Bison News
----------
-Changes in version 1.49a:
-
-* Revert the C++ namespace changes introduced in 1.31, as they caused too
- many portability hassles.
-
-* Items overflow
- Bison no longer dumps core when there are too many items, it just
- dies.
+Changes in version 1.49b, 2002-08-12:
+
+* GLR parsing
+ The declaration
+ %glr-parser
+ causes Bison to produce a Generalized LR (GLR) parser, capable of handling
+ almost any context-free grammar, ambiguous or not. The new declarations
+ %dprec and %merge on grammar rules allow parse-time resolution of
+ ambiguities. Contributed by Paul Hilfinger.
+
+* Output Directory
+ When not in Yacc compatibility mode, when the output file was not
+ specified, runnning `bison foo/bar.y' created `foo/bar.c'. It
+ now creates `bar.c'.
+
+* Undefined token
+ The undefined token was systematically mapped to 2 which prevented
+ the use of 2 from the user. This is no longer the case.
+
+* Unknown token numbers
+ If yylex returned a code out of range, yyparse could die. This is
+ no longer the case.
+
+* Error token
+ According to POSIX, the error token should be numbered as 256.
+ Bison extends this requirement by making it a preference: *if* the
+ user specified that one of her tokens is numbered 256, then error
+ will be mapped onto another number.
+
+* Verbose error messages
+ They no longer report `..., expecting error or...' for state where
+ error recovery is possible.
+
+* End token
+ Defaults to `$end' instead of `$'.
+
+* Error recovery now conforms to documentation and to POSIX
+ When a Bison-generated parser encounters a syntax error, it now pops
+ the stack until it finds a state that allows shifting the error
+ token. Formerly, it popped the stack until it found a state that
+ allowed some non-error action other than a default reduction on the
+ error token. The new behavior has long been the documented behavior,
+ and has long been required by POSIX. For more details, please see
+ <http://mail.gnu.org/pipermail/bug-bison/2002-May/001452.html>.
+
+* Traces
+ Popped tokens and nonterminals are now reported.
+
+* Larger grammars
+ Larger grammars are now supported (larger token numbers, larger grammar
+ size (= sum of the LHS and RHS lengths), larger LALR tables).
+ Formerly, many of these numbers ran afoul of 16-bit limits;
+ now these limits are 32 bits on most hosts.
+
+* Explicit initial rule
+ Bison used to play hacks with the initial rule, which the user does
+ not write. It is now explicit, and visible in the reports and
+ graphs as rule 0.
+
+* Useless rules
+ Before, Bison reported the useless rules, but, although not used,
+ included them in the parsers. They are now actually removed.
+
+* Useless rules, useless nonterminals
+ They are now reported, as a warning, with their locations.
+
+* Rules never reduced
+ Rules that can never be reduced because of conflicts are now
+ reported.
+
+* Incorrect `Token not used'
+ On a grammar such as
+
+ %token useless useful
+ %%
+ exp: '0' %prec useful;
+
+ where a token was used to set the precedence of the last rule,
+ bison reported both `useful' and `useless' as useless tokens.
+
+* Revert the C++ namespace changes introduced in 1.31
+ as they caused too many portability hassles.
+
+* Default locations
+ By an accident of design, the default computation of @$ was
+ performed after another default computation was performed: @$ = @1.
+ The latter is now removed: YYLLOC_DEFAULT is fully responsible of
+ the computation of @$.
* Token end-of-file
The token end of file may be specified by the user, in which case,
the user symbol is used in the reports, the graphs, and the verbose
- error messages instead of `$', which remains being the defaults.
+ error messages instead of `$end', which remains being the default.
For instance
%token YYEOF 0
or
%token YYEOF 0 "end of file"
+
+* Semantic parser
+ This old option, which has been broken for ages, is removed.
+
+* New translations
+ Brazilian Portuguese, thanks to Alexandre Folle de Menezes.
+ Croatian, thanks to Denis Lackovic.
+
+* Incorrect token definitions
+ When fed with `%token 'a' "A"', Bison used to output `#define 'a' 65'.
+
+* Token definitions as enums
+ Tokens are output both as the traditional #define's, and, provided
+ the compiler supports ANSI C or is a C++ compiler, as enums.
+ This helps debuggers producing symbols instead of values.
+
+* Reports
+ In addition to --verbose, bison supports --report=THINGS, which
+ produces additional information:
+ - itemset
+ complete the core item sets with their closure
+ - lookahead
+ explicitly associate lookaheads to items
+ - solved
+ describe shift/reduce conflicts solving.
+ Bison used to systematically output this information on top of
+ the report. Solved conflicts are now attached to their states.
+
+* Type clashes
+ Previous versions don't complain when there is a type clash on
+ the default action if the rule has a mid-rule action, such as in:
+
+ %type <foo> bar
+ %%
+ bar: '0' {} '0';
+
+ This is fixed.
+
+* GNU M4 is now required when using Bison.
+\f
+Changes in version 1.35, 2002-03-25:
+
+* C Skeleton
+ Some projects use Bison's C parser with C++ compilers, and define
+ YYSTYPE as a class. The recent adjustment of C parsers for data
+ alignment and 64 bit architectures made this impossible.
+
+ Because for the time being no real solution for C++ parser
+ generation exists, kludges were implemented in the parser to
+ maintain this use. In the future, when Bison has C++ parsers, this
+ kludge will be disabled.
+
+ This kludge also addresses some C++ problems when the stack was
+ extended.
+
+\f
+Changes in version 1.34, 2002-03-12:
+
+* File name clashes are detected
+ $ bison foo.y -d -o foo.x
+ fatal error: header and parser would both be named `foo.x'
+
+* A missing `;' at the end of a rule triggers a warning
+ In accordance with POSIX, and in agreement with other
+ Yacc implementations, Bison will mandate this semicolon in the near
+ future. This eases the implementation of a Bison parser of Bison
+ grammars by making this grammar LALR(1) instead of LR(2). To
+ facilitate the transition, this release introduces a warning.
+
+* Revert the C++ namespace changes introduced in 1.31, as they caused too
+ many portability hassles.
+
+* DJGPP support added.
+
+* Fix test suite portability problems.
+\f
+Changes in version 1.33, 2002-02-07:
+
+* Fix C++ issues
+ Groff could not be compiled for the definition of size_t was lacking
+ under some conditions.
+
+* Catch invalid @n
+ As is done with $n.
+\f
+Changes in version 1.32, 2002-01-23:
+
+* Fix Yacc output file names
+
+* Portability fixes
+
+* Italian, Dutch translations
\f
Changes in version 1.31, 2002-01-14:
* Better C++ compliance
The output parsers try to respect C++ namespaces.
+ [This turned out to be a failed experiment, and it was reverted later.]
* Reduced Grammars
Fixed bugs when reporting useless nonterminals.
* --output
New, aliasing `--output-file'.
\f
-Changes in version 1.30:
+Changes in version 1.30, 2001-10-26:
* `--defines' and `--graph' have now an optionnal argument which is the
output file name. `-d' and `-g' do not change, they do not take any
Local Variables:
mode: outline
End:
+
+-----
+
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