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, 70 insertions, 0 deletions

diff --git a/lib/libcxx/src/call_once.cpp b/lib/libcxx/src/call_once.cpp
new file mode 100644
index 0000000000..b596518a65
--- /dev/null
+++ b/lib/libcxx/src/call_once.cpp
@@ -0,0 +1,70 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include <__mutex/once_flag.h>
+#include <__utility/exception_guard.h>
+
+#ifndef _LIBCPP_HAS_NO_THREADS
+#  include <__threading_support>
+#endif
+
+#include "include/atomic_support.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// If dispatch_once_f ever handles C++ exceptions, and if one can get to it
+// without illegal macros (unexpected macros not beginning with _UpperCase or
+// __lowercase), and if it stops spinning waiting threads, then call_once should
+// call into dispatch_once_f instead of here. Relevant radar this code needs to
+// keep in sync with:  7741191.
+
+#ifndef _LIBCPP_HAS_NO_THREADS
+static constinit __libcpp_mutex_t mut  = _LIBCPP_MUTEX_INITIALIZER;
+static constinit __libcpp_condvar_t cv = _LIBCPP_CONDVAR_INITIALIZER;
+#endif
+
+void __call_once(volatile once_flag::_State_type& flag, void* arg, void (*func)(void*)) {
+#if defined(_LIBCPP_HAS_NO_THREADS)
+
+  if (flag == once_flag::_Unset) {
+    auto guard = std::__make_exception_guard([&flag] { flag = once_flag::_Unset; });
+    flag       = once_flag::_Pending;
+    func(arg);
+    flag = once_flag::_Complete;
+    guard.__complete();
+  }
+
+#else // !_LIBCPP_HAS_NO_THREADS
+
+  __libcpp_mutex_lock(&mut);
+  while (flag == once_flag::_Pending)
+    __libcpp_condvar_wait(&cv, &mut);
+  if (flag == once_flag::_Unset) {
+    auto guard = std::__make_exception_guard([&flag] {
+      __libcpp_mutex_lock(&mut);
+      __libcpp_relaxed_store(&flag, once_flag::_Unset);
+      __libcpp_mutex_unlock(&mut);
+      __libcpp_condvar_broadcast(&cv);
+    });
+
+    __libcpp_relaxed_store(&flag, once_flag::_Pending);
+    __libcpp_mutex_unlock(&mut);
+    func(arg);
+    __libcpp_mutex_lock(&mut);
+    __libcpp_atomic_store(&flag, once_flag::_Complete, _AO_Release);
+    __libcpp_mutex_unlock(&mut);
+    __libcpp_condvar_broadcast(&cv);
+    guard.__complete();
+  } else {
+    __libcpp_mutex_unlock(&mut);
+  }
+
+#endif // !_LIBCPP_HAS_NO_THREADS
+}
+
+_LIBCPP_END_NAMESPACE_STD