Only set std::enable_shared_from_this member once.

	* include/bits/shared_ptr.h (__enable_shared_from_this_helper): Use
	nullptr.
	* include/bits/shared_ptr_base.h (weak_ptr::_M_assign): Don't assign
	if ownership is already shared with a shared_ptr object.
	(__enable_shared_from_this_helper): Use nullptr.
	* testsuite/20_util/enable_shared_from_this/members/const.cc: New.
	* testsuite/20_util/enable_shared_from_this/members/reinit.cc: New.
	* testsuite/20_util/enable_shared_from_this/requirements/
	explicit_instantiation.cc: Instantiate with const and incomplete types.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@227232 138bc75d-0d04-0410-961f-82ee72b054a4

3 files changed, 114 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/const.cc b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/const.cc
new file mode 100644
index 00000000000..fdf39c7916e
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/const.cc
@@ -0,0 +1,60 @@
+// Copyright (C) 2015 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-options "-std=gnu++11" }
+
+#include <memory>
+#include <testsuite_hooks.h>
+
+template<typename T, typename U>
+  bool
+  share_ownership(const std::shared_ptr<T>& p1, const std::shared_ptr<U>& p2)
+  {
+    return !p1.owner_before(p2) && !p2.owner_before(p1);
+  }
+
+void
+test01()
+{
+  struct X : public std::enable_shared_from_this<X> { };
+  using CX = const X;
+  std::shared_ptr<CX> p(new X);
+  VERIFY( share_ownership(p->shared_from_this(), p) );
+  p.reset(new CX);
+  VERIFY( share_ownership(p->shared_from_this(), p) );
+  auto p2 = std::const_pointer_cast<X>(p)->shared_from_this();
+  VERIFY( share_ownership(p2, p) );
+}
+
+void
+test02()
+{
+  struct X;
+  using CX = const X;
+  struct X : public std::enable_shared_from_this<CX> { };
+  std::shared_ptr<CX> p(new X);
+  VERIFY( share_ownership(p->shared_from_this(), p) );
+  p.reset(new CX);
+  VERIFY( share_ownership(p->shared_from_this(), p) );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+}
diff --git a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/reinit.cc b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/reinit.cc
new file mode 100644
index 00000000000..3740db8ac36
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/reinit.cc
@@ -0,0 +1,49 @@
+// Copyright (C) 2015 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-options "-std=gnu++11" }
+
+#include <memory>
+#include <testsuite_hooks.h>
+
+struct X : public std::enable_shared_from_this<X> { };
+
+bool
+share_ownership(const std::shared_ptr<X>& p1, const std::shared_ptr<X>& p2)
+{
+  return !p1.owner_before(p2) && !p2.owner_before(p1);
+}
+
+void
+test01()
+{
+  std::shared_ptr<X> p1(new X);
+  VERIFY( share_ownership( p1->shared_from_this(), p1 ) );
+  {
+    std::shared_ptr<X> p2(p1.get(), [](X*){});
+    // The weak_ptr member of the enable_shared_from_this base should not
+    // be reset by creating a second control block that owns the pointer.
+    VERIFY( share_ownership( p2->shared_from_this(), p1 ) );
+  }
+  VERIFY( share_ownership( p1->shared_from_this(), p1 ) );
+}
+
+int
+main()
+{
+  test01();
+}
diff --git a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/requirements/explicit_instantiation.cc b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/requirements/explicit_instantiation.cc
index 270ee8409b9..94638e19242 100644
--- a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/requirements/explicit_instantiation.cc
+++ b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/requirements/explicit_instantiation.cc
@@ -21,3 +21,8 @@
 #include <memory>
 
 template class std::enable_shared_from_this<int>;
+template class std::enable_shared_from_this<const int>;
+
+class Incomplete;
+template class std::enable_shared_from_this<Incomplete>;
+template class std::enable_shared_from_this<const Incomplete>;