Bison News
----------
-* Changes in version ?.? (????-??-??):
+* Changes in version 2.4.2 (????-??-??):
+
+** Some portability problems that resulted in failures and livelocks
+ in the test suite on some versions of at least Solaris, AIX, HP-UX,
+ RHEL4, and Tru64 have been fixed. As part of those fixes, fatal
+ Bison errors no longer cause M4 to report a broken pipe on the
+ affected platforms.
+
+** `%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
declarations have been fixed.
exp: exp "+" exp { $$ = $1 + $3; };
- This prevents the future support for languages than do not use `;'
- as C/C++/Java do. Yet some grammars still depend on this `feature'.
- Bison 2.4.1 restores the previous behavior in the case of C output
- to leave more time for grammars depending on the old behavior to be
- adjusted. Future releases of Bison will disable this feature.
+ 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.
-----
-Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
-2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
+Copyright (C) 1995-2010 Free Software Foundation, Inc.
-This file is part of Bison, the GNU Compiler Compiler.
+This file is part of Bison, the GNU Parser Generator.
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
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