Feature or enhancement

Speed up os.path.splitroot() by implementing it in C.

Pitch

Per @eryksun:

I think splitroot() warrants a C implementation since it's a required step in our basic path handling on Windows -- join(), split(), relpath(), and commonpath(). Speeding it up gives a little boost across the board. Also, it would be less confusing if nt._path_splitroot() actually implemented ntpath.splitroot().

If implemented, using _Py_splitroot() in _Py_normpath() would help to ensure consistency. Currently, for example, ntpath.normpath('//?/UNC/server/share/../..') is correct on POSIX but wrong on Windows because _Py_normpath() incorrectly handles "//?/UNC/" as the root instead of "//?/UNC/server/share/".

Previous discussion

• https://discuss.python.org/t/add-os-path-splitroot/22243
• Add os.path.splitroot() function #101000
• GH-80486: Fix handling of NTFS alternate data streams in pathlib #102454

Linked PRs

• gh-102511: Add C implementation of os.path.splitroot() #118089
• [3.12] gh-102511: Fix os.path.normpath() for UNC paths on Windows. #119394
• gh-102511: Amend 3.13.0b1.rst #119895
• [3.13] gh-102511: Amend 3.13.0b1.rst (GH-119895) #119980
• gh-102511: Change the os.path.splitroot param name from path back to p #124097
• [3.13] gh-102511: Change the os.path.splitroot param name from path back to p (GH-124097) #124919