c++: clean up the handling of empty symbols

[bison.git] / NEWS

diff --git a/NEWS b/NEWS
index 5b9a6e803a81838b73fc9793eb057773fee10caa..490e89ed5c9cbe1ae340d45b924c62da22c587a8 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -2,15 +2,114 @@ GNU Bison NEWS
 
 * Noteworthy changes in release ?.? (????-??-??) [?]
 
 
 * Noteworthy changes in release ?.? (????-??-??) [?]
 

-** WARNING: Future backward-incompatibilities!
+** Bug fixes
+
+*** Named %union support
+
+  Bison 3.0 introduced a regression on named %union such as
+
+    %union foo { int ival; };
+
+  The possibility to use a name was introduced ``for Yacc compatibility''.
+  It is however not required by POSIX Yacc, and its usefulness is not clear.
+
+*** %define api.value.type union with %defines
+
+  The yacc.c and glr.c parsers were broken when %defines was used
+  together with "%define api.value.type union".

 
 

-  Bison will stop adding a semicolon at the end of the actions (as announced
-  in the release 2.5):
+*** Redeclarations are reported in proper order

 
 

-    foo.y:2.22: warning: a ';' might be needed at the end of action code
-     exp: "num" { $$ = $1 }
-                          ^
-    foo.y:2.22:     future versions of Bison will not add the ';'
+  On
+
+    %token FOO "foo"
+    %printer {} "foo"
+    %printer {} FOO
+
+  bison used to report:
+
+    /tmp/foo.yy:2.10-11: error: %printer redeclaration for FOO
+     %printer {} "foo"
+              ^^
+    /tmp/foo.yy:3.10-11:     previous declaration
+     %printer {} FOO
+              ^^
+
+  Now, the "previous" declaration is always the first one.
+
+
+** Documentation
+
+  Bison now installs various files in its docdir (which defaults to
+  '/usr/local/share/doc/bison'), including the three fully blown examples
+  extracted from the documentation:
+
+   - rpcalc
+     Reverse polish calculator, a simple introductory example.
+   - mfcalc
+     Multi-function Calc, a calculator with memory and functions and located
+     error messages.
+   - calc++
+     a calculator in C++ using variant support and token constructors.
+
+* Noteworthy changes in release 3.0.2 (2013-12-05) [stable]
+
+** Bug fixes
+
+*** Generated source files when errors are reported
+
+  When warnings are issued and -Werror is set, bison would still generate
+  the source files (*.c, *.h...).  As a consequence, some runs of "make"
+  could fail the first time, but not the second (as the files were generated
+  anyway).
+
+  This is fixed: bison no longer generates this source files, but, of
+  course, still produces the various reports (*.output, *.xml, etc.).
+
+*** %empty is used in reports
+
+  Empty right-hand sides are denoted by '%empty' in all the reports (text,
+  dot, XML and formats derived from it).
+
+*** YYERROR and variants
+
+  When C++ variant support is enabled, an error triggered via YYERROR, but
+  not caught via error recovery, resulted in a double deletion.
+
+* Noteworthy changes in release 3.0.1 (2013-11-12) [stable]
+
+** Bug fixes
+
+*** Errors in caret diagnostics
+
+  On some platforms, some errors could result in endless diagnostics.
+
+*** Fixes of the -Werror option
+
+  Options such as "-Werror -Wno-error=foo" were still turning "foo"
+  diagnostics into errors instead of warnings.  This is fixed.
+
+  Actually, for consistency with GCC, "-Wno-error=foo -Werror" now also
+  leaves "foo" diagnostics as warnings.  Similarly, with "-Werror=foo
+  -Wno-error", "foo" diagnostics are now errors.
+
+*** GLR Predicates
+
+  As demonstrated in the documentation, one can now leave spaces between
+  "%?" and its "{".
+
+*** Installation
+
+  The yacc.1 man page is no longer installed if --disable-yacc was
+  specified.
+
+*** Fixes in the test suite
+
+  Bugs and portability issues.
+
+* Noteworthy changes in release 3.0 (2013-07-25) [stable]
+
+** WARNING: Future backward-incompatibilities!

 
   Like other GNU packages, Bison will start using some of the C99 features
   for its own code, especially the definition of variables after statements.
 
   Like other GNU packages, Bison will start using some of the C99 features
   for its own code, especially the definition of variables after statements.


@@ -28,6 +127,29 @@ GNU Bison NEWS
   Support for YYLEX_PARAM and YYPARSE_PARAM is removed (deprecated in Bison
   1.875): use %lex-param, %parse-param, or %param.
 
   Support for YYLEX_PARAM and YYPARSE_PARAM is removed (deprecated in Bison
   1.875): use %lex-param, %parse-param, or %param.
 

+  Missing semicolons at the end of actions are no longer added (as announced
+  in the release 2.5).
+
+*** Use of YACC='bison -y'
+
+  TL;DR: With Autoconf <= 2.69, pass -Wno-yacc to (AM_)YFLAGS if you use
+  Bison extensions.
+
+  Traditional Yacc generates 'y.tab.c' whatever the name of the input file.
+  Therefore Makefiles written for Yacc expect 'y.tab.c' (and possibly
+  'y.tab.h' and 'y.outout') to be generated from 'foo.y'.
+
+  To this end, for ages, AC_PROG_YACC, Autoconf's macro to look for an
+  implementation of Yacc, was using Bison as 'bison -y'.  While it does
+  ensure compatible output file names, it also enables warnings for
+  incompatibilities with POSIX Yacc.  In other words, 'bison -y' triggers
+  warnings for Bison extensions.
+
+  Autoconf 2.70+ fixes this incompatibility by using YACC='bison -o y.tab.c'
+  (which also generates 'y.tab.h' and 'y.output' when needed).
+  Alternatively, disable Yacc warnings by passing '-Wno-yacc' to your Yacc
+  flags (YFLAGS, or AM_YFLAGS with Automake).
+

 ** Bug fixes
 
 *** The epilogue is no longer affected by internal #defines (glr.c)
 ** Bug fixes
 
 *** The epilogue is no longer affected by internal #defines (glr.c)


@@ -39,7 +161,7 @@ GNU Bison NEWS
 
     int yylex (YYSTYPE *yylval);
 
 
     int yylex (YYSTYPE *yylval);
 

-  This is has been fixed: yylval, yynerrs, yychar, and yylloc are now valid
+  This is fixed: yylval, yynerrs, yychar, and yylloc are now valid

   identifiers for user-provided variables.
 
 *** stdio.h is no longer needed when locations are enabled (yacc.c)
   identifiers for user-provided variables.
 
 *** stdio.h is no longer needed when locations are enabled (yacc.c)


@@ -47,6 +169,8 @@ GNU Bison NEWS
   Changes in Bison 2.7 introduced a dependency on FILE and fprintf when
   locations are enabled.  This is fixed.
 
   Changes in Bison 2.7 introduced a dependency on FILE and fprintf when
   locations are enabled.  This is fixed.
 

+*** Warnings about useless %pure-parser/%define api.pure are restored
+

 ** Diagnostics reported by Bison
 
   Most of these features were contributed by Théophile Ranquet and Victor
 ** Diagnostics reported by Bison
 
   Most of these features were contributed by Théophile Ranquet and Victor


@@ -58,6 +182,29 @@ GNU Bison NEWS
   activated by default.  The old format can still be used by invoking Bison
   with -fno-caret (or -fnone).
 
   activated by default.  The old format can still be used by invoking Bison
   with -fno-caret (or -fnone).
 

+  Some error messages that reproduced excerpts of the grammar are now using
+  the caret information only.  For instance on:
+
+    %%
+    exp: 'a' | 'a';
+
+  Bison 2.7 reports:
+
+    in.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
+    in.y:2.12-14: warning: rule useless in parser due to conflicts: exp: 'a' [-Wother]
+
+  Now bison reports:
+
+    in.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
+    in.y:2.12-14: warning: rule useless in parser due to conflicts [-Wother]
+     exp: 'a' | 'a';
+                ^^^
+
+  and "bison -fno-caret" reports:
+
+    in.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
+    in.y:2.12-14: warning: rule useless in parser due to conflicts [-Wother]
+

 *** Enhancements of the -Werror option
 
   The -Werror=CATEGORY option is now recognized, and will treat specified
 *** Enhancements of the -Werror option
 
   The -Werror=CATEGORY option is now recognized, and will treat specified


@@ -198,6 +345,11 @@ GNU Bison NEWS
     bar.y: error: shift/reduce conflicts: 1 found, 0 expected
     bar.y: error: reduce/reduce conflicts: 2 found, 0 expected
 
     bar.y: error: shift/reduce conflicts: 1 found, 0 expected
     bar.y: error: reduce/reduce conflicts: 2 found, 0 expected
 

+** Incompatibilities with POSIX Yacc
+
+  The 'yacc' category is no longer part of '-Wall', enable it explicitly
+  with '-Wyacc'.
+

 ** Additional yylex/yyparse arguments
 
   The new directive %param declares additional arguments to both yylex and
 ** Additional yylex/yyparse arguments
 
   The new directive %param declares additional arguments to both yylex and


@@ -213,6 +365,23 @@ GNU Bison NEWS
 
     %param {arg1_type *arg1} {arg2_type *arg2}
 
 
     %param {arg1_type *arg1} {arg2_type *arg2}
 

+** Types of values for %define variables
+
+  Bison used to make no difference between '%define foo bar' and '%define
+  foo "bar"'.  The former is now called a 'keyword value', and the latter a
+  'string value'.  A third kind was added: 'code values', such as '%define
+  foo {bar}'.
+
+  Keyword variables are used for fixed value sets, e.g.,
+
+    %define lr.type lalr
+
+  Code variables are used for value in the target language, e.g.,
+
+    %define api.value.type {struct semantic_type}
+
+  String variables are used remaining cases, e.g. file names.
+

 ** Variable api.token.prefix
 
   The variable api.token.prefix changes the way tokens are identified in
 ** Variable api.token.prefix
 
   The variable api.token.prefix changes the way tokens are identified in


@@ -220,7 +389,7 @@ GNU Bison NEWS
   with identifiers in the target language.  For instance
 
     %token FILE for ERROR
   with identifiers in the target language.  For instance
 
     %token FILE for ERROR

-    %define api.token.prefix "TOK_"
+    %define api.token.prefix {TOK_}

     %%
     start: FILE for ERROR;
 
     %%
     start: FILE for ERROR;
 


@@ -229,6 +398,79 @@ GNU Bison NEWS
   use these prefixed token names, although the grammar itself still
   uses the short names (as in the sample rule given above).
 
   use these prefixed token names, although the grammar itself still
   uses the short names (as in the sample rule given above).
 

+** Variable api.value.type
+
+  This new %define variable supersedes the #define macro YYSTYPE.  The use
+  of YYSTYPE is discouraged.  In particular, #defining YYSTYPE *and* either
+  using %union or %defining api.value.type results in undefined behavior.
+
+  Either define api.value.type, or use "%union":
+
+    %union
+    {
+      int ival;
+      char *sval;
+    }
+    %token <ival> INT "integer"
+    %token <sval> STRING "string"
+    %printer { fprintf (yyo, "%d", $$); } <ival>
+    %destructor { free ($$); } <sval>
+
+    /* In yylex().  */
+    yylval.ival = 42; return INT;
+    yylval.sval = "42"; return STRING;
+
+  The %define variable api.value.type supports both keyword and code values.
+
+  The keyword value 'union' means that the user provides genuine types, not
+  union member names such as "ival" and "sval" above (WARNING: will fail if
+  -y/--yacc/%yacc is enabled).
+
+    %define api.value.type union
+    %token <int> INT "integer"
+    %token <char *> STRING "string"
+    %printer { fprintf (yyo, "%d", $$); } <int>
+    %destructor { free ($$); } <char *>
+
+    /* In yylex().  */
+    yylval.INT = 42; return INT;
+    yylval.STRING = "42"; return STRING;
+
+  The keyword value variant is somewhat equivalent, but for C++ special
+  provision is made to allow classes to be used (more about this below).
+
+    %define api.value.type variant
+    %token <int> INT "integer"
+    %token <std::string> STRING "string"
+
+  Code values (in braces) denote user defined types.  This is where YYSTYPE
+  used to be used.
+
+    %code requires
+    {
+      struct my_value
+      {
+        enum
+        {
+          is_int, is_string
+        } kind;
+        union
+        {
+          int ival;
+          char *sval;
+        } u;
+      };
+    }
+    %define api.value.type {struct my_value}
+    %token <u.ival> INT "integer"
+    %token <u.sval> STRING "string"
+    %printer { fprintf (yyo, "%d", $$); } <u.ival>
+    %destructor { free ($$); } <u.sval>
+
+    /* In yylex().  */
+    yylval.u.ival = 42; return INT;
+    yylval.u.sval = "42"; return STRING;
+

 ** Variable parse.error
 
   This variable controls the verbosity of error messages.  The use of the
 ** Variable parse.error
 
   This variable controls the verbosity of error messages.  The use of the


@@ -261,17 +503,33 @@ GNU Bison NEWS
   It used to be an error only if used in non GLR mode, _and_ if there are
   reduce/reduce conflicts.
 
   It used to be an error only if used in non GLR mode, _and_ if there are
   reduce/reduce conflicts.
 

-** Token numbering has changed to preserve the user-defined order
+** Tokens are numbered in their order of appearance
+
+  Contributed by Valentin Tolmer.
+
+  With '%token A B', A had a number less than the one of B.  However,
+  precedence declarations used to generate a reversed order.  This is now
+  fixed, and introducing tokens with any of %token, %left, %right,
+  %precedence, or %nonassoc yields the same result.
+
+  When mixing declarations of tokens with a litteral character (e.g., 'a')
+  or with an identifier (e.g., B) in a precedence declaration, Bison
+  numbered the litteral characters first.  For example

 
 

-  When declaring %token A B, the numbering for A is inferior to B. Up to now,
-  when declaring associativity at the same time, with %left (or %right,
-  %precedence, %nonassoc), B was inferior to A.
+    %right A B 'c' 'd'
+
+  would lead to the tokens declared in this order: 'c' 'd' A B.  Again, the
+  input order is now preserved.
+
+  These changes were made so that one can remove useless precedence and
+  associativity declarations (i.e., map %nonassoc, %left or %right to
+  %precedence, or to %token) and get exactly the same output.

 
 ** Useless precedence and associativity
 
   Contributed by Valentin Tolmer.
 
 
 ** Useless precedence and associativity
 
   Contributed by Valentin Tolmer.
 

-  When developping and maintaining a grammar, useless associativity and
+  When developing and maintaining a grammar, useless associativity and

   precedence directives are common.  They can be a nuisance: new ambiguities
   arising are sometimes masked because their conflicts are resolved due to
   the extra precedence or associativity information.  Furthermore, it can
   precedence directives are common.  They can be a nuisance: new ambiguities
   arising are sometimes masked because their conflicts are resolved due to
   the extra precedence or associativity information.  Furthermore, it can


@@ -296,8 +554,8 @@ GNU Bison NEWS
     %left '*'
     %%
     exp:
     %left '*'
     %%
     exp:

-      "num"
-    | exp '+' "num"
+      "number"
+    | exp '+' "number"

     | exp '*' exp
     ;
 
     | exp '*' exp
     ;
 


@@ -316,7 +574,7 @@ GNU Bison NEWS
 
     %precedence '='
     %%
 
     %precedence '='
     %%

-    exp: "var" '=' "num";
+    exp: "var" '=' "number";

 
   will produce a
 
 
   will produce a
 


@@ -331,7 +589,7 @@ GNU Bison NEWS
 
     %nonassoc '='
     %%
 
     %nonassoc '='
     %%

-    exp: "var" '=' "num";
+    exp: "var" '=' "number";

 
   The warning is:
 
 
   The warning is:
 


@@ -339,13 +597,39 @@ GNU Bison NEWS
      %nonassoc '='
                ^^^
 
      %nonassoc '='
                ^^^
 

-** Java skeleton improvements
+** Empty rules

 
 

-  Contributed by Paolo Bonzini.
+  With help from Joel E. Denny and Gabriel Rassoul.
+
+  Empty rules (i.e., with an empty right-hand side) can now be explicitly
+  marked by the new %empty directive.  Using %empty on a non-empty rule is
+  an error.  The new -Wempty-rule warning reports empty rules without
+  %empty.  On the following grammar:
+
+    %%
+    s: a b c;
+    a: ;
+    b: %empty;
+    c: 'a' %empty;
+
+  bison reports:
+
+    3.4-5: warning: empty rule without %empty [-Wempty-rule]
+     a: {}
+        ^^
+    5.8-13: error: %empty on non-empty rule
+     c: 'a' %empty {};
+            ^^^^^^
+
+** Java skeleton improvements

 
   The constants for token names were moved to the Lexer interface.  Also, it
   is possible to add code to the parser's constructors using "%code init"
   and "%define init_throws".
 
   The constants for token names were moved to the Lexer interface.  Also, it
   is possible to add code to the parser's constructors using "%code init"
   and "%define init_throws".

+  Contributed by Paolo Bonzini.
+
+  The Java skeleton now supports push parsing.
+  Contributed by Dennis Heimbigner.

 
 ** C++ skeletons improvements
 
 
 ** C++ skeletons improvements
 


@@ -387,7 +671,7 @@ GNU Bison NEWS
     ;
 
     list:
     ;
 
     list:

-      /* nothing */ { /* Generates an empty string list */ }
+      %empty        { /* Generates an empty string list. */ }

     | list item ";" { std::swap ($$, $1); $$.push_back ($2); }
     ;
 
     | list item ";" { std::swap ($$, $1); $$.push_back ($2); }
     ;
 


@@ -414,6 +698,21 @@ GNU Bison NEWS
       ...
     }
 
       ...
     }
 

+*** C++ locations
+
+  There are operator- and operator-= for 'location'.  Negative line/column
+  increments can no longer underflow the resulting value.
+
+* Noteworthy changes in release 2.7.1 (2013-04-15) [stable]
+
+** Bug fixes
+
+*** Fix compiler attribute portability (yacc.c)
+
+  With locations enabled, __attribute__ was used unprotected.
+
+*** Fix some compiler warnings (lalr1.cc)
+

 * Noteworthy changes in release 2.7 (2012-12-12) [stable]
 
 ** Bug fixes
 * Noteworthy changes in release 2.7 (2012-12-12) [stable]
 
 ** Bug fixes


@@ -464,8 +763,8 @@ GNU Bison NEWS
      exp: exp '+' exp { $exp = $1 + $3; };
                   ^^^
 
      exp: exp '+' exp { $exp = $1 + $3; };
                   ^^^
 

-  The default behaviour for now is still not to display these unless
-  explictly asked with -fcaret (or -fall). However, in a later release, it
+  The default behavior for now is still not to display these unless
+  explicitly asked with -fcaret (or -fall). However, in a later release, it

   will be made the default behavior (but may still be deactivated with
   -fno-caret).
 
   will be made the default behavior (but may still be deactivated with
   -fno-caret).
 


@@ -552,7 +851,7 @@ GNU Bison NEWS
 
   Other issues in the test suite have been addressed.
 
 
   Other issues in the test suite have been addressed.
 

-  Nul characters are correctly displayed in error messages.
+  Null characters are correctly displayed in error messages.

 
   When possible, yylloc is correctly initialized before calling yylex.  It
   is no longer necessary to initialize it in the %initial-action.
 
   When possible, yylloc is correctly initialized before calling yylex.  It
   is no longer necessary to initialize it in the %initial-action.


@@ -2433,7 +2732,7 @@ Output file does not redefine const for C++.
 
 -----
 
 
 -----
 

-Copyright (C) 1995-2013 Free Software Foundation, Inc.
+Copyright (C) 1995-2015 Free Software Foundation, Inc.

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


@@ -2468,7 +2767,12 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
  LocalWords:  Automake TMPDIR LESSEQ ylwrap endif yydebug YYTOKEN YYLSP ival hh
  LocalWords:  extern YYTOKENTYPE TOKENTYPE yytokentype tokentype STYPE lval pdf
  LocalWords:  lang yyoutput dvi html ps POSIX lvalp llocp Wother nterm arg init
  LocalWords:  Automake TMPDIR LESSEQ ylwrap endif yydebug YYTOKEN YYLSP ival hh
  LocalWords:  extern YYTOKENTYPE TOKENTYPE yytokentype tokentype STYPE lval pdf
  LocalWords:  lang yyoutput dvi html ps POSIX lvalp llocp Wother nterm arg init

- LocalWords:  TOK calc yyo fval Wconflicts
+ LocalWords:  TOK calc yyo fval Wconflicts parsers yystackp yyval yynerrs
+ LocalWords:  Théophile Ranquet Santet fno fnone stype associativity Tolmer
+ LocalWords:  Wprecedence Rassoul Wempty Paolo Bonzini parser's Michiel loc
+ LocalWords:  redeclaration sval fcaret reentrant XSLT xsl Wmaybe yyvsp Tedi
+ LocalWords:  pragmas noreturn untyped Rozenman unexpanded Wojciech Polak
+ LocalWords:  Alexandre MERCHANTABILITY yytype

 
 Local Variables:
 mode: outline
 
 Local Variables:
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