libstdc++: Fix regressions in unique_ptr::swap (PR 93562)

The requirements for this function are only that the deleter is
swappable, but we incorrectly require that the element type is complete
and that the deleter can be swapped using std::swap (which requires it
to be move cosntructible and move assignable).

The fix is to add __uniq_ptr_impl::swap which swaps the pointer and
deleter individually, instead of using the generic std::swap on the
tuple containing them.

	PR libstdc++/93562
	* include/bits/unique_ptr.h (__uniq_ptr_impl::swap): Define.
	(unique_ptr::swap, unique_ptr<T[], D>::swap): Call it.
	* testsuite/20_util/unique_ptr/modifiers/93562.cc: New test.

3 files changed, 117 insertions, 4 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index d875201..bb1c3ab 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,10 @@
+2020-02-04  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/93562
+	* include/bits/unique_ptr.h (__uniq_ptr_impl::swap): Define.
+	(unique_ptr::swap, unique_ptr<T[], D>::swap): Call it.
+	* testsuite/20_util/unique_ptr/modifiers/93562.cc: New test.
+
 2020-02-01  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* configure: Regenerate.
diff --git a/libstdc++-v3/include/bits/unique_ptr.h b/libstdc++-v3/include/bits/unique_ptr.h
index 131937a..d03266c 100644
--- a/libstdc++-v3/include/bits/unique_ptr.h
+++ b/libstdc++-v3/include/bits/unique_ptr.h
@@ -185,6 +185,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	return __p;
       }
 
+      void
+      swap(__uniq_ptr_impl& __rhs) noexcept
+      {
+	using std::swap;
+	swap(this->_M_ptr(), __rhs._M_ptr());
+	swap(this->_M_deleter(), __rhs._M_deleter());
+      }
+
     private:
       tuple<pointer, _Dp> _M_t;
     };
@@ -448,8 +456,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       void
       swap(unique_ptr& __u) noexcept
       {
-	using std::swap;
-	swap(_M_t, __u._M_t);
+	static_assert(__is_swappable<_Dp>::value, "deleter must be swappable");
+	_M_t.swap(__u._M_t);
       }
 
       // Disable copy from lvalue.
@@ -703,8 +711,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       void
       swap(unique_ptr& __u) noexcept
       {
-	using std::swap;
-	swap(_M_t, __u._M_t);
+	static_assert(__is_swappable<_Dp>::value, "deleter must be swappable");
+	_M_t.swap(__u._M_t);
       }
 
       // Disable copy from lvalue.
diff --git a/libstdc++-v3/testsuite/20_util/unique_ptr/modifiers/93562.cc b/libstdc++-v3/testsuite/20_util/unique_ptr/modifiers/93562.cc
new file mode 100644
index 0000000..8ed2363
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/unique_ptr/modifiers/93562.cc
@@ -0,0 +1,98 @@
+// Copyright (C) 2020 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 incomplete;
+
+// This function isn't called, we just need to check it compiles.
+void
+test01(std::unique_ptr<incomplete>& p1, std::unique_ptr<incomplete>& p2)
+{
+  // PR libstdc++/93562
+  p1.swap(p2);
+  swap(p1, p2);
+}
+
+// This function isn't called, we just need to check it compiles.
+void
+test02(std::unique_ptr<incomplete[]>& p1, std::unique_ptr<incomplete[]>& p2)
+{
+  // PR libstdc++/93562
+  p1.swap(p2);
+  swap(p1, p2);
+}
+
+namespace A
+{
+  struct Deleter
+  {
+    Deleter& operator=(const Deleter&) = delete;
+
+    void operator()(int* p) const noexcept { delete p; }
+
+    // found by ADL
+    friend void swap(Deleter& lhs, Deleter& rhs) noexcept
+    { std::swap(lhs.id, rhs.id); }
+
+    int id;
+  };
+
+  static_assert(!std::is_move_assignable<Deleter>::value, "not assignable");
+#if __cplusplus >= 201703L
+  static_assert(std::is_swappable_v<Deleter>, "but swappable");
+#endif
+} // namespace A
+
+void
+test03()
+{
+  std::unique_ptr<int, A::Deleter> p1(new int(1), { -1 });
+  std::unique_ptr<int, A::Deleter> p2(new int(2), { -2 });
+  int* const pi1 = p1.get();
+  int* const pi2 = p2.get();
+  // This type must swappable even though the deleter is not move-assignable:
+  swap(p1, p2);
+  VERIFY(p1.get() == pi2);
+  VERIFY(p1.get_deleter().id == -2);
+  VERIFY(p2.get() == pi1);
+  VERIFY(p2.get_deleter().id == -1);
+}
+
+void
+test04()
+{
+  std::unique_ptr<int[], A::Deleter> p1(new int[1]{1}, { -1 });
+  std::unique_ptr<int[], A::Deleter> p2(new int[2]{2, 2}, { -2 });
+  int* const pi1 = p1.get();
+  int* const pi2 = p2.get();
+  // This type must swappable even though the deleter is not move-assignable:
+  swap(p1, p2);
+  VERIFY(p1.get() == pi2);
+  VERIFY(p1.get_deleter().id == -2);
+  VERIFY(p2.get() == pi1);
+  VERIFY(p2.get_deleter().id == -1);
+}
+
+int main()
+{
+  test03();
+  test04();
+}