[Octave-bug-tracker] [bug #38305] file dialog causes crash

[Dan Sebald]

Follow-up Comment #37, bug #38305 (project octave):

OK.  Great that you found the problem!

On the other hand, it could be a bad problem requiring some help and
discussion from the maintainers list.

The SIGCHLD is a signal notification to the parent process whenever one of its
child processes terminates:

http://www.gnu.org/software/libc/manual/html_node/Job-Control-Signals.html#Job-Control-Signals

You commented out Octave's signal handler for this, so the application is
likely falling back on Qt's signal handler.  I believe that the Samba server
via Qt is using a child process that originates from the Qt GUI thread.  That
child process(es) is probably an extremely fast LAN access on the order of a
fraction of a second and may not show up in the system monitor because it
doesn't last very long.

I bet the problem is that Octave core's SIGCHLD handler doesn't have the
GUI-thread-created child processes in its list.  Therefore, it cannot
appropriately respond to the signals associated with those children.  This is
tricky.  Either Octave will have to not set the SIGCHLD signal handler when
run under the GUI (not so bad) or the GUI thread will have to figure out how
to put child processes in Octave core's child list (nasty).  It depends on
whether there are some child processes for which Octave core needs to respond
to in a special way.

I'll write to the maintainers list sometime later today.

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