Update POTFILES.

[bison.git] / NEWS

diff --git a/NEWS b/NEWS
index 342b49fc473b03b48c793997b04615aac2d9b3d4..9933922c702098952533993354c98187336687b3 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -119,6 +119,23 @@ 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


@@ -162,10 +179,31 @@ 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:


@@ -189,6 +227,45 @@ 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,
 ** Internationalization.
 
   Fix a regression introduced in Bison 2.4: Under some circumstances,


@@ -1242,8 +1319,7 @@ 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.