Why does os.path.realpath convert c:\windows\system32 into c:/windows/syswow64?

Question

If we take a look to https://docs.python.org/3/library/pathlib.html#pathlib.Path.resolve source code we can see the routine is calling behind the curtains https://docs.python.org/3/library/os.path.html#os.path.realpath

I'm trying to really understand how os.path.realpath works in certain directories such as c:\windows\system32, ie:

>>> from pathlib import Path                                                    
>>> Path("c:/windows/system32")                                                 
WindowsPath('c:/windows/system32')                                              
>>> Path("c:/windows/system32").resolve()                                       
WindowsPath('C:/Windows/SysWOW64')                                              
>>> Path("c:/windows/system32").resolve(strict=True)                            
WindowsPath('C:/Windows/SysWOW64')                                              
>>> Path("c:/windows/system32").resolve()==Path("c:/windows/system32")          
False          

Or directories such as c:/windows/system32/openssh where you can get "unexpected results" such as below:

>>> list(Path("c:/windows/system32/openssh").resolve().glob("*"))
[]
>>> list(Path("c:/windows/system32/openssh").glob("*"))
[]

or

>>> os.listdir(r"C:\Windows\System32\OpenSSH")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
FileNotFoundError: [WinError 3] The system cannot find the path specified: 'C:\\Windows\\System32\\OpenSSH'

If you do dir /a you'll get

24/09/2022  10:03    <DIR>          System32

So you can see it's neither a SYMLINKD nor JUNCTION.

Could you explain how os.path.realpath works in these cases? Why can't i list/glob the content of that c:\windows\system32\openssh folder?

References: ntpath.py

Answer 1

On windows, os.path.realpath is using GetFinalPathNameByHandleW behind the curtains, for more info you can check here.

If we make a simple experiment to see how that routine works:

#include <windows.h>
#include <iostream>

#define MAXPATHLEN 1024

void os__getfinalpathname_impl(const std::wstring &path) {
    std::wcout << L"analizing: " << path << std::endl;

    HANDLE hFile;
    wchar_t buf[MAXPATHLEN];
    int result_length;

    hFile = CreateFileW(path.c_str(), 0, 0, NULL, OPEN_EXISTING,
                        FILE_FLAG_BACKUP_SEMANTICS, NULL);

    if (hFile == INVALID_HANDLE_VALUE) {
        std::wcout << L"CreateFileW:" << path << std::endl;
    }

    result_length =
        GetFinalPathNameByHandleW(hFile, buf, MAXPATHLEN, VOLUME_NAME_DOS);

    if (!result_length) {
        std::wcout << L"GetFinalPathNameByHandleW" << std::endl;
    }

    std::wcout << L"result: " << buf << std::endl;
}

void main(int argc, char *argv[]) {
    std::wcout << L"test1" << std::endl;
    os__getfinalpathname_impl(L"c:/windows/system32");
    std::wcout << L"test2" << std::endl;
    os__getfinalpathname_impl(L"c:\\windows\\system32");
}

If we compile it for a 32-bit target we'll get:

test1
analizing: c:/windows/system32
result: \\?\C:\Windows\SysWOW64
test2
analizing: c:\windows\system32
result: \\?\C:\Windows\SysWOW64

If we compile it for a 64-bit target we'll get:

test1
analizing: c:/windows/system32
result: \\?\C:\Windows\System32
test2
analizing: c:\windows\system32
result: \\?\C:\Windows\System32

Now, if we want to confirm the above and checking the differences in a python context, we can do that easily by just spawning a couple oneliners:

python\3.10.6-amd64\python.exe -c "from pathlib import Path; print(Path('c:/windows/system32').resolve())"
C:\Windows\System32

python\3.10.1\python.exe -c "from pathlib import Path; print(Path('c:/windows/system32').resolve())"
C:\Windows\SysWOW64

Which makes total sense accordingly what's described in the below link https://learn.microsoft.com/en-us/windows/win32/winprog64/file-system-redirector