[libc++] Fix PR35491 - std::array of zero-size doesn't work with non-default constructible types.
Summary:
This patch fixes llvm.org/PR35491 and LWG2157 (https://cplusplus.github.io/LWG/issue2157)
The fix attempts to maintain ABI compatibility by replacing the array with a instance of `aligned_storage`.
Reviewers: mclow.lists, EricWF
Reviewed By: EricWF
Subscribers: lichray, cfe-commits
Differential Revision: https://reviews.llvm.org/D41223
llvm-svn: 324182
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: afeda5c251f9a4696ab9178ecc6d4be7af72c105
diff --git a/include/array b/include/array
index 4eb2fe6..8cd3ecd 100644
--- a/include/array
+++ b/include/array
@@ -118,6 +118,55 @@
_LIBCPP_BEGIN_NAMESPACE_STD
template <class _Tp, size_t _Size>
+struct __array_traits {
+ typedef _Tp _StorageT[_Size];
+
+ _LIBCPP_INLINE_VISIBILITY
+ static _LIBCPP_CONSTEXPR_AFTER_CXX14 _Tp* __data(_StorageT& __store) {
+ return __store;
+ }
+
+ _LIBCPP_INLINE_VISIBILITY
+ static _LIBCPP_CONSTEXPR_AFTER_CXX14 _Tp const* __data(const _StorageT& __store) {
+ return __store;
+ }
+
+ _LIBCPP_INLINE_VISIBILITY
+ static void __swap(_StorageT& __lhs, _StorageT& __rhs) {
+ std::swap_ranges(__lhs, __lhs + _Size, __rhs);
+ }
+
+ _LIBCPP_INLINE_VISIBILITY
+ static void __fill(_StorageT& __arr, _Tp const& __val) {
+ _VSTD::fill_n(__arr, _Size, __val);
+ }
+};
+
+template <class _Tp>
+struct __array_traits<_Tp, 0> {
+ typedef typename aligned_storage<sizeof(_Tp), alignment_of<_Tp>::value>::type _StorageT;
+
+ _LIBCPP_INLINE_VISIBILITY
+ static _Tp* __data(_StorageT& __store) {
+ _StorageT *__ptr = std::addressof(__store);
+ return reinterpret_cast<_Tp*>(__ptr);
+ }
+
+ _LIBCPP_INLINE_VISIBILITY
+ static const _Tp* __data(const _StorageT& __store) {
+ const _StorageT *__ptr = std::addressof(__store);
+ return reinterpret_cast<const _Tp*>(__ptr);
+ }
+
+ _LIBCPP_INLINE_VISIBILITY
+ static void __swap(_StorageT&, _StorageT&) {}
+
+ _LIBCPP_INLINE_VISIBILITY
+ static void __fill(_StorageT&, _Tp const&) {
+ }
+};
+
+template <class _Tp, size_t _Size>
struct _LIBCPP_TEMPLATE_VIS array
{
// types:
@@ -134,31 +183,26 @@
typedef std::reverse_iterator<iterator> reverse_iterator;
typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
- value_type __elems_[_Size > 0 ? _Size : 1];
+ typedef __array_traits<_Tp, _Size> _Traits;
+ typename _Traits::_StorageT __elems_;
// No explicit construct/copy/destroy for aggregate type
_LIBCPP_INLINE_VISIBILITY void fill(const value_type& __u)
- {_VSTD::fill_n(__elems_, _Size, __u);}
+ {_Traits::__fill(__elems_, __u);}
+
_LIBCPP_INLINE_VISIBILITY
void swap(array& __a) _NOEXCEPT_(_Size == 0 || __is_nothrow_swappable<_Tp>::value)
- { __swap_dispatch((std::integral_constant<bool, _Size == 0>()), __a); }
-
- _LIBCPP_INLINE_VISIBILITY
- void __swap_dispatch(std::true_type, array&) {}
-
- _LIBCPP_INLINE_VISIBILITY
- void __swap_dispatch(std::false_type, array& __a)
- { _VSTD::swap_ranges(__elems_, __elems_ + _Size, __a.__elems_);}
+ { _Traits::__swap(__elems_, __a.__elems_); }
// iterators:
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
- iterator begin() _NOEXCEPT {return iterator(__elems_);}
+ iterator begin() _NOEXCEPT {return iterator(data());}
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
- const_iterator begin() const _NOEXCEPT {return const_iterator(__elems_);}
+ const_iterator begin() const _NOEXCEPT {return const_iterator(data());}
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
- iterator end() _NOEXCEPT {return iterator(__elems_ + _Size);}
+ iterator end() _NOEXCEPT {return iterator(data() + _Size);}
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
- const_iterator end() const _NOEXCEPT {return const_iterator(__elems_ + _Size);}
+ const_iterator end() const _NOEXCEPT {return const_iterator(data() + _Size);}
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
reverse_iterator rbegin() _NOEXCEPT {return reverse_iterator(end());}
@@ -201,9 +245,9 @@
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const_reference back() const {return __elems_[_Size > 0 ? _Size-1 : 0];}
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
- value_type* data() _NOEXCEPT {return __elems_;}
+ value_type* data() _NOEXCEPT {return _Traits::__data(__elems_);}
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
- const value_type* data() const _NOEXCEPT {return __elems_;}
+ const value_type* data() const _NOEXCEPT {return _Traits::__data(__elems_);}
};
template <class _Tp, size_t _Size>