data/variant.hh

   1 # C++ skeleton for Bison
   2
   3 # Copyright (C) 2002-2013 Free Software Foundation, Inc.
   4
   5 # This program is free software: you can redistribute it and/or modify
   6 # it under the terms of the GNU General Public License as published by
   7 # the Free Software Foundation, either version 3 of the License, or
   8 # (at your option) any later version.
   9 #
  10 # This program is distributed in the hope that it will be useful,
  11 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 # GNU General Public License for more details.
  14 #
  15 # You should have received a copy of the GNU General Public License
  16 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17
  18
  19 ## --------- ##
  20 ## variant.  ##
  21 ## --------- ##
  22
  23 # b4_symbol_variant(YYTYPE, YYVAL, ACTION, [ARGS])
  24 # ------------------------------------------------
  25 # Run some ACTION ("build", or "destroy") on YYVAL of symbol type
  26 # YYTYPE.
  27 m4_define([b4_symbol_variant],
  28 [m4_pushdef([b4_dollar_dollar],
  29             [$2.$3< $][3 >(m4_shift3($@))])dnl
  30   switch ($1)
  31     {
  32 b4_type_foreach([b4_type_action_])[]dnl
  33       default:
  34         break;
  35     }
  36 m4_popdef([b4_dollar_dollar])dnl
  37 ])
  38
  39
  40 # _b4_char_sizeof_counter
  41 # -----------------------
  42 # A counter used by _b4_char_sizeof_dummy to create fresh symbols.
  43 m4_define([_b4_char_sizeof_counter],
  44 [0])
  45
  46 # _b4_char_sizeof_dummy
  47 # ---------------------
  48 # At each call return a new C++ identifier.
  49 m4_define([_b4_char_sizeof_dummy],
  50 [m4_define([_b4_char_sizeof_counter], m4_incr(_b4_char_sizeof_counter))dnl
  51 dummy[]_b4_char_sizeof_counter])
  52
  53
  54 # b4_char_sizeof(SYMBOL-NUMS)
  55 # ---------------------------
  56 # To be mapped on the list of type names to produce:
  57 #
  58 #    char dummy1[sizeof(type_name_1)];
  59 #    char dummy2[sizeof(type_name_2)];
  60 #
  61 # for defined type names.
  62 m4_define([b4_char_sizeof],
  63 [b4_symbol_if([$1], [has_type],
  64 [
  65 m4_map([      b4_symbol_tag_comment], [$@])dnl
  66       char _b4_char_sizeof_dummy@{sizeof([b4_symbol([$1], [type])])@};
  67 ])])
  68
  69
  70 # b4_variant_includes
  71 # -------------------
  72 # The needed includes for variants support.
  73 m4_define([b4_variant_includes],
  74 [b4_parse_assert_if([[#include <typeinfo>]])[
  75 #include <cstdlib>  // abort
  76 #ifndef YYASSERT
  77 # include <cassert>
  78 # define YYASSERT assert
  79 #endif
  80 ]])
  81
  82 # b4_variant_define
  83 # -----------------
  84 # Define "variant".
  85 m4_define([b4_variant_define],
  86 [[  /// A char[S] buffer to store and retrieve objects.
  87   ///
  88   /// Sort of a variant, but does not keep track of the nature
  89   /// of the stored data, since that knowledge is available
  90   /// via the current state.
  91   template <size_t S>
  92   struct variant
  93   {
  94     /// Type of *this.
  95     typedef variant<S> self_type;
  96
  97     /// Empty construction.
  98     variant ()]b4_parse_assert_if([
  99       : built (false)
 100       , tname (YY_NULL)])[
 101     {}
 102
 103     /// Instantiate a \a T in here.
 104     template <typename T>
 105     T&
 106     build ()
 107     {]b4_parse_assert_if([
 108       //YYASSERT (!built);
 109       //YYASSERT (!tname);
 110       YYASSERT (sizeof (T) <= S);
 111       built = true;
 112       tname = typeid (T).name ();])[
 113       return *new (buffer.raw) T;
 114     }
 115
 116     /// Instantiate a \a T in here from \a t.
 117     template <typename T>
 118     T&
 119     build (const T& t)
 120     {]b4_parse_assert_if([
 121       //YYASSERT (!built);
 122       //YYASSERT (!tname);
 123       YYASSERT (sizeof (T) <= S);
 124       built = true;
 125       tname = typeid (T).name ();])[
 126       return *new (buffer.raw) T (t);
 127     }
 128
 129     /// Construct and fill.
 130     template <typename T>
 131     variant (const T& t)]b4_parse_assert_if([
 132       : built (true)
 133       , tname (typeid (T).name ())])[
 134     {
 135       YYASSERT (sizeof (T) <= S);
 136       new (buffer.raw) T (t);
 137     }
 138
 139     /// Accessor to a built \a T.
 140     template <typename T>
 141     T&
 142     as ()
 143     {]b4_parse_assert_if([
 144       YYASSERT (built);
 145       YYASSERT (tname == typeid (T).name ());
 146       YYASSERT (sizeof (T) <= S);])[
 147       return reinterpret_cast<T&> (buffer.raw);
 148     }
 149
 150     /// Const accessor to a built \a T (for %printer).
 151     template <typename T>
 152     const T&
 153     as () const
 154     {]b4_parse_assert_if([
 155       YYASSERT (built);
 156       YYASSERT (tname == typeid (T).name ());
 157       YYASSERT (sizeof (T) <= S);])[
 158       return reinterpret_cast<const T&> (buffer.raw);
 159     }
 160
 161     /// Swap the content with \a other, of same type.
 162     /// Both variants must be built beforehand, because swapping the actual
 163     /// data requires reading it (with as()), and this is not possible on
 164     /// unconstructed variants: it would require some dynamic testing, which
 165     /// should not be the variant's responsability.
 166     /// Swapping between built and ((possibly) non-built is done with
 167     /// variant::move ().
 168     template <typename T>
 169     void
 170     swap (variant<S>& other)
 171     {]b4_parse_assert_if([
 172       YYASSERT (built);
 173       YYASSERT (other.built);
 174       YYASSERT (tname == other.tname);])[
 175       std::swap (as<T>(), other.as<T>());
 176     }
 177
 178     /// Assign the content of \a other to this.
 179     /// Destroys \a other.
 180     template <typename T>
 181     void
 182     move (variant<S>& other)
 183     {]b4_parse_assert_if([
 184       YYASSERT (! built);])[
 185       build<T>();
 186       swap<T>(other);
 187       other.destroy<T>();
 188     }
 189
 190     /// Copy the content of \a other to this.
 191     /// Destroys \a other.
 192     template <typename T>
 193     void
 194     copy (const variant<S>& other)
 195     {
 196       build<T> (other.as<T> ());
 197     }
 198
 199     /// Destroy the stored \a T.
 200     template <typename T>
 201     void
 202     destroy ()
 203     {
 204       as<T> ().~T ();]b4_parse_assert_if([
 205       built = false;
 206       tname = YY_NULL;])[
 207     }
 208
 209     /// Prohibit blind copies.
 210     private:
 211     self_type& operator=(const self_type&)
 212     {
 213       abort ();
 214     }
 215
 216     variant (const self_type&)
 217     {
 218       abort ();
 219     }
 220
 221   private:
 222     /// A buffer large enough to store any of the semantic values.
 223     /// Long double is chosen as it has the strongest alignment
 224     /// constraints.
 225     union
 226     {
 227       long double align_me;
 228       char raw[S];
 229     } buffer;]b4_parse_assert_if([
 230     /// Whether something is contained.
 231     bool built;
 232     /// If defined, the name of the stored type.
 233     const char* tname;])[
 234   };
 235 ]])
 236
 237
 238 ## -------------------------- ##
 239 ## Adjustments for variants.  ##
 240 ## -------------------------- ##
 241
 242
 243 # b4_semantic_type_declare
 244 # ------------------------
 245 # Declare semantic_type.
 246 m4_define([b4_semantic_type_declare],
 247 [    /// An auxiliary type to compute the largest semantic type.
 248     union union_type
 249     {]b4_type_foreach([b4_char_sizeof])[};
 250
 251     /// Symbol semantic values.
 252     typedef variant<sizeof(union_type)> semantic_type;dnl
 253 ])
 254
 255
 256 # How the semantic value is extracted when using variants.
 257
 258 # b4_symbol_value(VAL, [TYPE])
 259 # ----------------------------
 260 m4_define([b4_symbol_value],
 261 [m4_ifval([$2],
 262           [$1.as< $2 >()],
 263           [$1])])
 264
 265 # b4_symbol_value_template(VAL, [TYPE])
 266 # -------------------------------------
 267 # Same as b4_symbol_value, but used in a template method.
 268 m4_define([b4_symbol_value_template],
 269 [m4_ifval([$2],
 270           [$1.template as< $2 >()],
 271           [$1])])
 272
 273
 274
 275 ## ------------- ##
 276 ## make_SYMBOL.  ##
 277 ## ------------- ##
 278
 279
 280 # b4_symbol_constructor_declare_(SYMBOL-NUMBER)
 281 # ---------------------------------------------
 282 # Declare the overloaded version of make_symbol for the (common) type of
 283 # these SYMBOL-NUMBERS.  Use at class-level.
 284 m4_define([b4_symbol_constructor_declare_],
 285 [b4_symbol_if([$1], [is_token], [b4_symbol_if([$1], [has_id],
 286 [    static inline
 287     symbol_type
 288     make_[]b4_symbol_([$1], [id]) (dnl
 289 b4_join(b4_symbol_if([$1], [has_type],
 290                      [const b4_symbol([$1], [type])& v]),
 291         b4_locations_if([const location_type& l])));
 292
 293 ])])])
 294
 295
 296 # b4_symbol_constructor_declare
 297 # -----------------------------
 298 # Declare symbol constructors for all the value types.
 299 # Use at class-level.
 300 m4_define([b4_symbol_constructor_declare],
 301 [    // Symbol constructors declarations.
 302 b4_symbol_foreach([b4_symbol_constructor_declare_])])
 303
 304
 305
 306 # b4_symbol_constructor_define_(SYMBOL-NUMBER)
 307 # --------------------------------------------
 308 # Define symbol constructor for this SYMBOL-NUMBER.
 309 m4_define([b4_symbol_constructor_define_],
 310 [b4_symbol_if([$1], [is_token], [b4_symbol_if([$1], [has_id],
 311 [  b4_parser_class_name::symbol_type
 312   b4_parser_class_name::make_[]b4_symbol_([$1], [id]) (dnl
 313 b4_join(b4_symbol_if([$1], [has_type],
 314                      [const b4_symbol([$1], [type])& v]),
 315         b4_locations_if([const location_type& l])))
 316   {
 317     return symbol_type (b4_join([token::b4_symbol([$1], [id])],
 318                                 b4_symbol_if([$1], [has_type], [v]),
 319                                 b4_locations_if([l])));
 320   }
 321
 322 ])])])
 323
 324
 325 # b4_symbol_constructor_define
 326 # ----------------------------
 327 # Define the overloaded versions of make_symbol for all the value types.
 328 m4_define([b4_symbol_constructor_define],
 329 [  // Implementation of make_symbol for each symbol type.
 330 b4_symbol_foreach([b4_symbol_constructor_define_])])