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.

lib/libcxx/src/tz.cpp

@@ -0,0 +1,146 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// For information see https://libcxx.llvm.org/DesignDocs/TimeZone.html
+
+#include <chrono>
+#include <filesystem>
+#include <fstream>
+#include <stdexcept>
+#include <string>
+
+// Contains a parser for the IANA time zone data files.
+//
+// These files can be found at https://data.iana.org/time-zones/ and are in the
+// public domain. Information regarding the input can be found at
+// https://data.iana.org/time-zones/tz-how-to.html and
+// https://man7.org/linux/man-pages/man8/zic.8.html.
+//
+// As indicated at https://howardhinnant.github.io/date/tz.html#Installation
+// For Windows another file seems to be required
+// https://raw.githubusercontent.com/unicode-org/cldr/master/common/supplemental/windowsZones.xml
+// This file seems to contain the mapping of Windows time zone name to IANA
+// time zone names.
+//
+// However this article mentions another way to do the mapping on Windows
+// https://devblogs.microsoft.com/oldnewthing/20210527-00/?p=105255
+// This requires Windows 10 Version 1903, which was released in May of 2019
+// and considered end of life in December 2020
+// https://learn.microsoft.com/en-us/lifecycle/announcements/windows-10-1903-end-of-servicing
+//
+// TODO TZDB Implement the Windows mapping in tzdb::current_zone
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace chrono {
+
+// This function is weak so it can be overriden in the tests. The
+// declaration is in the test header test/support/test_tzdb.h
+_LIBCPP_WEAK string_view __libcpp_tzdb_directory() {
+#if defined(__linux__)
+  return "/usr/share/zoneinfo/";
+#else
+#  error "unknown path to the IANA Time Zone Database"
+#endif
+}
+
+[[nodiscard]] static bool __is_whitespace(int __c) { return __c == ' ' || __c == '\t'; }
+
+static void __skip_optional_whitespace(istream& __input) {
+  while (chrono::__is_whitespace(__input.peek()))
+    __input.get();
+}
+
+static void __skip_mandatory_whitespace(istream& __input) {
+  if (!chrono::__is_whitespace(__input.get()))
+    std::__throw_runtime_error("corrupt tzdb: expected whitespace");
+
+  chrono::__skip_optional_whitespace(__input);
+}
+
+static void __matches(istream& __input, char __expected) {
+  if (std::tolower(__input.get()) != __expected)
+    std::__throw_runtime_error((string("corrupt tzdb: expected character '") + __expected + '\'').c_str());
+}
+
+static void __matches(istream& __input, string_view __expected) {
+  for (auto __c : __expected)
+    if (std::tolower(__input.get()) != __c)
+      std::__throw_runtime_error((string("corrupt tzdb: expected string '") + string(__expected) + '\'').c_str());
+}
+
+[[nodiscard]] static string __parse_string(istream& __input) {
+  string __result;
+  while (true) {
+    int __c = __input.get();
+    switch (__c) {
+    case ' ':
+    case '\t':
+    case '\n':
+      __input.unget();
+      [[fallthrough]];
+    case istream::traits_type::eof():
+      if (__result.empty())
+        std::__throw_runtime_error("corrupt tzdb: expected a string");
+
+      return __result;
+
+    default:
+      __result.push_back(__c);
+    }
+  }
+}
+
+static string __parse_version(istream& __input) {
+  // The first line in tzdata.zi contains
+  //    # version YYYYw
+  // The parser expects this pattern
+  // #\s*version\s*\(.*)
+  // This part is not documented.
+  chrono::__matches(__input, '#');
+  chrono::__skip_optional_whitespace(__input);
+  chrono::__matches(__input, "version");
+  chrono::__skip_mandatory_whitespace(__input);
+  return chrono::__parse_string(__input);
+}
+
+static tzdb __make_tzdb() {
+  tzdb __result;
+
+  filesystem::path __root = chrono::__libcpp_tzdb_directory();
+  ifstream __tzdata{__root / "tzdata.zi"};
+
+  __result.version = chrono::__parse_version(__tzdata);
+  return __result;
+}
+
+//===----------------------------------------------------------------------===//
+//                           Public API
+//===----------------------------------------------------------------------===//
+
+_LIBCPP_NODISCARD_EXT _LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI tzdb_list& get_tzdb_list() {
+  static tzdb_list __result{chrono::__make_tzdb()};
+  return __result;
+}
+
+_LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI const tzdb& reload_tzdb() {
+  if (chrono::remote_version() == chrono::get_tzdb().version)
+    return chrono::get_tzdb();
+
+  return chrono::get_tzdb_list().__emplace_front(chrono::__make_tzdb());
+}
+
+_LIBCPP_NODISCARD_EXT _LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI string remote_version() {
+  filesystem::path __root = chrono::__libcpp_tzdb_directory();
+  ifstream __tzdata{__root / "tzdata.zi"};
+  return chrono::__parse_version(__tzdata);
+}
+
+} // namespace chrono
+
+_LIBCPP_END_NAMESPACE_STD