Process Group ID's (was: Re: pid rollover?)

[John F. Haugh II]

In article <763 at necisa.necisa.oz> boyd at necisa.necisa.oz (Boyd Roberts) writes:
>In article <12118 at rpp386.Dallas.TX.US> jfh at rpp386.Dallas.TX.US (John F. Haugh II) writes:
>>	for (pp = proc;pp < v.ve_proc;pp++)
>>		if (pp->p_stat && pp->p_pid == mpid)	/* oops, exists */
>>			goto again;
>
>Guess again, bozo.  You've also got to check for p->p_pgrp clashes.
>You can't have mpid == an active process group id.

I may be wrong - I checked using the `compile a program and see how it
behaves' school of UNIX behaviour determination - but you can't have an
active process group if the process group leader is dead.

Or did I miss something?
% crash
> proc 16
SLT ST  PID  PPID  PGRP   UID  EUID PRI CPU    EVENT NAME       FLAGS
 16 s  9378     1     0     0     0  39   0  6000000 hang       incore text

That was a member of a process group which was exited from.  The program
lingered because it was ignoring the SIGHUP it was sent.  As you can see,
the process group is now zero.

Before I spend too many more hours trying to figure out the circumstance
under which the process group would not be reset to zero, does anyone
know of one?
-- 
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