For example, Bison warns
  54   about unused $2 in:
  55
  56     exp: '1' { $$ = 1; } '+' exp { $$ = $1 + $4; };
  57
  58   Now, Bison also warns about mid-rule values that are used but not set.  For
  59   example, Bison warns about unset $$ in the mid-rule action in:
  60
  61     exp: '1' { $1 = 1; } '+' exp { $$ = $2 + $4; };
  62
  63   However, Bison now disables both of these warnings by default since they
  64   sometimes prove to be false alarms in existing grammars employing the Yacc
  65   constructs $0 or $-N (where N is some positive integer).
  66
  67   To enable these warnings, specify the flag `--warnings=midrule-values' or
  68   `-W', which is a synonym for `--warnings=all'.
  69
  70 * Bison now recognizes two separate kinds of default %destructor's and
  71   %printer's:
  72
  73     1. Place `<*>' in a %destructor/%printer symbol list to define a default
  74        %destructor/%printer for all grammar symbols for which you have formally
  75        declared semantic type tags.
  76
  77     2. Place `<>' in a %destructor/%printer symbol list to define a default
  78        %destructor/%printer for all grammar symbols without declared semantic
  79        type tags.
  80
  81   Bison no longer supports the `%symbol-default' notation from Bison 2.3a.
  82   `<*>' and `<>' combined achieve the same effect with one exception: Bison no
  83   longer applies any %destructor to a mid-rule value if that mid-rule value is
  84   not actually ever referenced using either $$ or $n in a semantic action.
  85
  86   The default %destructor's and %printer's are experimental.  More user
  87   feedback will help to determine whether they should become permanent
  88   features.
  89
  90   See the section `Freeing Discarded Symbols' in the Bison manual for further
  91   details.
  92
  93 Changes in version 2.3a, 2006-09-13:
  94
  95 * Bison now supports generating Java parsers.  Grammars written for
  96   the Java language should include the `%language "Java"' directive.
  97
  98 * Instead of %union, you can define and use your own union type
  99   YYSTYPE if your grammar contains at least one <type> tag.
 100   Your YYSTYPE need not be a macro; it can be a typedef.
 101   This change is for compatibility with other Yacc implementations,
 102   and is required by POSIX.
 103
 104 * Locations columns and lines start at 1.
 105   In accordance with the GNU Coding Standards and Emacs.
 106
 107 * You may now declare per-type and default %destructor's and %printer's:
 108
 109   For example:
 110
 111     %union { char *string; }
 112     %token <string> STRING1
 113     %token <string> STRING2
 114     %type  <string> string1
 115     %type  <string> string2
 116     %union { char character; }
 117     %token <character> CHR
 118     %type  <character> chr
 119     %destructor { free ($$); } %symbol-default
 120     %destructor { free ($$); printf ("%d", @$.first_line); } STRING1 string1
 121     %destructor { } <character>
 122
 123   guarantees that, when the parser discards any user-defined symbol that has a
 124   semantic type tag other than `<character>', it passes its semantic value to
 125   `free'.  However, when the parser discards a `STRING1' or a `string1', it
 126   also prints its line number to `stdout'.  It performs only the second
 127   `%destructor' in this case, so it invokes `free' only once.
 128
 129   [Although we failed to mention this here in the 2.3a release, the default
 130   %destructor's and %printer's were experimental, and they were rewritten in
 131   future versions.]
 132
 133 * Except for LALR(1) parsers in C with POSIX Yacc emulation enabled (with `-y',
 134   `--yacc', or `%yacc'), Bison no longer generates #define statements for
 135   associating token numbers with token names.  Removing the #define statements
 136   helps to sanitize the global namespace during preprocessing, but POSIX Yacc
 137   requires them.  Bison still generates an enum for token names in all cases.
 138
 139 * Handling of traditional Yacc prologue blocks is now more consistent but
 140   potentially incompatible with previous releases of Bison.
 141
 142   As before, you declare prologue blocks in your grammar file with the
 143   `%{ ... %}' syntax.  To generate the pre-prologue, Bison concatenates all
 144   prologue blocks that you've declared before the first %union.  To generate
 145   the post-prologue, Bison concatenates all prologue blocks that you've
 146   declared after the first %union.
 147
 148   Previous releases of Bison inserted the pre-prologue into both the header
 149   file and the code file in all cases except for LALR(1) parsers in C.  In the
 150   latter case, Bison inserted it only into the code file.  For parsers in C++,
 151   the point of insertion was before any token definitions (which associate
 152   token numbers with names).  For parsers in C, the point of insertion was
 153   after the token definitions.
 154
 155   Now, Bison never inserts the pre-prologue into the header file.  In the code
 156   file, it always inserts it before the token definitions.
 157
 158 * Bison now provides a more flexible alternative to the traditional Yacc
 159   prologue blocks: %before-header, %start-header, %end-header, and
 160   %after-header.
 161
 162   For example, the following declaration order in the grammar file reflects the
 163   order in which Bison will output these code blocks.  However, you are free to
 164   declare these code blocks in your grammar file in whatever order is most
 165   convenient for you:
 166
 167     %before-header {
 168       /* Bison treats this block like a pre-prologue block: it inserts it into
 169        * the code file before the contents of the header file.  It does *not*
 170        * insert it into the header file.  This is a good place to put
 171        * #include's that you want at the top of your code file.  A common
 172        * example is `#include "system.h"'.  */
 173     }
 174     %start-header {
 175       /* Bison inserts this block into both the header file and the code file.
 176        * In both files, the point of insertion is before any Bison-generated
 177        * token, semantic type, location type, and class definitions.  This is a
 178        * good place to define %union dependencies, for example.  */
 179     }
 180     %union {
 181       /* Unlike the traditional Yacc prologue blocks, the output order for the
 182        * new %*-header blocks is not affected by their declaration position
 183        * relative to any %union in the grammar file.  */
 184     }
 185     %end-header {
 186       /* Bison inserts this block into both the header file and the code file.
 187        * In both files, the point of insertion is after the Bison-generated
 188        * definitions.  This is a good place to declare or define public
 189        * functions or data structures that depend on the Bison-generated
 190        * definitions.  */
 191     }
 192     %after-header {
 193       /* Bison treats this block like a post-prologue block: it inserts it into
 194        * the code file after the contents of the header file.  It does *not*
 195        * insert it into the header file.  This is a good place to declare or
 196        * define internal functions or data structures that depend on the
 197        * Bison-generated definitions.  */
 198     }
 199
 200   If you have multiple occurrences of any one of the above declarations, Bison
 201   will concatenate the contents in declaration order.
 202
 203   [Although we failed to mention this here in the 2.3a release, the prologue
 204   alternatives were experimental, and they were rewritten in future versions.]
 205
 206 * The option `--report=look-ahead' has been changed to `--report=lookahead'.
 207   The old spelling still works, but is not documented and may be removed
 208   in a future release.
 209
 210 Changes in version 2.3, 2006-06-05:
 211
 212 * GLR grammars should now use `YYRECOVERING ()' instead of `YYRECOVERING',
 213   for compatibility with LALR(1) grammars.
 214
 215 * It is now documented that any definition of YYSTYPE or YYLTYPE should
 216   be to a type name that does not contain parentheses or brackets.
 217
 218 Changes in version 2.2, 2006-05-19:
 219
 220 * The distribution terms for all Bison-generated parsers now permit
 221   using the parsers in nonfree programs.  Previously, this permission
 222   was granted only for Bison-generated LALR(1) parsers in C.
 223
 224 * %name-prefix changes the namespace name in C++ outputs.
 225
 226 * The C++ parsers export their token_type.
 227
 228 * Bison now allows multiple %union declarations, and concatenates
 229   their contents together.
 230
 231 * New warning: unused values
 232   Right-hand side symbols whose values are not used are reported,
 233   if the symbols have destructors.  For instance:
 234
 235      exp: exp "?" exp ":" exp { $1 ? $1 : $3; }
 236         | exp "+" exp
 237         ;
 238
 239   will trigger a warning about $$ and $5 in the first rule, and $3 in
 240   the second ($1 is copied to $$ by the default rule).  This example
 241   most likely contains three errors, and could be rewritten as:
 242
 243      exp: exp "?" exp ":" exp
 244             { $$ = $1 ? $3 : $5; free ($1 ? $5 : $3); free ($1); }
 245         | exp "+" exp
 246             { $$ = $1 ? $1 : $3; if ($1) free ($3); }
 247         ;
 248
 249   However, if the original actions were really intended, memory leaks
 250   and all, the warnings can be suppressed by letting Bison believe the
 251   values are used, e.g.:
 252
 253      exp: exp "?" exp ":" exp { $1 ? $1 : $3; (void) ($$, $5); }
 254         | exp "+" exp         { $$ = $1; (void) $3; }
 255         ;
 256
 257   If there are mid-rule actions, the warning is issued if no action
 258   uses it.  The following triggers no warning: $1 and $3 are used.
 259
 260      exp: exp { push ($1); } '+' exp { push ($3); sum (); };
 261
 262   The warning is intended to help catching lost values and memory leaks.
 263   If a value is ignored, its associated memory typically is not reclaimed.
 264
 265 * %destructor vs. YYABORT, YYACCEPT, and YYERROR.
 266   Destructors are now called when user code invokes YYABORT, YYACCEPT,
 267   and YYERROR, for all objects on the stack, other than objects
 268   corresponding to the right-hand side of the current rule.
 269
 270 * %expect, %expect-rr
 271   Incorrect numbers of expected conflicts are now actual errors,
 272   instead of warnings.
 273
 274 * GLR, YACC parsers.
 275   The %parse-params are available in the destructors (and the
 276   experimental printers) as per the documentation.
 277
 278 * Bison now warns if it finds a stray `$' or `@' in an action.
 279
 280 * %require "VERSION"
 281   This specifies that the grammar file depends on features implemented
 282   in Bison version VERSION or higher.
 283
 284 * lalr1.cc: The token and value types are now class members.
 285   The tokens were defined as free form enums and cpp macros.  YYSTYPE
 286   was defined as a free form union.  They are now class members:
 287   tokens are enumerations of the `yy::parser::token' struct, and the
 288   semantic values have the `yy::parser::semantic_type' type.
 289
 290   If you do not want or can update to this scheme, the directive
 291   `%define "global_tokens_and_yystype" "1"' triggers the global
 292   definition of tokens and YYSTYPE.  This change is suitable both
 293   for previous releases of Bison, and this one.
 294
 295   If you wish to update, then make sure older version of Bison will
 296   fail using `%require "2.2"'.
 297
 298 * DJGPP support added.
 299 \f
 300 Changes in version 2.1, 2005-09-16:
 301
 302 * The C++ lalr1.cc skeleton supports %lex-param.
 303
 304 * Bison-generated parsers now support the translation of diagnostics like
 305   "syntax error" into languages other than English.  The default
 306   language is still English.  For details, please see the new
 307   Internationalization section of the Bison manual.  Software
 308   distributors should also see the new PACKAGING file.  Thanks to
 309   Bruno Haible for this new feature.
 310
 311 * Wording in the Bison-generated parsers has been changed slightly to
 312   simplify translation.  In particular, the message "memory exhausted"
 313   has replaced "parser stack overflow", as the old message was not
 314   always accurate for modern Bison-generated parsers.
 315
 316 * Destructors are now called when the parser aborts, for all symbols left
 317   behind on the stack.  Also, the start symbol is now destroyed after a
 318   successful parse.  In both cases, the behavior was formerly inconsistent.
 319
 320 * When generating verbose diagnostics, Bison-generated parsers no longer
 321   quote the literal strings associated with tokens.  For example, for
 322   a syntax error associated with '%token NUM "number"' they might
 323   print 'syntax error, unexpected number' instead of 'syntax error,
 324   unexpected "number"'.
 325 \f
 326 Changes in version 2.0, 2004-12-25:
 327
 328 * Possibly-incompatible changes
 329
 330   - Bison-generated parsers no longer default to using the alloca function
 331     (when available) to extend the parser stack, due to widespread
 332     problems in unchecked stack-overflow detection.  You can "#define
 333     YYSTACK_USE_ALLOCA 1" to require the use of alloca, but please read
 334     the manual to determine safe values for YYMAXDEPTH in that case.
 335
 336   - Error token location.
 337     During error recovery, the location of the syntax error is updated
 338     to cover the whole sequence covered by the error token: it includes
 339     the shifted symbols thrown away during the first part of the error
 340     recovery, and the lookahead rejected during the second part.
 341
 342   - Semicolon changes:
 343     . Stray semicolons are no longer allowed at the start of a grammar.
 344     . Semicolons are now required after in-grammar declarations.
 345
 346   - Unescaped newlines are no longer allowed in character constants or
 347     string literals.  They were never portable, and GCC 3.4.0 has
 348     dropped support for them.  Better diagnostics are now generated if
 349     forget a closing quote.
 350
 351   - NUL bytes are no longer allowed in Bison string literals, unfortunately.
 352
 353 * New features
 354
 355   - GLR grammars now support locations.
 356
 357   - New directive: %initial-action.
 358     This directive allows the user to run arbitrary code (including
 359     initializing @$) from yyparse before parsing starts.
 360
 361   - A new directive "%expect-rr N" specifies the expected number of
 362     reduce/reduce conflicts in GLR parsers.
 363
 364   - %token numbers can now be hexadecimal integers, e.g., `%token FOO 0x12d'.
 365     This is a GNU extension.
 366
 367   - The option `--report=lookahead' was changed to `--report=look-ahead'.
 368     [However, this was changed back after 2.3.]
 369
 370   - Experimental %destructor support has been added to lalr1.cc.
 371
 372   - New configure option --disable-yacc, to disable installation of the
 373     yacc command and -ly library introduced in 1.875 for POSIX conformance.
 374
 375 * Bug fixes
 376
 377   - For now, %expect-count violations are now just warnings, not errors.
 378     This is for compatibility with Bison 1.75 and earlier (when there are
 379     reduce/reduce conflicts) and with Bison 1.30 and earlier (when there
 380     are too many or too few shift/reduce conflicts).  However, in future
 381     versions of Bison we plan to improve the %expect machinery so that
 382     these violations will become errors again.
 383
 384   - Within Bison itself, numbers (e.g., goto numbers) are no longer
 385     arbitrarily limited to 16-bit counts.
 386
 387   - Semicolons are now allowed before "|" in grammar rules, as POSIX requires.
 388 \f
 389 Changes in version 1.875, 2003-01-01:
 390
 391 * The documentation license has been upgraded to version 1.2
 392   of the GNU Free Documentation License.
 393
 394 * syntax error processing
 395
 396   - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error
 397     locations too.  This fixes bugs in error-location computation.
 398
 399   - %destructor
 400     It is now possible to reclaim the memory associated to symbols
 401     discarded during error recovery.  This feature is still experimental.
 402
 403   - %error-verbose
 404     This new directive is preferred over YYERROR_VERBOSE.
 405
 406   - #defining yyerror to steal internal variables is discouraged.
 407     It is not guaranteed to work forever.
 408
 409 * POSIX conformance
 410
 411   - Semicolons are once again optional at the end of grammar rules.
 412     This reverts to the behavior of Bison 1.33 and earlier, and improves
 413     compatibility with Yacc.
 414
 415   - `parse error' -> `syntax error'
 416     Bison now uniformly uses the term `syntax error'; formerly, the code
 417     and manual sometimes used the term `parse error' instead.  POSIX
 418     requires `syntax error' in diagnostics, and it was thought better to
 419     be consistent.
 420
 421   - The documentation now emphasizes that yylex and yyerror must be
 422     declared before use.  C99 requires this.
 423
 424   - Bison now parses C99 lexical constructs like UCNs and
 425     backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires.
 426
 427   - File names are properly escaped in C output.  E.g., foo\bar.y is
 428     output as "foo\\bar.y".
 429
 430   - Yacc command and library now available
 431     The Bison distribution now installs a `yacc' command, as POSIX requires.
 432     Also, Bison now installs a small library liby.a containing
 433     implementations of Yacc-compatible yyerror and main functions.
 434     This library is normally not useful, but POSIX requires it.
 435
 436   - Type clashes now generate warnings, not errors.
 437
 438   - If the user does not define YYSTYPE as a macro, Bison now declares it
 439     using typedef instead of defining it as a macro.
 440     For consistency, YYLTYPE is also declared instead of defined.
 441
 442 * Other compatibility issues
 443
 444   - %union directives can now have a tag before the `{', e.g., the
 445     directive `%union foo {...}' now generates the C code
 446     `typedef union foo { ... } YYSTYPE;'; this is for Yacc compatibility.
 447     The default union tag is `YYSTYPE', for compatibility with Solaris 9 Yacc.
 448     For consistency, YYLTYPE's struct tag is now `YYLTYPE' not `yyltype'.
 449     This is for compatibility with both Yacc and Bison 1.35.
 450
 451   - `;' is output before the terminating `}' of an action, for
 452     compatibility with Bison 1.35.
 453
 454   - Bison now uses a Yacc-style format for conflict reports, e.g.,
 455     `conflicts: 2 shift/reduce, 1 reduce/reduce'.
 456
 457   - `yystype' and `yyltype' are now obsolescent macros instead of being
 458     typedefs or tags; they are no longer documented and are planned to be
 459     withdrawn in a future release.
 460
 461 * GLR parser notes
 462
 463   - GLR and inline
 464     Users of Bison have to decide how they handle the portability of the
 465     C keyword `inline'.
 466
 467   - `parsing stack overflow...' -> `parser stack overflow'
 468     GLR parsers now report `parser stack overflow' as per the Bison manual.
 469
 470 * Bison now warns if it detects conflicting outputs to the same file,
 471   e.g., it generates a warning for `bison -d -o foo.h foo.y' since
 472   that command outputs both code and header to foo.h.
 473
 474 * #line in output files
 475   - --no-line works properly.
 476
 477 * Bison can no longer be built by a K&R C compiler; it requires C89 or
 478   later to be built.  This change originally took place a few versions
 479   ago, but nobody noticed until we recently asked someone to try
 480   building Bison with a K&R C compiler.
 481 \f
 482 Changes in version 1.75, 2002-10-14:
 483
 484 * Bison should now work on 64-bit hosts.
 485
 486 * Indonesian translation thanks to Tedi Heriyanto.
 487
 488 * GLR parsers
 489   Fix spurious parse errors.
 490
 491 * Pure parsers
 492   Some people redefine yyerror to steal yyparse' private variables.
 493   Reenable this trick until an official feature replaces it.
 494
 495 * Type Clashes
 496   In agreement with POSIX and with other Yaccs, leaving a default
 497   action is valid when $$ is untyped, and $1 typed:
 498
 499         untyped: ... typed;
 500
 501   but the converse remains an error:
 502
 503         typed: ... untyped;
 504
 505 * Values of mid-rule actions
 506   The following code:
 507
 508         foo: { ... } { $$ = $1; } ...
 509
 510   was incorrectly rejected: $1 is defined in the second mid-rule
 511   action, and is equal to the $$ of the first mid-rule action.
 512 \f
 513 Changes in version 1.50, 2002-10-04:
 514
 515 * GLR parsing
 516   The declaration
 517      %glr-parser
 518   causes Bison to produce a Generalized LR (GLR) parser, capable of handling
 519   almost any context-free grammar, ambiguous or not.  The new declarations
 520   %dprec and %merge on grammar rules allow parse-time resolution of
 521   ambiguities.  Contributed by Paul Hilfinger.
 522
 523   Unfortunately Bison 1.50 does not work properly on 64-bit hosts
 524   like the Alpha, so please stick to 32-bit hosts for now.
 525
 526 * Output Directory
 527   When not in Yacc compatibility mode, when the output file was not
 528   specified, running `bison foo/bar.y' created `foo/bar.c'.  It
 529   now creates `bar.c'.
 530
 531 * Undefined token
 532   The undefined token was systematically mapped to 2 which prevented
 533   the use of 2 by the user.  This is no longer the case.
 534
 535 * Unknown token numbers
 536   If yylex returned an out of range value, yyparse could die.  This is
 537   no longer the case.
 538
 539 * Error token
 540   According to POSIX, the error token must be 256.
 541   Bison extends this requirement by making it a preference: *if* the
 542   user specified that one of her tokens is numbered 256, then error
 543   will be mapped onto another number.
 544
 545 * Verbose error messages
 546   They no longer report `..., expecting error or...' for states where
 547   error recovery is possible.
 548
 549 * End token
 550   Defaults to `$end' instead of `$'.
 551
 552 * Error recovery now conforms to documentation and to POSIX
 553   When a Bison-generated parser encounters a syntax error, it now pops
 554   the stack until it finds a state that allows shifting the error
 555   token.  Formerly, it popped the stack until it found a state that
 556   allowed some non-error action other than a default reduction on the
 557   error token.  The new behavior has long been the documented behavior,
 558   and has long been required by POSIX.  For more details, please see
 559   Paul Eggert, "Reductions during Bison error handling" (2002-05-20)
 560   <http://lists.gnu.org/archive/html/bug-bison/2002-05/msg00038.html>.
 561
 562 * Traces
 563   Popped tokens and nonterminals are now reported.
 564
 565 * Larger grammars
 566   Larger grammars are now supported (larger token numbers, larger grammar
 567   size (= sum of the LHS and RHS lengths), larger LALR tables).
 568   Formerly, many of these numbers ran afoul of 16-bit limits;
 569   now these limits are 32 bits on most hosts.
 570
 571 * Explicit initial rule
 572   Bison used to play hacks with the initial rule, which the user does
 573   not write.  It is now explicit, and visible in the reports and
 574   graphs as rule 0.
 575
 576 * Useless rules
 577   Before, Bison reported the useless rules, but, although not used,
 578   included them in the parsers.  They are now actually removed.
 579
 580 * Useless rules, useless nonterminals
 581   They are now reported, as a warning, with their locations.
 582
 583 * Rules never reduced
 584   Rules that can never be reduced because of conflicts are now
 585   reported.
 586
 587 * Incorrect `Token not used'
 588   On a grammar such as
 589
 590            %token useless useful
 591            %%
 592            exp: '0' %prec useful;
 593
 594   where a token was used to set the precedence of the last rule,
 595   bison reported both `useful' and `useless' as useless tokens.
 596
 597 * Revert the C++ namespace changes introduced in 1.31
 598   as they caused too many portability hassles.
 599
 600 * Default locations
 601   By an accident of design, the default computation of @$ was
 602   performed after another default computation was performed: @$ = @1.
 603   The latter is now removed: YYLLOC_DEFAULT is fully responsible of
 604   the computation of @$.
 605
 606 * Token end-of-file
 607   The token end of file may be specified by the user, in which case,
 608   the user symbol is used in the reports, the graphs, and the verbose
 609   error messages instead of `$end', which remains being the default.
 610   For instance
 611      %token MYEOF 0
 612   or
 613      %token MYEOF 0 "end of file"
 614
 615 * Semantic parser
 616   This old option, which has been broken for ages, is removed.
 617
 618 * New translations
 619   Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
 620   Croatian, thanks to Denis Lackovic.
 621
 622 * Incorrect token definitions
 623   When given `%token 'a' "A"', Bison used to output `#define 'a' 65'.
 624
 625 * Token definitions as enums
 626   Tokens are output both as the traditional #define's, and, provided
 627   the compiler supports ANSI C or is a C++ compiler, as enums.
 628   This lets debuggers display names instead of integers.
 629
 630 * Reports
 631   In addition to --verbose, bison supports --report=THINGS, which
 632   produces additional information:
 633   - itemset
 634     complete the core item sets with their closure
 635   - lookahead [changed to `look-ahead' in 1.875e through 2.3, but changed back]
 636     explicitly associate lookahead tokens to items
 637   - solved
 638     describe shift/reduce conflicts solving.
 639     Bison used to systematically output this information on top of
 640     the report.  Solved conflicts are now attached to their states.
 641
 642 * Type clashes
 643   Previous versions don't complain when there is a type clash on
 644   the default action if the rule has a mid-rule action, such as in:
 645
 646       %type <foo> bar
 647       %%
 648       bar: '0' {} '0';
 649
 650   This is fixed.
 651
 652 * GNU M4 is now required when using Bison.
 653 \f
 654 Changes in version 1.35, 2002-03-25:
 655
 656 * C Skeleton
 657   Some projects use Bison's C parser with C++ compilers, and define
 658   YYSTYPE as a class.  The recent adjustment of C parsers for data
 659   alignment and 64 bit architectures made this impossible.
 660
 661   Because for the time being no real solution for C++ parser
 662   generation exists, kludges were implemented in the parser to
 663   maintain this use.  In the future, when Bison has C++ parsers, this
 664   kludge will be disabled.
 665
 666   This kludge also addresses some C++ problems when the stack was
 667   extended.
 668 \f
 669 Changes in version 1.34, 2002-03-12:
 670
 671 * File name clashes are detected
 672   $ bison foo.y -d -o foo.x
 673   fatal error: header and parser would both be named `foo.x'
 674
 675 * A missing `;' at the end of a rule triggers a warning
 676   In accordance with POSIX, and in agreement with other
 677   Yacc implementations, Bison will mandate this semicolon in the near
 678   future.  This eases the implementation of a Bison parser of Bison
 679   grammars by making this grammar LALR(1) instead of LR(2).  To
 680   facilitate the transition, this release introduces a warning.
 681
 682 * Revert the C++ namespace changes introduced in 1.31, as they caused too
 683   many portability hassles.
 684
 685 * DJGPP support added.
 686
 687 * Fix test suite portability problems.
 688 \f
 689 Changes in version 1.33, 2002-02-07:
 690
 691 * Fix C++ issues
 692   Groff could not be compiled for the definition of size_t was lacking
 693   under some conditions.
 694
 695 * Catch invalid @n
 696   As is done with $n.
 697 \f
 698 Changes in version 1.32, 2002-01-23:
 699
 700 * Fix Yacc output file names
 701
 702 * Portability fixes
 703
 704 * Italian, Dutch translations
 705 \f
 706 Changes in version 1.31, 2002-01-14:
 707
 708 * Many Bug Fixes
 709
 710 * GNU Gettext and %expect
 711   GNU Gettext asserts 10 s/r conflicts, but there are 7.  Now that
 712   Bison dies on incorrect %expectations, we fear there will be
 713   too many bug reports for Gettext, so _for the time being_, %expect
 714   does not trigger an error when the input file is named `plural.y'.
 715
 716 * Use of alloca in parsers
 717   If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use
 718   malloc exclusively.  Since 1.29, but was not NEWS'ed.
 719
 720   alloca is used only when compiled with GCC, to avoid portability
 721   problems as on AIX.
 722
 723 * yyparse now returns 2 if memory is exhausted; formerly it dumped core.
 724
 725 * When the generated parser lacks debugging code, YYDEBUG is now 0
 726   (as POSIX requires) instead of being undefined.
 727
 728 * User Actions
 729   Bison has always permitted actions such as { $$ = $1 }: it adds the
 730   ending semicolon.  Now if in Yacc compatibility mode, the semicolon
 731   is no longer output: one has to write { $$ = $1; }.
 732
 733 * Better C++ compliance
 734   The output parsers try to respect C++ namespaces.
 735   [This turned out to be a failed experiment, and it was reverted later.]
 736
 737 * Reduced Grammars
 738   Fixed bugs when reporting useless nonterminals.
 739
 740 * 64 bit hosts
 741   The parsers work properly on 64 bit hosts.
 742
 743 * Error messages
 744   Some calls to strerror resulted in scrambled or missing error messages.
 745
 746 * %expect
 747   When the number of shift/reduce conflicts is correct, don't issue
 748   any warning.
 749
 750 * The verbose report includes the rule line numbers.
 751
 752 * Rule line numbers are fixed in traces.
 753
 754 * Swedish translation
 755
 756 * Parse errors
 757   Verbose parse error messages from the parsers are better looking.
 758   Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'(''
 759      Now: parse error: unexpected '/', expecting "number" or '-' or '('
 760
 761 * Fixed parser memory leaks.
 762   When the generated parser was using malloc to extend its stacks, the
 763   previous allocations were not freed.
 764
 765 * Fixed verbose output file.
 766   Some newlines were missing.
 767   Some conflicts in state descriptions were missing.
 768
 769 * Fixed conflict report.
 770   Option -v was needed to get the result.
 771
 772 * %expect
 773   Was not used.
 774   Mismatches are errors, not warnings.
 775
 776 * Fixed incorrect processing of some invalid input.
 777
 778 * Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H.
 779
 780 * Fixed some typos in the documentation.
 781
 782 * %token MY_EOF 0 is supported.
 783   Before, MY_EOF was silently renumbered as 257.
 784
 785 * doc/refcard.tex is updated.
 786
 787 * %output, %file-prefix, %name-prefix.
 788   New.
 789
 790 * --output
 791   New, aliasing `--output-file'.
 792 \f
 793 Changes in version 1.30, 2001-10-26:
 794
 795 * `--defines' and `--graph' have now an optional argument which is the
 796   output file name. `-d' and `-g' do not change; they do not take any
 797   argument.
 798
 799 * `%source_extension' and `%header_extension' are removed, failed
 800   experiment.
 801
 802 * Portability fixes.
 803 \f
 804 Changes in version 1.29, 2001-09-07:
 805
 806 * The output file does not define const, as this caused problems when used
 807   with common autoconfiguration schemes.  If you still use ancient compilers
 808   that lack const, compile with the equivalent of the C compiler option
 809   `-Dconst='.  autoconf's AC_C_CONST macro provides one way to do this.
 810
 811 * Added `-g' and `--graph'.
 812
 813 * The Bison manual is now distributed under the terms of the GNU FDL.
 814
 815 * The input and the output files has automatically a similar extension.
 816
 817 * Russian translation added.
 818
 819 * NLS support updated; should hopefully be less troublesome.
 820
 821 * Added the old Bison reference card.
 822
 823 * Added `--locations' and `%locations'.
 824
 825 * Added `-S' and `--skeleton'.
 826
 827 * `%raw', `-r', `--raw' is disabled.
 828
 829 * Special characters are escaped when output.  This solves the problems
 830   of the #line lines with path names including backslashes.
 831
 832 * New directives.
 833   `%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose',
 834   `%debug', `%source_extension' and `%header_extension'.
 835
 836 * @$
 837   Automatic location tracking.
 838 \f
 839 Changes in version 1.28, 1999-07-06:
 840
 841 * Should compile better now with K&R compilers.
 842
 843 * Added NLS.
 844
 845 * Fixed a problem with escaping the double quote character.
 846
 847 * There is now a FAQ.
 848 \f
 849 Changes in version 1.27:
 850
 851 * The make rule which prevented bison.simple from being created on
 852   some systems has been fixed.
 853 \f
 854 Changes in version 1.26:
 855
 856 * Bison now uses automake.
 857
 858 * New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
 859
 860 * Token numbers now start at 257 as previously documented, not 258.
 861
 862 * Bison honors the TMPDIR environment variable.
 863
 864 * A couple of buffer overruns have been fixed.
 865
 866 * Problems when closing files should now be reported.
 867
 868 * Generated parsers should now work even on operating systems which do
 869   not provide alloca().
 870 \f
 871 Changes in version 1.25, 1995-10-16:
 872
 873 * Errors in the input grammar are not fatal; Bison keeps reading
 874 the grammar file, and reports all the errors found in it.
 875
 876 * Tokens can now be specified as multiple-character strings: for
 877 example, you could use "<=" for a token which looks like <=, instead
 878 of chosing a name like LESSEQ.
 879
 880 * The %token_table declaration says to write a table of tokens (names
 881 and numbers) into the parser file.  The yylex function can use this
 882 table to recognize multiple-character string tokens, or for other
 883 purposes.
 884
 885 * The %no_lines declaration says not to generate any #line preprocessor
 886 directives in the parser file.
 887
 888 * The %raw declaration says to use internal Bison token numbers, not
 889 Yacc-compatible token numbers, when token names are defined as macros.
 890
 891 * The --no-parser option produces the parser tables without including
 892 the parser engine; a project can now use its own parser engine.
 893 The actions go into a separate file called NAME.act, in the form of
 894 a switch statement body.
 895 \f
 896 Changes in version 1.23:
 897
 898 The user can define YYPARSE_PARAM as the name of an argument to be
 899 passed into yyparse.  The argument should have type void *.  It should
 900 actually point to an object.  Grammar actions can access the variable
 901 by casting it to the proper pointer type.
 902
 903 Line numbers in output file corrected.
 904 \f
 905 Changes in version 1.22:
 906
 907 --help option added.
 908 \f
 909 Changes in version 1.20:
 910
 911 Output file does not redefine const for C++.
 912
 913 Local Variables:
 914 mode: outline
 915 End:
 916
 917 -----
 918
 919 Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
 920 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
 921
 922 This file is part of Bison, the GNU Compiler Compiler.
 923
 924 Bison is free software; you can redistribute it and/or modify
 925 it under the terms of the GNU General Public License as published by
 926 the Free Software Foundation; either version 2, or (at your option)
 927 any later version.
 928
 929 Bison is distributed in the hope that it will be useful,
 930 but WITHOUT ANY WARRANTY; without even the implied warranty of
 931 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 932 GNU General Public License for more details.
 933
 934 You should have received a copy of the GNU General Public License
 935 along with autoconf; see the file COPYING.  If not, write to
 936 the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 937 Boston, MA 02110-1301, USA.