bug#15648: 24.2.50; gnutls SSL connection to IMAP server causes emacs to crash completely

[Eli Zaretskii <eliz@gnu.org>]

> From: <emacs@kosowsky.org>
> Date: Mon, 11 Nov 2013 14:12:34 -0500
> Cc: Ted Zlatanov <tzz@lifelogs.com>, emacs@kosowsky.org, 15648@debbugs.gnu.org
> 
> Well, there is also the problem that "/usr" is never present as a root
> path on any (standard) Windows machine, so that the path commented as
> being valid for cygwin actually never works! 

Please don't assume that what happens on your machine happens on
everyone else's.  E.g., my systems do have a /usr directory at least
on some of the drives.  No, I don't run Cygwin.

More generally, "/foo/bar" is a valid file name on Windows, whether
foo equals "usr" or not.  It is simply wrong to assume that if you see
/usr on Windows, it _must_ mean a Cygwin mount.  This kind of
reasoning is simply a non-starter.

> The absence of cygwin-mount magic file handling when a file name is
> passed directly to the gnutls c-code without going through any of the
> standard magic-file-handling file access routines is the crux of the
> problem.

No, the crux of the problem is that you are trying to use a natively
built Emacs with file names that make sense only for Cygwin programs.
If you want Cygwin semantics of file names, use a Cygwin build of
Emacs, and this problem will immediately go away.  Alternatively, use
file names for your certificates that native Windows programs can
find, and the problem will also go away immediately.

> So, again I see only 2 solutions:
> 1. Change (or omit) the "/usr" path and make it relative to cygwin
>    root (though this would not work generally since cygwin root is
>    changeable)
> 
> 2. Implement magic handling so that paths are automagically translated
>    to be correct at the file system level. In this case, by inserting
>    the cygwin root.

  3. Don't mix Cygwin file names with native Windows programs.