bug#22795: 25.0.91; Can't write read only file on w32

["Ota, Takaaki" <Takaaki.Ota@am.sony.com>]

Mon, 29 Feb 2016 22:06:39 +0200: Eli Zaretskii <eliz@gnu.org> wrote:

> > Date: Mon, 29 Feb 2016 11:28:15 -0800
> > CC: <22795@debbugs.gnu.org>
> > From: "Ota, Takaaki" <Takaaki.Ota@am.sony.com>
> > 
> > emacs-24.5 never called sys_rename().
> 
> ??? It does here.  The call is in backup-buffer: it calls rename-file.
> 
> Are you trying this in "emacs -Q"?  If not, perhaps you have some
> customizations, like backup-by-copying or
> backup-by-copying-when-mismatch etc.?
> 
> > emacs-25.0.91 calls sys_rename() but strangely old name and the new
> > name are the same.  See below.
> > 
> > -Tak
> > 
> > Breakpoint 1, sys_rename (old=0x880c9b8 "c:/d/ota/memo", 
> >     new=0x880c9b8 "c:/d/ota/memo") at w32.c:4543
> > 4543    {
> > (gdb) n
> > 4544      return sys_rename_replace (old, new, TRUE);
> > (gdb) s
> > sys_rename_replace (oldname=oldname@entry=0x880c9b8 "c:/d/ota/memo", 
> >     newname=newname@entry=0x880c9b8 "c:/d/ota/memo", force=force@entry=1)
> >     at w32.c:4404
> 
> Again, is this in "emacs -Q"?  The backup file name is generated by
> the function find-backup-file-name, you will find it in files.el.  It
> is called by backup-buffer.  Please see what file names it produces in
> this case.
> 

I just tried again with "run -Q" from gdb and the result is the same.
24.5 never called sys_rename() and 25.0.91 called sys_rename() with
two same names.

-Tak