Editing with vim clears Windows 10 file system archive bit.
Corinna Vinschen
corinna-cygwin@cygwin.com
Tue Nov 16 14:06:27 GMT 2021
On Nov 15 14:18, Gary Johnson wrote:
> On 2021-11-15, Corinna Vinschen via Cygwin wrote:
> > Changing that is actually pretty simple, just set FILE_ATTRIBUTE_ARCHIVE
> > as soon as the underlying NtCreateFile is called for an open(O_CREAT).
> >
> > Fixed in current git.
>
> I had thought that this might be a bug in Vim, so did a git bisect
> to find the offending commit. For the record, it was this one:
> [...]
> The only change I see to an open() call was removing O_TRUNC on
> systems with ftruncate() and adding a later call to ftruncate() on
> systems that have it. There were also some changes to the setting
> of permissions (fchown(), fchmod() and chmod()). These changes were
> all in the buf_write() function in fileio.c.
>
> That open() call had the O_CREAT flag before and after the change.
You are sooo right.
My bugfix appears to work, but it's fixing a non-existent bug.
NtCreateFile actually sets the ARCHIVE bit all the time when creating a
new file, even if it's not explicitely given as parameter. That makes a
lot of sense, of course, given how the archiving mechanism works on
Windows.
The *real* problem is in fact that Cygwin caches the wrong file
attribute bits when creating a new file, and that's where fchmod fails:
It writes back the wrongly cached bits. This doesn't happen with
chmod, because it re-opens the existing file and fetches the correct
attributes bit at the time.
I guess I'll revert my patch and create a new one which is more to the
point.
Thanks,
Corinna
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