Example conversion for optional, using [[trivially_relocatable]].

Quuxplusone · Nov 19, 2018 · ccae878 · ccae878
1 parent 999b73a
commit ccae878
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Showing 2 changed files with 22 additions and 2 deletions.
diff --git a/include/__config b/include/__config
@@ -1281,6 +1281,14 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
 #define _LIBCPP_HAS_NO_IS_AGGREGATE
 #endif
 
+#ifndef _LIBCPP_TRIVIALLY_RELOCATABLE
+#if __has_extension(trivially_relocatable)
+#define _LIBCPP_TRIVIALLY_RELOCATABLE [[clang::trivially_relocatable]]
+#else
+#define _LIBCPP_TRIVIALLY_RELOCATABLE
+#endif
+#endif
+
 #if !defined(__cpp_coroutines) || __cpp_coroutines < 201703L
 #define _LIBCPP_HAS_NO_COROUTINES
 #endif

diff --git a/include/optional b/include/optional
@@ -580,13 +580,25 @@ using __optional_sfinae_assign_base_t = __sfinae_assign_base<
     (is_move_constructible<_Tp>::value && is_move_assignable<_Tp>::value)
 >;
 
+template <class _Tp, bool = is_trivially_relocatable<_Tp>::value>
+struct __optional_relocate_base : __optional_move_assign_base<_Tp>
+{
+    using __optional_move_assign_base<_Tp>::__optional_move_assign_base;
+};
+
+template <class _Tp>
+struct _LIBCPP_TRIVIALLY_RELOCATABLE __optional_relocate_base<_Tp, true> : __optional_move_assign_base<_Tp>
+{
+    using __optional_move_assign_base<_Tp>::__optional_move_assign_base;
+};
+
 template <class _Tp>
 class optional
-    : private __optional_move_assign_base<_Tp>
+    : private __optional_relocate_base<_Tp>
     , private __optional_sfinae_ctor_base_t<_Tp>
     , private __optional_sfinae_assign_base_t<_Tp>
 {
-    using __base = __optional_move_assign_base<_Tp>;
+    using __base = __optional_relocate_base<_Tp>;
 public:
     using value_type = _Tp;