[thirdparty/gcc.git] / libstdc++-v3 / include / bits / move.h

// Move, forward and identity for C++11 + swap -*- C++ -*-

// Copyright (C) 2007-2025 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.

// 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 bits/move.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{utility}
 */

#ifndef _MOVE_H
#define _MOVE_H 1

#include <bits/c++config.h>
#if __cplusplus < 201103L
# include <bits/concept_check.h>
#else
# include <type_traits> // Brings in std::declval too.
#endif

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  // Used, in C++03 mode too, by allocators, etc.
  /**
   *  @brief Same as C++11 std::addressof
   *  @ingroup utilities
   */
  template<typename _Tp>
    __attribute__((__always_inline__))
    inline _GLIBCXX_CONSTEXPR _Tp*
    __addressof(_Tp& __r) _GLIBCXX_NOEXCEPT
    { return __builtin_addressof(__r); }

#if __cplusplus >= 201103L

  /**
   *  @addtogroup utilities
   *  @{
   */

  /**
   *  @brief  Forward an lvalue.
   *  @return The parameter cast to the specified type.
   *
   *  This function is used to implement "perfect forwarding".
   *  @since C++11
   */
  template<typename _Tp>
    [[__nodiscard__,__gnu__::__always_inline__]]
    constexpr _Tp&&
    forward(typename std::remove_reference<_Tp>::type& __t) noexcept
    { return static_cast<_Tp&&>(__t); }

  /**
   *  @brief  Forward an rvalue.
   *  @return The parameter cast to the specified type.
   *
   *  This function is used to implement "perfect forwarding".
   *  @since C++11
   */
  template<typename _Tp>
    [[__nodiscard__,__gnu__::__always_inline__]]
    constexpr _Tp&&
    forward(typename std::remove_reference<_Tp>::type&& __t) noexcept
    {
      static_assert(!std::is_lvalue_reference<_Tp>::value,
	  "std::forward must not be used to convert an rvalue to an lvalue");
      return static_cast<_Tp&&>(__t);
    }

  template<typename _Tp, typename _Up>
  struct __like_impl; // _Tp must be a reference and _Up an lvalue reference

  template<typename _Tp, typename _Up>
  struct __like_impl<_Tp&, _Up&>
  { using type = _Up&; };

  template<typename _Tp, typename _Up>
  struct __like_impl<const _Tp&, _Up&>
  { using type = const _Up&; };

  template<typename _Tp, typename _Up>
  struct __like_impl<_Tp&&, _Up&>
  { using type = _Up&&; };

  template<typename _Tp, typename _Up>
  struct __like_impl<const _Tp&&, _Up&>
  { using type = const _Up&&; };

  template<typename _Tp, typename _Up>
    using __like_t = typename __like_impl<_Tp&&, _Up&>::type;

#if __glibcxx_forward_like // C++ >= 23
  /** @brief Forward with the cv-qualifiers and value category of another type.
   *  @tparam _Tp An lvalue reference or rvalue reference.
   *  @tparam _Up An lvalue reference type deduced from the function argument.
   *  @param __x An lvalue.
   *  @return `__x` converted to match the qualifiers of `_Tp`.
   *  @since C++23
   */
  template<typename _Tp, typename _Up>
  [[nodiscard,__gnu__::__always_inline__]]
  constexpr __like_t<_Tp, _Up>
  forward_like(_Up&& __x) noexcept
  { return static_cast<__like_t<_Tp, _Up>>(__x); }
#endif

  /**
   *  @brief  Convert a value to an rvalue.
   *  @param  __t  A thing of arbitrary type.
   *  @return The parameter cast to an rvalue-reference to allow moving it.
   *  @since C++11
  */
  template<typename _Tp>
    [[__nodiscard__,__gnu__::__always_inline__]]
    constexpr typename std::remove_reference<_Tp>::type&&
    move(_Tp&& __t) noexcept
    { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }


  template<typename _Tp>
    struct __move_if_noexcept_cond
    : public __and_<__not_<is_nothrow_move_constructible<_Tp>>,
                    is_copy_constructible<_Tp>>::type { };

  /**
   *  @brief  Conditionally convert a value to an rvalue.
   *  @param  __x  A thing of arbitrary type.
   *  @return The parameter, possibly cast to an rvalue-reference.
   *
   *  Same as std::move unless the type's move constructor could throw and the
   *  type is copyable, in which case an lvalue-reference is returned instead.
   *  @since C++11
   */
  template<typename _Tp>
    [[__nodiscard__,__gnu__::__always_inline__]]
    constexpr
    __conditional_t<__move_if_noexcept_cond<_Tp>::value, const _Tp&, _Tp&&>
    move_if_noexcept(_Tp& __x) noexcept
    { return std::move(__x); }

  // declval, from type_traits.

  /**
   *  @brief Returns the actual address of the object or function
   *         referenced by r, even in the presence of an overloaded
   *         operator&.
   *  @param  __r  Reference to an object or function.
   *  @return   The actual address.
   *  @since C++11
  */
  template<typename _Tp>
    [[__nodiscard__,__gnu__::__always_inline__]]
    inline _GLIBCXX17_CONSTEXPR _Tp*
    addressof(_Tp& __r) noexcept
    { return __builtin_addressof(__r); }

  // _GLIBCXX_RESOLVE_LIB_DEFECTS
  // 2598. addressof works on temporaries
  template<typename _Tp>
    const _Tp* addressof(const _Tp&&) = delete;

  // C++11 version of std::exchange for internal use.
  template <typename _Tp, typename _Up = _Tp>
    _GLIBCXX20_CONSTEXPR
    inline _Tp
    __exchange(_Tp& __obj, _Up&& __new_val)
    {
      _Tp __old_val = std::move(__obj);
      __obj = std::forward<_Up>(__new_val);
      return __old_val;
    }

  /// @} group utilities

#define _GLIBCXX_FWDREF(_Tp) _Tp&&
#define _GLIBCXX_MOVE(__val) std::move(__val)
#define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val)
#else
#define _GLIBCXX_FWDREF(_Tp) const _Tp&
#define _GLIBCXX_MOVE(__val) (__val)
#define _GLIBCXX_FORWARD(_Tp, __val) (__val)
#endif

  /**
   *  @addtogroup utilities
   *  @{
   */

  /**
   *  @brief Swaps two values.
   *  @param  __a  A thing of arbitrary type.
   *  @param  __b  Another thing of arbitrary type.
   *  @return   Nothing.
  */
  template<typename _Tp>
#if __glibcxx_concepts // >= C++20
    requires (! __is_tuple_like<_Tp>::value)
      && is_move_constructible_v<_Tp>
      && is_move_assignable_v<_Tp>
    constexpr void
#elif __cplusplus >= 201103L
    _GLIBCXX20_CONSTEXPR inline
    __enable_if_t<__and_<__not_<__is_tuple_like<_Tp>>,
			 is_move_constructible<_Tp>,
			 is_move_assignable<_Tp>>::value>
#else
    inline void
#endif
    swap(_Tp& __a, _Tp& __b)
    _GLIBCXX_NOEXCEPT_IF(__and_<is_nothrow_move_constructible<_Tp>,
				is_nothrow_move_assignable<_Tp>>::value)
    {
#if __cplusplus < 201103L
      // concept requirements
      __glibcxx_function_requires(_SGIAssignableConcept<_Tp>)
#endif
      _Tp __tmp = _GLIBCXX_MOVE(__a);
      __a = _GLIBCXX_MOVE(__b);
      __b = _GLIBCXX_MOVE(__tmp);
    }

  // _GLIBCXX_RESOLVE_LIB_DEFECTS
  // DR 809. std::swap should be overloaded for array types.
  /// Swap the contents of two arrays.
  template<typename _Tp, size_t _Nm>
#if __glibcxx_concepts // >= C++20
    requires is_swappable_v<_Tp>
    constexpr void
#elif __cplusplus >= 201103L
    _GLIBCXX20_CONSTEXPR inline
    __enable_if_t<__is_swappable<_Tp>::value>
#else
    inline void
#endif
    swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
    _GLIBCXX_NOEXCEPT_IF(__is_nothrow_swappable<_Tp>::value)
    {
      for (size_t __n = 0; __n < _Nm; ++__n)
	swap(__a[__n], __b[__n]);
    }

  /// @} group utilities
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace

#endif /* _MOVE_H */
Commit	Line	Data
	1	// Move, forward and identity for C++11 + swap -- C++ --
	2
	3	// Copyright (C) 2007-2025 Free Software Foundation, Inc.
	4	//
	5	// This file is part of the GNU ISO C++ Library. This library is free
	6	// software; you can redistribute it and/or modify it under the
	7	// terms of the GNU General Public License as published by the
	8	// Free Software Foundation; either version 3, or (at your option)
	9	// any later version.
	10
	11	// This library is distributed in the hope that it will be useful,
	12	// but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	14	// GNU General Public License for more details.
	15
	16	// Under Section 7 of GPL version 3, you are granted additional
	17	// permissions described in the GCC Runtime Library Exception, version
	18	// 3.1, as published by the Free Software Foundation.
	19
	20	// You should have received a copy of the GNU General Public License and
	21	// a copy of the GCC Runtime Library Exception along with this program;
	22	// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
	23	// <http://www.gnu.org/licenses/>.
	24
	25	/** @file bits/move.h
	26	* This is an internal header file, included by other library headers.
	27	* Do not attempt to use it directly. @headername{utility}
	28	*/
	29
	30	#ifndef _MOVE_H
	31	#define _MOVE_H 1
	32
	33	#include <bits/c++config.h>
	34	#if __cplusplus < 201103L
	35	# include <bits/concept_check.h>
	36	#else
	37	# include <type_traits> // Brings in std::declval too.
	38	#endif
	39
	40	namespace std _GLIBCXX_VISIBILITY(default)
	41	{
	42	_GLIBCXX_BEGIN_NAMESPACE_VERSION
	43
	44	// Used, in C++03 mode too, by allocators, etc.
	45	/**
	46	* @brief Same as C++11 std::addressof
	47	* @ingroup utilities
	48	*/
	49	template<typename _Tp>
	50	__attribute__((__always_inline__))
	51	inline _GLIBCXX_CONSTEXPR _Tp*
	52	__addressof(_Tp& __r) _GLIBCXX_NOEXCEPT
	53	{ return __builtin_addressof(__r); }
	54
	55	#if __cplusplus >= 201103L
	56
	57	/**
	58	* @addtogroup utilities
	59	* @{
	60	*/
	61
	62	/**
	63	* @brief Forward an lvalue.
	64	* @return The parameter cast to the specified type.
	65	*
	66	* This function is used to implement "perfect forwarding".
	67	* @since C++11
	68	*/
	69	template<typename _Tp>
	70	[[__nodiscard__,__gnu__::__always_inline__]]
	71	constexpr _Tp&&
	72	forward(typename std::remove_reference<_Tp>::type& __t) noexcept
	73	{ return static_cast<_Tp&&>(__t); }
	74
	75	/**
	76	* @brief Forward an rvalue.
	77	* @return The parameter cast to the specified type.
	78	*
	79	* This function is used to implement "perfect forwarding".
	80	* @since C++11
	81	*/
	82	template<typename _Tp>
	83	[[__nodiscard__,__gnu__::__always_inline__]]
	84	constexpr _Tp&&
	85	forward(typename std::remove_reference<_Tp>::type&& __t) noexcept
	86	{
	87	static_assert(!std::is_lvalue_reference<_Tp>::value,
	88	"std::forward must not be used to convert an rvalue to an lvalue");
	89	return static_cast<_Tp&&>(__t);
	90	}
	91
	92	template<typename _Tp, typename _Up>
	93	struct __like_impl; // _Tp must be a reference and _Up an lvalue reference
	94
	95	template<typename _Tp, typename _Up>
	96	struct __like_impl<_Tp&, _Up&>
	97	{ using type = _Up&; };
	98
	99	template<typename _Tp, typename _Up>
	100	struct __like_impl<const _Tp&, _Up&>
	101	{ using type = const _Up&; };
	102
	103	template<typename _Tp, typename _Up>
	104	struct __like_impl<_Tp&&, _Up&>
	105	{ using type = _Up&&; };
	106
	107	template<typename _Tp, typename _Up>
	108	struct __like_impl<const _Tp&&, _Up&>
	109	{ using type = const _Up&&; };
	110
	111	template<typename _Tp, typename _Up>
	112	using __like_t = typename __like_impl<_Tp&&, _Up&>::type;
	113
	114	#if __glibcxx_forward_like // C++ >= 23
	115	/** @brief Forward with the cv-qualifiers and value category of another type.
	116	* @tparam _Tp An lvalue reference or rvalue reference.
	117	* @tparam _Up An lvalue reference type deduced from the function argument.
	118	* @param __x An lvalue.
	119	* @return `__x` converted to match the qualifiers of `_Tp`.
	120	* @since C++23
	121	*/
	122	template<typename _Tp, typename _Up>
	123	[[nodiscard,__gnu__::__always_inline__]]
	124	constexpr __like_t<_Tp, _Up>
	125	forward_like(_Up&& __x) noexcept
	126	{ return static_cast<__like_t<_Tp, _Up>>(__x); }
	127	#endif
	128
	129	/**
	130	* @brief Convert a value to an rvalue.
	131	* @param __t A thing of arbitrary type.
	132	* @return The parameter cast to an rvalue-reference to allow moving it.
	133	* @since C++11
	134	*/
	135	template<typename _Tp>
	136	[[__nodiscard__,__gnu__::__always_inline__]]
	137	constexpr typename std::remove_reference<_Tp>::type&&
	138	move(_Tp&& __t) noexcept
	139	{ return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }
	140
	141
	142	template<typename _Tp>
	143	struct __move_if_noexcept_cond
	144	: public __and_<__not_<is_nothrow_move_constructible<_Tp>>,
	145	is_copy_constructible<_Tp>>::type { };
	146
	147	/**
	148	* @brief Conditionally convert a value to an rvalue.
	149	* @param __x A thing of arbitrary type.
	150	* @return The parameter, possibly cast to an rvalue-reference.
	151	*
	152	* Same as std::move unless the type's move constructor could throw and the
	153	* type is copyable, in which case an lvalue-reference is returned instead.
	154	* @since C++11
	155	*/
	156	template<typename _Tp>
	157	[[__nodiscard__,__gnu__::__always_inline__]]
	158	constexpr
	159	__conditional_t<__move_if_noexcept_cond<_Tp>::value, const _Tp&, _Tp&&>
	160	move_if_noexcept(_Tp& __x) noexcept
	161	{ return std::move(__x); }
	162
	163	// declval, from type_traits.
	164
	165	/**
	166	* @brief Returns the actual address of the object or function
	167	* referenced by r, even in the presence of an overloaded
	168	* operator&.
	169	* @param __r Reference to an object or function.
	170	* @return The actual address.
	171	* @since C++11
	172	*/
	173	template<typename _Tp>
	174	[[__nodiscard__,__gnu__::__always_inline__]]
	175	inline _GLIBCXX17_CONSTEXPR _Tp*
	176	addressof(_Tp& __r) noexcept
	177	{ return __builtin_addressof(__r); }
	178
	179	// _GLIBCXX_RESOLVE_LIB_DEFECTS
	180	// 2598. addressof works on temporaries
	181	template<typename _Tp>
	182	const _Tp* addressof(const _Tp&&) = delete;
	183
	184	// C++11 version of std::exchange for internal use.
	185	template <typename _Tp, typename _Up = _Tp>
	186	_GLIBCXX20_CONSTEXPR
	187	inline _Tp
	188	__exchange(_Tp& __obj, _Up&& __new_val)
	189	{
	190	_Tp __old_val = std::move(__obj);
	191	__obj = std::forward<_Up>(__new_val);
	192	return __old_val;
	193	}
	194
	195	/// @} group utilities
	196
	197	#define _GLIBCXX_FWDREF(_Tp) _Tp&&
	198	#define _GLIBCXX_MOVE(__val) std::move(__val)
	199	#define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val)
	200	#else
	201	#define _GLIBCXX_FWDREF(_Tp) const _Tp&
	202	#define _GLIBCXX_MOVE(__val) (__val)
	203	#define _GLIBCXX_FORWARD(_Tp, __val) (__val)
	204	#endif
	205
	206	/**
	207	* @addtogroup utilities
	208	* @{
	209	*/
	210
	211	/**
	212	* @brief Swaps two values.
	213	* @param __a A thing of arbitrary type.
	214	* @param __b Another thing of arbitrary type.
	215	* @return Nothing.
	216	*/
	217	template<typename _Tp>
	218	#if __glibcxx_concepts // >= C++20
	219	requires (! __is_tuple_like<_Tp>::value)
	220	&& is_move_constructible_v<_Tp>
	221	&& is_move_assignable_v<_Tp>
	222	constexpr void
	223	#elif __cplusplus >= 201103L
	224	_GLIBCXX20_CONSTEXPR inline
	225	__enable_if_t<__and_<__not_<__is_tuple_like<_Tp>>,
	226	is_move_constructible<_Tp>,
	227	is_move_assignable<_Tp>>::value>
	228	#else
	229	inline void
	230	#endif
	231	swap(_Tp& __a, _Tp& __b)
	232	_GLIBCXX_NOEXCEPT_IF(__and_<is_nothrow_move_constructible<_Tp>,
	233	is_nothrow_move_assignable<_Tp>>::value)
	234	{
	235	#if __cplusplus < 201103L
	236	// concept requirements
	237	__glibcxx_function_requires(_SGIAssignableConcept<_Tp>)
	238	#endif
	239	_Tp __tmp = _GLIBCXX_MOVE(__a);
	240	__a = _GLIBCXX_MOVE(__b);
	241	__b = _GLIBCXX_MOVE(__tmp);
	242	}
	243
	244	// _GLIBCXX_RESOLVE_LIB_DEFECTS
	245	// DR 809. std::swap should be overloaded for array types.
	246	/// Swap the contents of two arrays.
	247	template<typename _Tp, size_t _Nm>
	248	#if __glibcxx_concepts // >= C++20
	249	requires is_swappable_v<_Tp>
	250	constexpr void
	251	#elif __cplusplus >= 201103L
	252	_GLIBCXX20_CONSTEXPR inline
	253	__enable_if_t<__is_swappable<_Tp>::value>
	254	#else
	255	inline void
	256	#endif
	257	swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
	258	_GLIBCXX_NOEXCEPT_IF(__is_nothrow_swappable<_Tp>::value)
	259	{
	260	for (size_t __n = 0; __n < _Nm; ++__n)
	261	swap(__a[__n], __b[__n]);
	262	}
	263
	264	/// @} group utilities
	265	_GLIBCXX_END_NAMESPACE_VERSION
	266	} // namespace
	267
	268	#endif /* _MOVE_H */