X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/32b5b719e4ed6a09bba1078c49a27ab8514823cd..765f22f0f4d50a2b1a4fb020cd8f13c1f9c6763a:/NEWS

diff --git a/NEWS b/NEWS
index a84a20ef..b4760b74 100644
--- a/NEWS
+++ b/NEWS
@@ -1,31 +1,67 @@
 Bison News
 ----------
 
-Changes in version 2.1a:
+Changes in version 2.1a, 2006-02-13:
 
-* GLR, C++ LALR(1) parsers.
-  These parser skeletons are now distributed with the same special
-  license exception that the C LALR(1) parser skeleton has had since
-  Bison 1.24.  Hence the FSF imposes no copyright restriction on the
-  output of Bison when it is generating such parsers.
+* 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 %destructor's (and the
-  experimental %printer's) as per the documentation.
+  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"
-  To specify that the grammar file depends on features implemented in
-  Bison version VERSION or higher.
+  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 where defined as free form enums and cpp macros.  YYSTYPE
-  was defined as a free form union.  Both 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.
 
@@ -41,6 +77,8 @@ Changes in version 2.1a:
 
 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
   language is still English.  For details, please see the new
@@ -657,8 +695,8 @@ End:
 
 -----
 
-Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
-Free Software Foundation, Inc.
+Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
+2004, 2005, 2006 Free Software Foundation, Inc.
 
 This file is part of Bison, the GNU Compiler Compiler.