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From: arne@yc.estec.nl
Newsgroups: comp.windows.x
Subject: Re: XDMCP/-query option to MIT sample servers
Message-ID: <9006071154.AA18296@yc1.yc.estec.nl>
Date: 7 Jun 90 11:54:19 GMT
References: <9006061659.AA05569@xenon.lcs.mit.edu>
Sender: root@athena.mit.edu (Wizard A. Root)
Organization: The Internet
Lines: 34


> xdm does not support XDMCP when running on SYSV machines.  The lack of reliable
> signal handling in a SYSV environment would make this quite difficult to
> implement.  The problem revolves around listening for UDP packets on a socket
> and also waiting for child process termination.

In the case of a HP-UX machine i believe that there exists a reliable signal
mechanism. Refer to the following extract from sigvector(2):

     SYNOPSIS
          #include <signal.h>

          sigvector(sig, vec, ovec)
          int sig;
          struct sigvec *vec, *ovec;

     DESCRIPTION
          The system defines a set of signals that can be delivered to
          a process.  The set of signals is defined in signal(5),
          along with the meaning and side effects of each signal.
          This manual page, along with those for sigblock(2),
          sigsetmask(2), sigpause(2), and sigspace(2), defines an
          alternate mechanism for handling these signals that assures
          the delivery of signals and integrity of signal handling
          procedures.  The facilities described here should not be
          used in the same program as signal(2).

Would it be possible to modify xdm to use these facilities and get XDMCP support?
How difficult would you think that this would be?

I have had a quick look and it seems like the ``SYSV'' define is used both for 
adapting to the different signals and also many other System V differences.

-- Arne Lundberg