<h2>Editing File: /usr/include/c++/8/experimental/memory_resource</h2><form method='post'><textarea name='content' class='file-edit'>// &lt;experimental/memory_resource&gt; -*- C++ -*-

// Copyright (C) 2015-2018 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
// &lt;http://www.gnu.org/licenses/&gt;.

/** @file experimental/memory_resource
 *  This is a TS C++ Library header.
 */

#ifndef _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE
#define _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE 1

#pragma GCC system_header

#if __cplusplus &gt;= 201402L

#include &lt;memory&gt;
#include &lt;new&gt;
#include &lt;atomic&gt;
#include &lt;cstddef&gt;
#include &lt;experimental/bits/lfts_config.h&gt;

namespace std {
_GLIBCXX_BEGIN_NAMESPACE_VERSION

namespace experimental {
inline namespace fundamentals_v2 {
namespace pmr {
#define __cpp_lib_experimental_memory_resources 201402L

  class memory_resource;

  template &lt;typename _Tp&gt;
    class polymorphic_allocator;

  template &lt;typename _Alloc&gt;
    class __resource_adaptor_imp;

  template &lt;typename _Alloc&gt;
    using resource_adaptor = __resource_adaptor_imp&lt;
      typename allocator_traits&lt;_Alloc&gt;::template rebind_alloc&lt;char&gt;&gt;;

  template &lt;typename _Tp&gt;
    struct __uses_allocator_construction_helper;

  // Global memory resources
  memory_resource* new_delete_resource() noexcept;
  memory_resource* null_memory_resource() noexcept;

  // The default memory resource
  memory_resource* get_default_resource() noexcept;
  memory_resource* set_default_resource(memory_resource* __r) noexcept;

  // Standard memory resources

  // 8.5 Class memory_resource
  class memory_resource
  {
  protected:
    static constexpr size_t _S_max_align = alignof(max_align_t);

  public:
    virtual ~memory_resource() { }

    void*
    allocate(size_t __bytes, size_t __alignment = _S_max_align)
    { return do_allocate(__bytes, __alignment); }

    void
    deallocate(void* __p, size_t __bytes, size_t __alignment = _S_max_align)
    { return do_deallocate(__p, __bytes, __alignment); }

    bool
    is_equal(const memory_resource&amp; __other) const noexcept
    { return do_is_equal(__other); }

  protected:
    virtual void*
    do_allocate(size_t __bytes, size_t __alignment) = 0;

    virtual void
    do_deallocate(void* __p, size_t __bytes, size_t __alignment) = 0;

    virtual bool
    do_is_equal(const memory_resource&amp; __other) const noexcept = 0;
  };

  inline bool
  operator==(const memory_resource&amp; __a,
	     const memory_resource&amp; __b) noexcept
  { return &amp;__a == &amp;__b || __a.is_equal(__b); }

  inline bool
  operator!=(const memory_resource&amp; __a,
	     const memory_resource&amp; __b) noexcept
  { return !(__a == __b); }


  // 8.6 Class template polymorphic_allocator
  template &lt;class _Tp&gt;
    class polymorphic_allocator
    {
      using __uses_alloc1_ = __uses_alloc1&lt;memory_resource*&gt;;
      using __uses_alloc2_ = __uses_alloc2&lt;memory_resource*&gt;;

      template&lt;typename _Tp1, typename... _Args&gt;
	void
	_M_construct(__uses_alloc0, _Tp1* __p, _Args&amp;&amp;... __args)
	{ ::new(__p) _Tp1(std::forward&lt;_Args&gt;(__args)...); }

      template&lt;typename _Tp1, typename... _Args&gt;
	void
	_M_construct(__uses_alloc1_, _Tp1* __p, _Args&amp;&amp;...  __args)
	{ ::new(__p) _Tp1(allocator_arg, this-&gt;resource(),
			  std::forward&lt;_Args&gt;(__args)...); }

      template&lt;typename _Tp1, typename... _Args&gt;
	void
	_M_construct(__uses_alloc2_, _Tp1* __p, _Args&amp;&amp;...  __args)
	{ ::new(__p) _Tp1(std::forward&lt;_Args&gt;(__args)...,
			  this-&gt;resource()); }

    public:
      using value_type = _Tp;

      polymorphic_allocator() noexcept
      : _M_resource(get_default_resource())
      { }

      polymorphic_allocator(memory_resource* __r)
      : _M_resource(__r)
      { _GLIBCXX_DEBUG_ASSERT(__r); }

      polymorphic_allocator(const polymorphic_allocator&amp; __other) = default;

      template &lt;typename _Up&gt;
	polymorphic_allocator(const polymorphic_allocator&lt;_Up&gt;&amp;
			      __other) noexcept
	: _M_resource(__other.resource())
	{ }

      polymorphic_allocator&amp;
	operator=(const polymorphic_allocator&amp; __rhs) = default;

      _Tp* allocate(size_t __n)
      { return static_cast&lt;_Tp*&gt;(_M_resource-&gt;allocate(__n * sizeof(_Tp),
						       alignof(_Tp))); }

      void deallocate(_Tp* __p, size_t __n)
      { _M_resource-&gt;deallocate(__p, __n * sizeof(_Tp), alignof(_Tp)); }

      template &lt;typename _Tp1, typename... _Args&gt; //used here
	void construct(_Tp1* __p, _Args&amp;&amp;... __args)
	{
	  memory_resource* const __resource = this-&gt;resource();
	  auto __use_tag
	    = __use_alloc&lt;_Tp1, memory_resource*, _Args...&gt;(__resource);
	  _M_construct(__use_tag, __p, std::forward&lt;_Args&gt;(__args)...);
	}

      // Specializations for pair using piecewise construction
      template &lt;typename _Tp1, typename _Tp2,
	       typename... _Args1, typename... _Args2&gt;
	void construct(pair&lt;_Tp1, _Tp2&gt;* __p, piecewise_construct_t,
		       tuple&lt;_Args1...&gt; __x,
		       tuple&lt;_Args2...&gt; __y)
	{
	  memory_resource* const __resource = this-&gt;resource();
	  auto __x_use_tag =
	    __use_alloc&lt;_Tp1, memory_resource*, _Args1...&gt;(__resource);
	  auto __y_use_tag =
	    __use_alloc&lt;_Tp2, memory_resource*, _Args2...&gt;(__resource);

	  ::new(__p) std::pair&lt;_Tp1, _Tp2&gt;(piecewise_construct,
					   _M_construct_p(__x_use_tag, __x),
					   _M_construct_p(__y_use_tag, __y));
	}

      template &lt;typename _Tp1, typename _Tp2&gt;
	void construct(pair&lt;_Tp1,_Tp2&gt;* __p)
	{ this-&gt;construct(__p, piecewise_construct, tuple&lt;&gt;(), tuple&lt;&gt;()); }

      template &lt;typename _Tp1, typename _Tp2, typename _Up, typename _Vp&gt;
	void construct(pair&lt;_Tp1,_Tp2&gt;* __p, _Up&amp;&amp; __x, _Vp&amp;&amp; __y)
	{ this-&gt;construct(__p, piecewise_construct,
			  forward_as_tuple(std::forward&lt;_Up&gt;(__x)),
			  forward_as_tuple(std::forward&lt;_Vp&gt;(__y))); }

      template &lt;typename _Tp1, typename _Tp2, typename _Up, typename _Vp&gt;
	void construct(pair&lt;_Tp1,_Tp2&gt;* __p, const std::pair&lt;_Up, _Vp&gt;&amp; __pr)
	{ this-&gt;construct(__p, piecewise_construct, forward_as_tuple(__pr.first),
			  forward_as_tuple(__pr.second)); }

      template &lt;typename _Tp1, typename _Tp2, typename _Up, typename _Vp&gt;
	void construct(pair&lt;_Tp1,_Tp2&gt;* __p, pair&lt;_Up, _Vp&gt;&amp;&amp; __pr)
	{ this-&gt;construct(__p, piecewise_construct,
			  forward_as_tuple(std::forward&lt;_Up&gt;(__pr.first)),
			  forward_as_tuple(std::forward&lt;_Vp&gt;(__pr.second))); }

      template &lt;typename _Up&gt;
	void destroy(_Up* __p)
	{ __p-&gt;~_Up(); }

      // Return a default-constructed allocator (no allocator propagation)
      polymorphic_allocator select_on_container_copy_construction() const
      { return polymorphic_allocator(); }

      memory_resource* resource() const
      { return _M_resource; }

    private:
      template&lt;typename _Tuple&gt;
	_Tuple&amp;&amp;
	_M_construct_p(__uses_alloc0, _Tuple&amp; __t)
	{ return std::move(__t); }

      template&lt;typename... _Args&gt;
	decltype(auto)
	_M_construct_p(__uses_alloc1_ __ua, tuple&lt;_Args...&gt;&amp; __t)
	{ return tuple_cat(make_tuple(allocator_arg, *(__ua._M_a)),
			   std::move(__t)); }

      template&lt;typename... _Args&gt;
	decltype(auto)
	_M_construct_p(__uses_alloc2_ __ua, tuple&lt;_Args...&gt;&amp; __t)
	{ return tuple_cat(std::move(__t), make_tuple(*(__ua._M_a))); }

      memory_resource* _M_resource;
    };

  template &lt;class _Tp1, class _Tp2&gt;
    bool operator==(const polymorphic_allocator&lt;_Tp1&gt;&amp; __a,
		    const polymorphic_allocator&lt;_Tp2&gt;&amp; __b) noexcept
    { return *__a.resource() == *__b.resource(); }

  template &lt;class _Tp1, class _Tp2&gt;
    bool operator!=(const polymorphic_allocator&lt;_Tp1&gt;&amp; __a,
		    const polymorphic_allocator&lt;_Tp2&gt;&amp; __b) noexcept
    { return !(__a == __b); }

  // 8.7.1 __resource_adaptor_imp
  template &lt;typename _Alloc&gt;
    class __resource_adaptor_imp : public memory_resource
    {
      static_assert(is_same&lt;char,
	  typename allocator_traits&lt;_Alloc&gt;::value_type&gt;::value,
	  &quot;Allocator's value_type is char&quot;);
      static_assert(is_same&lt;char*,
	  typename allocator_traits&lt;_Alloc&gt;::pointer&gt;::value,
	  &quot;Allocator's pointer type is value_type*&quot;);
      static_assert(is_same&lt;const char*,
	  typename allocator_traits&lt;_Alloc&gt;::const_pointer&gt;::value,
	  &quot;Allocator's const_pointer type is value_type const*&quot;);
      static_assert(is_same&lt;void*,
	  typename allocator_traits&lt;_Alloc&gt;::void_pointer&gt;::value,
	  &quot;Allocator's void_pointer type is void*&quot;);
      static_assert(is_same&lt;const void*,
	  typename allocator_traits&lt;_Alloc&gt;::const_void_pointer&gt;::value,
	  &quot;Allocator's const_void_pointer type is void const*&quot;);

    public:
      using allocator_type = _Alloc;

      __resource_adaptor_imp() = default;
      __resource_adaptor_imp(const __resource_adaptor_imp&amp;) = default;
      __resource_adaptor_imp(__resource_adaptor_imp&amp;&amp;) = default;

      explicit __resource_adaptor_imp(const _Alloc&amp; __a2)
      : _M_alloc(__a2)
      { }

      explicit __resource_adaptor_imp(_Alloc&amp;&amp; __a2)
      : _M_alloc(std::move(__a2))
      { }

      __resource_adaptor_imp&amp;
      operator=(const __resource_adaptor_imp&amp;) = default;

      allocator_type get_allocator() const noexcept { return _M_alloc; }

    protected:
      virtual void*
      do_allocate(size_t __bytes, size_t __alignment)
      {
	using _Aligned_alloc = std::__alloc_rebind&lt;_Alloc, char&gt;;
	size_t __new_size = _S_aligned_size(__bytes,
					    _S_supported(__alignment) ?
					    __alignment : _S_max_align);
	return _Aligned_alloc(_M_alloc).allocate(__new_size);
      }

      virtual void
      do_deallocate(void* __p, size_t __bytes, size_t __alignment)
      {
	using _Aligned_alloc = std::__alloc_rebind&lt;_Alloc, char&gt;;
	size_t __new_size = _S_aligned_size(__bytes,
					    _S_supported(__alignment) ?
					    __alignment : _S_max_align);
	using _Ptr = typename allocator_traits&lt;_Aligned_alloc&gt;::pointer;
	_Aligned_alloc(_M_alloc).deallocate(static_cast&lt;_Ptr&gt;(__p),
					    __new_size);
      }

      virtual bool
      do_is_equal(const memory_resource&amp; __other) const noexcept
      {
	auto __p = dynamic_cast&lt;const __resource_adaptor_imp*&gt;(&amp;__other);
	return __p ? (_M_alloc == __p-&gt;_M_alloc) : false;
      }

    private:
      // Calculate Aligned Size
      // Returns a size that is larger than or equal to __size and divisible
      // by __alignment, where __alignment is required to be a power of 2.
      static size_t
      _S_aligned_size(size_t __size, size_t __alignment)
      { return ((__size - 1)|(__alignment - 1)) + 1; }

      // Determine whether alignment meets one of those preconditions:
      // 1. Equal to Zero
      // 2. Is power of two
      static bool
      _S_supported (size_t __x)
      { return ((__x != 0) &amp;&amp; !(__x &amp; (__x - 1))); }

      _Alloc _M_alloc;
    };

  // Global memory resources

  inline memory_resource*
  new_delete_resource() noexcept
  {
    using type = resource_adaptor&lt;std::allocator&lt;char&gt;&gt;;
    alignas(type) static unsigned char __buf[sizeof(type)];
    static type* __r = new(__buf) type;
    return __r;
  }

  inline memory_resource*
  null_memory_resource() noexcept
  {
    class type final : public memory_resource
    {
      void*
      do_allocate(size_t, size_t) override
      { std::__throw_bad_alloc(); }

      void
      do_deallocate(void*, size_t, size_t) noexcept override
      { }

      bool
      do_is_equal(const memory_resource&amp; __other) const noexcept override
      { return this == &amp;__other; }
    };

    alignas(type) static unsigned char __buf[sizeof(type)];
    static type* __r = new(__buf) type;
    return __r;
  }

  // The default memory resource

  inline std::atomic&lt;memory_resource*&gt;&amp;
  __get_default_resource()
  {
    using type = atomic&lt;memory_resource*&gt;;
    alignas(type) static unsigned char __buf[sizeof(type)];
    static type* __r = new(__buf) type(new_delete_resource());
    return *__r;
  }

  inline memory_resource*
  get_default_resource() noexcept
  { return __get_default_resource().load(); }

  inline memory_resource*
  set_default_resource(memory_resource* __r) noexcept
  {
    if (__r == nullptr)
      __r = new_delete_resource();
    return __get_default_resource().exchange(__r);
  }
} // namespace pmr
} // namespace fundamentals_v2
} // namespace experimental

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // C++14
#endif // _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE
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