PR79156 fix std::__enable_shared_from_this extension

	PR libstdc++/79156
	* include/bits/shared_ptr_base.h (__enable_shared_from_this_base):
	Fix return type.
	(__enable_shared_from_this): Declare __shared_ptr as a friend.
	* testsuite/ext/shared_ptr/1.cc: New test.

From-SVN: r244668

libstdc++-v3/ChangeLog

 2017-01-19  Jonathan Wakely  <jwakely@redhat.com>
 
+	PR libstdc++/79156
+	* include/bits/shared_ptr_base.h (__enable_shared_from_this_base):
+	Fix return type.
+	(__enable_shared_from_this): Declare __shared_ptr as a friend.
+	* testsuite/ext/shared_ptr/1.cc: New test.
+
 	PR libstdc++/64903
 	* include/bits/stl_algo.h (is_partioned): Don't retest the partition
 	point.

libstdc++-v3/include/bits/shared_ptr_base.h

@@ -1817,11 +1817,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	_M_weak_assign(_Tp1* __p, const __shared_count<_Lp>& __n) const noexcept
 	{ _M_weak_this._M_assign(__p, __n); }
 
-      friend void
+      friend const __enable_shared_from_this*
       __enable_shared_from_this_base(const __shared_count<_Lp>&,
 				     const __enable_shared_from_this* __p)
       { return __p; }
 
+      template<typename, _Lock_policy>
+	friend class __shared_ptr;
+
       mutable __weak_ptr<_Tp, _Lp>  _M_weak_this;
     };
 

libstdc++-v3/testsuite/ext/shared_ptr/1.cc

+// Copyright (C) 2017 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/>.
+
+// { dg-do run { target c++11 } }
+
+#include <memory>
+#include <testsuite_hooks.h>
+
+struct A : std::__enable_shared_from_this<A> { };
+
+void
+test01()
+{
+  std::__shared_ptr<A> sp(new A);
+  auto sp2 = sp->shared_from_this();
+  VERIFY( (bool)sp2 );
+  static_assert( std::is_same<decltype(sp), decltype(sp2)>::value, "" );
+}
+
+int
+main()
+{
+  test01();
+}