1 files changed, 85 insertions, 0 deletions
diff --git a/test/std/strings/basic.string/string.nonmembers/string.special/swap_noexcept.pass.cpp b/test/std/strings/basic.string/string.nonmembers/string.special/swap_noexcept.pass.cpp
new file mode 100644
index 0000000000000..cfe03655a8a16
--- /dev/null
+++ b/test/std/strings/basic.string/string.nonmembers/string.special/swap_noexcept.pass.cpp
@@ -0,0 +1,85 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <string>
+
+// void swap(basic_string& c)
+//     noexcept(!allocator_type::propagate_on_container_swap::value ||
+//              __is_nothrow_swappable<allocator_type>::value);
+//
+//  In C++17, the standard says that swap shall have:
+//     noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value ||
+//              allocator_traits<Allocator>::is_always_equal::value);
+
+// This tests a conforming extension
+
+#include <string>
+#include <cassert>
+
+#include "test_allocator.h"
+
+template <class T>
+struct some_alloc
+{
+    typedef T value_type;
+    
+    some_alloc() {}
+    some_alloc(const some_alloc&);
+    void deallocate(void*, unsigned) {}
+
+    typedef std::true_type propagate_on_container_swap;
+};
+
+template <class T>
+struct some_alloc2
+{
+    typedef T value_type;
+    
+    some_alloc2() {}
+    some_alloc2(const some_alloc2&);
+    void deallocate(void*, unsigned) {}
+
+    typedef std::false_type propagate_on_container_swap;
+    typedef std::true_type is_always_equal;
+};
+
+int main()
+{
+#if __has_feature(cxx_noexcept)
+    {
+        typedef std::string C;
+        C c1, c2;
+        static_assert(noexcept(swap(c1, c2)), "");
+    }
+    {
+        typedef std::basic_string<char, std::char_traits<char>, test_allocator<char>> C;
+        C c1, c2;
+        static_assert(noexcept(swap(c1, c2)), "");
+    }
+    {
+        typedef std::basic_string<char, std::char_traits<char>, some_alloc<char>> C;
+        C c1, c2;
+#if TEST_STD_VER >= 14
+    //  In c++14, if POCS is set, swapping the allocator is required not to throw
+        static_assert( noexcept(swap(c1, c2)), "");
+#else
+        static_assert(!noexcept(swap(c1, c2)), "");
+#endif
+    }
+#if TEST_STD_VER >= 14
+    {
+        typedef std::basic_string<char, std::char_traits<char>, some_alloc2<char>> C;
+        C c1, c2;
+    //  if the allocators are always equal, then the swap can be noexcept
+        static_assert( noexcept(swap(c1, c2)), "");
+    }
+#endif
+
+#endif
+}