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The test failures in free-threading look unrelated to my eye but maybe I'm missing some context. E.g. I'm not sure how this change could cause cause a concurrency issue:

     self._send_bytes(m[offset:offset + size])
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\a\cpython\cpython\Lib\multiprocessing\connection.py", line 293, in _send_bytes
    raise ValueError("concurrent send_bytes() calls "
                     "are not supported")
ValueError: concurrent send_bytes() calls are not supported

@eryksun, would you mind having a look at this one? Thanks!

The test failures in free-threading look unrelated to my eye but maybe I'm missing some context.

I triggered a re-run, let's see if it reproduces.

@nineteendo could also use your input, if you have time to look at this. Cheers!

Well, I can't test this on my machine because python crashes with these warnings after the build (his is not a new issue):

C:\Users\wanne\cpython\PCbuild\python.vcxproj(134,5): warning MSB3073: The command "setlocal
C:\Users\wanne\cpython\PCbuild\python.vcxproj(134,5): warning MSB3073: set PYTHONPATH=C:\Users\wanne\cpython\Lib
C:\Users\wanne\cpython\PCbuild\python.vcxproj(134,5): warning MSB3073: "C:\Users\wanne\cpython\PCbuild\amd64\python.exe" "C:\Users\wanne\cpython\PC\validate_ucrtbase.py" ucrtbase" exited with code -1073741819 
.

You still need to add tests though.

You still need to add tests though.

I'm not sure how to add tests. realpath requires that the path really exist on a network path. We can't fake it because the point of realpath is to resolve to the real path.

Is there no other way to get GetFinalPathNameByHandleW to return UNC paths?

Well, I can't test this on my machine because python crashes with these warnings after the build (his is not a new issue):

Is it fixed in main? If so we can sync the PR, so that the fix is included.

No, this issue is still open: #123414

UPDATE: fixed by creating a clean clone, but I can't install Python libraries it seems

Is there no other way to get GetFinalPathNameByHandleW to return UNC paths?

Hmm... maybe I could try using a \\localhost\c$ path. I'll experiment.

That seems to work but the next problem I'm encountering is that there doesn't appear to be any existing unit tests for the C implementation of realpath (or any of the other functions in getpath.c) and I don't know how to add them. The test_getpath.py shims them for its testing.

I could maybe test using sysconfig::get_paths() but that means we'd need to run the test python using a \\?\UNC\localhost\ style path and not all drives support that (iirc dev drives don't). So it might be a bit flaky.

This can be tested locally without needing to import anything by starting python with a \\?\UNC path. E.g. if the build directory is in C:\Users\Chris\Python\PCBuild\amd64\python.exe then run:

\\?\UNC\localhost\c$\Users\Chris\Python\PCBuild\amd64\python.exe -c "import sysconfig; print(sysconfig.get_paths()['include'])"

This should print the simplified path: \\localhost\c$\Users\Chris\Python\Include. Whereas before this change it will have the long \\?\UNC path.

However, this relies on the drive supporting \\locahost.