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___ALGORITHM_COMP_REF_TYPE_H
10 #define _LIBCPP___ALGORITHM_COMP_REF_TYPE_H
11 
12 #include <__assert>
13 #include <__config>
14 #include <__utility/declval.h>
15 
16 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
17 #  pragma GCC system_header
18 #endif
19 
20 _LIBCPP_BEGIN_NAMESPACE_STD
21 
22 template <class _Compare>
23 struct __debug_less {
24   _Compare& __comp_;
25   _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI __debug_less(_Compare& __c) : __comp_(__c) {}
26 
27   template <class _Tp, class _Up>
28   _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI bool operator()(const _Tp& __x, const _Up& __y) {
29     bool __r = __comp_(__x, __y);
30     if (__r)
31       __do_compare_assert(0, __y, __x);
32     return __r;
33   }
34 
35   template <class _Tp, class _Up>
36   _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_HIDE_FROM_ABI bool operator()(_Tp& __x, _Up& __y) {
37     bool __r = __comp_(__x, __y);
38     if (__r)
39       __do_compare_assert(0, __y, __x);
40     return __r;
41   }
42 
43   template <class _LHS, class _RHS>
44   _LIBCPP_CONSTEXPR_SINCE_CXX14 inline _LIBCPP_HIDE_FROM_ABI decltype((void)std::declval<_Compare&>()(
45       std::declval<_LHS&>(), std::declval<_RHS&>()))
46   __do_compare_assert(int, _LHS& __l, _RHS& __r) {
47     _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(!__comp_(__l, __r), "Comparator does not induce a strict weak ordering");
48     (void)__l;
49     (void)__r;
50   }
51 
52   template <class _LHS, class _RHS>
53   _LIBCPP_CONSTEXPR_SINCE_CXX14 inline _LIBCPP_HIDE_FROM_ABI void __do_compare_assert(long, _LHS&, _RHS&) {}
54 };
55 
56 // Pass the comparator by lvalue reference. Or in the debug mode, using a debugging wrapper that stores a reference.
57 #if _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_DEBUG
58 template <class _Comp>
59 using __comp_ref_type = __debug_less<_Comp>;
60 #else
61 template <class _Comp>
62 using __comp_ref_type = _Comp&;
63 #endif
64 
65 _LIBCPP_END_NAMESPACE_STD
66 
67 #endif // _LIBCPP___ALGORITHM_COMP_REF_TYPE_H
68