gh-152433: Windows: modernize and refactor fileutils to allow build for Windows UWP

[thexai]

Windows: modernize and refactor fileutils to allow build for Windows UWP

This is probably the last relevant commit missing to allow compile all Python core for UWP.

GetFileInformationByHandle is not supported in UWP, then is replaced with more modern GetFileInformationByHandleEx calls.

Also code refactored to avoid some duplicated code.

Note that Xbox (all models) runs only on Windows 11 based OS. Then is guaranteed that "fast stat" code (based on GetFileInformationByName) is supported:

cpython/Modules/posixmodule.c

Line 2299 in 050a84b

if (_Py_GetFileInformationByName(path, FileStatBasicByNameInfo,

"slow stat" code path is not much relevant for UWP but also works if replaced CreateFileW with CreateFile2 (in other PR).

• Issue: Windows: improve compatibility to build for UWP / Xbox #152433

[thexai]

Updated with more simplified and less invasive changes.

[chris-eibl]

This breaks CI, e.g.

test_1686475 (test.test_os.test_os.StatAttributeTests.test_1686475) ... Windows fatal exception: access violation

Can you reproduce this on a local Windows installation and fix?

Regarding tests I have another question: are you able to run the tests on XBOX in general? I'd be curious in how many of them fail ...

[thexai]

This breaks CI, e.g.

test_1686475 (test.test_os.test_os.StatAttributeTests.test_1686475) ... Windows fatal exception: access violation

Can you reproduce this on a local Windows installation and fix?

Reproduced and now should be fixed in latest PR update. 🙂

It's important to note that some tests fail because they expect specific responses to unusual situations that may not have a single logical outcome. For example:

If a file is inaccessible (due to permissions), the parent directory is read, and if it's no longer available, the original error is not restored (instead of return access violation error, return file no exist error).

    # bpo-46785: the implementation of os.stat() falls back to reading
    # the parent directory if CreateFileW() fails with a permission
    # error. If reading the parent directory fails because the file or
    # directory are subsequently unlinked, or because the volume or
    # share are no longer available, then the original permission error
    # should not be restored.

Also on UWP, due security restrictions (every App runs isolated) is not possible to access to some information in the file system like st_dev (VolumeSerialNumber) or st_ino.

[chris-eibl]

LGTM, but I'd appreciate a second pair of eyes @python/windows-team.

[zooba]

Only left two comments, but the guts of it is, I think we can switch to FileStandardInfo for everyone, and that should simplify this change down to basically not needing the separate UWP path at all.

[thexai]

Updated PR with one simplification:

UWP not support GetFileInformationByHandle but the struct used to pass info BY_HANDLE_FILE_INFORMATION is still defined and can be used in some places e.g here:

cpython/Modules/posixmodule.c

Lines 2027 to 2043 in 202c4c8

	find_data_to_file_info(WIN32_FIND_DATAW *pFileData,
	BY_HANDLE_FILE_INFORMATION *info,
	ULONG *reparse_tag)
	{
	memset(info, 0, sizeof(*info));
	info->dwFileAttributes = pFileData->dwFileAttributes;
	info->ftCreationTime = pFileData->ftCreationTime;
	info->ftLastAccessTime = pFileData->ftLastAccessTime;
	info->ftLastWriteTime = pFileData->ftLastWriteTime;
	info->nFileSizeHigh = pFileData->nFileSizeHigh;
	info->nFileSizeLow = pFileData->nFileSizeLow;
	/* info->nNumberOfLinks = 1; */
	if (pFileData->dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT)
	*reparse_tag = pFileData->dwReserved0;
	else
	*reparse_tag = 0;
	}

This allows remove part of UWP only code and some ifdef.

[thexai]

Simplification 2:

Merges _Py_attribute_data_to_stat and _Py_attribute_data_to_stat_UWP in one.

[thexai]

I think I've finished this!

Minimal changes and the same common code for UWP and Desktop.

Tests should pass...

[zooba]

Apologies for lots of suggestions, but I'm excited about this cleanup! We're so close to really streamlining this code, so it'd be great to go the whole way.

My main target is to fully remove the BY_HANDLE_FILE_INFORMATION usage entirely, and also to minimise the logic in the to_stat function (more overwriting, less checking). The comments I've left should lead you there, but feel free to ignore them if you see another way.

[thexai]

Full remove BY_HANDLE_FILE_INFORMATION usage and cleanup done!

[zooba]

Looks great overall, glad we kept going, this is really neat!

Still have a question about guessing at ino values when we don't know them.

[zooba]

Do you have a specific scenario for needing these to be non-zero but inaccurate?

They are documented as allowed to be zero if not obtainable (even though it turns out that samestat doesn't check that), but I think the risk of declaring two files to be the same when they aren't is worse than declaring the ino as unknown when it's unknown. So I'd prefer to leave them both at zero if there's no ID info.

[thexai]

I don't have a concrete answer right now, I only added it because it was in the old UWP patches... I can remove it for now and add it back later if a specific reason comes up.