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, 11 insertions, 12 deletions

diff --git a/lib/libcxx/include/__iterator/prev.h b/lib/libcxx/include/__iterator/prev.h
index d31cd8e49b..2f0e6a088e 100644
--- a/lib/libcxx/include/__iterator/prev.h
+++ b/lib/libcxx/include/__iterator/prev.h
@@ -24,13 +24,14 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _InputIter>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX17
-    typename enable_if<__has_input_iterator_category<_InputIter>::value, _InputIter>::type
-    prev(_InputIter __x, typename iterator_traits<_InputIter>::difference_type __n = 1) {
-  _LIBCPP_ASSERT_UNCATEGORIZED(__n <= 0 || __has_bidirectional_iterator_category<_InputIter>::value,
-                               "Attempt to prev(it, n) with a positive n on a non-bidirectional iterator");
-  _VSTD::advance(__x, -__n);
+template <class _InputIter, __enable_if_t<__has_input_iterator_category<_InputIter>::value, int> = 0>
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 _InputIter
+prev(_InputIter __x, typename iterator_traits<_InputIter>::difference_type __n = 1) {
+  // Calling `advance` with a negative value on a non-bidirectional iterator is a no-op in the current implementation.
+  // Note that this check duplicates the similar check in `std::advance`.
+  _LIBCPP_ASSERT_PEDANTIC(__n <= 0 || __has_bidirectional_iterator_category<_InputIter>::value,
+                          "Attempt to prev(it, n) with a positive n on a non-bidirectional iterator");
+  std::advance(__x, -__n);
   return __x;
 }
 
@@ -43,15 +44,13 @@ namespace __prev {
 
 struct __fn {
   template <bidirectional_iterator _Ip>
-  _LIBCPP_HIDE_FROM_ABI
-  constexpr _Ip operator()(_Ip __x) const {
+  _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x) const {
     --__x;
     return __x;
   }
 
   template <bidirectional_iterator _Ip>
-  _LIBCPP_HIDE_FROM_ABI
-  constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n) const {
+  _LIBCPP_HIDE_FROM_ABI constexpr _Ip operator()(_Ip __x, iter_difference_t<_Ip> __n) const {
     ranges::advance(__x, -__n);
     return __x;
   }
@@ -66,7 +65,7 @@ struct __fn {
 } // namespace __prev
 
 inline namespace __cpo {
-  inline constexpr auto prev = __prev::__fn{};
+inline constexpr auto prev = __prev::__fn{};
 } // namespace __cpo
 } // namespace ranges