Example conversion for deque, using [[trivially_relocatable(bool)]].

Quuxplusone · Quuxplusone · commit 5caede0e633d · 2019-01-18T13:20:30.000-05:00
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(x) [[clang::trivially_relocatable(x)]]
+#else
+#define _LIBCPP_TRIVIALLY_RELOCATABLE(x)
+#endif
+#endif
+
 #if !defined(__cpp_coroutines) || __cpp_coroutines < 201703L
 #define _LIBCPP_HAS_NO_COROUTINES
 #endif
diff --git a/include/deque b/include/deque
@@ -920,6 +920,22 @@ __deque_base_common<__b>::__throw_out_of_range() const
     _VSTD::__throw_out_of_range("deque");
 }
 
+template <class _Allocator>
+struct __deque_allow_trivial_relocation {
+    typedef _Allocator                               allocator_type;
+    typedef allocator_traits<allocator_type>         __alloc_traits;
+    typedef typename __alloc_traits::pointer         pointer;
+    typedef typename __alloc_traits::size_type       size_type;
+    typedef typename __rebind_alloc_helper<__alloc_traits, pointer>::type __pointer_allocator;
+
+    typedef integral_constant<bool,
+        is_trivially_relocatable<pointer>::value &&
+        is_trivially_relocatable<__pointer_allocator>::value &&
+        is_trivially_relocatable<size_type>::value &&
+        is_trivially_relocatable<allocator_type>::value
+    > type;
+};
+
 template <class _Tp, class _Allocator>
 class __deque_base
     : protected __deque_base_common<true>
@@ -1191,7 +1207,7 @@ __deque_base<_Tp, _Allocator>::clear() _NOEXCEPT
 }
 
 template <class _Tp, class _Allocator /*= allocator<_Tp>*/>
-class _LIBCPP_TEMPLATE_VIS deque
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_TRIVIALLY_RELOCATABLE(__deque_allow_trivial_relocation<_Allocator>::type::value) deque
     : private __deque_base<_Tp, _Allocator>
 {
 public:
