// Allocator traits -*- C++ -*-
-// Copyright (C) 2011-2017 Free Software Foundation, Inc.
+// Copyright (C) 2011-2024 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
#ifndef _ALLOC_TRAITS_H
#define _ALLOC_TRAITS_H 1
-#if __cplusplus >= 201103L
-
+#include <bits/stl_construct.h>
#include <bits/memoryfwd.h>
-#include <bits/ptr_traits.h>
-#include <ext/numeric_traits.h>
-
-#define __cpp_lib_allocator_traits_is_always_equal 201411
+#if __cplusplus >= 201103L
+# include <bits/ptr_traits.h>
+# include <ext/numeric_traits.h>
+# if _GLIBCXX_HOSTED
+# include <bits/allocator.h>
+# endif
+#endif
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
+#if __cplusplus >= 201103L
+ /// @cond undocumented
struct __allocator_traits_base
{
template<typename _Tp, typename _Up, typename = void>
- struct __rebind : __replace_first_arg<_Tp, _Up> { };
+ struct __rebind : __replace_first_arg<_Tp, _Up>
+ {
+ static_assert(is_same<
+ typename __replace_first_arg<_Tp, typename _Tp::value_type>::type,
+ _Tp>::value,
+ "allocator_traits<A>::rebind_alloc<A::value_type> must be A");
+ };
template<typename _Tp, typename _Up>
struct __rebind<_Tp, _Up,
__void_t<typename _Tp::template rebind<_Up>::other>>
- { using type = typename _Tp::template rebind<_Up>::other; };
+ {
+ using type = typename _Tp::template rebind<_Up>::other;
+
+ static_assert(is_same<
+ typename _Tp::template rebind<typename _Tp::value_type>::other,
+ _Tp>::value,
+ "allocator_traits<A>::rebind_alloc<A::value_type> must be A");
+ };
protected:
template<typename _Tp>
template<typename _Tp>
using __pocs = typename _Tp::propagate_on_container_swap;
template<typename _Tp>
- using __equal = typename _Tp::is_always_equal;
+ using __equal = __type_identity<typename _Tp::is_always_equal>;
};
template<typename _Alloc, typename _Up>
using __alloc_rebind
= typename __allocator_traits_base::template __rebind<_Alloc, _Up>::type;
+ /// @endcond
/**
* @brief Uniform interface to all allocator types.
+ * @headerfile memory
* @ingroup allocators
+ * @since C++11
*/
template<typename _Alloc>
struct allocator_traits : __allocator_traits_base
* otherwise @c is_empty<Alloc>::type
*/
using is_always_equal
- = __detected_or_t<typename is_empty<_Alloc>::type, __equal, _Alloc>;
+ = typename __detected_or_t<is_empty<_Alloc>, __equal, _Alloc>::type;
template<typename _Tp>
using rebind_alloc = __alloc_rebind<_Alloc, _Tp>;
private:
template<typename _Alloc2>
- static auto
+ static constexpr auto
_S_allocate(_Alloc2& __a, size_type __n, const_void_pointer __hint, int)
-> decltype(__a.allocate(__n, __hint))
{ return __a.allocate(__n, __hint); }
template<typename _Alloc2>
- static pointer
+ static constexpr pointer
_S_allocate(_Alloc2& __a, size_type __n, const_void_pointer, ...)
{ return __a.allocate(__n); }
= typename __construct_helper<_Tp, _Args...>::type;
template<typename _Tp, typename... _Args>
- static _Require<__has_construct<_Tp, _Args...>>
+ static _GLIBCXX14_CONSTEXPR _Require<__has_construct<_Tp, _Args...>>
_S_construct(_Alloc& __a, _Tp* __p, _Args&&... __args)
+ noexcept(noexcept(__a.construct(__p, std::forward<_Args>(__args)...)))
{ __a.construct(__p, std::forward<_Args>(__args)...); }
template<typename _Tp, typename... _Args>
- static
+ static _GLIBCXX14_CONSTEXPR
_Require<__and_<__not_<__has_construct<_Tp, _Args...>>,
is_constructible<_Tp, _Args...>>>
_S_construct(_Alloc&, _Tp* __p, _Args&&... __args)
- { ::new((void*)__p) _Tp(std::forward<_Args>(__args)...); }
+ noexcept(std::is_nothrow_constructible<_Tp, _Args...>::value)
+ {
+#if __cplusplus <= 201703L
+ ::new((void*)__p) _Tp(std::forward<_Args>(__args)...);
+#else
+ std::construct_at(__p, std::forward<_Args>(__args)...);
+#endif
+ }
template<typename _Alloc2, typename _Tp>
- static auto
+ static _GLIBCXX14_CONSTEXPR auto
_S_destroy(_Alloc2& __a, _Tp* __p, int)
+ noexcept(noexcept(__a.destroy(__p)))
-> decltype(__a.destroy(__p))
{ __a.destroy(__p); }
template<typename _Alloc2, typename _Tp>
- static void
+ static _GLIBCXX14_CONSTEXPR void
_S_destroy(_Alloc2&, _Tp* __p, ...)
- { __p->~_Tp(); }
+ noexcept(std::is_nothrow_destructible<_Tp>::value)
+ { std::_Destroy(__p); }
template<typename _Alloc2>
- static auto
+ static constexpr auto
_S_max_size(_Alloc2& __a, int)
-> decltype(__a.max_size())
{ return __a.max_size(); }
template<typename _Alloc2>
- static size_type
+ static constexpr size_type
_S_max_size(_Alloc2&, ...)
{
// _GLIBCXX_RESOLVE_LIB_DEFECTS
}
template<typename _Alloc2>
- static auto
+ static constexpr auto
_S_select(_Alloc2& __a, int)
-> decltype(__a.select_on_container_copy_construction())
{ return __a.select_on_container_copy_construction(); }
template<typename _Alloc2>
- static _Alloc2
+ static constexpr _Alloc2
_S_select(_Alloc2& __a, ...)
{ return __a; }
*
* Calls @c a.allocate(n)
*/
- static pointer
+ _GLIBCXX_NODISCARD static _GLIBCXX20_CONSTEXPR pointer
allocate(_Alloc& __a, size_type __n)
{ return __a.allocate(__n); }
* Returns <tt> a.allocate(n, hint) </tt> if that expression is
* well-formed, otherwise returns @c a.allocate(n)
*/
- static pointer
+ _GLIBCXX_NODISCARD static _GLIBCXX20_CONSTEXPR pointer
allocate(_Alloc& __a, size_type __n, const_void_pointer __hint)
{ return _S_allocate(__a, __n, __hint, 0); }
*
* Calls <tt> a.deallocate(p, n) </tt>
*/
- static void
+ static _GLIBCXX20_CONSTEXPR void
deallocate(_Alloc& __a, pointer __p, size_type __n)
{ __a.deallocate(__p, __n); }
/**
- * @brief Construct an object of type @a _Tp
+ * @brief Construct an object of type `_Tp`
* @param __a An allocator.
* @param __p Pointer to memory of suitable size and alignment for Tp
* @param __args Constructor arguments.
* arguments @a __args...
*/
template<typename _Tp, typename... _Args>
- static auto construct(_Alloc& __a, _Tp* __p, _Args&&... __args)
+ static _GLIBCXX20_CONSTEXPR auto
+ construct(_Alloc& __a, _Tp* __p, _Args&&... __args)
+ noexcept(noexcept(_S_construct(__a, __p,
+ std::forward<_Args>(__args)...)))
-> decltype(_S_construct(__a, __p, std::forward<_Args>(__args)...))
{ _S_construct(__a, __p, std::forward<_Args>(__args)...); }
* otherwise calls @c __p->~_Tp()
*/
template<typename _Tp>
- static void destroy(_Alloc& __a, _Tp* __p)
+ static _GLIBCXX20_CONSTEXPR void
+ destroy(_Alloc& __a, _Tp* __p)
+ noexcept(noexcept(_S_destroy(__a, __p, 0)))
{ _S_destroy(__a, __p, 0); }
/**
* Returns @c __a.max_size() if that expression is well-formed,
* otherwise returns @c numeric_limits<size_type>::max()
*/
- static size_type max_size(const _Alloc& __a) noexcept
+ static _GLIBCXX20_CONSTEXPR size_type
+ max_size(const _Alloc& __a) noexcept
{ return _S_max_size(__a, 0); }
/**
* Returns @c __rhs.select_on_container_copy_construction() if that
* expression is well-formed, otherwise returns @a __rhs
*/
- static _Alloc
+ static _GLIBCXX20_CONSTEXPR _Alloc
select_on_container_copy_construction(const _Alloc& __rhs)
{ return _S_select(__rhs, 0); }
};
+#if _GLIBCXX_HOSTED
/// Partial specialization for std::allocator.
template<typename _Tp>
struct allocator_traits<allocator<_Tp>>
{
/// The allocator type
using allocator_type = allocator<_Tp>;
+
/// The allocated type
using value_type = _Tp;
*
* Calls @c a.allocate(n)
*/
- static pointer
+ [[__nodiscard__,__gnu__::__always_inline__]]
+ static _GLIBCXX20_CONSTEXPR pointer
allocate(allocator_type& __a, size_type __n)
{ return __a.allocate(__n); }
*
* Returns <tt> a.allocate(n, hint) </tt>
*/
- static pointer
- allocate(allocator_type& __a, size_type __n, const_void_pointer __hint)
- { return __a.allocate(__n, __hint); }
+ [[__nodiscard__,__gnu__::__always_inline__]]
+ static _GLIBCXX20_CONSTEXPR pointer
+ allocate(allocator_type& __a, size_type __n,
+ [[maybe_unused]] const_void_pointer __hint)
+ {
+#if __cplusplus <= 201703L
+ return __a.allocate(__n, __hint);
+#else
+ return __a.allocate(__n);
+#endif
+ }
/**
* @brief Deallocate memory.
*
* Calls <tt> a.deallocate(p, n) </tt>
*/
- static void
+ [[__gnu__::__always_inline__]]
+ static _GLIBCXX20_CONSTEXPR void
deallocate(allocator_type& __a, pointer __p, size_type __n)
{ __a.deallocate(__p, __n); }
/**
- * @brief Construct an object of type @a _Up
+ * @brief Construct an object of type `_Up`
* @param __a An allocator.
- * @param __p Pointer to memory of suitable size and alignment for Tp
+ * @param __p Pointer to memory of suitable size and alignment for
+ * an object of type `_Up`.
* @param __args Constructor arguments.
*
- * Calls <tt> __a.construct(__p, std::forward<Args>(__args)...) </tt>
+ * Calls `__a.construct(__p, std::forward<_Args>(__args)...)`
+ * in C++11, C++14 and C++17. Changed in C++20 to call
+ * `std::construct_at(__p, std::forward<_Args>(__args)...)` instead.
*/
template<typename _Up, typename... _Args>
- static void
- construct(allocator_type& __a, _Up* __p, _Args&&... __args)
- { __a.construct(__p, std::forward<_Args>(__args)...); }
+ [[__gnu__::__always_inline__]]
+ static _GLIBCXX20_CONSTEXPR void
+ construct(allocator_type& __a __attribute__((__unused__)), _Up* __p,
+ _Args&&... __args)
+ noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
+ {
+#if __cplusplus <= 201703L
+ __a.construct(__p, std::forward<_Args>(__args)...);
+#else
+ std::construct_at(__p, std::forward<_Args>(__args)...);
+#endif
+ }
/**
* @brief Destroy an object of type @a _Up
* Calls @c __a.destroy(__p).
*/
template<typename _Up>
- static void
- destroy(allocator_type& __a, _Up* __p)
- { __a.destroy(__p); }
+ [[__gnu__::__always_inline__]]
+ static _GLIBCXX20_CONSTEXPR void
+ destroy(allocator_type& __a __attribute__((__unused__)), _Up* __p)
+ noexcept(is_nothrow_destructible<_Up>::value)
+ {
+#if __cplusplus <= 201703L
+ __a.destroy(__p);
+#else
+ std::destroy_at(__p);
+#endif
+ }
/**
* @brief The maximum supported allocation size
* @param __a An allocator.
* @return @c __a.max_size()
*/
- static size_type
- max_size(const allocator_type& __a) noexcept
- { return __a.max_size(); }
+ [[__gnu__::__always_inline__]]
+ static _GLIBCXX20_CONSTEXPR size_type
+ max_size(const allocator_type& __a __attribute__((__unused__))) noexcept
+ {
+#if __cplusplus <= 201703L
+ return __a.max_size();
+#else
+ return size_t(-1) / sizeof(value_type);
+#endif
+ }
/**
* @brief Obtain an allocator to use when copying a container.
* @param __rhs An allocator.
* @return @c __rhs
*/
- static allocator_type
+ [[__gnu__::__always_inline__]]
+ static _GLIBCXX20_CONSTEXPR allocator_type
select_on_container_copy_construction(const allocator_type& __rhs)
{ return __rhs; }
};
+ /// Explicit specialization for std::allocator<void>.
+ template<>
+ struct allocator_traits<allocator<void>>
+ {
+ /// The allocator type
+ using allocator_type = allocator<void>;
+
+ /// The allocated type
+ using value_type = void;
+
+ /// The allocator's pointer type.
+ using pointer = void*;
+
+ /// The allocator's const pointer type.
+ using const_pointer = const void*;
+
+ /// The allocator's void pointer type.
+ using void_pointer = void*;
+
+ /// The allocator's const void pointer type.
+ using const_void_pointer = const void*;
+ /// The allocator's difference type
+ using difference_type = std::ptrdiff_t;
+
+ /// The allocator's size type
+ using size_type = std::size_t;
+
+ /// How the allocator is propagated on copy assignment
+ using propagate_on_container_copy_assignment = false_type;
+
+ /// How the allocator is propagated on move assignment
+ using propagate_on_container_move_assignment = true_type;
+
+ /// How the allocator is propagated on swap
+ using propagate_on_container_swap = false_type;
+
+ /// Whether all instances of the allocator type compare equal.
+ using is_always_equal = true_type;
+
+ template<typename _Up>
+ using rebind_alloc = allocator<_Up>;
+
+ template<typename _Up>
+ using rebind_traits = allocator_traits<allocator<_Up>>;
+
+ /// allocate is ill-formed for allocator<void>
+ static void*
+ allocate(allocator_type&, size_type, const void* = nullptr) = delete;
+
+ /// deallocate is ill-formed for allocator<void>
+ static void
+ deallocate(allocator_type&, void*, size_type) = delete;
+
+ /**
+ * @brief Construct an object of type `_Up`
+ * @param __a An allocator.
+ * @param __p Pointer to memory of suitable size and alignment for
+ * an object of type `_Up`.
+ * @param __args Constructor arguments.
+ *
+ * Calls `__a.construct(__p, std::forward<_Args>(__args)...)`
+ * in C++11, C++14 and C++17. Changed in C++20 to call
+ * `std::construct_at(__p, std::forward<_Args>(__args)...)` instead.
+ */
+ template<typename _Up, typename... _Args>
+ [[__gnu__::__always_inline__]]
+ static _GLIBCXX20_CONSTEXPR void
+ construct(allocator_type&, _Up* __p, _Args&&... __args)
+ noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
+ { std::_Construct(__p, std::forward<_Args>(__args)...); }
+
+ /**
+ * @brief Destroy an object of type `_Up`
+ * @param __a An allocator.
+ * @param __p Pointer to the object to destroy
+ *
+ * Invokes the destructor for `*__p`.
+ */
+ template<typename _Up>
+ [[__gnu__::__always_inline__]]
+ static _GLIBCXX20_CONSTEXPR void
+ destroy(allocator_type&, _Up* __p)
+ noexcept(is_nothrow_destructible<_Up>::value)
+ { std::_Destroy(__p); }
+
+ /// max_size is ill-formed for allocator<void>
+ static size_type
+ max_size(const allocator_type&) = delete;
+
+ /**
+ * @brief Obtain an allocator to use when copying a container.
+ * @param __rhs An allocator.
+ * @return `__rhs`
+ */
+ [[__gnu__::__always_inline__]]
+ static _GLIBCXX20_CONSTEXPR allocator_type
+ select_on_container_copy_construction(const allocator_type& __rhs)
+ { return __rhs; }
+ };
+#endif
+
+ /// @cond undocumented
+#if __cplusplus < 201703L
template<typename _Alloc>
+ [[__gnu__::__always_inline__]]
inline void
__do_alloc_on_copy(_Alloc& __one, const _Alloc& __two, true_type)
{ __one = __two; }
template<typename _Alloc>
+ [[__gnu__::__always_inline__]]
inline void
__do_alloc_on_copy(_Alloc&, const _Alloc&, false_type)
{ }
+#endif
template<typename _Alloc>
- inline void __alloc_on_copy(_Alloc& __one, const _Alloc& __two)
+ [[__gnu__::__always_inline__]]
+ _GLIBCXX14_CONSTEXPR inline void
+ __alloc_on_copy(_Alloc& __one, const _Alloc& __two)
{
- typedef allocator_traits<_Alloc> __traits;
- typedef typename __traits::propagate_on_container_copy_assignment __pocca;
+ using __traits = allocator_traits<_Alloc>;
+ using __pocca =
+ typename __traits::propagate_on_container_copy_assignment::type;
+#if __cplusplus >= 201703L
+ if constexpr (__pocca::value)
+ __one = __two;
+#else
__do_alloc_on_copy(__one, __two, __pocca());
+#endif
}
template<typename _Alloc>
- inline _Alloc __alloc_on_copy(const _Alloc& __a)
+ [[__gnu__::__always_inline__]]
+ constexpr _Alloc
+ __alloc_on_copy(const _Alloc& __a)
{
typedef allocator_traits<_Alloc> __traits;
return __traits::select_on_container_copy_construction(__a);
}
+#if __cplusplus < 201703L
template<typename _Alloc>
+ [[__gnu__::__always_inline__]]
inline void __do_alloc_on_move(_Alloc& __one, _Alloc& __two, true_type)
{ __one = std::move(__two); }
template<typename _Alloc>
+ [[__gnu__::__always_inline__]]
inline void __do_alloc_on_move(_Alloc&, _Alloc&, false_type)
{ }
+#endif
template<typename _Alloc>
- inline void __alloc_on_move(_Alloc& __one, _Alloc& __two)
+ [[__gnu__::__always_inline__]]
+ _GLIBCXX14_CONSTEXPR inline void
+ __alloc_on_move(_Alloc& __one, _Alloc& __two)
{
- typedef allocator_traits<_Alloc> __traits;
- typedef typename __traits::propagate_on_container_move_assignment __pocma;
+ using __traits = allocator_traits<_Alloc>;
+ using __pocma
+ = typename __traits::propagate_on_container_move_assignment::type;
+#if __cplusplus >= 201703L
+ if constexpr (__pocma::value)
+ __one = std::move(__two);
+#else
__do_alloc_on_move(__one, __two, __pocma());
+#endif
}
+#if __cplusplus < 201703L
template<typename _Alloc>
+ [[__gnu__::__always_inline__]]
inline void __do_alloc_on_swap(_Alloc& __one, _Alloc& __two, true_type)
{
using std::swap;
}
template<typename _Alloc>
+ [[__gnu__::__always_inline__]]
inline void __do_alloc_on_swap(_Alloc&, _Alloc&, false_type)
{ }
+#endif
template<typename _Alloc>
- inline void __alloc_on_swap(_Alloc& __one, _Alloc& __two)
+ [[__gnu__::__always_inline__]]
+ _GLIBCXX14_CONSTEXPR inline void
+ __alloc_on_swap(_Alloc& __one, _Alloc& __two)
{
- typedef allocator_traits<_Alloc> __traits;
- typedef typename __traits::propagate_on_container_swap __pocs;
+ using __traits = allocator_traits<_Alloc>;
+ using __pocs = typename __traits::propagate_on_container_swap::type;
+#if __cplusplus >= 201703L
+ if constexpr (__pocs::value)
+ {
+ using std::swap;
+ swap(__one, __two);
+ }
+#else
__do_alloc_on_swap(__one, __two, __pocs());
+#endif
}
- template<typename _Alloc>
- class __is_copy_insertable_impl
- {
- typedef allocator_traits<_Alloc> _Traits;
-
- template<typename _Up, typename
- = decltype(_Traits::construct(std::declval<_Alloc&>(),
- std::declval<_Up*>(),
- std::declval<const _Up&>()))>
- static true_type
- _M_select(int);
-
- template<typename _Up>
- static false_type
- _M_select(...);
+ template<typename _Alloc, typename _Tp,
+ typename _ValueT = __remove_cvref_t<typename _Alloc::value_type>,
+ typename = void>
+ struct __is_alloc_insertable_impl
+ : false_type
+ { };
- public:
- typedef decltype(_M_select<typename _Alloc::value_type>(0)) type;
- };
+ template<typename _Alloc, typename _Tp, typename _ValueT>
+ struct __is_alloc_insertable_impl<_Alloc, _Tp, _ValueT,
+ __void_t<decltype(allocator_traits<_Alloc>::construct(
+ std::declval<_Alloc&>(), std::declval<_ValueT*>(),
+ std::declval<_Tp>()))>>
+ : true_type
+ { };
// true if _Alloc::value_type is CopyInsertable into containers using _Alloc
+ // (might be wrong if _Alloc::construct exists but is not constrained,
+ // i.e. actually trying to use it would still be invalid. Use with caution.)
template<typename _Alloc>
struct __is_copy_insertable
- : __is_copy_insertable_impl<_Alloc>::type
+ : __is_alloc_insertable_impl<_Alloc,
+ typename _Alloc::value_type const&>::type
{ };
+#if _GLIBCXX_HOSTED
// std::allocator<_Tp> just requires CopyConstructible
template<typename _Tp>
struct __is_copy_insertable<allocator<_Tp>>
: is_copy_constructible<_Tp>
{ };
+#endif
-_GLIBCXX_END_NAMESPACE_VERSION
-} // namespace std
+ // true if _Alloc::value_type is MoveInsertable into containers using _Alloc
+ // (might be wrong if _Alloc::construct exists but is not constrained,
+ // i.e. actually trying to use it would still be invalid. Use with caution.)
+ template<typename _Alloc>
+ struct __is_move_insertable
+ : __is_alloc_insertable_impl<_Alloc, typename _Alloc::value_type>::type
+ { };
+
+#if _GLIBCXX_HOSTED
+ // std::allocator<_Tp> just requires MoveConstructible
+ template<typename _Tp>
+ struct __is_move_insertable<allocator<_Tp>>
+ : is_move_constructible<_Tp>
+ { };
+#endif
+
+ // Trait to detect Allocator-like types.
+ template<typename _Alloc, typename = void>
+ struct __is_allocator : false_type { };
+
+ template<typename _Alloc>
+ struct __is_allocator<_Alloc,
+ __void_t<typename _Alloc::value_type,
+ decltype(std::declval<_Alloc&>().allocate(size_t{}))>>
+ : true_type { };
+
+ template<typename _Alloc>
+ using _RequireAllocator
+ = typename enable_if<__is_allocator<_Alloc>::value, _Alloc>::type;
+
+ template<typename _Alloc>
+ using _RequireNotAllocator
+ = typename enable_if<!__is_allocator<_Alloc>::value, _Alloc>::type;
+#if __cpp_concepts >= 201907L
+ template<typename _Alloc>
+ concept __allocator_like = requires (_Alloc& __a) {
+ typename _Alloc::value_type;
+ __a.deallocate(__a.allocate(1u), 1u);
+ };
#endif
+ /// @endcond
+#endif // C++11
+
+ /// @cond undocumented
+
+ // To implement Option 3 of DR 431.
+ template<typename _Alloc, bool = __is_empty(_Alloc)>
+ struct __alloc_swap
+ { static void _S_do_it(_Alloc&, _Alloc&) _GLIBCXX_NOEXCEPT { } };
+
+ template<typename _Alloc>
+ struct __alloc_swap<_Alloc, false>
+ {
+ static void
+ _S_do_it(_Alloc& __one, _Alloc& __two) _GLIBCXX_NOEXCEPT
+ {
+ // Precondition: swappable allocators.
+ if (__one != __two)
+ swap(__one, __two);
+ }
+ };
+
+#if __cplusplus >= 201103L
+ template<typename _Tp, bool
+ = __or_<is_copy_constructible<typename _Tp::value_type>,
+ is_nothrow_move_constructible<typename _Tp::value_type>>::value>
+ struct __shrink_to_fit_aux
+ { static bool _S_do_it(_Tp&) noexcept { return false; } };
+
+ template<typename _Tp>
+ struct __shrink_to_fit_aux<_Tp, true>
+ {
+ _GLIBCXX20_CONSTEXPR
+ static bool
+ _S_do_it(_Tp& __c) noexcept
+ {
+#if __cpp_exceptions
+ try
+ {
+ _Tp(__make_move_if_noexcept_iterator(__c.begin()),
+ __make_move_if_noexcept_iterator(__c.end()),
+ __c.get_allocator()).swap(__c);
+ return true;
+ }
+ catch(...)
+ { return false; }
+#else
+ return false;
+#endif
+ }
+ };
+#endif
+
+ /**
+ * Destroy a range of objects using the supplied allocator. For
+ * non-default allocators we do not optimize away invocation of
+ * destroy() even if _Tp has a trivial destructor.
+ */
+
+ template<typename _ForwardIterator, typename _Allocator>
+ _GLIBCXX20_CONSTEXPR
+ void
+ _Destroy(_ForwardIterator __first, _ForwardIterator __last,
+ _Allocator& __alloc)
+ {
+ for (; __first != __last; ++__first)
+#if __cplusplus < 201103L
+ __alloc.destroy(std::__addressof(*__first));
+#else
+ allocator_traits<_Allocator>::destroy(__alloc,
+ std::__addressof(*__first));
#endif
+ }
+
+#if _GLIBCXX_HOSTED
+ template<typename _ForwardIterator, typename _Tp>
+ __attribute__((__always_inline__)) _GLIBCXX20_CONSTEXPR
+ inline void
+ _Destroy(_ForwardIterator __first, _ForwardIterator __last,
+ allocator<_Tp>&)
+ {
+ std::_Destroy(__first, __last);
+ }
+#endif
+ /// @endcond
+
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+#endif // _ALLOC_TRAITS_H