Bison News
----------
-Changes in the next version (not yet released):
+Changes in version 2.1a:
+
+* New warning: unused values
+ Typed right-hand side symbols whose value are not used are reported.
+ For instance:
+
+ exp: exp "?" exp ":" exp { $$ = $1 ? $1 : $3; }
+ | exp "+" exp
+ ;
+
+ will trigger a warning about $5 of the first rule, and $3 in the
+ second ($1 is copied to $$ by the default rule). This example
+ most likely contains two errors, and should be rewritten as:
+
+ exp: exp "?" exp ":" exp { $$ = $1 ? $3 : $5; }
+ | exp "+" exp { $$ = $1 + $3; }
+ ;
+
+ However, if the original actions were really intended, 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) $3; }
+ ;
+
+ The warning is intended to help catching lost values and memory leaks.
+ If a value is ignored, its associated memory typically is not reclaimed.
+
+* %destructor vs. YYABORT, YYACCEPT, and YYERROR.
+ Destructors are now called when user code invokes YYABORT, YYACCEPT,
+ and YYERROR, for all objects on the stack, other than objects
+ corresponding to the right-hand side of the current rule.
+
+* %expect, %expect-rr
+ Incorrect numbers of expected conflicts are now actual errors,
+ instead of warnings.
+
+* GLR, YACC parsers.
+ The %parse-params are available in the %destructor's (and the
+ experimental %printer's) as per the documentation.
+
+* Bison now warns if it finds a stray `$' or `@' in an action.
+
+* %require "VERSION"
+ To specify 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 "2.1a"'.
+
+* DJGPP support added.
+
+Changes in version 2.1, 2005-09-16:
+
+* The C++ lalr1.cc skeleton supports %lex-param.
* Bison-generated parsers now support the translation of diagnostics like
"syntax error" into languages other than English. The default
distributors should also see the new PACKAGING file. Thanks to
Bruno Haible for this new feature.
-The following change was also in version 2.0a, 2005-05-22:
+* Wording in the Bison-generated parsers has been changed slightly to
+ simplify translation. In particular, the message "memory exhausted"
+ has replaced "parser stack overflow", as the old message was not
+ always accurate for modern Bison-generated parsers.
+
+* Destructors are now called when the parser aborts, for all symbols left
+ behind on the stack. Also, the start symbol is now destroyed after a
+ successful parse. In both cases, the behavior was formerly inconsistent.
* When generating verbose diagnostics, Bison-generated parsers no longer
quote the literal strings associated with tokens. For example, for
alloca is used only when compiled with GCC, to avoid portability
problems as on AIX.
+* yyparse now returns 2 if memory is exhausted; formerly it dumped core.
+
* When the generated parser lacks debugging code, YYDEBUG is now 0
(as POSIX requires) instead of being undefined.
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