* NEWS: Improve wording for unused-value warnings.

[bison.git] / NEWS

diff --git a/NEWS b/NEWS
index 44b657902f92aa1dc90a806557361998154bcb59..176ce6f27df09ec78e2954172852b64eeade8674 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -1,73 +1,158 @@
 Bison News
 ----------
 
 Bison News
 ----------
 

-Changes in version 1.875f:
+Changes in version 2.1a:

 
 

-* Bison-generated parsers no longer default to using the alloca function
-  (when available) to extend the parser stack, due to widespread
-  problems in unchecked stack-overflow detection.  You can "#define
-  YYSTACK_USE_ALLOCA 1" to use alloca anyway, but please read the
-  manual to determine safe values for YYMAXDEPTH in that case.
+* New warning: unused values
+  Typed right-hand side symbols whose value are not used are reported.
+  For instance:

 
 

-Changes in version 1.875e, 2004-12-10:
+     exp: exp "?" exp ":" exp { $$ = $1 ? $1 : $3; }
+       | exp "+" exp
+       ;

 
 

-* New directive: %initial-action.
-  This directive allows the user to run arbitrary code (including
-  initializing @$) from yyparse before parsing starts.
+  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:

 
 

-* The option `--report=lookahead' was changed to `--report=look-ahead'.
-  The old spelling still works, but is not documented and will be
-  removed.
+     exp: exp "?" exp ":" exp { $$ = $1 ? $3 : $5; }
+       | exp "+" exp         { $$ = $1 + $3; }
+       ;

 
 

-* Error token location.
-  During error recovery, the location of the syntax error is updated
-  to cover the whole sequence covered by the error token: it includes
-  the shifted symbols thrown away during the first part of the error
-  recovery, and the lookahead rejected during the second part.
+  However, if the original actions were really intended, the warnings
+  can be suppressed by letting Bison believe the values are used, e.g.:

 
 

-* Goto numbers are no longer arbitrarily limited to 16-bit counts.
+     exp: exp "?" exp ":" exp { $$ = $1 ? $1 : $3; (void) $5; }
+       | exp "+" exp         { $$ = $1; (void) $3; }
+       ;

 
 

-Changes in version 1.875d, 2004-05-21:
+  The warning is intended to help catching lost values and memory leaks.
+  If a value is ignored, its associated memory typically is not reclaimed.

 
 

-* Unescaped newlines are no longer allowed in character constants or
-  string literals.  They were never portable, and GCC 3.4.0 has
-  dropped support for them.  Better diagnostics are now generated if
-  forget a closing quote.
+* %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.

 
 

-* NUL bytes are no longer allowed in Bison string literals, unfortunately.
+* %expect, %expect-rr
+  Incorrect numbers of expected conflicts are now actual errors,
+  instead of warnings.

 
 

-* %token numbers can now be hexadecimal integers, e.g., `%token FOO 0x12d'.
-  This is a GNU extension.
+* GLR, YACC parsers.
+  The %parse-params are available in the %destructor's (and the
+  experimental %printer's) as per the documentation.

 
 

-* A new directive "%expect-rr N" specifies the expected number of
-  reduce/reduce conflicts in GLR parsers.
+* Bison now warns if it finds a stray `$' or `@' in an action.

 
 

-* Experimental %destructor support has been added to lalr1.cc.
+* %require "VERSION"
+  To specify that the grammar file depends on features implemented in
+  Bison version VERSION or higher.

 
 

-Changes in version 1.875c, 2003-08-25:
+* 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.

 
 

-  (Just bug fixes.)
+  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.

 
 

-Changes in version 1.875b, 2003-06-17:
+  If you wish to update, then make sure older version of Bison will
+  fail using `%require "2.1a"'.

 
 

-* GLR grammars now support locations.
+* DJGPP support added.

 
 

-* Semicolon changes:
-  - Semicolons are now allowed before "|" in grammar rules, as POSIX requires.
-  - Stray semicolons are no longer allowed at the start of a grammar.
-  - Semicolons are now required after in-grammar declarations.
+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
+  Internationalization section of the Bison manual.  Software
+  distributors should also see the new PACKAGING file.  Thanks to
+  Bruno Haible for this new feature.
+
+* 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
+  a syntax error associated with '%token NUM "number"' they might
+  print 'syntax error, unexpected number' instead of 'syntax error,
+  unexpected "number"'.
+
+Changes in version 2.0, 2004-12-25:
+
+* Possibly-incompatible changes
+
+  - Bison-generated parsers no longer default to using the alloca function
+    (when available) to extend the parser stack, due to widespread
+    problems in unchecked stack-overflow detection.  You can "#define
+    YYSTACK_USE_ALLOCA 1" to require the use of alloca, but please read
+    the manual to determine safe values for YYMAXDEPTH in that case.
+
+  - Error token location.
+    During error recovery, the location of the syntax error is updated
+    to cover the whole sequence covered by the error token: it includes
+    the shifted symbols thrown away during the first part of the error
+    recovery, and the lookahead rejected during the second part.
+
+  - Semicolon changes:
+    . Stray semicolons are no longer allowed at the start of a grammar.
+    . Semicolons are now required after in-grammar declarations.
+
+  - Unescaped newlines are no longer allowed in character constants or
+    string literals.  They were never portable, and GCC 3.4.0 has
+    dropped support for them.  Better diagnostics are now generated if
+    forget a closing quote.

 
 

-Changes in version 1.875a, 2003-02-01:
+  - NUL bytes are no longer allowed in Bison string literals, unfortunately.

 
 

-* For now, %expect-count violations are now just warnings, not errors.
-  This is for compatibility with Bison 1.75 and earlier (when there are
-  reduce/reduce conflicts) and with Bison 1.30 and earlier (when there
-  are too many or too few shift/reduce conflicts).  However, in future
-  versions of Bison we plan to improve the %expect machinery so that
-  these violations will become errors again.
+* New features

 
 

-* New configure option --disable-yacc, to disable installation of the
-  yacc command and -ly library introduced in 1.875 for POSIX conformance.
+  - GLR grammars now support locations.
+
+  - New directive: %initial-action.
+    This directive allows the user to run arbitrary code (including
+    initializing @$) from yyparse before parsing starts.
+
+  - A new directive "%expect-rr N" specifies the expected number of
+    reduce/reduce conflicts in GLR parsers.
+
+  - %token numbers can now be hexadecimal integers, e.g., `%token FOO 0x12d'.
+    This is a GNU extension.
+
+  - The option `--report=lookahead' was changed to `--report=look-ahead'.
+    The old spelling still works, but is not documented and will be
+    removed.
+
+  - Experimental %destructor support has been added to lalr1.cc.
+
+  - New configure option --disable-yacc, to disable installation of the
+    yacc command and -ly library introduced in 1.875 for POSIX conformance.
+
+* Bug fixes
+
+  - For now, %expect-count violations are now just warnings, not errors.
+    This is for compatibility with Bison 1.75 and earlier (when there are
+    reduce/reduce conflicts) and with Bison 1.30 and earlier (when there
+    are too many or too few shift/reduce conflicts).  However, in future
+    versions of Bison we plan to improve the %expect machinery so that
+    these violations will become errors again.
+
+  - Within Bison itself, numbers (e.g., goto numbers) are no longer
+    arbitrarily limited to 16-bit counts.
+
+  - Semicolons are now allowed before "|" in grammar rules, as POSIX requires.

 \f
 Changes in version 1.875, 2003-01-01:
 
 \f
 Changes in version 1.875, 2003-01-01:
 


@@ -403,6 +488,8 @@ Changes in version 1.31, 2002-01-14:
   alloca is used only when compiled with GCC, to avoid portability
   problems as on AIX.
 
   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.
 
 * When the generated parser lacks debugging code, YYDEBUG is now 0
   (as POSIX requires) instead of being undefined.
 


@@ -597,7 +684,7 @@ End:
 
 -----
 
 
 -----
 

-Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
+Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005

 Free Software Foundation, Inc.
 
 This file is part of Bison, the GNU Compiler Compiler.
 Free Software Foundation, Inc.
 
 This file is part of Bison, the GNU Compiler Compiler.


@@ -614,5 +701,5 @@ GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 along with autoconf; see the file COPYING.  If not, write to
 
 You should have received a copy of the GNU General Public License
 along with autoconf; see the file COPYING.  If not, write to

-the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
-Boston, MA 02111-1307, USA.
+the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+Boston, MA 02110-1301, USA.