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Reduce the size of variant, it doesn't need an index of type size_t internally. 

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 _Storage::__index_type
for comparison with variant_npos.
(variant::index): Use _Base::_Storage::__index_type
for comparison with variant_npos.
* testsuite/20_util/variant/index_type.cc: New.

From-SVN: r244309
This commit is contained in:
Ville Voutilainen 2017-01-11 13:23:43 +02:00 committed by Ville Voutilainen
parent 5102089246
commit f3df0b3cde
3 changed files with 67 additions and 5 deletions
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20
libstdc++-v3/ChangeLog
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@ -1,3 +1,23 @@
2017-01-11 Ville Voutilainen <ville.voutilainen@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 _Storage::__index_type
for comparison with variant_npos.
(variant::index): Use _Base::_Storage::__index_type
for comparison with variant_npos.
* testsuite/20_util/variant/index_type.cc: New.
2017-01-10 Jonathan Wakely <jwakely@redhat.com>
* testsuite/18_support/exception_ptr/60612-unexpected.cc: Adjust

28
libstdc++-v3/include/std/variant
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@ -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?
@ -1086,7 +1099,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ return !this->_M_valid(); }
constexpr size_t index() const noexcept
{ return this->_M_index; }
{
if (this->_M_index ==
typename _Base::_Storage::__index_type(variant_npos))
return variant_npos;
return this->_M_index;
}
void
swap(variant& __rhs)

24
libstdc++-v3/testsuite/20_util/variant/index_type.cc Normal file
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@ -0,0 +1,24 @@
// { dg-options "-std=gnu++17" }
// { dg-do compile { target x86_64-*-* powerpc*-*-* } }
// 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>
static_assert(sizeof(std::variant<signed char, unsigned char>)
< sizeof(size_t));