1 files changed, 37 insertions, 0 deletions
diff --git a/test/libcxx/libcpp_alignof.pass.cpp b/test/libcxx/libcpp_alignof.pass.cpp
new file mode 100644
index 0000000000000..ba0df807e82dd
--- /dev/null
+++ b/test/libcxx/libcpp_alignof.pass.cpp
@@ -0,0 +1,37 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// Test that _LIBCPP_ALIGNOF acts the same as the C++11 keyword `alignof`, and
+// not as the GNU extension `__alignof`. The former returns the minimal required
+// alignment for a type, whereas the latter returns the preferred alignment.
+//
+// See llvm.org/PR39713
+
+#include <type_traits>
+#include "test_macros.h"
+
+template <class T>
+void test() {
+  static_assert(_LIBCPP_ALIGNOF(T) == std::alignment_of<T>::value, "");
+  static_assert(_LIBCPP_ALIGNOF(T) == TEST_ALIGNOF(T), "");
+#if TEST_STD_VER >= 11
+  static_assert(_LIBCPP_ALIGNOF(T) == alignof(T), "");
+#endif
+#ifdef TEST_COMPILER_CLANG
+  static_assert(_LIBCPP_ALIGNOF(T) == _Alignof(T), "");
+#endif
+}
+
+int main() {
+  test<int>();
+  test<long long>();
+  test<double>();
+  test<long double>();
+}