🚀 go-pugleaf

We have recently upgraded to SunOS 4.1.  Now, when running emacs under
X (with HAVE_X_WINDOWS defined) an attempt to start up a shell buffer
with csh as the shell hangs with:

"Process shell stopped (tty input)."

I have tried this with the shell.el that comes with emacs, with a
multi-shell version that I snarfed from the net, with vanilla emacs
version 18.55 (with X support), and with epoch version 3.2beta.  All
fail in the same manner.  Working via a glass tty has not caused the
problem.  Emacs invoked under an xterm without X support works fine as
well.

If the explicit-shell-file-name is set to "/bin/sh" this does not
happen.  Also if /bin/csh is invoked with -c (by 'compile for example)
then it works fine as well.  The stopped shells show up like:

23964 ?  TW    0:00 -bin/csh -i (csh)

in a `ps x`.

One of our local guru's had this to say:

> From: bruner@csrd.uiuc.edu (John Bruner)
> Subject: Re: emacs under X and /bin/csh
> 
> This sounds like a problem with process groups.  I believe that the
> process group code changed in SunOS 4.1 in order to more closely
> conform to the System V Interface Definition.  It sounds like emacs
> may not be establishing the controlling terminal of its subshells,
> perhaps because it doesn't correctly dissociate itself with the
> original controlling terminal (the pty from which the "emacs-X"
> process was started).
> 
> When "csh" is run interactively it tries to put itself into its own
> process group, change the process group of its controlling terminal to
> be its own pgrp, and then it reads from it.  If it fails to change the
> process group the read will generate a SIGTTIN (tty input stop).
> 
> "sh" and "csh -c" do not use job control.
> 

Is this a "known" problem with 18.55?  My apologies in advance if this
has been discussed here before - I haven't been reading this group
recently.  I will resubscribe, so either email or post of a solution
would be greatly appreciated.
--
    Steve Turner (on the Si prairie  - UIUC CSRD)

    ARPANET:  turner@csrd.uiuc.edu
    Phone:    (217) 244-7293 or (217) 367-0882

    I went walking in the wasted city / Started thinking about entropy
    Smelled the wind from the ruined river / Went home to watch TV
                                                 -- Warren Zevon