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[libc++] Simplify the implementation of the pointer aliases in allocator_traits #127079

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merged 1 commit into from
Mar 28, 2025
Merged

[libc++] Simplify the implementation of the pointer aliases in allocator_traits #127079

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82 changes: 34 additions & 48 deletions libcxx/include/__memory/allocator_traits.h
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Original file line number Diff line number Diff line change
@@ -36,12 +36,6 @@ _LIBCPP_PUSH_MACROS

_LIBCPP_BEGIN_NAMESPACE_STD

#define _LIBCPP_ALLOCATOR_TRAITS_HAS_XXX(NAME, PROPERTY) \
template <class _Tp, class = void> \
struct NAME : false_type {}; \
template <class _Tp> \
struct NAME<_Tp, __void_t<typename _Tp::PROPERTY > > : true_type {}

_LIBCPP_SUPPRESS_DEPRECATED_PUSH
// __pointer
template <class _Tp>
@@ -50,51 +44,45 @@ using __pointer_member _LIBCPP_NODEBUG = typename _Tp::pointer;
template <class _Tp, class _Alloc>
using __pointer _LIBCPP_NODEBUG = __detected_or_t<_Tp*, __pointer_member, __libcpp_remove_reference_t<_Alloc> >;

// __const_pointer
_LIBCPP_ALLOCATOR_TRAITS_HAS_XXX(__has_const_pointer, const_pointer);
template <class _Tp, class _Ptr, class _Alloc, bool = __has_const_pointer<_Alloc>::value>
struct __const_pointer {
using type _LIBCPP_NODEBUG = typename _Alloc::const_pointer;
};
template <class _Tp, class _Ptr, class _Alloc>
struct __const_pointer<_Tp, _Ptr, _Alloc, false> {
// This trait returns _Alias<_Alloc> if that's well-formed, and _Ptr rebound to _Tp otherwise
template <class _Alloc, template <class> class _Alias, class _Ptr, class _Tp, class = void>
struct __rebind_or_alias_pointer {
#ifdef _LIBCPP_CXX03_LANG
using type _LIBCPP_NODEBUG = typename pointer_traits<_Ptr>::template rebind<const _Tp>::other;
using type _LIBCPP_NODEBUG = typename pointer_traits<_Ptr>::template rebind<_Tp>::other;
#else
using type _LIBCPP_NODEBUG = typename pointer_traits<_Ptr>::template rebind<const _Tp>;
using type _LIBCPP_NODEBUG = typename pointer_traits<_Ptr>::template rebind<_Tp>;
#endif
};

template <class _Ptr, class _Alloc, class _Tp, template <class> class _Alias>
struct __rebind_or_alias_pointer<_Alloc, _Alias, _Ptr, _Tp, __void_t<_Alias<_Alloc> > > {
using type _LIBCPP_NODEBUG = _Alias<_Alloc>;
};

// __const_pointer
template <class _Alloc>
using __const_pointer_member _LIBCPP_NODEBUG = typename _Alloc::const_pointer;

template <class _Tp, class _Ptr, class _Alloc>
using __const_pointer_t _LIBCPP_NODEBUG =
typename __rebind_or_alias_pointer<_Alloc, __const_pointer_member, _Ptr, const _Tp>::type;
_LIBCPP_SUPPRESS_DEPRECATED_POP

// __void_pointer
_LIBCPP_ALLOCATOR_TRAITS_HAS_XXX(__has_void_pointer, void_pointer);
template <class _Ptr, class _Alloc, bool = __has_void_pointer<_Alloc>::value>
struct __void_pointer {
using type _LIBCPP_NODEBUG = typename _Alloc::void_pointer;
};
template <class _Alloc>
using __void_pointer_member _LIBCPP_NODEBUG = typename _Alloc::void_pointer;

template <class _Ptr, class _Alloc>
struct __void_pointer<_Ptr, _Alloc, false> {
#ifdef _LIBCPP_CXX03_LANG
using type _LIBCPP_NODEBUG = typename pointer_traits<_Ptr>::template rebind<void>::other;
#else
using type _LIBCPP_NODEBUG = typename pointer_traits<_Ptr>::template rebind<void>;
#endif
};
using __void_pointer_t _LIBCPP_NODEBUG =
typename __rebind_or_alias_pointer<_Alloc, __void_pointer_member, _Ptr, void>::type;

// __const_void_pointer
_LIBCPP_ALLOCATOR_TRAITS_HAS_XXX(__has_const_void_pointer, const_void_pointer);
template <class _Ptr, class _Alloc, bool = __has_const_void_pointer<_Alloc>::value>
struct __const_void_pointer {
using type _LIBCPP_NODEBUG = typename _Alloc::const_void_pointer;
};
template <class _Alloc>
using __const_void_pointer_member _LIBCPP_NODEBUG = typename _Alloc::const_void_pointer;

template <class _Ptr, class _Alloc>
struct __const_void_pointer<_Ptr, _Alloc, false> {
#ifdef _LIBCPP_CXX03_LANG
using type _LIBCPP_NODEBUG = typename pointer_traits<_Ptr>::template rebind<const void>::other;
#else
using type _LIBCPP_NODEBUG = typename pointer_traits<_Ptr>::template rebind<const void>;
#endif
};
using __const_void_pointer_t _LIBCPP_NODEBUG =
typename __rebind_or_alias_pointer<_Alloc, __const_void_pointer_member, _Ptr, const void>::type;

// __size_type
template <class _Tp>
@@ -104,13 +92,13 @@ template <class _Alloc, class _DiffType>
using __size_type _LIBCPP_NODEBUG = __detected_or_t<__make_unsigned_t<_DiffType>, __size_type_member, _Alloc>;

// __alloc_traits_difference_type
_LIBCPP_ALLOCATOR_TRAITS_HAS_XXX(__has_alloc_traits_difference_type, difference_type);
template <class _Alloc, class _Ptr, bool = __has_alloc_traits_difference_type<_Alloc>::value>
template <class _Alloc, class _Ptr, class = void>
struct __alloc_traits_difference_type {
using type _LIBCPP_NODEBUG = typename pointer_traits<_Ptr>::difference_type;
};

template <class _Alloc, class _Ptr>
struct __alloc_traits_difference_type<_Alloc, _Ptr, true> {
struct __alloc_traits_difference_type<_Alloc, _Ptr, __void_t<typename _Alloc::difference_type> > {
using type _LIBCPP_NODEBUG = typename _Alloc::difference_type;
};

@@ -240,9 +228,9 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits {
using allocator_type = _Alloc;
using value_type = typename allocator_type::value_type;
using pointer = __pointer<value_type, allocator_type>;
using const_pointer = typename __const_pointer<value_type, pointer, allocator_type>::type;
using void_pointer = typename __void_pointer<pointer, allocator_type>::type;
using const_void_pointer = typename __const_void_pointer<pointer, allocator_type>::type;
using const_pointer = __const_pointer_t<value_type, pointer, allocator_type>;
using void_pointer = __void_pointer_t<pointer, allocator_type>;
using const_void_pointer = __const_void_pointer_t<pointer, allocator_type>;
using difference_type = typename __alloc_traits_difference_type<allocator_type, pointer>::type;
using size_type = __size_type<allocator_type, difference_type>;
using propagate_on_container_copy_assignment = __propagate_on_container_copy_assignment<allocator_type>;
@@ -386,8 +374,6 @@ inline const bool __is_cpp17_copy_insertable_v =
(!__is_std_allocator_v<_Alloc> &&
__has_construct_v<_Alloc, typename _Alloc::value_type*, const typename _Alloc::value_type&>));

#undef _LIBCPP_ALLOCATOR_TRAITS_HAS_XXX

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS