Support overaligned types in `aligned_storage`.
Summary:
The current implementation of aligned storage was written before we had `alignas`, so it used a list of builtin types to force the alignment. But this doesn't work overaligned requests.
This patch adds a fallback case supporting over-alignment. It only affects case that were previously ill-formed.
Reviewers: rsmith, ldionne, dlj, mclow.lists
Reviewed By: mclow.lists
Subscribers: mclow.lists, dexonsmith, libcxx-commits
Differential Revision: https://reviews.llvm.org/D61301
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@359596 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/type_traits b/include/type_traits
index a0bdb2b..d17bd09 100644
--- a/include/type_traits
+++ b/include/type_traits
@@ -1768,6 +1768,9 @@
__nat
> > > > > > > > > > __all_types;
+template <size_t _Align>
+struct _ALIGNAS(_Align) __fallback_overaligned {};
+
template <class _TL, size_t _Align> struct __find_pod;
template <class _Hp, size_t _Align>
@@ -1776,7 +1779,7 @@
typedef typename conditional<
_Align == _Hp::value,
typename _Hp::type,
- void
+ __fallback_overaligned<_Align>
>::type type;
};
@@ -1813,7 +1816,6 @@
struct _LIBCPP_TEMPLATE_VIS aligned_storage
{
typedef typename __find_pod<__all_types, _Align>::type _Aligner;
- static_assert(!is_void<_Aligner>::value, "");
union type
{
_Aligner __align;
diff --git a/test/std/utilities/meta/meta.trans/meta.trans.other/aligned_storage.pass.cpp b/test/std/utilities/meta/meta.trans/meta.trans.other/aligned_storage.pass.cpp
index 0b4aac3..e761532 100644
--- a/test/std/utilities/meta/meta.trans/meta.trans.other/aligned_storage.pass.cpp
+++ b/test/std/utilities/meta/meta.trans/meta.trans.other/aligned_storage.pass.cpp
@@ -285,6 +285,14 @@
static_assert(std::alignment_of<T1>::value == 8, "");
static_assert(sizeof(T1) == 16, "");
}
+ {
+ const int Align = 65536;
+ typedef typename std::aligned_storage<1, Align>::type T1;
+ static_assert(std::is_trivial<T1>::value, "");
+ static_assert(std::is_standard_layout<T1>::value, "");
+ static_assert(std::alignment_of<T1>::value == Align, "");
+ static_assert(sizeof(T1) == Align, "");
+ }
return 0;
}
