* NEWS (2.5): Document fix for -Wno-KEY.

[bison.git] / NEWS

diff --git a/NEWS b/NEWS
index 99814004ff6b96128ad26592920e240da479cc2a..64a257043e6feab361b342d165c0729b56c2c5fe 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -62,6 +62,14 @@ Bison News
 
 * Changes in version 2.5 (????-??-??):
 
 
 * Changes in version 2.5 (????-??-??):
 

+** Grammar symbol names can now contain non-initial dashes:
+
+  Consistently with directives (such as %error-verbose) and with
+  %define variables (e.g. push-pull), grammar symbol names may contain
+  dashes in any position except the beginning.  This is a GNU
+  extension over POSIX Yacc.  Thus, use of this extension is reported
+  by -Wyacc and rejected in Yacc mode (--yacc).
+

 ** Named references:
 
   Historically, Yacc and Bison have supported positional references
 ** Named references:
 
   Historically, Yacc and Bison have supported positional references


@@ -108,27 +116,27 @@ Bison News
     %define lr.type ielr
     %define lr.type canonical-lr
 
     %define lr.type ielr
     %define lr.type canonical-lr
 

-  The default reduction optimization in the parser tables can also be
-  adjusted using `%define lr.default-reductions'.  See the documentation
-  for `%define lr.type' and `%define lr.default-reductions' in the
-  section `Bison Declaration Summary' in the Bison manual for the
-  details.
+  The default-reduction optimization in the parser tables can also be
+  adjusted using `%define lr.default-reductions'.  For details on both
+  of these features, see the new section `Tuning LR' in the Bison
+  manual.

 
   These features are experimental.  More user feedback will help to
   stabilize them.
 
 
   These features are experimental.  More user feedback will help to
   stabilize them.
 

-** LAC (lookahead correction) for syntax error handling:
+** LAC (Lookahead Correction) for syntax error handling:

 
   Canonical LR, IELR, and LALR can suffer from a couple of problems
   upon encountering a syntax error.  First, the parser might perform
   additional parser stack reductions before discovering the syntax
 
   Canonical LR, IELR, and LALR can suffer from a couple of problems
   upon encountering a syntax error.  First, the parser might perform
   additional parser stack reductions before discovering the syntax

-  error.  Such reductions perform user semantic actions that are
+  error.  Such reductions can perform user semantic actions that are

   unexpected because they are based on an invalid token, and they
   cause error recovery to begin in a different syntactic context than
   the one in which the invalid token was encountered.  Second, when
   unexpected because they are based on an invalid token, and they
   cause error recovery to begin in a different syntactic context than
   the one in which the invalid token was encountered.  Second, when

-  verbose error messages are enabled (with %error-verbose or `#define
-  YYERROR_VERBOSE'), the expected token list in the syntax error
-  message can both contain invalid tokens and omit valid tokens.
+  verbose error messages are enabled (with %error-verbose or the
+  obsolete `#define YYERROR_VERBOSE'), the expected token list in the
+  syntax error message can both contain invalid tokens and omit valid
+  tokens.

 
   The culprits for the above problems are %nonassoc, default
   reductions in inconsistent states, and parser state merging.  Thus,
 
   The culprits for the above problems are %nonassoc, default
   reductions in inconsistent states, and parser state merging.  Thus,


@@ -136,11 +144,11 @@ Bison News
   %nonassoc is used or if default reductions are enabled for
   inconsistent states.
 
   %nonassoc is used or if default reductions are enabled for
   inconsistent states.
 

-  LAC is a new mechanism within the parsing algorithm that completely
-  solves these problems for canonical LR, IELR, and LALR without
-  sacrificing %nonassoc, default reductions, or state mering.  When
-  LAC is in use, canonical LR and IELR behave exactly the same for
-  both syntactically acceptable and syntactically unacceptable input.
+  LAC is a new mechanism within the parsing algorithm that solves
+  these problems for canonical LR, IELR, and LALR without sacrificing
+  %nonassoc, default reductions, or state merging.  When LAC is in
+  use, canonical LR and IELR behave almost exactly the same for both
+  syntactically acceptable and syntactically unacceptable input.

   While LALR still does not support the full language-recognition
   power of canonical LR and IELR, LAC at least enables LALR's syntax
   error handling to correctly reflect LALR's language-recognition
   While LALR still does not support the full language-recognition
   power of canonical LR and IELR, LAC at least enables LALR's syntax
   error handling to correctly reflect LALR's language-recognition


@@ -151,20 +159,14 @@ Bison News
 
     %define parse.lac full
 
 
     %define parse.lac full
 

-  See the documentation for `%define parse.lac' in the section `Bison
-  Declaration Summary' in the Bison manual for additional details.
+  See the new section `LAC' in the Bison manual for additional
+  details including a few caveats.

 
   LAC is an experimental feature.  More user feedback will help to
   stabilize it.
 
 
   LAC is an experimental feature.  More user feedback will help to
   stabilize it.
 

-** Unrecognized %code qualifiers are now errors not warnings.
-

 ** %define improvements:
 
 ** %define improvements:
 

-*** Unrecognized variables are now errors not warnings.
-
-*** Multiple invocations for any variable is now an error not a warning.
-

 *** Can now be invoked via the command line:
 
   Each of these command-line options
 *** Can now be invoked via the command line:
 
   Each of these command-line options


@@ -210,13 +212,73 @@ Bison News
 
     %define api.push-pull push
 
 
     %define api.push-pull push
 

-** Grammar symbol names can now contain dashes:
+*** Unrecognized variables are now errors not warnings.
+
+*** Multiple invocations for any variable is now an error not a warning.
+
+** Unrecognized %code qualifiers are now errors not warnings.
+
+** Character literals not of length one:

 
 

-  Consistently with directives (such as %error-verbose) and variables
-  (e.g. push-pull), grammar symbol names may include dashes in any
-  position, similarly to periods and underscores.  This is GNU
-  extension over POSIX Yacc whose use is reported by -Wyacc, and
-  rejected in Yacc mode (--yacc).
+  Previously, Bison quietly converted all character literals to length
+  one.  For example, without warning, Bison interpreted the operators in
+  the following grammar to be the same token:
+
+    exp: exp '++'
+       | exp '+' exp
+       ;
+
+  Bison now warns when a character literal is not of length one.  In
+  some future release, Bison will start reporting an error instead.
+
+** Destructor calls fixed for lookaheads altered in semantic actions:
+
+  Previously for deterministic parsers in C, if a user semantic action
+  altered yychar, the parser in some cases used the old yychar value to
+  determine which destructor to call for the lookahead upon a syntax
+  error or upon parser return.  This bug has been fixed.
+
+** C++ parsers use YYRHSLOC:
+
+  Similarly to the C parsers, the C++ parsers now define the YYRHSLOC
+  macro and use it in the default YYLLOC_DEFAULT.  You are encouraged
+  to use it.  If, for instance, your location structure has "first"
+  and "last" members, instead of
+
+      # define YYLLOC_DEFAULT(Current, Rhs, N)                             \
+        do                                                                 \
+          if (N)                                                           \
+            {                                                              \
+              (Current).first = (Rhs)[1].location.first;                   \
+              (Current).last  = (Rhs)[N].location.last;                    \
+            }                                                              \
+          else                                                             \
+            {                                                              \
+              (Current).first = (Current).last = (Rhs)[0].location.last;   \
+            }                                                              \
+        while (false)
+
+  use:
+
+      # define YYLLOC_DEFAULT(Current, Rhs, N)                             \
+        do                                                                 \
+          if (N)                                                           \
+            {                                                              \
+              (Current).first = YYRHSLOC (Rhs, 1).first;                   \
+              (Current).last  = YYRHSLOC (Rhs, N).last;                    \
+            }                                                              \
+          else                                                             \
+            {                                                              \
+              (Current).first = (Current).last = YYRHSLOC (Rhs, 0).last;   \
+            }                                                              \
+        while (false)
+
+** YYLLOC_DEFAULT in C++:
+
+  The default implementation of YYLLOC_DEFAULT used to be issued in
+  the header file.  It is now output in the implementation file, after
+  the user %code sections so that its #ifndef guard does not try to
+  override the user's YYLLOC_DEFAULT if provided.

 
 ** YYFAIL now produces warnings and Java parsers no longer implement it:
 
 
 ** YYFAIL now produces warnings and Java parsers no longer implement it:
 


@@ -250,26 +312,13 @@ Bison News
   about a missing semicolon where it did not before.  Future releases of
   Bison will cease to append semicolons entirely.
 
   about a missing semicolon where it did not before.  Future releases of
   Bison will cease to append semicolons entirely.
 

-** Character literals not of length one:
-
-  Previously, Bison quietly converted all character literals to length
-  one.  For example, without warning, Bison interpreted the operators in
-  the following grammar to be the same token:
-
-    exp: exp '++'
-       | exp '+' exp
-       ;
-
-  Bison now warns when a character literal is not of length one.  In
-  some future release, Bison will start reporting an error instead.
-

 ** Verbose syntax error message fixes:
 
 ** Verbose syntax error message fixes:
 

-  When %error-verbose or `#define YYERROR_VERBOSE' is specified,
-  syntax error messages produced by the generated parser include the
-  unexpected token as well as a list of expected tokens.  The effect
-  of %nonassoc on these verbose messages has been corrected in two
-  ways, but a complete fix requires LAC, described above:
+  When %error-verbose or the obsolete `#define YYERROR_VERBOSE' is
+  specified, syntax error messages produced by the generated parser
+  include the unexpected token as well as a list of expected tokens.
+  The effect of %nonassoc on these verbose messages has been corrected
+  in two ways, but a more complete fix requires LAC, described above:

 
 *** When %nonassoc is used, there can exist parser states that accept no
     tokens, and so the parser does not always require a lookahead token
 
 *** When %nonassoc is used, there can exist parser states that accept no
     tokens, and so the parser does not always require a lookahead token


@@ -301,54 +350,23 @@ Bison News
     canonical LR.  However, LAC is still experimental and is disabled
     by default.
 
     canonical LR.  However, LAC is still experimental and is disabled
     by default.
 

-** Destructor calls fixed for lookaheads altered in semantic actions:
-
-  Previously for deterministic parsers in C, if a user semantic action
-  altered yychar, the parser in some cases used the old yychar value to
-  determine which destructor to call for the lookahead upon a syntax
-  error or upon parser return.  This bug has been fixed.
+** Java skeleton fixes:

 
 

-** C++ parsers use YYRHSLOC:
+*** A location handling bug has been fixed.

 
 

-  Similarly to the C parsers, the C++ parsers now define the YYRHSLOC
-  macro and use it in the default YYLLOC_DEFAULT.  You are encouraged
-  to use it.  If, for instance, your location structure has "first"
-  and "last" members, instead of
+*** The top element of each of the value stack and location stack is now
+    cleared when popped so that it can be garbage collected.

 
 

-      # define YYLLOC_DEFAULT(Current, Rhs, N)                             \
-        do                                                                 \
-          if (N)                                                           \
-            {                                                              \
-              (Current).first = (Rhs)[1].location.first;                   \
-              (Current).last  = (Rhs)[N].location.last;                    \
-            }                                                              \
-          else                                                             \
-            {                                                              \
-              (Current).first = (Current).last = (Rhs)[0].location.last;   \
-            }                                                              \
-        while (false)
+*** Parser traces now print the top element of the stack.

 
 

-  use:
+** -W/--warnings fixes:

 
 

-      # define YYLLOC_DEFAULT(Current, Rhs, N)                             \
-        do                                                                 \
-          if (N)                                                           \
-            {                                                              \
-              (Current).first = YYRHSLOC (Rhs, 1).first;                   \
-              (Current).last  = YYRHSLOC (Rhs, N).last;                    \
-            }                                                              \
-          else                                                             \
-            {                                                              \
-              (Current).first = (Current).last = YYRHSLOC (Rhs, 0).last;   \
-            }                                                              \
-        while (false)
+*** Bison now properly recognizes the "no-" versions of categories:

 
 

-** YYLLOC_DEFAULT in C++:
+  For example, given the following command line, Bison now enables all
+  warnings except warnings for incompatibilities with POSIX Yacc:

 
 

-  The default implementation of YYLLOC_DEFAULT used to be issued in
-  the header file.  It is now output in the implementation file, after
-  the user %code sections so that its #ifndef guard does not try to
-  override the user's YYLLOC_DEFAULT if provided.
+    bison -Wall,no-yacc gram.y

 
 * Changes in version 2.4.3 (2010-08-05):
 
 
 * Changes in version 2.4.3 (2010-08-05):
 


@@ -1511,9 +1529,7 @@ End:
 
 -----
 
 
 -----
 

-Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
-2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation,
-Inc.
+Copyright (C) 1995-2011 Free Software Foundation, Inc.

 
 This file is part of Bison, the GNU Parser Generator.
 
 
 This file is part of Bison, the GNU Parser Generator.