X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/5b1ff42379edbbf37b135d33aa5fb3c72da2dca1..02354690ee02dfa05564137aafc6721eb54d21ab:/NEWS?ds=sidebyside diff --git a/NEWS b/NEWS index d5851390..acdd5be1 100644 --- a/NEWS +++ b/NEWS @@ -169,6 +169,17 @@ Bison News 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. + ** Temporary hack for adding a semicolon to the user action. Previously, Bison appended a semicolon to every user action for @@ -212,10 +223,47 @@ Bison News were resolved with %nonassoc. Such tokens are now properly omitted from the list. -* Changes in version 2.4.2 (????-??-??): +** 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 2.4.3 (????-??-??): + +** Problems with spawning M4 on at least FreeBSD 8 and FreeBSD 9 have + been fixed. + +** Failures in the test suite for GCC 4.5 have been fixed. + +** Failures in the test suite for some versions of Sun Studio C++ have + been fixed. + +* Changes in version 2.4.2 (2010-03-20): + +** 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 addressed. As a result, fatal Bison + errors should 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: @@ -239,6 +287,45 @@ Bison News 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, @@ -1292,8 +1379,7 @@ 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.