5aaefa510e
libc++ has started splicing standard library headers into much more fine-grained content for maintainability. It's very likely that outdated and naive tooling (some of which is outside of LLVM's scope) will suggest users include things such as <__ranges/access.h> instead of <ranges>, and Hyrum's law suggests that users will eventually begin to rely on this without the help of tooling. As such, this commit intends to protect users from themselves, by making it a hard error for anyone outside of the standard library to include libc++ detail headers. Differential Revision: https://reviews.llvm.org/D106124
87 lines
2.6 KiB
C++
87 lines
2.6 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___NUMERIC_MIDPOINT_H
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#define _LIBCPP___NUMERIC_MIDPOINT_H
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#include <__config>
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#include <limits>
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#include <type_traits>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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# pragma clang include_instead(<numeric>)
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#endif
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_LIBCPP_PUSH_MACROS
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#include <__undef_macros>
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_LIBCPP_BEGIN_NAMESPACE_STD
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#if _LIBCPP_STD_VER > 17
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template <class _Tp>
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_LIBCPP_INLINE_VISIBILITY constexpr
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enable_if_t<is_integral_v<_Tp> && !is_same_v<bool, _Tp> && !is_null_pointer_v<_Tp>, _Tp>
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midpoint(_Tp __a, _Tp __b) noexcept
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_LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
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{
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using _Up = make_unsigned_t<_Tp>;
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constexpr _Up __bitshift = numeric_limits<_Up>::digits - 1;
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_Up __diff = _Up(__b) - _Up(__a);
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_Up __sign_bit = __b < __a;
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_Up __half_diff = (__diff / 2) + (__sign_bit << __bitshift) + (__sign_bit & __diff);
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return __a + __half_diff;
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}
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template <class _TPtr>
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_LIBCPP_INLINE_VISIBILITY constexpr
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enable_if_t<is_pointer_v<_TPtr>
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&& is_object_v<remove_pointer_t<_TPtr>>
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&& ! is_void_v<remove_pointer_t<_TPtr>>
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&& (sizeof(remove_pointer_t<_TPtr>) > 0), _TPtr>
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midpoint(_TPtr __a, _TPtr __b) noexcept
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{
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return __a + _VSTD::midpoint(ptrdiff_t(0), __b - __a);
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}
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template <typename _Tp>
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constexpr int __sign(_Tp __val) {
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return (_Tp(0) < __val) - (__val < _Tp(0));
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}
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template <typename _Fp>
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constexpr _Fp __fp_abs(_Fp __f) { return __f >= 0 ? __f : -__f; }
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template <class _Fp>
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_LIBCPP_INLINE_VISIBILITY constexpr
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enable_if_t<is_floating_point_v<_Fp>, _Fp>
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midpoint(_Fp __a, _Fp __b) noexcept
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{
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constexpr _Fp __lo = numeric_limits<_Fp>::min()*2;
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constexpr _Fp __hi = numeric_limits<_Fp>::max()/2;
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return __fp_abs(__a) <= __hi && __fp_abs(__b) <= __hi ? // typical case: overflow is impossible
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(__a + __b)/2 : // always correctly rounded
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__fp_abs(__a) < __lo ? __a + __b/2 : // not safe to halve a
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__fp_abs(__b) < __lo ? __a/2 + __b : // not safe to halve b
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__a/2 + __b/2; // otherwise correctly rounded
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}
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#endif // _LIBCPP_STD_VER > 17
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___NUMERIC_MIDPOINT_H
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