Tested on Linux-x64.
2017-01-09 Ville Voutilainen <ville.voutilai...@gmail.com>
Reduce the size of variant, it doesn't need an index of
type size_t internally.
* include/std/variant (parse_numbers.h): New include.
(__select_index): New.
(_Variant_storage<false, _Types...>::_M_reset_impl): Use
_index_type for comparison with variant_npos.
(_Variant_storage<false, _Types...>::__index_type): New.
(_Variant_storage<false, _Types...>::_M_index): Change the
type from size_t to __index_type.
(_Variant_storage<true, _Types...>::__index_type): New.
(_Variant_storage<true, _Types...>::_M_index): Change the
type from size_t to __index_type.
(_Variant_base::_M_valid): Use __index_type for comparison
with variant_npos.
(variant::__index_type): New.
(variant::index): Use __index_type for comparison with variant_npos.
* testsuite/20_util/variant/index_type.cc: New.
diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant
index 3d025a7..b016f32 100644
--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -43,6 +43,7 @@
#include <bits/functional_hash.h>
#include <bits/invoke.h>
#include <ext/aligned_buffer.h>
+#include <bits/parse_numbers.h>
namespace std _GLIBCXX_VISIBILITY(default)
{
@@ -314,6 +315,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<bool __trivially_destructible, typename... _Types>
struct _Variant_storage;
+ template <typename... _Types>
+ using __select_index =
+ typename __select_int::_Select_int_base<sizeof...(_Types)+1,
+ unsigned char,
+ unsigned short>
+ ::type::value_type;
+
template<typename... _Types>
struct _Variant_storage<false, _Types...>
{
@@ -332,7 +340,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<size_t... __indices>
constexpr void _M_reset_impl(std::index_sequence<__indices...>)
{
- if (_M_index != variant_npos)
+ if (_M_index != __index_type(variant_npos))
_S_vtable<__indices...>[_M_index](*this);
}
@@ -346,7 +354,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ _M_reset(); }
_Variadic_union<_Types...> _M_u;
- size_t _M_index;
+ using __index_type = __select_index<_Types...>;
+ __index_type _M_index;
};
template<typename... _Types>
@@ -364,7 +373,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ _M_index = variant_npos; }
_Variadic_union<_Types...> _M_u;
- size_t _M_index;
+ using __index_type = __select_index<_Types...>;
+ __index_type _M_index;
};
// Helps SFINAE on special member functions. Otherwise it can live in variant
@@ -487,7 +497,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
constexpr bool
_M_valid() const noexcept
- { return this->_M_index != variant_npos; }
+ {
+ return this->_M_index !=
+ typename _Storage::__index_type(variant_npos);
+ }
};
// For how many times does _Tp appear in _Tuple?
@@ -944,6 +957,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__detail::__variant::__index_of_v<_Tp, _Types...>;
public:
+ using __index_type = typename _Base::_Storage::__index_type;
constexpr variant()
noexcept(is_nothrow_default_constructible_v<__to_type<0>>) = default;
variant(const variant&) = default;
@@ -1086,7 +1100,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ return !this->_M_valid(); }
constexpr size_t index() const noexcept
- { return this->_M_index; }
+ {
+ if (this->_M_index == __index_type(variant_npos))
+ return variant_npos;
+ return this->_M_index;
+ }
void
swap(variant& __rhs)
diff --git a/libstdc++-v3/testsuite/20_util/variant/index_type.cc
b/libstdc++-v3/testsuite/20_util/variant/index_type.cc
new file mode 100644
index 0000000..ea6b4d6
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/variant/index_type.cc
@@ -0,0 +1,43 @@
+// { dg-options "-std=gnu++17" }
+// { dg-do compile }
+
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library. This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3. If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <variant>
+#include <type_traits>
+#include <climits>
+
+template <size_t N> struct Bogus {};
+
+template <size_t... I> auto f(std::index_sequence<I...>)
+{
+ return std::variant<Bogus<I>...>{};
+}
+
+static_assert(sizeof(char) >= sizeof(int) ||
+ CHAR_BIT != 8 ||
+ std::is_same_v<
+ decltype(f(std::make_index_sequence<3>()))::__index_type,
+ unsigned char>);
+
+static_assert(sizeof(char) >= sizeof(int) ||
+ sizeof(char) >= sizeof(short) ||
+ CHAR_BIT != 8 ||
+ std::is_same_v<
+ decltype(f(std::make_index_sequence<260>()))::__index_type,
+ unsigned short>);
