fix libstdc++/58839

diff --git a/libstdc++-v3/include/bits/shared_ptr_base.h b/libstdc++-v3/include/bits/shared_ptr_base.h
index 911dd92..91b6367 100644
--- a/libstdc++-v3/include/bits/shared_ptr_base.h
+++ b/libstdc++-v3/include/bits/shared_ptr_base.h
@@ -855,9 +855,9 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	: _M_ptr(__r.get()), _M_refcount()
 	{
 	  __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
-	  auto __tmp = std::__addressof(*__r.get());
+	  auto __raw = _S_raw_ptr(__r.get());
 	  _M_refcount = __shared_count<_Lp>(std::move(__r));
-	  __enable_shared_from_this_helper(_M_refcount, __tmp, __tmp);
+	  __enable_shared_from_this_helper(_M_refcount, __raw, __raw);
 	}
 
 #if _GLIBCXX_USE_DEPRECATED
@@ -1048,6 +1048,16 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
       _M_get_deleter(const std::type_info& __ti) const noexcept
       { return _M_refcount._M_get_deleter(__ti); }
 
+      template<typename _Tp1>
+	static _Tp1*
+	_S_raw_ptr(_Tp1* __ptr)
+	{ return __ptr; }
+
+      template<typename _Tp1>
+	static auto
+	_S_raw_ptr(_Tp1 __ptr) -> decltype(std::__addressof(*__ptr))
+	{ return std::__addressof(*__ptr); }
+
       template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
       template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
 
diff --git a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/assign.cc b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/assign.cc
new file mode 100644
index 0000000..24ab926
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/assign.cc
@@ -0,0 +1,36 @@ 
+// { dg-options "-std=gnu++11" }
+
+// Copyright (C) 2013 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.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <memory>
+#include <testsuite_hooks.h>
+
+struct X : public std::enable_shared_from_this<X> { };
+
+void test01()
+{
+  bool test __attribute__((unused)) = true;
+  auto x1 = std::make_shared<X>(), x2 = std::make_shared<X>();
+  *x1 = *x2;
+  VERIFY( x1->shared_from_this() != x2->shared_from_this() );
+}
+
+int main()
+{
+  test01();
+}
diff --git a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/unique_ptr.cc b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/unique_ptr.cc
new file mode 100644
index 0000000..9f0eaa7
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/unique_ptr.cc
@@ -0,0 +1,62 @@ 
+// { dg-options "-std=gnu++11" }
+
+// Copyright (C) 2013 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.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <memory>
+#include <ext/pointer.h>
+#include <testsuite_hooks.h>
+
+struct X : public std::enable_shared_from_this<X> { };
+
+void test01()
+{
+  std::unique_ptr<X> up(new X);
+  X* xp = up.get();
+  std::shared_ptr<X> sp(std::move(up));
+  VERIFY( xp->shared_from_this() != nullptr );
+}
+
+using __gnu_cxx::_Pointer_adapter;
+using __gnu_cxx::_Std_pointer_impl;
+
+struct Deleter
+{
+  struct pointer : _Pointer_adapter<_Std_pointer_impl<X>>
+  {
+    using _Pointer_adapter::_Pointer_adapter;
+    operator X*() const noexcept { return this->get(); }
+  };
+
+  void operator()(pointer p) const noexcept { delete (X*)p; }
+};
+
+void test02()
+{
+  std::unique_ptr<X, Deleter> up(new X);
+  Deleter::pointer xp = up.get();
+  // Creating shared_ptr from unique_ptr with custom pointer is an extension:
+  std::shared_ptr<X> sp(std::move(up));
+  // but enable_shared_from_this should still work:
+  VERIFY( xp->shared_from_this() != nullptr );
+}
+
+int main()
+{
+  test01();
+  test02();
+}
diff --git a/libstdc++-v3/testsuite/20_util/shared_ptr/cons/58839.cc b/libstdc++-v3/testsuite/20_util/shared_ptr/cons/58839.cc
new file mode 100644
index 0000000..6ad2564
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/shared_ptr/cons/58839.cc
@@ -0,0 +1,29 @@ 
+// { dg-options "-std=gnu++11" }
+// { dg-do compile }
+
+// Copyright (C) 2013 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.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <memory>
+
+// libstdc++/58839
+
+void test01()
+{
+  std::unique_ptr<void> y;
+  std::shared_ptr<void> x = std::move(y);
+}