Re: MPS: Win64 testers?

[Eli Zaretskii <eliz@gnu.org>]

> From: Quang Kien Nguyen <kien.n.quang@gmail.com>
> Date: Thu, 8 Aug 2024 16:44:09 -0700
> Cc: emacs-devel@gnu.org, pipcet@protonmail.com
> 
> > What ProcExp64 shows is a good sign, but I'd prefer to test also some
> > redirection like above, with Emacs and the sub-process both writing to
> > the same stdout/stderr stream, which would allow to verify positively
> > that they write to different places.
> 
> Okay, I have tested with this lisp exp:
>     (print 10 #'external-debugging-output)
> 
> 10 is printed in the stdout/stderr on the console.
> 
> Then try again with
>     (start-process-shell-command "test" nil "emacs -Q --batch --eval
> \"(print 123123 #'external-debugging-output)\"")
> 
> The child emacs process is spinned up but nothing is spewed to the
> current console
> output.  Does that correct and prove that they don't share the handle?

Not clearly enough.  Consoles are tricky on Windows.  It is better to
start Emacs with stderr redirected to a file (I've shown how to do
that in a previous message), and then see that what the child Emacs
writes to external-debugging-output does not appear in that file.

Also, instead of start-process please use call-process.  That's
because start-process redirects the stdout/stderr handles of the child
process to the pipe from which the parent Emacs process reads, and
that makes the experiment more complex and harder to reason about.