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7be08dfbe7
The "variant" structure provides a means to store, in a typeless way, C++ objects. Manipulating it without provide the type of the stored content is doomed to failure. So provide a means to copy in a type safe way, and prohibit typeless assignments. * data/c++.m4 (symbol_type::move): New. * data/lalr1.cc: Use it. * data/variant.hh (b4_variant_define): Provide variant::copy. Let variant::operator= abort. We cannot undefine it, yet, as it is still uses by the implicit assigment in symbols, which must also be disabled.
328 lines
8.5 KiB
C++
328 lines
8.5 KiB
C++
# C++ skeleton for Bison
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# Copyright (C) 2002-2012 Free Software Foundation, Inc.
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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## --------- ##
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## variant. ##
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## --------- ##
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# b4_symbol_variant(YYTYPE, YYVAL, ACTION, [ARGS])
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# ------------------------------------------------
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# Run some ACTION ("build", or "destroy") on YYVAL of symbol type
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# YYTYPE.
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m4_define([b4_symbol_variant],
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[m4_pushdef([b4_dollar_dollar],
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[$2.$3< $][3 >(m4_shift3($@))])dnl
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switch ($1)
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{
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b4_type_foreach([b4_type_action_])[]dnl
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default:
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break;
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}
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m4_popdef([b4_dollar_dollar])dnl
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])
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# _b4_char_sizeof_counter
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# -----------------------
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# A counter used by _b4_char_sizeof_dummy to create fresh symbols.
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m4_define([_b4_char_sizeof_counter],
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[0])
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# _b4_char_sizeof_dummy
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# ---------------------
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# At each call return a new C++ identifier.
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m4_define([_b4_char_sizeof_dummy],
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[m4_define([_b4_char_sizeof_counter], m4_incr(_b4_char_sizeof_counter))dnl
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dummy[]_b4_char_sizeof_counter])
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# b4_char_sizeof_(SYMBOL-NUM)
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# ---------------------------
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# A comment describing this symbol.
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m4_define([b4_char_sizeof_],
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[ // b4_symbol([$1], [tag])
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])
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# b4_char_sizeof(SYMBOL-NUMS)
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# ---------------------------
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# To be mapped on the list of type names to produce:
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#
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# char dummy1[sizeof(type_name_1)];
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# char dummy2[sizeof(type_name_2)];
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#
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# for defined type names.
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m4_define([b4_char_sizeof],
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[b4_symbol_if([$1], [has_type],
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[
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m4_map([b4_char_sizeof_], [$@])dnl
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char _b4_char_sizeof_dummy@{sizeof([b4_symbol([$1], [type])])@};
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])])
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# b4_variant_includes
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# -------------------
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# The needed includes for variants support.
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m4_define([b4_variant_includes],
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[b4_parse_assert_if([[#include <typeinfo>]])[
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#include <cstdlib> // abort
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#ifndef YYASSERT
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# include <cassert>
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# define YYASSERT assert
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#endif
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]])
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# b4_variant_define
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# -----------------
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# Define "variant".
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m4_define([b4_variant_define],
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[[ /// A char[S] buffer to store and retrieve objects.
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///
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/// Sort of a variant, but does not keep track of the nature
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/// of the stored data, since that knowledge is available
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/// via the current state.
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template <size_t S>
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struct variant
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{
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/// Type of *this.
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typedef variant<S> self_type;
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/// Empty construction.
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inline
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variant ()]b4_parse_assert_if([
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: built (false)
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, tname (YY_NULL)])[
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{}
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/// Instantiate a \a T in here.
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template <typename T>
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inline T&
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build ()
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{]b4_parse_assert_if([
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YYASSERT (!built);
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YYASSERT (!tname);
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YYASSERT (sizeof (T) <= S);
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built = true;
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tname = typeid (T).name ();])[
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return *new (buffer.raw) T;
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}
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/// Instantiate a \a T in here from \a t.
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template <typename T>
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inline T&
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build (const T& t)
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{]b4_parse_assert_if([
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YYASSERT (!built);
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YYASSERT (!tname);
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YYASSERT (sizeof (T) <= S);
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built = true;
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tname = typeid (T).name ();])[
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return *new (buffer.raw) T (t);
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}
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/// Construct and fill.
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template <typename T>
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inline
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variant (const T& t)]b4_parse_assert_if([
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: built (true)
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, tname (typeid (T).name ())])[
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{
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YYASSERT (sizeof (T) <= S);
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new (buffer.raw) T (t);
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}
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/// Accessor to a built \a T.
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template <typename T>
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inline T&
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as ()
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{]b4_parse_assert_if([
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YYASSERT (built);
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YYASSERT (tname == typeid (T).name ());
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YYASSERT (sizeof (T) <= S);])[
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return reinterpret_cast<T&> (buffer.raw);
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}
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/// Const accessor to a built \a T (for %printer).
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template <typename T>
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inline const T&
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as () const
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{]b4_parse_assert_if([
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YYASSERT (built);
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YYASSERT (tname == typeid (T).name ());
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YYASSERT (sizeof (T) <= S);])[
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return reinterpret_cast<const T&> (buffer.raw);
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}
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/// Swap the content with \a other, of same type.
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template <typename T>
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inline void
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swap (variant<S>& other)
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{]b4_parse_assert_if([
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YYASSERT (tname == other.tname);])[
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std::swap (as<T>(), other.as<T>());]b4_parse_assert_if([
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std::swap (built, other.built);
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std::swap (tname, other.tname);])[
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}
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/// Assign the content of \a other to this.
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/// Destroys \a other.
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template <typename T>
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inline void
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build (variant<S>& other)
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{
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build<T>();
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swap<T>(other);
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other.destroy<T>();
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}
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/// Copy the content of \a other to this.
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/// Destroys \a other.
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template <typename T>
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inline void
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copy (const variant<S>& other)
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{
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build<T> (other.as<T> ());
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}
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/// Destroy the stored \a T.
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template <typename T>
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inline void
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destroy ()
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{
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as<T> ().~T ();]b4_parse_assert_if([
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built = false;
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tname = YY_NULL;])[
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}
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/// Prohibit blind copies.
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// private:
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self_type& operator=(const self_type&)
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{
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abort ();
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}
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private:
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/// A buffer large enough to store any of the semantic values.
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/// Long double is chosen as it has the strongest alignment
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/// constraints.
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union
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{
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long double align_me;
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char raw[S];
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} buffer;]b4_parse_assert_if([
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/// Whether something is contained.
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bool built;
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/// If defined, the name of the stored type.
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const char* tname;])[
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};
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]])
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## -------------------------- ##
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## Adjustments for variants. ##
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## -------------------------- ##
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# b4_semantic_type_declare
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# ------------------------
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# Declare semantic_type.
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m4_define([b4_semantic_type_declare],
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[ /// An auxiliary type to compute the largest semantic type.
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union union_type
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{]b4_type_foreach([b4_char_sizeof])[};
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/// Symbol semantic values.
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typedef variant<sizeof(union_type)> semantic_type;dnl
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])
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# How the semantic value is extracted when using variants.
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# b4_symbol_value(VAL, [TYPE])
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# ----------------------------
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m4_define([b4_symbol_value],
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[m4_ifval([$2],
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[$1.as< $2 >()],
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[$1])])
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# b4_symbol_value_template(VAL, [TYPE])
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# -------------------------------------
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# Same as b4_symbol_value, but used in a template method.
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m4_define([b4_symbol_value_template],
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[m4_ifval([$2],
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[$1.template as< $2 >()],
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[$1])])
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## ------------- ##
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## make_SYMBOL. ##
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## ------------- ##
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# b4_symbol_constructor_declare_(SYMBOL-NUMBER)
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# ---------------------------------------------
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# Declare the overloaded version of make_symbol for the (common) type of
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# these SYMBOL-NUMBERS. Use at class-level.
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m4_define([b4_symbol_constructor_declare_],
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[b4_symbol_if([$1], [is_token], [b4_symbol_if([$1], [has_id],
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[ static inline
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symbol_type
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make_[]b4_symbol_([$1], [id]) (dnl
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b4_join(b4_symbol_if([$1], [has_type],
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[const b4_symbol([$1], [type])& v]),
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b4_locations_if([const location_type& l])));
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])])])
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# b4_symbol_constructor_declare
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# -----------------------------
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# Declare symbol constructors for all the value types.
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# Use at class-level.
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m4_define([b4_symbol_constructor_declare],
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[ // Symbol constructors declarations.
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b4_symbol_foreach([b4_symbol_constructor_declare_])])
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# b4_symbol_constructor_define_(SYMBOL-NUMBER)
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# --------------------------------------------
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# Define symbol constructor for this SYMBOL-NUMBER.
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m4_define([b4_symbol_constructor_define_],
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[b4_symbol_if([$1], [is_token], [b4_symbol_if([$1], [has_id],
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[ b4_parser_class_name::symbol_type
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b4_parser_class_name::make_[]b4_symbol_([$1], [id]) (dnl
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b4_join(b4_symbol_if([$1], [has_type],
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[const b4_symbol([$1], [type])& v]),
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b4_locations_if([const location_type& l])))
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{
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return symbol_type (b4_join([token::b4_symbol([$1], [id])],
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b4_symbol_if([$1], [has_type], [v]),
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b4_locations_if([l])));
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}
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])])])
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# b4_symbol_constructor_define
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# ----------------------------
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# Define the overloaded versions of make_symbol for all the value types.
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m4_define([b4_symbol_constructor_define],
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[ // Implementation of make_symbol for each symbol type.
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b4_symbol_foreach([b4_symbol_constructor_define_])])
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