libcxx: Update to Clang 20.

See:

* https://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc/77319
* https://discourse.llvm.org/t/rfc-project-hand-in-hand-llvm-libc-libc-code-sharing/77701

We're dropping support for C++03 for Zig due to the first change; it would be
insane to ship 1018 duplicate header files just for this outdated use case.

As a result of the second change, I had to bring in a subset of the headers from
llvm-libc since libc++ now depends on these. Hopefully we can continue to get
away with not copying the entirety of llvm-libc.

Author: alexrp

lib/libcxx/include/__algorithm/adjacent_find.h

@@ -11,9 +11,9 @@
 #define _LIBCPP___ALGORITHM_ADJACENT_FIND_H
 
 #include <__algorithm/comp.h>
-#include <__algorithm/iterator_operations.h>
 #include <__config>
-#include <__iterator/iterator_traits.h>
+#include <__functional/identity.h>
+#include <__type_traits/invoke.h>
 #include <__utility/move.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -25,28 +25,30 @@ _LIBCPP_PUSH_MACROS
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Iter, class _Sent, class _BinaryPredicate>
-_LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Iter
-__adjacent_find(_Iter __first, _Sent __last, _BinaryPredicate&& __pred) {
+template <class _Iter, class _Sent, class _Pred, class _Proj>
+[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Iter
+__adjacent_find(_Iter __first, _Sent __last, _Pred& __pred, _Proj& __proj) {
   if (__first == __last)
     return __first;
+
   _Iter __i = __first;
   while (++__i != __last) {
-    if (__pred(*__first, *__i))
+    if (std::__invoke(__pred, std::__invoke(__proj, *__first), std::__invoke(__proj, *__i)))
       return __first;
     __first = __i;
   }
   return __i;
 }
 
 template <class _ForwardIterator, class _BinaryPredicate>
-_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
 adjacent_find(_ForwardIterator __first, _ForwardIterator __last, _BinaryPredicate __pred) {
-  return std::__adjacent_find(std::move(__first), std::move(__last), __pred);
+  __identity __proj;
+  return std::__adjacent_find(std::move(__first), std::move(__last), __pred, __proj);
 }
 
 template <class _ForwardIterator>
-_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
 adjacent_find(_ForwardIterator __first, _ForwardIterator __last) {
   return std::adjacent_find(std::move(__first), std::move(__last), __equal_to());
 }

lib/libcxx/include/__algorithm/all_of.h

@@ -11,22 +11,32 @@
 #define _LIBCPP___ALGORITHM_ALL_OF_H
 
 #include <__config>
+#include <__functional/identity.h>
+#include <__type_traits/invoke.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _InputIterator, class _Predicate>
-_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
-all_of(_InputIterator __first, _InputIterator __last, _Predicate __pred) {
-  for (; __first != __last; ++__first)
-    if (!__pred(*__first))
+template <class _Iter, class _Sent, class _Proj, class _Pred>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool
+__all_of(_Iter __first, _Sent __last, _Pred& __pred, _Proj& __proj) {
+  for (; __first != __last; ++__first) {
+    if (!std::__invoke(__pred, std::__invoke(__proj, *__first)))
       return false;
+  }
   return true;
 }
 
+template <class _InputIterator, class _Predicate>
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
+all_of(_InputIterator __first, _InputIterator __last, _Predicate __pred) {
+  __identity __proj;
+  return std::__all_of(__first, __last, __pred, __proj);
+}
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___ALGORITHM_ALL_OF_H

lib/libcxx/include/__algorithm/any_of.h

@@ -11,22 +11,32 @@
 #define _LIBCPP___ALGORITHM_ANY_OF_H
 
 #include <__config>
+#include <__functional/identity.h>
+#include <__type_traits/invoke.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _InputIterator, class _Predicate>
-_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
-any_of(_InputIterator __first, _InputIterator __last, _Predicate __pred) {
-  for (; __first != __last; ++__first)
-    if (__pred(*__first))
+template <class _Iter, class _Sent, class _Proj, class _Pred>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool
+__any_of(_Iter __first, _Sent __last, _Pred& __pred, _Proj& __proj) {
+  for (; __first != __last; ++__first) {
+    if (std::__invoke(__pred, std::__invoke(__proj, *__first)))
       return true;
+  }
   return false;
 }
 
+template <class _InputIterator, class _Predicate>
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
+any_of(_InputIterator __first, _InputIterator __last, _Predicate __pred) {
+  __identity __proj;
+  return std::__any_of(__first, __last, __pred, __proj);
+}
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___ALGORITHM_ANY_OF_H

lib/libcxx/include/__algorithm/binary_search.h

@@ -13,7 +13,6 @@
 #include <__algorithm/comp_ref_type.h>
 #include <__algorithm/lower_bound.h>
 #include <__config>
-#include <__iterator/iterator_traits.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -22,14 +21,14 @@
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _ForwardIterator, class _Tp, class _Compare>
-_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
 binary_search(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value, _Compare __comp) {
   __first = std::lower_bound<_ForwardIterator, _Tp, __comp_ref_type<_Compare> >(__first, __last, __value, __comp);
   return __first != __last && !__comp(__value, *__first);
 }
 
 template <class _ForwardIterator, class _Tp>
-_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
 binary_search(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) {
   return std::binary_search(__first, __last, __value, __less<>());
 }

lib/libcxx/include/__algorithm/comp.h

@@ -11,6 +11,7 @@
 
 #include <__config>
 #include <__type_traits/desugars_to.h>
+#include <__type_traits/is_integral.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -44,6 +45,9 @@ struct __less<void, void> {
 template <class _Tp>
 inline const bool __desugars_to_v<__less_tag, __less<>, _Tp, _Tp> = true;
 
+template <class _Tp>
+inline const bool __desugars_to_v<__totally_ordered_less_tag, __less<>, _Tp, _Tp> = is_integral<_Tp>::value;
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___ALGORITHM_COMP_H

lib/libcxx/include/__algorithm/comp_ref_type.h

@@ -56,10 +56,10 @@ struct __debug_less {
 // Pass the comparator by lvalue reference. Or in the debug mode, using a debugging wrapper that stores a reference.
 #if _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_DEBUG
 template <class _Comp>
-using __comp_ref_type = __debug_less<_Comp>;
+using __comp_ref_type _LIBCPP_NODEBUG = __debug_less<_Comp>;
 #else
 template <class _Comp>
-using __comp_ref_type = _Comp&;
+using __comp_ref_type _LIBCPP_NODEBUG = _Comp&;
 #endif
 
 _LIBCPP_END_NAMESPACE_STD

lib/libcxx/include/__algorithm/copy.h

@@ -11,11 +11,12 @@
 
 #include <__algorithm/copy_move_common.h>
 #include <__algorithm/for_each_segment.h>
-#include <__algorithm/iterator_operations.h>
 #include <__algorithm/min.h>
 #include <__config>
+#include <__iterator/iterator_traits.h>
 #include <__iterator/segmented_iterator.h>
 #include <__type_traits/common_type.h>
+#include <__type_traits/enable_if.h>
 #include <__utility/move.h>
 #include <__utility/pair.h>
 
@@ -28,10 +29,9 @@ _LIBCPP_PUSH_MACROS
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class, class _InIter, class _Sent, class _OutIter>
+template <class _InIter, class _Sent, class _OutIter>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter> __copy(_InIter, _Sent, _OutIter);
 
-template <class _AlgPolicy>
 struct __copy_impl {
   template <class _InIter, class _Sent, class _OutIter>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
@@ -47,7 +47,7 @@ struct __copy_impl {
 
   template <class _InIter, class _OutIter>
   struct _CopySegment {
-    using _Traits = __segmented_iterator_traits<_InIter>;
+    using _Traits _LIBCPP_NODEBUG = __segmented_iterator_traits<_InIter>;
 
     _OutIter& __result_;
 
@@ -56,7 +56,7 @@ struct __copy_impl {
 
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void
     operator()(typename _Traits::__local_iterator __lfirst, typename _Traits::__local_iterator __llast) {
-      __result_ = std::__copy<_AlgPolicy>(__lfirst, __llast, std::move(__result_)).second;
+      __result_ = std::__copy(__lfirst, __llast, std::move(__result_)).second;
     }
   };
 
@@ -85,7 +85,7 @@ struct __copy_impl {
     while (true) {
       auto __local_last = _Traits::__end(__segment_iterator);
       auto __size       = std::min<_DiffT>(__local_last - __local_first, __last - __first);
-      auto __iters      = std::__copy<_AlgPolicy>(__first, __first + __size, __local_first);
+      auto __iters      = std::__copy(__first, __first + __size, __local_first);
       __first           = std::move(__iters.first);
 
       if (__first == __last)
@@ -103,17 +103,16 @@ struct __copy_impl {
   }
 };
 
-template <class _AlgPolicy, class _InIter, class _Sent, class _OutIter>
+template <class _InIter, class _Sent, class _OutIter>
 pair<_InIter, _OutIter> inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
 __copy(_InIter __first, _Sent __last, _OutIter __result) {
-  return std::__copy_move_unwrap_iters<__copy_impl<_AlgPolicy> >(
-      std::move(__first), std::move(__last), std::move(__result));
+  return std::__copy_move_unwrap_iters<__copy_impl>(std::move(__first), std::move(__last), std::move(__result));
 }
 
 template <class _InputIterator, class _OutputIterator>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
 copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result) {
-  return std::__copy<_ClassicAlgPolicy>(__first, __last, __result).second;
+  return std::__copy(__first, __last, __result).second;
 }
 
 _LIBCPP_END_NAMESPACE_STD

lib/libcxx/include/__algorithm/copy_backward.h

@@ -13,8 +13,10 @@
 #include <__algorithm/iterator_operations.h>
 #include <__algorithm/min.h>
 #include <__config>
+#include <__iterator/iterator_traits.h>
 #include <__iterator/segmented_iterator.h>
 #include <__type_traits/common_type.h>
+#include <__type_traits/enable_if.h>
 #include <__type_traits/is_constructible.h>
 #include <__utility/move.h>
 #include <__utility/pair.h>

lib/libcxx/include/__algorithm/copy_if.h

@@ -10,25 +10,41 @@
 #define _LIBCPP___ALGORITHM_COPY_IF_H
 
 #include <__config>
+#include <__functional/identity.h>
+#include <__type_traits/invoke.h>
+#include <__utility/move.h>
+#include <__utility/pair.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _InputIterator, class _OutputIterator, class _Predicate>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
-copy_if(_InputIterator __first, _InputIterator __last, _OutputIterator __result, _Predicate __pred) {
+template <class _InIter, class _Sent, class _OutIter, class _Proj, class _Pred>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
+__copy_if(_InIter __first, _Sent __last, _OutIter __result, _Pred& __pred, _Proj& __proj) {
   for (; __first != __last; ++__first) {
-    if (__pred(*__first)) {
+    if (std::__invoke(__pred, std::__invoke(__proj, *__first))) {
       *__result = *__first;
       ++__result;
     }
   }
-  return __result;
+  return std::make_pair(std::move(__first), std::move(__result));
+}
+
+template <class _InputIterator, class _OutputIterator, class _Predicate>
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
+copy_if(_InputIterator __first, _InputIterator __last, _OutputIterator __result, _Predicate __pred) {
+  __identity __proj;
+  return std::__copy_if(__first, __last, __result, __pred, __proj).second;
 }
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif // _LIBCPP___ALGORITHM_COPY_IF_H

lib/libcxx/include/__algorithm/copy_move_common.h

@@ -9,10 +9,10 @@
 #ifndef _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H
 #define _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H
 
-#include <__algorithm/iterator_operations.h>
 #include <__algorithm/unwrap_iter.h>
 #include <__algorithm/unwrap_range.h>
 #include <__config>
+#include <__cstddef/size_t.h>
 #include <__iterator/iterator_traits.h>
 #include <__memory/pointer_traits.h>
 #include <__string/constexpr_c_functions.h>
@@ -24,7 +24,6 @@
 #include <__type_traits/is_volatile.h>
 #include <__utility/move.h>
 #include <__utility/pair.h>
-#include <cstddef>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header