[ntpath] realpath fails for broken symlinks with rooted target paths #85035

Activity

1. eryksun commented on Jun 3, 2020

   

   eryksun

   on Jun 3, 2020

   Last edited by eryksun

   ContributorAuthor

   More actions

   ntpath.realpath fails to resolve the non-strict path of a broken relative symlink if the target is a rooted path. For example:

       >>> os.readlink('symlink')
       '\\broken\\link'
       >>> os.path.realpath('symlink')
       '\\broken\\link'
   
       >>> os.path.abspath('symlink')
       'C:\\Temp\\symlink'

   The problem is that relative paths have to be specially handled by ntpath._readlink_deep, but ntpath.isabs incorrectly classifies r"\broken\link" as an absolute path. It's actually relative to the current device or drive in the access context. Other path libraries get this right, such as pathlib.Path.is_absolute and C++ path::is_absolute. The documented behavior of ntpath.isabs isn't something that we can change (i.e. "begins with a (back)slash after chopping off a potential drive letter"). So ntpath._readlink_deep needs a private implementation of isabs. For example:

       def _isabs(s):
           s = os.fspath(s)
           seps = _get_bothseps(s)
           s = s[1:2] if (s and s[0] in seps) else splitdrive(s)[1]
           return bool(s) and s[0] in seps

   This classifies UNC paths as absolute; rooted paths without a drive as relative; and otherwise depends on splitdrive() to get the root path, if any.

   ---

   Background

   The target of a relative symlink gets evaluated against the solid path that's used to access the link. A solid path contains directories and mountpoints, but no symlinks. In particular, a rooted target such as r"\spam\eggs" is relative to the root device of the solid path that's used to access the link. This may or may not be the device on which the link resides. It depends on how it's accessed. For example, if the volume that contains the symlink is accessed via its DOS device name "V:", then it resolves to r"V:\spam\eggs". Similarly, if the symlink is accessed via r"C:\Mount\VolumeSymlink", where "VolumeSymlink" is a directory symlink to "V:\\\\", then it also resolves to r"V:\spam\eggs". On the other hand, if the symlink is accessed via the mount point r"C:\Mount\VolumeMountpoint", then it resolves to r"C:\spam\eggs".
2. eryksun

   added

   3.8 (EOL)end of lifeend of life

   3.9 (EOL)end of lifeend of life

   3.10 (EOL)end of lifeend of life

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   OS-windows

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Jun 3, 2020
3. ezio-melotti

   transferred this issue fromon Apr 10, 2022
4. eryksun

   changed the title [-]ntpath.realpath fails for broken symlinks with rooted target paths[/-] [+][ntpath] realpath fails for broken symlinks with rooted target paths[/+] on Aug 8, 2022
5. serhiy-storchaka

   added this to OS issues 💻on Jul 3, 2026
6. github-project-automation

   moved this to Todo in OS issues 💻on Jul 3, 2026
7. serhiy-storchaka commented on Aug 8, 2026

   

   serhiy-storchaka

   on Aug 8, 2026

   Member

   More actions

   Fixed in 3.13 by GH-113829, which made ntpath.isabs() return False for a rooted path without a drive, so _readlink_deep() now joins such target with the location of the link.

   >>> os.readlink('symlink')
   '\\broken\\link'
   >>> os.path.realpath('symlink')
   'C:\\broken\\link'

   @eryksun, is this the result you expected, and can the issue be closed?
8. serhiy-storchaka

   added

   pendingThe issue will be closed if no feedback is providedThe issue will be closed if no feedback is provided

   on Aug 8, 2026