bug#13921: 24.2; Misbehavior of expand-file-name on Cygwin with Emacs 24.2

[Eli Zaretskii]

> Date: Wed, 13 Mar 2013 05:52:58 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 13921@debbugs.gnu.org
> 
> >    source-directory is a variable defined in `lread.c'.
> >    Its value is "d:/devel/emacs/release/emacs24/emacs-24.2/"
> > 
> >    Documentation:
> >    Directory in which Emacs sources were found when Emacs was built.
> >    You cannot count on them to still be there!
> > 
> > I did not find this /devel/emacs/release/emacs24/emacs-24.2/ on my system,
> > nor is it the kind of path I would create.
> 
> source-directory is where Emacs was built.  And since you didn't build
> it yourself, this reflects the directory where whoever built it did
> that.
> 
> And since Cygwin passes to Emacs a file name without a drive letter,
> the logic in autoload.el causes the D: drive letter be added to
> /home/epich/sw/cedet/lisp/cedet, because it doesn't expect a
> semi-absolute file name like that, it expects either a relative file
> name or a fully-qualified absolute one.
> 
> So this is a direct result of launching a native w32 Emacs from a
> Cygwin Bash.

To make this more clear: this fragment:

  (defun autoload-generated-file ()
    (expand-file-name generated-autoload-file
                      ;; File-local settings of generated-autoload-file should
                      ;; be interpreted relative to the file's location,
                      ;; of course.
                      (if (not (local-variable-p 'generated-autoload-file))
                          (expand-file-name "lisp" source-directory))))

clearly assumes that either generated-autoload-file is a file name
relative to the Emacs's lisp directory, or it is an absolute file
name.  But in your case, it is an absolute file name without a drive
letter, so expand-file-name takes the drive letter from
source-directory.

A Cygwin specific workaround would be to use

  `cygpath -m /home/epich/sw/cedet/lisp/cedet/loaddefs.el`

which will supply the missing drive letter.  (Yes, that means you need
to hack the CEDET build scripts.)