--- /dev/null
+// Copyright (C) 2005, 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 <algorithm>
+#include <vector>
+#include <testsuite_hooks.h>
+
+void
+test1()
+{
+ bool test __attribute__((unused)) = true;
+
+ std::vector<bool> v;
+ v.push_back(true);
+ v.push_back(false);
+ std::iter_swap(v.begin(), v.begin() + 1);
+ VERIFY( v[0] == false && v[1] == true );
+}
+
+void
+test2()
+{
+ bool test __attribute__((unused)) = true;
+
+ std::vector<int> v;
+ v.push_back(1);
+ v.push_back(2);
+ std::iter_swap(v.begin(), v.begin() + 1);
+ VERIFY( v[0] == 2 && v[1] == 1 );
+}
+
+int int_swap_count;
+
+struct X {};
+void swap(X&, X&)
+{ ++int_swap_count; }
+
+void
+test3()
+{
+ bool test __attribute__((unused)) = true;
+
+ int_swap_count = 0;
+ X i, j;
+ std::iter_swap(&i, &j);
+ VERIFY( int_swap_count == 1 );
+}
+
+// libstdc++/20577
+int main()
+{
+ test1();
+ test2();
+ test3();
+ return 0;
+}