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.
%defines "parser.h"
+* When reporting useless rules, useless nonterminals, and unused terminals,
+ Bison now employs the terms "useless in grammar" instead of "useless",
+ "useless in parser" instead of "never reduced", and "unused in grammar"
+ instead of "unused".
+
+* 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
+ "useless in parser due to 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.
+
+* --report-file=FILE is a new flag to override the default `.output' file name.
+
* The `=' that used to be required in the following directives is now
deprecated:
%name-prefix "c_"
%output "parser.c"
-* The quotes around NAME that used to be required in the following directive
- are now deprecated:
+* An Alternative to `%{...%}' -- `%code QUALIFIER {CODE}'
- %define NAME "VALUE"
-
-* 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
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
See the section `Freeing Discarded Symbols' in the Bison manual for further
details.
+* %left, %right, and %nonassoc can now declare token numbers. This is required
+ by POSIX. However, see the end of section `Operator Precedence' in the Bison
+ manual for a caveat concerning the treatment of literal strings.
+
+* The nonfunctional --no-parser, -n, and %no-parser options have been
+ completely removed from Bison.
+
Changes in version 2.3a, 2006-09-13:
* Instead of %union, you can define and use your own union type
-----
Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
-2004, 2005, 2006, 2007 Free Software Foundation, Inc.
+2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
This file is part of Bison, the GNU Compiler Compiler.
projects / bison.git / blobdiff