Re: UNIX signal handling

[Owen Taylor <otaylor redhat com>]

Andy Kahn <kahn@zk3.dec.com> writes:

> On Fri, Jul 10, 1998 at 07:20:56PM +0200, Daniel Solaz wrote:
> > The HTML docs simply state that GTK will install several signal
> > handlers. I'm talking about unix signals now.
> > What purpose do they serve? Do they clean up things on exit? Is there
> > any reason why resetting them would be a bad idea?
> > -Daniel
> > 
> 
> i dug around in this area as well and found that in gdk_init(), signal
> handlers are installed for SIGHUP, SIGINT, SIGQUIT, SIGBUS, SIGSEGV,
> SIGPIPE, and SIGTERM (effectively, all the "fatal" signals).  they are
> all caught with one signal handler, gdk_signal().  but if you take a
> look at gdk_signal(), it really does nothing useful!

Yes and no. There are actually two important things that gdk_signal() 
does.

* The reason that it was originally added, I think, was to
  destroy shared memory segments that were created for X images.
  This isn't as important now, since GTK+ when possible uses
  IPC_RMID to do a deferred destroy when the last program 
  detaches, but there are, I think, still programs, where 
  without gdk_signal() control-C'ing out of a GTK program
  will leak shared memory segments.

* Also, gdk_key_repeat_disable() disables key-repeat globally,
  so the exit function tries to restore that. That the
  key-repeat is global is a defect of X, but I think it
  may be possible to work around that by looking for
  key-release / press pairs with identical timestamps and
  ignoring them.

So the purpose wasn't just to hide the core and print out
a pretty error message, though on most platforms in most
cases, that's what it works out to.

Regards,
                                        Owen