Add detailed notes on Win32 API limitations for dirfile semantics in …

include/fast_io_core.h

@@ -9,10 +9,13 @@
 #if !defined(__cpp_concepts)
 #error "fast_io requires at least C++20 standard compiler."
 #else
+
+#include <version>
+#include <cstdint>
+#include <cstddef>
+#include <climits>
 #include <bit>
 #include <limits>
-#include <cstdint>
-#include <version>
 
 #if __cpp_lib_three_way_comparison >= 201907L
 #include <compare>

include/fast_io_core_impl/char_category/char_category.h

@@ -1795,7 +1795,7 @@ inline constexpr bool is_html_whitespace_wide_impl(wchar_t ch) noexcept
 	};
 }
 
-inline constexpr bool is_dos_path_invalid_character_impl(char32_t ch) noexcept
+inline constexpr bool is_dos_file_invalid_character_impl(char32_t ch) noexcept
 {
 	if (ch < static_cast<char32_t>(32u))
 	{
@@ -1926,15 +1926,15 @@ To do: to_c_fullwidth
 */
 
 template <::std::integral T>
-inline constexpr bool is_dos_path_invalid_character(T ch) noexcept
+inline constexpr bool is_dos_file_invalid_character(T ch) noexcept
 {
 	if constexpr (::std::signed_integral<T>)
 	{
-		return ::fast_io::char_category::details::is_dos_path_invalid_character_impl(static_cast<char32_t>(static_cast<::std::make_unsigned_t<T>>(ch)));
+		return ::fast_io::char_category::details::is_dos_file_invalid_character_impl(static_cast<char32_t>(static_cast<::std::make_unsigned_t<T>>(ch)));
 	}
 	else
 	{
-		return ::fast_io::char_category::details::is_dos_path_invalid_character_impl(static_cast<char32_t>(ch));
+		return ::fast_io::char_category::details::is_dos_file_invalid_character_impl(static_cast<char32_t>(ch));
 	}
 }
 

include/fast_io_core_impl/char_category/char_category_traits.h

@@ -19,7 +19,7 @@ enum class char_category_family : ::std::uint_least32_t
 	c_space,                    // Whitespace characters (space, tab, newline, etc.)
 	c_upper,                    // Uppercase alphabetic characters
 	c_xdigit,                   // Hexadecimal digits (0-9, A-F, a-f)
-	dos_path_invalid_character, // DOS Path invalid character
+	dos_file_invalid_character, // DOS Path invalid character
 	html_whitespace             // HTML whitespace
 };
 
@@ -96,9 +96,9 @@ class char_category_traits
 		{
 			ret = ::fast_io::char_category::is_c_fullwidth(ch);
 		}
-		else if constexpr (fam == ::fast_io::char_category::char_category_family::dos_path_invalid_character)
+		else if constexpr (fam == ::fast_io::char_category::char_category_family::dos_file_invalid_character)
 		{
-			ret = ::fast_io::char_category::is_dos_path_invalid_character(ch);
+			ret = ::fast_io::char_category::is_dos_file_invalid_character(ch);
 		}
 		if constexpr (negate)
 		{
@@ -192,7 +192,7 @@ using c_punct = ::fast_io::char_category::char_category_traits<::fast_io::char_c
 using c_space = ::fast_io::char_category::char_category_traits<::fast_io::char_category::char_category_family::c_space, false>;
 using c_upper = ::fast_io::char_category::char_category_traits<::fast_io::char_category::char_category_family::c_upper, false>;
 using c_xdigit = ::fast_io::char_category::char_category_traits<::fast_io::char_category::char_category_family::c_xdigit, false>;
-using dos_path_invalid_character = ::fast_io::char_category::char_category_traits<::fast_io::char_category::char_category_family::dos_path_invalid_character, false>;
+using dos_file_invalid_character = ::fast_io::char_category::char_category_traits<::fast_io::char_category::char_category_family::dos_file_invalid_character, false>;
 using html_whitespace = ::fast_io::char_category::char_category_traits<::fast_io::char_category::char_category_family::html_whitespace, false>;
 
 
@@ -210,7 +210,7 @@ using not_c_punct = ::fast_io::char_category::char_category_traits<::fast_io::ch
 using not_c_space = ::fast_io::char_category::char_category_traits<::fast_io::char_category::char_category_family::c_space, true>;
 using not_c_upper = ::fast_io::char_category::char_category_traits<::fast_io::char_category::char_category_family::c_upper, true>;
 using not_c_xdigit = ::fast_io::char_category::char_category_traits<::fast_io::char_category::char_category_family::c_xdigit, true>;
-using not_dos_path_invalid_character = ::fast_io::char_category::char_category_traits<::fast_io::char_category::char_category_family::dos_path_invalid_character, true>;
+using not_dos_file_invalid_character = ::fast_io::char_category::char_category_traits<::fast_io::char_category::char_category_family::dos_file_invalid_character, true>;
 using not_html_whitespace = ::fast_io::char_category::char_category_traits<::fast_io::char_category::char_category_family::html_whitespace, true>;
 
 namespace details

include/fast_io_device.h

@@ -29,6 +29,20 @@ using dir_file = directory_file_wrapper<
 #endif
 	>;
 
+// Note:
+// The Win32 API layer is not well-suited for precise "dirfile" semantics,
+// because it abstracts away the underlying NT object types. Unlike the NT I/O
+// manager (where FILE_DIRECTORY_FILE and FILE_NON_DIRECTORY_FILE flags enforce
+// strict open-type constraints), Win32’s CreateFileW does not distinguish
+// between files and directories unless explicitly checked afterwards.
+//
+// FILE_FLAG_BACKUP_SEMANTICS merely *permits* opening a directory handle,
+// but does not *require* the target to be a directory. Similarly, adding
+// FILE_ATTRIBUTE_DIRECTORY has no enforcement effect — it's only a metadata hint.
+// Therefore, to emulate dirfile-style correctness, one must explicitly query
+// the object type (e.g., via GetFileInformationByHandle or GetFileAttributes)
+// after opening the handle.
+
 /*
 template region
 */

include/fast_io_driver/install_path/impl.h

@@ -2,15 +2,15 @@
 
 #include"install_path.h"
 
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__CYGWIN__)
 #include "argv0_null.h"
 #else
 #include "argv0.h"
 #endif
 
-#if (defined(__linux) || defined(__linux__) || defined(__gnu_linux__)) || defined(__CYGWIN__) || defined(__sun)
+#if (defined(__linux) || defined(__linux__) || defined(__gnu_linux__)) || defined(__sun)
 #include "linux.h"
-#elif defined(_WIN32)
+#elif defined(_WIN32) || defined(__CYGWIN__)
 #if defined(_WIN32_WINDOWS)
 #include "win32_9xa.h"
 #else

include/fast_io_dsal/impl/misc/push_macros.h

@@ -14,7 +14,14 @@
 #undef move
 
 #pragma push_macro("new")
+#if __GNUC__ >= 16
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wkeyword-macro"
 #undef new
+#pragma GCC diagnostic pop
+#else
+#undef new
+#endif
 
 #pragma push_macro("refresh")
 #undef refresh

include/fast_io_hosted/dll/win32.h

@@ -98,7 +98,7 @@ inline void *create_win32_dll_9xa(char const *filename) // 9x kernel does not su
 inline void *create_win32_dll_ntw(char16_t const *filename, [[maybe_unused]] dll_mode mode)
 {
 	auto hmodule{
-#if _WIN32_WINNT <= 0x0500
+#if (defined(_WIN32_WINNT) && _WIN32_WINNT <= 0x0500)
 		// Windows 2000 does not support Ex apis
 		::fast_io::win32::LoadLibraryW(filename)
 #else

include/fast_io_hosted/filesystem/dos.h

@@ -60,6 +60,8 @@ namespace posix
 // extern char const* my_dos_get_fd_name(int) noexcept __asm__("___get_fd_name");
 extern DIR *my_dos_opendir(char const *) noexcept __asm__("_opendir");
 
+extern int my_dos_closedir(DIR *) noexcept __asm__("_closedir");
+
 inline DIR *my_dos_fdopendir(int fd) noexcept
 {
 	return my_dos_opendir(::fast_io::noexcept_call(::__get_fd_name, fd));
@@ -69,6 +71,16 @@ inline DIR *my_dos_fdopendir(int fd) noexcept
 namespace details
 {
 
+inline void check_dos_fd_is_dir(int fd)
+{
+	auto const dir{::fast_io::posix::my_dos_fdopendir(fd)};
+	if (dir == nullptr) [[unlikely]]
+	{
+		throw_posix_error(ENOTDIR);
+	}
+	::fast_io::posix::my_dos_closedir(dir);
+}
+
 inline dos_DIR sys_dup_dir(dos_DIR dirp)
 {
 	if (dirp.dirp == nullptr) [[unlikely]]
@@ -127,7 +139,7 @@ class dos_directory_file FAST_IO_TRIVIALLY_RELOCATABLE_IF_ELIGIBLE : public dos_
 		auto newdir{details::sys_dup_dir(other.dirp)};
 		if (this->dirp.dirp) [[likely]]
 		{
-			noexcept_call(::closedir, this->dirp.dirp);
+			::fast_io::posix::my_dos_closedir(this->dirp.dirp);
 		}
 		if (this->dirp.fd != -1) [[likely]]
 		{
@@ -149,7 +161,7 @@ class dos_directory_file FAST_IO_TRIVIALLY_RELOCATABLE_IF_ELIGIBLE : public dos_
 		}
 		if (this->dirp.dirp) [[likely]]
 		{
-			noexcept_call(::closedir, this->dirp.dirp);
+			::fast_io::posix::my_dos_closedir(this->dirp.dirp);
 		}
 		if (this->dirp.fd != -1) [[likely]]
 		{
@@ -163,7 +175,7 @@ class dos_directory_file FAST_IO_TRIVIALLY_RELOCATABLE_IF_ELIGIBLE : public dos_
 	{
 		if (this->dirp.dirp) [[likely]]
 		{
-			noexcept_call(::closedir, this->dirp.dirp);
+			::fast_io::posix::my_dos_closedir(this->dirp.dirp);		
 		}
 		if (this->dirp.fd != -1) [[likely]]
 		{
@@ -177,7 +189,7 @@ class dos_directory_file FAST_IO_TRIVIALLY_RELOCATABLE_IF_ELIGIBLE : public dos_
 		if (*this) [[likely]]
 		{
 			int fd_to_close{this->dirp.fd};
-			int ret{noexcept_call(::closedir, this->dirp.dirp)};
+			int ret{::fast_io::posix::my_dos_closedir(this->dirp.dirp)};
 			this->dirp.dirp = nullptr;
 			this->dirp.fd = -1;
 			if (fd_to_close != -1)
@@ -195,7 +207,7 @@ class dos_directory_file FAST_IO_TRIVIALLY_RELOCATABLE_IF_ELIGIBLE : public dos_
 	{
 		if (this->dirp.dirp) [[likely]]
 		{
-			noexcept_call(::closedir, this->dirp.dirp);
+			::fast_io::posix::my_dos_closedir(this->dirp.dirp);
 		}
 		if (this->dirp.fd != -1) [[likely]]
 		{

include/fast_io_hosted/filesystem/nt_at.h

@@ -93,15 +93,21 @@ inline void nt_unlinkat_impl(void *dirhd, char16_t const *path_c_str, ::std::siz
 template <bool zw>
 inline void nt_mkdirat_impl(void *dirhd, char16_t const *path_c_str, ::std::size_t path_size, perms pm, bool kernel)
 {
-	constexpr fast_io::win32::nt::details::nt_open_mode create_dir_mode{
-		fast_io::win32::nt::details::calculate_nt_open_mode(
-			{fast_io::open_mode::creat | fast_io::open_mode::directory})};
-	auto m_dir_mode{create_dir_mode};
+	nt_open_mode m_dir_mode{
+		.DesiredAccess = 0x00100000 | 0x0001, // SYNCHRONIZE | FILE_LIST_DIRECTORY
+		.FileAttributes = 0x80,               // FILE_ATTRIBUTE_NORMAL
+		.ShareAccess = 0x00000003,            // FILE_SHARE_READ | FILE_SHARE_WRITE
+		.CreateDisposition = 0x00000002,      // CREATE_NEW	=>	FILE_CREATE		(0x00000002)
+		.CreateOptions = 0x00004021           // FILE_DIRECTORY_FILE | FILE_SYNCHRONOUS_IO_NONALERT | FILE_OPEN_FOR_BACKUP_INTENT
+	};
+
 	if ((pm & perms::owner_write) == perms::none)
 	{
 		m_dir_mode.FileAttributes |= 0x00000001; // FILE_ATTRIBUTE_READONLY
 	}
+
 	auto status{nt_close<zw>(nt_call_determine_kernel_callback(dirhd, path_c_str, path_size, kernel, nt_create_callback<zw>{m_dir_mode}))};
+
 	if (status)
 	{
 		throw_nt_error(status);
@@ -775,7 +781,7 @@ inline ::fast_io::details::basic_ct_string<char_type> nt_readlinkat_impl(void *d
 		.FileAttributes = 0x80,               // FILE_ATTRIBUTE_NORMAL
 		.ShareAccess = 0x00000007,            // FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE
 		.CreateDisposition = 0x00000001,      // OPEN_EXISTING => FILE_OPEN
-		.CreateOptions = 0x00200000           // FILE_FLAG_OPEN_REPARSE_POINT => FILE_OPEN_REPARSE_POINT (0x00200000)
+		.CreateOptions = 0x00200000 | 0x00000020 // FILE_FLAG_OPEN_REPARSE_POINT | FILE_SYNCHRONOUS_IO_NONALERT
 	};
 
 	::fast_io::basic_nt_family_file<(zw ? nt_family::zw : nt_family::nt), char> file{

include/fast_io_hosted/filesystem/posix.h

@@ -6,14 +6,36 @@ namespace fast_io
 
 namespace details
 {
+#if defined(__CYGWIN__)
+struct my_cygwin_DIR
+{
+  /* This is first to set alignment in non _LIBC case.  */
+  unsigned long	__d_cookie;
+  struct dirent	*__d_dirent;
+  char		*__d_dirname;		/* use for internal caching */
+  ::std::int32_t	 __d_position;		/* used by telldir/seekdir */
+  int		 __d_fd;
+  ::std::uintptr_t	 __d_internal;
+  void		*__handle;
+  void		*__fh;
+  unsigned	 __flags;
+};
+
+using my_cygwin_DIR_may_alias_ptr = 
+#if __has_cpp_attribute(__gnu__::__may_alias__)
+	[[__gnu__::__may_alias__]]
+#endif
+	my_cygwin_DIR *;
+#endif
+
 inline int dirp_to_fd(DIR *dirp) noexcept
 {
 	if (dirp == nullptr)
 	{
 		return -1;
 	}
 #if defined(__CYGWIN__)
-	return dirp->__d_fd;
+	return reinterpret_cast<my_cygwin_DIR_may_alias_ptr>(dirp)->__d_fd;
 #else
 	return dirfd(dirp);
 #endif
@@ -58,7 +80,7 @@ inline DIR *sys_dup_dir(DIR *dirp)
 	}
 	auto fd{
 #if defined(__CYGWIN__)
-		dirp->__d_fd
+		reinterpret_cast<my_cygwin_DIR_may_alias_ptr>(dirp)->__d_fd
 #else
 		dirfd(dirp)
 #endif

include/fast_io_hosted/filesystem/posix_at.h

@@ -447,7 +447,7 @@ inline void posix_utimensat_impl(int dirfd, char const *path, unix_timestamp_opt
 }
 
 template<::std::integral char_type>
-inline ::fast_io::details::basic_ct_string<char_type> posix_readlinkat_impl(int dirfd, char const *pathname)
+inline ::fast_io::details::basic_ct_string<char_type> posix_readlinkat_impl([[maybe_unused]] int dirfd, [[maybe_unused]] char const *pathname)
 {
 #if defined(AT_SYMLINK_NOFOLLOW)
     using posix_ssize_t = ::std::make_signed_t<::std::size_t>;

include/fast_io_hosted/platforms/dos_filename.h

@@ -29,7 +29,7 @@ inline constexpr bool is_invalid_dos_filename_with_size(char_type const *filenam
 
 	for (; curr != end; ++curr)
 	{
-		if (auto fc{*curr}; ::fast_io::char_category::is_dos_path_invalid_character(fc)) [[unlikely]]
+		if (auto fc{*curr}; ::fast_io::char_category::is_dos_file_invalid_character(fc)) [[unlikely]]
 		{
 			return true;
 		}