Release Cosmopolitan v3.6.0

This release is an atomic upgrade to GCC 14.1.0 with C23 and C++23

third_party/libcxx/fs/directory_entry.cpp

@@ -0,0 +1,73 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 <__config>
+#include <cstdint>
+#include <filesystem>
+#include <system_error>
+
+#include "file_descriptor.h"
+#include "posix_compat.h"
+#include "time_utils.h"
+
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+
+error_code directory_entry::__do_refresh() noexcept {
+  __data_.__reset();
+  error_code failure_ec;
+
+  detail::StatT full_st;
+  file_status st = detail::posix_lstat(__p_, full_st, &failure_ec);
+  if (!status_known(st)) {
+    __data_.__reset();
+    return failure_ec;
+  }
+
+  if (!filesystem::exists(st) || !filesystem::is_symlink(st)) {
+    __data_.__cache_type_    = directory_entry::_RefreshNonSymlink;
+    __data_.__type_          = st.type();
+    __data_.__non_sym_perms_ = st.permissions();
+  } else { // we have a symlink
+    __data_.__sym_perms_ = st.permissions();
+    // Get the information about the linked entity.
+    // Ignore errors from stat, since we don't want errors regarding symlink
+    // resolution to be reported to the user.
+    error_code ignored_ec;
+    st = detail::posix_stat(__p_, full_st, &ignored_ec);
+
+    __data_.__type_          = st.type();
+    __data_.__non_sym_perms_ = st.permissions();
+
+    // If we failed to resolve the link, then only partially populate the
+    // cache.
+    if (!status_known(st)) {
+      __data_.__cache_type_ = directory_entry::_RefreshSymlinkUnresolved;
+      return error_code{};
+    }
+    // Otherwise, we resolved the link, potentially as not existing.
+    // That's OK.
+    __data_.__cache_type_ = directory_entry::_RefreshSymlink;
+  }
+
+  if (filesystem::is_regular_file(st))
+    __data_.__size_ = static_cast<uintmax_t>(full_st.st_size);
+
+  if (filesystem::exists(st)) {
+    __data_.__nlink_ = static_cast<uintmax_t>(full_st.st_nlink);
+
+    // Attempt to extract the mtime, and fail if it's not representable using
+    // file_time_type. For now we ignore the error, as we'll report it when
+    // the value is actually used.
+    error_code ignored_ec;
+    __data_.__write_time_ = detail::__extract_last_write_time(__p_, full_st, &ignored_ec);
+  }
+
+  return failure_ec;
+}
+
+_LIBCPP_END_NAMESPACE_FILESYSTEM

third_party/libcxx/fs/directory_iterator.cpp

@@ -0,0 +1,322 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 <__assert>
+#include <__config>
+#include <errno.h>
+#include <filesystem>
+#include <stack>
+#include <utility>
+
+#include "error.h"
+#include "file_descriptor.h"
+
+#if defined(_LIBCPP_WIN32API)
+#  define WIN32_LEAN_AND_MEAN
+#  define NOMINMAX
+#  include <windows.h>
+#else
+#  include <dirent.h> // for DIR & friends
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+
+using detail::ErrorHandler;
+
+#if defined(_LIBCPP_WIN32API)
+class __dir_stream {
+public:
+  __dir_stream()                               = delete;
+  __dir_stream& operator=(const __dir_stream&) = delete;
+
+  __dir_stream(__dir_stream&& __ds) noexcept
+      : __stream_(__ds.__stream_), __root_(std::move(__ds.__root_)), __entry_(std::move(__ds.__entry_)) {
+    __ds.__stream_ = INVALID_HANDLE_VALUE;
+  }
+
+  __dir_stream(const path& root, directory_options opts, error_code& ec)
+      : __stream_(INVALID_HANDLE_VALUE), __root_(root) {
+    if (root.native().empty()) {
+      ec = make_error_code(errc::no_such_file_or_directory);
+      return;
+    }
+    __stream_ = ::FindFirstFileW((root / "*").c_str(), &__data_);
+    if (__stream_ == INVALID_HANDLE_VALUE) {
+      ec                                  = detail::make_windows_error(GetLastError());
+      const bool ignore_permission_denied = bool(opts & directory_options::skip_permission_denied);
+      if (ignore_permission_denied && ec.value() == static_cast<int>(errc::permission_denied))
+        ec.clear();
+      return;
+    }
+    if (!assign())
+      advance(ec);
+  }
+
+  ~__dir_stream() noexcept {
+    if (__stream_ == INVALID_HANDLE_VALUE)
+      return;
+    close();
+  }
+
+  bool good() const noexcept { return __stream_ != INVALID_HANDLE_VALUE; }
+
+  bool advance(error_code& ec) {
+    while (::FindNextFileW(__stream_, &__data_)) {
+      if (assign())
+        return true;
+    }
+    close();
+    return false;
+  }
+
+  bool assign() {
+    if (!wcscmp(__data_.cFileName, L".") || !wcscmp(__data_.cFileName, L".."))
+      return false;
+    // FIXME: Cache more of this
+    // directory_entry::__cached_data cdata;
+    // cdata.__type_ = get_file_type(__data_);
+    // cdata.__size_ = get_file_size(__data_);
+    // cdata.__write_time_ = get_write_time(__data_);
+    __entry_.__assign_iter_entry(
+        __root_ / __data_.cFileName, directory_entry::__create_iter_result(detail::get_file_type(__data_)));
+    return true;
+  }
+
+private:
+  error_code close() noexcept {
+    error_code ec;
+    if (!::FindClose(__stream_))
+      ec = detail::make_windows_error(GetLastError());
+    __stream_ = INVALID_HANDLE_VALUE;
+    return ec;
+  }
+
+  HANDLE __stream_{INVALID_HANDLE_VALUE};
+  WIN32_FIND_DATAW __data_;
+
+public:
+  path __root_;
+  directory_entry __entry_;
+};
+#else
+class __dir_stream {
+public:
+  __dir_stream()                               = delete;
+  __dir_stream& operator=(const __dir_stream&) = delete;
+
+  __dir_stream(__dir_stream&& other) noexcept
+      : __stream_(other.__stream_), __root_(std::move(other.__root_)), __entry_(std::move(other.__entry_)) {
+    other.__stream_ = nullptr;
+  }
+
+  __dir_stream(const path& root, directory_options opts, error_code& ec) : __stream_(nullptr), __root_(root) {
+    if ((__stream_ = ::opendir(root.c_str())) == nullptr) {
+      ec                      = detail::capture_errno();
+      const bool allow_eacces = bool(opts & directory_options::skip_permission_denied);
+      if (allow_eacces && ec.value() == EACCES)
+        ec.clear();
+      return;
+    }
+    advance(ec);
+  }
+
+  ~__dir_stream() noexcept {
+    if (__stream_)
+      close();
+  }
+
+  bool good() const noexcept { return __stream_ != nullptr; }
+
+  bool advance(error_code& ec) {
+    while (true) {
+      auto str_type_pair = detail::posix_readdir(__stream_, ec);
+      auto& str          = str_type_pair.first;
+      if (str == "." || str == "..") {
+        continue;
+      } else if (ec || str.empty()) {
+        close();
+        return false;
+      } else {
+        __entry_.__assign_iter_entry(__root_ / str, directory_entry::__create_iter_result(str_type_pair.second));
+        return true;
+      }
+    }
+  }
+
+private:
+  error_code close() noexcept {
+    error_code m_ec;
+    if (::closedir(__stream_) == -1)
+      m_ec = detail::capture_errno();
+    __stream_ = nullptr;
+    return m_ec;
+  }
+
+  DIR* __stream_{nullptr};
+
+public:
+  path __root_;
+  directory_entry __entry_;
+};
+#endif
+
+// directory_iterator
+
+directory_iterator::directory_iterator(const path& p, error_code* ec, directory_options opts) {
+  ErrorHandler<void> err("directory_iterator::directory_iterator(...)", ec, &p);
+
+  error_code m_ec;
+  __imp_ = make_shared<__dir_stream>(p, opts, m_ec);
+  if (ec)
+    *ec = m_ec;
+  if (!__imp_->good()) {
+    __imp_.reset();
+    if (m_ec)
+      err.report(m_ec);
+  }
+}
+
+directory_iterator& directory_iterator::__increment(error_code* ec) {
+  _LIBCPP_ASSERT_NON_NULL(__imp_ != nullptr, "Attempting to increment an invalid iterator");
+  ErrorHandler<void> err("directory_iterator::operator++()", ec);
+
+  error_code m_ec;
+  if (!__imp_->advance(m_ec)) {
+    path root = std::move(__imp_->__root_);
+    __imp_.reset();
+    if (m_ec)
+      err.report(m_ec, "at root " PATH_CSTR_FMT, root.c_str());
+  }
+  return *this;
+}
+
+directory_entry const& directory_iterator::__dereference() const {
+  _LIBCPP_ASSERT_NON_NULL(__imp_ != nullptr, "Attempting to dereference an invalid iterator");
+  return __imp_->__entry_;
+}
+
+// recursive_directory_iterator
+
+struct recursive_directory_iterator::__shared_imp {
+  stack<__dir_stream> __stack_;
+  directory_options __options_;
+};
+
+recursive_directory_iterator::recursive_directory_iterator(const path& p, directory_options opt, error_code* ec)
+    : __imp_(nullptr), __rec_(true) {
+  ErrorHandler<void> err("recursive_directory_iterator", ec, &p);
+
+  error_code m_ec;
+  __dir_stream new_s(p, opt, m_ec);
+  if (m_ec)
+    err.report(m_ec);
+  if (m_ec || !new_s.good())
+    return;
+
+  __imp_             = make_shared<__shared_imp>();
+  __imp_->__options_ = opt;
+  __imp_->__stack_.push(std::move(new_s));
+}
+
+void recursive_directory_iterator::__pop(error_code* ec) {
+  _LIBCPP_ASSERT_NON_NULL(__imp_ != nullptr, "Popping the end iterator");
+  if (ec)
+    ec->clear();
+  __imp_->__stack_.pop();
+  if (__imp_->__stack_.size() == 0)
+    __imp_.reset();
+  else
+    __advance(ec);
+}
+
+directory_options recursive_directory_iterator::options() const { return __imp_->__options_; }
+
+int recursive_directory_iterator::depth() const { return __imp_->__stack_.size() - 1; }
+
+const directory_entry& recursive_directory_iterator::__dereference() const { return __imp_->__stack_.top().__entry_; }
+
+recursive_directory_iterator& recursive_directory_iterator::__increment(error_code* ec) {
+  if (ec)
+    ec->clear();
+  if (recursion_pending()) {
+    if (__try_recursion(ec) || (ec && *ec))
+      return *this;
+  }
+  __rec_ = true;
+  __advance(ec);
+  return *this;
+}
+
+void recursive_directory_iterator::__advance(error_code* ec) {
+  ErrorHandler<void> err("recursive_directory_iterator::operator++()", ec);
+
+  const directory_iterator end_it;
+  auto& stack = __imp_->__stack_;
+  error_code m_ec;
+  while (stack.size() > 0) {
+    if (stack.top().advance(m_ec))
+      return;
+    if (m_ec)
+      break;
+    stack.pop();
+  }
+
+  if (m_ec) {
+    path root = std::move(stack.top().__root_);
+    __imp_.reset();
+    err.report(m_ec, "at root " PATH_CSTR_FMT, root.c_str());
+  } else {
+    __imp_.reset();
+  }
+}
+
+bool recursive_directory_iterator::__try_recursion(error_code* ec) {
+  ErrorHandler<void> err("recursive_directory_iterator::operator++()", ec);
+
+  bool rec_sym = bool(options() & directory_options::follow_directory_symlink);
+
+  auto& curr_it = __imp_->__stack_.top();
+
+  bool skip_rec = false;
+  error_code m_ec;
+  if (!rec_sym) {
+    file_status st(curr_it.__entry_.__get_sym_ft(&m_ec));
+    if (m_ec && status_known(st))
+      m_ec.clear();
+    if (m_ec || is_symlink(st) || !is_directory(st))
+      skip_rec = true;
+  } else {
+    file_status st(curr_it.__entry_.__get_ft(&m_ec));
+    if (m_ec && status_known(st))
+      m_ec.clear();
+    if (m_ec || !is_directory(st))
+      skip_rec = true;
+  }
+
+  if (!skip_rec) {
+    __dir_stream new_it(curr_it.__entry_.path(), __imp_->__options_, m_ec);
+    if (new_it.good()) {
+      __imp_->__stack_.push(std::move(new_it));
+      return true;
+    }
+  }
+  if (m_ec) {
+    const bool allow_eacess = bool(__imp_->__options_ & directory_options::skip_permission_denied);
+    if (m_ec.value() == EACCES && allow_eacess) {
+      if (ec)
+        ec->clear();
+    } else {
+      path at_ent = std::move(curr_it.__entry_.__p_);
+      __imp_.reset();
+      err.report(m_ec, "attempting recursion into " PATH_CSTR_FMT, at_ent.c_str());
+    }
+  }
+  return false;
+}
+
+_LIBCPP_END_NAMESPACE_FILESYSTEM

third_party/libcxx/fs/error.h

@@ -0,0 +1,232 @@
+//===----------------------------------------------------------------------===////
+//
+// 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 FILESYSTEM_ERROR_H
+#define FILESYSTEM_ERROR_H
+
+#include <__assert>
+#include <__config>
+#include <cerrno>
+#include <cstdarg>
+#include <cstddef>
+#include <cstdint>
+#include <filesystem>
+#include <string>
+#include <system_error>
+#include <utility> // __libcpp_unreachable
+
+#include "format_string.h"
+
+#if defined(_LIBCPP_WIN32API)
+#  define WIN32_LEAN_AND_MEAN
+#  define NOMINMAX
+#  include <windows.h> // ERROR_* macros
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+
+namespace detail {
+
+#if defined(_LIBCPP_WIN32API)
+
+inline errc __win_err_to_errc(int err) {
+  constexpr struct {
+    DWORD win;
+    errc errc;
+  } win_error_mapping[] = {
+      {ERROR_ACCESS_DENIED, errc::permission_denied},
+      {ERROR_ALREADY_EXISTS, errc::file_exists},
+      {ERROR_BAD_NETPATH, errc::no_such_file_or_directory},
+      {ERROR_BAD_PATHNAME, errc::no_such_file_or_directory},
+      {ERROR_BAD_UNIT, errc::no_such_device},
+      {ERROR_BROKEN_PIPE, errc::broken_pipe},
+      {ERROR_BUFFER_OVERFLOW, errc::filename_too_long},
+      {ERROR_BUSY, errc::device_or_resource_busy},
+      {ERROR_BUSY_DRIVE, errc::device_or_resource_busy},
+      {ERROR_CANNOT_MAKE, errc::permission_denied},
+      {ERROR_CANTOPEN, errc::io_error},
+      {ERROR_CANTREAD, errc::io_error},
+      {ERROR_CANTWRITE, errc::io_error},
+      {ERROR_CURRENT_DIRECTORY, errc::permission_denied},
+      {ERROR_DEV_NOT_EXIST, errc::no_such_device},
+      {ERROR_DEVICE_IN_USE, errc::device_or_resource_busy},
+      {ERROR_DIR_NOT_EMPTY, errc::directory_not_empty},
+      {ERROR_DIRECTORY, errc::invalid_argument},
+      {ERROR_DISK_FULL, errc::no_space_on_device},
+      {ERROR_FILE_EXISTS, errc::file_exists},
+      {ERROR_FILE_NOT_FOUND, errc::no_such_file_or_directory},
+      {ERROR_HANDLE_DISK_FULL, errc::no_space_on_device},
+      {ERROR_INVALID_ACCESS, errc::permission_denied},
+      {ERROR_INVALID_DRIVE, errc::no_such_device},
+      {ERROR_INVALID_FUNCTION, errc::function_not_supported},
+      {ERROR_INVALID_HANDLE, errc::invalid_argument},
+      {ERROR_INVALID_NAME, errc::no_such_file_or_directory},
+      {ERROR_INVALID_PARAMETER, errc::invalid_argument},
+      {ERROR_LOCK_VIOLATION, errc::no_lock_available},
+      {ERROR_LOCKED, errc::no_lock_available},
+      {ERROR_NEGATIVE_SEEK, errc::invalid_argument},
+      {ERROR_NOACCESS, errc::permission_denied},
+      {ERROR_NOT_ENOUGH_MEMORY, errc::not_enough_memory},
+      {ERROR_NOT_READY, errc::resource_unavailable_try_again},
+      {ERROR_NOT_SAME_DEVICE, errc::cross_device_link},
+      {ERROR_NOT_SUPPORTED, errc::not_supported},
+      {ERROR_OPEN_FAILED, errc::io_error},
+      {ERROR_OPEN_FILES, errc::device_or_resource_busy},
+      {ERROR_OPERATION_ABORTED, errc::operation_canceled},
+      {ERROR_OUTOFMEMORY, errc::not_enough_memory},
+      {ERROR_PATH_NOT_FOUND, errc::no_such_file_or_directory},
+      {ERROR_READ_FAULT, errc::io_error},
+      {ERROR_REPARSE_TAG_INVALID, errc::invalid_argument},
+      {ERROR_RETRY, errc::resource_unavailable_try_again},
+      {ERROR_SEEK, errc::io_error},
+      {ERROR_SHARING_VIOLATION, errc::permission_denied},
+      {ERROR_TOO_MANY_OPEN_FILES, errc::too_many_files_open},
+      {ERROR_WRITE_FAULT, errc::io_error},
+      {ERROR_WRITE_PROTECT, errc::permission_denied},
+  };
+
+  for (const auto& pair : win_error_mapping)
+    if (pair.win == static_cast<DWORD>(err))
+      return pair.errc;
+  return errc::invalid_argument;
+}
+
+#endif // _LIBCPP_WIN32API
+
+inline error_code capture_errno() {
+  _LIBCPP_ASSERT_INTERNAL(errno != 0, "Expected errno to be non-zero");
+  return error_code(errno, generic_category());
+}
+
+#if defined(_LIBCPP_WIN32API)
+inline error_code make_windows_error(int err) { return make_error_code(__win_err_to_errc(err)); }
+#endif
+
+template <class T>
+T error_value();
+template <>
+inline constexpr void error_value<void>() {}
+template <>
+inline bool error_value<bool>() {
+  return false;
+}
+#if __SIZEOF_SIZE_T__ != __SIZEOF_LONG_LONG__
+template <>
+inline size_t error_value<size_t>() {
+  return size_t(-1);
+}
+#endif
+template <>
+inline uintmax_t error_value<uintmax_t>() {
+  return uintmax_t(-1);
+}
+template <>
+inline constexpr file_time_type error_value<file_time_type>() {
+  return file_time_type::min();
+}
+template <>
+inline path error_value<path>() {
+  return {};
+}
+
+template <class T>
+struct ErrorHandler {
+  const char* func_name_;
+  error_code* ec_ = nullptr;
+  const path* p1_ = nullptr;
+  const path* p2_ = nullptr;
+
+  ErrorHandler(const char* fname, error_code* ec, const path* p1 = nullptr, const path* p2 = nullptr)
+      : func_name_(fname), ec_(ec), p1_(p1), p2_(p2) {
+    if (ec_)
+      ec_->clear();
+  }
+
+  T report(const error_code& ec) const {
+    if (ec_) {
+      *ec_ = ec;
+      return error_value<T>();
+    }
+    string what = string("in ") + func_name_;
+    switch (bool(p1_) + bool(p2_)) {
+    case 0:
+      __throw_filesystem_error(what, ec);
+    case 1:
+      __throw_filesystem_error(what, *p1_, ec);
+    case 2:
+      __throw_filesystem_error(what, *p1_, *p2_, ec);
+    }
+    __libcpp_unreachable();
+  }
+
+  _LIBCPP_ATTRIBUTE_FORMAT(__printf__, 3, 0)
+  void report_impl(const error_code& ec, const char* msg, va_list ap) const {
+    if (ec_) {
+      *ec_ = ec;
+      return;
+    }
+    string what = string("in ") + func_name_ + ": " + detail::vformat_string(msg, ap);
+    switch (bool(p1_) + bool(p2_)) {
+    case 0:
+      __throw_filesystem_error(what, ec);
+    case 1:
+      __throw_filesystem_error(what, *p1_, ec);
+    case 2:
+      __throw_filesystem_error(what, *p1_, *p2_, ec);
+    }
+    __libcpp_unreachable();
+  }
+
+  _LIBCPP_ATTRIBUTE_FORMAT(__printf__, 3, 4)
+  T report(const error_code& ec, const char* msg, ...) const {
+    va_list ap;
+    va_start(ap, msg);
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+    try {
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
+      report_impl(ec, msg, ap);
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+    } catch (...) {
+      va_end(ap);
+      throw;
+    }
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
+    va_end(ap);
+    return error_value<T>();
+  }
+
+  T report(errc const& err) const { return report(make_error_code(err)); }
+
+  _LIBCPP_ATTRIBUTE_FORMAT(__printf__, 3, 4)
+  T report(errc const& err, const char* msg, ...) const {
+    va_list ap;
+    va_start(ap, msg);
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+    try {
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
+      report_impl(make_error_code(err), msg, ap);
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+    } catch (...) {
+      va_end(ap);
+      throw;
+    }
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
+    va_end(ap);
+    return error_value<T>();
+  }
+
+private:
+  ErrorHandler(ErrorHandler const&)            = delete;
+  ErrorHandler& operator=(ErrorHandler const&) = delete;
+};
+
+} // end namespace detail
+
+_LIBCPP_END_NAMESPACE_FILESYSTEM
+
+#endif // FILESYSTEM_ERROR_H

third_party/libcxx/fs/file_descriptor.h

@@ -0,0 +1,291 @@
+//===----------------------------------------------------------------------===////
+//
+// 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 FILESYSTEM_FILE_DESCRIPTOR_H
+#define FILESYSTEM_FILE_DESCRIPTOR_H
+
+#include <__config>
+#include <cstdint>
+#include <filesystem>
+#include <string_view>
+#include <system_error>
+#include <utility>
+
+#include "error.h"
+#include "posix_compat.h"
+#include "time_utils.h"
+
+#if defined(_LIBCPP_WIN32API)
+#  define WIN32_LEAN_AND_MEAN
+#  define NOMINMAX
+#  include <windows.h>
+#else
+#  include <dirent.h> // for DIR & friends
+#  include <fcntl.h>  // values for fchmodat
+#  include <sys/stat.h>
+#  include <sys/statvfs.h>
+#  include <unistd.h>
+#endif // defined(_LIBCPP_WIN32API)
+
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+
+namespace detail {
+
+#if !defined(_LIBCPP_WIN32API)
+
+#  if defined(DT_BLK)
+template <class DirEntT, class = decltype(DirEntT::d_type)>
+file_type get_file_type(DirEntT* ent, int) {
+  switch (ent->d_type) {
+  case DT_BLK:
+    return file_type::block;
+  case DT_CHR:
+    return file_type::character;
+  case DT_DIR:
+    return file_type::directory;
+  case DT_FIFO:
+    return file_type::fifo;
+  case DT_LNK:
+    return file_type::symlink;
+  case DT_REG:
+    return file_type::regular;
+  case DT_SOCK:
+    return file_type::socket;
+  // Unlike in lstat, hitting "unknown" here simply means that the underlying
+  // filesystem doesn't support d_type. Report is as 'none' so we correctly
+  // set the cache to empty.
+  case DT_UNKNOWN:
+    break;
+  }
+  return file_type::none;
+}
+#  endif // defined(DT_BLK)
+
+template <class DirEntT>
+file_type get_file_type(DirEntT*, long) {
+  return file_type::none;
+}
+
+inline pair<string_view, file_type> posix_readdir(DIR* dir_stream, error_code& ec) {
+  struct dirent* dir_entry_ptr = nullptr;
+  errno                        = 0; // zero errno in order to detect errors
+  ec.clear();
+  if ((dir_entry_ptr = ::readdir(dir_stream)) == nullptr) {
+    if (errno)
+      ec = capture_errno();
+    return {};
+  } else {
+    return {dir_entry_ptr->d_name, get_file_type(dir_entry_ptr, 0)};
+  }
+}
+
+#else // _LIBCPP_WIN32API
+
+inline file_type get_file_type(const WIN32_FIND_DATAW& data) {
+  if (data.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT && data.dwReserved0 == IO_REPARSE_TAG_SYMLINK)
+    return file_type::symlink;
+  if (data.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
+    return file_type::directory;
+  return file_type::regular;
+}
+inline uintmax_t get_file_size(const WIN32_FIND_DATAW& data) {
+  return (static_cast<uint64_t>(data.nFileSizeHigh) << 32) + data.nFileSizeLow;
+}
+inline file_time_type get_write_time(const WIN32_FIND_DATAW& data) {
+  ULARGE_INTEGER tmp;
+  const FILETIME& time = data.ftLastWriteTime;
+  tmp.u.LowPart        = time.dwLowDateTime;
+  tmp.u.HighPart       = time.dwHighDateTime;
+  return file_time_type(file_time_type::duration(tmp.QuadPart));
+}
+
+#endif // !_LIBCPP_WIN32API
+
+//                       POSIX HELPERS
+
+using value_type  = path::value_type;
+using string_type = path::string_type;
+
+struct FileDescriptor {
+  const path& name;
+  int fd = -1;
+  StatT m_stat;
+  file_status m_status;
+
+  template <class... Args>
+  static FileDescriptor create(const path* p, error_code& ec, Args... args) {
+    ec.clear();
+    int fd;
+#ifdef _LIBCPP_WIN32API
+    // TODO: most of the filesystem implementation uses native Win32 calls
+    // (mostly via posix_compat.h). However, here we use the C-runtime APIs to
+    // open a file, because we subsequently pass the C-runtime fd to
+    // `std::[io]fstream::__open(int fd)` in order to implement copy_file.
+    //
+    // Because we're calling the windows C-runtime, win32 error codes are
+    // translated into C error numbers by the C runtime, and returned in errno,
+    // rather than being accessible directly via GetLastError.
+    //
+    // Ideally copy_file should be calling the Win32 CopyFile2 function, which
+    // works on paths, not open files -- at which point this FileDescriptor type
+    // will no longer be needed on windows at all.
+    fd = ::_wopen(p->c_str(), args...);
+#else
+    fd = open(p->c_str(), args...);
+#endif
+
+    if (fd == -1) {
+      ec = capture_errno();
+      return FileDescriptor{p};
+    }
+    return FileDescriptor(p, fd);
+  }
+
+  template <class... Args>
+  static FileDescriptor create_with_status(const path* p, error_code& ec, Args... args) {
+    FileDescriptor fd = create(p, ec, args...);
+    if (!ec)
+      fd.refresh_status(ec);
+
+    return fd;
+  }
+
+  file_status get_status() const { return m_status; }
+  StatT const& get_stat() const { return m_stat; }
+
+  bool status_known() const { return filesystem::status_known(m_status); }
+
+  file_status refresh_status(error_code& ec);
+
+  void close() noexcept {
+    if (fd != -1) {
+#ifdef _LIBCPP_WIN32API
+      ::_close(fd);
+#else
+      ::close(fd);
+#endif
+      // FIXME: shouldn't this return an error_code?
+    }
+    fd = -1;
+  }
+
+  FileDescriptor(FileDescriptor&& other)
+      : name(other.name), fd(other.fd), m_stat(other.m_stat), m_status(other.m_status) {
+    other.fd       = -1;
+    other.m_status = file_status{};
+  }
+
+  ~FileDescriptor() { close(); }
+
+  FileDescriptor(FileDescriptor const&)            = delete;
+  FileDescriptor& operator=(FileDescriptor const&) = delete;
+
+private:
+  explicit FileDescriptor(const path* p, int descriptor = -1) : name(*p), fd(descriptor) {}
+};
+
+inline perms posix_get_perms(const StatT& st) noexcept { return static_cast<perms>(st.st_mode) & perms::mask; }
+
+inline file_status create_file_status(error_code& m_ec, path const& p, const StatT& path_stat, error_code* ec) {
+  if (ec)
+    *ec = m_ec;
+  if (m_ec && (m_ec.value() == ENOENT || m_ec.value() == ENOTDIR)) {
+    return file_status(file_type::not_found);
+  } else if (m_ec) {
+    ErrorHandler<void> err("posix_stat", ec, &p);
+    err.report(m_ec, "failed to determine attributes for the specified path");
+    return file_status(file_type::none);
+  }
+  // else
+
+  file_status fs_tmp;
+  auto const mode = path_stat.st_mode;
+  if (S_ISLNK(mode))
+    fs_tmp.type(file_type::symlink);
+  else if (S_ISREG(mode))
+    fs_tmp.type(file_type::regular);
+  else if (S_ISDIR(mode))
+    fs_tmp.type(file_type::directory);
+  else if (S_ISBLK(mode))
+    fs_tmp.type(file_type::block);
+  else if (S_ISCHR(mode))
+    fs_tmp.type(file_type::character);
+  else if (S_ISFIFO(mode))
+    fs_tmp.type(file_type::fifo);
+  else if (S_ISSOCK(mode))
+    fs_tmp.type(file_type::socket);
+  else
+    fs_tmp.type(file_type::unknown);
+
+  fs_tmp.permissions(detail::posix_get_perms(path_stat));
+  return fs_tmp;
+}
+
+inline file_status posix_stat(path const& p, StatT& path_stat, error_code* ec) {
+  error_code m_ec;
+  if (detail::stat(p.c_str(), &path_stat) == -1)
+    m_ec = detail::capture_errno();
+  return create_file_status(m_ec, p, path_stat, ec);
+}
+
+inline file_status posix_stat(path const& p, error_code* ec) {
+  StatT path_stat;
+  return posix_stat(p, path_stat, ec);
+}
+
+inline file_status posix_lstat(path const& p, StatT& path_stat, error_code* ec) {
+  error_code m_ec;
+  if (detail::lstat(p.c_str(), &path_stat) == -1)
+    m_ec = detail::capture_errno();
+  return create_file_status(m_ec, p, path_stat, ec);
+}
+
+inline file_status posix_lstat(path const& p, error_code* ec) {
+  StatT path_stat;
+  return posix_lstat(p, path_stat, ec);
+}
+
+// http://pubs.opengroup.org/onlinepubs/9699919799/functions/ftruncate.html
+inline bool posix_ftruncate(const FileDescriptor& fd, off_t to_size, error_code& ec) {
+  if (detail::ftruncate(fd.fd, to_size) == -1) {
+    ec = capture_errno();
+    return true;
+  }
+  ec.clear();
+  return false;
+}
+
+inline bool posix_fchmod(const FileDescriptor& fd, const StatT& st, error_code& ec) {
+  if (detail::fchmod(fd.fd, st.st_mode) == -1) {
+    ec = capture_errno();
+    return true;
+  }
+  ec.clear();
+  return false;
+}
+
+inline bool stat_equivalent(const StatT& st1, const StatT& st2) {
+  return (st1.st_dev == st2.st_dev && st1.st_ino == st2.st_ino);
+}
+
+inline file_status FileDescriptor::refresh_status(error_code& ec) {
+  // FD must be open and good.
+  m_status = file_status{};
+  m_stat   = {};
+  error_code m_ec;
+  if (detail::fstat(fd, &m_stat) == -1)
+    m_ec = capture_errno();
+  m_status = create_file_status(m_ec, name, m_stat, &ec);
+  return m_status;
+}
+
+} // end namespace detail
+
+_LIBCPP_END_NAMESPACE_FILESYSTEM
+
+#endif // FILESYSTEM_FILE_DESCRIPTOR_H

third_party/libcxx/fs/filesystem_clock.cpp

@@ -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
+//
+//===----------------------------------------------------------------------===//
+
+#include <__config>
+#include <chrono>
+#include <filesystem>
+#include <time.h>
+
+#if defined(_LIBCPP_WIN32API)
+#  include "time_utils.h"
+#endif
+
+#if defined(_LIBCPP_WIN32API)
+#  define WIN32_LEAN_AND_MEAN
+#  define NOMINMAX
+#  include <windows.h>
+#endif
+
+#if __has_include(<unistd.h>)
+#  include <unistd.h> // _POSIX_TIMERS
+#endif
+
+#if __has_include(<sys/time.h>)
+#  include <sys/time.h> // for gettimeofday and timeval
+#endif
+
+#if defined(__APPLE__) || defined(__gnu_hurd__) || (defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0)
+#  define _LIBCPP_HAS_CLOCK_GETTIME
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+
+const bool _FilesystemClock::is_steady;
+
+_FilesystemClock::time_point _FilesystemClock::now() noexcept {
+  typedef chrono::duration<rep> __secs;
+#if defined(_LIBCPP_WIN32API)
+  typedef chrono::duration<rep, nano> __nsecs;
+  FILETIME time;
+  GetSystemTimeAsFileTime(&time);
+  detail::TimeSpec tp = detail::filetime_to_timespec(time);
+  return time_point(__secs(tp.tv_sec) + chrono::duration_cast<duration>(__nsecs(tp.tv_nsec)));
+#elif defined(_LIBCPP_HAS_CLOCK_GETTIME)
+  typedef chrono::duration<rep, nano> __nsecs;
+  struct timespec tp;
+  if (0 != clock_gettime(CLOCK_REALTIME, &tp))
+    __throw_system_error(errno, "clock_gettime(CLOCK_REALTIME) failed");
+  return time_point(__secs(tp.tv_sec) + chrono::duration_cast<duration>(__nsecs(tp.tv_nsec)));
+#else
+  typedef chrono::duration<rep, micro> __microsecs;
+  timeval tv;
+  gettimeofday(&tv, 0);
+  return time_point(__secs(tv.tv_sec) + __microsecs(tv.tv_usec));
+#endif
+}
+
+_LIBCPP_END_NAMESPACE_FILESYSTEM

third_party/libcxx/fs/filesystem_error.cpp

@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 <__config>
+#include <__utility/unreachable.h>
+#include <filesystem>
+#include <system_error>
+
+#include "format_string.h"
+
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+
+filesystem_error::~filesystem_error() {}
+
+void filesystem_error::__create_what(int __num_paths) {
+  const char* derived_what = system_error::what();
+  __storage_->__what_      = [&]() -> string {
+    switch (__num_paths) {
+    case 0:
+      return detail::format_string("filesystem error: %s", derived_what);
+    case 1:
+      return detail::format_string("filesystem error: %s [" PATH_CSTR_FMT "]", derived_what, path1().c_str());
+    case 2:
+      return detail::format_string(
+          "filesystem error: %s [" PATH_CSTR_FMT "] [" PATH_CSTR_FMT "]",
+          derived_what,
+          path1().c_str(),
+          path2().c_str());
+    }
+    __libcpp_unreachable();
+  }();
+}
+
+_LIBCPP_END_NAMESPACE_FILESYSTEM

third_party/libcxx/fs/format_string.h

@@ -0,0 +1,77 @@
+//===----------------------------------------------------------------------===////
+//
+// 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 FILESYSTEM_FORMAT_STRING_H
+#define FILESYSTEM_FORMAT_STRING_H
+
+#include <__assert>
+#include <__config>
+#include <array>
+#include <cstdarg>
+#include <cstddef>
+#include <cstdio>
+#include <string>
+
+#if defined(_LIBCPP_WIN32API)
+#  define PATHSTR(x) (L##x)
+#  define PATH_CSTR_FMT "\"%ls\""
+#else
+#  define PATHSTR(x) (x)
+#  define PATH_CSTR_FMT "\"%s\""
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+
+namespace detail {
+
+inline _LIBCPP_ATTRIBUTE_FORMAT(__printf__, 1, 0) string vformat_string(const char* msg, va_list ap) {
+  array<char, 256> buf;
+
+  va_list apcopy;
+  va_copy(apcopy, ap);
+  int ret = ::vsnprintf(buf.data(), buf.size(), msg, apcopy);
+  va_end(apcopy);
+
+  string result;
+  if (static_cast<size_t>(ret) < buf.size()) {
+    result.assign(buf.data(), static_cast<size_t>(ret));
+  } else {
+    // we did not provide a long enough buffer on our first attempt. The
+    // return value is the number of bytes (excluding the null byte) that are
+    // needed for formatting.
+    size_t size_with_null = static_cast<size_t>(ret) + 1;
+    result.__resize_default_init(size_with_null - 1);
+    ret = ::vsnprintf(&result[0], size_with_null, msg, ap);
+    _LIBCPP_ASSERT_INTERNAL(static_cast<size_t>(ret) == (size_with_null - 1), "TODO");
+  }
+  return result;
+}
+
+inline _LIBCPP_ATTRIBUTE_FORMAT(__printf__, 1, 2) string format_string(const char* msg, ...) {
+  string ret;
+  va_list ap;
+  va_start(ap, msg);
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+  try {
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
+    ret = detail::vformat_string(msg, ap);
+#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+  } catch (...) {
+    va_end(ap);
+    throw;
+  }
+#endif // _LIBCPP_HAS_NO_EXCEPTIONS
+  va_end(ap);
+  return ret;
+}
+
+} // end namespace detail
+
+_LIBCPP_END_NAMESPACE_FILESYSTEM
+
+#endif // FILESYSTEM_FORMAT_STRING_H

third_party/libcxx/fs/int128_builtins.cpp

@@ -0,0 +1,54 @@
+/*===-- int128_builtins.cpp - Implement __muloti4 --------------------------===
+ *
+ * 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
+ *
+ * ===----------------------------------------------------------------------===
+ *
+ * This file implements __muloti4, and is stolen from the compiler_rt library.
+ *
+ * FIXME: we steal and re-compile it into filesystem, which uses __int128_t,
+ * and requires this builtin when sanitized. See llvm.org/PR30643
+ *
+ * ===----------------------------------------------------------------------===
+ */
+#include <__config>
+#include <climits>
+
+#if !defined(_LIBCPP_HAS_NO_INT128)
+
+extern "C" __attribute__((no_sanitize("undefined"))) _LIBCPP_EXPORTED_FROM_ABI __int128_t
+__muloti4(__int128_t a, __int128_t b, int* overflow) {
+  const int N          = (int)(sizeof(__int128_t) * CHAR_BIT);
+  const __int128_t MIN = (__int128_t)1 << (N - 1);
+  const __int128_t MAX = ~MIN;
+  *overflow            = 0;
+  __int128_t result    = a * b;
+  if (a == MIN) {
+    if (b != 0 && b != 1)
+      *overflow = 1;
+    return result;
+  }
+  if (b == MIN) {
+    if (a != 0 && a != 1)
+      *overflow = 1;
+    return result;
+  }
+  __int128_t sa    = a >> (N - 1);
+  __int128_t abs_a = (a ^ sa) - sa;
+  __int128_t sb    = b >> (N - 1);
+  __int128_t abs_b = (b ^ sb) - sb;
+  if (abs_a < 2 || abs_b < 2)
+    return result;
+  if (sa == sb) {
+    if (abs_a > MAX / abs_b)
+      *overflow = 1;
+  } else {
+    if (abs_a > MIN / -abs_b)
+      *overflow = 1;
+  }
+  return result;
+}
+
+#endif

third_party/libcxx/fs/operations.cpp

@@ -0,0 +1,965 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 <__assert>
+#include <__config>
+#include <__utility/unreachable.h>
+#include <array>
+#include <climits>
+#include <cstdlib>
+#include <filesystem>
+#include <iterator>
+#include <string_view>
+#include <type_traits>
+#include <vector>
+
+#include "error.h"
+#include "file_descriptor.h"
+#include "path_parser.h"
+#include "posix_compat.h"
+#include "time_utils.h"
+
+#if defined(_LIBCPP_WIN32API)
+#  define WIN32_LEAN_AND_MEAN
+#  define NOMINMAX
+#  include <windows.h>
+#else
+#  include <dirent.h>
+#  include <sys/stat.h>
+#  include <sys/statvfs.h>
+#  include <unistd.h>
+#endif
+#include <fcntl.h> /* values for fchmodat */
+#include <time.h>
+
+#if __has_include(<sys/sendfile.h>)
+#  include <sys/sendfile.h>
+#  define _LIBCPP_FILESYSTEM_USE_SENDFILE
+#elif defined(__APPLE__) || __has_include(<copyfile.h>)
+#  include <copyfile.h>
+#  define _LIBCPP_FILESYSTEM_USE_COPYFILE
+#else
+#  include <fstream>
+#  define _LIBCPP_FILESYSTEM_USE_FSTREAM
+#endif
+
+#if defined(__ELF__) && defined(_LIBCPP_LINK_RT_LIB)
+#  pragma comment(lib, "rt")
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+
+using detail::capture_errno;
+using detail::ErrorHandler;
+using detail::StatT;
+using detail::TimeSpec;
+using parser::createView;
+using parser::PathParser;
+using parser::string_view_t;
+
+static path __do_absolute(const path& p, path* cwd, error_code* ec) {
+  if (ec)
+    ec->clear();
+  if (p.is_absolute())
+    return p;
+  *cwd = __current_path(ec);
+  if (ec && *ec)
+    return {};
+  return (*cwd) / p;
+}
+
+path __absolute(const path& p, error_code* ec) {
+  path cwd;
+  return __do_absolute(p, &cwd, ec);
+}
+
+path __canonical(path const& orig_p, error_code* ec) {
+  path cwd;
+  ErrorHandler<path> err("canonical", ec, &orig_p, &cwd);
+
+  path p = __do_absolute(orig_p, &cwd, ec);
+#if (defined(_POSIX_VERSION) && _POSIX_VERSION >= 200112) || defined(_LIBCPP_WIN32API)
+  std::unique_ptr<path::value_type, decltype(&::free)> hold(detail::realpath(p.c_str(), nullptr), &::free);
+  if (hold.get() == nullptr)
+    return err.report(capture_errno());
+  return {hold.get()};
+#else
+#  if defined(__MVS__) && !defined(PATH_MAX)
+  path::value_type buff[_XOPEN_PATH_MAX + 1];
+#  else
+  path::value_type buff[PATH_MAX + 1];
+#  endif
+  path::value_type* ret;
+  if ((ret = detail::realpath(p.c_str(), buff)) == nullptr)
+    return err.report(capture_errno());
+  return {ret};
+#endif
+}
+
+void __copy(const path& from, const path& to, copy_options options, error_code* ec) {
+  ErrorHandler<void> err("copy", ec, &from, &to);
+
+  const bool sym_status = bool(options & (copy_options::create_symlinks | copy_options::skip_symlinks));
+
+  const bool sym_status2 = bool(options & copy_options::copy_symlinks);
+
+  error_code m_ec1;
+  StatT f_st;
+  const file_status f =
+      sym_status || sym_status2 ? detail::posix_lstat(from, f_st, &m_ec1) : detail::posix_stat(from, f_st, &m_ec1);
+  if (m_ec1)
+    return err.report(m_ec1);
+
+  StatT t_st;
+  const file_status t = sym_status ? detail::posix_lstat(to, t_st, &m_ec1) : detail::posix_stat(to, t_st, &m_ec1);
+
+  if (not status_known(t))
+    return err.report(m_ec1);
+
+  if (!exists(f) || is_other(f) || is_other(t) || (is_directory(f) && is_regular_file(t)) ||
+      (exists(t) && detail::stat_equivalent(f_st, t_st))) {
+    return err.report(errc::function_not_supported);
+  }
+
+  if (is_symlink(f)) {
+    if (bool(copy_options::skip_symlinks & options)) {
+      // do nothing
+    } else if (not exists(t)) {
+      __copy_symlink(from, to, ec);
+    } else {
+      return err.report(errc::file_exists);
+    }
+    return;
+  } else if (is_regular_file(f)) {
+    if (bool(copy_options::directories_only & options)) {
+      // do nothing
+    } else if (bool(copy_options::create_symlinks & options)) {
+      __create_symlink(from, to, ec);
+    } else if (bool(copy_options::create_hard_links & options)) {
+      __create_hard_link(from, to, ec);
+    } else if (is_directory(t)) {
+      __copy_file(from, to / from.filename(), options, ec);
+    } else {
+      __copy_file(from, to, options, ec);
+    }
+    return;
+  } else if (is_directory(f) && bool(copy_options::create_symlinks & options)) {
+    return err.report(errc::is_a_directory);
+  } else if (is_directory(f) && (bool(copy_options::recursive & options) || copy_options::none == options)) {
+    if (!exists(t)) {
+      // create directory to with attributes from 'from'.
+      __create_directory(to, from, ec);
+      if (ec && *ec) {
+        return;
+      }
+    }
+    directory_iterator it = ec ? directory_iterator(from, *ec) : directory_iterator(from);
+    if (ec && *ec) {
+      return;
+    }
+    error_code m_ec2;
+    for (; !m_ec2 && it != directory_iterator(); it.increment(m_ec2)) {
+      __copy(it->path(), to / it->path().filename(), options | copy_options::__in_recursive_copy, ec);
+      if (ec && *ec) {
+        return;
+      }
+    }
+    if (m_ec2) {
+      return err.report(m_ec2);
+    }
+  }
+}
+
+namespace detail {
+namespace {
+
+#if defined(_LIBCPP_FILESYSTEM_USE_SENDFILE)
+bool copy_file_impl(FileDescriptor& read_fd, FileDescriptor& write_fd, error_code& ec) {
+  size_t count = read_fd.get_stat().st_size;
+  do {
+    ssize_t res;
+    if ((res = ::sendfile(write_fd.fd, read_fd.fd, nullptr, count)) == -1) {
+      ec = capture_errno();
+      return false;
+    }
+    count -= res;
+  } while (count > 0);
+
+  ec.clear();
+
+  return true;
+}
+#elif defined(_LIBCPP_FILESYSTEM_USE_COPYFILE)
+bool copy_file_impl(FileDescriptor& read_fd, FileDescriptor& write_fd, error_code& ec) {
+  struct CopyFileState {
+    copyfile_state_t state;
+    CopyFileState() { state = copyfile_state_alloc(); }
+    ~CopyFileState() { copyfile_state_free(state); }
+
+  private:
+    CopyFileState(CopyFileState const&)            = delete;
+    CopyFileState& operator=(CopyFileState const&) = delete;
+  };
+
+  CopyFileState cfs;
+  if (fcopyfile(read_fd.fd, write_fd.fd, cfs.state, COPYFILE_DATA) < 0) {
+    ec = capture_errno();
+    return false;
+  }
+
+  ec.clear();
+  return true;
+}
+#elif defined(_LIBCPP_FILESYSTEM_USE_FSTREAM)
+bool copy_file_impl(FileDescriptor& read_fd, FileDescriptor& write_fd, error_code& ec) {
+  ifstream in;
+  in.__open(read_fd.fd, ios::binary);
+  if (!in.is_open()) {
+    // This assumes that __open didn't reset the error code.
+    ec = capture_errno();
+    return false;
+  }
+  read_fd.fd = -1;
+  ofstream out;
+  out.__open(write_fd.fd, ios::binary);
+  if (!out.is_open()) {
+    ec = capture_errno();
+    return false;
+  }
+  write_fd.fd = -1;
+
+  if (in.good() && out.good()) {
+    using InIt  = istreambuf_iterator<char>;
+    using OutIt = ostreambuf_iterator<char>;
+    InIt bin(in);
+    InIt ein;
+    OutIt bout(out);
+    copy(bin, ein, bout);
+  }
+  if (out.fail() || in.fail()) {
+    ec = make_error_code(errc::io_error);
+    return false;
+  }
+
+  ec.clear();
+  return true;
+}
+#else
+#  error "Unknown implementation for copy_file_impl"
+#endif // copy_file_impl implementation
+
+} // end anonymous namespace
+} // end namespace detail
+
+bool __copy_file(const path& from, const path& to, copy_options options, error_code* ec) {
+  using detail::FileDescriptor;
+  ErrorHandler<bool> err("copy_file", ec, &to, &from);
+
+  error_code m_ec;
+  FileDescriptor from_fd = FileDescriptor::create_with_status(&from, m_ec, O_RDONLY | O_NONBLOCK | O_BINARY);
+  if (m_ec)
+    return err.report(m_ec);
+
+  auto from_st           = from_fd.get_status();
+  StatT const& from_stat = from_fd.get_stat();
+  if (!is_regular_file(from_st)) {
+    if (not m_ec)
+      m_ec = make_error_code(errc::not_supported);
+    return err.report(m_ec);
+  }
+
+  const bool skip_existing      = bool(copy_options::skip_existing & options);
+  const bool update_existing    = bool(copy_options::update_existing & options);
+  const bool overwrite_existing = bool(copy_options::overwrite_existing & options);
+
+  StatT to_stat_path;
+  file_status to_st = detail::posix_stat(to, to_stat_path, &m_ec);
+  if (!status_known(to_st))
+    return err.report(m_ec);
+
+  const bool to_exists = exists(to_st);
+  if (to_exists && !is_regular_file(to_st))
+    return err.report(errc::not_supported);
+
+  if (to_exists && detail::stat_equivalent(from_stat, to_stat_path))
+    return err.report(errc::file_exists);
+
+  if (to_exists && skip_existing)
+    return false;
+
+  bool ShouldCopy = [&]() {
+    if (to_exists && update_existing) {
+      auto from_time = detail::extract_mtime(from_stat);
+      auto to_time   = detail::extract_mtime(to_stat_path);
+      if (from_time.tv_sec < to_time.tv_sec)
+        return false;
+      if (from_time.tv_sec == to_time.tv_sec && from_time.tv_nsec <= to_time.tv_nsec)
+        return false;
+      return true;
+    }
+    if (!to_exists || overwrite_existing)
+      return true;
+    return err.report(errc::file_exists);
+  }();
+  if (!ShouldCopy)
+    return false;
+
+  // Don't truncate right away. We may not be opening the file we originally
+  // looked at; we'll check this later.
+  int to_open_flags = O_WRONLY | O_BINARY;
+  if (!to_exists)
+    to_open_flags |= O_CREAT;
+  FileDescriptor to_fd = FileDescriptor::create_with_status(&to, m_ec, to_open_flags, from_stat.st_mode);
+  if (m_ec)
+    return err.report(m_ec);
+
+  if (to_exists) {
+    // Check that the file we initially stat'ed is equivalent to the one
+    // we opened.
+    // FIXME: report this better.
+    if (!detail::stat_equivalent(to_stat_path, to_fd.get_stat()))
+      return err.report(errc::bad_file_descriptor);
+
+    // Set the permissions and truncate the file we opened.
+    if (detail::posix_fchmod(to_fd, from_stat, m_ec))
+      return err.report(m_ec);
+    if (detail::posix_ftruncate(to_fd, 0, m_ec))
+      return err.report(m_ec);
+  }
+
+  if (!detail::copy_file_impl(from_fd, to_fd, m_ec)) {
+    // FIXME: Remove the dest file if we failed, and it didn't exist previously.
+    return err.report(m_ec);
+  }
+
+  return true;
+}
+
+void __copy_symlink(const path& existing_symlink, const path& new_symlink, error_code* ec) {
+  const path real_path(__read_symlink(existing_symlink, ec));
+  if (ec && *ec) {
+    return;
+  }
+#if defined(_LIBCPP_WIN32API)
+  error_code local_ec;
+  if (is_directory(real_path, local_ec))
+    __create_directory_symlink(real_path, new_symlink, ec);
+  else
+#endif
+    __create_symlink(real_path, new_symlink, ec);
+}
+
+bool __create_directories(const path& p, error_code* ec) {
+  ErrorHandler<bool> err("create_directories", ec, &p);
+
+  error_code m_ec;
+  auto const st = detail::posix_stat(p, &m_ec);
+  if (!status_known(st))
+    return err.report(m_ec);
+  else if (is_directory(st))
+    return false;
+  else if (exists(st))
+    return err.report(errc::file_exists);
+
+  const path parent = p.parent_path();
+  if (!parent.empty()) {
+    const file_status parent_st = status(parent, m_ec);
+    if (not status_known(parent_st))
+      return err.report(m_ec);
+    if (not exists(parent_st)) {
+      if (parent == p)
+        return err.report(errc::invalid_argument);
+      __create_directories(parent, ec);
+      if (ec && *ec) {
+        return false;
+      }
+    } else if (not is_directory(parent_st))
+      return err.report(errc::not_a_directory);
+  }
+  bool ret = __create_directory(p, &m_ec);
+  if (m_ec)
+    return err.report(m_ec);
+  return ret;
+}
+
+bool __create_directory(const path& p, error_code* ec) {
+  ErrorHandler<bool> err("create_directory", ec, &p);
+
+  if (detail::mkdir(p.c_str(), static_cast<int>(perms::all)) == 0)
+    return true;
+
+  if (errno != EEXIST)
+    return err.report(capture_errno());
+  error_code mec = capture_errno();
+  error_code ignored_ec;
+  const file_status st = status(p, ignored_ec);
+  if (!is_directory(st))
+    return err.report(mec);
+  return false;
+}
+
+bool __create_directory(path const& p, path const& attributes, error_code* ec) {
+  ErrorHandler<bool> err("create_directory", ec, &p, &attributes);
+
+  StatT attr_stat;
+  error_code mec;
+  file_status st = detail::posix_stat(attributes, attr_stat, &mec);
+  if (!status_known(st))
+    return err.report(mec);
+  if (!is_directory(st))
+    return err.report(errc::not_a_directory, "the specified attribute path is invalid");
+
+  if (detail::mkdir(p.c_str(), attr_stat.st_mode) == 0)
+    return true;
+
+  if (errno != EEXIST)
+    return err.report(capture_errno());
+
+  mec = capture_errno();
+  error_code ignored_ec;
+  st = status(p, ignored_ec);
+  if (!is_directory(st))
+    return err.report(mec);
+  return false;
+}
+
+void __create_directory_symlink(path const& from, path const& to, error_code* ec) {
+  ErrorHandler<void> err("create_directory_symlink", ec, &from, &to);
+  if (detail::symlink_dir(from.c_str(), to.c_str()) == -1)
+    return err.report(capture_errno());
+}
+
+void __create_hard_link(const path& from, const path& to, error_code* ec) {
+  ErrorHandler<void> err("create_hard_link", ec, &from, &to);
+  if (detail::link(from.c_str(), to.c_str()) == -1)
+    return err.report(capture_errno());
+}
+
+void __create_symlink(path const& from, path const& to, error_code* ec) {
+  ErrorHandler<void> err("create_symlink", ec, &from, &to);
+  if (detail::symlink_file(from.c_str(), to.c_str()) == -1)
+    return err.report(capture_errno());
+}
+
+path __current_path(error_code* ec) {
+  ErrorHandler<path> err("current_path", ec);
+
+#if defined(_LIBCPP_WIN32API) || defined(__GLIBC__) || defined(__APPLE__)
+  // Common extension outside of POSIX getcwd() spec, without needing to
+  // preallocate a buffer. Also supported by a number of other POSIX libcs.
+  int size              = 0;
+  path::value_type* ptr = nullptr;
+  typedef decltype(&::free) Deleter;
+  Deleter deleter = &::free;
+#else
+  errno     = 0; // Note: POSIX mandates that modifying `errno` is thread-safe.
+  auto size = ::pathconf(".", _PC_PATH_MAX);
+  if (size == -1) {
+    if (errno != 0) {
+      return err.report(capture_errno(), "call to pathconf failed");
+
+      // `pathconf` returns `-1` without an error to indicate no limit.
+    } else {
+#  if defined(__MVS__) && !defined(PATH_MAX)
+      size = _XOPEN_PATH_MAX + 1;
+#  else
+      size = PATH_MAX + 1;
+#  endif
+    }
+  }
+
+  auto buff             = unique_ptr<path::value_type[]>(new path::value_type[size + 1]);
+  path::value_type* ptr = buff.get();
+
+  // Preallocated buffer, don't free the buffer in the second unique_ptr
+  // below.
+  struct Deleter {
+    void operator()(void*) const {}
+  };
+  Deleter deleter;
+#endif
+
+  unique_ptr<path::value_type, Deleter> hold(detail::getcwd(ptr, size), deleter);
+  if (hold.get() == nullptr)
+    return err.report(capture_errno(), "call to getcwd failed");
+
+  return {hold.get()};
+}
+
+void __current_path(const path& p, error_code* ec) {
+  ErrorHandler<void> err("current_path", ec, &p);
+  if (detail::chdir(p.c_str()) == -1)
+    err.report(capture_errno());
+}
+
+bool __equivalent(const path& p1, const path& p2, error_code* ec) {
+  ErrorHandler<bool> err("equivalent", ec, &p1, &p2);
+
+  error_code ec1, ec2;
+  StatT st1 = {}, st2 = {};
+  auto s1 = detail::posix_stat(p1.native(), st1, &ec1);
+  if (!exists(s1))
+    return err.report(errc::not_supported);
+  auto s2 = detail::posix_stat(p2.native(), st2, &ec2);
+  if (!exists(s2))
+    return err.report(errc::not_supported);
+
+  return detail::stat_equivalent(st1, st2);
+}
+
+uintmax_t __file_size(const path& p, error_code* ec) {
+  ErrorHandler<uintmax_t> err("file_size", ec, &p);
+
+  error_code m_ec;
+  StatT st;
+  file_status fst = detail::posix_stat(p, st, &m_ec);
+  if (!exists(fst) || !is_regular_file(fst)) {
+    errc error_kind = is_directory(fst) ? errc::is_a_directory : errc::not_supported;
+    if (!m_ec)
+      m_ec = make_error_code(error_kind);
+    return err.report(m_ec);
+  }
+  // is_regular_file(p) == true
+  return static_cast<uintmax_t>(st.st_size);
+}
+
+uintmax_t __hard_link_count(const path& p, error_code* ec) {
+  ErrorHandler<uintmax_t> err("hard_link_count", ec, &p);
+
+  error_code m_ec;
+  StatT st;
+  detail::posix_stat(p, st, &m_ec);
+  if (m_ec)
+    return err.report(m_ec);
+  return static_cast<uintmax_t>(st.st_nlink);
+}
+
+bool __fs_is_empty(const path& p, error_code* ec) {
+  ErrorHandler<bool> err("is_empty", ec, &p);
+
+  error_code m_ec;
+  StatT pst;
+  auto st = detail::posix_stat(p, pst, &m_ec);
+  if (m_ec)
+    return err.report(m_ec);
+  else if (!is_directory(st) && !is_regular_file(st))
+    return err.report(errc::not_supported);
+  else if (is_directory(st)) {
+    auto it = ec ? directory_iterator(p, *ec) : directory_iterator(p);
+    if (ec && *ec)
+      return false;
+    return it == directory_iterator{};
+  } else if (is_regular_file(st))
+    return static_cast<uintmax_t>(pst.st_size) == 0;
+
+  __libcpp_unreachable();
+}
+
+file_time_type __last_write_time(const path& p, error_code* ec) {
+  using namespace chrono;
+  ErrorHandler<file_time_type> err("last_write_time", ec, &p);
+
+  error_code m_ec;
+  StatT st;
+  detail::posix_stat(p, st, &m_ec);
+  if (m_ec)
+    return err.report(m_ec);
+  return detail::__extract_last_write_time(p, st, ec);
+}
+
+void __last_write_time(const path& p, file_time_type new_time, error_code* ec) {
+  using detail::fs_time;
+  ErrorHandler<void> err("last_write_time", ec, &p);
+
+#if defined(_LIBCPP_WIN32API)
+  TimeSpec ts;
+  if (!fs_time::convert_to_timespec(ts, new_time))
+    return err.report(errc::value_too_large);
+  detail::WinHandle h(p.c_str(), FILE_WRITE_ATTRIBUTES, 0);
+  if (!h)
+    return err.report(detail::make_windows_error(GetLastError()));
+  FILETIME last_write = timespec_to_filetime(ts);
+  if (!SetFileTime(h, nullptr, nullptr, &last_write))
+    return err.report(detail::make_windows_error(GetLastError()));
+#else
+  error_code m_ec;
+  array<TimeSpec, 2> tbuf;
+#  if !defined(_LIBCPP_USE_UTIMENSAT)
+  // This implementation has a race condition between determining the
+  // last access time and attempting to set it to the same value using
+  // ::utimes
+  StatT st;
+  file_status fst = detail::posix_stat(p, st, &m_ec);
+  if (m_ec)
+    return err.report(m_ec);
+  tbuf[0] = detail::extract_atime(st);
+#  else
+  tbuf[0].tv_sec  = 0;
+  tbuf[0].tv_nsec = UTIME_OMIT;
+#  endif
+  if (!fs_time::convert_to_timespec(tbuf[1], new_time))
+    return err.report(errc::value_too_large);
+
+  detail::set_file_times(p, tbuf, m_ec);
+  if (m_ec)
+    return err.report(m_ec);
+#endif
+}
+
+void __permissions(const path& p, perms prms, perm_options opts, error_code* ec) {
+  ErrorHandler<void> err("permissions", ec, &p);
+
+  auto has_opt                = [&](perm_options o) { return bool(o & opts); };
+  const bool resolve_symlinks = !has_opt(perm_options::nofollow);
+  const bool add_perms        = has_opt(perm_options::add);
+  const bool remove_perms     = has_opt(perm_options::remove);
+  _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
+      (add_perms + remove_perms + has_opt(perm_options::replace)) == 1,
+      "One and only one of the perm_options constants 'replace', 'add', or 'remove' must be present in opts");
+
+  bool set_sym_perms = false;
+  prms &= perms::mask;
+  if (!resolve_symlinks || (add_perms || remove_perms)) {
+    error_code m_ec;
+    file_status st = resolve_symlinks ? detail::posix_stat(p, &m_ec) : detail::posix_lstat(p, &m_ec);
+    set_sym_perms  = is_symlink(st);
+    if (m_ec)
+      return err.report(m_ec);
+    // TODO(hardening): double-check this assertion -- it might be a valid (if rare) case when the permissions are
+    // unknown.
+    _LIBCPP_ASSERT_VALID_EXTERNAL_API_CALL(st.permissions() != perms::unknown, "Permissions unexpectedly unknown");
+    if (add_perms)
+      prms |= st.permissions();
+    else if (remove_perms)
+      prms = st.permissions() & ~prms;
+  }
+  const auto real_perms = static_cast<detail::ModeT>(prms & perms::mask);
+
+#if defined(AT_SYMLINK_NOFOLLOW) && defined(AT_FDCWD)
+  const int flags = set_sym_perms ? AT_SYMLINK_NOFOLLOW : 0;
+  if (detail::fchmodat(AT_FDCWD, p.c_str(), real_perms, flags) == -1) {
+    return err.report(capture_errno());
+  }
+#else
+  if (set_sym_perms)
+    return err.report(errc::operation_not_supported);
+  if (::chmod(p.c_str(), real_perms) == -1) {
+    return err.report(capture_errno());
+  }
+#endif
+}
+
+path __read_symlink(const path& p, error_code* ec) {
+  ErrorHandler<path> err("read_symlink", ec, &p);
+
+#if defined(PATH_MAX) || defined(MAX_SYMLINK_SIZE)
+  struct NullDeleter {
+    void operator()(void*) const {}
+  };
+#  ifdef MAX_SYMLINK_SIZE
+  const size_t size = MAX_SYMLINK_SIZE + 1;
+#  else
+  const size_t size = PATH_MAX + 1;
+#  endif
+  path::value_type stack_buff[size];
+  auto buff = std::unique_ptr<path::value_type[], NullDeleter>(stack_buff);
+#else
+  StatT sb;
+  if (detail::lstat(p.c_str(), &sb) == -1) {
+    return err.report(capture_errno());
+  }
+  const size_t size = sb.st_size + 1;
+  auto buff         = unique_ptr<path::value_type[]>(new path::value_type[size]);
+#endif
+  detail::SSizeT ret;
+  if ((ret = detail::readlink(p.c_str(), buff.get(), size)) == -1)
+    return err.report(capture_errno());
+  // Note that `ret` returning `0` would work, resulting in a valid empty string being returned.
+  if (static_cast<size_t>(ret) >= size)
+    return err.report(errc::value_too_large);
+  buff[ret] = 0;
+  return {buff.get()};
+}
+
+bool __remove(const path& p, error_code* ec) {
+  ErrorHandler<bool> err("remove", ec, &p);
+  if (detail::remove(p.c_str()) == -1) {
+    if (errno != ENOENT)
+      err.report(capture_errno());
+    return false;
+  }
+  return true;
+}
+
+// We currently have two implementations of `__remove_all`. The first one is general and
+// used on platforms where we don't have access to the `openat()` family of POSIX functions.
+// That implementation uses `directory_iterator`, however it is vulnerable to some race
+// conditions, see https://reviews.llvm.org/D118134 for details.
+//
+// The second implementation is used on platforms where `openat()` & friends are available,
+// and it threads file descriptors through recursive calls to avoid such race conditions.
+#if defined(_LIBCPP_WIN32API) || defined(__MVS__)
+#  define REMOVE_ALL_USE_DIRECTORY_ITERATOR
+#endif
+
+#if defined(REMOVE_ALL_USE_DIRECTORY_ITERATOR)
+
+namespace {
+
+uintmax_t remove_all_impl(path const& p, error_code& ec) {
+  const auto npos      = static_cast<uintmax_t>(-1);
+  const file_status st = __symlink_status(p, &ec);
+  if (ec)
+    return npos;
+  uintmax_t count = 1;
+  if (is_directory(st)) {
+    for (directory_iterator it(p, ec); !ec && it != directory_iterator(); it.increment(ec)) {
+      auto other_count = remove_all_impl(it->path(), ec);
+      if (ec)
+        return npos;
+      count += other_count;
+    }
+    if (ec)
+      return npos;
+  }
+  if (!__remove(p, &ec))
+    return npos;
+  return count;
+}
+
+} // end namespace
+
+uintmax_t __remove_all(const path& p, error_code* ec) {
+  ErrorHandler<uintmax_t> err("remove_all", ec, &p);
+
+  error_code mec;
+  auto count = remove_all_impl(p, mec);
+  if (mec) {
+    if (mec == errc::no_such_file_or_directory)
+      return 0;
+    return err.report(mec);
+  }
+  return count;
+}
+
+#else // !REMOVE_ALL_USE_DIRECTORY_ITERATOR
+
+namespace {
+
+template <class Cleanup>
+struct scope_exit {
+  explicit scope_exit(Cleanup const& cleanup) : cleanup_(cleanup) {}
+
+  ~scope_exit() { cleanup_(); }
+
+private:
+  Cleanup cleanup_;
+};
+_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(scope_exit);
+
+uintmax_t remove_all_impl(int parent_directory, const path& p, error_code& ec) {
+  // First, try to open the path as a directory.
+  const int options = O_CLOEXEC | O_RDONLY | O_DIRECTORY | O_NOFOLLOW;
+  int fd            = ::openat(parent_directory, p.c_str(), options);
+  if (fd != -1) {
+    // If that worked, iterate over the contents of the directory and
+    // remove everything in it, recursively.
+    DIR* stream = ::fdopendir(fd);
+    if (stream == nullptr) {
+      ::close(fd);
+      ec = detail::capture_errno();
+      return 0;
+    }
+    // Note: `::closedir` will also close the associated file descriptor, so
+    // there should be no call to `close(fd)`.
+    scope_exit close_stream([=] { ::closedir(stream); });
+
+    uintmax_t count = 0;
+    while (true) {
+      auto [str, type] = detail::posix_readdir(stream, ec);
+      static_assert(std::is_same_v<decltype(str), std::string_view>);
+      if (str == "." || str == "..") {
+        continue;
+      } else if (ec || str.empty()) {
+        break; // we're done iterating through the directory
+      } else {
+        count += remove_all_impl(fd, str, ec);
+      }
+    }
+
+    // Then, remove the now-empty directory itself.
+    if (::unlinkat(parent_directory, p.c_str(), AT_REMOVEDIR) == -1) {
+      ec = detail::capture_errno();
+      return count;
+    }
+
+    return count + 1; // the contents of the directory + the directory itself
+  }
+
+  ec = detail::capture_errno();
+
+  // If we failed to open `p` because it didn't exist, it's not an
+  // error -- it might have moved or have been deleted already.
+  if (ec == errc::no_such_file_or_directory) {
+    ec.clear();
+    return 0;
+  }
+
+  // If opening `p` failed because it wasn't a directory, remove it as
+  // a normal file instead. Note that `openat()` can return either ENOTDIR
+  // or ELOOP depending on the exact reason of the failure. On FreeBSD it
+  // may return EMLINK instead of ELOOP, contradicting POSIX.
+  if (ec == errc::not_a_directory || ec == errc::too_many_symbolic_link_levels || ec == errc::too_many_links) {
+    ec.clear();
+    if (::unlinkat(parent_directory, p.c_str(), /* flags = */ 0) == -1) {
+      ec = detail::capture_errno();
+      return 0;
+    }
+    return 1;
+  }
+
+  // Otherwise, it's a real error -- we don't remove anything.
+  return 0;
+}
+
+} // end namespace
+
+uintmax_t __remove_all(const path& p, error_code* ec) {
+  ErrorHandler<uintmax_t> err("remove_all", ec, &p);
+  error_code mec;
+  uintmax_t count = remove_all_impl(AT_FDCWD, p, mec);
+  if (mec)
+    return err.report(mec);
+  return count;
+}
+
+#endif // REMOVE_ALL_USE_DIRECTORY_ITERATOR
+
+void __rename(const path& from, const path& to, error_code* ec) {
+  ErrorHandler<void> err("rename", ec, &from, &to);
+  if (detail::rename(from.c_str(), to.c_str()) == -1)
+    err.report(capture_errno());
+}
+
+void __resize_file(const path& p, uintmax_t size, error_code* ec) {
+  ErrorHandler<void> err("resize_file", ec, &p);
+  if (detail::truncate(p.c_str(), static_cast< ::off_t>(size)) == -1)
+    return err.report(capture_errno());
+}
+
+space_info __space(const path& p, error_code* ec) {
+  ErrorHandler<void> err("space", ec, &p);
+  space_info si;
+  detail::StatVFS m_svfs = {};
+  if (detail::statvfs(p.c_str(), &m_svfs) == -1) {
+    err.report(capture_errno());
+    si.capacity = si.free = si.available = static_cast<uintmax_t>(-1);
+    return si;
+  }
+  // Multiply with overflow checking.
+  auto do_mult = [&](uintmax_t& out, uintmax_t other) {
+    out = other * m_svfs.f_frsize;
+    if (other == 0 || out / other != m_svfs.f_frsize)
+      out = static_cast<uintmax_t>(-1);
+  };
+  do_mult(si.capacity, m_svfs.f_blocks);
+  do_mult(si.free, m_svfs.f_bfree);
+  do_mult(si.available, m_svfs.f_bavail);
+  return si;
+}
+
+file_status __status(const path& p, error_code* ec) { return detail::posix_stat(p, ec); }
+
+file_status __symlink_status(const path& p, error_code* ec) { return detail::posix_lstat(p, ec); }
+
+path __temp_directory_path(error_code* ec) {
+  ErrorHandler<path> err("temp_directory_path", ec);
+
+#if defined(_LIBCPP_WIN32API)
+  wchar_t buf[MAX_PATH];
+  DWORD retval = GetTempPathW(MAX_PATH, buf);
+  if (!retval)
+    return err.report(detail::make_windows_error(GetLastError()));
+  if (retval > MAX_PATH)
+    return err.report(errc::filename_too_long);
+  // GetTempPathW returns a path with a trailing slash, which we
+  // shouldn't include for consistency.
+  if (buf[retval - 1] == L'\\')
+    buf[retval - 1] = L'\0';
+  path p(buf);
+#else
+  const char* env_paths[] = {"TMPDIR", "TMP", "TEMP", "TEMPDIR"};
+  const char* ret         = nullptr;
+
+  for (auto& ep : env_paths)
+    if ((ret = getenv(ep)))
+      break;
+  if (ret == nullptr) {
+#  if defined(__ANDROID__)
+    ret = "/data/local/tmp";
+#  else
+    ret = "/tmp";
+#  endif
+  }
+
+  path p(ret);
+#endif
+  error_code m_ec;
+  file_status st = detail::posix_stat(p, &m_ec);
+  if (!status_known(st))
+    return err.report(m_ec, "cannot access path " PATH_CSTR_FMT, p.c_str());
+
+  if (!exists(st) || !is_directory(st))
+    return err.report(errc::not_a_directory, "path " PATH_CSTR_FMT " is not a directory", p.c_str());
+
+  return p;
+}
+
+path __weakly_canonical(const path& p, error_code* ec) {
+  ErrorHandler<path> err("weakly_canonical", ec, &p);
+
+  if (p.empty())
+    return __canonical("", ec);
+
+  path result;
+  path tmp;
+  tmp.__reserve(p.native().size());
+  auto PP = PathParser::CreateEnd(p.native());
+  --PP;
+  vector<string_view_t> DNEParts;
+
+  error_code m_ec;
+  while (PP.State_ != PathParser::PS_BeforeBegin) {
+    tmp.assign(createView(p.native().data(), &PP.RawEntry.back()));
+    file_status st = __status(tmp, &m_ec);
+    if (!status_known(st)) {
+      return err.report(m_ec);
+    } else if (exists(st)) {
+      result = __canonical(tmp, &m_ec);
+      if (m_ec) {
+        return err.report(m_ec);
+      }
+      break;
+    }
+    DNEParts.push_back(*PP);
+    --PP;
+  }
+  if (PP.State_ == PathParser::PS_BeforeBegin) {
+    result = __canonical("", &m_ec);
+    if (m_ec) {
+      return err.report(m_ec);
+    }
+  }
+  if (DNEParts.empty())
+    return result;
+  for (auto It = DNEParts.rbegin(); It != DNEParts.rend(); ++It)
+    result /= *It;
+  return result.lexically_normal();
+}
+
+_LIBCPP_END_NAMESPACE_FILESYSTEM

third_party/libcxx/fs/path.cpp

@@ -0,0 +1,441 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 <__config>
+#include <filesystem>
+#include <vector>
+
+#include "error.h"
+#include "path_parser.h"
+
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+
+using detail::ErrorHandler;
+using parser::createView;
+using parser::PathParser;
+using parser::string_view_t;
+
+///////////////////////////////////////////////////////////////////////////////
+//                            path definitions
+///////////////////////////////////////////////////////////////////////////////
+
+constexpr path::value_type path::preferred_separator;
+
+path& path::replace_extension(path const& replacement) {
+  path p = extension();
+  if (not p.empty()) {
+    __pn_.erase(__pn_.size() - p.native().size());
+  }
+  if (!replacement.empty()) {
+    if (replacement.native()[0] != '.') {
+      __pn_ += PATHSTR(".");
+    }
+    __pn_.append(replacement.__pn_);
+  }
+  return *this;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// path.decompose
+
+string_view_t path::__root_name() const {
+  auto PP = PathParser::CreateBegin(__pn_);
+  if (PP.State_ == PathParser::PS_InRootName)
+    return *PP;
+  return {};
+}
+
+string_view_t path::__root_directory() const {
+  auto PP = PathParser::CreateBegin(__pn_);
+  if (PP.State_ == PathParser::PS_InRootName)
+    ++PP;
+  if (PP.State_ == PathParser::PS_InRootDir)
+    return *PP;
+  return {};
+}
+
+string_view_t path::__root_path_raw() const {
+  auto PP = PathParser::CreateBegin(__pn_);
+  if (PP.State_ == PathParser::PS_InRootName) {
+    auto NextCh = PP.peek();
+    if (NextCh && isSeparator(*NextCh)) {
+      ++PP;
+      return createView(__pn_.data(), &PP.RawEntry.back());
+    }
+    return PP.RawEntry;
+  }
+  if (PP.State_ == PathParser::PS_InRootDir)
+    return *PP;
+  return {};
+}
+
+static bool ConsumeRootName(PathParser* PP) {
+  static_assert(PathParser::PS_BeforeBegin == 1 && PathParser::PS_InRootName == 2, "Values for enums are incorrect");
+  while (PP->State_ <= PathParser::PS_InRootName)
+    ++(*PP);
+  return PP->State_ == PathParser::PS_AtEnd;
+}
+
+static bool ConsumeRootDir(PathParser* PP) {
+  static_assert(PathParser::PS_BeforeBegin == 1 && PathParser::PS_InRootName == 2 && PathParser::PS_InRootDir == 3,
+                "Values for enums are incorrect");
+  while (PP->State_ <= PathParser::PS_InRootDir)
+    ++(*PP);
+  return PP->State_ == PathParser::PS_AtEnd;
+}
+
+string_view_t path::__relative_path() const {
+  auto PP = PathParser::CreateBegin(__pn_);
+  if (ConsumeRootDir(&PP))
+    return {};
+  return createView(PP.RawEntry.data(), &__pn_.back());
+}
+
+string_view_t path::__parent_path() const {
+  if (empty())
+    return {};
+  // Determine if we have a root path but not a relative path. In that case
+  // return *this.
+  {
+    auto PP = PathParser::CreateBegin(__pn_);
+    if (ConsumeRootDir(&PP))
+      return __pn_;
+  }
+  // Otherwise remove a single element from the end of the path, and return
+  // a string representing that path
+  {
+    auto PP = PathParser::CreateEnd(__pn_);
+    --PP;
+    if (PP.RawEntry.data() == __pn_.data())
+      return {};
+    --PP;
+    return createView(__pn_.data(), &PP.RawEntry.back());
+  }
+}
+
+string_view_t path::__filename() const {
+  if (empty())
+    return {};
+  {
+    PathParser PP = PathParser::CreateBegin(__pn_);
+    if (ConsumeRootDir(&PP))
+      return {};
+  }
+  return *(--PathParser::CreateEnd(__pn_));
+}
+
+string_view_t path::__stem() const { return parser::separate_filename(__filename()).first; }
+
+string_view_t path::__extension() const { return parser::separate_filename(__filename()).second; }
+
+////////////////////////////////////////////////////////////////////////////
+// path.gen
+
+enum PathPartKind : unsigned char { PK_None, PK_RootSep, PK_Filename, PK_Dot, PK_DotDot, PK_TrailingSep };
+
+static PathPartKind ClassifyPathPart(string_view_t Part) {
+  if (Part.empty())
+    return PK_TrailingSep;
+  if (Part == PATHSTR("."))
+    return PK_Dot;
+  if (Part == PATHSTR(".."))
+    return PK_DotDot;
+  if (Part == PATHSTR("/"))
+    return PK_RootSep;
+#if defined(_LIBCPP_WIN32API)
+  if (Part == PATHSTR("\\"))
+    return PK_RootSep;
+#endif
+  return PK_Filename;
+}
+
+path path::lexically_normal() const {
+  if (__pn_.empty())
+    return *this;
+
+  using PartKindPair = pair<string_view_t, PathPartKind>;
+  vector<PartKindPair> Parts;
+  // Guess as to how many elements the path has to avoid reallocating.
+  Parts.reserve(32);
+
+  // Track the total size of the parts as we collect them. This allows the
+  // resulting path to reserve the correct amount of memory.
+  size_t NewPathSize = 0;
+  auto AddPart       = [&](PathPartKind K, string_view_t P) {
+    NewPathSize += P.size();
+    Parts.emplace_back(P, K);
+  };
+  auto LastPartKind = [&]() {
+    if (Parts.empty())
+      return PK_None;
+    return Parts.back().second;
+  };
+
+  bool MaybeNeedTrailingSep = false;
+  // Build a stack containing the remaining elements of the path, popping off
+  // elements which occur before a '..' entry.
+  for (auto PP = PathParser::CreateBegin(__pn_); PP; ++PP) {
+    auto Part         = *PP;
+    PathPartKind Kind = ClassifyPathPart(Part);
+    switch (Kind) {
+    case PK_Filename:
+    case PK_RootSep: {
+      // Add all non-dot and non-dot-dot elements to the stack of elements.
+      AddPart(Kind, Part);
+      MaybeNeedTrailingSep = false;
+      break;
+    }
+    case PK_DotDot: {
+      // Only push a ".." element if there are no elements preceding the "..",
+      // or if the preceding element is itself "..".
+      auto LastKind = LastPartKind();
+      if (LastKind == PK_Filename) {
+        NewPathSize -= Parts.back().first.size();
+        Parts.pop_back();
+      } else if (LastKind != PK_RootSep)
+        AddPart(PK_DotDot, PATHSTR(".."));
+      MaybeNeedTrailingSep = LastKind == PK_Filename;
+      break;
+    }
+    case PK_Dot:
+    case PK_TrailingSep: {
+      MaybeNeedTrailingSep = true;
+      break;
+    }
+    case PK_None:
+      __libcpp_unreachable();
+    }
+  }
+  // [fs.path.generic]p6.8: If the path is empty, add a dot.
+  if (Parts.empty())
+    return PATHSTR(".");
+
+  // [fs.path.generic]p6.7: If the last filename is dot-dot, remove any
+  // trailing directory-separator.
+  bool NeedTrailingSep = MaybeNeedTrailingSep && LastPartKind() == PK_Filename;
+
+  path Result;
+  Result.__pn_.reserve(Parts.size() + NewPathSize + NeedTrailingSep);
+  for (auto& PK : Parts)
+    Result /= PK.first;
+
+  if (NeedTrailingSep)
+    Result /= PATHSTR("");
+
+  Result.make_preferred();
+  return Result;
+}
+
+static int DetermineLexicalElementCount(PathParser PP) {
+  int Count = 0;
+  for (; PP; ++PP) {
+    auto Elem = *PP;
+    if (Elem == PATHSTR(".."))
+      --Count;
+    else if (Elem != PATHSTR(".") && Elem != PATHSTR(""))
+      ++Count;
+  }
+  return Count;
+}
+
+path path::lexically_relative(const path& base) const {
+  { // perform root-name/root-directory mismatch checks
+    auto PP                      = PathParser::CreateBegin(__pn_);
+    auto PPBase                  = PathParser::CreateBegin(base.__pn_);
+    auto CheckIterMismatchAtBase = [&]() {
+      return PP.State_ != PPBase.State_ && (PP.inRootPath() || PPBase.inRootPath());
+    };
+    if (PP.inRootName() && PPBase.inRootName()) {
+      if (*PP != *PPBase)
+        return {};
+    } else if (CheckIterMismatchAtBase())
+      return {};
+
+    if (PP.inRootPath())
+      ++PP;
+    if (PPBase.inRootPath())
+      ++PPBase;
+    if (CheckIterMismatchAtBase())
+      return {};
+  }
+
+  // Find the first mismatching element
+  auto PP     = PathParser::CreateBegin(__pn_);
+  auto PPBase = PathParser::CreateBegin(base.__pn_);
+  while (PP && PPBase && PP.State_ == PPBase.State_ && *PP == *PPBase) {
+    ++PP;
+    ++PPBase;
+  }
+
+  // If there is no mismatch, return ".".
+  if (!PP && !PPBase)
+    return ".";
+
+  // Otherwise, determine the number of elements, 'n', which are not dot or
+  // dot-dot minus the number of dot-dot elements.
+  int ElemCount = DetermineLexicalElementCount(PPBase);
+  if (ElemCount < 0)
+    return {};
+
+  // if n == 0 and (a == end() || a->empty()), returns path("."); otherwise
+  if (ElemCount == 0 && (PP.atEnd() || *PP == PATHSTR("")))
+    return PATHSTR(".");
+
+  // return a path constructed with 'n' dot-dot elements, followed by the
+  // elements of '*this' after the mismatch.
+  path Result;
+  // FIXME: Reserve enough room in Result that it won't have to re-allocate.
+  while (ElemCount--)
+    Result /= PATHSTR("..");
+  for (; PP; ++PP)
+    Result /= *PP;
+  return Result;
+}
+
+////////////////////////////////////////////////////////////////////////////
+// path.comparisons
+static int CompareRootName(PathParser* LHS, PathParser* RHS) {
+  if (!LHS->inRootName() && !RHS->inRootName())
+    return 0;
+
+  auto GetRootName = [](PathParser* Parser) -> string_view_t { return Parser->inRootName() ? **Parser : PATHSTR(""); };
+  int res          = GetRootName(LHS).compare(GetRootName(RHS));
+  ConsumeRootName(LHS);
+  ConsumeRootName(RHS);
+  return res;
+}
+
+static int CompareRootDir(PathParser* LHS, PathParser* RHS) {
+  if (!LHS->inRootDir() && RHS->inRootDir())
+    return -1;
+  else if (LHS->inRootDir() && !RHS->inRootDir())
+    return 1;
+  else {
+    ConsumeRootDir(LHS);
+    ConsumeRootDir(RHS);
+    return 0;
+  }
+}
+
+static int CompareRelative(PathParser* LHSPtr, PathParser* RHSPtr) {
+  auto& LHS = *LHSPtr;
+  auto& RHS = *RHSPtr;
+
+  int res;
+  while (LHS && RHS) {
+    if ((res = (*LHS).compare(*RHS)) != 0)
+      return res;
+    ++LHS;
+    ++RHS;
+  }
+  return 0;
+}
+
+static int CompareEndState(PathParser* LHS, PathParser* RHS) {
+  if (LHS->atEnd() && !RHS->atEnd())
+    return -1;
+  else if (!LHS->atEnd() && RHS->atEnd())
+    return 1;
+  return 0;
+}
+
+int path::__compare(string_view_t __s) const {
+  auto LHS = PathParser::CreateBegin(__pn_);
+  auto RHS = PathParser::CreateBegin(__s);
+  int res;
+
+  if ((res = CompareRootName(&LHS, &RHS)) != 0)
+    return res;
+
+  if ((res = CompareRootDir(&LHS, &RHS)) != 0)
+    return res;
+
+  if ((res = CompareRelative(&LHS, &RHS)) != 0)
+    return res;
+
+  return CompareEndState(&LHS, &RHS);
+}
+
+////////////////////////////////////////////////////////////////////////////
+// path.nonmembers
+size_t hash_value(const path& __p) noexcept {
+  auto PP           = PathParser::CreateBegin(__p.native());
+  size_t hash_value = 0;
+  hash<string_view_t> hasher;
+  while (PP) {
+    hash_value = __hash_combine(hash_value, hasher(*PP));
+    ++PP;
+  }
+  return hash_value;
+}
+
+////////////////////////////////////////////////////////////////////////////
+// path.itr
+path::iterator path::begin() const {
+  auto PP = PathParser::CreateBegin(__pn_);
+  iterator it;
+  it.__path_ptr_ = this;
+  it.__state_    = static_cast<path::iterator::_ParserState>(PP.State_);
+  it.__entry_    = PP.RawEntry;
+  it.__stashed_elem_.__assign_view(*PP);
+  return it;
+}
+
+path::iterator path::end() const {
+  iterator it{};
+  it.__state_    = path::iterator::_AtEnd;
+  it.__path_ptr_ = this;
+  return it;
+}
+
+path::iterator& path::iterator::__increment() {
+  PathParser PP(__path_ptr_->native(), __entry_, __state_);
+  ++PP;
+  __state_ = static_cast<_ParserState>(PP.State_);
+  __entry_ = PP.RawEntry;
+  __stashed_elem_.__assign_view(*PP);
+  return *this;
+}
+
+path::iterator& path::iterator::__decrement() {
+  PathParser PP(__path_ptr_->native(), __entry_, __state_);
+  --PP;
+  __state_ = static_cast<_ParserState>(PP.State_);
+  __entry_ = PP.RawEntry;
+  __stashed_elem_.__assign_view(*PP);
+  return *this;
+}
+
+#if defined(_LIBCPP_WIN32API)
+////////////////////////////////////////////////////////////////////////////
+// Windows path conversions
+size_t __wide_to_char(const wstring& str, char* out, size_t outlen) {
+  if (str.empty())
+    return 0;
+  ErrorHandler<size_t> err("__wide_to_char", nullptr);
+  UINT codepage     = AreFileApisANSI() ? CP_ACP : CP_OEMCP;
+  BOOL used_default = FALSE;
+  int ret           = WideCharToMultiByte(codepage, 0, str.data(), str.size(), out, outlen, nullptr, &used_default);
+  if (ret <= 0 || used_default)
+    return err.report(errc::illegal_byte_sequence);
+  return ret;
+}
+
+size_t __char_to_wide(const string& str, wchar_t* out, size_t outlen) {
+  if (str.empty())
+    return 0;
+  ErrorHandler<size_t> err("__char_to_wide", nullptr);
+  UINT codepage = AreFileApisANSI() ? CP_ACP : CP_OEMCP;
+  int ret       = MultiByteToWideChar(codepage, MB_ERR_INVALID_CHARS, str.data(), str.size(), out, outlen);
+  if (ret <= 0)
+    return err.report(errc::illegal_byte_sequence);
+  return ret;
+}
+#endif
+
+_LIBCPP_END_NAMESPACE_FILESYSTEM

third_party/libcxx/fs/path_parser.h

@@ -0,0 +1,352 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 PATH_PARSER_H
+#define PATH_PARSER_H
+
+#include <__config>
+#include <__utility/unreachable.h>
+#include <cstddef>
+#include <filesystem>
+#include <utility>
+
+#include "format_string.h"
+
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+
+inline bool isSeparator(path::value_type C) {
+  if (C == '/')
+    return true;
+#if defined(_LIBCPP_WIN32API)
+  if (C == '\\')
+    return true;
+#endif
+  return false;
+}
+
+inline bool isDriveLetter(path::value_type C) { return (C >= 'a' && C <= 'z') || (C >= 'A' && C <= 'Z'); }
+
+namespace parser {
+
+using string_view_t    = path::__string_view;
+using string_view_pair = pair<string_view_t, string_view_t>;
+using PosPtr           = path::value_type const*;
+
+struct PathParser {
+  enum ParserState : unsigned char {
+    // Zero is a special sentinel value used by default constructed iterators.
+    PS_BeforeBegin   = path::iterator::_BeforeBegin,
+    PS_InRootName    = path::iterator::_InRootName,
+    PS_InRootDir     = path::iterator::_InRootDir,
+    PS_InFilenames   = path::iterator::_InFilenames,
+    PS_InTrailingSep = path::iterator::_InTrailingSep,
+    PS_AtEnd         = path::iterator::_AtEnd
+  };
+
+  const string_view_t Path;
+  string_view_t RawEntry;
+  ParserState State_;
+
+private:
+  PathParser(string_view_t P, ParserState State) noexcept : Path(P), State_(State) {}
+
+public:
+  PathParser(string_view_t P, string_view_t E, unsigned char S)
+      : Path(P), RawEntry(E), State_(static_cast<ParserState>(S)) {
+    // S cannot be '0' or PS_BeforeBegin.
+  }
+
+  static PathParser CreateBegin(string_view_t P) noexcept {
+    PathParser PP(P, PS_BeforeBegin);
+    PP.increment();
+    return PP;
+  }
+
+  static PathParser CreateEnd(string_view_t P) noexcept {
+    PathParser PP(P, PS_AtEnd);
+    return PP;
+  }
+
+  PosPtr peek() const noexcept {
+    auto TkEnd = getNextTokenStartPos();
+    auto End   = getAfterBack();
+    return TkEnd == End ? nullptr : TkEnd;
+  }
+
+  void increment() noexcept {
+    const PosPtr End   = getAfterBack();
+    const PosPtr Start = getNextTokenStartPos();
+    if (Start == End)
+      return makeState(PS_AtEnd);
+
+    switch (State_) {
+    case PS_BeforeBegin: {
+      PosPtr TkEnd = consumeRootName(Start, End);
+      if (TkEnd)
+        return makeState(PS_InRootName, Start, TkEnd);
+    }
+      _LIBCPP_FALLTHROUGH();
+    case PS_InRootName: {
+      PosPtr TkEnd = consumeAllSeparators(Start, End);
+      if (TkEnd)
+        return makeState(PS_InRootDir, Start, TkEnd);
+      else
+        return makeState(PS_InFilenames, Start, consumeName(Start, End));
+    }
+    case PS_InRootDir:
+      return makeState(PS_InFilenames, Start, consumeName(Start, End));
+
+    case PS_InFilenames: {
+      PosPtr SepEnd = consumeAllSeparators(Start, End);
+      if (SepEnd != End) {
+        PosPtr TkEnd = consumeName(SepEnd, End);
+        if (TkEnd)
+          return makeState(PS_InFilenames, SepEnd, TkEnd);
+      }
+      return makeState(PS_InTrailingSep, Start, SepEnd);
+    }
+
+    case PS_InTrailingSep:
+      return makeState(PS_AtEnd);
+
+    case PS_AtEnd:
+      __libcpp_unreachable();
+    }
+  }
+
+  void decrement() noexcept {
+    const PosPtr REnd   = getBeforeFront();
+    const PosPtr RStart = getCurrentTokenStartPos() - 1;
+    if (RStart == REnd) // we're decrementing the begin
+      return makeState(PS_BeforeBegin);
+
+    switch (State_) {
+    case PS_AtEnd: {
+      // Try to consume a trailing separator or root directory first.
+      if (PosPtr SepEnd = consumeAllSeparators(RStart, REnd)) {
+        if (SepEnd == REnd)
+          return makeState(PS_InRootDir, Path.data(), RStart + 1);
+        PosPtr TkStart = consumeRootName(SepEnd, REnd);
+        if (TkStart == REnd)
+          return makeState(PS_InRootDir, RStart, RStart + 1);
+        return makeState(PS_InTrailingSep, SepEnd + 1, RStart + 1);
+      } else {
+        PosPtr TkStart = consumeRootName(RStart, REnd);
+        if (TkStart == REnd)
+          return makeState(PS_InRootName, TkStart + 1, RStart + 1);
+        TkStart = consumeName(RStart, REnd);
+        return makeState(PS_InFilenames, TkStart + 1, RStart + 1);
+      }
+    }
+    case PS_InTrailingSep:
+      return makeState(PS_InFilenames, consumeName(RStart, REnd) + 1, RStart + 1);
+    case PS_InFilenames: {
+      PosPtr SepEnd = consumeAllSeparators(RStart, REnd);
+      if (SepEnd == REnd)
+        return makeState(PS_InRootDir, Path.data(), RStart + 1);
+      PosPtr TkStart = consumeRootName(SepEnd ? SepEnd : RStart, REnd);
+      if (TkStart == REnd) {
+        if (SepEnd)
+          return makeState(PS_InRootDir, SepEnd + 1, RStart + 1);
+        return makeState(PS_InRootName, TkStart + 1, RStart + 1);
+      }
+      TkStart = consumeName(SepEnd, REnd);
+      return makeState(PS_InFilenames, TkStart + 1, SepEnd + 1);
+    }
+    case PS_InRootDir:
+      return makeState(PS_InRootName, Path.data(), RStart + 1);
+    case PS_InRootName:
+    case PS_BeforeBegin:
+      __libcpp_unreachable();
+    }
+  }
+
+  /// \brief Return a view with the "preferred representation" of the current
+  ///   element. For example trailing separators are represented as a '.'
+  string_view_t operator*() const noexcept {
+    switch (State_) {
+    case PS_BeforeBegin:
+    case PS_AtEnd:
+      return PATHSTR("");
+    case PS_InRootDir:
+      if (RawEntry[0] == '\\')
+        return PATHSTR("\\");
+      else
+        return PATHSTR("/");
+    case PS_InTrailingSep:
+      return PATHSTR("");
+    case PS_InRootName:
+    case PS_InFilenames:
+      return RawEntry;
+    }
+    __libcpp_unreachable();
+  }
+
+  explicit operator bool() const noexcept { return State_ != PS_BeforeBegin && State_ != PS_AtEnd; }
+
+  PathParser& operator++() noexcept {
+    increment();
+    return *this;
+  }
+
+  PathParser& operator--() noexcept {
+    decrement();
+    return *this;
+  }
+
+  bool atEnd() const noexcept { return State_ == PS_AtEnd; }
+
+  bool inRootDir() const noexcept { return State_ == PS_InRootDir; }
+
+  bool inRootName() const noexcept { return State_ == PS_InRootName; }
+
+  bool inRootPath() const noexcept { return inRootName() || inRootDir(); }
+
+private:
+  void makeState(ParserState NewState, PosPtr Start, PosPtr End) noexcept {
+    State_    = NewState;
+    RawEntry = string_view_t(Start, End - Start);
+  }
+  void makeState(ParserState NewState) noexcept {
+    State_    = NewState;
+    RawEntry = {};
+  }
+
+  PosPtr getAfterBack() const noexcept { return Path.data() + Path.size(); }
+
+  PosPtr getBeforeFront() const noexcept { return Path.data() - 1; }
+
+  /// \brief Return a pointer to the first character after the currently
+  ///   lexed element.
+  PosPtr getNextTokenStartPos() const noexcept {
+    switch (State_) {
+    case PS_BeforeBegin:
+      return Path.data();
+    case PS_InRootName:
+    case PS_InRootDir:
+    case PS_InFilenames:
+      return &RawEntry.back() + 1;
+    case PS_InTrailingSep:
+    case PS_AtEnd:
+      return getAfterBack();
+    }
+    __libcpp_unreachable();
+  }
+
+  /// \brief Return a pointer to the first character in the currently lexed
+  ///   element.
+  PosPtr getCurrentTokenStartPos() const noexcept {
+    switch (State_) {
+    case PS_BeforeBegin:
+    case PS_InRootName:
+      return &Path.front();
+    case PS_InRootDir:
+    case PS_InFilenames:
+    case PS_InTrailingSep:
+      return &RawEntry.front();
+    case PS_AtEnd:
+      return &Path.back() + 1;
+    }
+    __libcpp_unreachable();
+  }
+
+  // Consume all consecutive separators.
+  PosPtr consumeAllSeparators(PosPtr P, PosPtr End) const noexcept {
+    if (P == nullptr || P == End || !isSeparator(*P))
+      return nullptr;
+    const int Inc = P < End ? 1 : -1;
+    P += Inc;
+    while (P != End && isSeparator(*P))
+      P += Inc;
+    return P;
+  }
+
+  // Consume exactly N separators, or return nullptr.
+  PosPtr consumeNSeparators(PosPtr P, PosPtr End, int N) const noexcept {
+    PosPtr Ret = consumeAllSeparators(P, End);
+    if (Ret == nullptr)
+      return nullptr;
+    if (P < End) {
+      if (Ret == P + N)
+        return Ret;
+    } else {
+      if (Ret == P - N)
+        return Ret;
+    }
+    return nullptr;
+  }
+
+  PosPtr consumeName(PosPtr P, PosPtr End) const noexcept {
+    PosPtr Start = P;
+    if (P == nullptr || P == End || isSeparator(*P))
+      return nullptr;
+    const int Inc = P < End ? 1 : -1;
+    P += Inc;
+    while (P != End && !isSeparator(*P))
+      P += Inc;
+    if (P == End && Inc < 0) {
+      // Iterating backwards and consumed all the rest of the input.
+      // Check if the start of the string would have been considered
+      // a root name.
+      PosPtr RootEnd = consumeRootName(End + 1, Start);
+      if (RootEnd)
+        return RootEnd - 1;
+    }
+    return P;
+  }
+
+  PosPtr consumeDriveLetter(PosPtr P, PosPtr End) const noexcept {
+    if (P == End)
+      return nullptr;
+    if (P < End) {
+      if (P + 1 == End || !isDriveLetter(P[0]) || P[1] != ':')
+        return nullptr;
+      return P + 2;
+    } else {
+      if (P - 1 == End || !isDriveLetter(P[-1]) || P[0] != ':')
+        return nullptr;
+      return P - 2;
+    }
+  }
+
+  PosPtr consumeNetworkRoot(PosPtr P, PosPtr End) const noexcept {
+    if (P == End)
+      return nullptr;
+    if (P < End)
+      return consumeName(consumeNSeparators(P, End, 2), End);
+    else
+      return consumeNSeparators(consumeName(P, End), End, 2);
+  }
+
+  PosPtr consumeRootName(PosPtr P, PosPtr End) const noexcept {
+#if defined(_LIBCPP_WIN32API)
+    if (PosPtr Ret = consumeDriveLetter(P, End))
+      return Ret;
+    if (PosPtr Ret = consumeNetworkRoot(P, End))
+      return Ret;
+#endif
+    return nullptr;
+  }
+};
+
+inline string_view_pair separate_filename(string_view_t const& s) {
+  if (s == PATHSTR(".") || s == PATHSTR("..") || s.empty())
+    return string_view_pair{s, PATHSTR("")};
+  auto pos = s.find_last_of('.');
+  if (pos == string_view_t::npos || pos == 0)
+    return string_view_pair{s, string_view_t{}};
+  return string_view_pair{s.substr(0, pos), s.substr(pos)};
+}
+
+inline string_view_t createView(PosPtr S, PosPtr E) noexcept { return {S, static_cast<size_t>(E - S) + 1}; }
+
+} // namespace parser
+
+_LIBCPP_END_NAMESPACE_FILESYSTEM
+
+#endif // PATH_PARSER_H

third_party/libcxx/fs/posix_compat.h

@@ -0,0 +1,497 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+//
+// POSIX-like portability helper functions.
+//
+// These generally behave like the proper posix functions, with these
+// exceptions:
+// On Windows, they take paths in wchar_t* form, instead of char* form.
+// The symlink() function is split into two frontends, symlink_file()
+// and symlink_dir().
+//
+// These are provided within an anonymous namespace within the detail
+// namespace - callers need to include this header and call them as
+// detail::function(), regardless of platform.
+//
+
+#ifndef POSIX_COMPAT_H
+#define POSIX_COMPAT_H
+
+#include <__assert>
+#include <__config>
+#include <filesystem>
+
+#include "error.h"
+#include "time_utils.h"
+
+#if defined(_LIBCPP_WIN32API)
+#  define WIN32_LEAN_AND_MEAN
+#  define NOMINMAX
+#  include <io.h>
+#  include <windows.h>
+#  include <winioctl.h>
+#else
+#  include <fcntl.h>
+#  include <sys/stat.h>
+#  include <sys/statvfs.h>
+#  include <sys/time.h>
+#  include <unistd.h>
+#endif
+#include <stdlib.h>
+#include <time.h>
+
+#if defined(_LIBCPP_WIN32API)
+// This struct isn't defined in the normal Windows SDK, but only in the
+// Windows Driver Kit.
+struct LIBCPP_REPARSE_DATA_BUFFER {
+  unsigned long ReparseTag;
+  unsigned short ReparseDataLength;
+  unsigned short Reserved;
+  union {
+    struct {
+      unsigned short SubstituteNameOffset;
+      unsigned short SubstituteNameLength;
+      unsigned short PrintNameOffset;
+      unsigned short PrintNameLength;
+      unsigned long Flags;
+      wchar_t PathBuffer[1];
+    } SymbolicLinkReparseBuffer;
+    struct {
+      unsigned short SubstituteNameOffset;
+      unsigned short SubstituteNameLength;
+      unsigned short PrintNameOffset;
+      unsigned short PrintNameLength;
+      wchar_t PathBuffer[1];
+    } MountPointReparseBuffer;
+    struct {
+      unsigned char DataBuffer[1];
+    } GenericReparseBuffer;
+  };
+};
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+
+namespace detail {
+
+#if defined(_LIBCPP_WIN32API)
+
+// Various C runtime header sets provide more or less of these. As we
+// provide our own implementation, undef all potential defines from the
+// C runtime headers and provide a complete set of macros of our own.
+
+#  undef _S_IFMT
+#  undef _S_IFDIR
+#  undef _S_IFCHR
+#  undef _S_IFIFO
+#  undef _S_IFREG
+#  undef _S_IFBLK
+#  undef _S_IFLNK
+#  undef _S_IFSOCK
+
+#  define _S_IFMT 0xF000
+#  define _S_IFDIR 0x4000
+#  define _S_IFCHR 0x2000
+#  define _S_IFIFO 0x1000
+#  define _S_IFREG 0x8000
+#  define _S_IFBLK 0x6000
+#  define _S_IFLNK 0xA000
+#  define _S_IFSOCK 0xC000
+
+#  undef S_ISDIR
+#  undef S_ISFIFO
+#  undef S_ISCHR
+#  undef S_ISREG
+#  undef S_ISLNK
+#  undef S_ISBLK
+#  undef S_ISSOCK
+
+#  define S_ISDIR(m) (((m) & _S_IFMT) == _S_IFDIR)
+#  define S_ISCHR(m) (((m) & _S_IFMT) == _S_IFCHR)
+#  define S_ISFIFO(m) (((m) & _S_IFMT) == _S_IFIFO)
+#  define S_ISREG(m) (((m) & _S_IFMT) == _S_IFREG)
+#  define S_ISBLK(m) (((m) & _S_IFMT) == _S_IFBLK)
+#  define S_ISLNK(m) (((m) & _S_IFMT) == _S_IFLNK)
+#  define S_ISSOCK(m) (((m) & _S_IFMT) == _S_IFSOCK)
+
+#  define O_NONBLOCK 0
+
+inline int set_errno(int e = GetLastError()) {
+  errno = static_cast<int>(__win_err_to_errc(e));
+  return -1;
+}
+
+class WinHandle {
+public:
+  WinHandle(const wchar_t* p, DWORD access, DWORD flags) {
+    h = CreateFileW(
+        p,
+        access,
+        FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+        nullptr,
+        OPEN_EXISTING,
+        FILE_FLAG_BACKUP_SEMANTICS | flags,
+        nullptr);
+  }
+  ~WinHandle() {
+    if (h != INVALID_HANDLE_VALUE)
+      CloseHandle(h);
+  }
+  operator HANDLE() const { return h; }
+  operator bool() const { return h != INVALID_HANDLE_VALUE; }
+
+private:
+  HANDLE h;
+};
+
+inline int stat_handle(HANDLE h, StatT* buf) {
+  FILE_BASIC_INFO basic;
+  if (!GetFileInformationByHandleEx(h, FileBasicInfo, &basic, sizeof(basic)))
+    return set_errno();
+  memset(buf, 0, sizeof(*buf));
+  buf->st_mtim = filetime_to_timespec(basic.LastWriteTime);
+  buf->st_atim = filetime_to_timespec(basic.LastAccessTime);
+  buf->st_mode = 0555; // Read-only
+  if (!(basic.FileAttributes & FILE_ATTRIBUTE_READONLY))
+    buf->st_mode |= 0222; // Write
+  if (basic.FileAttributes & FILE_ATTRIBUTE_DIRECTORY) {
+    buf->st_mode |= _S_IFDIR;
+  } else {
+    buf->st_mode |= _S_IFREG;
+  }
+  if (basic.FileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) {
+    FILE_ATTRIBUTE_TAG_INFO tag;
+    if (!GetFileInformationByHandleEx(h, FileAttributeTagInfo, &tag, sizeof(tag)))
+      return set_errno();
+    if (tag.ReparseTag == IO_REPARSE_TAG_SYMLINK)
+      buf->st_mode = (buf->st_mode & ~_S_IFMT) | _S_IFLNK;
+  }
+  FILE_STANDARD_INFO standard;
+  if (!GetFileInformationByHandleEx(h, FileStandardInfo, &standard, sizeof(standard)))
+    return set_errno();
+  buf->st_nlink = standard.NumberOfLinks;
+  buf->st_size  = standard.EndOfFile.QuadPart;
+  BY_HANDLE_FILE_INFORMATION info;
+  if (!GetFileInformationByHandle(h, &info))
+    return set_errno();
+  buf->st_dev = info.dwVolumeSerialNumber;
+  memcpy(&buf->st_ino.id[0], &info.nFileIndexHigh, 4);
+  memcpy(&buf->st_ino.id[4], &info.nFileIndexLow, 4);
+  return 0;
+}
+
+inline int stat_file(const wchar_t* path, StatT* buf, DWORD flags) {
+  WinHandle h(path, FILE_READ_ATTRIBUTES, flags);
+  if (!h)
+    return set_errno();
+  int ret = stat_handle(h, buf);
+  return ret;
+}
+
+inline int stat(const wchar_t* path, StatT* buf) { return stat_file(path, buf, 0); }
+
+inline int lstat(const wchar_t* path, StatT* buf) { return stat_file(path, buf, FILE_FLAG_OPEN_REPARSE_POINT); }
+
+inline int fstat(int fd, StatT* buf) {
+  HANDLE h = reinterpret_cast<HANDLE>(_get_osfhandle(fd));
+  return stat_handle(h, buf);
+}
+
+inline int mkdir(const wchar_t* path, int permissions) {
+  (void)permissions;
+  if (!CreateDirectoryW(path, nullptr))
+    return set_errno();
+  return 0;
+}
+
+inline int symlink_file_dir(const wchar_t* oldname, const wchar_t* newname, bool is_dir) {
+  path dest(oldname);
+  dest.make_preferred();
+  oldname     = dest.c_str();
+  DWORD flags = is_dir ? SYMBOLIC_LINK_FLAG_DIRECTORY : 0;
+  if (CreateSymbolicLinkW(newname, oldname, flags | SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE))
+    return 0;
+  int e = GetLastError();
+  if (e != ERROR_INVALID_PARAMETER)
+    return set_errno(e);
+  if (CreateSymbolicLinkW(newname, oldname, flags))
+    return 0;
+  return set_errno();
+}
+
+inline int symlink_file(const wchar_t* oldname, const wchar_t* newname) {
+  return symlink_file_dir(oldname, newname, false);
+}
+
+inline int symlink_dir(const wchar_t* oldname, const wchar_t* newname) {
+  return symlink_file_dir(oldname, newname, true);
+}
+
+inline int link(const wchar_t* oldname, const wchar_t* newname) {
+  if (CreateHardLinkW(newname, oldname, nullptr))
+    return 0;
+  return set_errno();
+}
+
+inline int remove(const wchar_t* path) {
+  detail::WinHandle h(path, DELETE, FILE_FLAG_OPEN_REPARSE_POINT);
+  if (!h)
+    return set_errno();
+  FILE_DISPOSITION_INFO info;
+  info.DeleteFile = TRUE;
+  if (!SetFileInformationByHandle(h, FileDispositionInfo, &info, sizeof(info)))
+    return set_errno();
+  return 0;
+}
+
+inline int truncate_handle(HANDLE h, off_t length) {
+  LARGE_INTEGER size_param;
+  size_param.QuadPart = length;
+  if (!SetFilePointerEx(h, size_param, 0, FILE_BEGIN))
+    return set_errno();
+  if (!SetEndOfFile(h))
+    return set_errno();
+  return 0;
+}
+
+inline int ftruncate(int fd, off_t length) {
+  HANDLE h = reinterpret_cast<HANDLE>(_get_osfhandle(fd));
+  return truncate_handle(h, length);
+}
+
+inline int truncate(const wchar_t* path, off_t length) {
+  detail::WinHandle h(path, GENERIC_WRITE, 0);
+  if (!h)
+    return set_errno();
+  return truncate_handle(h, length);
+}
+
+inline int rename(const wchar_t* from, const wchar_t* to) {
+  if (!(MoveFileExW(from, to, MOVEFILE_COPY_ALLOWED | MOVEFILE_REPLACE_EXISTING | MOVEFILE_WRITE_THROUGH)))
+    return set_errno();
+  return 0;
+}
+
+inline int chdir(const wchar_t* path) {
+  if (!SetCurrentDirectoryW(path))
+    return set_errno();
+  return 0;
+}
+
+struct StatVFS {
+  uint64_t f_frsize;
+  uint64_t f_blocks;
+  uint64_t f_bfree;
+  uint64_t f_bavail;
+};
+
+inline int statvfs(const wchar_t* p, StatVFS* buf) {
+  path dir = p;
+  while (true) {
+    error_code local_ec;
+    const file_status st = status(dir, local_ec);
+    if (!exists(st) || is_directory(st))
+      break;
+    path parent = dir.parent_path();
+    if (parent == dir) {
+      errno = ENOENT;
+      return -1;
+    }
+    dir = parent;
+  }
+  ULARGE_INTEGER free_bytes_available_to_caller, total_number_of_bytes, total_number_of_free_bytes;
+  if (!GetDiskFreeSpaceExW(
+          dir.c_str(), &free_bytes_available_to_caller, &total_number_of_bytes, &total_number_of_free_bytes))
+    return set_errno();
+  buf->f_frsize = 1;
+  buf->f_blocks = total_number_of_bytes.QuadPart;
+  buf->f_bfree  = total_number_of_free_bytes.QuadPart;
+  buf->f_bavail = free_bytes_available_to_caller.QuadPart;
+  return 0;
+}
+
+inline wchar_t* getcwd([[maybe_unused]] wchar_t* in_buf, [[maybe_unused]] size_t in_size) {
+  // Only expected to be used with us allocating the buffer.
+  _LIBCPP_ASSERT_INTERNAL(in_buf == nullptr, "Windows getcwd() assumes in_buf==nullptr");
+  _LIBCPP_ASSERT_INTERNAL(in_size == 0, "Windows getcwd() assumes in_size==0");
+
+  size_t buff_size = MAX_PATH + 10;
+  std::unique_ptr<wchar_t, decltype(&::free)> buff(static_cast<wchar_t*>(malloc(buff_size * sizeof(wchar_t))), &::free);
+  DWORD retval = GetCurrentDirectoryW(buff_size, buff.get());
+  if (retval > buff_size) {
+    buff_size = retval;
+    buff.reset(static_cast<wchar_t*>(malloc(buff_size * sizeof(wchar_t))));
+    retval = GetCurrentDirectoryW(buff_size, buff.get());
+  }
+  if (!retval) {
+    set_errno();
+    return nullptr;
+  }
+  return buff.release();
+}
+
+inline wchar_t* realpath(const wchar_t* path, [[maybe_unused]] wchar_t* resolved_name) {
+  // Only expected to be used with us allocating the buffer.
+  _LIBCPP_ASSERT_INTERNAL(resolved_name == nullptr, "Windows realpath() assumes a null resolved_name");
+
+  WinHandle h(path, FILE_READ_ATTRIBUTES, 0);
+  if (!h) {
+    set_errno();
+    return nullptr;
+  }
+  size_t buff_size = MAX_PATH + 10;
+  std::unique_ptr<wchar_t, decltype(&::free)> buff(static_cast<wchar_t*>(malloc(buff_size * sizeof(wchar_t))), &::free);
+  DWORD retval = GetFinalPathNameByHandleW(h, buff.get(), buff_size, FILE_NAME_NORMALIZED | VOLUME_NAME_DOS);
+  if (retval > buff_size) {
+    buff_size = retval;
+    buff.reset(static_cast<wchar_t*>(malloc(buff_size * sizeof(wchar_t))));
+    retval = GetFinalPathNameByHandleW(h, buff.get(), buff_size, FILE_NAME_NORMALIZED | VOLUME_NAME_DOS);
+  }
+  if (!retval) {
+    set_errno();
+    return nullptr;
+  }
+  wchar_t* ptr = buff.get();
+  if (!wcsncmp(ptr, L"\\\\?\\", 4)) {
+    if (ptr[5] == ':') { // \\?\X: -> X:
+      memmove(&ptr[0], &ptr[4], (wcslen(&ptr[4]) + 1) * sizeof(wchar_t));
+    } else if (!wcsncmp(&ptr[4], L"UNC\\", 4)) { // \\?\UNC\server -> \\server
+      wcscpy(&ptr[0], L"\\\\");
+      memmove(&ptr[2], &ptr[8], (wcslen(&ptr[8]) + 1) * sizeof(wchar_t));
+    }
+  }
+  return buff.release();
+}
+
+#  define AT_FDCWD -1
+#  define AT_SYMLINK_NOFOLLOW 1
+using ModeT = int;
+
+inline int fchmod_handle(HANDLE h, int perms) {
+  FILE_BASIC_INFO basic;
+  if (!GetFileInformationByHandleEx(h, FileBasicInfo, &basic, sizeof(basic)))
+    return set_errno();
+  DWORD orig_attributes = basic.FileAttributes;
+  basic.FileAttributes &= ~FILE_ATTRIBUTE_READONLY;
+  if ((perms & 0222) == 0)
+    basic.FileAttributes |= FILE_ATTRIBUTE_READONLY;
+  if (basic.FileAttributes != orig_attributes && !SetFileInformationByHandle(h, FileBasicInfo, &basic, sizeof(basic)))
+    return set_errno();
+  return 0;
+}
+
+inline int fchmodat(int /*fd*/, const wchar_t* path, int perms, int flag) {
+  DWORD attributes = GetFileAttributesW(path);
+  if (attributes == INVALID_FILE_ATTRIBUTES)
+    return set_errno();
+  if (attributes & FILE_ATTRIBUTE_REPARSE_POINT && !(flag & AT_SYMLINK_NOFOLLOW)) {
+    // If the file is a symlink, and we are supposed to operate on the target
+    // of the symlink, we need to open a handle to it, without the
+    // FILE_FLAG_OPEN_REPARSE_POINT flag, to open the destination of the
+    // symlink, and operate on it via the handle.
+    detail::WinHandle h(path, FILE_READ_ATTRIBUTES | FILE_WRITE_ATTRIBUTES, 0);
+    if (!h)
+      return set_errno();
+    return fchmod_handle(h, perms);
+  } else {
+    // For a non-symlink, or if operating on the symlink itself instead of
+    // its target, we can use SetFileAttributesW, saving a few calls.
+    DWORD orig_attributes = attributes;
+    attributes &= ~FILE_ATTRIBUTE_READONLY;
+    if ((perms & 0222) == 0)
+      attributes |= FILE_ATTRIBUTE_READONLY;
+    if (attributes != orig_attributes && !SetFileAttributesW(path, attributes))
+      return set_errno();
+  }
+  return 0;
+}
+
+inline int fchmod(int fd, int perms) {
+  HANDLE h = reinterpret_cast<HANDLE>(_get_osfhandle(fd));
+  return fchmod_handle(h, perms);
+}
+
+#  define MAX_SYMLINK_SIZE MAXIMUM_REPARSE_DATA_BUFFER_SIZE
+using SSizeT = ::int64_t;
+
+inline SSizeT readlink(const wchar_t* path, wchar_t* ret_buf, size_t bufsize) {
+  uint8_t buf[MAXIMUM_REPARSE_DATA_BUFFER_SIZE];
+  detail::WinHandle h(path, FILE_READ_ATTRIBUTES, FILE_FLAG_OPEN_REPARSE_POINT);
+  if (!h)
+    return set_errno();
+  DWORD out;
+  if (!DeviceIoControl(h, FSCTL_GET_REPARSE_POINT, nullptr, 0, buf, sizeof(buf), &out, 0))
+    return set_errno();
+  const auto* reparse    = reinterpret_cast<LIBCPP_REPARSE_DATA_BUFFER*>(buf);
+  size_t path_buf_offset = offsetof(LIBCPP_REPARSE_DATA_BUFFER, SymbolicLinkReparseBuffer.PathBuffer[0]);
+  if (out < path_buf_offset) {
+    errno = EINVAL;
+    return -1;
+  }
+  if (reparse->ReparseTag != IO_REPARSE_TAG_SYMLINK) {
+    errno = EINVAL;
+    return -1;
+  }
+  const auto& symlink = reparse->SymbolicLinkReparseBuffer;
+  unsigned short name_offset, name_length;
+  if (symlink.PrintNameLength == 0) {
+    name_offset = symlink.SubstituteNameOffset;
+    name_length = symlink.SubstituteNameLength;
+  } else {
+    name_offset = symlink.PrintNameOffset;
+    name_length = symlink.PrintNameLength;
+  }
+  // name_offset/length are expressed in bytes, not in wchar_t
+  if (path_buf_offset + name_offset + name_length > out) {
+    errno = EINVAL;
+    return -1;
+  }
+  if (name_length / sizeof(wchar_t) > bufsize) {
+    errno = ENOMEM;
+    return -1;
+  }
+  memcpy(ret_buf, &symlink.PathBuffer[name_offset / sizeof(wchar_t)], name_length);
+  return name_length / sizeof(wchar_t);
+}
+
+#else
+inline int symlink_file(const char* oldname, const char* newname) { return ::symlink(oldname, newname); }
+inline int symlink_dir(const char* oldname, const char* newname) { return ::symlink(oldname, newname); }
+using ::chdir;
+using ::fchmod;
+#  if defined(AT_SYMLINK_NOFOLLOW) && defined(AT_FDCWD)
+using ::fchmodat;
+#  endif
+using ::fstat;
+using ::ftruncate;
+using ::getcwd;
+using ::link;
+using ::lstat;
+using ::mkdir;
+using ::readlink;
+using ::realpath;
+using ::remove;
+using ::rename;
+using ::stat;
+using ::statvfs;
+using ::truncate;
+
+#  define O_BINARY 0
+
+using StatVFS = struct statvfs;
+using ModeT   = ::mode_t;
+using SSizeT  = ::ssize_t;
+
+#endif
+
+} // end namespace detail
+
+_LIBCPP_END_NAMESPACE_FILESYSTEM
+
+#endif // POSIX_COMPAT_H

third_party/libcxx/fs/time_utils.h

@@ -0,0 +1,351 @@
+//===----------------------------------------------------------------------===////
+//
+// 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 FILESYSTEM_TIME_UTILS_H
+#define FILESYSTEM_TIME_UTILS_H
+
+#include <__config>
+#include <array>
+#include <chrono>
+#include <filesystem>
+#include <limits>
+#include <ratio>
+#include <system_error>
+#include <type_traits>
+#include <utility>
+
+#include "error.h"
+#include "format_string.h"
+
+#if defined(_LIBCPP_WIN32API)
+#  define WIN32_LEAN_AND_MEAN
+#  define NOMINMAX
+#  include <windows.h>
+#else
+#  include <fcntl.h>
+#  include <sys/stat.h>
+#  include <sys/time.h> // for ::utimes as used in __last_write_time
+#endif
+
+// We can use the presence of UTIME_OMIT to detect platforms that provide utimensat.
+#if defined(UTIME_OMIT)
+#  define _LIBCPP_USE_UTIMENSAT
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+
+namespace detail {
+
+#if defined(_LIBCPP_WIN32API)
+// Various C runtime versions (UCRT, or the legacy msvcrt.dll used by
+// some mingw toolchains) provide different stat function implementations,
+// with a number of limitations with respect to what we want from the
+// stat function. Instead provide our own which does exactly what we want,
+// along with our own stat structure and flag macros.
+
+struct TimeSpec {
+  int64_t tv_sec;
+  int64_t tv_nsec;
+};
+struct StatT {
+  unsigned st_mode;
+  TimeSpec st_atim;
+  TimeSpec st_mtim;
+  uint64_t st_dev; // FILE_ID_INFO::VolumeSerialNumber
+  struct FileIdStruct {
+    unsigned char id[16]; // FILE_ID_INFO::FileId
+    bool operator==(const FileIdStruct& other) const {
+      for (int i = 0; i < 16; i++)
+        if (id[i] != other.id[i])
+          return false;
+      return true;
+    }
+  } st_ino;
+  uint32_t st_nlink;
+  uintmax_t st_size;
+};
+
+// There were 369 years and 89 leap days from the Windows epoch
+// (1601) to the Unix epoch (1970).
+#  define FILE_TIME_OFFSET_SECS (uint64_t(369 * 365 + 89) * (24 * 60 * 60))
+
+inline TimeSpec filetime_to_timespec(LARGE_INTEGER li) {
+  TimeSpec ret;
+  ret.tv_sec  = li.QuadPart / 10000000 - FILE_TIME_OFFSET_SECS;
+  ret.tv_nsec = (li.QuadPart % 10000000) * 100;
+  return ret;
+}
+
+inline TimeSpec filetime_to_timespec(FILETIME ft) {
+  LARGE_INTEGER li;
+  li.LowPart  = ft.dwLowDateTime;
+  li.HighPart = ft.dwHighDateTime;
+  return filetime_to_timespec(li);
+}
+
+inline FILETIME timespec_to_filetime(TimeSpec ts) {
+  LARGE_INTEGER li;
+  li.QuadPart = ts.tv_nsec / 100 + (ts.tv_sec + FILE_TIME_OFFSET_SECS) * 10000000;
+  FILETIME ft;
+  ft.dwLowDateTime  = li.LowPart;
+  ft.dwHighDateTime = li.HighPart;
+  return ft;
+}
+
+#else
+using TimeSpec = struct timespec;
+using TimeVal  = struct timeval;
+using StatT    = struct stat;
+
+inline TimeVal make_timeval(TimeSpec const& ts) {
+  using namespace chrono;
+  auto Convert = [](long nsec) {
+    using int_type = decltype(std::declval<TimeVal>().tv_usec);
+    auto dur       = duration_cast<microseconds>(nanoseconds(nsec)).count();
+    return static_cast<int_type>(dur);
+  };
+  TimeVal TV = {};
+  TV.tv_sec  = ts.tv_sec;
+  TV.tv_usec = Convert(ts.tv_nsec);
+  return TV;
+}
+#endif
+
+using chrono::duration;
+using chrono::duration_cast;
+
+template <class FileTimeT, class TimeT, bool IsFloat = is_floating_point<typename FileTimeT::rep>::value>
+struct time_util_base {
+  using rep             = typename FileTimeT::rep;
+  using fs_duration     = typename FileTimeT::duration;
+  using fs_seconds      = duration<rep>;
+  using fs_nanoseconds  = duration<rep, nano>;
+  using fs_microseconds = duration<rep, micro>;
+
+  static constexpr rep max_seconds = duration_cast<fs_seconds>(FileTimeT::duration::max()).count();
+
+  static constexpr rep max_nsec =
+      duration_cast<fs_nanoseconds>(FileTimeT::duration::max() - fs_seconds(max_seconds)).count();
+
+  static constexpr rep min_seconds = duration_cast<fs_seconds>(FileTimeT::duration::min()).count();
+
+  static constexpr rep min_nsec_timespec =
+      duration_cast<fs_nanoseconds>((FileTimeT::duration::min() - fs_seconds(min_seconds)) + fs_seconds(1)).count();
+
+private:
+  static constexpr fs_duration get_min_nsecs() {
+    return duration_cast<fs_duration>(fs_nanoseconds(min_nsec_timespec) - duration_cast<fs_nanoseconds>(fs_seconds(1)));
+  }
+  // Static assert that these values properly round trip.
+  static_assert(fs_seconds(min_seconds) + get_min_nsecs() == FileTimeT::duration::min(), "value doesn't roundtrip");
+
+  static constexpr bool check_range() {
+    // This kinda sucks, but it's what happens when we don't have __int128_t.
+    if (sizeof(TimeT) == sizeof(rep)) {
+      typedef duration<long long, ratio<3600 * 24 * 365> > Years;
+      return duration_cast<Years>(fs_seconds(max_seconds)) > Years(250) &&
+             duration_cast<Years>(fs_seconds(min_seconds)) < Years(-250);
+    }
+    return max_seconds >= numeric_limits<TimeT>::max() && min_seconds <= numeric_limits<TimeT>::min();
+  }
+#if _LIBCPP_STD_VER >= 14
+  static_assert(check_range(), "the representable range is unacceptable small");
+#endif
+};
+
+template <class FileTimeT, class TimeT>
+struct time_util_base<FileTimeT, TimeT, true> {
+  using rep             = typename FileTimeT::rep;
+  using fs_duration     = typename FileTimeT::duration;
+  using fs_seconds      = duration<rep>;
+  using fs_nanoseconds  = duration<rep, nano>;
+  using fs_microseconds = duration<rep, micro>;
+
+  static const rep max_seconds;
+  static const rep max_nsec;
+  static const rep min_seconds;
+  static const rep min_nsec_timespec;
+};
+
+template <class FileTimeT, class TimeT>
+const typename FileTimeT::rep time_util_base<FileTimeT, TimeT, true>::max_seconds =
+    duration_cast<fs_seconds>(FileTimeT::duration::max()).count();
+
+template <class FileTimeT, class TimeT>
+const typename FileTimeT::rep time_util_base<FileTimeT, TimeT, true>::max_nsec =
+    duration_cast<fs_nanoseconds>(FileTimeT::duration::max() - fs_seconds(max_seconds)).count();
+
+template <class FileTimeT, class TimeT>
+const typename FileTimeT::rep time_util_base<FileTimeT, TimeT, true>::min_seconds =
+    duration_cast<fs_seconds>(FileTimeT::duration::min()).count();
+
+template <class FileTimeT, class TimeT>
+const typename FileTimeT::rep time_util_base<FileTimeT, TimeT, true>::min_nsec_timespec =
+    duration_cast<fs_nanoseconds>((FileTimeT::duration::min() - fs_seconds(min_seconds)) + fs_seconds(1)).count();
+
+template <class FileTimeT, class TimeT, class TimeSpecT>
+struct time_util : time_util_base<FileTimeT, TimeT> {
+  using Base = time_util_base<FileTimeT, TimeT>;
+  using Base::max_nsec;
+  using Base::max_seconds;
+  using Base::min_nsec_timespec;
+  using Base::min_seconds;
+
+  using typename Base::fs_duration;
+  using typename Base::fs_microseconds;
+  using typename Base::fs_nanoseconds;
+  using typename Base::fs_seconds;
+
+public:
+  template <class CType, class ChronoType>
+  static constexpr bool checked_set(CType* out, ChronoType time) {
+    using Lim = numeric_limits<CType>;
+    if (time > Lim::max() || time < Lim::min())
+      return false;
+    *out = static_cast<CType>(time);
+    return true;
+  }
+
+  static constexpr bool is_representable(TimeSpecT tm) {
+    if (tm.tv_sec >= 0) {
+      return tm.tv_sec < max_seconds || (tm.tv_sec == max_seconds && tm.tv_nsec <= max_nsec);
+    } else if (tm.tv_sec == (min_seconds - 1)) {
+      return tm.tv_nsec >= min_nsec_timespec;
+    } else {
+      return tm.tv_sec >= min_seconds;
+    }
+  }
+
+  static constexpr bool is_representable(FileTimeT tm) {
+    auto secs  = duration_cast<fs_seconds>(tm.time_since_epoch());
+    auto nsecs = duration_cast<fs_nanoseconds>(tm.time_since_epoch() - secs);
+    if (nsecs.count() < 0) {
+      secs  = secs + fs_seconds(1);
+      nsecs = nsecs + fs_seconds(1);
+    }
+    using TLim = numeric_limits<TimeT>;
+    if (secs.count() >= 0)
+      return secs.count() <= TLim::max();
+    return secs.count() >= TLim::min();
+  }
+
+  static constexpr FileTimeT convert_from_timespec(TimeSpecT tm) {
+    if (tm.tv_sec >= 0 || tm.tv_nsec == 0) {
+      return FileTimeT(fs_seconds(tm.tv_sec) + duration_cast<fs_duration>(fs_nanoseconds(tm.tv_nsec)));
+    } else { // tm.tv_sec < 0
+      auto adj_subsec = duration_cast<fs_duration>(fs_seconds(1) - fs_nanoseconds(tm.tv_nsec));
+      auto Dur        = fs_seconds(tm.tv_sec + 1) - adj_subsec;
+      return FileTimeT(Dur);
+    }
+  }
+
+  template <class SubSecT>
+  static constexpr bool set_times_checked(TimeT* sec_out, SubSecT* subsec_out, FileTimeT tp) {
+    auto dur        = tp.time_since_epoch();
+    auto sec_dur    = duration_cast<fs_seconds>(dur);
+    auto subsec_dur = duration_cast<fs_nanoseconds>(dur - sec_dur);
+    // The tv_nsec and tv_usec fields must not be negative so adjust accordingly
+    if (subsec_dur.count() < 0) {
+      if (sec_dur.count() > min_seconds) {
+        sec_dur    = sec_dur - fs_seconds(1);
+        subsec_dur = subsec_dur + fs_seconds(1);
+      } else {
+        subsec_dur = fs_nanoseconds::zero();
+      }
+    }
+    return checked_set(sec_out, sec_dur.count()) && checked_set(subsec_out, subsec_dur.count());
+  }
+  static constexpr bool convert_to_timespec(TimeSpecT& dest, FileTimeT tp) {
+    if (!is_representable(tp))
+      return false;
+    return set_times_checked(&dest.tv_sec, &dest.tv_nsec, tp);
+  }
+};
+
+#if defined(_LIBCPP_WIN32API)
+using fs_time = time_util<file_time_type, int64_t, TimeSpec>;
+#else
+using fs_time = time_util<file_time_type, time_t, TimeSpec>;
+#endif
+
+#if defined(__APPLE__)
+inline TimeSpec extract_mtime(StatT const& st) { return st.st_mtimespec; }
+inline TimeSpec extract_atime(StatT const& st) { return st.st_atimespec; }
+#elif defined(__MVS__)
+inline TimeSpec extract_mtime(StatT const& st) {
+  TimeSpec TS = {st.st_mtime, 0};
+  return TS;
+}
+inline TimeSpec extract_atime(StatT const& st) {
+  TimeSpec TS = {st.st_atime, 0};
+  return TS;
+}
+#elif defined(_AIX)
+inline TimeSpec extract_mtime(StatT const& st) {
+  TimeSpec TS = {st.st_mtime, st.st_mtime_n};
+  return TS;
+}
+inline TimeSpec extract_atime(StatT const& st) {
+  TimeSpec TS = {st.st_atime, st.st_atime_n};
+  return TS;
+}
+#else
+inline TimeSpec extract_mtime(StatT const& st) { return st.st_mtim; }
+inline TimeSpec extract_atime(StatT const& st) { return st.st_atim; }
+#endif
+
+#ifndef _LIBCPP_HAS_NO_FILESYSTEM
+
+#  if !defined(_LIBCPP_WIN32API)
+inline bool posix_utimes(const path& p, std::array<TimeSpec, 2> const& TS, error_code& ec) {
+  TimeVal ConvertedTS[2] = {make_timeval(TS[0]), make_timeval(TS[1])};
+  if (::utimes(p.c_str(), ConvertedTS) == -1) {
+    ec = capture_errno();
+    return true;
+  }
+  return false;
+}
+
+#    if defined(_LIBCPP_USE_UTIMENSAT)
+inline bool posix_utimensat(const path& p, std::array<TimeSpec, 2> const& TS, error_code& ec) {
+  if (::utimensat(AT_FDCWD, p.c_str(), TS.data(), 0) == -1) {
+    ec = capture_errno();
+    return true;
+  }
+  return false;
+}
+#    endif
+
+inline bool set_file_times(const path& p, std::array<TimeSpec, 2> const& TS, error_code& ec) {
+#    if !defined(_LIBCPP_USE_UTIMENSAT)
+  return posix_utimes(p, TS, ec);
+#    else
+  return posix_utimensat(p, TS, ec);
+#    endif
+}
+
+#  endif // !_LIBCPP_WIN32API
+
+inline file_time_type __extract_last_write_time(const path& p, const StatT& st, error_code* ec) {
+  using detail::fs_time;
+  ErrorHandler<file_time_type> err("last_write_time", ec, &p);
+
+  auto ts = detail::extract_mtime(st);
+  if (!fs_time::is_representable(ts))
+    return err.report(errc::value_too_large);
+
+  return fs_time::convert_from_timespec(ts);
+}
+
+#endif // !_LIBCPP_HAS_NO_FILESYSTEM
+
+} // end namespace detail
+
+_LIBCPP_END_NAMESPACE_FILESYSTEM
+
+#endif // FILESYSTEM_TIME_UTILS_H