libcxx/include/__utility/is_pointer_in_range.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef _LIBCPP___UTILITY_IS_POINTER_IN_RANGE_H
  10 #define _LIBCPP___UTILITY_IS_POINTER_IN_RANGE_H
  11
  12 #include <__algorithm/comp.h>
  13 #include <__assert>
  14 #include <__config>
  15 #include <__type_traits/enable_if.h>
  16 #include <__type_traits/integral_constant.h>
  17 #include <__type_traits/is_constant_evaluated.h>
  18 #include <__type_traits/void_t.h>
  19 #include <__utility/declval.h>
  20
  21 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  22 #  pragma GCC system_header
  23 #endif
  24
  25 _LIBCPP_BEGIN_NAMESPACE_STD
  26
  27 template <class _Tp, class _Up, class = void>
  28 struct __is_less_than_comparable : false_type {};
  29
  30 template <class _Tp, class _Up>
  31 struct __is_less_than_comparable<_Tp, _Up, __void_t<decltype(std::declval<_Tp>() < std::declval<_Up>())> > : true_type {
  32 };
  33
  34 template <class _Tp, class _Up, __enable_if_t<__is_less_than_comparable<const _Tp*, const _Up*>::value, int> = 0>
  35 _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI _LIBCPP_NO_SANITIZE("address") bool __is_pointer_in_range(
  36     const _Tp* __begin, const _Tp* __end, const _Up* __ptr) {
  37   if (__libcpp_is_constant_evaluated()) {
  38     _LIBCPP_ASSERT_UNCATEGORIZED(__builtin_constant_p(__begin <= __end), "__begin and __end do not form a range");
  39
  40     // If this is not a constant during constant evaluation we know that __ptr is not part of the allocation where
  41     // [__begin, __end) is.
  42     if (!__builtin_constant_p(__begin <= __ptr && __ptr < __end))
  43       return false;
  44   }
  45
  46   // Checking this for unrelated pointers is technically UB, but no compiler optimizes based on it (currently).
  47   return !__less<>()(__ptr, __begin) && __less<>()(__ptr, __end);
  48 }
  49
  50 template <class _Tp, class _Up, __enable_if_t<!__is_less_than_comparable<const _Tp*, const _Up*>::value, int> = 0>
  51 _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI _LIBCPP_NO_SANITIZE("address") bool __is_pointer_in_range(
  52     const _Tp* __begin, const _Tp* __end, const _Up* __ptr) {
  53   if (__libcpp_is_constant_evaluated())
  54     return false;
  55
  56   return reinterpret_cast<const char*>(__begin) <= reinterpret_cast<const char*>(__ptr) &&
  57          reinterpret_cast<const char*>(__ptr) < reinterpret_cast<const char*>(__end);
  58 }
  59
  60 _LIBCPP_END_NAMESPACE_STD
  61
  62 #endif // _LIBCPP___UTILITY_IS_POINTER_IN_RANGE_H