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Title: os.lstat/os.stat don't set st_nlink on Windows
Type: behavior Stage: resolved
Components: Extension Modules, Windows Versions: Python 3.2
Status: closed Resolution: fixed
Dependencies: Superseder:
Assigned To: brian.curtin Nosy List: brian.curtin, jaraco, ocean-city
Priority: normal Keywords: needs review, patch

Created on 2010-10-05 14:35 by brian.curtin, last changed 2022-04-11 14:57 by admin. This issue is now closed.

File name Uploaded Description Edit
st_nlink.diff brian.curtin, 2010-10-05 14:35 review
py3k_posixpath_v1.patch ocean-city, 2010-10-20 00:59 replaced review
py3k_posixpath_traverse_via_DeviceIoControl.patch ocean-city, 2010-10-22 11:12 Same patch to r85789 review
Messages (19)
msg118012 - (view) Author: Brian Curtin (brian.curtin) * (Python committer) Date: 2010-10-05 14:35
In msg117834 on #8879 it was noticed that os.lstat and os.stat don't set st_nlink on Windows, which is causing the patch on that issue to fail test_tarfile.

Attached is a stripped down version of the patch Hirokazu Yamamoto proposed on #8879, containing just the os.*stat changes. As stated in that message, the patch is a quick hack to get test_os and test_tarfile working, so it could use review.
msg118029 - (view) Author: Brian Curtin (brian.curtin) * (Python committer) Date: 2010-10-05 19:23
Overall I think this looks like a reasonable restructuring, and it works in a few manual tests of existing hardlinks on my system. Until #8879 goes in, we can't really add tests for this.

Hirokazu, do you want to commit this since you came up with it?
msg118064 - (view) Author: Hirokazu Yamamoto (ocean-city) * (Python committer) Date: 2010-10-06 11:47
There are some questions.

1. About my patch, I noticed it removed following code.
   Isn't this needed? I like clean code, but I don't want to
   break anything.

    /* Get WIN32_FIND_DATA structure for the path to determine if
       it is a symlink */
    if(info.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) {
        find_data_handle = FindFirstFileA(path, &find_data);
        if(find_data_handle != INVALID_HANDLE_VALUE) {
            if(find_data.dwReserved0 == IO_REPARSE_TAG_SYMLINK) {
                /* first clear the S_IFMT bits */
                result->st_mode ^= (result->st_mode & 0170000);
                /* now set the bits that make this a symlink */
                result->st_mode |= 0120000;

    /* Set S_IFEXEC if it is an .exe, .bat, ... */
    dot = strrchr(path, '.');
    if (dot) {
        if (stricmp(dot, ".bat") == 0 || stricmp(dot, ".cmd") == 0 ||
            stricmp(dot, ".exe") == 0 || stricmp(dot, ".com") == 0)
            result->st_mode |= 0111;

2. About current behavior. when os.stat() is used for junction
   (reparse point, but not simlink), returned information is
   about junction on XP or earlier, but about target folder on
   Vista or above. Is this intended bahavior?

Thank you.
msg118066 - (view) Author: Hirokazu Yamamoto (ocean-city) * (Python committer) Date: 2010-10-06 11:53
P.S. Thank you for acceptance. I really wanted to commit
that code!
msg118720 - (view) Author: Brian Curtin (brian.curtin) * (Python committer) Date: 2010-10-14 21:48
Jason, any idea on #2?
msg118724 - (view) Author: Jason R. Coombs (jaraco) * (Python committer) Date: 2010-10-14 22:15
I'm unsure. I think when I addressed the issue, I was only concerned with symlinks. The Vista behavior sounds correct to me, so it may be that XP was left with the legacy behavior as it doesn't have native symlink support. It sounds as if the behavior on XP should be modified to follow the same technique as in Vista. I don't know when I'll have a moment to look at it in depth, but I'll try to in the next week or two.
msg119108 - (view) Author: Hirokazu Yamamoto (ocean-city) * (Python committer) Date: 2010-10-19 02:21
How about this patch?

* st_nlink support for stat()/lstat().
* lstat() for junction read attributes of junction not target.
* stat() for symlink of system locked file (ie: c:/pagefile.sys)
  should read attributes from target locked file not of symlink
  even via FindFirstFile. (I cannot test this, sorry)

I hope other behavior was not changed by this patch.
msg119110 - (view) Author: Hirokazu Yamamoto (ocean-city) * (Python committer) Date: 2010-10-19 02:24
... I noticed I can test this via buildbot...
Probably I'll try this.
msg119111 - (view) Author: Brian Curtin (brian.curtin) * (Python committer) Date: 2010-10-19 02:39
I'll also give it a run on my Windows machines but won't be able to until tomorrow morning (~1300 UTC).
msg119130 - (view) Author: Hirokazu Yamamoto (ocean-city) * (Python committer) Date: 2010-10-19 10:33
I noticed stat() won't set S_IEXEC in stat()
with my patch (py3k_posixpath_v1.patch). :-(
msg119182 - (view) Author: Hirokazu Yamamoto (ocean-city) * (Python committer) Date: 2010-10-20 01:03
I replaced my patch (almost reverted stat() part)
I think st_nlink will be set via stat()/lstat(), at least.
msg119380 - (view) Author: Hirokazu Yamamoto (ocean-city) * (Python committer) Date: 2010-10-22 11:12
I created test branch "branches/py3k-stat-on-windows" and
committed the new patch in r85789. This achieves msg119108.
I tested this on Windows7 buildbot where symlink support
exists, it seems working correct.
msg120521 - (view) Author: Brian Curtin (brian.curtin) * (Python committer) Date: 2010-11-05 18:26
Works for me. I think it should be ok to commit.
msg120675 - (view) Author: Hirokazu Yamamoto (ocean-city) * (Python committer) Date: 2010-11-07 12:38
I found Win32 FileID API. With this library, it seems
we can use GetFileInformationByHandleEx before Vista.
We can get real file name and hard link count from handle.

I don't have a patch, but maybe it is worth to implement it.
msg121667 - (view) Author: Brian Curtin (brian.curtin) * (Python committer) Date: 2010-11-20 15:50
I'm not sure how that would work in terms of redistributing, and how we'd handle it within our own build process. This close to the beta I'm -1 on adding that API.
msg121977 - (view) Author: Hirokazu Yamamoto (ocean-city) * (Python committer) Date: 2010-11-21 20:21
Thank you for reply. Could you commit my last patch
instead of me? I cannot commit files for a while.
msg122275 - (view) Author: Brian Curtin (brian.curtin) * (Python committer) Date: 2010-11-24 13:32
Committed to py3k in r86727.

I think this should be backported to the maintenance branches, but not until after the upcoming point releases. Although those branches won't have the ability to create hard links, they should have the ability to view information about existing links on the system (or if they create them via ctypes/pywin32). Since those branches won't be able to explicitly test this, I think it makes sense to let this bake for a while on py3k.
msg122324 - (view) Author: Hirokazu Yamamoto (ocean-city) * (Python committer) Date: 2010-11-25 02:01
Thank you for commit!
msg137624 - (view) Author: Brian Curtin (brian.curtin) * (Python committer) Date: 2011-06-04 03:00
This code has changed a lot since originally being committed, so I'll handle backporting in #12084 which has the latest changes.
Date User Action Args
2022-04-11 14:57:07adminsetgithub: 54236
2011-06-04 03:00:56brian.curtinsetstatus: open -> closed

messages: + msg137624
2010-11-25 02:01:48ocean-citysetmessages: + msg122324
2010-11-24 20:26:23brian.curtinunlinkissue8879 dependencies
2010-11-24 13:32:28brian.curtinsetassignee: ocean-city -> brian.curtin
resolution: accepted -> fixed
messages: + msg122275
stage: patch review -> resolved
2010-11-21 20:21:07ocean-citysetmessages: + msg121977
2010-11-20 15:50:46brian.curtinsetmessages: + msg121667
2010-11-07 12:38:54ocean-citysetmessages: + msg120675
2010-11-05 18:26:48brian.curtinsetassignee: ocean-city
messages: + msg120521
2010-10-22 11:12:36ocean-citysetfiles: + py3k_posixpath_traverse_via_DeviceIoControl.patch

messages: + msg119380
2010-10-20 01:03:10ocean-citysetmessages: + msg119182
2010-10-20 00:59:47ocean-citysetfiles: - py3k_posixpath_v1.patch
2010-10-20 00:59:31ocean-citysetfiles: + py3k_posixpath_v1.patch
2010-10-19 10:33:11ocean-citysetmessages: + msg119130
2010-10-19 02:39:30brian.curtinsetmessages: + msg119111
2010-10-19 02:24:01ocean-citysetmessages: + msg119110
2010-10-19 02:21:20ocean-citysetfiles: + py3k_posixpath_v1.patch

messages: + msg119108
2010-10-14 22:15:35jaracosetmessages: + msg118724
2010-10-14 21:48:48brian.curtinsetnosy: + jaraco
messages: + msg118720
2010-10-06 11:53:09ocean-citysetmessages: + msg118066
2010-10-06 11:47:50ocean-citysetmessages: + msg118064
2010-10-05 19:23:36brian.curtinsetresolution: accepted
messages: + msg118029
2010-10-05 14:39:44brian.curtinlinkissue8879 dependencies
2010-10-05 14:35:25brian.curtincreate