X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/0410a6e0ccfe1bf6fd917a4cc06d4bdfdd980b8d..2073ce56f5bdad7ac39fe5a734556dbf1e79cd24:/NEWS

diff --git a/NEWS b/NEWS
index 02b22d09..784efeb7 100644
--- a/NEWS
+++ b/NEWS
@@ -1,7 +1,83 @@
 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 $$ and $5 in the first rule, and $3 in
+  the second ($1 is copied to $$ 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
@@ -10,7 +86,14 @@ Changes in the next version (not yet released):
   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
@@ -416,6 +499,8 @@ 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.