X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/f16b08196c780556cbf50691e2944960aebc46f6..757f8f98fca888609b4533aa1d7f00c2427f9564:/data/lalr1.cc?ds=sidebyside

diff --git a/data/lalr1.cc b/data/lalr1.cc
index fff83822..dc397800 100644
--- a/data/lalr1.cc
+++ b/data/lalr1.cc
@@ -1,7 +1,7 @@
 # C++ skeleton for Bison
 
-# Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation,
-# Inc.
+# Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008
+# Free Software Foundation, Inc.
 
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -18,10 +18,162 @@
 
 m4_include(b4_pkgdatadir/[c++.m4])
 
+# b4_table_define(TABLE-NAME, CONTENT)
+# ------------------------------------
+# Define "parser::yy<TABLE-NAME>_" which contents is CONTENT.
+m4_define([b4_table_define],
+[const b4_int_type_for([$2])
+  b4_parser_class_name::yy$1_[[]] =
+  {
+  $2
+  }dnl
+])
+
+# How the semantic value is extracted when using variants.
+b4_variant_if([
+  # b4_symbol_value(VAL, [TYPE])
+  # ----------------------------
+  m4_define([b4_symbol_value],
+  [m4_ifval([$2],
+            [$1.as<$2>()],
+            [$1])])
+]) # b4_variant_if
+
+
+# b4_assert_if([IF-ASSERTIONS-ARE-USED], [IF-NOT])
+# ----------------------------------------------------
+m4_define([b4_assert_if],
+[b4_percent_define_ifdef([[assert]], [$1], [$2])])
+
+
+# b4_lhs_value([TYPE])
+# --------------------
+# Expansion of $<TYPE>$.
+m4_define([b4_lhs_value],
+[b4_symbol_value([yylhs.value], [$1])])
+
+
+# b4_lhs_location()
+# -----------------
+# Expansion of @$.
+m4_define([b4_lhs_location],
+[yylhs.location])
+
+
+# b4_rhs_data(RULE-LENGTH, NUM)
+# -----------------------------
+# Return the data corresponding to the symbol #NUM, where the current
+# rule has RULE-LENGTH symbols on RHS.
+m4_define([b4_rhs_data],
+          [yystack_@{($1) - ($2)@}])
+
+
+# b4_rhs_state(RULE-LENGTH, NUM)
+# -----------------------------
+# The state corresponding to the symbol #NUM, where the current
+# rule has RULE-LENGTH symbols on RHS.
+m4_define([b4_rhs_state],
+          [b4_rhs_data([$1], [$2]).state])
+
+
+# b4_rhs_value(RULE-LENGTH, NUM, [TYPE])
+# --------------------------------------
+# Expansion of $<TYPE>NUM, where the current rule has RULE-LENGTH
+# symbols on RHS.
+m4_define([b4_rhs_value],
+          [b4_symbol_value([b4_rhs_data([$1], [$2]).value], [$3])])
+
+
+# b4_rhs_location(RULE-LENGTH, NUM)
+# ---------------------------------
+# Expansion of @NUM, where the current rule has RULE-LENGTH symbols
+# on RHS.
+m4_define([b4_rhs_location],
+          [b4_rhs_data([$1], [$2]).location])
+
+
+# b4_symbol_actions(FILENAME, LINENO,
+#                   SYMBOL-TAG, SYMBOL-NUM,
+#                   SYMBOL-ACTION, SYMBOL-TYPENAME)
+# -------------------------------------------------
+# Same as in C, but using references instead of pointers.
+m4_define([b4_symbol_actions],
+[m4_pushdef([b4_dollar_dollar],
+            [b4_symbol_value([yysym.value], [$6])])dnl
+m4_pushdef([b4_at_dollar], [yysym.location])dnl
+      case $4: // $3
+b4_syncline([$2], [$1])
+        $5;
+b4_syncline([@oline@], [@ofile@])
+        break;
+m4_popdef([b4_at_dollar])dnl
+m4_popdef([b4_dollar_dollar])dnl
+])
+
+
+# b4_symbol_action_(SYMBOL-TAG, SYMBOL-NUM, SYMBOL-TYPENAME)
+# ----------------------------------------------------------
+# Invoke b4_dollar_dollar(SYMBOL_TYPENAME) for each symbol.
+m4_define([b4_symbol_action_],
+[m4_ifval($3,
+[      case $2: // $1
+        b4_dollar_dollar($@);
+	break;
+])])
+
+
+# b4_symbol_variant(YYTYPE, YYVAL, ACTION, [ARGS])
+# ------------------------------------------------
+# Run some ACTION ("build", or "destroy") on YYVAL of symbol type
+# YYTYPE.
+m4_define([b4_symbol_variant],
+[m4_pushdef([b4_dollar_dollar],
+            [$2.$3<$][3>(m4_shift3($@))])dnl
+  switch ($1)
+    {
+m4_map([b4_symbol_action_], m4_defn([b4_type_names]))
+     default:
+       break;
+    }
+m4_popdef([b4_dollar_dollar])dnl
+])
+
+
+# _b4_char_sizeof_counter
+# -----------------------
+# A counter used by _b4_char_sizeof_dummy to create fresh symbols.
+m4_define([_b4_char_sizeof_counter],
+[0])
+
+# _b4_char_sizeof_dummy
+# ---------------------
+# At each call return a new C++ identifier.
+m4_define([_b4_char_sizeof_dummy],
+[m4_define([_b4_char_sizeof_counter], m4_incr(_b4_char_sizeof_counter))dnl
+dummy[]_b4_char_sizeof_counter])
+
+
+# b4_char_sizeof(SYMBOL-TAG, SYMBOL-NUM, SYMBOL-TYPENAME)
+# -------------------------------------------------------
+# To be mapped on the list of type names to produce:
+#
+#    char dummy1[sizeof(type_name_1)];
+#    char dummy2[sizeof(type_name_2)];
+#
+# for defined type names.
+# $3 is doubly-quoted, do not quote it again.
+m4_define([b4_char_sizeof],
+[m4_ifval($3,
+[
+      char _b4_char_sizeof_dummy@{sizeof($3)@}; // $1])dnl
+])
+
+
+m4_pushdef([b4_copyright_years],
+           [2002, 2003, 2004, 2005, 2006, 2007, 2008])
+
 m4_define([b4_parser_class_name],
           [b4_percent_define_get([[parser_class_name]])])
-m4_define([b4_namespace],
-          [b4_percent_define_get([[namespace]])])
 
 # The header is mandatory.
 b4_defines_if([],
@@ -35,9 +187,8 @@ m4_include(b4_pkgdatadir/[location.cc])
 m4_changecom()
 m4_divert_push(0)dnl
 b4_defines_if(
-[@output(b4_spec_defines_file@)
-b4_copyright([Skeleton interface for Bison LALR(1) parsers in C++],
-  [2002, 2003, 2004, 2005, 2006])
+[@output(b4_spec_defines_file@)@
+b4_copyright([Skeleton interface for Bison LALR(1) parsers in C++])
 dnl FIXME: This is wrong, we want computed header guards.
 [
 /* C++ LALR(1) parser skeleton written by Akim Demaille.  */
@@ -47,15 +198,93 @@ dnl FIXME: This is wrong, we want computed header guards.
 
 ]b4_percent_code_get([[requires]])[
 
+]b4_assert_if([#include <cassert>])[
 #include <string>
 #include <iostream>
 #include "stack.hh"
 
-namespace ]b4_namespace[
-{
+]b4_namespace_open[
   class position;
   class location;
-}
+]b4_variant_if(
+[[
+  /// A char[S] buffer to store and retrieve objects.
+  ///
+  /// Sort of a variant, but does not keep track of the nature
+  /// of the stored data, since that knowledge is available
+  /// via the current state.
+  template <size_t S>
+  struct variant
+  {]b4_assert_if([
+    /// Whether something is contained.
+    bool built;
+
+    /// Initially uninitialized.
+    variant ()
+      : built(false)
+    {}])[
+
+    /// Instantiate a \a T in here.
+    template <typename T>
+    inline T&
+    build()
+    {]b4_assert_if([
+      assert(!built);
+      built = true;])[
+      return *new (buffer) T;
+    }
+
+    /// Accessor to a built \a T.
+    template <typename T>
+    inline T&
+    as()
+    {]b4_assert_if([
+      assert(built);])[
+      return reinterpret_cast<T&>(buffer);
+    }
+
+    /// Const accessor to a built \a T (for %printer).
+    template <typename T>
+    inline const T&
+    as() const
+    {]b4_assert_if([
+      assert(built);])[
+      return reinterpret_cast<const T&>(buffer);
+    }
+
+    /// Swap the content with \a other.
+    template <typename T>
+    inline void
+    swap(variant<S>& other)
+    {
+      std::swap(as<T>(), other.as<T>());
+    }
+
+    /// Assign the content of \a other to this.
+    /// Destroys \a other.
+    template <typename T>
+    inline void
+    build(variant<S>& other)
+    {
+      build<T>();
+      swap<T>(other);
+      other.destroy<T>();
+    }
+
+    /// Destroy the stored \a T.
+    template <typename T>
+    inline void
+    destroy()
+    {
+      as<T>().~T();]b4_assert_if([
+      built = false;])[
+    }
+
+    /// A buffer large enough to store any of the semantic values.
+    char buffer[S];
+  };
+]])[
+]b4_namespace_close[
 
 #include "location.hh"
 
@@ -82,37 +311,43 @@ namespace ]b4_namespace[
    the previous symbol: RHS[0] (always defined).  */
 
 #ifndef YYLLOC_DEFAULT
-# define YYLLOC_DEFAULT(Current, Rhs, N)		\
-do {							\
-  if (N)						\
-    {							\
-      (Current).begin = (Rhs)[1].begin;			\
-      (Current).end   = (Rhs)[N].end;			\
-    }							\
-  else							\
-    {							\
-      (Current).begin = (Current).end = (Rhs)[0].end;	\
-    }							\
+# define YYLLOC_DEFAULT(Current, Rhs, N)                        \
+do {                                                            \
+  if (N)                                                        \
+    {                                                           \
+      (Current).begin = (Rhs)[1].location.begin;                \
+      (Current).end   = (Rhs)[N].location.end;			\
+    }                                                           \
+  else                                                          \
+    {                                                           \
+      (Current).begin = (Current).end = (Rhs)[0].location.end;	\
+    }                                                           \
 } while (false)
 #endif
 
-namespace ]b4_namespace[
-{
+]b4_namespace_open[
 
   /// A Bison parser.
   class ]b4_parser_class_name[
   {
   public:
-    /// Symbol semantic values.
 #ifndef YYSTYPE
-]m4_ifdef([b4_stype],
+]b4_variant_if(
+[    /// An auxiliary type to compute the largest semantic type.
+    union union_type
+    {]m4_map([b4_char_sizeof], m4_defn([b4_type_names]))[
+    };
+
+    /// Symbol semantic values.
+    typedef variant<sizeof(union_type)> semantic_type;],
+[    /// Symbol semantic values.
+m4_ifdef([b4_stype],
 [    union semantic_type
-    {
-b4_user_stype
+    {b4_user_stype
     };],
 [m4_if(b4_tag_seen_flag, 0,
 [[    typedef int semantic_type;]],
-[[    typedef YYSTYPE semantic_type;]])])[
+[[    typedef YYSTYPE semantic_type;]])])])[
 #else
     typedef YYSTYPE semantic_type;
 #endif
@@ -134,6 +369,7 @@ b4_user_stype
     /// \returns  0 iff parsing succeeded.
     virtual int parse ();
 
+#if YYDEBUG
     /// The current debugging stream.
     std::ostream& debug_stream () const;
     /// Set the current debugging stream.
@@ -145,6 +381,7 @@ b4_user_stype
     debug_level_type debug_level () const;
     /// Set the current debugging level.
     void set_debug_level (debug_level_type l);
+#endif
 
   private:
     /// Report a syntax error.
@@ -155,42 +392,10 @@ b4_user_stype
     /// Generate an error message.
     /// \param state   the state where the error occurred.
     /// \param tok     the lookahead token.
-    virtual std::string yysyntax_error_ (int yystate]dnl
-b4_error_verbose_if([, int tok])[);
-
-#if YYDEBUG
-    /// \brief Report a symbol value on the debug stream.
-    /// \param yytype       The token type.
-    /// \param yyvaluep     Its semantic value.
-    /// \param yylocationp  Its location.
-    virtual void yy_symbol_value_print_ (int yytype,
-					 const semantic_type* yyvaluep,
-					 const location_type* yylocationp);
-    /// \brief Report a symbol on the debug stream.
-    /// \param yytype       The token type.
-    /// \param yyvaluep     Its semantic value.
-    /// \param yylocationp  Its location.
-    virtual void yy_symbol_print_ (int yytype,
-				   const semantic_type* yyvaluep,
-				   const location_type* yylocationp);
-#endif
-
+    virtual std::string yysyntax_error_ (int yystate, int tok);
 
     /// State numbers.
     typedef int state_type;
-    /// State stack type.
-    typedef stack<state_type>    state_stack_type;
-    /// Semantic value stack type.
-    typedef stack<semantic_type> semantic_stack_type;
-    /// location stack type.
-    typedef stack<location_type> location_stack_type;
-
-    /// The state stack.
-    state_stack_type yystate_stack_;
-    /// The semantic value stack.
-    semantic_stack_type yysemantic_stack_;
-    /// The location stack.
-    location_stack_type yylocation_stack_;
 
     /// Internal symbol numbers.
     typedef ]b4_int_type_for([b4_translate])[ token_number_type;
@@ -236,12 +441,6 @@ b4_error_verbose_if([, int tok])[);
 #endif
 
 #if YYDEBUG
-    /// A type to store symbol numbers and -1.
-    typedef ]b4_int_type_for([b4_rhs])[ rhs_number_type;
-    /// A `-1'-separated list of the rules' RHS.
-    static const rhs_number_type yyrhs_[];
-    /// For each rule, the index of the first RHS symbol in \a yyrhs_.
-    static const ]b4_int_type_for([b4_prhs])[ yyprhs_[];
     /// For each rule, its source line number.
     static const ]b4_int_type_for([b4_rline])[ yyrline_[];
     /// For each scanner token number, its symbol number.
@@ -259,15 +458,92 @@ b4_error_verbose_if([, int tok])[);
     /// Convert a scanner token number \a t to a symbol number.
     token_number_type yytranslate_ (int t);
 
+    /// A complete symbol, with its type.
+    struct symbol_base_type
+    {
+      /// Default constructor.
+      inline symbol_base_type ();
+
+      /// Constructor.
+      inline symbol_base_type (const semantic_type& v, const location_type& l);
+
+      /// Return the type of this symbol.
+      virtual int type_get () const = 0;
+
+      /// The semantic value.
+      semantic_type value;
+
+      /// The location.
+      location_type location;
+    };
+
+#if YYDEBUG
+    /// \brief Display a symbol type, value and location.
+    /// \param yyo    The output stream.
+    /// \param yysym  The symbol.
+    void yy_print_ (std::ostream& yyo, const symbol_base_type& yysym) const;
+#endif
+
     /// \brief Reclaim the memory associated to a symbol.
-    /// \param yymsg        Why this token is reclaimed.
-    /// \param yytype       The symbol type.
-    /// \param yyvaluep     Its semantic value.
-    /// \param yylocationp  Its location.
-    inline void yydestruct_ (const char* yymsg,
-			     int yytype,
-			     semantic_type* yyvaluep,
-			     location_type* yylocationp);
+    /// \param yymsg     Why this token is reclaimed.
+    ///                  If null, print nothing.
+    /// \param s         The symbol.
+    inline void yy_destroy_ (const char* yymsg, symbol_base_type& yysym) const;
+
+    /// Element of the stack: a state and its attributes.
+    struct symbol_type : symbol_base_type
+    {
+      /// Default constructor.
+      inline symbol_type ();
+
+      /// Constructor.
+      inline symbol_type (int t,
+                          const semantic_type& v, const location_type& l);
+
+      /// The symbol type.
+      int type;
+
+      /// Return the type corresponding to this state.
+      virtual inline int type_get () const;
+    };
+
+    /// Element of the stack: a state and its attributes.
+    struct stack_symbol_type : symbol_base_type
+    {
+      /// Default constructor.
+      inline stack_symbol_type ();
+
+      /// Constructor.
+      inline stack_symbol_type (state_type s,
+                                const semantic_type& v, const location_type& l);
+
+      /// The state.
+      state_type state;
+
+      /// Return the type corresponding to this state.
+      virtual inline int type_get () const;
+    };
+
+    /// Stack type.
+    typedef stack<stack_symbol_type> stack_type;
+
+    /// The stack.
+    stack_type yystack_;
+
+    /// Push a new state on the stack.
+    /// \param m    a debug message to display
+    ///             if null, no trace is output.
+    /// \param s    the symbol
+    /// \warning the contents of \a s.value is stolen.
+    inline void yypush_ (const char* m, stack_symbol_type& s);
+
+    /// Push a new look ahead token on the state on the stack.
+    /// \param m    a debug message to display
+    ///             if null, no trace is output.
+    /// \param s    the state
+    /// \param sym  the symbol (for its value and location).
+    /// \warning the contents of \a s.value is stolen.
+    inline void yypush_ (const char* m, state_type s, symbol_type& sym);
 
     /// Pop \a n symbols the three stacks.
     inline void yypop_ (unsigned int n = 1);
@@ -286,23 +562,23 @@ b4_error_verbose_if([, int tok])[);
     static const token_number_type yyundef_token_;
 ]b4_parse_param_vars[
   };
-}
+
+]b4_namespace_close[
 
 ]b4_percent_define_flag_if([[global_tokens_and_yystype]],
 [b4_token_defines(b4_tokens)
 
 #ifndef YYSTYPE
  /* Redirection for backward compatibility.  */
-# define YYSTYPE b4_namespace::b4_parser_class_name::semantic_type
+# define YYSTYPE b4_namespace_ref::b4_parser_class_name::semantic_type
 #endif
 ])
 b4_percent_code_get([[provides]])[]dnl
 
 [#endif /* ! defined PARSER_HEADER_H */]
 ])dnl
-@output(b4_parser_file_name@)
-b4_copyright([Skeleton implementation for Bison LALR(1) parsers in C++],
-  [2002, 2003, 2004, 2005, 2006])
+@output(b4_parser_file_name@)@
+b4_copyright([Skeleton implementation for Bison LALR(1) parsers in C++])
 b4_percent_code_get([[top]])[]dnl
 m4_if(b4_prefix, [yy], [],
 [
@@ -340,43 +616,46 @@ b4_percent_code_get[]dnl
 /* A pseudo ostream that takes yydebug_ into account.  */
 # define YYCDEBUG if (yydebug_) (*yycdebug_)
 
-# define YY_SYMBOL_PRINT(Title, Type, Value, Location)	\
-do {							\
-  if (yydebug_)						\
-    {							\
-      *yycdebug_ << Title << ' ';			\
-      yy_symbol_print_ ((Type), (Value), (Location));	\
-      *yycdebug_ << std::endl;				\
-    }							\
-} while (false)
+# define YY_SYMBOL_PRINT(Title, Symbol)         \
+  do {                                          \
+    if (yydebug_)                               \
+    {                                           \
+      *yycdebug_ << Title << ' ';               \
+      yy_print_ (*yycdebug_, Symbol);           \
+      *yycdebug_ << std::endl;                  \
+    }                                           \
+  } while (false)
 
 # define YY_REDUCE_PRINT(Rule)		\
-do {					\
-  if (yydebug_)				\
-    yy_reduce_print_ (Rule);		\
-} while (false)
+  do {					\
+    if (yydebug_)                       \
+      yy_reduce_print_ (Rule);		\
+  } while (false)
 
 # define YY_STACK_PRINT()		\
-do {					\
-  if (yydebug_)				\
-    yystack_print_ ();			\
-} while (false)
+  do {					\
+    if (yydebug_)                       \
+      yystack_print_ ();                \
+  } while (false)
 
 #else /* !YYDEBUG */
 
 # define YYCDEBUG if (false) std::cerr
-# define YY_SYMBOL_PRINT(Title, Type, Value, Location)
-# define YY_REDUCE_PRINT(Rule)
-# define YY_STACK_PRINT()
+# define YY_SYMBOL_PRINT(Title, Symbol)  static_cast<void>(0)
+# define YY_REDUCE_PRINT(Rule)           static_cast<void>(0)
+# define YY_STACK_PRINT()                static_cast<void>(0)
 
 #endif /* !YYDEBUG */
 
+#define yyerrok		(yyerrstatus_ = 0)
+#define yyclearin	(yychar = yyempty_)
+
 #define YYACCEPT	goto yyacceptlab
 #define YYABORT		goto yyabortlab
 #define YYERROR		goto yyerrorlab
+#define YYRECOVERING()  (!!yyerrstatus_)
 
-namespace ]b4_namespace[
-{
+]b4_namespace_open[
 #if YYERROR_VERBOSE
 
   /* Return YYSTR after stripping away unnecessary quotes and
@@ -432,62 +711,133 @@ namespace ]b4_namespace[
   {
   }
 
-#if YYDEBUG
-  /*--------------------------------.
-  | Print this symbol on YYOUTPUT.  |
-  `--------------------------------*/
 
-  inline void
-  ]b4_parser_class_name[::yy_symbol_value_print_ (int yytype,
-			   const semantic_type* yyvaluep, const location_type* yylocationp)
+  /*---------------.
+  | Symbol types.  |
+  `---------------*/
+
+  // symbol_base_type.
+  ]b4_parser_class_name[::symbol_base_type::symbol_base_type ()
+    : value()
+    , location()
   {
-    YYUSE (yylocationp);
-    YYUSE (yyvaluep);
-    switch (yytype)
-      {
-  ]m4_map([b4_symbol_actions], m4_defn([b4_symbol_printers]))dnl
-[       default:
-	  break;
-      }
   }
 
+  ]b4_parser_class_name[::symbol_base_type::symbol_base_type (const semantic_type& v, const location_type& l)
 
-  void
-  ]b4_parser_class_name[::yy_symbol_print_ (int yytype,
-			   const semantic_type* yyvaluep, const location_type* yylocationp)
+    : value(v)
+    , location(l)
+  {
+  }
+
+  // symbol_type.
+  ]b4_parser_class_name[::symbol_type::symbol_type ()
+    : type()
+    , symbol_base_type()
   {
-    *yycdebug_ << (yytype < yyntokens_ ? "token" : "nterm")
-	       << ' ' << yytname_[yytype] << " ("
-	       << *yylocationp << ": ";
-    yy_symbol_value_print_ (yytype, yyvaluep, yylocationp);
-    *yycdebug_ << ')';
   }
-#endif
+
+  ]b4_parser_class_name[::symbol_type::symbol_type (int t,
+                           const semantic_type& v, const location_type& l)
+    : type(t)
+    , symbol_base_type(v, l)
+  {
+  }
+
+  int
+  ]b4_parser_class_name[::symbol_type::type_get () const
+  {
+    return type;
+  }
+
+  // stack_symbol_type.
+  ]b4_parser_class_name[::stack_symbol_type::stack_symbol_type ()
+    : state()
+    , symbol_base_type()
+  {
+  }
+
+  ]b4_parser_class_name[::stack_symbol_type::stack_symbol_type (state_type s,
+                           const semantic_type& v, const location_type& l)
+    : state(s)
+    , symbol_base_type(v, l)
+  {
+  }
+
+  int
+  ]b4_parser_class_name[::stack_symbol_type::type_get () const
+  {
+    return yystos_[state];
+  }
+
 
   void
-  ]b4_parser_class_name[::yydestruct_ (const char* yymsg,
-			   int yytype, semantic_type* yyvaluep, location_type* yylocationp)
+  ]b4_parser_class_name[::yy_destroy_ (const char* yymsg, symbol_base_type& yysym) const
   {
-    YYUSE (yylocationp);
+    int yytype = yysym.type_get ();
     YYUSE (yymsg);
-    YYUSE (yyvaluep);
-
-    YY_SYMBOL_PRINT (yymsg, yytype, yyvaluep, yylocationp);
+    if (yymsg)
+      YY_SYMBOL_PRINT (yymsg, yysym);
 
+    // User destructor.
     switch (yytype)
       {
   ]m4_map([b4_symbol_actions], m4_defn([b4_symbol_destructors]))[
 	default:
 	  break;
+      }]b4_variant_if([
+
+    // Type destructor.
+    b4_symbol_variant([[yytype]], [[yysym.value]], [[destroy]])])[
+  }
+
+#if YYDEBUG
+  void
+  ]b4_parser_class_name[::yy_print_ (std::ostream& yyo, const symbol_base_type& yysym) const
+  {
+    int yytype = yysym.type_get ();
+    yyo << (yytype < yyntokens_ ? "token" : "nterm")
+        << ' ' << yytname_[yytype] << " ("
+        << yysym.location << ": ";
+    switch (yytype)
+      {
+  ]m4_map([b4_symbol_actions], m4_defn([b4_symbol_printers]))dnl
+[       default:
+	  break;
       }
+    yyo << ')';
+  }
+#endif
+
+  void
+  ]b4_parser_class_name[::yypush_ (const char* m, state_type s,
+                                   symbol_type& sym)
+  {
+    if (m)
+      YY_SYMBOL_PRINT (m, sym);
+]b4_variant_if(
+[[    yystack_.push (stack_symbol_type (s, semantic_type(), sym.location));
+    ]b4_symbol_variant([[yystos_[s]]], [[yystack_[0].value]],
+                       [build], [sym.value])],
+[    yystack_.push (stack_symbol_type (s, sym.value, sym.location));])[
+  }
+
+  void
+  ]b4_parser_class_name[::yypush_ (const char* m, stack_symbol_type& s)
+  {
+    if (m)
+      YY_SYMBOL_PRINT (m, s);
+]b4_variant_if(
+[[    yystack_.push (stack_symbol_type (s.state, semantic_type(), s.location));
+    ]b4_symbol_variant([[yystos_[s.state]]], [[yystack_[0].value]],
+                       [build], [s.value])],
+[    yystack_.push (s);])[
   }
 
   void
   ]b4_parser_class_name[::yypop_ (unsigned int n)
   {
-    yystate_stack_.pop (n);
-    yysemantic_stack_.pop (n);
-    yylocation_stack_.pop (n);
+    yystack_.pop (n);
   }
 
 #if YYDEBUG
@@ -520,9 +870,8 @@ namespace ]b4_namespace[
   int
   ]b4_parser_class_name[::parse ()
   {
-    /// Lookahead and lookahead in internal form.
+    /// Coded type of the lookahead.
     int yychar = yyempty_;
-    int yytoken = 0;
 
     /* State.  */
     int yyn;
@@ -533,43 +882,39 @@ namespace ]b4_namespace[
     int yynerrs_ = 0;
     int yyerrstatus_ = 0;
 
-    /// Semantic value of the lookahead.
-    semantic_type yylval;
-    /// Location of the lookahead.
-    location_type yylloc;
+    /// The lookahead symbol.
+    symbol_type yyla;
+
     /// The locations where the error started and ended.
-    location yyerror_range[2];
+    stack_symbol_type yyerror_range[2];
 
-    /// $$.
-    semantic_type yyval;
-    /// @@$.
-    location_type yyloc;
+    /// $$ and @@$.
+    stack_symbol_type yylhs;
 
+    /// The return value of parse().
     int yyresult;
 
     YYCDEBUG << "Starting parse" << std::endl;
 
 ]m4_ifdef([b4_initial_action], [
-m4_pushdef([b4_at_dollar],     [yylloc])dnl
-m4_pushdef([b4_dollar_dollar], [yylval])dnl
+m4_pushdef([b4_at_dollar],     [yyla.location])dnl
+m4_pushdef([b4_dollar_dollar], [yyla.value])dnl
     /* User initialization code.  */
     b4_user_initial_action
 m4_popdef([b4_dollar_dollar])dnl
 m4_popdef([b4_at_dollar])])dnl
 
-  [  /* Initialize the stacks.  The initial state will be pushed in
+  [  /* Initialize the stack.  The initial state will be set in
        yynewstate, since the latter expects the semantical and the
        location values to have been already stored, initialize these
        stacks with a primary value.  */
-    yystate_stack_ = state_stack_type (0);
-    yysemantic_stack_ = semantic_stack_type (0);
-    yylocation_stack_ = location_stack_type (0);
-    yysemantic_stack_.push (yylval);
-    yylocation_stack_.push (yylloc);
+    yystack_ = stack_type (0);
+    yypush_ (0, 0, yyla);
 
-    /* New state.  */
+    // A new state was pushed on the stack.
+    // Invariant: yystate == yystack_[0].state, i.e.,
+    // yystate was just pushed onto the state stack.
   yynewstate:
-    yystate_stack_.push (yystate);
     YYCDEBUG << "Entering state " << yystate << std::endl;
 
     /* Accept?  */
@@ -591,8 +936,8 @@ m4_popdef([b4_at_dollar])])dnl
       {
 	YYCDEBUG << "Reading a token: ";
 	yychar = ]b4_c_function_call([yylex], [int],
-				     [[YYSTYPE*], [&yylval]][]dnl
-b4_locations_if([, [[location*], [&yylloc]]])dnl
+				     [[YYSTYPE*], [&yyla.value]][]dnl
+b4_locations_if([, [[location*], [&yyla.location]]])dnl
 m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
       }
 
@@ -600,19 +945,19 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
     /* Convert token to internal form.  */
     if (yychar <= yyeof_)
       {
-	yychar = yytoken = yyeof_;
+	yychar = yyla.type = yyeof_;
 	YYCDEBUG << "Now at end of input." << std::endl;
       }
     else
       {
-	yytoken = yytranslate_ (yychar);
-	YY_SYMBOL_PRINT ("Next token is", yytoken, &yylval, &yylloc);
+	yyla.type = yytranslate_ (yychar);
+	YY_SYMBOL_PRINT ("Next token is", yyla);
       }
 
-    /* If the proper action on seeing token YYTOKEN is to reduce or to
-       detect an error, take that action.  */
-    yyn += yytoken;
-    if (yyn < 0 || yylast_ < yyn || yycheck_[yyn] != yytoken)
+    /* If the proper action on seeing token YYLA.TYPE is to reduce or
+       to detect an error, take that action.  */
+    yyn += yyla.type;
+    if (yyn < 0 || yylast_ < yyn || yycheck_[yyn] != yyla.type)
       goto yydefault;
 
     /* Reduce or error.  */
@@ -620,26 +965,22 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
     if (yyn <= 0)
       {
 	if (yyn == 0 || yyn == yytable_ninf_)
-	goto yyerrlab;
+	  goto yyerrlab;
 	yyn = -yyn;
 	goto yyreduce;
       }
 
-    /* Shift the lookahead token.  */
-    YY_SYMBOL_PRINT ("Shifting", yytoken, &yylval, &yylloc);
-
     /* Discard the token being shifted.  */
     yychar = yyempty_;
 
-    yysemantic_stack_.push (yylval);
-    yylocation_stack_.push (yylloc);
-
     /* Count tokens shifted since error; after three, turn off error
        status.  */
     if (yyerrstatus_)
       --yyerrstatus_;
 
+    /* Shift the lookahead token.  */
     yystate = yyn;
+    yypush_ ("Shifting", yystate, yyla);
     goto yynewstate;
 
   /*-----------------------------------------------------------.
@@ -655,45 +996,65 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
   | yyreduce -- Do a reduction.  |
   `-----------------------------*/
   yyreduce:
-    yylen = yyr2_[yyn];
+    yylen = yyr2_[yyn];]b4_variant_if([
+    /* Variants are always initialized to an empty instance of the
+       correct type. The default $$=$1 rule is NOT applied when using
+       variants */
+    ]b4_symbol_variant([[yyr1_@{yyn@}]], [yylhs.value], [build])[],[
     /* If YYLEN is nonzero, implement the default value of the action:
        `$$ = $1'.  Otherwise, use the top of the stack.
 
-       Otherwise, the following line sets YYVAL to garbage.
+       Otherwise, the following line sets YYLHS.VALUE to garbage.
        This behavior is undocumented and Bison
        users should not rely upon it.  */
     if (yylen)
-      yyval = yysemantic_stack_[yylen - 1];
+      yylhs.value = yystack_@{yylen - 1@}.value;
     else
-      yyval = yysemantic_stack_[0];
+      yylhs.value = yystack_@{0@}.value;])[
 
+    // Compute the default @@$.
     {
-      slice<location_type, location_stack_type> slice (yylocation_stack_, yylen);
-      YYLLOC_DEFAULT (yyloc, slice, yylen);
+      slice<stack_symbol_type, stack_type> slice (yystack_, yylen);
+      YYLLOC_DEFAULT (yylhs.location, slice, yylen);
     }
+
+    // Perform the reduction.
     YY_REDUCE_PRINT (yyn);
     switch (yyn)
       {
 	]b4_user_actions[
-	default: break;
+	default:
+          break;
       }
-    YY_SYMBOL_PRINT ("-> $$ =", yyr1_[yyn], &yyval, &yyloc);
+    // Compute post-reduction state.
+    yyn = yyr1_[yyn];
+    yystate = yypgoto_[yyn - yyntokens_] + yystack_[yylen].state;
+    if (0 <= yystate && yystate <= yylast_
+	&& yycheck_[yystate] == yystack_[yylen].state)
+      yystate = yytable_[yystate];
+    else
+      yystate = yydefgoto_[yyn - yyntokens_];
+    yylhs.state = yystate;
+    YY_SYMBOL_PRINT ("-> $$ =", yylhs);
+]b4_variant_if([[
+    // Destroy the lhs symbols.
+    for (int i = 0; i < yylen; ++i)
+      // Destroy a variant which value may have be swapped with
+      // yylhs.value.  The value of yylhs.value (hence maybe one of
+      // these lhs symbols) depends on what does the default
+      // contruction for this type.  In the case of pointers for
+      // instance, nothing is done, so the value is junk.  Therefore
+      // do not try to report the content in the debug trace, it's
+      // junk.  Hence yymsg = 0.  Besides, that keeps exactly the same
+      // traces as with the other Bison skeletons.
+      yy_destroy_ (0, yystack_[i]);]])[
 
     yypop_ (yylen);
     yylen = 0;
     YY_STACK_PRINT ();
 
-    yysemantic_stack_.push (yyval);
-    yylocation_stack_.push (yyloc);
-
     /* Shift the result of the reduction.  */
-    yyn = yyr1_[yyn];
-    yystate = yypgoto_[yyn - yyntokens_] + yystate_stack_[0];
-    if (0 <= yystate && yystate <= yylast_
-	&& yycheck_[yystate] == yystate_stack_[0])
-      yystate = yytable_[yystate];
-    else
-      yystate = yydefgoto_[yyn - yyntokens_];
+    yypush_ (0, yylhs);
     goto yynewstate;
 
   /*------------------------------------.
@@ -704,11 +1065,10 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))[;
     if (!yyerrstatus_)
       {
 	++yynerrs_;
-	error (yylloc, yysyntax_error_ (yystate]dnl
-b4_error_verbose_if([, yytoken])[));
+	error (yyla.location, yysyntax_error_ (yystate, yyla.type));
       }
 
-    yyerror_range[0] = yylloc;
+    yyerror_range[0].location = yyla.location;
     if (yyerrstatus_ == 3)
       {
 	/* If just tried and failed to reuse lookahead token after an
@@ -716,13 +1076,13 @@ b4_error_verbose_if([, yytoken])[));
 
 	if (yychar <= yyeof_)
 	  {
-	  /* Return failure if at end of input.  */
-	  if (yychar == yyeof_)
-	    YYABORT;
+            /* Return failure if at end of input.  */
+            if (yychar == yyeof_)
+              YYABORT;
 	  }
 	else
 	  {
-	    yydestruct_ ("Error: discarding", yytoken, &yylval, &yylloc);
+	    yy_destroy_ ("Error: discarding", yyla);
 	    yychar = yyempty_;
 	  }
       }
@@ -743,12 +1103,12 @@ b4_error_verbose_if([, yytoken])[));
     if (false)
       goto yyerrorlab;
 
-    yyerror_range[0] = yylocation_stack_[yylen - 1];
+    yyerror_range[0].location = yystack_[yylen - 1].location;
     /* Do not reclaim the symbols of the rule which action triggered
        this YYERROR.  */
     yypop_ (yylen);
     yylen = 0;
-    yystate = yystate_stack_[0];
+    yystate = yystack_[0].state;
     goto yyerrlab1;
 
   /*-------------------------------------------------------------.
@@ -756,46 +1116,40 @@ b4_error_verbose_if([, yytoken])[));
   `-------------------------------------------------------------*/
   yyerrlab1:
     yyerrstatus_ = 3;	/* Each real token shifted decrements this.  */
+    {
+      stack_symbol_type error_token;
+      for (;;)
+        {
+          yyn = yypact_[yystate];
+          if (yyn != yypact_ninf_)
+            {
+              yyn += yyterror_;
+              if (0 <= yyn && yyn <= yylast_ && yycheck_[yyn] == yyterror_)
+                {
+                  yyn = yytable_[yyn];
+                  if (0 < yyn)
+                    break;
+                }
+            }
 
-    for (;;)
-      {
-	yyn = yypact_[yystate];
-	if (yyn != yypact_ninf_)
-	{
-	  yyn += yyterror_;
-	  if (0 <= yyn && yyn <= yylast_ && yycheck_[yyn] == yyterror_)
-	    {
-	      yyn = yytable_[yyn];
-	      if (0 < yyn)
-		break;
-	    }
-	}
-
-	/* Pop the current state because it cannot handle the error token.  */
-	if (yystate_stack_.height () == 1)
-	YYABORT;
-
-	yyerror_range[0] = yylocation_stack_[0];
-	yydestruct_ ("Error: popping",
-		     yystos_[yystate],
-		     &yysemantic_stack_[0], &yylocation_stack_[0]);
-	yypop_ ();
-	yystate = yystate_stack_[0];
-	YY_STACK_PRINT ();
-      }
+          // Pop the current state because it cannot handle the error token.
+          if (yystack_.size () == 1)
+            YYABORT;
 
-    yyerror_range[1] = yylloc;
-    // Using YYLLOC is tempting, but would change the location of
-    // the lookahead.  YYLOC is available though.
-    YYLLOC_DEFAULT (yyloc, (yyerror_range - 1), 2);
-    yysemantic_stack_.push (yylval);
-    yylocation_stack_.push (yyloc);
+          yyerror_range[0].location = yystack_[0].location;
+          yy_destroy_ ("Error: popping", yystack_[0]);
+          yypop_ ();
+          yystate = yystack_[0].state;
+          YY_STACK_PRINT ();
+        }
 
-    /* Shift the error token.  */
-    YY_SYMBOL_PRINT ("Shifting", yystos_[yyn],
-		   &yysemantic_stack_[0], &yylocation_stack_[0]);
+      yyerror_range[1].location = yyla.location;
+      YYLLOC_DEFAULT (error_token.location, (yyerror_range - 1), 2);
 
-    yystate = yyn;
+      /* Shift the error token.  */
+      error_token.state = yystate = yyn;
+      yypush_ ("Shifting", error_token);
+    }
     goto yynewstate;
 
     /* Accept.  */
@@ -810,17 +1164,14 @@ b4_error_verbose_if([, yytoken])[));
 
   yyreturn:
     if (yychar != yyempty_)
-      yydestruct_ ("Cleanup: discarding lookahead", yytoken, &yylval, &yylloc);
+      yy_destroy_ ("Cleanup: discarding lookahead", yyla);
 
     /* Do not reclaim the symbols of the rule which action triggered
        this YYABORT or YYACCEPT.  */
     yypop_ (yylen);
-    while (yystate_stack_.height () != 1)
+    while (yystack_.size () != 1)
       {
-	yydestruct_ ("Cleanup: popping",
-		   yystos_[yystate_stack_[0]],
-		   &yysemantic_stack_[0],
-		   &yylocation_stack_[0]);
+	yy_destroy_ ("Cleanup: popping", yystack_[0]);
 	yypop_ ();
       }
 
@@ -829,8 +1180,8 @@ b4_error_verbose_if([, yytoken])[));
 
   // Generate an error message.
   std::string
-  ]b4_parser_class_name[::yysyntax_error_ (int yystate]dnl
-b4_error_verbose_if([, int tok])[)
+  ]b4_parser_class_name[::yysyntax_error_ (int yystate, int]dnl
+b4_error_verbose_if([ tok])[)
   {
     std::string res;
     YYUSE (yystate);
@@ -881,83 +1232,43 @@ b4_error_verbose_if([, int tok])[)
   /* YYPACT[STATE-NUM] -- Index in YYTABLE of the portion describing
      STATE-NUM.  */
   const ]b4_int_type(b4_pact_ninf, b4_pact_ninf) b4_parser_class_name::yypact_ninf_ = b4_pact_ninf[;
-  const ]b4_int_type_for([b4_pact])[
-  ]b4_parser_class_name[::yypact_[] =
-  {
-    ]b4_pact[
-  };
+  ]b4_table_define([pact], [b4_pact])[;
 
   /* YYDEFACT[S] -- default rule to reduce with in state S when YYTABLE
      doesn't specify something else to do.  Zero means the default is an
      error.  */
-  const ]b4_int_type_for([b4_defact])[
-  ]b4_parser_class_name[::yydefact_[] =
-  {
-    ]b4_defact[
-  };
+  ]b4_table_define([defact], [b4_defact])[;
 
   /* YYPGOTO[NTERM-NUM].  */
-  const ]b4_int_type_for([b4_pgoto])[
-  ]b4_parser_class_name[::yypgoto_[] =
-  {
-    ]b4_pgoto[
-  };
+  ]b4_table_define([pgoto], [b4_pgoto])[;
 
   /* YYDEFGOTO[NTERM-NUM].  */
-  const ]b4_int_type_for([b4_defgoto])[
-  ]b4_parser_class_name[::yydefgoto_[] =
-  {
-    ]b4_defgoto[
-  };
+  ]b4_table_define([defgoto], [b4_defgoto])[;
 
   /* YYTABLE[YYPACT[STATE-NUM]].  What to do in state STATE-NUM.  If
      positive, shift that token.  If negative, reduce the rule which
      number is the opposite.  If zero, do what YYDEFACT says.  */
   const ]b4_int_type(b4_table_ninf, b4_table_ninf) b4_parser_class_name::yytable_ninf_ = b4_table_ninf[;
-  const ]b4_int_type_for([b4_table])[
-  ]b4_parser_class_name[::yytable_[] =
-  {
-    ]b4_table[
-  };
+  ]b4_table_define([table], [b4_table])[;
 
   /* YYCHECK.  */
-  const ]b4_int_type_for([b4_check])[
-  ]b4_parser_class_name[::yycheck_[] =
-  {
-    ]b4_check[
-  };
+  ]b4_table_define([check], [b4_check])[;
 
   /* STOS_[STATE-NUM] -- The (internal number of the) accessing
      symbol of state STATE-NUM.  */
-  const ]b4_int_type_for([b4_stos])[
-  ]b4_parser_class_name[::yystos_[] =
-  {
-    ]b4_stos[
-  };
+  ]b4_table_define([stos], [b4_stos])[;
 
 #if YYDEBUG
   /* TOKEN_NUMBER_[YYLEX-NUM] -- Internal symbol number corresponding
      to YYLEX-NUM.  */
-  const ]b4_int_type_for([b4_toknum])[
-  ]b4_parser_class_name[::yytoken_number_[] =
-  {
-    ]b4_toknum[
-  };
+  ]b4_table_define([token_number], [b4_toknum])[;
 #endif
 
   /* YYR1[YYN] -- Symbol number of symbol that rule YYN derives.  */
-  const ]b4_int_type_for([b4_r1])[
-  ]b4_parser_class_name[::yyr1_[] =
-  {
-    ]b4_r1[
-  };
+  ]b4_table_define([r1], [b4_r1])[;
 
   /* YYR2[YYN] -- Number of symbols composing right hand side of rule YYN.  */
-  const ]b4_int_type_for([b4_r2])[
-  ]b4_parser_class_name[::yyr2_[] =
-  {
-    ]b4_r2[
-  };
+  ]b4_table_define([r2], [b4_r2])[;
 
 #if YYDEBUG || YYERROR_VERBOSE || YYTOKEN_TABLE
   /* YYTNAME[SYMBOL-NUM] -- String name of the symbol SYMBOL-NUM.
@@ -965,41 +1276,24 @@ b4_error_verbose_if([, int tok])[)
   const char*
   const ]b4_parser_class_name[::yytname_[] =
   {
-    ]b4_tname[
+  ]b4_tname[
   };
 #endif
 
 #if YYDEBUG
-  /* YYRHS -- A `-1'-separated list of the rules' RHS.  */
-  const ]b4_parser_class_name[::rhs_number_type
-  ]b4_parser_class_name[::yyrhs_[] =
-  {
-    ]b4_rhs[
-  };
-
-  /* YYPRHS[YYN] -- Index of the first RHS symbol of rule number YYN in
-     YYRHS.  */
-  const ]b4_int_type_for([b4_prhs])[
-  ]b4_parser_class_name[::yyprhs_[] =
-  {
-    ]b4_prhs[
-  };
-
   /* YYRLINE[YYN] -- Source line where rule number YYN was defined.  */
-  const ]b4_int_type_for([b4_rline])[
-  ]b4_parser_class_name[::yyrline_[] =
-  {
-    ]b4_rline[
-  };
+  ]b4_table_define([rline], [b4_rline])[;
 
   // Print the state stack on the debug stream.
   void
   ]b4_parser_class_name[::yystack_print_ ()
   {
     *yycdebug_ << "Stack now";
-    for (state_stack_type::const_iterator i = yystate_stack_.begin ();
-	 i != yystate_stack_.end (); ++i)
-      *yycdebug_ << ' ' << *i;
+    for (stack_type::const_iterator
+           i = yystack_.begin (),
+           i_end = yystack_.end ();
+	 i != i_end; ++i)
+      *yycdebug_ << ' ' << i->state;
     *yycdebug_ << std::endl;
   }
 
@@ -1015,9 +1309,7 @@ b4_error_verbose_if([, int tok])[)
     /* The symbols being reduced.  */
     for (int yyi = 0; yyi < yynrhs; yyi++)
       YY_SYMBOL_PRINT ("   $" << yyi + 1 << " =",
-		       yyrhs_[yyprhs_[yyrule] + yyi],
-		       &]b4_rhs_value(yynrhs, yyi + 1)[,
-		       &]b4_rhs_location(yynrhs, yyi + 1)[);
+                       ]b4_rhs_data(yynrhs, yyi + 1)[);
   }
 #endif // YYDEBUG
 
@@ -1029,7 +1321,7 @@ b4_error_verbose_if([, int tok])[)
     const token_number_type
     translate_table[] =
     {
-      ]b4_translate[
+  ]b4_translate[
     };
     if ((unsigned int) t <= yyuser_token_number_max_)
       return translate_table[t];
@@ -1049,21 +1341,18 @@ b4_error_verbose_if([, int tok])[)
   const unsigned int ]b4_parser_class_name[::yyuser_token_number_max_ = ]b4_user_token_number_max[;
   const ]b4_parser_class_name[::token_number_type ]b4_parser_class_name[::yyundef_token_ = ]b4_undef_token_number[;
 
-} // namespace ]b4_namespace[
+]b4_namespace_close[
 
-]b4_epilogue
-dnl
-@output(b4_dir_prefix[]stack.hh@)
-b4_copyright([Stack handling for Bison parsers in C++],
-  [2002, 2003, 2004, 2005, 2006])[
+]b4_epilogue[]dnl
+@output(b4_dir_prefix[]stack.hh@)@
+b4_copyright([Stack handling for Bison parsers in C++])[
 
 #ifndef BISON_STACK_HH
 # define BISON_STACK_HH
 
 #include <deque>
 
-namespace ]b4_namespace[
-{
+]b4_namespace_open[
   template <class T, class S = std::deque<T> >
   class stack
   {
@@ -1111,17 +1400,17 @@ namespace ]b4_namespace[
     }
 
     inline
-    unsigned int
-    height () const
+    typename S::size_type
+    size () const
     {
       return seq_.size ();
     }
 
     inline const_iterator begin () const { return seq_.rbegin (); }
-    inline const_iterator end () const { return seq_.rend (); }
+    inline const_iterator end ()   const { return seq_.rend ();   }
 
   private:
-
+    /// The wrapped container.
     S seq_;
   };
 
@@ -1149,7 +1438,9 @@ namespace ]b4_namespace[
     const S& stack_;
     unsigned int range_;
   };
-}
+]b4_namespace_close[
 
-#endif // not BISON_STACK_HH]
+#endif // not BISON_STACK_HH[]dnl
+]
 m4_divert_pop(0)
+m4_popdef([b4_copyright_years])dnl