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[libc++] Refactor memory allocation in basic_string #128423

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Merged
merged 1 commit into from
Sep 18, 2025
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[libc++] Refactor memory allocation in basic_string #128423

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25 changes: 15 additions & 10 deletions libcxx/include/__memory/allocate_at_least.h
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Original file line number Diff line number Diff line change
Expand Up @@ -19,26 +19,31 @@

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _Pointer, class _SizeT = size_t>
struct __allocation_result {
_Pointer ptr;
_SizeT count;

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __allocation_result(_Pointer __ptr, _SizeT __count)
: ptr(__ptr), count(__count) {}
};
_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(__allocation_result);

#if _LIBCPP_STD_VER >= 23

template <class _Alloc>
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto __allocate_at_least(_Alloc& __alloc, size_t __n) {
return std::allocator_traits<_Alloc>::allocate_at_least(__alloc, __n);
auto __res = std::allocator_traits<_Alloc>::allocate_at_least(__alloc, __n);
return __allocation_result{__res.ptr, __res.count};
}

#else

template <class _Pointer>
struct __allocation_result {
_Pointer ptr;
size_t count;
};

template <class _Alloc>
template <class _Alloc, class _Traits = allocator_traits<_Alloc> >
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI
_LIBCPP_CONSTEXPR __allocation_result<typename allocator_traits<_Alloc>::pointer>
_LIBCPP_CONSTEXPR __allocation_result<typename _Traits::pointer, typename _Traits::size_type>
__allocate_at_least(_Alloc& __alloc, size_t __n) {
return {__alloc.allocate(__n), __n};
return __allocation_result<typename _Traits::pointer, typename _Traits::size_type>(__alloc.allocate(__n), __n);
}

#endif // _LIBCPP_STD_VER >= 23
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