libcxx: update to LLVM 18

release/18.x branch, commit 78b99c73ee4b96fe9ce0e294d4632326afb2db42

This adds the flag `-D_LIBCPP_HARDENING_MODE` which is determined based
on the Zig optimization mode.

This commit also fixes libunwind, libcxx, and libcxxabi to properly
report sub compilation errors.

1 files changed, 62 insertions, 0 deletions

diff --git a/lib/libcxx/include/__algorithm/find_segment_if.h b/lib/libcxx/include/__algorithm/find_segment_if.h
new file mode 100644
index 0000000000..9d6064f3e2
--- /dev/null
+++ b/lib/libcxx/include/__algorithm/find_segment_if.h
@@ -0,0 +1,62 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___ALGORITHM_FIND_SEGMENT_IF_H
+#define _LIBCPP___ALGORITHM_FIND_SEGMENT_IF_H
+
+#include <__config>
+#include <__iterator/segmented_iterator.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// __find_segment_if is a utility function for optimizing iteration over segmented iterators linearly.
+// [__first, __last) has to be a segmented range. __pred is expected to take a range of local iterators and the __proj.
+// It returns an iterator to the first element that satisfies the predicate, or a one-past-the-end iterator if there was
+// no match. __proj may be anything that should be passed to __pred, but is expected to be a projection to support
+// ranges algorithms, or __identity for classic algorithms.
+
+template <class _SegmentedIterator, class _Pred, class _Proj>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _SegmentedIterator
+__find_segment_if(_SegmentedIterator __first, _SegmentedIterator __last, _Pred __pred, _Proj& __proj) {
+  using _Traits = __segmented_iterator_traits<_SegmentedIterator>;
+
+  auto __sfirst = _Traits::__segment(__first);
+  auto __slast  = _Traits::__segment(__last);
+
+  // We are in a single segment, so we might not be at the beginning or end
+  if (__sfirst == __slast)
+    return _Traits::__compose(__sfirst, __pred(_Traits::__local(__first), _Traits::__local(__last), __proj));
+
+  { // We have more than one segment. Iterate over the first segment, since we might not start at the beginning
+    auto __llast = _Traits::__end(__sfirst);
+    auto __liter = __pred(_Traits::__local(__first), __llast, __proj);
+    if (__liter != __llast)
+      return _Traits::__compose(__sfirst, __liter);
+  }
+  ++__sfirst;
+
+  // Iterate over the segments which are guaranteed to be completely in the range
+  while (__sfirst != __slast) {
+    auto __llast = _Traits::__end(__sfirst);
+    auto __liter = __pred(_Traits::__begin(__sfirst), _Traits::__end(__sfirst), __proj);
+    if (__liter != __llast)
+      return _Traits::__compose(__sfirst, __liter);
+    ++__sfirst;
+  }
+
+  // Iterate over the last segment
+  return _Traits::__compose(__sfirst, __pred(_Traits::__begin(__sfirst), _Traits::__local(__last), __proj));
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___ALGORITHM_FIND_SEGMENT_IF_H