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

Quuxplusone · Quuxplusone · commit 1df78ab704b8 · 2018-11-19T16:16:40.000-05:00
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 [[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/deque b/include/deque
@@ -952,6 +952,13 @@ protected:
     typedef __deque_iterator<value_type, const_pointer, const_reference, __map_const_pointer,
                              difference_type>    const_iterator;
 
+public:
+    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
+    > __allow_trivial_relocation;
 protected:
     __map __map_;
     size_type __start_;
@@ -1190,9 +1197,43 @@ __deque_base<_Tp, _Allocator>::clear() _NOEXCEPT
     }
 }
 
+template <class _Tp, class _Allocator, bool = __deque_base<_Tp, _Allocator>::__allow_trivial_relocation::value>
+class _LIBCPP_TEMPLATE_VIS __deque_relocate_base
+    : protected __deque_base<_Tp, _Allocator>
+{
+protected:
+#ifndef _LIBCPP_CXX03_LANG
+    using __deque_base<_Tp, _Allocator>::__deque_base;
+#else
+    _LIBCPP_INLINE_VISIBILITY
+    __deque_relocate_base() = default;
+
+    _LIBCPP_INLINE_VISIBILITY
+    __deque_relocate_base(const _Allocator& __a)
+        : __deque_base<_Tp, _Allocator>(__a) {}
+#endif  // _LIBCPP_CXX03_LANG
+};
+
+template <class _Tp, class _Allocator>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_TRIVIALLY_RELOCATABLE __deque_relocate_base<_Tp, _Allocator, true>
+    : protected __deque_base<_Tp, _Allocator>
+{
+protected:
+#ifndef _LIBCPP_CXX03_LANG
+    using __deque_base<_Tp, _Allocator>::__deque_base;
+#else
+    _LIBCPP_INLINE_VISIBILITY
+    __deque_relocate_base() = default;
+
+    _LIBCPP_INLINE_VISIBILITY
+    __deque_relocate_base(const _Allocator& __a)
+        : __deque_base<_Tp, _Allocator>(__a) {}
+#endif  // _LIBCPP_CXX03_LANG
+};
+
 template <class _Tp, class _Allocator /*= allocator<_Tp>*/>
 class _LIBCPP_TEMPLATE_VIS deque
-    : private __deque_base<_Tp, _Allocator>
+    : private __deque_relocate_base<_Tp, _Allocator>
 {
 public:
     // types:
@@ -1203,6 +1244,7 @@ public:
     static_assert((is_same<typename allocator_type::value_type, value_type>::value),
                   "Allocator::value_type must be same type as value_type");
 
+    typedef __deque_relocate_base<value_type, allocator_type> __relocate_base;
     typedef __deque_base<value_type, allocator_type> __base;
 
     typedef typename __base::__alloc_traits        __alloc_traits;
@@ -1223,7 +1265,7 @@ public:
     deque()
         _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
         {}
-    _LIBCPP_INLINE_VISIBILITY explicit deque(const allocator_type& __a) : __base(__a) {}
+    _LIBCPP_INLINE_VISIBILITY explicit deque(const allocator_type& __a) : __relocate_base(__a) {}
     explicit deque(size_type __n);
 #if _LIBCPP_STD_VER > 11
     explicit deque(size_type __n, const _Allocator& __a);
@@ -1249,7 +1291,7 @@ public:
     deque& operator=(initializer_list<value_type> __il) {assign(__il); return *this;}
 
     _LIBCPP_INLINE_VISIBILITY
-    deque(deque&& __c) _NOEXCEPT_(is_nothrow_move_constructible<__base>::value);
+    deque(deque&& __c) = default;
     _LIBCPP_INLINE_VISIBILITY
     deque(deque&& __c, const allocator_type& __a);
     _LIBCPP_INLINE_VISIBILITY
@@ -1495,7 +1537,7 @@ deque<_Tp, _Allocator>::deque(size_type __n)
 #if _LIBCPP_STD_VER > 11
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(size_type __n, const _Allocator& __a)
-    : __base(__a)
+    : __relocate_base(__a)
 {
     if (__n > 0)
         __append(__n);
@@ -1511,7 +1553,7 @@ deque<_Tp, _Allocator>::deque(size_type __n, const value_type& __v)
 
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(size_type __n, const value_type& __v, const allocator_type& __a)
-    : __base(__a)
+    : __relocate_base(__a)
 {
     if (__n > 0)
         __append(__n, __v);
@@ -1529,21 +1571,21 @@ template <class _Tp, class _Allocator>
 template <class _InputIter>
 deque<_Tp, _Allocator>::deque(_InputIter __f, _InputIter __l, const allocator_type& __a,
               typename enable_if<__is_input_iterator<_InputIter>::value>::type*)
-    : __base(__a)
+    : __relocate_base(__a)
 {
     __append(__f, __l);
 }
 
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(const deque& __c)
-    : __base(__alloc_traits::select_on_container_copy_construction(__c.__alloc()))
+    : __relocate_base(__alloc_traits::select_on_container_copy_construction(__c.__alloc()))
 {
     __append(__c.begin(), __c.end());
 }
 
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(const deque& __c, const allocator_type& __a)
-    : __base(__a)
+    : __relocate_base(__a)
 {
     __append(__c.begin(), __c.end());
 }
@@ -1570,23 +1612,15 @@ deque<_Tp, _Allocator>::deque(initializer_list<value_type> __il)
 
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(initializer_list<value_type> __il, const allocator_type& __a)
-    : __base(__a)
+    : __relocate_base(__a)
 {
     __append(__il.begin(), __il.end());
 }
 
-template <class _Tp, class _Allocator>
-inline
-deque<_Tp, _Allocator>::deque(deque&& __c)
-    _NOEXCEPT_(is_nothrow_move_constructible<__base>::value)
-    : __base(_VSTD::move(__c))
-{
-}
-
 template <class _Tp, class _Allocator>
 inline
 deque<_Tp, _Allocator>::deque(deque&& __c, const allocator_type& __a)
-    : __base(_VSTD::move(__c), __a)
+    : __relocate_base(_VSTD::move(__c), __a)
 {
     if (__a != __c.__alloc())
     {
