Refactor thread start routine declaration and improve error handling in POSIX headers

- Updated `thread_start_routine` in both NT and Win32 headers to include `FAST_IO_WINSTDCALL` for better calling convention compatibility.
- Enhanced error handling in `get_module_install_path_from_argv0` by checking for a null environment path and throwing an appropriate error.
- Improved readability by initializing pointers to empty and using consistent formatting in the `argv0.h` file.
- Adjusted conditional compilation checks in `posix.h` for clearer handling of open mode flags.

Author: MacroModel

include/fast_io_driver/install_path/argv0.h

@@ -66,7 +66,7 @@ inline ::fast_io::install_path get_module_install_path_from_argv0(char const *ar
 		::fast_io::noexcept_call(::strncat, newpath2, path_separator_as_string, PATH_MAX + 256);
 		::fast_io::noexcept_call(::strncat, newpath2, argv0, PATH_MAX + 256);
 		[[maybe_unused]] auto const unused2{::fast_io::noexcept_call(::realpath, newpath2, newpath)};
-		if (auto status{::fast_io::noexcept_call(::access, newpath, F_OK)};!status)
+		if (auto status{::fast_io::noexcept_call(::access, newpath, F_OK)}; !status)
 		{
 			newpath[PATH_MAX - 1] = 0;
 			ret.module_name = ::fast_io::u8concat_fast_io(::fast_io::mnp::code_cvt_os_c_str(newpath));
@@ -91,10 +91,17 @@ inline ::fast_io::install_path get_module_install_path_from_argv0(char const *ar
 	}
 	else
 	{
-		char *saveptr;
-		char *pathitem;
-		char *save_path{::fast_io::noexcept_call(::getenv, "PATH")};
-		for (pathitem = ::fast_io::noexcept_call(::strtok_r, save_path, path_list_separator, &saveptr); pathitem;
+		char *saveptr{};
+		char *pathitem{};
+		char const *env_path{::fast_io::noexcept_call(::getenv, "PATH")};
+		if (!env_path) [[unlikely]]
+		{
+			throw_posix_error(EINVAL);
+		}
+		char pathbuf[PATH_MAX + 256 + 1]{};
+		::fast_io::noexcept_call(::strncpy, pathbuf, env_path, PATH_MAX + 256);
+
+		for (pathitem = ::fast_io::noexcept_call(::strtok_r, pathbuf, path_list_separator, &saveptr); pathitem;
 			 pathitem = ::fast_io::noexcept_call(::strtok_r, nullptr, path_list_separator, &saveptr))
 		{
 			::fast_io::noexcept_call(::strncpy, newpath2, pathitem, PATH_MAX + 256);

include/fast_io_hosted/platforms/posix.h

@@ -194,7 +194,7 @@ inline constexpr int calculate_posix_open_mode(open_mode value) noexcept
 	if ((value & open_mode::inherit) == open_mode::none)
 #ifdef O_CLOEXEC
 		mode |= O_CLOEXEC;
-#elif _O_NOINHERIT
+#elif defined(_O_NOINHERIT)
 		mode |= _O_NOINHERIT;
 #endif
 #ifdef O_BINARY

include/fast_io_hosted/threads/thread/nt.h

@@ -38,7 +38,7 @@ class nt_thread_start_routine_tuple_allocate_guard
 };
 
 template <typename Tuple, ::std::size_t... Is>
-constexpr ::std::uint_least32_t thread_start_routine(void *args) noexcept(noexcept(
+constexpr ::std::uint_least32_t FAST_IO_WINSTDCALL thread_start_routine(void *args) noexcept(noexcept(
 	::std::invoke(::fast_io::get<Is>(*reinterpret_cast<Tuple *>(args))...)))
 {
 	[[maybe_unused]] ::fast_io::win32::nt::details::nt_thread_start_routine_tuple_allocate_guard _(args);

include/fast_io_hosted/threads/thread/win32.h

@@ -38,7 +38,7 @@ class win32_thread_start_routine_tuple_allocate_guard
 };
 
 template <typename Tuple, ::std::size_t... Is>
-constexpr ::std::uint_least32_t thread_start_routine(void *args) noexcept(noexcept(
+constexpr ::std::uint_least32_t FAST_IO_WINSTDCALL thread_start_routine(void *args) noexcept(noexcept(
 	::std::invoke(::fast_io::get<Is>(*reinterpret_cast<Tuple *>(args))...)))
 {
 	[[maybe_unused]] ::fast_io::win32::details::win32_thread_start_routine_tuple_allocate_guard _(args);