Preview: move_only_function.h
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/opt/rh/gcc-toolset-14/root/usr/include/c++/14/bits/move_only_function.h
// Implementation of std::move_only_function -*- C++ -*-
// Copyright The GNU Toolchain Authors.
//
// 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.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
/** @file include/bits/move_only_function.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @headername{functional}
*/
#ifndef _GLIBCXX_MOVE_ONLY_FUNCTION_H
#define _GLIBCXX_MOVE_ONLY_FUNCTION_H 1
#pragma GCC system_header
#include <bits/version.h>
#ifdef __glibcxx_move_only_function // C++ >= 23 && HOSTED
#include <bits/invoke.h>
#include <bits/utility.h>
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename... _Signature>
class move_only_function; // not defined
/// @cond undocumented
class _Mofunc_base
{
protected:
_Mofunc_base() noexcept
: _M_manage(_S_empty)
{ }
_Mofunc_base(_Mofunc_base&& __x) noexcept
{
_M_manage = std::__exchange(__x._M_manage, _S_empty);
_M_manage(_M_storage, &__x._M_storage);
}
template<typename _Tp, typename... _Args>
static constexpr bool
_S_nothrow_init() noexcept
{
if constexpr (__stored_locally<_Tp>)
return is_nothrow_constructible_v<_Tp, _Args...>;
return false;
}
template<typename _Tp, typename... _Args>
void
_M_init(_Args&&... __args) noexcept(_S_nothrow_init<_Tp, _Args...>())
{
if constexpr (__stored_locally<_Tp>)
::new (_M_storage._M_addr()) _Tp(std::forward<_Args>(__args)...);
else
_M_storage._M_p = new _Tp(std::forward<_Args>(__args)...);
_M_manage = &_S_manage<_Tp>;
}
_Mofunc_base&
operator=(_Mofunc_base&& __x) noexcept
{
_M_manage(_M_storage, nullptr);
_M_manage = std::__exchange(__x._M_manage, _S_empty);
_M_manage(_M_storage, &__x._M_storage);
return *this;
}
_Mofunc_base&
operator=(nullptr_t) noexcept
{
_M_manage(_M_storage, nullptr);
_M_manage = _S_empty;
return *this;
}
~_Mofunc_base() { _M_manage(_M_storage, nullptr); }
void
swap(_Mofunc_base& __x) noexcept
{
// Order of operations here is more efficient if __x is empty.
_Storage __s;
__x._M_manage(__s, &__x._M_storage);
_M_manage(__x._M_storage, &_M_storage);
__x._M_manage(_M_storage, &__s);
std::swap(_M_manage, __x._M_manage);
}
template<typename _Tp, typename _Self>
static _Tp*
_S_access(_Self* __self) noexcept
{
if constexpr (__stored_locally<remove_const_t<_Tp>>)
return static_cast<_Tp*>(__self->_M_storage._M_addr());
else
return static_cast<_Tp*>(__self->_M_storage._M_p);
}
private:
struct _Storage
{
void* _M_addr() noexcept { return &_M_bytes[0]; }
const void* _M_addr() const noexcept { return &_M_bytes[0]; }
// We want to have enough space to store a simple delegate type.
struct _Delegate { void (_Storage::*__pfm)(); _Storage* __obj; };
union {
void* _M_p;
alignas(_Delegate) alignas(void(*)())
unsigned char _M_bytes[sizeof(_Delegate)];
};
};
template<typename _Tp>
static constexpr bool __stored_locally
= sizeof(_Tp) <= sizeof(_Storage) && alignof(_Tp) <= alignof(_Storage)
&& is_nothrow_move_constructible_v<_Tp>;
// A function that either destroys the target object stored in __target,
// or moves the target object from *__src to __target.
using _Manager = void (*)(_Storage& __target, _Storage* __src) noexcept;
// The no-op manager function for objects with no target.
static void _S_empty(_Storage&, _Storage*) noexcept { }
// The real manager function for a target object of type _Tp.
template<typename _Tp>
static void
_S_manage(_Storage& __target, _Storage* __src) noexcept
{
if constexpr (__stored_locally<_Tp>)
{
if (__src)
{
_Tp* __rval = static_cast<_Tp*>(__src->_M_addr());
::new (__target._M_addr()) _Tp(std::move(*__rval));
__rval->~_Tp();
}
else
static_cast<_Tp*>(__target._M_addr())->~_Tp();
}
else
{
if (__src)
__target._M_p = __src->_M_p;
else
delete static_cast<_Tp*>(__target._M_p);
}
}
_Storage _M_storage;
_Manager _M_manage;
};
template<typename _Tp>
inline constexpr bool __is_move_only_function_v = false;
template<typename _Tp>
constexpr bool __is_move_only_function_v<move_only_function<_Tp>> = true;
/// @endcond
namespace __detail::__variant
{
template<typename> struct _Never_valueless_alt; // see <variant>
// Provide the strong exception-safety guarantee when emplacing a
// move_only_function into a variant.
template<typename... _Signature>
struct _Never_valueless_alt<std::move_only_function<_Signature...>>
: true_type
{ };
} // namespace __detail::__variant
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#include "mofunc_impl.h"
#define _GLIBCXX_MOF_CV const
#include "mofunc_impl.h"
#define _GLIBCXX_MOF_REF &
#include "mofunc_impl.h"
#define _GLIBCXX_MOF_REF &&
#include "mofunc_impl.h"
#define _GLIBCXX_MOF_CV const
#define _GLIBCXX_MOF_REF &
#include "mofunc_impl.h"
#define _GLIBCXX_MOF_CV const
#define _GLIBCXX_MOF_REF &&
#include "mofunc_impl.h"
#endif // __glibcxx_move_only_function
#endif // _GLIBCXX_MOVE_ONLY_FUNCTION_H
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