X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/eb45ef3ba6fff47b9d037da56170f795766c9423..326e5cf81eada2ebd9007fa5fe9903a27a8bd067:/NEWS?ds=sidebyside

diff --git a/NEWS b/NEWS
index a42ec81d..ae87c0af 100644
--- a/NEWS
+++ b/NEWS
@@ -3,14 +3,81 @@ Bison News
 
 * Changes in version ?.? (????-??-??):
 
-** Java skeleton improvements:
+** Additional yylex/yyparse arguments
+
+  The new directive %param declare additional argument to both yylex
+  and yyparse.  The %lex-param, %parse-param, and %param directive
+  support one or more arguments.  Instead of
+
+      %lex-param   {arg1_type *arg1}
+      %lex-param   {arg2_type *arg2}
+      %parse-param {arg1_type *arg1}
+      %parse-param {arg2_type *arg2}
+
+  one may now declare
+
+      %param {arg1_type *arg1} {arg2_type *arg2}
+
+** Java skeleton improvements
 
   The constants for token names were moved to the Lexer interface.
   Also, it is possible to add code to the parser's constructors using
   "%code init" and "%define init_throws".
 
+** Variable api.tokens.prefix
+
+  The variable api.tokens.prefix changes the way tokens are identified in
+  the generated files.  This is especially useful to avoid collisions
+  with identifiers in the target language.  For instance
+
+      %token FILE for ERROR
+      %define api.tokens.prefix "TOK_"
+      %%
+      start: FILE for ERROR;
+
+  will generate the definition of the symbols TOK_FILE, TOK_for, and
+  TOK_ERROR in the generated sources.  In particular, the scanner must
+  use these prefixed token names, although the grammar itself still
+  uses the short names (as in the sample rule given above).
+
+** Variable api.namespace
+
+  The "namespace" variable is renamed "api.namespace".  Backward
+  compatibility is ensured, but upgrading is recommended.
+
+** Variable parse.error
+
+  The variable error controls the verbosity of error messages.  The
+  use of the %error-verbose directive is deprecated in favor of
+  %define parse.error "verbose".
+
 * Changes in version 2.5 (????-??-??):
 
+** Named References Support
+
+  Historically, Yacc and Bison have supported positional references
+  ($n, $$) to allow access to symbol values from inside of semantic
+  actions code.
+
+  Starting from this version, Bison can also accept named references.
+  When no ambiguity is possible, original symbol names may be used
+  as named references:
+
+    if_stmt : 'if' cond_expr 'then' then_stmt ';'
+    { $if_stmt = mk_if_stmt($cond_expr, $then_stmt); }
+
+  In the more common case, explicit names may be declared:
+
+    stmt[res] : 'if' expr[cond] 'then' stmt[then] 'else' stmt[else] ';'
+    { $res = mk_if_stmt($cond, $then, $else); }
+
+  Location information is also accessible using @name syntax.  When
+  accessing symbol names containing dots or dashes, explicit bracketing
+  ($[sym.1]) must be used.
+
+  These features are experimental in this version.  More user feedback
+  will help to stabilize them.
+
 ** IELR(1) and Canonical LR(1) Support
 
   IELR(1) is a minimal LR(1) parser table generation algorithm.  That
@@ -28,31 +95,96 @@ Bison News
   default.  You can specify the type of parser tables in the grammar
   file with these directives:
 
-    %define lr.type "LALR"
-    %define lr.type "IELR"
-    %define lr.type "canonical LR"
+    %define lr.type lalr
+    %define lr.type ielr
+    %define lr.type canonical-lr
 
-  The default rules optimization in the parser tables can also be
-  adjusted using `%define lr.default_rules'.  See the documentation for
-  `%define lr.type' and `%define lr.default_rules' in the section `Bison
-  Declaration Summary' in the Bison manual for the details.
+  The default reduction optimization in the parser tables can also be
+  adjusted using `%define lr.default-reductions'.  See the documentation
+  for `%define lr.type' and `%define lr.default-reductions' in the
+  section `Bison Declaration Summary' in the Bison manual for the
+  details.
 
   These features are experimental.  More user feedback will help to
   stabilize them.
 
-** %define can now be invoked via the command line.
+** Unrecognized %code qualifiers are now an error not a warning.
+
+** %define improvements.
+
+*** Unrecognized variables are now an error not a warning.
+
+*** Multiple invocations for any variable is now an error not a warning.
+
+*** Can now be invoked via the command line.
+
+  Each of these command-line options
 
-  Each of these bison command-line options
+    -D NAME[=VALUE]
+    --define=NAME[=VALUE]
 
-    -D NAME=VALUE
-    --define=NAME=VALUE
+    -F NAME[=VALUE]
+    --force-define=NAME[=VALUE]
 
   is equivalent to this grammar file declaration
 
-    %define NAME "VALUE"
+    %define NAME ["VALUE"]
+
+  except that the manner in which Bison processes multiple definitions
+  for the same NAME differs.  Most importantly, -F and --force-define
+  quietly override %define, but -D and --define do not.  For further
+  details, see the section "Bison Options" in the Bison manual.
+
+*** Variables renamed.
+
+  The following %define variables
+
+    api.push_pull
+    lr.keep_unreachable_states
+
+  have been renamed to
+
+    api.push-pull
+    lr.keep-unreachable-states
+
+  The old names are now deprecated but will be maintained indefinitely
+  for backward compatibility.
+
+*** Values no longer need to be quoted in grammar file.
+
+  If a %define value is an identifier, it no longer needs to be placed
+  within quotations marks.  For example,
+
+    %define api.push-pull "push"
+
+  can be rewritten as
+
+    %define api.push-pull push
+
+** Symbol names.
 
-  for any NAME and VALUE.  Omitting `=VALUE' on the command line is
-  equivalent to omitting `"VALUE"' in the declaration.
+  Consistently with directives (such as %error-verbose) and variables
+  (e.g. push-pull), symbol names may include dashes in any position,
+  similarly to periods and underscores.  This is GNU extension over
+  POSIX Yacc whose use is reported by -Wyacc, and rejected in Yacc
+  mode (--yacc).
+
+** YYFAIL now produces warnings and Java parsers no longer implement it.
+
+  YYFAIL has existed for many years as an undocumented feature of
+  deterministic parsers in C generated by Bison.  More recently, it was
+  a documented feature of Bison's experimental Java parsers.  As
+  promised in Bison 2.4.2's NEWS entry, any appearance of YYFAIL in a
+  semantic action now produces a deprecation warning, and Java parsers
+  no longer implement YYFAIL at all.  For further details, including a
+  discussion of how to suppress C preprocessor warnings about YYFAIL
+  being unused, see the Bison 2.4.2 NEWS entry.
+
+** `%prec IDENTIFIER' requires IDENTIFIER to be defined separately.
+
+  As promised in Bison 2.4.2's NEWS entry, it is now an error if a token
+  that appears after a %prec directive is not defined by %token, %left,
+  %right, or %nonassoc.  This is required by POSIX.
 
 ** Temporary hack for adding a semicolon to the user action.
 
@@ -75,8 +207,121 @@ Bison News
   about a missing semicolon where it did not before.  Future releases of
   Bison will cease to append semicolons entirely.
 
+** Character literals not of length one.
+
+  Previously, Bison quietly converted all character literals to length
+  one.  For example, without warning, Bison interpreted the operators in
+  the following grammar to be the same token:
+
+    exp: exp '++'
+       | exp '+' exp
+       ;
+
+  Bison now warns when a character literal is not of length one.  In
+  some future release, Bison will report an error instead.
+
+** Verbose error messages fixed for nonassociative tokens.
+
+  When %error-verbose is specified, syntax error messages produced by
+  the generated parser include the unexpected token as well as a list of
+  expected tokens.  Previously, this list erroneously included tokens
+  that would actually induce a syntax error because conflicts for them
+  were resolved with %nonassoc.  Such tokens are now properly omitted
+  from the list.
+
+** Destructor calls fixed for lookaheads altered in semantic actions.
+
+  Previously for deterministic parsers in C, if a user semantic action
+  altered yychar, the parser in some cases used the old yychar value to
+  determine which destructor to call for the lookahead upon a syntax
+  error or upon parser return.  This bug has been fixed.
+
 * Changes in version 2.4.2 (????-??-??):
 
+** `%prec IDENTIFIER' requires IDENTIFIER to be defined separately.
+
+  POSIX specifies that an error be reported for any identifier that does
+  not appear on the LHS of a grammar rule and that is not defined by
+  %token, %left, %right, or %nonassoc.  Bison 2.3b and later lost this
+  error report for the case when an identifier appears only after a
+  %prec directive.  It is now restored.  However, for backward
+  compatibility with recent Bison releases, it is only a warning for
+  now.  In Bison 2.5 and later, it will return to being an error.
+
+** Detection of GNU M4 1.4.6 or newer during configure is improved.
+
+** Warnings from gcc's -Wundef option about undefined YYENABLE_NLS,
+   YYLTYPE_IS_TRIVIAL, and __STRICT_ANSI__ in C/C++ parsers are now
+   avoided.
+
+** %code is now a permanent feature.
+
+  A traditional Yacc prologue directive is written in the form:
+
+    %{CODE%}
+
+  To provide a more flexible alternative, Bison 2.3b introduced the
+  %code directive with the following forms for C/C++:
+
+    %code          {CODE}
+    %code requires {CODE}
+    %code provides {CODE}
+    %code top      {CODE}
+
+  These forms are now considered permanent features of Bison.  See the
+  %code entries in the section "Bison Declaration Summary" in the Bison
+  manual for a summary of their functionality.  See the section
+  "Prologue Alternatives" for a detailed discussion including the
+  advantages of %code over the traditional Yacc prologue directive.
+
+  Bison's Java feature as a whole including its current usage of %code
+  is still considered experimental.
+
+** YYFAIL is deprecated and will eventually be removed.
+
+  YYFAIL has existed for many years as an undocumented feature of
+  deterministic parsers in C generated by Bison.  Previously, it was
+  documented for Bison's experimental Java parsers.  YYFAIL is no longer
+  documented for Java parsers and is formally deprecated in both cases.
+  Users are strongly encouraged to migrate to YYERROR, which is
+  specified by POSIX.
+
+  Like YYERROR, you can invoke YYFAIL from a semantic action in order to
+  induce a syntax error.  The most obvious difference from YYERROR is
+  that YYFAIL will automatically invoke yyerror to report the syntax
+  error so that you don't have to.  However, there are several other
+  subtle differences between YYERROR and YYFAIL, and YYFAIL suffers from
+  inherent flaws when %error-verbose or `#define YYERROR_VERBOSE' is
+  used.  For a more detailed discussion, see:
+
+    http://lists.gnu.org/archive/html/bison-patches/2009-12/msg00024.html
+
+  The upcoming Bison 2.5 will remove YYFAIL from Java parsers, but
+  deterministic parsers in C will continue to implement it.  However,
+  because YYFAIL is already flawed, it seems futile to try to make new
+  Bison features compatible with it.  Thus, during parser generation,
+  Bison 2.5 will produce a warning whenever it discovers YYFAIL in a
+  rule action.  In a later release, YYFAIL will be disabled for
+  %error-verbose and `#define YYERROR_VERBOSE'.  Eventually, YYFAIL will
+  be removed altogether.
+
+  There exists at least one case where Bison 2.5's YYFAIL warning will
+  be a false positive.  Some projects add phony uses of YYFAIL and other
+  Bison-defined macros for the sole purpose of suppressing C
+  preprocessor warnings (from GCC cpp's -Wunused-macros, for example).
+  To avoid Bison's future warning, such YYFAIL uses can be moved to the
+  epilogue (that is, after the second `%%') in the Bison input file.  In
+  this release (2.4.2), Bison already generates its own code to suppress
+  C preprocessor warnings for YYFAIL, so projects can remove their own
+  phony uses of YYFAIL if compatibility with Bison releases prior to
+  2.4.2 is not necessary.
+
+** Internationalization.
+
+  Fix a regression introduced in Bison 2.4: Under some circumstances,
+  message translations were not installed although supported by the
+  host system.
+
 * Changes in version 2.4.1 (2008-12-11):
 
 ** In the GLR defines file, unexpanded M4 macros in the yylval and yylloc
@@ -1124,8 +1369,7 @@ End:
 
 -----
 
-Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
-2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
+Copyright (C) 1995-2010 Free Software Foundation, Inc.
 
 This file is part of Bison, the GNU Parser Generator.