* tests/input.at (AT_CHECK_UNUSED_VALUES): Remove. Instead, do

[bison.git] / NEWS

diff --git a/NEWS b/NEWS
index ac3587ebf4a0fcda0dfeda0a7c43c57e50379afd..e982759c2a2724a709ec6d64b4866a6a32d40857 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -1,7 +1,86 @@
 Bison News
 ----------
 
-Changes in the next version (not yet released):
+Changes in version 2.1a:
+
+* Bison now allows multiple %union declarations, and concatenates
+  their contents together.
+
+* 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 $$ and $5 in the first rule, and $3 in
+  the second ($1 is copied to $$ by the default rule).  This example
+  most likely contains three errors, and 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; }
+       ;
+
+  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 (); };
+
+  Mid-rule actions that use $$ cause the corresponding value to be
+  set, therefore the following action must use it.  The following rule
+  triggers a warning about $2.
+
+     exp: '1' { $$ = 1; } '+' exp { $$ = $1 + $4; };
+
+  The warning is intended to help catching lost values and memory leaks.
+  If a value is ignored, its associated memory typically is not reclaimed.
+
+* %destructor vs. YYABORT, YYACCEPT, and YYERROR.
+  Destructors are now called when user code invokes YYABORT, YYACCEPT,
+  and YYERROR, for all objects on the stack, other than objects
+  corresponding to the right-hand side of the current rule.
+
+* %expect, %expect-rr
+  Incorrect numbers of expected conflicts are now actual errors,
+  instead of warnings.
+
+* GLR, YACC parsers.
+  The %parse-params are available in the %destructor's (and the
+  experimental %printer's) as per the documentation.
+
+* Bison now warns if it finds a stray `$' 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
@@ -19,8 +98,6 @@ Changes in the next version (not yet released):
   behind on the stack.  Also, the start symbol is now destroyed after a
   successful parse.  In both cases, the behavior was formerly inconsistent.
 
-The following change was also in version 2.0a, 2005-05-22:
-
 * When generating verbose diagnostics, Bison-generated parsers no longer
   quote the literal strings associated with tokens.  For example, for
   a syntax error associated with '%token NUM "number"' they might
@@ -425,6 +502,8 @@ Changes in version 1.31, 2002-01-14:
   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.
 
@@ -619,8 +698,8 @@ 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.