Re: [ gnuplot-Bugs-3468950 ] Qt, moc and uic not found on Mac OS X

[sfeam (E. Merritt) <eam...@gm...>]

On Monday, 09 January 2012, Jérôme Lodewyck wrote:
> Le Dimanche 8 Janvier 2012 21:55:35 vous avez écrit :
> > I have been running with this one (version 2) under linux.
> > It looks pretty good.  Over the day or so of testing I've accumulated
> > 3 zombie gnuplot_qt processes, however.  So there's a termination
> > condition that's being missed somewhere.
> 
> I tried very hard to crash it but failed to reproduce your observation. Each 
> time I get a gnuplot_qt zombie, there is a gnuplot one, and killing the later 
> kills the former. 

I wasn't really trying to crash anything.  I was just trying to debug
other, unrelated, problems.  Sometimes the program would crash.
Apparently some of those times it would leave behind a zombie.
I didn't notice till later, so I can't tell you exactly what I was 
doing at the time.  

Nevertheless, I think I can now reproduce it consistently.
This is today's CVS with your patch #2 applied.
Here is a recipe:

$ ./gnuplot             # terminal defaults to qt
gnuplot> plot x         # so far, so good

[in another terminal window]
$ ps -efT | grep gnuplot           # both ./gnuplot and gnuplot_qt visible
$ kill -9 <pid of ./gnuplot>
$ ps -efT | grep gnuplot           # gnuplot_qt is visible, ./gnuplot is gone

[close the qt plot window by clicking 'X' in the window title bar]
$ ps -efT | grep gnuplot           # gnuplot_qt is now a zombie

I think the problem is that if the parent process dies hard,
either from an unintentional segfault or from receiving a KILL signal,
then any atexit() processing that would have sent a signal to the 
child doesn't happen.

I thought at first that maybe this only happened if the child
window was closed at the time the parent process was killed, 
but apparently that doesn't matter.

So what I see doesn't seem to match what you see, since you say that if
you kill the parent process then the child process dies also.
That isn't happening here.

> An interesting question would be whether the zombies you 
> observed are still reachable by starting a new gnuplot and entering
> 	set term qt widget "qtgnuplotXXX"
> where XXX is the pid of the zombie gnuplot_qt.

Yes, that works.
So strictly speaking they are not zombies.  But they will sit forever
in that state unless you do something clever.

	cheers,

		Ethan