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[libc++] Remove some of the uses of aligned_storage inside the library #161635

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[libc++] Remove some of the uses of aligned_storage inside the library #161635

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3 changes: 1 addition & 2 deletions libcxx/include/__memory/temp_value.h
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,6 @@
#include <__config>
#include <__memory/addressof.h>
#include <__memory/allocator_traits.h>
#include <__type_traits/aligned_storage.h>
#include <__utility/forward.h>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
Expand All @@ -26,7 +25,7 @@ struct __temp_value {
typedef allocator_traits<_Alloc> _Traits;

#ifdef _LIBCPP_CXX03_LANG
typename aligned_storage<sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp)>::type __v;
_ALIGNAS_TYPE(_Tp) char __v[sizeof(_Tp)];
#else
union {
_Tp __v;
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10 changes: 4 additions & 6 deletions libcxx/include/any
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Expand Up @@ -90,7 +90,6 @@ namespace std {
# include <__memory/unique_ptr.h>
# include <__type_traits/add_cv_quals.h>
# include <__type_traits/add_pointer.h>
# include <__type_traits/aligned_storage.h>
# include <__type_traits/conditional.h>
# include <__type_traits/decay.h>
# include <__type_traits/enable_if.h>
Expand Down Expand Up @@ -148,14 +147,13 @@ template <class _ValueType>
_LIBCPP_HIDE_FROM_ABI add_pointer_t<_ValueType> any_cast(any*) _NOEXCEPT;

namespace __any_imp {
_LIBCPP_SUPPRESS_DEPRECATED_PUSH
using _Buffer _LIBCPP_NODEBUG = aligned_storage_t<3 * sizeof(void*), alignof(void*)>;
_LIBCPP_SUPPRESS_DEPRECATED_POP
inline constexpr size_t __small_buffer_size = 3 * sizeof(void*);
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I found the previous code easier to read since we did sizeof(_Buffer) and alignof(_Buffer) below. What would you think of using _Buffer = alignas(alignment) char [size] instead?

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You can't put alignas on an alias.

inline constexpr size_t __small_buffer_alignment = alignof(void*);

template <class _Tp>
using _IsSmallObject _LIBCPP_NODEBUG =
integral_constant<bool,
sizeof(_Tp) <= sizeof(_Buffer) && alignof(_Buffer) % alignof(_Tp) == 0 &&
sizeof(_Tp) <= __small_buffer_size && alignof(_Tp) <= __small_buffer_alignment &&
is_nothrow_move_constructible<_Tp>::value >;

enum class _Action { _Destroy, _Copy, _Move, _Get, _TypeInfo };
Expand Down Expand Up @@ -285,7 +283,7 @@ private:
union _Storage {
_LIBCPP_HIDE_FROM_ABI constexpr _Storage() : __ptr(nullptr) {}
void* __ptr;
__any_imp::_Buffer __buf;
alignas(__any_imp::__small_buffer_alignment) char __buf[__any_imp::__small_buffer_size];
};

_LIBCPP_HIDE_FROM_ABI void*
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5 changes: 1 addition & 4 deletions libcxx/include/future
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Expand Up @@ -583,12 +583,9 @@ inline future_status __assoc_sub_state::wait_for(const chrono::duration<_Rep, _P
template <class _Rp>
class _LIBCPP_HIDDEN __assoc_state : public __assoc_sub_state {
typedef __assoc_sub_state base;
_LIBCPP_SUPPRESS_DEPRECATED_PUSH
typedef typename aligned_storage<sizeof(_Rp), _LIBCPP_ALIGNOF(_Rp)>::type _Up;
_LIBCPP_SUPPRESS_DEPRECATED_POP

protected:
_Up __value_;
_ALIGNAS_TYPE(_Rp) char __value_[sizeof(_Rp)];

_LIBCPP_HIDE_FROM_ABI_VIRTUAL void __on_zero_shared() _NOEXCEPT override;

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