libcxx/include/__debug_utils/strict_weak_ordering_check.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___LIBCXX_DEBUG_STRICT_WEAK_ORDERING_CHECK
  10 #define _LIBCPP___LIBCXX_DEBUG_STRICT_WEAK_ORDERING_CHECK
  11
  12 #include <__config>
  13
  14 #include <__algorithm/comp_ref_type.h>
  15 #include <__algorithm/is_sorted.h>
  16 #include <__assert>
  17 #include <__iterator/iterator_traits.h>
  18 #include <__type_traits/is_constant_evaluated.h>
  19
  20 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  21 #  pragma GCC system_header
  22 #endif
  23
  24 _LIBCPP_BEGIN_NAMESPACE_STD
  25
  26 template <class _RandomAccessIterator, class _Comp>
  27 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void
  28 __check_strict_weak_ordering_sorted(_RandomAccessIterator __first, _RandomAccessIterator __last, _Comp& __comp) {
  29 #if _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_DEBUG
  30   using __diff_t  = __iter_diff_t<_RandomAccessIterator>;
  31   using _Comp_ref = __comp_ref_type<_Comp>;
  32   if (!__libcpp_is_constant_evaluated()) {
  33     // Check if the range is actually sorted.
  34     _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(
  35         (std::is_sorted<_RandomAccessIterator, _Comp_ref>(__first, __last, _Comp_ref(__comp))),
  36         "The range is not sorted after the sort, your comparator is not a valid strict-weak ordering");
  37     // Limit the number of elements we need to check.
  38     __diff_t __size = __last - __first > __diff_t(100) ? __diff_t(100) : __last - __first;
  39     __diff_t __p    = 0;
  40     while (__p < __size) {
  41       __diff_t __q = __p + __diff_t(1);
  42       // Find first element that is greater than *(__first+__p).
  43       while (__q < __size && !__comp(*(__first + __p), *(__first + __q))) {
  44         ++__q;
  45       }
  46       // Check that the elements from __p to __q are equal between each other.
  47       for (__diff_t __b = __p; __b < __q; ++__b) {
  48         for (__diff_t __a = __p; __a <= __b; ++__a) {
  49           _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(
  50               !__comp(*(__first + __a), *(__first + __b)), "Your comparator is not a valid strict-weak ordering");
  51           _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(
  52               !__comp(*(__first + __b), *(__first + __a)), "Your comparator is not a valid strict-weak ordering");
  53         }
  54       }
  55       // Check that elements between __p and __q are less than between __q and __size.
  56       for (__diff_t __a = __p; __a < __q; ++__a) {
  57         for (__diff_t __b = __q; __b < __size; ++__b) {
  58           _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(
  59               __comp(*(__first + __a), *(__first + __b)), "Your comparator is not a valid strict-weak ordering");
  60           _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(
  61               !__comp(*(__first + __b), *(__first + __a)), "Your comparator is not a valid strict-weak ordering");
  62         }
  63       }
  64       // Skip these equal elements.
  65       __p = __q;
  66     }
  67   }
  68 #else
  69   (void)__first;
  70   (void)__last;
  71   (void)__comp;
  72 #endif // _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_DEBUG
  73 }
  74
  75 _LIBCPP_END_NAMESPACE_STD
  76
  77 #endif // _LIBCPP___LIBCXX_DEBUG_STRICT_WEAK_ORDERING_CHECK