[libc++] Add [[nodiscard]] extensions to ranges algorithms

[philnik]

Summary

This mirrors what we have done in the classic algorithms

[philnik]

List functions in the documentation

[huixie90]

LGTM

libcxx/include/__algorithm/ranges_remove_if.h

68

not an issue, but I think we can make use of the optional nodiscard string literal to suggest the user to use erase-remove (same of erase-unique)

[ldionne]

FWIW I got positive feedback from some folks on our nodiscard extensions. I resisted them for a while but I now definitely think they're an improvement.

libcxx/test/libcxx/diagnostics/ranges.nodiscard.compile.pass.cpp

1

Filename ranges.nodiscard_extensions.compile.pass.cpp maybe? Not as cute but it explains better what it's about.

12–14

I don't think we should try to guard this test against potential future changes in Clang like that. Clang should never implement ranges algorithms as builtins, that sounds like a weird thing to do.

libcxx/test/libcxx/diagnostics/ranges.nodiscard.verify.cpp

9–10

This is an incorrect copy-paste.

12–14

Same comment, let's remove.

[philnik]

• Address comments
• Try to fix CI

[philnik]

libcxx/include/__algorithm/ranges_remove_if.h

68

I'm not sure what you mean exactly. Either way this should probably be it's own PR, in case you feel like it.

libcxx/docs/UsingLibcxx.rst

 * ``mismatch``
 * ``none_of``
 * ``remove_if``
 * ``remove``
 * ``search_n``
 * ``search``
 * ``unique``
 * ``upper_bound``
+* ``ranges::adjacent_find``
+* ``ranges::all_of``
+* ``ranges::any_of``
+* ``ranges::binary_search``
+* ``ranges::clamp``
+* ``ranges::count_if``
+* ``ranges::count``
+* ``ranges::equal_range``
+* ``ranges::equal``
+* ``ranges::find_end``
+* ``ranges::find_first_of``
+* ``ranges::find_if_not``
+* ``ranges::find_if``
+* ``ranges::find``
+* ``ranges::get_temporary_buffer``
+* ``ranges::includes``
+* ``ranges::is_heap_until``
+* ``ranges::is_heap``
+* ``ranges::is_partitioned``
+* ``ranges::is_permutation``
+* ``ranges::is_sorted_until``
+* ``ranges::is_sorted``
+* ``ranges::lexicographical_compare``
+* ``ranges::lower_bound``
+* ``ranges::max_element``
+* ``ranges::max``
+* ``ranges::min_element``
+* ``ranges::min``
+* ``ranges::minmax_element``
+* ``ranges::minmax``
+* ``ranges::mismatch``
+* ``ranges::none_of``
+* ``ranges::remove_if``
+* ``ranges::remove``
+* ``ranges::search_n``
+* ``ranges::search``
+* ``ranges::unique``
+* ``ranges::upper_bound``
 * ``lock_guard``'s constructors
 * ``as_const``
 * ``bit_cast``
 * ``forward``
 * ``move``
 * ``move_if_noexcept``
 * ``identity::operator()``
 * ``to_integer``

libcxx/include/__algorithm/ranges_adjacent_find.h

while (++__i != __last) {
       __first = __i;
     }
     return __i;
   }
 
   template <forward_iterator _Iter, sentinel_for<_Iter> _Sent,
             class _Proj = identity,
             indirect_binary_predicate<projected<_Iter, _Proj>, projected<_Iter, _Proj>> _Pred = ranges::equal_to>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   _Iter operator()(_Iter __first, _Sent __last, _Pred __pred = {}, _Proj __proj = {}) const {
     return __adjacent_find_impl(std::move(__first), std::move(__last), __pred, __proj);
   }
 
   template <forward_range _Range,
             class _Proj = identity,
             indirect_binary_predicate<projected<iterator_t<_Range>, _Proj>,
                                       projected<iterator_t<_Range>, _Proj>> _Pred = ranges::equal_to>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_iterator_t<_Range> operator()(_Range&& __range, _Pred __pred = {}, _Proj __proj = {}) const {
     return __adjacent_find_impl(ranges::begin(__range), ranges::end(__range), __pred, __proj);
   }
 };
 } // namespace __adjacent_find
 
 inline namespace __cpo {
   inline constexpr auto adjacent_find = __adjacent_find::__fn{};
 } // namespace __cpo
 } // namespace ranges
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER > 17
 
 #endif // _LIBCPP___ALGORITHM_RANGES_ADJACENT_FIND_H

libcxx/include/__algorithm/ranges_all_of.h

for (; __first != __last; ++__first) {
       if (!std::invoke(__pred, std::invoke(__proj, *__first)))
         return false;
     }
     return true;
   }
 
   template <input_iterator _Iter, sentinel_for<_Iter> _Sent, class _Proj = identity,
             indirect_unary_predicate<projected<_Iter, _Proj>> _Pred>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Iter __first, _Sent __last, _Pred __pred, _Proj __proj = {}) const {
     return __all_of_impl(std::move(__first), std::move(__last), __pred, __proj);
   }
 
   template <input_range _Range, class _Proj = identity,
             indirect_unary_predicate<projected<iterator_t<_Range>, _Proj>> _Pred>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Range&& __range, _Pred __pred, _Proj __proj = {}) const {
     return __all_of_impl(ranges::begin(__range), ranges::end(__range), __pred, __proj);
   }
 };
 } // namespace __all_of
 
 inline namespace __cpo {
   inline constexpr auto all_of = __all_of::__fn{};
 } // namespace __cpo
 } // namespace ranges
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER > 17
 
 #endif // _LIBCPP___ALGORITHM_RANGES_ALL_OF_H

libcxx/include/__algorithm/ranges_any_of.h

for (; __first != __last; ++__first) {
       if (std::invoke(__pred, std::invoke(__proj, *__first)))
         return true;
     }
     return false;
   }
 
   template <input_iterator _Iter, sentinel_for<_Iter> _Sent, class _Proj = identity,
             indirect_unary_predicate<projected<_Iter, _Proj>> _Pred>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Iter __first, _Sent __last, _Pred __pred = {}, _Proj __proj = {}) const {
     return __any_of_impl(std::move(__first), std::move(__last), __pred, __proj);
   }
 
   template <input_range _Range, class _Proj = identity,
             indirect_unary_predicate<projected<iterator_t<_Range>, _Proj>> _Pred>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Range&& __range, _Pred __pred, _Proj __proj = {}) const {
     return __any_of_impl(ranges::begin(__range), ranges::end(__range), __pred, __proj);
   }
 };
 } // namespace __any_of
 
 inline namespace __cpo {
   inline constexpr auto any_of = __any_of::__fn{};
 } // namespace __cpo
 } // namespace ranges
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER > 17
 
 #endif // _LIBCPP___ALGORITHM_RANGES_ANY_OF_H

libcxx/include/__algorithm/ranges_binary_search.h

 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace ranges {
 namespace __binary_search {
 struct __fn {
   template <forward_iterator _Iter, sentinel_for<_Iter> _Sent, class _Type, class _Proj = identity,
             indirect_strict_weak_order<const _Type*, projected<_Iter, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Iter __first, _Sent __last, const _Type& __value, _Comp __comp = {}, _Proj __proj = {}) const {
     auto __ret = std::__lower_bound_impl<_RangeAlgPolicy>(__first, __last, __value, __comp, __proj);
     return __ret != __last && !std::invoke(__comp, __value, std::invoke(__proj, *__first));
   }
 
   template <forward_range _Range, class _Type, class _Proj = identity,
             indirect_strict_weak_order<const _Type*, projected<iterator_t<_Range>, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Range&& __r, const _Type& __value, _Comp __comp = {}, _Proj __proj = {}) const {
     auto __first = ranges::begin(__r);
     auto __last = ranges::end(__r);
     auto __ret = std::__lower_bound_impl<_RangeAlgPolicy>(__first, __last, __value, __comp, __proj);
     return __ret != __last && !std::invoke(__comp, __value, std::invoke(__proj, *__first));
   }
 };
 } // namespace __binary_search

libcxx/include/__algorithm/ranges_clamp.h

 
 namespace ranges {
 namespace __clamp {
 struct __fn {
 
   template <class _Type,
             class _Proj = identity,
             indirect_strict_weak_order<projected<const _Type*, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   const _Type& operator()(const _Type& __value,
                           const _Type& __low,
                           const _Type& __high,
                           _Comp __comp = {},
                           _Proj __proj = {}) const {
     _LIBCPP_ASSERT(!bool(std::invoke(__comp, std::invoke(__proj, __high), std::invoke(__proj, __low))),
                    "Bad bounds passed to std::ranges::clamp");
 

libcxx/include/__algorithm/ranges_count.h

 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace ranges {
 namespace __count {
 struct __fn {
   template <input_iterator _Iter, sentinel_for<_Iter> _Sent, class _Type, class _Proj = identity>
     requires indirect_binary_predicate<ranges::equal_to, projected<_Iter, _Proj>, const _Type*>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   iter_difference_t<_Iter> operator()(_Iter __first, _Sent __last, const _Type& __value, _Proj __proj = {}) const {
     auto __pred = [&](auto&& __e) { return __e == __value; };
     return ranges::__count_if_impl(std::move(__first), std::move(__last), __pred, __proj);
   }
 
   template <input_range _Range, class _Type, class _Proj = identity>
     requires indirect_binary_predicate<ranges::equal_to, projected<iterator_t<_Range>, _Proj>, const _Type*>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   range_difference_t<_Range> operator()(_Range&& __r, const _Type& __value, _Proj __proj = {}) const {
     auto __pred = [&](auto&& __e) { return __e == __value; };
     return ranges::__count_if_impl(ranges::begin(__r), ranges::end(__r), __pred, __proj);
   }
 };
 } // namespace __count
 
 inline namespace __cpo {

libcxx/include/__algorithm/ranges_count_if.h

iter_difference_t<_Iter> __count_if_impl(_Iter __first, _Sent __last,
   }
   return __counter;
 }
 
 namespace __count_if {
 struct __fn {
   template <input_iterator _Iter, sentinel_for<_Iter> _Sent, class _Proj = identity,
             indirect_unary_predicate<projected<_Iter, _Proj>> _Predicate>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   iter_difference_t<_Iter> operator()(_Iter __first, _Sent __last, _Predicate __pred, _Proj __proj = {}) const {
     return ranges::__count_if_impl(std::move(__first), std::move(__last), __pred, __proj);
   }
 
   template <input_range _Range, class _Proj = identity,
             indirect_unary_predicate<projected<iterator_t<_Range>, _Proj>> _Predicate>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   range_difference_t<_Range> operator()(_Range&& __r, _Predicate __pred, _Proj __proj = {}) const {
     return ranges::__count_if_impl(ranges::begin(__r), ranges::end(__r), __pred, __proj);
   }
 };
 } // namespace __count_if
 
 inline namespace __cpo {
   inline constexpr auto count_if = __count_if::__fn{};
 } // namespace __cpo
 } // namespace ranges
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER > 17
 
 #endif // _LIBCPP___ALGORITHM_RANGES_COUNT_IF_H

libcxx/include/__algorithm/ranges_equal.h

 public:
 
   template <input_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
             input_iterator _Iter2, sentinel_for<_Iter2> _Sent2,
             class _Pred = ranges::equal_to,
             class _Proj1 = identity,
             class _Proj2 = identity>
     requires indirectly_comparable<_Iter1, _Iter2, _Pred, _Proj1, _Proj2>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Iter1 __first1, _Sent1 __last1,
                   _Iter2 __first2, _Sent2 __last2,
                   _Pred __pred = {},
                   _Proj1 __proj1 = {},
                   _Proj2 __proj2 = {}) const {
     if constexpr (sized_sentinel_for<_Sent1, _Iter1> && sized_sentinel_for<_Sent2, _Iter2>) {
       if (__last1 - __first1 != __last2 - __first2)
         return false;
     }
     return __equal_impl(std::move(__first1), std::move(__last1),
                         std::move(__first2), std::move(__last2),
                         __pred,
                         __proj1,
                         __proj2);
   }
 
   template <input_range _Range1,
             input_range _Range2,
             class _Pred = ranges::equal_to,
             class _Proj1 = identity,
             class _Proj2 = identity>
     requires indirectly_comparable<iterator_t<_Range1>, iterator_t<_Range2>, _Pred, _Proj1, _Proj2>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Range1&& __range1,
                   _Range2&& __range2,
                   _Pred __pred = {},
                   _Proj1 __proj1 = {},
                   _Proj2 __proj2 = {}) const {
     if constexpr (sized_range<_Range1> && sized_range<_Range2>) {
       if (ranges::distance(__range1) != ranges::distance(__range2))
         return false;

libcxx/include/__algorithm/ranges_equal_range.h

 
 struct __fn {
   template <
       forward_iterator _Iter,
       sentinel_for<_Iter> _Sent,
       class _Tp,
       class _Proj                                                           = identity,
       indirect_strict_weak_order<const _Tp*, projected<_Iter, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr subrange<_Iter>
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr subrange<_Iter>
   operator()(_Iter __first, _Sent __last, const _Tp& __value, _Comp __comp = {}, _Proj __proj = {}) const {
     auto __ret = std::__equal_range<_RangeAlgPolicy>(
         std::move(__first), std::move(__last), __value, __comp, __proj);
     return {std::move(__ret.first), std::move(__ret.second)};
   }
 
   template <
       forward_range _Range,
       class _Tp,
       class _Proj                                                                        = identity,
       indirect_strict_weak_order<const _Tp*, projected<iterator_t<_Range>, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr borrowed_subrange_t<_Range>
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr borrowed_subrange_t<_Range>
   operator()(_Range&& __range, const _Tp& __value, _Comp __comp = {}, _Proj __proj = {}) const {
     auto __ret = std::__equal_range<_RangeAlgPolicy>(
         ranges::begin(__range), ranges::end(__range), __value, __comp, __proj);
     return {std::move(__ret.first), std::move(__ret.second)};
   }
 };
 
 } // namespace __equal_range

libcxx/include/__algorithm/ranges_find.h

 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace ranges {
 namespace __find {
 struct __fn {
   template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Tp, class _Proj = identity>
     requires indirect_binary_predicate<ranges::equal_to, projected<_Ip, _Proj>, const _Tp*>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   _Ip operator()(_Ip __first, _Sp __last, const _Tp& __value, _Proj __proj = {}) const {
     auto __pred = [&](auto&& __e) { return std::forward<decltype(__e)>(__e) == __value; };
     return ranges::__find_if_impl(std::move(__first), std::move(__last), __pred, __proj);
   }
 
   template <input_range _Rp, class _Tp, class _Proj = identity>
     requires indirect_binary_predicate<ranges::equal_to, projected<iterator_t<_Rp>, _Proj>, const _Tp*>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_iterator_t<_Rp> operator()(_Rp&& __r, const _Tp& __value, _Proj __proj = {}) const {
     auto __pred = [&](auto&& __e) { return std::forward<decltype(__e)>(__e) == __value; };
     return ranges::__find_if_impl(ranges::begin(__r), ranges::end(__r), __pred, __proj);
   }
 };
 } // namespace __find
 
 inline namespace __cpo {

libcxx/include/__algorithm/ranges_find_end.h

 namespace __find_end {
 struct __fn {
   template <forward_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
             forward_iterator _Iter2, sentinel_for<_Iter2> _Sent2,
             class _Pred = ranges::equal_to,
             class _Proj1 = identity,
             class _Proj2 = identity>
     requires indirectly_comparable<_Iter1, _Iter2, _Pred, _Proj1, _Proj2>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   subrange<_Iter1> operator()(_Iter1 __first1, _Sent1 __last1,
                               _Iter2 __first2, _Sent2 __last2,
                               _Pred __pred = {},
                               _Proj1 __proj1 = {},
                               _Proj2 __proj2 = {}) const {
     auto __ret = std::__find_end_impl<_RangeAlgPolicy>(
         __first1,
         __last1,
         __first2,
         __last2,
         __pred,
         __proj1,
         __proj2,
         __iterator_concept<_Iter1>(),
         __iterator_concept<_Iter2>());
     return {__ret.first, __ret.second};
   }
 
   template <forward_range _Range1,
             forward_range _Range2,
             class _Pred = ranges::equal_to,
             class _Proj1 = identity,
             class _Proj2 = identity>
     requires indirectly_comparable<iterator_t<_Range1>, iterator_t<_Range2>, _Pred, _Proj1, _Proj2>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_subrange_t<_Range1> operator()(_Range1&& __range1,
                                           _Range2&& __range2,
                                           _Pred __pred = {},
                                           _Proj1 __proj1 = {},
                                           _Proj2 __proj2 = {}) const {
     auto __ret = std::__find_end_impl<_RangeAlgPolicy>(
         ranges::begin(__range1),
         ranges::end(__range1),

libcxx/include/__algorithm/ranges_find_first_of.h

struct __fn {
   }
 
   template <input_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
             forward_iterator _Iter2, sentinel_for<_Iter2> _Sent2,
             class _Pred = ranges::equal_to,
             class _Proj1 = identity,
             class _Proj2 = identity>
     requires indirectly_comparable<_Iter1, _Iter2, _Pred, _Proj1, _Proj2>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   _Iter1 operator()(_Iter1 __first1, _Sent1 __last1,
                     _Iter2 __first2, _Sent2 __last2,
                     _Pred __pred = {},
                     _Proj1 __proj1 = {},
                     _Proj2 __proj2 = {}) const {
     return __find_first_of_impl(std::move(__first1), std::move(__last1),
                                 std::move(__first2), std::move(__last2),
                                 __pred,
                                 __proj1,
                                 __proj2);
   }
 
   template <input_range _Range1,
             forward_range _Range2,
             class _Pred = ranges::equal_to,
             class _Proj1 = identity,
             class _Proj2 = identity>
     requires indirectly_comparable<iterator_t<_Range1>, iterator_t<_Range2>, _Pred, _Proj1, _Proj2>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_iterator_t<_Range1> operator()(_Range1&& __range1,
                                           _Range2&& __range2,
                                           _Pred __pred = {},
                                           _Proj1 __proj1 = {},
                                           _Proj2 __proj2 = {}) const {
     return __find_first_of_impl(ranges::begin(__range1), ranges::end(__range1),
                                 ranges::begin(__range2), ranges::end(__range2),
                                 __pred,

libcxx/include/__algorithm/ranges_find_if.h

_Ip __find_if_impl(_Ip __first, _Sp __last, _Pred& __pred, _Proj& __proj) {
   return __first;
 }
 
 namespace __find_if {
 struct __fn {
 
   template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Proj = identity,
             indirect_unary_predicate<projected<_Ip, _Proj>> _Pred>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   _Ip operator()(_Ip __first, _Sp __last, _Pred __pred, _Proj __proj = {}) const {
     return ranges::__find_if_impl(std::move(__first), std::move(__last), __pred, __proj);
   }
 
   template <input_range _Rp, class _Proj = identity,
             indirect_unary_predicate<projected<iterator_t<_Rp>, _Proj>> _Pred>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_iterator_t<_Rp> operator()(_Rp&& __r, _Pred __pred, _Proj __proj = {}) const {
     return ranges::__find_if_impl(ranges::begin(__r), ranges::end(__r), __pred, __proj);
   }
 };
 } // namespace __find_if
 
 inline namespace __cpo {
   inline constexpr auto find_if = __find_if::__fn{};
 } // namespace __cpo
 } // namespace ranges
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER > 17
 
 #endif // _LIBCPP___ALGORITHM_RANGES_FIND_IF_H

libcxx/include/__algorithm/ranges_find_if_not.h

 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace ranges {
 namespace __find_if_not {
 struct __fn {
   template <input_iterator _Ip, sentinel_for<_Ip> _Sp, class _Proj = identity,
             indirect_unary_predicate<projected<_Ip, _Proj>> _Pred>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   _Ip operator()(_Ip __first, _Sp __last, _Pred __pred, _Proj __proj = {}) const {
     auto __pred2 = [&](auto&& __e) { return !std::invoke(__pred, std::forward<decltype(__e)>(__e)); };
     return ranges::__find_if_impl(std::move(__first), std::move(__last), __pred2, __proj);
   }
 
   template <input_range _Rp, class _Proj = identity,
             indirect_unary_predicate<projected<iterator_t<_Rp>, _Proj>> _Pred>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_iterator_t<_Rp> operator()(_Rp&& __r, _Pred __pred, _Proj __proj = {}) const {
     auto __pred2 = [&](auto&& __e) { return !std::invoke(__pred, std::forward<decltype(__e)>(__e)); };
     return ranges::__find_if_impl(ranges::begin(__r), ranges::end(__r), __pred2, __proj);
   }
 };
 } // namespace __find_if_not
 
 inline namespace __cpo {

libcxx/include/__algorithm/ranges_includes.h

struct __fn {
   template <
       input_iterator _Iter1,
       sentinel_for<_Iter1> _Sent1,
       input_iterator _Iter2,
       sentinel_for<_Iter2> _Sent2,
       class _Proj1                                                                           = identity,
       class _Proj2                                                                           = identity,
       indirect_strict_weak_order<projected<_Iter1, _Proj1>, projected<_Iter2, _Proj2>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr bool operator()(
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr bool operator()(
       _Iter1 __first1,
       _Sent1 __last1,
       _Iter2 __first2,
       _Sent2 __last2,
       _Comp __comp   = {},
       _Proj1 __proj1 = {},
       _Proj2 __proj2 = {}) const {
     return std::__includes(
         std::move(__first1),
         std::move(__last1),
         std::move(__first2),
         std::move(__last2),
         std::move(__comp),
         std::move(__proj1),
         std::move(__proj2));
   }
 
   template <
       input_range _Range1,
       input_range _Range2,
       class _Proj1 = identity,
       class _Proj2 = identity,
       indirect_strict_weak_order<projected<iterator_t<_Range1>, _Proj1>, projected<iterator_t<_Range2>, _Proj2>>
           _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr bool operator()(
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr bool operator()(
       _Range1&& __range1, _Range2&& __range2, _Comp __comp = {}, _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const {
     return std::__includes(
         ranges::begin(__range1),
         ranges::end(__range1),
         ranges::begin(__range2),
         ranges::end(__range2),
         std::move(__comp),
         std::move(__proj1),

libcxx/include/__algorithm/ranges_is_heap.h

static bool __is_heap_fn_impl(_Iter __first, _Sent __last, _Comp& __comp, _Proj& __proj) {
     auto&& __projected_comp = std::__make_projected(__comp, __proj);
 
     auto __result = std::__is_heap_until(std::move(__first), std::move(__last_iter), __projected_comp);
     return __result == __last;
   }
 
   template <random_access_iterator _Iter, sentinel_for<_Iter> _Sent, class _Proj = identity,
             indirect_strict_weak_order<projected<_Iter, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Iter __first, _Sent __last, _Comp __comp = {}, _Proj __proj = {}) const {
     return __is_heap_fn_impl(std::move(__first), std::move(__last), __comp, __proj);
   }
 
   template <random_access_range _Range, class _Proj = identity,
             indirect_strict_weak_order<projected<iterator_t<_Range>, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Range&& __range, _Comp __comp = {}, _Proj __proj = {}) const {
     return __is_heap_fn_impl(ranges::begin(__range), ranges::end(__range), __comp, __proj);
   }
 };
 
 } // namespace __is_heap
 
 inline namespace __cpo {

libcxx/include/__algorithm/ranges_is_heap_until.h

static _Iter __is_heap_until_fn_impl(_Iter __first, _Sent __last, _Comp& __comp, _Proj& __proj) {
     auto __last_iter = ranges::next(__first, __last);
     auto&& __projected_comp = std::__make_projected(__comp, __proj);
 
     return std::__is_heap_until(std::move(__first), std::move(__last_iter), __projected_comp);
   }
 
   template <random_access_iterator _Iter, sentinel_for<_Iter> _Sent, class _Proj = identity,
             indirect_strict_weak_order<projected<_Iter, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   _Iter operator()(_Iter __first, _Sent __last, _Comp __comp = {}, _Proj __proj = {}) const {
     return __is_heap_until_fn_impl(std::move(__first), std::move(__last), __comp, __proj);
   }
 
   template <random_access_range _Range, class _Proj = identity,
             indirect_strict_weak_order<projected<iterator_t<_Range>, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_iterator_t<_Range> operator()(_Range&& __range, _Comp __comp = {}, _Proj __proj = {}) const {
     return __is_heap_until_fn_impl(ranges::begin(__range), ranges::end(__range), __comp, __proj);
   }
 
 };
 
 } // namespace __is_heap_until
 

libcxx/include/__algorithm/ranges_is_partitioned.h

bool __is_parititioned_impl(_Iter __first, _Sent __last, _Pred& __pred, _Proj& __proj) {
     }
 
     return true;
   }
 
   template <input_iterator _Iter, sentinel_for<_Iter> _Sent,
             class _Proj = identity,
             indirect_unary_predicate<projected<_Iter, _Proj>> _Pred>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Iter __first, _Sent __last, _Pred __pred, _Proj __proj = {}) const {
     return __is_parititioned_impl(std::move(__first), std::move(__last), __pred, __proj);
   }
 
   template <input_range _Range,
             class _Proj = identity,
             indirect_unary_predicate<projected<iterator_t<_Range>, _Proj>> _Pred>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Range&& __range, _Pred __pred, _Proj __proj = {}) const {
     return __is_parititioned_impl(ranges::begin(__range), ranges::end(__range), __pred, __proj);
   }
 };
 } // namespace __is_partitioned
 
 inline namespace __cpo {
   inline constexpr auto is_partitioned = __is_partitioned::__fn{};
 } // namespace __cpo
 } // namespace ranges
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER > 17
 
 #endif // _LIBCPP___ALGORITHM_RANGES_IS_PARTITIONED_H

libcxx/include/__algorithm/ranges_is_permutation.h

struct __fn {
   }
 
   template <forward_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
             forward_iterator _Iter2, sentinel_for<_Iter2> _Sent2,
             class _Proj1 = identity,
             class _Proj2 = identity,
             indirect_equivalence_relation<projected<_Iter1, _Proj1>,
                                           projected<_Iter2, _Proj2>> _Pred = ranges::equal_to>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2 __last2,
                   _Pred __pred = {}, _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const {
     return __is_permutation_func_impl(
         std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2),
         __pred, __proj1, __proj2);
   }
 
   template <forward_range _Range1,
             forward_range _Range2,
             class _Proj1 = identity,
             class _Proj2 = identity,
             indirect_equivalence_relation<projected<iterator_t<_Range1>, _Proj1>, projected<iterator_t<_Range2>, _Proj2>> _Pred = ranges::equal_to>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Range1&& __range1, _Range2&& __range2,
                   _Pred __pred = {}, _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const {
     if constexpr (sized_range<_Range1> && sized_range<_Range2>) {
       if (ranges::distance(__range1) != ranges::distance(__range2))
         return false;
     }
 
     return __is_permutation_func_impl(

libcxx/include/__algorithm/ranges_is_sorted.h

 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace ranges {
 namespace __is_sorted {
 struct __fn {
   template <forward_iterator _Iter, sentinel_for<_Iter> _Sent,
             class _Proj = identity,
             indirect_strict_weak_order<projected<_Iter, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Iter __first, _Sent __last, _Comp __comp = {}, _Proj __proj = {}) const {
     return ranges::__is_sorted_until_impl(std::move(__first), __last, __comp, __proj) == __last;
   }
 
   template <forward_range _Range,
             class _Proj = identity,
             indirect_strict_weak_order<projected<iterator_t<_Range>, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Range&& __range, _Comp __comp = {}, _Proj __proj = {}) const {
     auto __last = ranges::end(__range);
     return ranges::__is_sorted_until_impl(ranges::begin(__range), __last, __comp, __proj) == __last;
   }
 };
 } // namespace __is_sorted
 
 inline namespace __cpo {

libcxx/include/__algorithm/ranges_is_sorted_until.h

_Iter __is_sorted_until_impl(_Iter __first, _Sent __last, _Comp& __comp, _Proj& __proj) {
   return __i;
 }
 
 namespace __is_sorted_until {
 struct __fn {
   template <forward_iterator _Iter, sentinel_for<_Iter> _Sent,
             class _Proj = identity,
             indirect_strict_weak_order<projected<_Iter, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   _Iter operator()(_Iter __first, _Sent __last, _Comp __comp = {}, _Proj __proj = {}) const {
     return ranges::__is_sorted_until_impl(std::move(__first), std::move(__last), __comp, __proj);
   }
 
   template <forward_range _Range,
             class _Proj = identity,
             indirect_strict_weak_order<projected<iterator_t<_Range>, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_iterator_t<_Range> operator()(_Range&& __range, _Comp __comp = {}, _Proj __proj = {}) const {
     return ranges::__is_sorted_until_impl(ranges::begin(__range), ranges::end(__range), __comp, __proj);
   }
 };
 } // namespace __is_sorted_until
 
 inline namespace __cpo {
   inline constexpr auto is_sorted_until = __is_sorted_until::__fn{};
 } // namespace __cpo
 } // namespace ranges
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER > 17
 
 #endif // _LIBCPP__ALGORITHM_RANGES_IS_SORTED_UNTIL_H

libcxx/include/__algorithm/ranges_lexicographical_compare.h

bool __lexicographical_compare_impl(_Iter1 __first1, _Sent1 __last1,
     return false;
   }
 
   template <input_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
             input_iterator _Iter2, sentinel_for<_Iter2> _Sent2,
             class _Proj1 = identity,
             class _Proj2 = identity,
             indirect_strict_weak_order<projected<_Iter1, _Proj1>, projected<_Iter2, _Proj2>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Iter1 __first1, _Sent1 __last1,
                   _Iter2 __first2, _Sent2 __last2,
                   _Comp __comp = {},
                   _Proj1 __proj1 = {},
                   _Proj2 __proj2 = {}) const {
     return __lexicographical_compare_impl(std::move(__first1), std::move(__last1),
                                           std::move(__first2), std::move(__last2),
                                           __comp,
                                           __proj1,
                                           __proj2);
   }
 
   template <input_range _Range1,
             input_range _Range2,
             class _Proj1 = identity,
             class _Proj2 = identity,
             indirect_strict_weak_order<projected<iterator_t<_Range1>, _Proj1>,
                                        projected<iterator_t<_Range2>, _Proj2>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Range1&& __range1, _Range2&& __range2, _Comp __comp = {}, _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const {
     return __lexicographical_compare_impl(ranges::begin(__range1), ranges::end(__range1),
                                           ranges::begin(__range2), ranges::end(__range2),
                                           __comp,
                                           __proj1,
                                           __proj2);
   }
 

libcxx/include/__algorithm/ranges_lower_bound.h

 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace ranges {
 
 namespace __lower_bound {
 struct __fn {
   template <forward_iterator _Iter, sentinel_for<_Iter> _Sent, class _Type, class _Proj = identity,
             indirect_strict_weak_order<const _Type*, projected<_Iter, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   _Iter operator()(_Iter __first, _Sent __last, const _Type& __value, _Comp __comp = {}, _Proj __proj = {}) const {
     return std::__lower_bound_impl<_RangeAlgPolicy>(__first, __last, __value, __comp, __proj);
   }
 
   template <forward_range _Range, class _Type, class _Proj = identity,
             indirect_strict_weak_order<const _Type*, projected<iterator_t<_Range>, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_iterator_t<_Range> operator()(_Range&& __r,
                                          const _Type& __value,
                                          _Comp __comp = {},
                                          _Proj __proj = {}) const {
     return std::__lower_bound_impl<_RangeAlgPolicy>(ranges::begin(__r), ranges::end(__r), __value, __comp, __proj);
   }
 };
 } // namespace __lower_bound

libcxx/include/__algorithm/ranges_max.h

 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace ranges {
 namespace __max {
 struct __fn {
   template <class _Tp, class _Proj = identity,
             indirect_strict_weak_order<projected<const _Tp*, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   const _Tp& operator()(const _Tp& __a, const _Tp& __b, _Comp __comp = {}, _Proj __proj = {}) const {
     return std::invoke(__comp, std::invoke(__proj, __a), std::invoke(__proj, __b)) ? __b : __a;
   }
 
   template <copyable _Tp, class _Proj = identity,
             indirect_strict_weak_order<projected<const _Tp*, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   _Tp operator()(initializer_list<_Tp> __il, _Comp __comp = {}, _Proj __proj = {}) const {
     _LIBCPP_ASSERT(__il.begin() != __il.end(), "initializer_list must contain at least one element");
 
     auto __comp_lhs_rhs_swapped = [&](auto&& __lhs, auto&& __rhs) { return std::invoke(__comp, __rhs, __lhs); };
     return *ranges::__min_element_impl(__il.begin(), __il.end(), __comp_lhs_rhs_swapped, __proj);
   }
 
   template <input_range _Rp, class _Proj = identity,
             indirect_strict_weak_order<projected<iterator_t<_Rp>, _Proj>> _Comp = ranges::less>
     requires indirectly_copyable_storable<iterator_t<_Rp>, range_value_t<_Rp>*>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   range_value_t<_Rp> operator()(_Rp&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
     auto __first = ranges::begin(__r);
     auto __last = ranges::end(__r);
 
     _LIBCPP_ASSERT(__first != __last, "range must contain at least one element");
 
     if constexpr (forward_range<_Rp>) {
       auto __comp_lhs_rhs_swapped = [&](auto&& __lhs, auto&& __rhs) { return std::invoke(__comp, __rhs, __lhs); };

libcxx/include/__algorithm/ranges_max_element.h

 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace ranges {
 namespace __max_element {
 struct __fn {
   template <forward_iterator _Ip, sentinel_for<_Ip> _Sp, class _Proj = identity,
             indirect_strict_weak_order<projected<_Ip, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   _Ip operator()(_Ip __first, _Sp __last, _Comp __comp = {}, _Proj __proj = {}) const {
     auto __comp_lhs_rhs_swapped = [&](auto&& __lhs, auto&& __rhs) { return std::invoke(__comp, __rhs, __lhs); };
     return ranges::__min_element_impl(__first, __last, __comp_lhs_rhs_swapped, __proj);
   }
 
   template <forward_range _Rp, class _Proj = identity,
             indirect_strict_weak_order<projected<iterator_t<_Rp>, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_iterator_t<_Rp> operator()(_Rp&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
     auto __comp_lhs_rhs_swapped = [&](auto&& __lhs, auto&& __rhs) { return std::invoke(__comp, __rhs, __lhs); };
     return ranges::__min_element_impl(ranges::begin(__r), ranges::end(__r), __comp_lhs_rhs_swapped, __proj);
   }
 };
 } // namespace __max_element
 
 inline namespace __cpo {

libcxx/include/__algorithm/ranges_min.h

 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace ranges {
 namespace __min {
 struct __fn {
   template <class _Tp, class _Proj = identity,
             indirect_strict_weak_order<projected<const _Tp*, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   const _Tp& operator()(const _Tp& __a, const _Tp& __b, _Comp __comp = {}, _Proj __proj = {}) const {
     return std::invoke(__comp, std::invoke(__proj, __b), std::invoke(__proj, __a)) ? __b : __a;
   }
 
   template <copyable _Tp, class _Proj = identity,
             indirect_strict_weak_order<projected<const _Tp*, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   _Tp operator()(initializer_list<_Tp> __il, _Comp __comp = {}, _Proj __proj = {}) const {
     _LIBCPP_ASSERT(__il.begin() != __il.end(), "initializer_list must contain at least one element");
     return *ranges::__min_element_impl(__il.begin(), __il.end(), __comp, __proj);
   }
 
   template <input_range _Rp, class _Proj = identity,
             indirect_strict_weak_order<projected<iterator_t<_Rp>, _Proj>> _Comp = ranges::less>
     requires indirectly_copyable_storable<iterator_t<_Rp>, range_value_t<_Rp>*>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   range_value_t<_Rp> operator()(_Rp&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
     auto __first = ranges::begin(__r);
     auto __last = ranges::end(__r);
 
     _LIBCPP_ASSERT(__first != __last, "range must contain at least one element");
 
     if constexpr (forward_range<_Rp>) {
       return *ranges::__min_element_impl(__first, __last, __comp, __proj);

libcxx/include/__algorithm/ranges_min_element.h

if (std::invoke(__comp, std::invoke(__proj, *__i), std::invoke(__proj, *__first)))
       __first = __i;
   return __first;
 }
 
 namespace __min_element {
 struct __fn {
   template <forward_iterator _Ip, sentinel_for<_Ip> _Sp, class _Proj = identity,
             indirect_strict_weak_order<projected<_Ip, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   _Ip operator()(_Ip __first, _Sp __last, _Comp __comp = {}, _Proj __proj = {}) const {
     return ranges::__min_element_impl(__first, __last, __comp, __proj);
   }
 
   template <forward_range _Rp, class _Proj = identity,
             indirect_strict_weak_order<projected<iterator_t<_Rp>, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_iterator_t<_Rp> operator()(_Rp&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
     return ranges::__min_element_impl(ranges::begin(__r), ranges::end(__r), __comp, __proj);
   }
 };
 } // namespace __min_element
 
 inline namespace __cpo {
   inline constexpr auto min_element = __min_element::__fn{};
 } // namespace __cpo
 } // namespace ranges
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER > 17
 
 #endif // _LIBCPP___ALGORITHM_RANGES_MIN_ELEMENT_H

libcxx/include/__algorithm/ranges_minmax.h

 namespace ranges {
 template <class _T1>
 using minmax_result = min_max_result<_T1>;
 
 namespace __minmax {
 struct __fn {
   template <class _Type, class _Proj = identity,
             indirect_strict_weak_order<projected<const _Type*, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr ranges::minmax_result<const _Type&>
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr ranges::minmax_result<const _Type&>
   operator()(const _Type& __a, const _Type& __b, _Comp __comp = {}, _Proj __proj = {}) const {
     if (std::invoke(__comp, std::invoke(__proj, __b), std::invoke(__proj, __a)))
       return {__b, __a};
     return {__a, __b};
   }
 
   template <copyable _Type, class _Proj = identity,
             indirect_strict_weak_order<projected<const _Type*, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   ranges::minmax_result<_Type> operator()(initializer_list<_Type> __il, _Comp __comp = {}, _Proj __proj = {}) const {
     _LIBCPP_ASSERT(__il.begin() != __il.end(), "initializer_list has to contain at least one element");
     auto __iters = std::__minmax_element_impl(__il.begin(), __il.end(), __comp, __proj);
     return ranges::minmax_result<_Type> { *__iters.first, *__iters.second };
   }
 
   template <input_range _Range, class _Proj = identity,
             indirect_strict_weak_order<projected<iterator_t<_Range>, _Proj>> _Comp = ranges::less>
     requires indirectly_copyable_storable<iterator_t<_Range>, range_value_t<_Range>*>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   ranges::minmax_result<range_value_t<_Range>> operator()(_Range&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
     auto __first = ranges::begin(__r);
     auto __last = ranges::end(__r);
     using _ValueT = range_value_t<_Range>;
 
     _LIBCPP_ASSERT(__first != __last, "range has to contain at least one element");
 
     if constexpr (forward_range<_Range>) {

libcxx/include/__algorithm/ranges_minmax_element.h

 
 template <class _T1>
 using minmax_element_result = min_max_result<_T1>;
 
 namespace __minmax_element {
 struct __fn {
   template <forward_iterator _Ip, sentinel_for<_Ip> _Sp, class _Proj = identity,
             indirect_strict_weak_order<projected<_Ip, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   ranges::minmax_element_result<_Ip> operator()(_Ip __first, _Sp __last, _Comp __comp = {}, _Proj __proj = {}) const {
     auto __ret = std::__minmax_element_impl(std::move(__first), std::move(__last), __comp, __proj);
     return {__ret.first, __ret.second};
   }
 
   template <forward_range _Rp, class _Proj = identity,
             indirect_strict_weak_order<projected<iterator_t<_Rp>, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   ranges::minmax_element_result<borrowed_iterator_t<_Rp>>
   operator()(_Rp&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
     auto __ret = std::__minmax_element_impl(ranges::begin(__r), ranges::end(__r), __comp, __proj);
     return {__ret.first, __ret.second};
   }
 };
 } // namespace __minmax_element
 

libcxx/include/__algorithm/ranges_mismatch.h

__go(_I1 __first1, _S1 __last1, _I2 __first2, _S2 __last2,
     }
     return {std::move(__first1), std::move(__first2)};
   }
 
   template <input_iterator _I1, sentinel_for<_I1> _S1,
             input_iterator _I2, sentinel_for<_I2> _S2,
             class _Pred = ranges::equal_to, class _Proj1 = identity, class _Proj2 = identity>
     requires indirectly_comparable<_I1, _I2, _Pred, _Proj1, _Proj2>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   mismatch_result<_I1, _I2> operator()(_I1 __first1, _S1 __last1, _I2 __first2, _S2 __last2,
                                        _Pred __pred = {}, _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const {
     return __go(std::move(__first1), __last1, std::move(__first2), __last2, __pred, __proj1, __proj2);
   }
 
   template <input_range _R1, input_range _R2,
             class _Pred = ranges::equal_to, class _Proj1 = identity, class _Proj2 = identity>
     requires indirectly_comparable<iterator_t<_R1>, iterator_t<_R2>, _Pred, _Proj1, _Proj2>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   mismatch_result<borrowed_iterator_t<_R1>, borrowed_iterator_t<_R2>>
   operator()(_R1&& __r1, _R2&& __r2, _Pred __pred = {}, _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const {
     return __go(ranges::begin(__r1), ranges::end(__r1), ranges::begin(__r2), ranges::end(__r2),
                 __pred, __proj1, __proj2);
   }
 };
 } // namespace __mismatch
 

libcxx/include/__algorithm/ranges_none_of.h

for (; __first != __last; ++__first) {
       if (std::invoke(__pred, std::invoke(__proj, *__first)))
         return false;
     }
     return true;
   }
 
   template <input_iterator _Iter, sentinel_for<_Iter> _Sent, class _Proj = identity,
             indirect_unary_predicate<projected<_Iter, _Proj>> _Pred>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Iter __first, _Sent __last, _Pred __pred = {}, _Proj __proj = {}) const {
     return __none_of_impl(std::move(__first), std::move(__last), __pred, __proj);
   }
 
   template <input_range _Range, class _Proj = identity,
             indirect_unary_predicate<projected<iterator_t<_Range>, _Proj>> _Pred>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   bool operator()(_Range&& __range, _Pred __pred, _Proj __proj = {}) const {
     return __none_of_impl(ranges::begin(__range), ranges::end(__range), __pred, __proj);
   }
 };
 } // namespace __none_of
 
 inline namespace __cpo {
   inline constexpr auto none_of = __none_of::__fn{};
 } // namespace __cpo
 } // namespace ranges
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER > 17
 
 #endif // _LIBCPP___ALGORITHM_RANGES_NONE_OF_H

libcxx/include/__algorithm/ranges_remove.h

 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace ranges {
 namespace __remove {
 struct __fn {
 
   template <permutable _Iter, sentinel_for<_Iter> _Sent, class _Type, class _Proj = identity>
     requires indirect_binary_predicate<ranges::equal_to, projected<_Iter, _Proj>, const _Type*>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   subrange<_Iter> operator()(_Iter __first, _Sent __last, const _Type& __value, _Proj __proj = {}) const {
     auto __pred = [&](auto&& __other) { return __value == __other; };
     return ranges::__remove_if_impl(std::move(__first), std::move(__last), __pred, __proj);
   }
 
   template <forward_range _Range, class _Type, class _Proj = identity>
     requires permutable<iterator_t<_Range>>
           && indirect_binary_predicate<ranges::equal_to, projected<iterator_t<_Range>, _Proj>, const _Type*>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_subrange_t<_Range> operator()(_Range&& __range, const _Type& __value, _Proj __proj = {}) const {
     auto __pred = [&](auto&& __other) { return __value == __other; };
     return ranges::__remove_if_impl(ranges::begin(__range), ranges::end(__range), __pred, __proj);
   }
 };
 } // namespace __remove
 
 inline namespace __cpo {

libcxx/include/__algorithm/ranges_remove_if.h

 }
 
 namespace __remove_if {
 struct __fn {
 
   template <permutable _Iter, sentinel_for<_Iter> _Sent,
             class _Proj = identity,
             indirect_unary_predicate<projected<_Iter, _Proj>> _Pred>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   subrange<_Iter> operator()(_Iter __first, _Sent __last, _Pred __pred, _Proj __proj = {}) const {
     return ranges::__remove_if_impl(std::move(__first), std::move(__last), __pred, __proj);
   }
 
   template <forward_range _Range,
             class _Proj = identity,
             indirect_unary_predicate<projected<iterator_t<_Range>, _Proj>> _Pred>
     requires permutable<iterator_t<_Range>>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_subrange_t<_Range> operator()(_Range&& __range, _Pred __pred, _Proj __proj = {}) const {
     return ranges::__remove_if_impl(ranges::begin(__range), ranges::end(__range), __pred, __proj);
   }
 
 };
 } // namespace __remove_if
 
 inline namespace __cpo {

libcxx/include/__algorithm/ranges_search.h

struct __fn {
   }
 
   template <forward_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
             forward_iterator _Iter2, sentinel_for<_Iter2> _Sent2,
             class _Pred = ranges::equal_to,
             class _Proj1 = identity,
             class _Proj2 = identity>
     requires indirectly_comparable<_Iter1, _Iter2, _Pred, _Proj1, _Proj2>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   subrange<_Iter1> operator()(_Iter1 __first1, _Sent1 __last1,
                               _Iter2 __first2, _Sent2 __last2,
                               _Pred __pred = {},
                               _Proj1 __proj1 = {},
                               _Proj2 __proj2 = {}) const {
     return __ranges_search_impl(__first1, __last1, __first2, __last2, __pred, __proj1, __proj2);
   }
 
   template <forward_range _Range1,
             forward_range _Range2,
             class _Pred = ranges::equal_to,
             class _Proj1 = identity,
             class _Proj2 = identity>
     requires indirectly_comparable<iterator_t<_Range1>, iterator_t<_Range2>, _Pred, _Proj1, _Proj2>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_subrange_t<_Range1> operator()(_Range1&& __range1,
                                           _Range2&& __range2,
                                           _Pred __pred = {},
                                           _Proj1 __proj1 = {},
                                           _Proj2 __proj2 = {}) const {
     auto __first1 = ranges::begin(__range1);
     if constexpr (sized_range<_Range2>) {
       auto __size2 = ranges::size(__range2);

libcxx/include/__algorithm/ranges_search_n.h

_LIBCPP_HIDE_FROM_ABI static constexpr subrange<_Iter1> __ranges_search_n_impl(
     return {std::move(__ret.first), std::move(__ret.second)};
   }
 
   template <forward_iterator _Iter, sentinel_for<_Iter> _Sent,
             class _Type,
             class _Pred = ranges::equal_to,
             class _Proj = identity>
     requires indirectly_comparable<_Iter, const _Type*, _Pred, _Proj>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   subrange<_Iter> operator()(_Iter __first, _Sent __last,
                              iter_difference_t<_Iter> __count,
                              const _Type& __value,
                              _Pred __pred = {},
                              _Proj __proj = _Proj{}) const {
     return __ranges_search_n_impl(__first, __last, __count, __value, __pred, __proj);
   }
 
   template <forward_range _Range, class _Type, class _Pred = ranges::equal_to, class _Proj = identity>
     requires indirectly_comparable<iterator_t<_Range>, const _Type*, _Pred, _Proj>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_subrange_t<_Range> operator()(_Range&& __range,
                                          range_difference_t<_Range> __count,
                                          const _Type& __value,
                                          _Pred __pred = {},
                                          _Proj __proj = {}) const {
     auto __first = ranges::begin(__range);
     if (__count <= 0)
       return {__first, __first};

libcxx/include/__algorithm/ranges_unique.h

 namespace __unique {
 
   struct __fn {
     template <
         permutable _Iter,
         sentinel_for<_Iter> _Sent,
         class _Proj                                                  = identity,
         indirect_equivalence_relation<projected<_Iter, _Proj>> _Comp = ranges::equal_to>
-    _LIBCPP_HIDE_FROM_ABI constexpr subrange<_Iter>
+    _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr subrange<_Iter>
     operator()(_Iter __first, _Sent __last, _Comp __comp = {}, _Proj __proj = {}) const {
       auto __ret = std::__unique<_RangeAlgPolicy>(
           std::move(__first), std::move(__last), std::__make_projected(__comp, __proj));
       return {std::move(__ret.first), std::move(__ret.second)};
     }
 
     template <
         forward_range _Range,
         class _Proj                                                               = identity,
         indirect_equivalence_relation<projected<iterator_t<_Range>, _Proj>> _Comp = ranges::equal_to>
       requires permutable<iterator_t<_Range>>
-    _LIBCPP_HIDE_FROM_ABI constexpr borrowed_subrange_t<_Range>
+    _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr borrowed_subrange_t<_Range>
     operator()(_Range&& __range, _Comp __comp = {}, _Proj __proj = {}) const {
       auto __ret = std::__unique<_RangeAlgPolicy>(
           ranges::begin(__range), ranges::end(__range), std::__make_projected(__comp, __proj));
       return {std::move(__ret.first), std::move(__ret.second)};
     }
   };
 
 } // namespace __unique

libcxx/include/__algorithm/ranges_upper_bound.h

 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace ranges {
 namespace __upper_bound {
 struct __fn {
   template <forward_iterator _Iter, sentinel_for<_Iter> _Sent, class _Type, class _Proj = identity,
             indirect_strict_weak_order<const _Type*, projected<_Iter, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   _Iter operator()(_Iter __first, _Sent __last, const _Type& __value, _Comp __comp = {}, _Proj __proj = {}) const {
     auto __comp_lhs_rhs_swapped = [&](const auto& __lhs, const auto& __rhs) {
       return !std::invoke(__comp, __rhs, __lhs);
     };
 
     return std::__lower_bound_impl<_RangeAlgPolicy>(__first, __last, __value, __comp_lhs_rhs_swapped, __proj);
   }
 
   template <forward_range _Range, class _Type, class _Proj = identity,
             indirect_strict_weak_order<const _Type*, projected<iterator_t<_Range>, _Proj>> _Comp = ranges::less>
-  _LIBCPP_HIDE_FROM_ABI constexpr
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr
   borrowed_iterator_t<_Range> operator()(_Range&& __r,
                                          const _Type& __value,
                                          _Comp __comp = {},
                                          _Proj __proj = {}) const {
     auto __comp_lhs_rhs_swapped = [&](const auto& __lhs, const auto& __rhs) {
       return !std::invoke(__comp, __rhs, __lhs);
     };
 

libcxx/test/libcxx/diagnostics/nodiscard_extensions.compile.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // Test that entities declared [[nodiscard]] as at extension by libc++, are
-// declared as such when _LIBCPP_DISABLE_NODISCARD_EXT is specified.
-
-// This test intentionally leaks memory, so it is unsupported under ASAN.
-// UNSUPPORTED: asan
+// not declared as such when _LIBCPP_DISABLE_NODISCARD_EXT is specified.
 
 // All entities to which libc++ applies [[nodiscard]] as an extension should
 // be tested here and in nodiscard_extensions.verify.cpp. They should also
 // be listed in `UsingLibcxx.rst` in the documentation for the extension.
 
 // Disable any builtin recognition of std::* in the compiler, that might also
 // trigger -Wunused-value warnings.
 // ADDITIONAL_COMPILE_FLAGS: -fno-builtin
std::find_end(std::begin(arr), std::end(arr), std::begin(arr), std::end(arr),
                 std::greater<int>());
   std::find_first_of(std::begin(arr), std::end(arr), std::begin(arr),
                      std::end(arr));
   std::find_first_of(std::begin(arr), std::end(arr), std::begin(arr),
                      std::end(arr), std::greater<int>());
   std::find_if_not(std::begin(arr), std::end(arr), P());
   std::find_if(std::begin(arr), std::end(arr), P());
   std::find(std::begin(arr), std::end(arr), 1);
-  std::get_temporary_buffer<int>(1); // intentional memory leak.
+  std::get_temporary_buffer<int>(1);
   std::includes(std::begin(arr), std::end(arr), std::begin(arr), std::end(arr));
   std::includes(std::begin(arr), std::end(arr), std::begin(arr), std::end(arr),
                 std::greater<int>());
   std::is_heap_until(std::begin(arr), std::end(arr));
   std::is_heap_until(std::begin(arr), std::end(arr), std::greater<int>());
   std::is_heap(std::begin(arr), std::end(arr));
   std::is_heap(std::begin(arr), std::end(arr), std::greater<int>());
   std::is_partitioned(std::begin(arr), std::end(arr), P());

libcxx/test/libcxx/diagnostics/ranges.nodiscard.compile.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Check that ranges algorithms aren't marked [[nodiscard]] when
+// _LIBCPP_DISBALE_NODISCARD_EXT is defined
+
+// Disable any builtin recognition of std::* in the compiler, that might also
+// trigger -Wunused-value warnings.
+// ADDITIONAL_COMPILE_FLAGS: -fno-builtin
+
+// UNSUPPORTED: c++03, c++11, c++14 ,c++17
+
+// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_DISABLE_NODISCARD_EXT
+
+#include <algorithm>
+
+void test() {
+  int range[1];
+  int* iter = range;
+  auto pred = [](auto...) { return true; };
+  std::ranges::adjacent_find(range);
+  std::ranges::adjacent_find(iter, iter);
+  std::ranges::all_of(range, pred);
+  std::ranges::all_of(iter, iter, pred);
+  std::ranges::any_of(range, pred);
+  std::ranges::any_of(iter, iter, pred);
+  std::ranges::binary_search(range, 1);
+  std::ranges::binary_search(iter, iter, 1);
+  std::ranges::clamp(1, 2, 3);
+  std::ranges::count_if(range, pred);
+  std::ranges::count_if(iter, iter, pred);
+  std::ranges::count(range, 1);
+  std::ranges::count(iter, iter, 1);
+  std::ranges::equal_range(range, 1);
+  std::ranges::equal_range(iter, iter, 1);
+  std::ranges::equal(range, range);
+  std::ranges::equal(iter, iter, iter, iter);
+  std::ranges::find_end(range, range);
+  std::ranges::find_end(iter, iter, iter, iter);
+  std::ranges::find_first_of(range, range);
+  std::ranges::find_first_of(iter, iter, iter, iter);
+  std::ranges::find_if_not(range, pred);
+  std::ranges::find_if_not(iter, iter, pred);
+  std::ranges::find_if(range, pred);
+  std::ranges::find_if(iter, iter, pred);
+  std::ranges::find(range, 1);
+  std::ranges::find(iter, iter, 1);
+  std::ranges::includes(range, range);
+  std::ranges::includes(iter, iter, iter, iter);
+  std::ranges::is_heap_until(range);
+  std::ranges::is_heap_until(iter, iter);
+  std::ranges::is_heap(range);
+  std::ranges::is_heap(iter, iter);
+  std::ranges::is_partitioned(range, pred);
+  std::ranges::is_partitioned(iter, iter, pred);
+  std::ranges::is_permutation(range, range);
+  std::ranges::is_permutation(iter, iter, iter, iter);
+  std::ranges::is_sorted_until(range);
+  std::ranges::is_sorted_until(iter, iter);
+  std::ranges::is_sorted(range);
+  std::ranges::is_sorted(iter, iter);
+  std::ranges::lexicographical_compare(range, range);
+  std::ranges::lexicographical_compare(iter, iter, iter, iter);
+  std::ranges::lower_bound(range, 1);
+  std::ranges::lower_bound(iter, iter, 1);
+  std::ranges::max_element(range);
+  std::ranges::max_element(iter, iter);
+  std::ranges::max(1, 2);
+  std::ranges::max({1, 2, 3});
+  std::ranges::max(range);
+  std::ranges::minmax_element(range);
+  std::ranges::minmax_element(iter, iter);
+  std::ranges::minmax(1, 2);
+  std::ranges::minmax({1, 2, 3});
+  std::ranges::minmax(range);
+  std::ranges::mismatch(range, range);
+  std::ranges::mismatch(iter, iter, iter, iter);
+  std::ranges::none_of(range, pred);
+  std::ranges::none_of(iter, iter, pred);
+  std::ranges::remove_if(range, pred);
+  std::ranges::remove_if(iter, iter, pred);
+  std::ranges::remove(range, 1);
+  std::ranges::remove(iter, iter, 1);
+  std::ranges::search_n(range, 1, 1);
+  std::ranges::search_n(iter, iter, 1, 1);
+  std::ranges::search(range, range);
+  std::ranges::search(iter, iter, iter, iter);
+  std::ranges::unique(range);
+  std::ranges::unique(iter, iter);
+  std::ranges::upper_bound(range, 1);
+  std::ranges::upper_bound(iter, iter, 1);
+}

libcxx/test/libcxx/diagnostics/ranges.nodiscard.verify.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Check that ranges algorithms aren't marked [[nodiscard]] when
+// _LIBCPP_DISBALE_NODISCARD_EXT is defined
+
+// Disable any builtin recognition of std::* in the compiler, that might also
+// trigger -Wunused-value warnings.
+// ADDITIONAL_COMPILE_FLAGS: -fno-builtin
+
+// UNSUPPORTED: c++03, c++11, c++14 ,c++17
+
+#include <algorithm>
+
+void test() {
+  int range[1];
+  int* iter = range;
+  auto pred = [](auto...) { return true; };
+  std::ranges::adjacent_find(range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::adjacent_find(iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::all_of(range, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::all_of(iter, iter, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::any_of(range, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::any_of(iter, iter, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::binary_search(range, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::binary_search(iter, iter, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::clamp(1, 2, 3); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::count_if(range, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::count_if(iter, iter, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::count(range, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::count(iter, iter, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::equal_range(range, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::equal_range(iter, iter, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::equal(range, range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::equal(iter, iter, iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::find_end(range, range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::find_end(iter, iter, iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::find_first_of(range, range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::find_first_of(iter, iter, iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::find_if_not(range, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::find_if_not(iter, iter, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::find_if(range, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::find_if(iter, iter, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::find(range, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::find(iter, iter, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::includes(range, range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::includes(iter, iter, iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::is_heap_until(range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::is_heap_until(iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::is_heap(range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::is_heap(iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::is_partitioned(range, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::is_partitioned(iter, iter, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::is_permutation(range, range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::is_permutation(iter, iter, iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::is_sorted_until(range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::is_sorted_until(iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::is_sorted(range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::is_sorted(iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::lexicographical_compare(range, range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::lexicographical_compare(iter, iter, iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::lower_bound(range, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::lower_bound(iter, iter, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::max_element(range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::max_element(iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::max(1, 2); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::max({1, 2, 3}); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::max(range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::minmax_element(range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::minmax_element(iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::minmax(1, 2); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::minmax({1, 2, 3}); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::minmax(range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::mismatch(range, range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::mismatch(iter, iter, iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::none_of(range, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::none_of(iter, iter, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::remove_if(range, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::remove_if(iter, iter, pred); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::remove(range, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::remove(iter, iter, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::search_n(range, 1, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::search_n(iter, iter, 1, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::search(range, range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::search(iter, iter, iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::unique(range); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::unique(iter, iter); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::upper_bound(range, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  std::ranges::upper_bound(iter, iter, 1); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+}