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bison/contrib/bison/2.4.1/bison-2.4.1-src/NEWS

+Bison News
+----------
+
+* Changes in version 2.4.1 (2008-12-11):
+
+** In the GLR defines file, unexpanded M4 macros in the yylval and yylloc
+   declarations have been fixed.
+
+** Temporary hack for adding a semicolon to the user action.
+
+  Bison used to prepend a trailing semicolon at the end of the user
+  action for reductions.  This allowed actions such as
+
+    exp: exp "+" exp { $$ = $1 + $3 };
+
+  instead of
+
+    exp: exp "+" exp { $$ = $1 + $3; };
+
+  Some grammars still depend on this `feature'.  Bison 2.4.1 restores
+  the previous behavior in the case of C output (specifically, when
+  neither %language or %skeleton or equivalent command-line options
+  are used) to leave more time for grammars depending on the old
+  behavior to be adjusted.  Future releases of Bison will disable this
+  feature.
+
+** A few minor improvements to the Bison manual.
+
+* Changes in version 2.4 (2008-11-02):
+
+** %language is an experimental feature.
+
+  We first introduced this feature in test release 2.3b as a cleaner
+  alternative to %skeleton.  Since then, we have discussed the possibility of
+  modifying its effect on Bison's output file names.  Thus, in this release,
+  we consider %language to be an experimental feature that will likely evolve
+  in future releases.
+
+** Forward compatibility with GNU M4 has been improved.
+
+** Several bugs in the C++ skeleton and the experimental Java skeleton have been
+  fixed.
+
+* Changes in version 2.3b (2008-05-27):
+
+** The quotes around NAME that used to be required in the following directive
+  are now deprecated:
+
+    %define NAME "VALUE"
+
+** The directive `%pure-parser' is now deprecated in favor of:
+
+    %define api.pure
+
+  which has the same effect except that Bison is more careful to warn about
+  unreasonable usage in the latter case.
+
+** Push Parsing
+
+  Bison can now generate an LALR(1) parser in C with a push interface.  That
+  is, instead of invoking `yyparse', which pulls tokens from `yylex', you can
+  push one token at a time to the parser using `yypush_parse', which will
+  return to the caller after processing each token.  By default, the push
+  interface is disabled.  Either of the following directives will enable it:
+
+    %define api.push_pull "push" // Just push; does not require yylex.
+    %define api.push_pull "both" // Push and pull; requires yylex.
+
+  See the new section `A Push Parser' in the Bison manual for details.
+
+  The current push parsing interface is experimental and may evolve.  More user
+  feedback will help to stabilize it.
+
+** The -g and --graph options now output graphs in Graphviz DOT format,
+  not VCG format.  Like --graph, -g now also takes an optional FILE argument
+  and thus cannot be bundled with other short options.
+
+** Java
+
+  Bison can now generate an LALR(1) parser in Java.  The skeleton is
+  `data/lalr1.java'.  Consider using the new %language directive instead of
+  %skeleton to select it.
+
+  See the new section `Java Parsers' in the Bison manual for details.
+
+  The current Java interface is experimental and may evolve.  More user
+  feedback will help to stabilize it.
+
+** %language
+
+  This new directive specifies the programming language of the generated
+  parser, which can be C (the default), C++, or Java.  Besides the skeleton
+  that Bison uses, the directive affects the names of the generated files if
+  the grammar file's name ends in ".y".
+
+** XML Automaton Report
+
+  Bison can now generate an XML report of the LALR(1) automaton using the new
+  `--xml' option.  The current XML schema is experimental and may evolve.  More
+  user feedback will help to stabilize it.
+
+** The grammar file may now specify the name of the parser header file using
+  %defines.  For example:
+
+    %defines "parser.h"
+
+** When reporting useless rules, useless nonterminals, and unused terminals,
+  Bison now employs the terms "useless in grammar" instead of "useless",
+  "useless in parser" instead of "never reduced", and "unused in grammar"
+  instead of "unused".
+
+** Unreachable State Removal
+
+  Previously, Bison sometimes generated parser tables containing unreachable
+  states.  A state can become unreachable during conflict resolution if Bison
+  disables a shift action leading to it from a predecessor state.  Bison now:
+
+    1. Removes unreachable states.
+
+    2. Does not report any conflicts that appeared in unreachable states.
+       WARNING: As a result, you may need to update %expect and %expect-rr
+       directives in existing grammar files.
+
+    3. For any rule used only in such states, Bison now reports the rule as
+       "useless in parser due to conflicts".
+
+  This feature can be disabled with the following directive:
+
+    %define lr.keep_unreachable_states
+
+  See the %define entry in the `Bison Declaration Summary' in the Bison manual
+  for further discussion.
+
+** Lookahead Set Correction in the `.output' Report
+
+  When instructed to generate a `.output' file including lookahead sets
+  (using `--report=lookahead', for example), Bison now prints each reduction's
+  lookahead set only next to the associated state's one item that (1) is
+  associated with the same rule as the reduction and (2) has its dot at the end
+  of its RHS.  Previously, Bison also erroneously printed the lookahead set
+  next to all of the state's other items associated with the same rule.  This
+  bug affected only the `.output' file and not the generated parser source
+  code.
+
+** --report-file=FILE is a new option to override the default `.output' file
+  name.
+
+** The `=' that used to be required in the following directives is now
+  deprecated:
+
+    %file-prefix "parser"
+    %name-prefix "c_"
+    %output "parser.c"
+
+** An Alternative to `%{...%}' -- `%code QUALIFIER {CODE}'
+
+  Bison 2.3a provided a new set of directives as a more flexible alternative to
+  the traditional Yacc prologue blocks.  Those have now been consolidated into
+  a single %code directive with an optional qualifier field, which identifies
+  the purpose of the code and thus the location(s) where Bison should generate
+  it:
+
+    1. `%code          {CODE}' replaces `%after-header  {CODE}'
+    2. `%code requires {CODE}' replaces `%start-header  {CODE}'
+    3. `%code provides {CODE}' replaces `%end-header    {CODE}'
+    4. `%code top      {CODE}' replaces `%before-header {CODE}'
+
+  See the %code entries in section `Bison Declaration Summary' in the Bison
+  manual for a summary of the new functionality.  See the new section `Prologue
+  Alternatives' for a detailed discussion including the advantages of %code
+  over the traditional Yacc prologues.
+
+  The prologue alternatives are experimental.  More user feedback will help to
+  determine whether they should become permanent features.
+
+** Revised warning: unset or unused mid-rule values
+
+  Since Bison 2.2, Bison has warned about mid-rule values that are set but not
+  used within any of the actions of the parent rule.  For example, Bison warns
+  about unused $2 in:
+
+    exp: '1' { $$ = 1; } '+' exp { $$ = $1 + $4; };
+
+  Now, Bison also warns about mid-rule values that are used but not set.  For
+  example, Bison warns about unset $$ in the mid-rule action in:
+
+    exp: '1' { $1 = 1; } '+' exp { $$ = $2 + $4; };
+
+  However, Bison now disables both of these warnings by default since they
+  sometimes prove to be false alarms in existing grammars employing the Yacc
+  constructs $0 or $-N (where N is some positive integer).
+
+  To enable these warnings, specify the option `--warnings=midrule-values' or
+  `-W', which is a synonym for `--warnings=all'.
+
+** Default %destructor or %printer with `<*>' or `<>'
+
+  Bison now recognizes two separate kinds of default %destructor's and
+  %printer's:
+
+    1. Place `<*>' in a %destructor/%printer symbol list to define a default
+       %destructor/%printer for all grammar symbols for which you have formally
+       declared semantic type tags.
+
+    2. Place `<>' in a %destructor/%printer symbol list to define a default
+       %destructor/%printer for all grammar symbols without declared semantic
+       type tags.
+
+  Bison no longer supports the `%symbol-default' notation from Bison 2.3a.
+  `<*>' and `<>' combined achieve the same effect with one exception: Bison no
+  longer applies any %destructor to a mid-rule value if that mid-rule value is
+  not actually ever referenced using either $$ or $n in a semantic action.
+
+  The default %destructor's and %printer's are experimental.  More user
+  feedback will help to determine whether they should become permanent
+  features.
+
+  See the section `Freeing Discarded Symbols' in the Bison manual for further
+  details.
+
+** %left, %right, and %nonassoc can now declare token numbers.  This is required
+  by POSIX.  However, see the end of section `Operator Precedence' in the Bison
+  manual for a caveat concerning the treatment of literal strings.
+
+** The nonfunctional --no-parser, -n, and %no-parser options have been
+  completely removed from Bison.
+
+* Changes in version 2.3a, 2006-09-13:
+
+** Instead of %union, you can define and use your own union type
+  YYSTYPE if your grammar contains at least one <type> tag.
+  Your YYSTYPE need not be a macro; it can be a typedef.
+  This change is for compatibility with other Yacc implementations,
+  and is required by POSIX.
+
+** Locations columns and lines start at 1.
+  In accordance with the GNU Coding Standards and Emacs.
+
+** You may now declare per-type and default %destructor's and %printer's:
+
+  For example:
+
+    %union { char *string; }
+    %token <string> STRING1
+    %token <string> STRING2
+    %type  <string> string1
+    %type  <string> string2
+    %union { char character; }
+    %token <character> CHR
+    %type  <character> chr
+    %destructor { free ($$); } %symbol-default
+    %destructor { free ($$); printf ("%d", @$.first_line); } STRING1 string1
+    %destructor { } <character>
+
+  guarantees that, when the parser discards any user-defined symbol that has a
+  semantic type tag other than `<character>', it passes its semantic value to
+  `free'.  However, when the parser discards a `STRING1' or a `string1', it
+  also prints its line number to `stdout'.  It performs only the second
+  `%destructor' in this case, so it invokes `free' only once.
+
+  [Although we failed to mention this here in the 2.3a release, the default
+  %destructor's and %printer's were experimental, and they were rewritten in
+  future versions.]
+
+** Except for LALR(1) parsers in C with POSIX Yacc emulation enabled (with `-y',
+  `--yacc', or `%yacc'), Bison no longer generates #define statements for
+  associating token numbers with token names.  Removing the #define statements
+  helps to sanitize the global namespace during preprocessing, but POSIX Yacc
+  requires them.  Bison still generates an enum for token names in all cases.
+
+** Handling of traditional Yacc prologue blocks is now more consistent but
+  potentially incompatible with previous releases of Bison.
+
+  As before, you declare prologue blocks in your grammar file with the
+  `%{ ... %}' syntax.  To generate the pre-prologue, Bison concatenates all
+  prologue blocks that you've declared before the first %union.  To generate
+  the post-prologue, Bison concatenates all prologue blocks that you've
+  declared after the first %union.
+
+  Previous releases of Bison inserted the pre-prologue into both the header
+  file and the code file in all cases except for LALR(1) parsers in C.  In the
+  latter case, Bison inserted it only into the code file.  For parsers in C++,
+  the point of insertion was before any token definitions (which associate
+  token numbers with names).  For parsers in C, the point of insertion was
+  after the token definitions.
+
+  Now, Bison never inserts the pre-prologue into the header file.  In the code
+  file, it always inserts it before the token definitions.
+
+** Bison now provides a more flexible alternative to the traditional Yacc
+  prologue blocks: %before-header, %start-header, %end-header, and
+  %after-header.
+
+  For example, the following declaration order in the grammar file reflects the
+  order in which Bison will output these code blocks.  However, you are free to
+  declare these code blocks in your grammar file in whatever order is most
+  convenient for you:
+
+    %before-header {
+      /* Bison treats this block like a pre-prologue block: it inserts it into
+       * the code file before the contents of the header file.  It does *not*
+       * insert it into the header file.  This is a good place to put
+       * #include's that you want at the top of your code file.  A common
+       * example is `#include "system.h"'.  */
+    }
+    %start-header {
+      /* Bison inserts this block into both the header file and the code file.
+       * In both files, the point of insertion is before any Bison-generated
+       * token, semantic type, location type, and class definitions.  This is a
+       * good place to define %union dependencies, for example.  */
+    }
+    %union {
+      /* Unlike the traditional Yacc prologue blocks, the output order for the
+       * new %*-header blocks is not affected by their declaration position
+       * relative to any %union in the grammar file.  */
+    }
+    %end-header {
+      /* Bison inserts this block into both the header file and the code file.
+       * In both files, the point of insertion is after the Bison-generated
+       * definitions.  This is a good place to declare or define public
+       * functions or data structures that depend on the Bison-generated
+       * definitions.  */
+    }
+    %after-header {
+      /* Bison treats this block like a post-prologue block: it inserts it into
+       * the code file after the contents of the header file.  It does *not*
+       * insert it into the header file.  This is a good place to declare or
+       * define internal functions or data structures that depend on the
+       * Bison-generated definitions.  */
+    }
+
+  If you have multiple occurrences of any one of the above declarations, Bison
+  will concatenate the contents in declaration order.
+
+  [Although we failed to mention this here in the 2.3a release, the prologue
+  alternatives were experimental, and they were rewritten in future versions.]
+
+** The option `--report=look-ahead' has been changed to `--report=lookahead'.
+  The old spelling still works, but is not documented and may be removed
+  in a future release.
+
+* Changes in version 2.3, 2006-06-05:
+
+** GLR grammars should now use `YYRECOVERING ()' instead of `YYRECOVERING',
+  for compatibility with LALR(1) grammars.
+
+** It is now documented that any definition of YYSTYPE or YYLTYPE should
+  be to a type name that does not contain parentheses or brackets.
+
+* Changes in version 2.2, 2006-05-19:
+
+** The distribution terms for all Bison-generated parsers now permit
+  using the parsers in nonfree programs.  Previously, this permission
+  was granted only for Bison-generated LALR(1) parsers in C.
+
+** %name-prefix changes the namespace name in C++ outputs.
+
+** The C++ parsers export their token_type.
+
+** Bison now allows multiple %union declarations, and concatenates
+  their contents together.
+
+** New warning: unused values
+  Right-hand side symbols whose values are not used are reported,
+  if the symbols have destructors.  For instance:
+
+     exp: exp "?" exp ":" exp { $1 ? $1 : $3; }
+        | exp "+" exp
+        ;
+
+  will trigger a warning about $$ and $5 in the first rule, and $3 in
+  the second ($1 is copied to $$ by the default rule).  This example
+  most likely contains three errors, and could be rewritten as:
+
+     exp: exp "?" exp ":" exp
+            { $$ = $1 ? $3 : $5; free ($1 ? $5 : $3); free ($1); }
+        | exp "+" exp
+            { $$ = $1 ? $1 : $3; if ($1) free ($3); }
+        ;
+
+  However, if the original actions were really intended, memory leaks
+  and all, the warnings can be suppressed by letting Bison believe the
+  values are used, e.g.:
+
+     exp: exp "?" exp ":" exp { $1 ? $1 : $3; (void) ($$, $5); }
+        | exp "+" exp         { $$ = $1; (void) $3; }
+        ;
+
+  If there are mid-rule actions, the warning is issued if no action
+  uses it.  The following triggers no warning: $1 and $3 are used.
+
+     exp: exp { push ($1); } '+' exp { push ($3); sum (); };
+
+  The warning is intended to help catching lost values and memory leaks.
+  If a value is ignored, its associated memory typically is not reclaimed.
+
+** %destructor vs. YYABORT, YYACCEPT, and YYERROR.
+  Destructors are now called when user code invokes YYABORT, YYACCEPT,
+  and YYERROR, for all objects on the stack, other than objects
+  corresponding to the right-hand side of the current rule.
+
+** %expect, %expect-rr
+  Incorrect numbers of expected conflicts are now actual errors,
+  instead of warnings.
+
+** GLR, YACC parsers.
+  The %parse-params are available in the destructors (and the
+  experimental printers) as per the documentation.
+
+** Bison now warns if it finds a stray `$' or `@' in an action.
+
+** %require "VERSION"
+  This specifies that the grammar file depends on features implemented
+  in Bison version VERSION or higher.
+
+** lalr1.cc: The token and value types are now class members.
+  The tokens were defined as free form enums and cpp macros.  YYSTYPE
+  was defined as a free form union.  They are now class members:
+  tokens are enumerations of the `yy::parser::token' struct, and the
+  semantic values have the `yy::parser::semantic_type' type.
+
+  If you do not want or can update to this scheme, the directive
+  `%define "global_tokens_and_yystype" "1"' triggers the global
+  definition of tokens and YYSTYPE.  This change is suitable both
+  for previous releases of Bison, and this one.
+
+  If you wish to update, then make sure older version of Bison will
+  fail using `%require "2.2"'.
+
+** DJGPP support added.
+
+* Changes in version 2.1, 2005-09-16:
+
+** The C++ lalr1.cc skeleton supports %lex-param.
+
+** Bison-generated parsers now support the translation of diagnostics like
+  "syntax error" into languages other than English.  The default
+  language is still English.  For details, please see the new
+  Internationalization section of the Bison manual.  Software
+  distributors should also see the new PACKAGING file.  Thanks to
+  Bruno Haible for this new feature.
+
+** Wording in the Bison-generated parsers has been changed slightly to
+  simplify translation.  In particular, the message "memory exhausted"
+  has replaced "parser stack overflow", as the old message was not
+  always accurate for modern Bison-generated parsers.
+
+** Destructors are now called when the parser aborts, for all symbols left
+  behind on the stack.  Also, the start symbol is now destroyed after a
+  successful parse.  In both cases, the behavior was formerly inconsistent.
+
+** When generating verbose diagnostics, Bison-generated parsers no longer
+  quote the literal strings associated with tokens.  For example, for
+  a syntax error associated with '%token NUM "number"' they might
+  print 'syntax error, unexpected number' instead of 'syntax error,
+  unexpected "number"'.
+
+* Changes in version 2.0, 2004-12-25:
+
+** Possibly-incompatible changes
+
+  - Bison-generated parsers no longer default to using the alloca function
+    (when available) to extend the parser stack, due to widespread
+    problems in unchecked stack-overflow detection.  You can "#define
+    YYSTACK_USE_ALLOCA 1" to require the use of alloca, but please read
+    the manual to determine safe values for YYMAXDEPTH in that case.
+
+  - Error token location.
+    During error recovery, the location of the syntax error is updated
+    to cover the whole sequence covered by the error token: it includes
+    the shifted symbols thrown away during the first part of the error
+    recovery, and the lookahead rejected during the second part.
+
+  - Semicolon changes:
+    . Stray semicolons are no longer allowed at the start of a grammar.
+    . Semicolons are now required after in-grammar declarations.
+
+  - Unescaped newlines are no longer allowed in character constants or
+    string literals.  They were never portable, and GCC 3.4.0 has
+    dropped support for them.  Better diagnostics are now generated if
+    forget a closing quote.
+
+  - NUL bytes are no longer allowed in Bison string literals, unfortunately.
+
+** New features
+
+  - GLR grammars now support locations.
+
+  - New directive: %initial-action.
+    This directive allows the user to run arbitrary code (including
+    initializing @$) from yyparse before parsing starts.
+
+  - A new directive "%expect-rr N" specifies the expected number of
+    reduce/reduce conflicts in GLR parsers.
+
+  - %token numbers can now be hexadecimal integers, e.g., `%token FOO 0x12d'.
+    This is a GNU extension.
+
+  - The option `--report=lookahead' was changed to `--report=look-ahead'.
+    [However, this was changed back after 2.3.]
+
+  - Experimental %destructor support has been added to lalr1.cc.
+
+  - New configure option --disable-yacc, to disable installation of the
+    yacc command and -ly library introduced in 1.875 for POSIX conformance.
+
+** Bug fixes
+
+  - For now, %expect-count violations are now just warnings, not errors.
+    This is for compatibility with Bison 1.75 and earlier (when there are
+    reduce/reduce conflicts) and with Bison 1.30 and earlier (when there
+    are too many or too few shift/reduce conflicts).  However, in future
+    versions of Bison we plan to improve the %expect machinery so that
+    these violations will become errors again.
+
+  - Within Bison itself, numbers (e.g., goto numbers) are no longer
+    arbitrarily limited to 16-bit counts.
+
+  - Semicolons are now allowed before "|" in grammar rules, as POSIX requires.
+
+* Changes in version 1.875, 2003-01-01:
+
+** The documentation license has been upgraded to version 1.2
+  of the GNU Free Documentation License.
+
+** syntax error processing
+
+  - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error
+    locations too.  This fixes bugs in error-location computation.
+
+  - %destructor
+    It is now possible to reclaim the memory associated to symbols
+    discarded during error recovery.  This feature is still experimental.
+
+  - %error-verbose
+    This new directive is preferred over YYERROR_VERBOSE.
+
+  - #defining yyerror to steal internal variables is discouraged.
+    It is not guaranteed to work forever.
+
+** POSIX conformance
+
+  - Semicolons are once again optional at the end of grammar rules.
+    This reverts to the behavior of Bison 1.33 and earlier, and improves
+    compatibility with Yacc.
+
+  - `parse error' -> `syntax error'
+    Bison now uniformly uses the term `syntax error'; formerly, the code
+    and manual sometimes used the term `parse error' instead.  POSIX
+    requires `syntax error' in diagnostics, and it was thought better to
+    be consistent.
+
+  - The documentation now emphasizes that yylex and yyerror must be
+    declared before use.  C99 requires this.
+
+  - Bison now parses C99 lexical constructs like UCNs and
+    backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires.
+
+  - File names are properly escaped in C output.  E.g., foo\bar.y is
+    output as "foo\\bar.y".
+
+  - Yacc command and library now available
+    The Bison distribution now installs a `yacc' command, as POSIX requires.
+    Also, Bison now installs a small library liby.a containing
+    implementations of Yacc-compatible yyerror and main functions.
+    This library is normally not useful, but POSIX requires it.
+
+  - Type clashes now generate warnings, not errors.
+
+  - If the user does not define YYSTYPE as a macro, Bison now declares it
+    using typedef instead of defining it as a macro.
+    For consistency, YYLTYPE is also declared instead of defined.
+
+** Other compatibility issues
+
+  - %union directives can now have a tag before the `{', e.g., the
+    directive `%union foo {...}' now generates the C code
+    `typedef union foo { ... } YYSTYPE;'; this is for Yacc compatibility.
+    The default union tag is `YYSTYPE', for compatibility with Solaris 9 Yacc.
+    For consistency, YYLTYPE's struct tag is now `YYLTYPE' not `yyltype'.
+    This is for compatibility with both Yacc and Bison 1.35.
+
+  - `;' is output before the terminating `}' of an action, for
+    compatibility with Bison 1.35.
+
+  - Bison now uses a Yacc-style format for conflict reports, e.g.,
+    `conflicts: 2 shift/reduce, 1 reduce/reduce'.
+
+  - `yystype' and `yyltype' are now obsolescent macros instead of being
+    typedefs or tags; they are no longer documented and are planned to be
+    withdrawn in a future release.
+
+** GLR parser notes
+
+  - GLR and inline
+    Users of Bison have to decide how they handle the portability of the
+    C keyword `inline'.
+
+  - `parsing stack overflow...' -> `parser stack overflow'
+    GLR parsers now report `parser stack overflow' as per the Bison manual.
+
+** Bison now warns if it detects conflicting outputs to the same file,
+  e.g., it generates a warning for `bison -d -o foo.h foo.y' since
+  that command outputs both code and header to foo.h.
+
+** #line in output files
+  - --no-line works properly.
+
+** Bison can no longer be built by a K&R C compiler; it requires C89 or
+  later to be built.  This change originally took place a few versions
+  ago, but nobody noticed until we recently asked someone to try
+  building Bison with a K&R C compiler.
+
+* Changes in version 1.75, 2002-10-14:
+
+** Bison should now work on 64-bit hosts.
+
+** Indonesian translation thanks to Tedi Heriyanto.
+
+** GLR parsers
+  Fix spurious parse errors.
+
+** Pure parsers
+  Some people redefine yyerror to steal yyparse' private variables.
+  Reenable this trick until an official feature replaces it.
+
+** Type Clashes
+  In agreement with POSIX and with other Yaccs, leaving a default
+  action is valid when $$ is untyped, and $1 typed:
+
+        untyped: ... typed;
+
+  but the converse remains an error:
+
+        typed: ... untyped;
+
+** Values of mid-rule actions
+  The following code:
+
+        foo: { ... } { $$ = $1; } ...
+
+  was incorrectly rejected: $1 is defined in the second mid-rule
+  action, and is equal to the $$ of the first mid-rule action.
+
+* Changes in version 1.50, 2002-10-04:
+
+** GLR parsing
+  The declaration
+     %glr-parser
+  causes Bison to produce a Generalized LR (GLR) parser, capable of handling
+  almost any context-free grammar, ambiguous or not.  The new declarations
+  %dprec and %merge on grammar rules allow parse-time resolution of
+  ambiguities.  Contributed by Paul Hilfinger.
+
+  Unfortunately Bison 1.50 does not work properly on 64-bit hosts
+  like the Alpha, so please stick to 32-bit hosts for now.
+
+** Output Directory
+  When not in Yacc compatibility mode, when the output file was not
+  specified, running `bison foo/bar.y' created `foo/bar.c'.  It
+  now creates `bar.c'.
+
+** Undefined token
+  The undefined token was systematically mapped to 2 which prevented
+  the use of 2 by the user.  This is no longer the case.
+
+** Unknown token numbers
+  If yylex returned an out of range value, yyparse could die.  This is
+  no longer the case.
+
+** Error token
+  According to POSIX, the error token must be 256.
+  Bison extends this requirement by making it a preference: *if* the
+  user specified that one of her tokens is numbered 256, then error
+  will be mapped onto another number.
+
+** Verbose error messages
+  They no longer report `..., expecting error or...' for states where
+  error recovery is possible.
+
+** End token
+  Defaults to `$end' instead of `$'.
+
+** Error recovery now conforms to documentation and to POSIX
+  When a Bison-generated parser encounters a syntax error, it now pops
+  the stack until it finds a state that allows shifting the error
+  token.  Formerly, it popped the stack until it found a state that
+  allowed some non-error action other than a default reduction on the
+  error token.  The new behavior has long been the documented behavior,
+  and has long been required by POSIX.  For more details, please see
+  Paul Eggert, "Reductions during Bison error handling" (2002-05-20)
+  <http://lists.gnu.org/archive/html/bug-bison/2002-05/msg00038.html>.
+
+** Traces
+  Popped tokens and nonterminals are now reported.
+
+** Larger grammars
+  Larger grammars are now supported (larger token numbers, larger grammar
+  size (= sum of the LHS and RHS lengths), larger LALR tables).
+  Formerly, many of these numbers ran afoul of 16-bit limits;
+  now these limits are 32 bits on most hosts.
+
+** Explicit initial rule
+  Bison used to play hacks with the initial rule, which the user does
+  not write.  It is now explicit, and visible in the reports and
+  graphs as rule 0.
+
+** Useless rules
+  Before, Bison reported the useless rules, but, although not used,
+  included them in the parsers.  They are now actually removed.
+
+** Useless rules, useless nonterminals
+  They are now reported, as a warning, with their locations.
+
+** Rules never reduced
+  Rules that can never be reduced because of conflicts are now
+  reported.
+
+** Incorrect `Token not used'
+  On a grammar such as
+
+           %token useless useful
+           %%
+           exp: '0' %prec useful;
+
+  where a token was used to set the precedence of the last rule,
+  bison reported both `useful' and `useless' as useless tokens.
+
+** Revert the C++ namespace changes introduced in 1.31
+  as they caused too many portability hassles.
+
+** Default locations
+  By an accident of design, the default computation of @$ was
+  performed after another default computation was performed: @$ = @1.
+  The latter is now removed: YYLLOC_DEFAULT is fully responsible of
+  the computation of @$.
+
+** Token end-of-file
+  The token end of file may be specified by the user, in which case,
+  the user symbol is used in the reports, the graphs, and the verbose
+  error messages instead of `$end', which remains being the default.
+  For instance
+     %token MYEOF 0
+  or
+     %token MYEOF 0 "end of file"
+
+** Semantic parser
+  This old option, which has been broken for ages, is removed.
+
+** New translations
+  Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
+  Croatian, thanks to Denis Lackovic.
+
+** Incorrect token definitions
+  When given `%token 'a' "A"', Bison used to output `#define 'a' 65'.
+
+** Token definitions as enums
+  Tokens are output both as the traditional #define's, and, provided
+  the compiler supports ANSI C or is a C++ compiler, as enums.
+  This lets debuggers display names instead of integers.
+
+** Reports
+  In addition to --verbose, bison supports --report=THINGS, which
+  produces additional information:
+  - itemset
+    complete the core item sets with their closure
+  - lookahead [changed to `look-ahead' in 1.875e through 2.3, but changed back]
+    explicitly associate lookahead tokens to items
+  - solved
+    describe shift/reduce conflicts solving.
+    Bison used to systematically output this information on top of
+    the report.  Solved conflicts are now attached to their states.
+
+** Type clashes
+  Previous versions don't complain when there is a type clash on
+  the default action if the rule has a mid-rule action, such as in:
+
+      %type <foo> bar
+      %%
+      bar: '0' {} '0';
+
+  This is fixed.
+
+** GNU M4 is now required when using Bison.
+
+* Changes in version 1.35, 2002-03-25:
+
+** C Skeleton
+  Some projects use Bison's C parser with C++ compilers, and define
+  YYSTYPE as a class.  The recent adjustment of C parsers for data
+  alignment and 64 bit architectures made this impossible.
+
+  Because for the time being no real solution for C++ parser
+  generation exists, kludges were implemented in the parser to
+  maintain this use.  In the future, when Bison has C++ parsers, this
+  kludge will be disabled.
+
+  This kludge also addresses some C++ problems when the stack was
+  extended.
+
+* Changes in version 1.34, 2002-03-12:
+
+** File name clashes are detected
+  $ bison foo.y -d -o foo.x
+  fatal error: header and parser would both be named `foo.x'
+
+** A missing `;' at the end of a rule triggers a warning
+  In accordance with POSIX, and in agreement with other
+  Yacc implementations, Bison will mandate this semicolon in the near
+  future.  This eases the implementation of a Bison parser of Bison
+  grammars by making this grammar LALR(1) instead of LR(2).  To
+  facilitate the transition, this release introduces a warning.
+
+** Revert the C++ namespace changes introduced in 1.31, as they caused too
+  many portability hassles.
+
+** DJGPP support added.
+
+** Fix test suite portability problems.
+
+* Changes in version 1.33, 2002-02-07:
+
+** Fix C++ issues
+  Groff could not be compiled for the definition of size_t was lacking
+  under some conditions.
+
+** Catch invalid @n
+  As is done with $n.
+
+* Changes in version 1.32, 2002-01-23:
+
+** Fix Yacc output file names
+
+** Portability fixes
+
+** Italian, Dutch translations
+
+* Changes in version 1.31, 2002-01-14:
+
+** Many Bug Fixes
+
+** GNU Gettext and %expect
+  GNU Gettext asserts 10 s/r conflicts, but there are 7.  Now that
+  Bison dies on incorrect %expectations, we fear there will be
+  too many bug reports for Gettext, so _for the time being_, %expect
+  does not trigger an error when the input file is named `plural.y'.
+
+** Use of alloca in parsers
+  If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use
+  malloc exclusively.  Since 1.29, but was not NEWS'ed.
+
+  alloca is used only when compiled with GCC, to avoid portability
+  problems as on AIX.
+
+** yyparse now returns 2 if memory is exhausted; formerly it dumped core.
+
+** When the generated parser lacks debugging code, YYDEBUG is now 0
+  (as POSIX requires) instead of being undefined.
+
+** User Actions
+  Bison has always permitted actions such as { $$ = $1 }: it adds the
+  ending semicolon.  Now if in Yacc compatibility mode, the semicolon
+  is no longer output: one has to write { $$ = $1; }.
+
+** Better C++ compliance
+  The output parsers try to respect C++ namespaces.
+  [This turned out to be a failed experiment, and it was reverted later.]
+
+** Reduced Grammars
+  Fixed bugs when reporting useless nonterminals.
+
+** 64 bit hosts
+  The parsers work properly on 64 bit hosts.
+
+** Error messages
+  Some calls to strerror resulted in scrambled or missing error messages.
+
+** %expect
+  When the number of shift/reduce conflicts is correct, don't issue
+  any warning.
+
+** The verbose report includes the rule line numbers.
+
+** Rule line numbers are fixed in traces.
+
+** Swedish translation
+
+** Parse errors
+  Verbose parse error messages from the parsers are better looking.
+  Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'(''
+     Now: parse error: unexpected '/', expecting "number" or '-' or '('
+
+** Fixed parser memory leaks.
+  When the generated parser was using malloc to extend its stacks, the
+  previous allocations were not freed.
+
+** Fixed verbose output file.
+  Some newlines were missing.
+  Some conflicts in state descriptions were missing.
+
+** Fixed conflict report.
+  Option -v was needed to get the result.
+
+** %expect
+  Was not used.
+  Mismatches are errors, not warnings.
+
+** Fixed incorrect processing of some invalid input.
+
+** Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H.
+
+** Fixed some typos in the documentation.
+
+** %token MY_EOF 0 is supported.
+  Before, MY_EOF was silently renumbered as 257.
+
+** doc/refcard.tex is updated.
+
+** %output, %file-prefix, %name-prefix.
+  New.
+
+** --output
+  New, aliasing `--output-file'.
+
+* Changes in version 1.30, 2001-10-26:
+
+** `--defines' and `--graph' have now an optional argument which is the
+  output file name. `-d' and `-g' do not change; they do not take any
+  argument.
+
+** `%source_extension' and `%header_extension' are removed, failed
+  experiment.
+
+** Portability fixes.
+
+* Changes in version 1.29, 2001-09-07:
+
+** The output file does not define const, as this caused problems when used
+  with common autoconfiguration schemes.  If you still use ancient compilers
+  that lack const, compile with the equivalent of the C compiler option
+  `-Dconst='.  autoconf's AC_C_CONST macro provides one way to do this.
+
+** Added `-g' and `--graph'.
+
+** The Bison manual is now distributed under the terms of the GNU FDL.
+
+** The input and the output files has automatically a similar extension.
+
+** Russian translation added.
+
+** NLS support updated; should hopefully be less troublesome.
+
+** Added the old Bison reference card.
+
+** Added `--locations' and `%locations'.
+
+** Added `-S' and `--skeleton'.
+
+** `%raw', `-r', `--raw' is disabled.
+
+** Special characters are escaped when output.  This solves the problems
+  of the #line lines with path names including backslashes.
+
+** New directives.
+  `%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose',
+  `%debug', `%source_extension' and `%header_extension'.
+
+** @$
+  Automatic location tracking.
+
+* Changes in version 1.28, 1999-07-06:
+
+** Should compile better now with K&R compilers.
+
+** Added NLS.
+
+** Fixed a problem with escaping the double quote character.
+
+** There is now a FAQ.
+
+* Changes in version 1.27:
+
+** The make rule which prevented bison.simple from being created on
+  some systems has been fixed.
+
+* Changes in version 1.26:
+
+** Bison now uses automake.
+
+** New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
+
+** Token numbers now start at 257 as previously documented, not 258.
+
+** Bison honors the TMPDIR environment variable.
+
+** A couple of buffer overruns have been fixed.
+
+** Problems when closing files should now be reported.
+
+** Generated parsers should now work even on operating systems which do
+  not provide alloca().
+
+* Changes in version 1.25, 1995-10-16:
+
+** Errors in the input grammar are not fatal; Bison keeps reading
+the grammar file, and reports all the errors found in it.
+
+** Tokens can now be specified as multiple-character strings: for
+example, you could use "<=" for a token which looks like <=, instead
+of chosing a name like LESSEQ.
+
+** The %token_table declaration says to write a table of tokens (names
+and numbers) into the parser file.  The yylex function can use this
+table to recognize multiple-character string tokens, or for other
+purposes.
+
+** The %no_lines declaration says not to generate any #line preprocessor
+directives in the parser file.
+
+** The %raw declaration says to use internal Bison token numbers, not
+Yacc-compatible token numbers, when token names are defined as macros.
+
+** The --no-parser option produces the parser tables without including
+the parser engine; a project can now use its own parser engine.
+The actions go into a separate file called NAME.act, in the form of
+a switch statement body.
+
+* Changes in version 1.23:
+
+The user can define YYPARSE_PARAM as the name of an argument to be
+passed into yyparse.  The argument should have type void *.  It should
+actually point to an object.  Grammar actions can access the variable
+by casting it to the proper pointer type.
+
+Line numbers in output file corrected.
+
+* Changes in version 1.22:
+
+--help option added.
+
+* Changes in version 1.20:
+
+Output file does not redefine const for C++.
+
+Local Variables:
+mode: outline
+End:
+
+-----
+
+Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
+2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
+
+This file is part of Bison, the GNU Compiler Compiler.
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.