move.h (forward): Implement N3143, resolving US 90.

2010-11-11  Paolo Carlini  <paolo.carlini@oracle.com>

	* include/bits/move.h (forward): Implement N3143, resolving US 90.
	* testsuite/20_util/forward/a.cc: New.
	* testsuite/20_util/forward/b.cc: Likewise.
	* testsuite/20_util/forward/c_neg.cc: Likewise.
	* testsuite/20_util/forward/d.cc: Likewise.
	* testsuite/20_util/forward/e.cc: Likewise.
	* testsuite/20_util/forward/f_neg.cc: Likewise.

From-SVN: r166599

8 files changed, 474 insertions, 19 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index ab6a3fc..a82999b 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,13 @@
+2010-11-11  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	* include/bits/move.h (forward): Implement N3143, resolving US 90.
+	* testsuite/20_util/forward/a.cc: New.
+	* testsuite/20_util/forward/b.cc: Likewise.
+	* testsuite/20_util/forward/c_neg.cc: Likewise.
+	* testsuite/20_util/forward/d.cc: Likewise.
+	* testsuite/20_util/forward/e.cc: Likewise.
+	* testsuite/20_util/forward/f_neg.cc: Likewise.
+
 2010-11-10  François Dumont  <francois.cppdevs@free.fr>
 
 	* include/profile/unordered_map (unordered_map<>::_M_profile_size):
diff --git a/libstdc++-v3/include/bits/move.h b/libstdc++-v3/include/bits/move.h
index 9329cb4..f351d01 100644
--- a/libstdc++-v3/include/bits/move.h
+++ b/libstdc++-v3/include/bits/move.h
@@ -51,29 +51,20 @@ _GLIBCXX_END_NAMESPACE
 
 _GLIBCXX_BEGIN_NAMESPACE(std)
   
-  /// forward (as per N2835)
-  /// Forward lvalues as rvalues.
+  /// forward (as per N3143)
   template<typename _Tp>
-    inline typename enable_if<!is_lvalue_reference<_Tp>::value, _Tp&&>::type
-    forward(typename std::common_type<_Tp>::type& __t)
+    inline _Tp&&
+    forward(typename std::remove_reference<_Tp>::type& __t) 
     { return static_cast<_Tp&&>(__t); }
 
-  /// Forward rvalues as rvalues.
   template<typename _Tp>
-    inline typename enable_if<!is_lvalue_reference<_Tp>::value, _Tp&&>::type
-    forward(typename std::common_type<_Tp>::type&& __t)
-    { return static_cast<_Tp&&>(__t); }
-
-  // Forward lvalues as lvalues.
-  template<typename _Tp>
-    inline typename enable_if<is_lvalue_reference<_Tp>::value, _Tp>::type
-    forward(typename std::common_type<_Tp>::type __t)
-    { return __t; }
-
-  // Prevent forwarding rvalues as const lvalues.
-  template<typename _Tp>
-    inline typename enable_if<is_lvalue_reference<_Tp>::value, _Tp>::type
-    forward(typename std::remove_reference<_Tp>::type&& __t) = delete;
+    inline _Tp&&
+    forward(typename std::remove_reference<_Tp>::type&& __t) 
+    {
+      static_assert(!std::is_lvalue_reference<_Tp>::value, "template argument"
+		    " substituting _Tp is an lvalue reference type");
+      return static_cast<_Tp&&>(__t);
+    }
 
   /**
    *  @brief Move a value.
diff --git a/libstdc++-v3/testsuite/20_util/forward/a.cc b/libstdc++-v3/testsuite/20_util/forward/a.cc
new file mode 100644
index 0000000..296c9f4
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/forward/a.cc
@@ -0,0 +1,77 @@
+// { dg-options "-std=gnu++0x" }
+
+// Copyright (C) 2010 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 <list>
+#include <testsuite_hooks.h>
+
+template <class T>
+  struct C
+  {
+    T t_;
+
+    template <class U,
+              class = typename std::enable_if
+                    <
+                        !std::is_lvalue_reference<U>::value
+                    >::type>
+      C(U&& u) : t_(std::forward<T>(std::move(u).get())) {}
+  };
+
+class A
+{
+  int data_;
+public:
+  explicit
+  A(int data = 1)
+  : data_(data) {}
+  
+  ~A() { data_ = -1; }
+
+  void test() const
+  {
+    bool test __attribute__((unused)) = true;
+    VERIFY( data_ == 3 );
+  }
+};
+
+class Awrap
+{
+  const A& a_;
+public:
+  explicit Awrap(const A& a) : a_(a) { }
+  const A& get() const { return a_; }
+};
+
+template <class C>
+  void test(C c)
+  {
+    c.t_.test();
+  }
+
+// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2951.html
+// Test A.
+int main()
+{
+  std::list<C<const A&> > list;
+  A a(3);
+  C<const A&> c((Awrap(a)));
+  list.push_back(c);
+  test(c);
+  test(list.front());
+}
diff --git a/libstdc++-v3/testsuite/20_util/forward/b.cc b/libstdc++-v3/testsuite/20_util/forward/b.cc
new file mode 100644
index 0000000..4168800
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/forward/b.cc
@@ -0,0 +1,77 @@
+// { dg-options "-std=gnu++0x" }
+
+// Copyright (C) 2010 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 <list>
+#include <testsuite_hooks.h>
+
+template <class T>
+  struct C
+  {
+    T t_;
+
+    template <class U,
+              class = typename std::enable_if
+                    <
+                        !std::is_lvalue_reference<U>::value
+                    >::type>
+      C(U&& u) : t_(std::forward<T>(std::move(u).get())) {}
+  };
+
+class A
+{
+  int data_;
+public:
+  explicit
+  A(int data = 1)
+  : data_(data) { }
+
+  ~A() { data_ = -1; }
+
+  void test() const
+  {
+    bool test __attribute__((unused)) = true;
+    VERIFY( data_ == 3 );
+  }
+};
+
+class Awrap
+{
+  A a_;
+public:
+  explicit Awrap(const A& a) : a_(a) { }
+  A get() const { return a_; }
+};
+
+template <class C>
+void test(C c)
+{
+  c.t_.test();
+}
+
+// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2951.html
+// Test B.
+int main()
+{
+  std::list<C<A> > list;
+  A a(3);
+  C<A> c((Awrap(a)));
+  list.push_back(c);
+  test(c);
+  test(list.front());
+}
diff --git a/libstdc++-v3/testsuite/20_util/forward/c_neg.cc b/libstdc++-v3/testsuite/20_util/forward/c_neg.cc
new file mode 100644
index 0000000..919fe56
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/forward/c_neg.cc
@@ -0,0 +1,78 @@
+// { dg-do compile }
+// { dg-options "-std=gnu++0x" }
+
+// Copyright (C) 2010 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-error "static assertion failed" "" { target *-*-* } 64 }
+
+#include <list>
+
+template <class T>
+  struct C
+  {
+    T t_;
+
+    template <class U,
+	      class = typename std::enable_if
+                    <
+	                !std::is_lvalue_reference<U>::value
+                    >::type>
+      C(U&& u) : t_(std::forward<T>(std::move(u).get())) {}
+  };
+
+class A
+{
+  int data_;
+public:
+  explicit
+  A(int data = 1)
+  : data_(data) { }
+
+  ~A() { data_ = -1; }
+
+  void test() const
+  {
+    __builtin_abort();
+  }
+};
+
+class Awrap
+{
+  const A& a_;
+public:
+  explicit Awrap(const A& a) : a_(a) {}
+  const A /* & */ get() const { return a_; }
+};
+
+template <class C>
+  void test(C c)
+  {
+    c.t_.test();
+  }
+
+// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2951.html
+// Test C.
+int main()
+{
+  std::list<C<const A&> > list;
+  A a(3);
+  C<const A&> c((Awrap(a)));
+  list.push_back(c);
+  test(c);
+  test(list.front());
+}
diff --git a/libstdc++-v3/testsuite/20_util/forward/d.cc b/libstdc++-v3/testsuite/20_util/forward/d.cc
new file mode 100644
index 0000000..c2c7eb3
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/forward/d.cc
@@ -0,0 +1,78 @@
+// { dg-options "-std=gnu++0x" }
+
+// Copyright (C) 2010 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 <list>
+#include <testsuite_hooks.h>
+
+template <class T>
+  struct C
+  {
+    T t_;
+
+    template <class U,
+              class = typename std::enable_if
+                    <
+                        !std::is_lvalue_reference<U>::value
+                    >::type>
+      C(U&& u) : t_(std::forward<T>(std::move(u).get())) { }
+  };
+
+class A
+{
+  int data_;
+public:
+  explicit
+  A(int data = 1)
+  : data_(data) { }
+
+  ~A() { data_ = -1; }
+
+  void test() const
+  {
+    bool test __attribute__((unused)) = true;
+    VERIFY( data_ == 3 );
+  }
+};
+
+class Awrap
+{
+  A& a_;
+public:
+  explicit Awrap(A& a) : a_(a) { }
+  const A& get() const { return a_; }
+        A& get()       { return a_; }
+};
+
+template <class C>
+  void test(C c)
+  {
+    c.t_.test();
+  }
+
+// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2951.html
+// Test D.
+int main()
+{
+  std::list<C<const A&> > list;
+  A a(3);
+  C<const A&> c((Awrap(a)));
+  list.push_back(c);
+  test(c);
+  test(list.front());
+}
diff --git a/libstdc++-v3/testsuite/20_util/forward/e.cc b/libstdc++-v3/testsuite/20_util/forward/e.cc
new file mode 100644
index 0000000..4d89cd1
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/forward/e.cc
@@ -0,0 +1,54 @@
+// { dg-do compile }
+// { dg-options "-std=gnu++0x" }
+
+// Copyright (C) 2010 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 <utility>
+
+template <class T>
+  struct C
+  {
+    T t_;
+
+    C() { }
+
+    template <class U,
+              class = typename std::enable_if
+                    <
+                        !std::is_lvalue_reference<U>::value
+                    >::type>
+      C(U&& u) : t_(std::forward<T>(std::move(u).get())) { }
+
+    C(C&& c) : t_(std::forward<T>(c.t_)) { }
+  };
+
+template <class T>
+  struct Derived
+  : C<T>
+  {
+    Derived() { }
+    Derived(Derived&& d) : C<T>(std::forward<C<T>>(d)) { }
+  };
+
+// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2951.html
+// Test E.
+int main()
+{
+  Derived<int> d;
+  Derived<int> d2(std::move(d));
+}
diff --git a/libstdc++-v3/testsuite/20_util/forward/f_neg.cc b/libstdc++-v3/testsuite/20_util/forward/f_neg.cc
new file mode 100644
index 0000000..6b5a365
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/forward/f_neg.cc
@@ -0,0 +1,90 @@
+// { dg-do compile }
+// { dg-options "-std=gnu++0x" }
+
+// Copyright (C) 2010 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-error "static assertion failed" "" { target *-*-* } 64 }
+
+#include <utility>
+
+template <class T>
+  struct C
+  {
+    T t_;
+
+    C() {}
+
+    explicit C(const T& t) : t_(t) { }
+
+    template <class U,
+              class = typename std::enable_if
+                    <
+                        std::is_convertible<U, T>::value
+                    >::type>
+      C(C<U>&& c) : t_(std::forward<T>(c.t_)) { }
+  };
+
+class B;
+
+class A
+{
+  int data_;
+
+  friend class B;
+public:
+  explicit
+  A(int data = 1)
+  : data_(data) { }
+
+  ~A() { data_ = -1; }
+
+  void test() const
+  {
+    __builtin_abort();
+  }
+};
+
+class B
+{
+  int data_;
+public:
+  explicit
+  B(int data = 1)
+  : data_(data) { }
+
+  B(const A& a) : data_(a.data_) { }
+
+  B(A&& a) : data_(a.data_) { a.data_ = 100; }
+
+  ~B() { data_ = -1; }
+
+  void test() const
+  {
+    __builtin_abort();
+  }
+};
+
+// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2951.html
+// Test F.
+int main()
+{
+  A a(3);
+  C<A> ca(a);
+  C<const B&> cb(std::move(ca));
+  cb.t_.test();
+}