Bison News
----------
-* Changes in version 2.5 (????-??-??):
+* Changes in version 2.5.1 (????-??-??):
+
+** Future changes:
+
+ The next major release will drop support for K&R C.
+
+** yacc.c: YYBACKUP works as expected.
+
+** glr.c improvements:
+
+*** Location support is eliminated when not requested:
+
+ GLR parsers used to include location-related code even when
+ locations were not requested, and therefore not even usable.
+
+*** __attribute__ is preserved:
+
+ __attribute__ is no longer disabled when __STRICT_ANSI__ is defined
+ (i.e., when -std is passed to GCC).
+
+** lalr1.java: several fixes:
+
+ The Java parser no longer throws ArrayIndexOutOfBoundsException if
+ the first token leads to a syntax error. Some minor clean ups.
+
+** C++11 compatibility:
+
+ C and C++ parsers use nullptr instead of 0 when __cplusplus is
+ 201103L or higher.
+
+** C++ locations:
+
+ The position and location constructors (and their initialize
+ methods) accept new arguments for line and column. Several issues
+ in the documentation were fixed.
+
+** liby is no longer asking for "rpl_fprintf" on some platforms.
+
+** Changes in the manual:
+
+*** %printer is documented
+
+ The %printer directive, supported since at least Bison 1.50, is
+ finally documented. The %mfcalc example is extended to demonstrate
+ its use of printer.
+
+ The C++ parsers now also support yyoutput (as an alias to
+ debug_stream ()) for consistency with the C skeletons.
+
+*** Several improvements have been made:
+
+ The layout for grammar excerpts was changed to a more compact
+ scheme. Named references are motivated. The description of the
+ automaton description file (*.output) is updated to the current
+ format. Incorrect index entries were fixed. Some other errors were
+ fixed.
+
+** Changes to the build system:
+
+*** Warnings during the build procedure have been eliminated.
+
+*** Several portability problems in the test suite have been fixed:
+
+ This includes warnings with some compilers, unexpected behavior of
+ tools such as diff, warning messages from the test suite itself,
+ etc.
+
+*** The install-pdf target work properly:
+
+ Running "make install-pdf" (or -dvi, -html, -info, and -ps) no
+ longer halts in the middle of its course.
+
+* Changes in version 2.5 (2011-05-14):
** Grammar symbol names can now contain non-initial dashes:
When no ambiguity is possible, original symbol names may be used
as named references:
- if_stmt : 'if' cond_expr 'then' then_stmt ';'
+ if_stmt : "if" cond_expr "then" then_stmt ';'
{ $if_stmt = mk_if_stmt($cond_expr, $then_stmt); }
In the more common case, explicit names may be declared:
- stmt[res] : 'if' expr[cond] 'then' stmt[then] 'else' stmt[else] ';'
+ stmt[res] : "if" expr[cond] "then" stmt[then] "else" stmt[else] ';'
{ $res = mk_if_stmt($cond, $then, $else); }
Location information is also accessible using @name syntax. When
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
+ 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,
because canonical LR(1)'s extra parser states may contain duplicate
%define lr.type ielr
%define lr.type canonical-lr
- The default reduction optimization in the parser tables can also be
- adjusted using `%define lr.default-reductions'. See the documentation
- for `%define lr.type' and `%define lr.default-reductions' in the
- section `Bison Declaration Summary' in the Bison manual for the
- details.
+ The default-reduction optimization in the parser tables can also be
+ adjusted using `%define lr.default-reductions'. For details on both
+ of these features, see the new section `Tuning LR' in the Bison
+ manual.
These features are experimental. More user feedback will help to
stabilize them.
-** LAC (lookahead correction) for syntax error handling:
+** LAC (Lookahead Correction) for syntax error handling:
Canonical LR, IELR, and LALR can suffer from a couple of problems
upon encountering a syntax error. First, the parser might perform
additional parser stack reductions before discovering the syntax
- error. Such reductions perform user semantic actions that are
+ error. Such reductions can perform user semantic actions that are
unexpected because they are based on an invalid token, and they
cause error recovery to begin in a different syntactic context than
the one in which the invalid token was encountered. Second, when
- verbose error messages are enabled (with %error-verbose or `#define
- YYERROR_VERBOSE'), the expected token list in the syntax error
- message can both contain invalid tokens and omit valid tokens.
+ verbose error messages are enabled (with %error-verbose or the
+ obsolete `#define YYERROR_VERBOSE'), the expected token list in the
+ syntax error message can both contain invalid tokens and omit valid
+ tokens.
The culprits for the above problems are %nonassoc, default
reductions in inconsistent states, and parser state merging. Thus,
%nonassoc is used or if default reductions are enabled for
inconsistent states.
- LAC is a new mechanism within the parsing algorithm that completely
- solves these problems for canonical LR, IELR, and LALR without
- sacrificing %nonassoc, default reductions, or state mering. When
- LAC is in use, canonical LR and IELR behave exactly the same for
- both syntactically acceptable and syntactically unacceptable input.
+ LAC is a new mechanism within the parsing algorithm that solves
+ these problems for canonical LR, IELR, and LALR without sacrificing
+ %nonassoc, default reductions, or state merging. When LAC is in
+ use, canonical LR and IELR behave almost exactly the same for both
+ syntactically acceptable and syntactically unacceptable input.
While LALR still does not support the full language-recognition
power of canonical LR and IELR, LAC at least enables LALR's syntax
error handling to correctly reflect LALR's language-recognition
%define parse.lac full
- See the documentation for `%define parse.lac' in the section `Bison
- Declaration Summary' in the Bison manual for additional details.
+ See the new section `LAC' in the Bison manual for additional
+ details including a few caveats.
LAC is an experimental feature. More user feedback will help to
stabilize it.
except that the manner in which Bison processes multiple definitions
for the same NAME differs. Most importantly, -F and --force-define
quietly override %define, but -D and --define do not. For further
- details, see the section "Bison Options" in the Bison manual.
+ details, see the section `Bison Options' in the Bison manual.
*** Variables renamed:
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 the grammar file:
If a %define value is an identifier, it no longer needs to be placed
within quotations marks. For example,
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
+ to use it. If, for instance, your location structure has `first'
+ and `last' members, instead of
# define YYLLOC_DEFAULT(Current, Rhs, N) \
do \
** Verbose syntax error message fixes:
- When %error-verbose or `#define YYERROR_VERBOSE' is specified,
- syntax error messages produced by the generated parser include the
- unexpected token as well as a list of expected tokens. The effect
- of %nonassoc on these verbose messages has been corrected in two
- ways, but a complete fix requires LAC, described above:
+ When %error-verbose or the obsolete `#define YYERROR_VERBOSE' is
+ specified, syntax error messages produced by the generated parser
+ include the unexpected token as well as a list of expected tokens.
+ The effect of %nonassoc on these verbose messages has been corrected
+ in two ways, but a more complete fix requires LAC, described above:
*** When %nonassoc is used, there can exist parser states that accept no
tokens, and so the parser does not always require a lookahead token
in order to detect a syntax error. Because no unexpected token or
expected tokens can then be reported, the verbose syntax error
message described above is suppressed, and the parser instead
- reports the simpler message, "syntax error". Previously, this
+ reports the simpler message, `syntax error'. Previously, this
suppression was sometimes erroneously triggered by %nonassoc when a
lookahead was actually required. Now verbose messages are
suppressed only when all previous lookaheads have already been
canonical LR. However, LAC is still experimental and is disabled
by default.
-** A location handling bug in the Java skeleton has been fixed.
+** Java skeleton fixes:
+
+*** A location handling bug has been fixed.
+
+*** The top element of each of the value stack and location stack is now
+ cleared when popped so that it can be garbage collected.
+
+*** Parser traces now print the top element of the stack.
+
+** -W/--warnings fixes:
+
+*** Bison now properly recognizes the `no-' versions of categories:
+
+ For example, given the following command line, Bison now enables all
+ warnings except warnings for incompatibilities with POSIX Yacc:
+
+ bison -Wall,no-yacc gram.y
+
+*** Bison now treats S/R and R/R conflicts like other warnings:
+
+ Previously, conflict reports were independent of Bison's normal
+ warning system. Now, Bison recognizes the warning categories
+ `conflicts-sr' and `conflicts-rr'. This change has important
+ consequences for the -W and --warnings command-line options. For
+ example:
+
+ bison -Wno-conflicts-sr gram.y # S/R conflicts not reported
+ bison -Wno-conflicts-rr gram.y # R/R conflicts not reported
+ bison -Wnone gram.y # no conflicts are reported
+ bison -Werror gram.y # any conflict is an error
+
+ However, as before, if the %expect or %expect-rr directive is
+ specified, an unexpected number of conflicts is an error, and an
+ expected number of conflicts is not reported, so -W and --warning
+ then have no effect on the conflict report.
+
+*** The `none' category no longer disables a preceding `error':
+
+ For example, for the following command line, Bison now reports
+ errors instead of warnings for incompatibilities with POSIX Yacc:
+
+ bison -Werror,none,yacc gram.y
+
+*** The `none' category now disables all Bison warnings:
+
+ Previously, the `none' category disabled only Bison warnings for
+ which there existed a specific -W/--warning category. However,
+ given the following command line, Bison is now guaranteed to
+ suppress all warnings:
+
+ bison -Wnone gram.y
+
+** Precedence directives can now assign token number 0:
+
+ Since Bison 2.3b, which restored the ability of precedence
+ directives to assign token numbers, doing so for token number 0 has
+ produced an assertion failure. For example:
+
+ %left END 0
+
+ This bug has been fixed.
* Changes in version 2.4.3 (2010-08-05):
** The output file does not define const, as this caused problems when used
with common autoconfiguration schemes. If you still use ancient compilers
that lack const, compile with the equivalent of the C compiler option
- `-Dconst='. autoconf's AC_C_CONST macro provides one way to do this.
+ `-Dconst='. Autoconf's AC_C_CONST macro provides one way to do this.
** Added `-g' and `--graph'.
\f
* Changes in version 1.26:
-** Bison now uses automake.
+** Bison now uses Automake.
** New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>.
** Tokens can now be specified as multiple-character strings: for
example, you could use "<=" for a token which looks like <=, instead
-of chosing a name like LESSEQ.
+of choosing a name like LESSEQ.
** The %token_table declaration says to write a table of tokens (names
and numbers) into the parser file. The yylex function can use this
Output file does not redefine const for C++.
-Local Variables:
-mode: outline
-End:
-
-----
-Copyright (C) 1995-2011 Free Software Foundation, Inc.
+Copyright (C) 1995-2012 Free Software Foundation, Inc.
This file is part of Bison, the GNU Parser Generator.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+ LocalWords: yacc YYBACKUP glr GCC lalr ArrayIndexOutOfBoundsException nullptr
+ LocalWords: cplusplus liby rpl fprintf mfcalc Wyacc stmt cond expr mk sym lr
+ LocalWords: IELR ielr Lookahead YYERROR nonassoc LALR's api lookaheads yychar
+ LocalWords: destructor lookahead YYRHSLOC YYLLOC Rhs ifndef YYFAIL cpp sr rr
+ LocalWords: preprocessor initializer Wno Wnone Werror FreeBSD prec livelocks
+ LocalWords: Solaris AIX UX RHEL Tru LHS gcc's Wundef YYENABLE NLS YYLTYPE VCG
+ LocalWords: yyerror cpp's Wunused yylval yylloc prepend yyparse yylex yypush
+ LocalWords: Graphviz xml nonterminals midrule destructor's YYSTYPE typedef ly
+ LocalWords: CHR chr printf stdout namespace preprocessing enum pre include's
+ LocalWords: YYRECOVERING nonfree destructors YYABORT YYACCEPT params enums de
+ LocalWords: struct yystype DJGPP lex param Haible NUM alloca YYSTACK NUL goto
+ LocalWords: YYMAXDEPTH Unescaped UCNs YYLTYPE's yyltype typedefs inline Yaccs
+ LocalWords: Heriyanto Reenable dprec Hilfinger Eggert MYEOF Folle Menezes EOF
+ LocalWords: Lackovic define's itemset Groff Gettext malloc NEWS'ed YYDEBUG
+ LocalWords: namespaces strerror const autoconfiguration Dconst Autoconf's FDL
+ LocalWords: Automake TMPDIR LESSEQ
+
+Local Variables:
+mode: outline
+End:
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