bug#21831: 24.5 on Windows; start-process modifies its PROGRAM argument

bug#21831: 24.5 on Windows; start-process modifies its PROGRAM argument

[Cornelius Mika]

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start-process normalizes the given PROGRAM path by destructively modifying
its contents.
This is problematic if the path variable is reused later on.

Minimal repro:
(let ((path "c:/Windows/System32/clip.exe"))
  (start-process "" nil path)
  path) ; => "c:\\Windows\\System32\\clip.exe"

In GNU Emacs 24.5.1 (i686-pc-mingw32)
 of 2015-04-11 on LEG570
Windowing system distributor `Microsoft Corp.', version 6.3.9600
Configured using:
 `configure --prefix=/c/usr --host=i686-pc-mingw32'

Important settings:
  value of $LANG: DEU
  locale-coding-system: cp1252

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml
easymenu mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
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uniquify ediff-hook vc-hooks lisp-float-type mwheel dos-w32 ls-lisp
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loaddefs button faces cus-face macroexp files text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote make-network-process w32notify w32
multi-tty emacs)

Memory information:
((conses 8 73857 5808)
 (symbols 32 17432 0)
 (miscs 32 33 131)
 (strings 16 10612 4319)
 (string-bytes 1 268415)
 (vectors 8 9520)
 (vector-slots 4 383153 5554)
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bug#21831: 24.5 on Windows; start-process modifies its PROGRAM argument

[Eli Zaretskii]

> From: Cornelius Mika <cornelius.mika@gmail.com>
> Date: Wed, 4 Nov 2015 21:31:55 +0100
> 
> start-process normalizes the given PROGRAM path by destructively modifying its
> contents.
> This is problematic if the path variable is reused later on.
> 
> Minimal repro:
> (let ((path "c:/Windows/System32/clip.exe"))
> (start-process "" nil path)
> path) ; => "c:\\Windows\\System32\\clip.exe"
> 
> In GNU Emacs 24.5.1 (i686-pc-mingw32)
> of 2015-04-11 on LEG570
> Windowing system distributor `Microsoft Corp.', version 6.3.9600
> Configured using:
> `configure --prefix=/c/usr --host=i686-pc-mingw32'

Thanks.

I can reproduce this in Emacs 24.5, but not in the current development
sources.  So this problem was already fixed as part of the development
since then, and I see the code which was added to avoid this.

So I'm marking this bug done.

bug#21831: 24.5 on Windows; start-process modifies its PROGRAM argument

[Nicolas Richard]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Cornelius Mika <cornelius.mika@gmail.com>
>> Minimal repro:
>> (let ((path "c:/Windows/System32/clip.exe"))
>> (start-process "" nil path)
>> path) ; => "c:\\Windows\\System32\\clip.exe"

> I can reproduce this in Emacs 24.5, but not in the current development
> sources.  So this problem was already fixed as part of the development
> since then, and I see the code which was added to avoid this.

Thanks for checking.
Did you see a test associated to this fix ?

perhaps something like :

(ert-deftest start-process-should-not-modify-arguments ()
  "`start-process' must not modify its arguments in-place."
  ;; See bug#21831.
  (let* ((path (pcase system-type
                 ('windows-nt  "c:/Windows/System32/clip.exe")
                 ('ms-dos "c:/command.com")
                 (_ "/bin//sh")))
         (samepath (copy-sequence path)))
    (start-process "" nil path)
    (should (equal path samepath))))

to be included in test/automated/process-tests.el

I'm not sure what a good value of `path' might be.

-- 
Nico.

bug#21831: 24.5 on Windows; start-process modifies its PROGRAM argument

[Eli Zaretskii]

> From: Nicolas Richard <youngfrog@members.fsf.org>
> Cc: eliz@gnu.org,  cornelius.mika@gmail.com
> Date: Thu, 05 Nov 2015 09:42:54 +0100
> 
> Did you see a test associated to this fix ?
> 
> perhaps something like :

Thanks, I pushed a variant of your suggested test.