[v3] Implement P0513R0, Poisoning the Hash.

diff --git a/libstdc++-v3/include/bits/functional_hash.h b/libstdc++-v3/include/bits/functional_hash.h
index def35f5..dc09683 100644
--- a/libstdc++-v3/include/bits/functional_hash.h
+++ b/libstdc++-v3/include/bits/functional_hash.h
@@ -57,6 +57,20 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct hash;
 
+  template<typename _Tp, typename = void>
+    struct __poison_hash
+    {
+    private:
+      // Private rather than deleted to be non-trivially-copyable.
+      __poison_hash(__poison_hash&&);
+      ~__poison_hash();
+    };
+
+  template<typename _Tp>
+    struct __poison_hash<_Tp, __void_t<decltype(hash<_Tp>()(declval<_Tp>()))>>
+    {
+    };
+
   // Helper struct for SFINAE-poisoning non-enum types.
   template<typename _Tp, bool = is_enum<_Tp>::value>
     struct __hash_enum
diff --git a/libstdc++-v3/include/bits/unique_ptr.h b/libstdc++-v3/include/bits/unique_ptr.h
index 996c9ea..f9ec60f 100644
--- a/libstdc++-v3/include/bits/unique_ptr.h
+++ b/libstdc++-v3/include/bits/unique_ptr.h
@@ -36,6 +36,7 @@ 
 #include <utility>
 #include <tuple>
 #include <bits/stl_function.h>
+#include <bits/functional_hash.h>
 
 namespace std _GLIBCXX_VISIBILITY(default)
 {
@@ -763,7 +764,8 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
   /// std::hash specialization for unique_ptr.
   template<typename _Tp, typename _Dp>
     struct hash<unique_ptr<_Tp, _Dp>>
-    : public __hash_base<size_t, unique_ptr<_Tp, _Dp>>
+    : public __hash_base<size_t, unique_ptr<_Tp, _Dp>>,
+    private __poison_hash<typename unique_ptr<_Tp, _Dp>::pointer>
     {
       size_t
       operator()(const unique_ptr<_Tp, _Dp>& __u) const noexcept
diff --git a/libstdc++-v3/include/std/optional b/libstdc++-v3/include/std/optional
index f272876..69aa54d 100644
--- a/libstdc++-v3/include/std/optional
+++ b/libstdc++-v3/include/std/optional
@@ -990,7 +990,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
   // Hash.
   template<typename _Tp>
-    struct hash<optional<_Tp>>
+    struct hash<optional<_Tp>> : private __poison_hash<remove_const_t<_Tp>>
     {
       using result_type = size_t;
       using argument_type = optional<_Tp>;
diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant
index 314f5f2..004d667 100644
--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -41,6 +41,7 @@ 
 #include <bits/functexcept.h>
 #include <bits/move.h>
 #include <bits/uses_allocator.h>
+#include <bits/functional_hash.h>
 
 namespace std _GLIBCXX_VISIBILITY(default)
 {
@@ -1337,6 +1338,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
   template<typename... _Types>
     struct hash<variant<_Types...>>
+    : private __poison_hash<remove_const_t<_Types>>...
     {
       using result_type = size_t;
       using argument_type = variant<_Types...>;
diff --git a/libstdc++-v3/testsuite/20_util/optional/hash.cc b/libstdc++-v3/testsuite/20_util/optional/hash.cc
new file mode 100644
index 0000000..294a617
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/optional/hash.cc
@@ -0,0 +1,38 @@ 
+// { dg-options "-std=gnu++17" }
+
+// Copyright (C) 2016 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 moved_to of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <optional>
+#include <testsuite_hooks.h>
+
+class S{}; // No hash specialization
+
+template<class T>
+auto f(int) -> decltype(std::hash<std::optional<T>>(), std::true_type());
+
+template<class T>
+auto f(...) -> decltype(std::false_type());
+
+static_assert(!decltype(f<S>(0))::value, "");
+
+int main()
+{
+  int x = 42;
+  std::optional<int> x2 = 42;
+  VERIFY(std::hash<int>()(x) == std::hash<std::optional<int>>()(x2));
+}
diff --git a/libstdc++-v3/testsuite/20_util/unique_ptr/hash/1.cc b/libstdc++-v3/testsuite/20_util/unique_ptr/hash/1.cc
index 6fc4fdc..ae73a43 100644
--- a/libstdc++-v3/testsuite/20_util/unique_ptr/hash/1.cc
+++ b/libstdc++-v3/testsuite/20_util/unique_ptr/hash/1.cc
@@ -21,6 +21,29 @@ 
 
 #include <memory>
 #include <testsuite_hooks.h>
+#include <testsuite_allocator.h>
+
+// User-defined pointer type that throws if a null pointer is dereferenced.
+template<typename T>
+struct Pointer : __gnu_test::PointerBase<Pointer<T>, T>
+{
+};
+
+template<typename T>
+struct PointerDeleter : std::default_delete<T>
+{
+  typedef Pointer<T> pointer;
+  void operator()(pointer) const;
+};
+
+template<class T>
+auto f(int) -> decltype(std::hash<std::unique_ptr<T,
+			PointerDeleter<T>>>(), std::true_type());
+
+template<class T>
+auto f(...) -> decltype(std::false_type());
+
+static_assert(!decltype(f<Pointer<int>>(0))::value, "");
 
 void test01()
 {
diff --git a/libstdc++-v3/testsuite/20_util/variant/hash.cc b/libstdc++-v3/testsuite/20_util/variant/hash.cc
new file mode 100644
index 0000000..74f97ed
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/variant/hash.cc
@@ -0,0 +1,38 @@ 
+// { dg-options "-std=gnu++17" }
+
+// Copyright (C) 2016 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 moved_to of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <variant>
+#include <testsuite_hooks.h>
+
+class S{}; // No hash specialization
+
+template<class T>
+auto f(int) -> decltype(std::hash<std::variant<T>>(), std::true_type());
+
+template<class T>
+auto f(...) -> decltype(std::false_type());
+
+static_assert(!decltype(f<S>(0))::value, "");
+
+int main()
+{
+  int x = 42;
+  std::variant<int> x2 = 42;
+  VERIFY(std::hash<int>()(x) == std::hash<std::variant<int>>()(x2));
+}