X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/fcf834f9ecf080784b741782f4206df1e1a2957a..676997e53bf9e8d364302bd1f90d812e50b1477a:/NEWS?ds=sidebyside diff --git a/NEWS b/NEWS index 5b763b9d..593807c7 100644 --- a/NEWS +++ b/NEWS @@ -62,7 +62,7 @@ Bison News * Changes in version 2.5 (????-??-??): -** Named References Support +** Named references: Historically, Yacc and Bison have supported positional references ($n, $$) to allow access to symbol values from inside of semantic @@ -87,13 +87,13 @@ Bison News These features are experimental in this version. More user feedback will help to stabilize them. -** IELR(1) and Canonical LR(1) Support +** IELR(1) and canonical LR(1): IELR(1) is a minimal LR(1) parser table generation algorithm. That is, given any context-free grammar, IELR(1) generates parser tables with the full language recognition power of canonical LR(1) but with - nearly the same number of parser states as LALR(1). This reduction in - parser states is often an order of magnitude. More importantly, + nearly the same number of parser states as LALR(1). This reduction + in parser states is often an order of magnitude. More importantly, because canonical LR(1)'s extra parser states may contain duplicate conflicts in the case of non-LR(1) grammars, the number of conflicts for IELR(1) is often an order of magnitude less as well. This can @@ -157,15 +157,17 @@ Bison News LAC is an experimental feature. More user feedback will help to stabilize it. -** Unrecognized %code qualifiers are now an error not a warning. +** Grammar symbol names can now contain dashes: -** %define improvements. - -*** Unrecognized variables are now an error not a warning. + Consistently with directives (such as %error-verbose) and variables + (e.g. push-pull), grammar 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). -*** Multiple invocations for any variable is now an error not a warning. +** %define improvements: -*** Can now be invoked via the command line. +*** Can now be invoked via the command line: Each of these command-line options @@ -184,7 +186,7 @@ Bison News quietly override %define, but -D and --define do not. For further details, see the section "Bison Options" in the Bison manual. -*** Variables renamed. +*** Variables renamed: The following %define variables @@ -199,7 +201,7 @@ Bison News The old names are now deprecated but will be maintained indefinitely for backward compatibility. -*** Values no longer need to be quoted in grammar file. +*** 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, @@ -210,15 +212,75 @@ Bison News %define api.push-pull push -** Symbol names. +*** Unrecognized variables are now errors not warnings. - 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). +*** Multiple invocations for any variable is now an error not a warning. + +** Unrecognized %code qualifiers are now errors not warnings. + +** 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 + ; -** YYFAIL now produces warnings and Java parsers no longer implement it. + Bison now warns when a character literal is not of length one. In + some future release, Bison will start reporting an error instead. + +** 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. + +** C++ parsers use YYRHSLOC: + + Similarly to the C parsers, the C++ parsers now define the YYRHSLOC + macro and use it in the default YYLLOC_DEFAULT. You are encouraged + to use it. If, for instance, your location structure has "first" + and "last" members, instead of + + # define YYLLOC_DEFAULT(Current, Rhs, N) \ + do \ + if (N) \ + { \ + (Current).first = (Rhs)[1].location.first; \ + (Current).last = (Rhs)[N].location.last; \ + } \ + else \ + { \ + (Current).first = (Current).last = (Rhs)[0].location.last; \ + } \ + while (false) + + use: + + # define YYLLOC_DEFAULT(Current, Rhs, N) \ + do \ + if (N) \ + { \ + (Current).first = YYRHSLOC (Rhs, 1).first; \ + (Current).last = YYRHSLOC (Rhs, N).last; \ + } \ + else \ + { \ + (Current).first = (Current).last = YYRHSLOC (Rhs, 0).last; \ + } \ + while (false) + +** YYLLOC_DEFAULT in C++: + + The default implementation of YYLLOC_DEFAULT used to be issued in + the header file. It is now output in the implementation file, after + the user %code sections so that its #ifndef guard does not try to + override the user's YYLLOC_DEFAULT if provided. + +** 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 @@ -229,7 +291,7 @@ Bison News 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. +** Temporary hack for adding a semicolon to the user action: Previously, Bison appended a semicolon to every user action for reductions when the output language defaulted to C (specifically, when @@ -250,19 +312,6 @@ 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 syntax error message fixes: When %error-verbose or `#define YYERROR_VERBOSE' is specified, @@ -301,55 +350,6 @@ Bison News canonical LR. However, LAC is still experimental and is disabled by default. -** 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. - -** C++ parsers use YYRHSLOC - - Similarly to the C parsers, the C++ parsers now define the YYRHSLOC - macro and use it in the default YYLLOC_DEFAULT. You are encouraged - to use it. If, for instance, your location structure has "first" - and "last" members, instead of - - # define YYLLOC_DEFAULT(Current, Rhs, N) \ - do \ - if (N) \ - { \ - (Current).first = (Rhs)[1].location.first; \ - (Current).last = (Rhs)[N].location.last; \ - } \ - else \ - { \ - (Current).first = (Current).last = (Rhs)[0].location.last; \ - } \ - while (false) - - use: - - # define YYLLOC_DEFAULT(Current, Rhs, N) \ - do \ - if (N) \ - { \ - (Current).first = YYRHSLOC (Rhs, 1).first; \ - (Current).last = YYRHSLOC (Rhs, N).last; \ - } \ - else \ - { \ - (Current).first = (Current).last = YYRHSLOC (Rhs, 0).last; \ - } \ - while (false) - -** YYLLOC_DEFAULT in C++ - - The default implementation of YYLLOC_DEFAULT used to be issued in - the header file. It is now output in the implementation file, after - the user %code sections so that its #ifndef guard does not try to - override the user's YYLLOC_DEFAULT if provided. - * Changes in version 2.4.3 (2010-08-05): ** Bison now obeys -Werror and --warnings=error for warnings about @@ -1511,9 +1511,7 @@ End: ----- -Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, -2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, -Inc. +Copyright (C) 1995-2011 Free Software Foundation, Inc. This file is part of Bison, the GNU Parser Generator.