Revert "Remove shared_ptr because AVR does not support atomics"

This reverts commit eacaac1.

include/backward/auto_ptr.h

@@ -0,0 +1,337 @@
+// auto_ptr implementation -*- C++ -*-
+
+// Copyright (C) 2007-2020 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 backward/auto_ptr.h
+ *  This is an internal header file, included by other library headers.
+ *  Do not attempt to use it directly. @headername{memory}
+ */
+
+#ifndef _BACKWARD_AUTO_PTR_H
+#define _BACKWARD_AUTO_PTR_H 1
+
+#include <bits/c++config.h>
+#include <debug/debug.h>
+
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+  /**
+   *  A wrapper class to provide auto_ptr with reference semantics.
+   *  For example, an auto_ptr can be assigned (or constructed from)
+   *  the result of a function which returns an auto_ptr by value.
+   *
+   *  All the auto_ptr_ref stuff should happen behind the scenes.
+   */
+  template<typename _Tp1>
+    struct auto_ptr_ref
+    {
+      _Tp1* _M_ptr;
+
+      explicit
+      auto_ptr_ref(_Tp1* __p): _M_ptr(__p) { }
+    } _GLIBCXX_DEPRECATED;
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+
+  /**
+   *  @brief  A simple smart pointer providing strict ownership semantics.
+   *
+   *  The Standard says:
+   *  <pre>
+   *  An @c auto_ptr owns the object it holds a pointer to.  Copying
+   *  an @c auto_ptr copies the pointer and transfers ownership to the
+   *  destination.  If more than one @c auto_ptr owns the same object
+   *  at the same time the behavior of the program is undefined.
+   *
+   *  The uses of @c auto_ptr include providing temporary
+   *  exception-safety for dynamically allocated memory, passing
+   *  ownership of dynamically allocated memory to a function, and
+   *  returning dynamically allocated memory from a function.  @c
+   *  auto_ptr does not meet the CopyConstructible and Assignable
+   *  requirements for Standard Library <a
+   *  href="tables.html#65">container</a> elements and thus
+   *  instantiating a Standard Library container with an @c auto_ptr
+   *  results in undefined behavior.
+   *  </pre>
+   *  Quoted from [20.4.5]/3.
+   *
+   *  Good examples of what can and cannot be done with auto_ptr can
+   *  be found in the libstdc++ testsuite.
+   *
+   *  _GLIBCXX_RESOLVE_LIB_DEFECTS
+   *  127.  auto_ptr<> conversion issues
+   *  These resolutions have all been incorporated.
+   */
+  template<typename _Tp>
+    class auto_ptr
+    {
+    private:
+      _Tp* _M_ptr;
+
+    public:
+      /// The pointed-to type.
+      typedef _Tp element_type;
+
+      /**
+       *  @brief  An %auto_ptr is usually constructed from a raw pointer.
+       *  @param  __p  A pointer (defaults to NULL).
+       *
+       *  This object now @e owns the object pointed to by @a __p.
+       */
+      explicit
+      auto_ptr(element_type* __p = 0) throw() : _M_ptr(__p) { }
+
+      /**
+       *  @brief  An %auto_ptr can be constructed from another %auto_ptr.
+       *  @param  __a  Another %auto_ptr of the same type.
+       *
+       *  This object now @e owns the object previously owned by @a __a,
+       *  which has given up ownership.
+       */
+      auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) { }
+
+      /**
+       *  @brief  An %auto_ptr can be constructed from another %auto_ptr.
+       *  @param  __a  Another %auto_ptr of a different but related type.
+       *
+       *  A pointer-to-Tp1 must be convertible to a
+       *  pointer-to-Tp/element_type.
+       *
+       *  This object now @e owns the object previously owned by @a __a,
+       *  which has given up ownership.
+       */
+      template<typename _Tp1>
+        auto_ptr(auto_ptr<_Tp1>& __a) throw() : _M_ptr(__a.release()) { }
+
+      /**
+       *  @brief  %auto_ptr assignment operator.
+       *  @param  __a  Another %auto_ptr of the same type.
+       *
+       *  This object now @e owns the object previously owned by @a __a,
+       *  which has given up ownership.  The object that this one @e
+       *  used to own and track has been deleted.
+       */
+      auto_ptr&
+      operator=(auto_ptr& __a) throw()
+      {
+	reset(__a.release());
+	return *this;
+      }
+
+      /**
+       *  @brief  %auto_ptr assignment operator.
+       *  @param  __a  Another %auto_ptr of a different but related type.
+       *
+       *  A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type.
+       *
+       *  This object now @e owns the object previously owned by @a __a,
+       *  which has given up ownership.  The object that this one @e
+       *  used to own and track has been deleted.
+       */
+      template<typename _Tp1>
+        auto_ptr&
+        operator=(auto_ptr<_Tp1>& __a) throw()
+        {
+	  reset(__a.release());
+	  return *this;
+	}
+
+      /**
+       *  When the %auto_ptr goes out of scope, the object it owns is
+       *  deleted.  If it no longer owns anything (i.e., @c get() is
+       *  @c NULL), then this has no effect.
+       *
+       *  The C++ standard says there is supposed to be an empty throw
+       *  specification here, but omitting it is standard conforming.  Its
+       *  presence can be detected only if _Tp::~_Tp() throws, but this is
+       *  prohibited.  [17.4.3.6]/2
+       */
+      ~auto_ptr() { delete _M_ptr; }
+
+      /**
+       *  @brief  Smart pointer dereferencing.
+       *
+       *  If this %auto_ptr no longer owns anything, then this
+       *  operation will crash.  (For a smart pointer, <em>no longer owns
+       *  anything</em> is the same as being a null pointer, and you know
+       *  what happens when you dereference one of those...)
+       */
+      element_type&
+      operator*() const throw() 
+      {
+	__glibcxx_assert(_M_ptr != 0);
+	return *_M_ptr; 
+      }
+
+      /**
+       *  @brief  Smart pointer dereferencing.
+       *
+       *  This returns the pointer itself, which the language then will
+       *  automatically cause to be dereferenced.
+       */
+      element_type*
+      operator->() const throw() 
+      {
+	__glibcxx_assert(_M_ptr != 0);
+	return _M_ptr; 
+      }
+
+      /**
+       *  @brief  Bypassing the smart pointer.
+       *  @return  The raw pointer being managed.
+       *
+       *  You can get a copy of the pointer that this object owns, for
+       *  situations such as passing to a function which only accepts
+       *  a raw pointer.
+       *
+       *  @note  This %auto_ptr still owns the memory.
+       */
+      element_type*
+      get() const throw() { return _M_ptr; }
+
+      /**
+       *  @brief  Bypassing the smart pointer.
+       *  @return  The raw pointer being managed.
+       *
+       *  You can get a copy of the pointer that this object owns, for
+       *  situations such as passing to a function which only accepts
+       *  a raw pointer.
+       *
+       *  @note  This %auto_ptr no longer owns the memory.  When this object
+       *  goes out of scope, nothing will happen.
+       */
+      element_type*
+      release() throw()
+      {
+	element_type* __tmp = _M_ptr;
+	_M_ptr = 0;
+	return __tmp;
+      }
+
+      /**
+       *  @brief  Forcibly deletes the managed object.
+       *  @param  __p  A pointer (defaults to NULL).
+       *
+       *  This object now @e owns the object pointed to by @a __p.  The
+       *  previous object has been deleted.
+       */
+      void
+      reset(element_type* __p = 0) throw()
+      {
+	if (__p != _M_ptr)
+	  {
+	    delete _M_ptr;
+	    _M_ptr = __p;
+	  }
+      }
+
+      /** 
+       *  @brief  Automatic conversions
+       *
+       *  These operations are supposed to convert an %auto_ptr into and from
+       *  an auto_ptr_ref automatically as needed.  This would allow
+       *  constructs such as
+       *  @code
+       *    auto_ptr<Derived>  func_returning_auto_ptr(.....);
+       *    ...
+       *    auto_ptr<Base> ptr = func_returning_auto_ptr(.....);
+       *  @endcode
+       *
+       *  But it doesn't work, and won't be fixed. For further details see
+       *  http://cplusplus.github.io/LWG/lwg-closed.html#463
+       */
+      auto_ptr(auto_ptr_ref<element_type> __ref) throw()
+      : _M_ptr(__ref._M_ptr) { }
+
+      auto_ptr&
+      operator=(auto_ptr_ref<element_type> __ref) throw()
+      {
+	if (__ref._M_ptr != this->get())
+	  {
+	    delete _M_ptr;
+	    _M_ptr = __ref._M_ptr;
+	  }
+	return *this;
+      }
+
+      template<typename _Tp1>
+        operator auto_ptr_ref<_Tp1>() throw()
+        { return auto_ptr_ref<_Tp1>(this->release()); }
+
+      template<typename _Tp1>
+        operator auto_ptr<_Tp1>() throw()
+        { return auto_ptr<_Tp1>(this->release()); }
+    } _GLIBCXX_DEPRECATED;
+
+  // _GLIBCXX_RESOLVE_LIB_DEFECTS
+  // 541. shared_ptr template assignment and void
+  template<>
+    class auto_ptr<void>
+    {
+    public:
+      typedef void element_type;
+    } _GLIBCXX_DEPRECATED;
+
+#if __cplusplus >= 201103L
+  template<_Lock_policy _Lp>
+  template<typename _Tp>
+    inline
+    __shared_count<_Lp>::__shared_count(std::auto_ptr<_Tp>&& __r)
+    : _M_pi(new _Sp_counted_ptr<_Tp*, _Lp>(__r.get()))
+    { __r.release(); }
+
+  template<typename _Tp, _Lock_policy _Lp>
+  template<typename _Tp1, typename>
+    inline
+    __shared_ptr<_Tp, _Lp>::__shared_ptr(std::auto_ptr<_Tp1>&& __r)
+    : _M_ptr(__r.get()), _M_refcount()
+    {
+      __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
+      static_assert( sizeof(_Tp1) > 0, "incomplete type" );
+      _Tp1* __tmp = __r.get();
+      _M_refcount = __shared_count<_Lp>(std::move(__r));
+      _M_enable_shared_from_this_with(__tmp);
+    }
+
+  template<typename _Tp>
+  template<typename _Tp1, typename>
+    inline
+    shared_ptr<_Tp>::shared_ptr(std::auto_ptr<_Tp1>&& __r)
+    : __shared_ptr<_Tp>(std::move(__r)) { }
+
+  template<typename _Tp, typename _Dp>
+  template<typename _Up, typename>
+    inline
+    unique_ptr<_Tp, _Dp>::unique_ptr(auto_ptr<_Up>&& __u) noexcept
+    : _M_t(__u.release(), deleter_type()) { }
+#endif
+
+#pragma GCC diagnostic pop
+
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace
+
+#endif /* _BACKWARD_AUTO_PTR_H */