Renamed from "Invalid \$n", to work around an Autoconf bug with dollar

[bison.git] / NEWS

diff --git a/NEWS b/NEWS
index 0407aad5ab66fde651f19972293fae05dbafe02d..a3130f93d551a0d29e136d4b483930a0cbe3df84 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -1,111 +1,163 @@
 Bison News
 ----------
 
 Bison News
 ----------
 

-Changes in version 1.75f, 2002-12-28:
+Changes in version 2.0, 2004-12-25:

 
 

-* In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error
-  locations too.  This fixes bugs in error-location computation.
+* Possibly-incompatible changes

 
 

-* Bison now uses a Yacc-style format for conflict reports, e.g.,
-  "conflicts: 2 shift/reduce, 1 reduce/reduce".
+  - 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.

 
 

-* Bison now warns if it detects conflicting outputs to the same file,
-  e.g., it generates a warning for "bison -d -o foo.h foo.y" since
-  that command outputs both code and header to foo.h.
+  - 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.
+
+  - NUL bytes are no longer allowed in Bison string literals, unfortunately.
+
+* New features

 
 

-Changes in version 1.75e, 2002-12-24:
+  - GLR grammars now support locations.

 
 

-* If the user does not define YYSTYPE as a macro, Bison now declares it
-  using typedef instead of defining it as a macro.  POSIX requires this.
-  For consistency, YYLTYPE is also declared instead of defined.
+  - New directive: %initial-action.
+    This directive allows the user to run arbitrary code (including
+    initializing @$) from yyparse before parsing starts.

 
 

-* %union directives can now have a tag before the `{', e.g., the
-  directive `%union foo {...}' now generates the C code
-  `typedef union foo { ... } YYSTYPE;'; this is for Yacc compatibility.
-  The default union tag is `YYSTYPE', for compatibility with Solaris 9 Yacc.
-  For consistency, YYLTYPE's struct tag is now `YYLTYPE' instead of `yyltype'.
+  - A new directive "%expect-rr N" specifies the expected number of
+    reduce/reduce conflicts in GLR parsers.

 
 

-* `yystype' and `yyltype' are now obsolescent macros instead of being
-  typedefs or tags; they are no longer documented and will be
-  withdrawn in a future release.
+  - %token numbers can now be hexadecimal integers, e.g., `%token FOO 0x12d'.
+    This is a GNU extension.

 
 

-* References to the experimental %lex-param and %parse-param directives
-  have been temporarily removed from the manual, since we don't want
-  users to rely upon these features quite yet.
+  - The option `--report=lookahead' was changed to `--report=look-ahead'.
+    The old spelling still works, but is not documented and will be
+    removed.

 
 

-Changes in version 1.75d, 2002-12-13:
+  - Experimental %destructor support has been added to lalr1.cc.

 
 

-* Semicolons are once again optional at the end of grammar rules.
-  This reverts to the behavior of Bison 1.33 and earlier, and improves
-  compatibility with Yacc.
+  - New configure option --disable-yacc, to disable installation of the
+    yacc command and -ly library introduced in 1.875 for POSIX conformance.

 
 

-* Type clashes now generate warnings, not errors.
+* Bug fixes

 
 

-* Yacc command and library now available
-  The Bison distribution now installs a yacc command, as POSIX requires.
-  Also, Bison now installs a small library liby.a containing
-  implementations of Yacc-compatible yyerror and main functions.
-  This library is normally not useful, but POSIX requires it.
+  - 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.

 
 

-* %lex-param, %parse-param
-  These now take just one operand, not two.
+  - Within Bison itself, numbers (e.g., goto numbers) are no longer
+    arbitrarily limited to 16-bit counts.

 
 

-* The documentation now emphasizes that yylex and yyerror must be
-  declared before use.  C99 requires this.
+  - Semicolons are now allowed before "|" in grammar rules, as POSIX requires.
+\f
+Changes in version 1.875, 2003-01-01:

 
 * The documentation license has been upgraded to version 1.2
   of the GNU Free Documentation License.
 
 
 * The documentation license has been upgraded to version 1.2
   of the GNU Free Documentation License.
 

-Changes in version 1.75c, 2002-11-25:
+* syntax error processing
+
+  - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error
+    locations too.  This fixes bugs in error-location computation.
+
+  - %destructor
+    It is now possible to reclaim the memory associated to symbols
+    discarded during error recovery.  This feature is still experimental.
+
+  - %error-verbose
+    This new directive is preferred over YYERROR_VERBOSE.
+
+  - #defining yyerror to steal internal variables is discouraged.
+    It is not guaranteed to work forever.
+
+* POSIX conformance

 
 

-* "parse error" -> "syntax error"
-  Bison now uniformly uses the term "syntax error"; formerly, the code
-  and manual sometimes used the term "parse error" instead.  POSIX
-  requires "syntax error" in diagnostics, and it was thought better to
-  be consistent.
+  - Semicolons are once again optional at the end of grammar rules.
+    This reverts to the behavior of Bison 1.33 and earlier, and improves
+    compatibility with Yacc.

 
 

-* "parsing stack overflow..." -> "parser stack overflow"
-  GLR parsers now report "parser stack overflow" as per the Bison manual.
+  - `parse error' -> `syntax error'
+    Bison now uniformly uses the term `syntax error'; formerly, the code
+    and manual sometimes used the term `parse error' instead.  POSIX
+    requires `syntax error' in diagnostics, and it was thought better to
+    be consistent.

 
 

-* GLR and inline
-  Users of Bison have to decide how they handle the portability of the
-  C keyword `inline'.
+  - The documentation now emphasizes that yylex and yyerror must be
+    declared before use.  C99 requires this.

 
 

-Changes in version 1.75b, 2002-11-13:
+  - Bison now parses C99 lexical constructs like UCNs and
+    backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires.

 
 

-* %destructor
-  It is now possible to reclaim the memory associated to symbols
-  discarded during error recovery.  This feature is still experimental.
+  - File names are properly escaped in C output.  E.g., foo\bar.y is
+    output as "foo\\bar.y".

 
 

-* Bison now parses C99 lexical constructs like UCNs and
-  backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires.
+  - Yacc command and library now available
+    The Bison distribution now installs a `yacc' command, as POSIX requires.
+    Also, Bison now installs a small library liby.a containing
+    implementations of Yacc-compatible yyerror and main functions.
+    This library is normally not useful, but POSIX requires it.

 
 

-* --no-line works properly.
+  - Type clashes now generate warnings, not errors.

 
 

-* %error-verbose
-  This new directive is preferred over YYERROR_VERBOSE.
+  - If the user does not define YYSTYPE as a macro, Bison now declares it
+    using typedef instead of defining it as a macro.
+    For consistency, YYLTYPE is also declared instead of defined.

 
 

-* %lex-param, %parse-param
-  These new directives are preferred over PARSE_PARAM and LEX_PARAM.
-  In addition, they provide a means for yyerror to remain pure, and
-  to access to the current location.
+* Other compatibility issues

 
 

-  #defining yyerror to steal internal variables is strongly
-  discouraged.  It is not guaranteed to work for ever.
+  - %union directives can now have a tag before the `{', e.g., the
+    directive `%union foo {...}' now generates the C code
+    `typedef union foo { ... } YYSTYPE;'; this is for Yacc compatibility.
+    The default union tag is `YYSTYPE', for compatibility with Solaris 9 Yacc.
+    For consistency, YYLTYPE's struct tag is now `YYLTYPE' not `yyltype'.
+    This is for compatibility with both Yacc and Bison 1.35.

 
 

-* #line
-  Bison now recognizes #line in its input, and forwards them.
+  - `;' is output before the terminating `}' of an action, for
+    compatibility with Bison 1.35.

 
 

-* #line
-  File names are properly escaped. E.g. foo\bar.y give #line 123 "foo\\bar.y".
+  - Bison now uses a Yacc-style format for conflict reports, e.g.,
+    `conflicts: 2 shift/reduce, 1 reduce/reduce'.

 
 

-Changes in version 1.75a, 2002-10-24:
+  - `yystype' and `yyltype' are now obsolescent macros instead of being
+    typedefs or tags; they are no longer documented and are planned to be
+    withdrawn in a future release.
+
+* GLR parser notes
+
+  - GLR and inline
+    Users of Bison have to decide how they handle the portability of the
+    C keyword `inline'.
+
+  - `parsing stack overflow...' -> `parser stack overflow'
+    GLR parsers now report `parser stack overflow' as per the Bison manual.
+
+* Bison now warns if it detects conflicting outputs to the same file,
+  e.g., it generates a warning for `bison -d -o foo.h foo.y' since
+  that command outputs both code and header to foo.h.
+
+* #line in output files
+  - --no-line works properly.

 
 * Bison can no longer be built by a K&R C compiler; it requires C89 or
   later to be built.  This change originally took place a few versions
   ago, but nobody noticed until we recently asked someone to try
   building Bison with a K&R C compiler.
 
 * Bison can no longer be built by a K&R C compiler; it requires C89 or
   later to be built.  This change originally took place a few versions
   ago, but nobody noticed until we recently asked someone to try
   building Bison with a K&R C compiler.

-
+\f

 Changes in version 1.75, 2002-10-14:
 
 * Bison should now work on 64-bit hosts.
 Changes in version 1.75, 2002-10-14:
 
 * Bison should now work on 64-bit hosts.


@@ -136,7 +188,7 @@ Changes in version 1.75, 2002-10-14:
 
   was incorrectly rejected: $1 is defined in the second mid-rule
   action, and is equal to the $$ of the first mid-rule action.
 
   was incorrectly rejected: $1 is defined in the second mid-rule
   action, and is equal to the $$ of the first mid-rule action.

-
+\f

 Changes in version 1.50, 2002-10-04:
 
 * GLR parsing
 Changes in version 1.50, 2002-10-04:
 
 * GLR parsing


@@ -183,7 +235,8 @@ Changes in version 1.50, 2002-10-04:
   allowed some non-error action other than a default reduction on the
   error token.  The new behavior has long been the documented behavior,
   and has long been required by POSIX.  For more details, please see
   allowed some non-error action other than a default reduction on the
   error token.  The new behavior has long been the documented behavior,
   and has long been required by POSIX.  For more details, please see

-  <http://mail.gnu.org/pipermail/bug-bison/2002-May/001452.html>.
+  Paul Eggert, "Reductions during Bison error handling" (2002-05-20)
+  <http://lists.gnu.org/archive/html/bug-bison/2002-05/msg00038.html>.

 
 * Traces
   Popped tokens and nonterminals are now reported.
 
 * Traces
   Popped tokens and nonterminals are now reported.


@@ -258,8 +311,8 @@ Changes in version 1.50, 2002-10-04:
   produces additional information:
   - itemset
     complete the core item sets with their closure
   produces additional information:
   - itemset
     complete the core item sets with their closure

-  - lookahead
-    explicitly associate lookaheads to items
+  - lookahead [changed to `look-ahead' in 1.875e and later]
+    explicitly associate look-ahead tokens to items

   - solved
     describe shift/reduce conflicts solving.
     Bison used to systematically output this information on top of
   - solved
     describe shift/reduce conflicts solving.
     Bison used to systematically output this information on top of


@@ -540,8 +593,8 @@ End:
 
 -----
 
 
 -----
 

-Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002 Free
-Software Foundation, Inc.
+Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
+Free Software Foundation, Inc.

 
 This file is part of Bison, the GNU Compiler Compiler.
 
 
 This file is part of Bison, the GNU Compiler Compiler.