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This checks whether a pointer is within a range, even during constant evaluation. This allows running optimized code paths during constant evaluation, instead of falling back to the general-purpose implementation all the time. This is also a central place for comparing unrelated pointers, which is technically UB. Reviewed By: ldionne, #libc Spies: libcxx-commits Differential Revision: https://reviews.llvm.org/D143327
53 lines
2.0 KiB
C++
53 lines
2.0 KiB
C++
//===----------------------------------------------------------------------===//
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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___UTILITY_IS_POINTER_IN_RANGE_H
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#define _LIBCPP___UTILITY_IS_POINTER_IN_RANGE_H
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#include <__algorithm/comp.h>
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#include <__assert>
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#include <__config>
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#include <__type_traits/enable_if.h>
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#include <__type_traits/integral_constant.h>
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#include <__type_traits/is_constant_evaluated.h>
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#include <__type_traits/is_function.h>
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#include <__type_traits/is_member_pointer.h>
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#include <__type_traits/void_t.h>
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#include <__utility/declval.h>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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template <class _Tp, class _Up>
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_LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI _LIBCPP_NO_SANITIZE("address") bool __is_pointer_in_range(
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const _Tp* __begin, const _Tp* __end, const _Up* __ptr) {
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static_assert(!is_function<_Tp>::value && !is_function<_Up>::value,
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"__is_pointer_in_range should not be called with function pointers");
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static_assert(!is_member_pointer<_Tp>::value && !is_member_pointer<_Up>::value,
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"__is_pointer_in_range should not be called with member pointers");
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if (__libcpp_is_constant_evaluated()) {
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_LIBCPP_ASSERT(__builtin_constant_p(__begin <= __end), "__begin and __end do not form a range");
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// If this is not a constant during constant evaluation we know that __ptr is not part of the allocation where
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// [__begin, __end) is.
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if (!__builtin_constant_p(__begin <= __ptr && __ptr < __end))
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return false;
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}
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// Checking this for unrelated pointers is technically UB, but no compiler optimizes based on it (currently).
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return !__less<>()(__ptr, __begin) && __less<>()(__ptr, __end);
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}
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___UTILITY_IS_POINTER_IN_RANGE_H
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