[C++0x] std::exception_ptr rvalues

[Jonathan Wakely <jwakely dot gcc at gmail dot com>]

n2884 removed support for swapping with rvalues everywhere in the
library, but I missed exception_ptr::swap() when I changed libstdc++.
The symbol is not exported so it can just be removed.

exception_ptr's move assignment operator doesn't actually move right
now:  a temporary is copy-constructed then swapped with *this.  This
patch casts the source to an rvalue-reference, ensuring the temporary
is move-constructed instead, avoiding a reference count update.

        * libsupc++/exception_ptr.h (exception_ptr::swap(exception_ptr&&)):
        Remove.
        (exception_ptr::operator=(exception_ptr&&)): Cast source to
        rvalue-reference so that move constructor is called.
        * testsuite/18_support/exception_ptr/move.cc: New.

As noted in the new file, the test checks for behaviour that is not
required, but is a property of this implementation that I think should
be tested.

Tested x86_64-unknown-linux-gnu, OK for trunk?  Should this go on the
4.4. branch too?

Jonathan

Index: libsupc++/exception_ptr.h
===================================================================
--- libsupc++/exception_ptr.h	(revision 148467)
+++ libsupc++/exception_ptr.h	(working copy)
@@ -123,7 +123,7 @@ namespace std 
       exception_ptr& 
       operator=(exception_ptr&& __o) throw()
       {
-        exception_ptr(__o).swap(*this);
+        exception_ptr(static_cast<exception_ptr&&>(__o)).swap(*this);
         return *this;
       }
 #endif
@@ -133,16 +133,6 @@ namespace std 
       void 
       swap(exception_ptr&) throw();
 
-#ifdef __GXX_EXPERIMENTAL_CXX0X__
-      void 
-      swap(exception_ptr &&__o) throw()
-      {
-        void *__tmp = _M_exception_object;
-        _M_exception_object = __o._M_exception_object;
-        __o._M_exception_object = __tmp;
-      }
-#endif
-
 #ifdef _GLIBCXX_EH_PTR_COMPAT
       // Retained for compatibility with CXXABI_1.3.
       bool operator!() const throw() __attribute__ ((__pure__));
Index: testsuite/18_support/exception_ptr/move.cc
===================================================================
--- testsuite/18_support/exception_ptr/move.cc	(revision 0)
+++ testsuite/18_support/exception_ptr/move.cc	(revision 0)
@@ -0,0 +1,45 @@
+// { dg-options "-std=gnu++0x" }
+// { dg-require-atomic-builtins "" }
+
+// Copyright (C) 2009 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 <exception>
+#include <utility>
+#include <testsuite_hooks.h>
+
+// Verify move construction and assignment are efficient and do not copy.
+// This behaviour is a GNU extension provided for efficiency.
+void test01()
+{
+  bool test = true;
+ 
+  std::exception_ptr p1 = std::copy_exception(test);
+  std::exception_ptr p2 = std::move(p1);
+  VERIFY( p1 == 0 );
+  VERIFY( !(p2 == 0) );
+
+  p1 = std::move(p2);
+  VERIFY( !(p1 == 0) );
+  VERIFY( p2 == 0 );
+}
+
+int main()
+{
+  test01();
+  return 0;
+}