The C and C++ Include Header Files

/usr/include/c++/11/bits/stl_construct.h


$ cat -n /usr/include/c++/11/bits/stl_construct.h

     1	// nonstandard construct and destroy functions -*- C++ -*-
     2	
     3	// Copyright (C) 2001-2021 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	/*
    26	 *
    27	 * Copyright (c) 1994
    28	 * Hewlett-Packard Company
    29	 *
    30	 * Permission to use, copy, modify, distribute and sell this software
    31	 * and its documentation for any purpose is hereby granted without fee,
    32	 * provided that the above copyright notice appear in all copies and
    33	 * that both that copyright notice and this permission notice appear
    34	 * in supporting documentation.  Hewlett-Packard Company makes no
    35	 * representations about the suitability of this software for any
    36	 * purpose.  It is provided "as is" without express or implied warranty.
    37	 *
    38	 *
    39	 * Copyright (c) 1996,1997
    40	 * Silicon Graphics Computer Systems, Inc.
    41	 *
    42	 * Permission to use, copy, modify, distribute and sell this software
    43	 * and its documentation for any purpose is hereby granted without fee,
    44	 * provided that the above copyright notice appear in all copies and
    45	 * that both that copyright notice and this permission notice appear
    46	 * in supporting documentation.  Silicon Graphics makes no
    47	 * representations about the suitability of this software for any
    48	 * purpose.  It is provided "as is" without express or implied warranty.
    49	 */
    50	
    51	/** @file bits/stl_construct.h
    52	 *  This is an internal header file, included by other library headers.
    53	 *  Do not attempt to use it directly. @headername{memory}
    54	 */
    55	
    56	#ifndef _STL_CONSTRUCT_H
    57	#define _STL_CONSTRUCT_H 1
    58	
    59	#include <new>
    60	#include <bits/move.h>
    61	#include <bits/stl_iterator_base_types.h> // for iterator_traits
    62	#include <bits/stl_iterator_base_funcs.h> // for advance
    63	
    64	/* This file provides the C++17 functions std::destroy_at, std::destroy, and
    65	 * std::destroy_n, and the C++20 function std::construct_at.
    66	 * It also provides std::_Construct, std::_Destroy,and std::_Destroy_n functions
    67	 * which are defined in all standard modes and so can be used in C++98-14 code.
    68	 * The _Destroy functions will dispatch to destroy_at during constant
    69	 * evaluation, because calls to that function are intercepted by the compiler
    70	 * to allow use in constant expressions.
    71	 */
    72	
    73	namespace std _GLIBCXX_VISIBILITY(default)
    74	{
    75	_GLIBCXX_BEGIN_NAMESPACE_VERSION
    76	
    77	#if __cplusplus >= 201703L
    78	  template <typename _Tp>
    79	    _GLIBCXX20_CONSTEXPR inline void
    80	    destroy_at(_Tp* __location)
    81	    {
    82	      if constexpr (__cplusplus > 201703L && is_array_v<_Tp>)
    83		{
    84		  for (auto& __x : *__location)
    85		    std::destroy_at(std::__addressof(__x));
    86		}
    87	      else
    88		__location->~_Tp();
    89	    }
    90	
    91	#if __cplusplus >= 202002L
    92	  template<typename _Tp, typename... _Args>
    93	    constexpr auto
    94	    construct_at(_Tp* __location, _Args&&... __args)
    95	    noexcept(noexcept(::new((void*)0) _Tp(std::declval<_Args>()...)))
    96	    -> decltype(::new((void*)0) _Tp(std::declval<_Args>()...))
    97	    { return ::new((void*)__location) _Tp(std::forward<_Args>(__args)...); }
    98	#endif // C++20
    99	#endif// C++17
   100	
   101	  /**
   102	   * Constructs an object in existing memory by invoking an allocated
   103	   * object's constructor with an initializer.
   104	   */
   105	#if __cplusplus >= 201103L
   106	  template<typename _Tp, typename... _Args>
   107	    _GLIBCXX20_CONSTEXPR
   108	    inline void
   109	    _Construct(_Tp* __p, _Args&&... __args)
   110	    {
   111	#if __cplusplus >= 202002L && __has_builtin(__builtin_is_constant_evaluated)
   112	      if (__builtin_is_constant_evaluated())
   113		{
   114		  // Allow std::_Construct to be used in constant expressions.
   115		  std::construct_at(__p, std::forward<_Args>(__args)...);
   116		  return;
   117		}
   118	#endif
   119	      ::new((void*)__p) _Tp(std::forward<_Args>(__args)...);
   120	    }
   121	#else
   122	  template<typename _T1, typename _T2>
   123	    inline void
   124	    _Construct(_T1* __p, const _T2& __value)
   125	    {
   126	      // _GLIBCXX_RESOLVE_LIB_DEFECTS
   127	      // 402. wrong new expression in [some_]allocator::construct
   128	      ::new(static_cast<void*>(__p)) _T1(__value);
   129	    }
   130	#endif
   131	
   132	  template<typename _T1>
   133	    inline void
   134	    _Construct_novalue(_T1* __p)
   135	    { ::new((void*)__p) _T1; }
   136	
   137	  template<typename _ForwardIterator>
   138	    _GLIBCXX20_CONSTEXPR void
   139	    _Destroy(_ForwardIterator __first, _ForwardIterator __last);
   140	
   141	  /**
   142	   * Destroy the object pointed to by a pointer type.
   143	   */
   144	  template<typename _Tp>
   145	    _GLIBCXX14_CONSTEXPR inline void
   146	    _Destroy(_Tp* __pointer)
   147	    {
   148	#if __cplusplus > 201703L
   149	      std::destroy_at(__pointer);
   150	#else
   151	      __pointer->~_Tp();
   152	#endif
   153	    }
   154	
   155	  template<bool>
   156	    struct _Destroy_aux
   157	    {
   158	      template<typename _ForwardIterator>
   159		static _GLIBCXX20_CONSTEXPR void
   160		__destroy(_ForwardIterator __first, _ForwardIterator __last)
   161		{
   162		  for (; __first != __last; ++__first)
   163		    std::_Destroy(std::__addressof(*__first));
   164		}
   165	    };
   166	
   167	  template<>
   168	    struct _Destroy_aux<true>
   169	    {
   170	      template<typename _ForwardIterator>
   171	        static void
   172	        __destroy(_ForwardIterator, _ForwardIterator) { }
   173	    };
   174	
   175	  /**
   176	   * Destroy a range of objects.  If the value_type of the object has
   177	   * a trivial destructor, the compiler should optimize all of this
   178	   * away, otherwise the objects' destructors must be invoked.
   179	   */
   180	  template<typename _ForwardIterator>
   181	    _GLIBCXX20_CONSTEXPR inline void
   182	    _Destroy(_ForwardIterator __first, _ForwardIterator __last)
   183	    {
   184	      typedef typename iterator_traits<_ForwardIterator>::value_type
   185	                       _Value_type;
   186	#if __cplusplus >= 201103L
   187	      // A deleted destructor is trivial, this ensures we reject such types:
   188	      static_assert(is_destructible<_Value_type>::value,
   189			    "value type is destructible");
   190	#endif
   191	#if __cplusplus > 201703L && defined __cpp_lib_is_constant_evaluated
   192	      if (std::is_constant_evaluated())
   193		return _Destroy_aux<false>::__destroy(__first, __last);
   194	#endif
   195	      std::_Destroy_aux<__has_trivial_destructor(_Value_type)>::
   196		__destroy(__first, __last);
   197	    }
   198	
   199	  template<bool>
   200	    struct _Destroy_n_aux
   201	    {
   202	      template<typename _ForwardIterator, typename _Size>
   203		static _GLIBCXX20_CONSTEXPR _ForwardIterator
   204		__destroy_n(_ForwardIterator __first, _Size __count)
   205		{
   206		  for (; __count > 0; (void)++__first, --__count)
   207		    std::_Destroy(std::__addressof(*__first));
   208		  return __first;
   209		}
   210	    };
   211	
   212	  template<>
   213	    struct _Destroy_n_aux<true>
   214	    {
   215	      template<typename _ForwardIterator, typename _Size>
   216	        static _ForwardIterator
   217	        __destroy_n(_ForwardIterator __first, _Size __count)
   218		{
   219		  std::advance(__first, __count);
   220		  return __first;
   221		}
   222	    };
   223	
   224	  /**
   225	   * Destroy a range of objects.  If the value_type of the object has
   226	   * a trivial destructor, the compiler should optimize all of this
   227	   * away, otherwise the objects' destructors must be invoked.
   228	   */
   229	  template<typename _ForwardIterator, typename _Size>
   230	    _GLIBCXX20_CONSTEXPR inline _ForwardIterator
   231	    _Destroy_n(_ForwardIterator __first, _Size __count)
   232	    {
   233	      typedef typename iterator_traits<_ForwardIterator>::value_type
   234	                       _Value_type;
   235	#if __cplusplus >= 201103L
   236	      // A deleted destructor is trivial, this ensures we reject such types:
   237	      static_assert(is_destructible<_Value_type>::value,
   238			    "value type is destructible");
   239	#endif
   240	#if __cplusplus > 201703L && defined __cpp_lib_is_constant_evaluated
   241	      if (std::is_constant_evaluated())
   242		return _Destroy_n_aux<false>::__destroy_n(__first, __count);
   243	#endif
   244	      return std::_Destroy_n_aux<__has_trivial_destructor(_Value_type)>::
   245		__destroy_n(__first, __count);
   246	    }
   247	
   248	#if __cplusplus >= 201703L
   249	  template <typename _ForwardIterator>
   250	    _GLIBCXX20_CONSTEXPR inline void
   251	    destroy(_ForwardIterator __first, _ForwardIterator __last)
   252	    {
   253	      std::_Destroy(__first, __last);
   254	    }
   255	
   256	  template <typename _ForwardIterator, typename _Size>
   257	    _GLIBCXX20_CONSTEXPR inline _ForwardIterator
   258	    destroy_n(_ForwardIterator __first, _Size __count)
   259	    {
   260	      return std::_Destroy_n(__first, __count);
   261	    }
   262	#endif // C++17
   263	
   264	_GLIBCXX_END_NAMESPACE_VERSION
   265	} // namespace std
   266	
   267	#endif /* _STL_CONSTRUCT_H */