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Date: Fri, 27 Mar 2020 14:01:33 +0100
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: WSL symbolic links
Message-ID: <20200327130133.GM3261@calimero.vinschen.de>
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On Mar 27 13:24, Thomas Wolff wrote:
> Am 27.03.2020 um 12:21 schrieb Corinna Vinschen:
> > On Mar 27 00:52, Thomas Wolff wrote:
> > > [...]
> > > > rd-reparse '\??\C:\tmp\link' ; echo
> > > ReparseTag:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0 0xa000001d
> > > ReparseDataLength:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0 8
> > > Reserved:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0
> > > 02 00 00 00 66 69 6c 65
> > > > rd-reparse '\??\C:\tmp\link-abs' ; echo
> > > ReparseTag:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0 0xa000001d
> > > ReparseDataLength:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0 19
> > > Reserved:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0
> > > 02 00 00 00 2f 6d 6e 74 2f 63 2f 74 6d 70 2f 66
> > > 69 6c 65
> > > > rd-reparse '\??\C:\tmp\link-foo' ; echo
> > > ReparseTag:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0 0xa000001d
> > > ReparseDataLength:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0 9
> > > Reserved:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0
> > > 02 00 00 00 66 c3 b6 c3 b6
> > > > rd-reparse '\??\C:\tmp\link-foo-abs' ; echo
> > > ReparseTag:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0 0xa000001d
> > > ReparseDataLength:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0 20
> > > Reserved:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0
> > > 02 00 00 00 2f 6d 6e 74 2f 63 2f 74 6d 70 2f 66
> > > c3 b6 c3 b6
> > [...]
> > I debugged this now and I found that practically all problems, including
> > the inability to delete the symlink, are a result of not being able to
> > open the reparse point correctly as reparse point within Cygwin.  So as
> > not to destroy something important, Cygwin only opens reparse points as
> > reparse points if it recognizes the reparse point type.
> >=20
> > Consequentially, all immediate problems go away, as soon as Cygwin
> > recognizes and handles the symlink :)
> >=20
> > So I created a patch and pushed it.  The latest developer snapshot from
> > https://cygwin.com/snapshots/ contains this patch.
> Works, great, thank you!

Thanks for testing!

> > Funny sidenote: Assuming you create symlinks pointing to files with
> > non-UTF-8 chars, e. g., umlauts in ISO-8859-1, then the symlink converts
> > *all* these chars to the Unicode REPLACEMENT CHARACTER 0xfffd.  I assume
> > this will also happen if you try to create the file with these chars in
> > the first place, so it's not much of a problem.
> As Windows filenames are character strings as opposed to Linux filenames
> which are byte strings, some strange behaviour is unavoidable. I see:
> $ wsl ls -l link_LW
> lrwxrwxrwx=C2=A0=C2=A0=C2=A0 1 towo=C2=A0=C2=A0=C2=A0=C2=A0 towo=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 19 Mar 27 12:11 l=
ink_LW ->
> file_L_=EF=83=A4=EF=83=B6=EF=83=BC=EF=83=9F
> $ ls -l link_LW
> lrwxrwxrwx 1 towo Kein 11 27. Mrz 13:11 link_LW -> file_L_=EF=BF=BD=EF=BF=
=BD=EF=BF=BD=EF=BF=BD
> which looks OK for me.

Not sure I expressed myself correctly there.  What I was trying to say
is, the symlink created by WSL already contains the 0xfffd replacement
char, in UTF-8 \xef \xbf \xbd.  So the info is already lost inside the
symlink.


Corinna

--=20
Corinna Vinschen
Cygwin Maintainer

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