Strange behaviour on Windows 10

[Pascal Quesseveur <pquessev@gmail.com>]

Hello,

I am encountering a strange problem with emacs on Windows 10 (perhaps
it is not related to emacs but I have not found nothing about it). I
have written a cmd script on Windows 7 which uses plink to launch a
remote command. The script works fine and I use it in emacs through
(call-process) without problems.

As Windows 10 comes with OpenSSH I decided to update my script and use
ssh instead of plink. The script works fine, but it doesn't work
anymore through (call-process). Calls to ssh cause an error:

Le chemin d'accès spécifié est introuvable.

which means the specified filepath cannot be found. ssh.exe is in
C:/Windows/System32/OpenSSH and that directory is in PATH. It seems
that when the script is activated by (call-process) it is unable to
access the C:/Windows/System32/OpenSSH directory. I made the following
test.

#+BEGIN_EXAMPLE
>type xtest.cmd
@echo off
if exist "C:\Windows\System32" (echo OK) else (echo NOK)
if exist "C:\Windows\System32\OpenSSH" (echo OK) else (echo NOK)

>xtest
OK
OK
#+END_EXAMPLE

and in emacs -Q (version 26.1):

#+BEGIN_EXAMPLE
(defun xtest()
  (interactive)
  (call-process "xtest" nil t nil))
M-x xtest
OK
NOK
#+END_EXAMPLE

The problem arises for OpenSHH directory but this is not the only
case. Directory C:\Windows\System32\Microsoft doesn't work either.
The problem is not limited to emacs as I also noted a stange behavior
from which command from EzWin:

#+BEGIN_EXAMPLE
> which --version
GNU which v2.20, Copyright (C) 1999 - 2008 Carlo Wood.
(Modified for MS-Windows/MinGW by Eli Zaretskii.)
> which ssh.exe
which: no ssh.exe in (.;C:\Program...;C:\WINDOWS\System32\OpenSSH\;...)
#+END_EXAMPLE


-- 
Pascal Quesseveur
pquessev@gmail.com