X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/0e021770cc023c6a2e7ae132a3aab55bc7cbc058..f16b08196c780556cbf50691e2944960aebc46f6:/NEWS diff --git a/NEWS b/NEWS index 119521cc..0e4061aa 100644 --- a/NEWS +++ b/NEWS @@ -3,6 +3,18 @@ Bison News Changes in version 2.3a+ (????-??-??): +* Previously, Bison sometimes generated parser tables with states that were + unreachable due to conflicts in predecessor states. Bison now: + + 1. Removes unreachable states. + + 2. Does not report any conflicts that appeared in unreachable states. + WARNING: As a result, you may need to update %expect and %expect-rr + directives in existing grammar files. + + 3. For any rule used only in such states, Bison now reports the rule as + "never reduced because of conflicts". + * The -g and --graph options now output graphs in Graphviz DOT format, not VCG format. @@ -16,13 +28,37 @@ Changes in version 2.3a+ (????-??-??): %defines "parser.h" -* The `=' that used to be required in the following declarations is now +* The `=' that used to be required in the following directives is now deprecated: %file-prefix "parser" %name-prefix "c_" %output "parser.c" +* The quotes around NAME that used to be required in the following directive + are now deprecated: + + %define NAME "VALUE" + +* Bison 2.3a provided a new set of directives as a more flexible alternative to + the traditional Yacc prologue blocks. Those have now been consolidated into + a single %code directive with an optional qualifier field, which identifies + the purpose of the code and thus the location(s) where Bison should generate + it: + + 1. `%code {CODE}' replaces `%after-header {CODE}' + 2. `%code requires {CODE}' replaces `%start-header {CODE}' + 3. `%code provides {CODE}' replaces `%end-header {CODE}' + 4. `%code top {CODE}' replaces `%before-header {CODE}' + + See the %code entries in section `Bison Declaration Summary' in the Bison + manual for a summary of the new functionality. See the new section `Prologue + Alternatives' for a detailed discussion including the advantages of %code + over the traditional Yacc prologues. + + The prologue alternatives are experimental. More user feedback will help to + determine whether they should become permanent features. + * Revised warning: unset or unused mid-rule values Since Bison 2.2, Bison has warned about mid-rule values that are set but not @@ -66,76 +102,6 @@ Changes in version 2.3a+ (????-??-??): See the section `Freeing Discarded Symbols' in the Bison manual for further details. -* The Yacc prologue alternatives from Bison 2.3a have been rewritten as the - following directives: - - 1. %code {CODE} - - Other than semantic actions, this is probably the most common place you - should write verbatim code for the parser implementation. It replaces - the traditional Yacc prologue, `%{CODE%}', for most purposes. Compare - with: - - - `%{CODE%}' appearing after the first `%union {CODE}' in a grammar - file. While Bison will continue to support `%{CODE%}' for backward - compatibility, `%code {CODE}' is cleaner as its functionality does - not depend on its position in the grammar file relative to any - `%union {CODE}'. Specifically, `%code {CODE}' always inserts your - CODE into the parser code file after the usual contents of the - parser header file. - - `%after-header {CODE}', which only Bison 2.3a supported. - - 2. %requires {CODE} - - This is the right place to write dependency code for externally exposed - definitions required by Bison. Such exposed definitions are those - usually appearing in the parser header file. Thus, this is the right - place to define types referenced in `%union {CODE}' directives, and it - is the right place to override Bison's default YYSTYPE and YYLTYPE - definitions. Compare with: - - - `%{CODE%}' appearing before the first `%union {CODE}' in a grammar - file. Unlike `%{CODE%}', `%requires {CODE}' inserts your CODE both - into the parser code file and into the parser header file since - Bison's required definitions should depend on it in both places. - - `%start-header {CODE}', which only Bison 2.3a supported. - - 3. %provides {CODE} - - This is the right place to write additional definitions you would like - Bison to expose externally. That is, this directive inserts your CODE - both into the parser header file and into the parser code file after - Bison's required definitions. Compare with: - - - `%end-header {CODE}', which only Bison 2.3a supported. - - 4. %code-top {CODE} - - Occasionally it is desirable to insert code near the top of the parser - code file. For example: - - %code-top { - #define _GNU_SOURCE - #include - } - - Compare with: - - - `%{CODE%}' appearing before the first `%union {CODE}' in a grammar - file. `%code-top {CODE}' is cleaner as its functionality does not - depend on its position in the grammar file relative to any - `%union {CODE}'. - - `%before-header {CODE}', which only Bison 2.3a supported. - - If you have multiple occurrences of any one of the above four directives, - Bison will concatenate the contents in the order they appear in the grammar - file. - - The prologue alternatives are experimental. More user feedback will help to - determine whether they should become permanent features. - - Also see the new section `Prologue Alternatives' in the Bison manual. - Changes in version 2.3a, 2006-09-13: * Instead of %union, you can define and use your own union type @@ -960,21 +926,19 @@ End: ----- Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, -2004, 2005, 2006 Free Software Foundation, Inc. +2004, 2005, 2006, 2007 Free Software Foundation, Inc. This file is part of Bison, the GNU Compiler Compiler. -Bison is free software; you can redistribute it and/or modify +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 -the Free Software Foundation; either version 2, or (at your option) -any later version. +the Free Software Foundation, either version 3 of the License, or +(at your option) any later version. -Bison is distributed in the hope that it will be useful, +This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License -along with autoconf; see the file COPYING. If not, write to -the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, -Boston, MA 02110-1301, USA. +along with this program. If not, see .