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re PR libstdc++/60970 (Support std::hash with enum types (LWG 2148))

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2015-07-29  Ville Voutilainen  <ville.voutilainen@gmail.com>

	PR libstdc++/60970
	* include/bits/functional_hash.h (__hash_enum): New.
	(hash): Derive from __hash_enum.
	* testsuite/20_util/hash/60970.cc: New.

From-SVN: r226347
This commit is contained in:
Ville Voutilainen 2015-07-29 15:41:23 +03:00 committed by Jonathan Wakely
parent c2ec330c9a
commit 1fa9ba224e
3 changed files with 71 additions and 0 deletions
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7
libstdc++-v3/ChangeLog
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@ -1,3 +1,10 @@
2015-07-29 Ville Voutilainen <ville.voutilainen@gmail.com>
PR libstdc++/60970
* include/bits/functional_hash.h (__hash_enum): New.
(hash): Derive from __hash_enum.
* testsuite/20_util/hash/60970.cc: New.
2015-07-29 Tim Shen <timshen@google.com>
PR libstdc++/67015

28
libstdc++-v3/include/bits/functional_hash.h
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@ -57,6 +57,34 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Tp>
struct hash;
// Helper struct for SFINAE-poisoning non-enum types.
template<typename _Tp, bool = is_enum<_Tp>::value>
struct __hash_enum
{
private:
// Private rather than deleted to be non-trivially-copyable.
__hash_enum(__hash_enum&&);
~__hash_enum();
};
// Helper struct for hash with enum types.
template<typename _Tp>
struct __hash_enum<_Tp, true> : public __hash_base<size_t, _Tp>
{
size_t
operator()(_Tp __val) const noexcept
{
using __type = typename underlying_type<_Tp>::type;
return hash<__type>{}(static_cast<__type>(__val));
}
};
/// Primary class template hash, usable for enum types only.
// Use with non-enum types still SFINAES.
template<typename _Tp>
struct hash : __hash_enum<_Tp>
{ };
/// Partial specializations for pointer types.
template<typename _Tp>
struct hash<_Tp*> : public __hash_base<size_t, _Tp*>

36
libstdc++-v3/testsuite/20_util/hash/60970.cc Normal file
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@ -0,0 +1,36 @@
// { dg-options "-std=gnu++11" }
// { dg-do run }
// Copyright (C) 2015 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 <functional>
#include <testsuite_hooks.h>
using namespace std;
enum E1 : int {FIRST=1, SECOND=2};
enum class E2 : int {THIRD=42, FOURTH=666};
int main()
{
VERIFY(hash<int>{}(1) == hash<E1>{}(FIRST));
VERIFY(hash<int>{}(2) == hash<E1>{}(SECOND));
VERIFY(hash<int>{}(42) == hash<E2>{}(E2::THIRD));
VERIFY(hash<int>{}(666) == hash<E2>{}(E2::FOURTH));
}