Thank the developer of the initial push parser implementation.

[bison.git] / NEWS

diff --git a/NEWS b/NEWS
index 6bfe53a73c56c695280d02d9cfa1fce3b028abd1..ae87c0af64f99a7e8e3057657fd269f02858337f 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -3,7 +3,22 @@ Bison News
 
 * Changes in version ?.? (????-??-??):
 
 
 * 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
 
   The constants for token names were moved to the Lexer interface.
   Also, it is possible to add code to the parser's constructors using


@@ -38,6 +53,31 @@ Bison News
 
 * Changes in version 2.5 (????-??-??):
 
 
 * 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
 ** IELR(1) and Canonical LR(1) Support
 
   IELR(1) is a minimal LR(1) parser table generation algorithm.  That


@@ -55,9 +95,9 @@ Bison News
   default.  You can specify the type of parser tables in the grammar
   file with these directives:
 
   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 reduction optimization in the parser tables can also be
   adjusted using `%define lr.default-reductions'.  See the documentation
 
   The default reduction optimization in the parser tables can also be
   adjusted using `%define lr.default-reductions'.  See the documentation


@@ -68,9 +108,15 @@ Bison News
   These features are experimental.  More user feedback will help to
   stabilize them.
 
   These features are experimental.  More user feedback will help to
   stabilize them.
 

-** Multiple %define's for any variable is now an error not a warning.
+** 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.

 
 

-** %define can now be invoked via the command line.
+*** Can now be invoked via the command line.

 
   Each of these command-line options
 
 
   Each of these command-line options
 


@@ -89,7 +135,7 @@ Bison News
   quietly override %define, but -D and --define do not.  For further
   details, see the section "Bison Options" in the Bison manual.
 
   quietly override %define, but -D and --define do not.  For further
   details, see the section "Bison Options" in the Bison manual.
 

-** %define variables renamed.
+*** Variables renamed.

 
   The following %define variables
 
 
   The following %define variables
 


@@ -104,7 +150,18 @@ Bison News
   The old names are now deprecated but will be maintained indefinitely
   for backward compatibility.
 
   The old names are now deprecated but will be maintained indefinitely
   for backward compatibility.
 

-** Symbols names
+*** 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.

 
   Consistently with directives (such as %error-verbose) and variables
   (e.g. push-pull), symbol names may include dashes in any position,
 
   Consistently with directives (such as %error-verbose) and variables
   (e.g. push-pull), symbol names may include dashes in any position,


@@ -112,6 +169,23 @@ Bison News
   POSIX Yacc whose use is reported by -Wyacc, and rejected in Yacc
   mode (--yacc).
 
   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.
 
   Previously, Bison appended a semicolon to every user action for
 ** Temporary hack for adding a semicolon to the user action.
 
   Previously, Bison appended a semicolon to every user action for


@@ -155,10 +229,31 @@ Bison News
   were resolved with %nonassoc.  Such tokens are now properly omitted
   from the list.
 
   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 (????-??-??):
 
 * 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.
 
 ** 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 is now a permanent feature.
 
   A traditional Yacc prologue directive is written in the form:


@@ -182,6 +277,51 @@ Bison News
   Bison's Java feature as a whole including its current usage of %code
   is still considered experimental.
 
   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
 * Changes in version 2.4.1 (2008-12-11):
 
 ** In the GLR defines file, unexpanded M4 macros in the yylval and yylloc


@@ -1229,8 +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.
 
 
 This file is part of Bison, the GNU Parser Generator.