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[libc++][NFC] Move monostate to its own header. 

The format library uses `std::monostate`, but not a `std::variant`.
Moving `std::monostate` to its own header allows the format library to
reduce the amount of included code.

Reviewed By: #libc, ldionne

Differential Revision: https://reviews.llvm.org/D105582
This commit is contained in:
Mark de Wever 2021-07-07 21:27:27 +02:00
parent 4947ecf4e9
commit 321c2ea91c
4 changed files with 71 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
libcxx/include/CMakeLists.txt
View File

@ -237,6 +237,7 @@ set(files
__utility/rel_ops.h
__utility/swap.h
__utility/to_underlying.h
__variant/monostate.h
algorithm
any
array

65
libcxx/include/__variant/monostate.h Normal file
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@ -0,0 +1,65 @@
// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___VARIANT_MONOSTATE_H
#define _LIBCPP___VARIANT_MONOSTATE_H
#include <__config>
#include <__functional/hash.h>
#include <cstddef>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif
_LIBCPP_PUSH_MACROS
#include <__undef_macros>
_LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER > 14
struct _LIBCPP_TEMPLATE_VIS monostate {};
inline _LIBCPP_INLINE_VISIBILITY
constexpr bool operator<(monostate, monostate) noexcept { return false; }
inline _LIBCPP_INLINE_VISIBILITY
constexpr bool operator>(monostate, monostate) noexcept { return false; }
inline _LIBCPP_INLINE_VISIBILITY
constexpr bool operator<=(monostate, monostate) noexcept { return true; }
inline _LIBCPP_INLINE_VISIBILITY
constexpr bool operator>=(monostate, monostate) noexcept { return true; }
inline _LIBCPP_INLINE_VISIBILITY
constexpr bool operator==(monostate, monostate) noexcept { return true; }
inline _LIBCPP_INLINE_VISIBILITY
constexpr bool operator!=(monostate, monostate) noexcept { return false; }
template <>
struct _LIBCPP_TEMPLATE_VIS hash<monostate> {
using argument_type = monostate;
using result_type = size_t;
inline _LIBCPP_INLINE_VISIBILITY
result_type operator()(const argument_type&) const _NOEXCEPT {
return 66740831; // return a fundamentally attractive random value.
}
};
#endif // _LIBCPP_STD_VER > 14
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP___VARIANT_MONOSTATE_H

4
libcxx/include/module.modulemap
View File

@ -735,6 +735,10 @@ module std [system] {
module variant {
header "variant"
export *
module __variant {
module monostate { header "__variant/monostate.h" }
}
}
module vector {
header "vector"

32
libcxx/include/variant
View File

@ -202,6 +202,7 @@ namespace std {
#include <__availability>
#include <__config>
#include <__utility/forward.h>
#include <__variant/monostate.h>
#include <__tuple>
#include <array>
#include <compare>
@ -1703,26 +1704,6 @@ inline _LIBCPP_INLINE_VISIBILITY
}
#endif
struct _LIBCPP_TEMPLATE_VIS monostate {};
inline _LIBCPP_INLINE_VISIBILITY
constexpr bool operator<(monostate, monostate) noexcept { return false; }
inline _LIBCPP_INLINE_VISIBILITY
constexpr bool operator>(monostate, monostate) noexcept { return false; }
inline _LIBCPP_INLINE_VISIBILITY
constexpr bool operator<=(monostate, monostate) noexcept { return true; }
inline _LIBCPP_INLINE_VISIBILITY
constexpr bool operator>=(monostate, monostate) noexcept { return true; }
inline _LIBCPP_INLINE_VISIBILITY
constexpr bool operator==(monostate, monostate) noexcept { return true; }
inline _LIBCPP_INLINE_VISIBILITY
constexpr bool operator!=(monostate, monostate) noexcept { return false; }
template <class... _Types>
inline _LIBCPP_INLINE_VISIBILITY
auto swap(variant<_Types...>& __lhs,
@ -1755,17 +1736,6 @@ struct _LIBCPP_TEMPLATE_VIS hash<
}
};
template <>
struct _LIBCPP_TEMPLATE_VIS hash<monostate> {
using argument_type = monostate;
using result_type = size_t;
inline _LIBCPP_INLINE_VISIBILITY
result_type operator()(const argument_type&) const _NOEXCEPT {
return 66740831; // return a fundamentally attractive random value.
}
};
#endif // _LIBCPP_STD_VER > 14
_LIBCPP_END_NAMESPACE_STD