Missed this on the previous (255517) commit

llvm-svn: 255518

libcxx/include/type_traits

@@ -396,6 +396,55 @@ template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY enable_if<true, _Tp> {typedef
 template <bool _Bp, class _Tp = void> using enable_if_t = typename enable_if<_Bp, _Tp>::type;
 #endif
 
+// addressof
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+_Tp*
+addressof(_Tp& __x) _NOEXCEPT
+{
+    return (_Tp*)&reinterpret_cast<const volatile char&>(__x);
+}
+
+#if defined(_LIBCPP_HAS_OBJC_ARC) && !defined(_LIBCPP_PREDEFINED_OBJC_ARC_ADDRESSOF)
+// Objective-C++ Automatic Reference Counting uses qualified pointers
+// that require special addressof() signatures. When
+// _LIBCPP_PREDEFINED_OBJC_ARC_ADDRESSOF is defined, the compiler
+// itself is providing these definitions. Otherwise, we provide them.
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+__strong _Tp*
+addressof(__strong _Tp& __x) _NOEXCEPT
+{
+  return &__x;
+}
+
+#ifdef _LIBCPP_HAS_OBJC_ARC_WEAK
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+__weak _Tp*
+addressof(__weak _Tp& __x) _NOEXCEPT
+{
+  return &__x;
+}
+#endif
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+__autoreleasing _Tp*
+addressof(__autoreleasing _Tp& __x) _NOEXCEPT
+{
+  return &__x;
+}
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+__unsafe_unretained _Tp*
+addressof(__unsafe_unretained _Tp& __x) _NOEXCEPT
+{
+  return &__x;
+}
+#endif
 
 struct __two {char __lx[2];};