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Re: Today's long path name patch


On Mar  8 10:49, Corinna Vinschen wrote:
> Hi Brian,
> 
> thanks for testing!
> 
> On Mar  7 17:02, Brian Dessent wrote:
> > Corinna Vinschen wrote:
> > 
> > > as I threatened the community with today, I've now checked in my patch
> > > which finally enables long path names in Cygwin.  I tested it on XP,
> > > 2008, and 2008 x64.  What this patch does:
> > 
> > Hmm.  I was playing with this code using the attached testcase.  It
> > simply tries to open(O_RDWR | O_CREAT | O_TRUNC) a filename that
> > contains 256 chars, nothing else.  The call to open fails with errno =
> > ENOENT.  The strace from fhandler_base::open and on looks like this:
> > [...]
> >    25   41152 [main] tc 3304 fhandler_base::open: C0000033 =
> > NtCreateFile (0x0, C0100000,
> > \??\C:\cygwin\home\brian\testcases\long-file-name-create\256charfilename[+241
> > underscores], io, NULL, 81, 7, 5, 4420, NULL, 0)
> > [...]
> > So NtCreateFile is returning STATUS_OBJECT_NAME_INVALID.  Did I
> > misunderstand what's supported, is there a limitation on each
> > path-component or just the total length of the absolute path?  I checked
> > the attr.ObjectName and it appears to be correctly set.
> 
> Every path component is restricted to the length defined by NAME_MAX,
> which is 255 bytes.  This is not different from other systems and defined 
> in limits.h as per POSIX.

Huh!  You uncovered a bug in symlink_info::check.  I ran your testcase
and it tries to open the file with a .lnk attached.

symlink_info::check first tries to get info for the plain filename.
This fails with STATUS_OBJECT_NAME_NOT_FOUND, so it tries to get
info for the same filename with .lnk attached.  However, now the
filename is longer than allowed for a path component and
NtQueryAttributesFile returns with STATUS_OBJECT_NAME_INVALID, which
is handled differently than STATUS_OBJECT_NAME_NOT_FOUND.

I'll look into fixing that.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat


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