Mail Archives: cygwin/2006/07/09/15:07:55
I've made a new version of 'bison' available for download. This updates
the package to the latest version available from ftp.gnu.org. I've included
the relevant portions of the Bison NEWS file at the end of this message.
For a brief description of this package, see http://cygwin.com/packages/ .
To update your installation, click on the "Install Cygwin now" link on
the http://cygwin.com/ web page. This downloads setup.exe to your
system. Run setup.exe to install or update the bison package.
If you have questions or comments, please send them to the Cygwin
mailing list. I would appreciate it if you would use the mailing list
rather than emailing me directly.
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Bison News
----------
Changes in version 2.3, 2006-06-05:
* GLR grammars should now use `YYRECOVERING ()' instead of `YYRECOVERING',
for compatibility with LALR(1) grammars.
* It is now documented that any definition of YYSTYPE or YYLTYPE should
be to a type name that does not contain parentheses or brackets.
Changes in version 2.2, 2006-05-19:
* The distribution terms for all Bison-generated parsers now permit
using the parsers in nonfree programs. Previously, this permission
was granted only for Bison-generated LALR(1) parsers in C.
* %name-prefix changes the namespace name in C++ outputs.
* The C++ parsers export their token_type.
* Bison now allows multiple %union declarations, and concatenates
their contents together.
* New warning: unused values
Right-hand side symbols whose values are not used are reported,
if the symbols have destructors. For instance:
exp: exp "?" exp ":" exp { $1 ? $1 : $3; }
| exp "+" exp
;
will trigger a warning about $$ and $5 in the first rule, and $3 in
the second ($1 is copied to $$ by the default rule). This example
most likely contains three errors, and could be rewritten as:
exp: exp "?" exp ":" exp
{ $$ = $1 ? $3 : $5; free ($1 ? $5 : $3); free ($1); }
| exp "+" exp
{ $$ = $1 ? $1 : $3; if ($1) free ($3); }
;
However, if the original actions were really intended, memory leaks
and all, the warnings can be suppressed by letting Bison believe the
values are used, e.g.:
exp: exp "?" exp ":" exp { $1 ? $1 : $3; (void) ($$, $5); }
| exp "+" exp { $$ = $1; (void) $3; }
;
If there are mid-rule actions, the warning is issued if no action
uses it. The following triggers no warning: $1 and $3 are used.
exp: exp { push ($1); } '+' exp { push ($3); sum (); };
The warning is intended to help catching lost values and memory leaks.
If a value is ignored, its associated memory typically is not reclaimed.
* %destructor vs. YYABORT, YYACCEPT, and YYERROR.
Destructors are now called when user code invokes YYABORT, YYACCEPT,
and YYERROR, for all objects on the stack, other than objects
corresponding to the right-hand side of the current rule.
* %expect, %expect-rr
Incorrect numbers of expected conflicts are now actual errors,
instead of warnings.
* GLR, YACC parsers.
The %parse-params are available in the destructors (and the
experimental printers) as per the documentation.
* Bison now warns if it finds a stray `$' or `@' in an action.
* %require "VERSION"
This specifies that the grammar file depends on features implemented
in Bison version VERSION or higher.
* lalr1.cc: The token and value types are now class members.
The tokens were defined as free form enums and cpp macros. YYSTYPE
was defined as a free form union. They are now class members:
tokens are enumerations of the `yy::parser::token' struct, and the
semantic values have the `yy::parser::semantic_type' type.
If you do not want or can update to this scheme, the directive
`%define "global_tokens_and_yystype" "1"' triggers the global
definition of tokens and YYSTYPE. This change is suitable both
for previous releases of Bison, and this one.
If you wish to update, then make sure older version of Bison will
fail using `%require "2.2"'.
* DJGPP support added.
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