X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/75ad86eebd3f49dff81976eb83036eb7b7793e68..d0ee410565c9d7bc876af42583ee092568f44fa8:/NEWS?ds=sidebyside diff --git a/NEWS b/NEWS index 854023cc..18e71b7d 100644 --- a/NEWS +++ b/NEWS @@ -3,17 +3,30 @@ 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: +* The quotes around NAME that used to be required in the following directive + are now deprecated: - 1. Removes unreachable states. + %define NAME "VALUE" - 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. +* The directive `%pure-parser' is now deprecated in favor of: - 3. For any rule used only in such states, Bison now reports the rule as - "never reduced because of conflicts". + %define api.pure + + which has the same effect except that Bison is more careful to warn about + unreasonable usage in the latter case. + +* Push Parsing + + Bison can now generate an LALR(1) parser in C with a push interface. That + is, instead of invoking yyparse, which pulls tokens from `yylex', you can + push one token at a time to the parser using `yypush_parse', which will + return to the caller after processing each token. By default, the push + interface is disabled. Either of the following directives will enable it: + + %define api.push_pull "push" // Just push; does not require yylex. + %define api.push_pull "both" // Push and pull; requires yylex. + + See the new section `A Push Parser' in the Bison manual for details. * The -g and --graph options now output graphs in Graphviz DOT format, not VCG format. @@ -28,6 +41,39 @@ Changes in version 2.3a+ (????-??-??): %defines "parser.h" +* Unreachable State Removal + + Previously, Bison sometimes generated parser tables containing unreachable + states. A state can become unreachable during conflict resolution if Bison + disables a shift action leading to it from a predecessor state. 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". + + This feature can be disabled with the following directive: + + %define lr.keep_unreachable_states + + See the %define entry in the `Bison Declaration Summary' in the Bison manual + for further discussion. + +* Lookahead Set Correction in the `.output' Report + + When instructed to generate a `.output' file including lookahead sets + (using `--report=lookahead', for example), Bison now prints each reduction's + lookahead set only next to the associated state's one item that (1) is + associated with the same rule as the reduction and (2) has its dot at the end + of its RHS. Previously, Bison also erroneously printed the lookahead set + next to all of the state's other items associated with the same rule. This + bug affected only the `.output' file and not the generated parser source + code. + * The `=' that used to be required in the following directives is now deprecated: @@ -35,12 +81,9 @@ Changes in version 2.3a+ (????-??-??): %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" +* An Alternative to `%{...%}' -- `%code QUALIFIER {CODE}' -* Bison 2.3a provided a new set of directives as a more flexible alternative to + 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 @@ -51,8 +94,8 @@ Changes in version 2.3a+ (????-??-??): 3. `%code provides {CODE}' replaces `%end-header {CODE}' 4. `%code top {CODE}' replaces `%before-header {CODE}' - See the %code entries in `Appendix A Bison Symbols' in the Bison manual for a - summary of the new functionality. See the new section `Prologue + 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. @@ -79,7 +122,9 @@ Changes in version 2.3a+ (????-??-??): To enable these warnings, specify the flag `--warnings=midrule-values' or `-W', which is a synonym for `--warnings=all'. -* Bison now recognizes two separate kinds of default %destructor's and +* Default %destructor or %printer with `<*>' or `<>' + + Bison now recognizes two separate kinds of default %destructor's and %printer's: 1. Place `<*>' in a %destructor/%printer symbol list to define a default @@ -930,17 +975,15 @@ Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 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 .