Forum: wxRuby GenericDirCtrl Bus Error crash on OSX

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Mathias Bruce (Guest)
on 2008-11-11 02:01
(Received via mailing list)
Hi all and thanks to everyone working on this project =o)
I have a problem, and I suspect it has its origins in WxRuby...
In my program I use a GenericDirCtrl and handle its corresponding
TreeCtrl item selection event with evt_tree_sel_changed.
In the method handling this event, I try to get at the data of the
selected item, but I run into this:

./my_xrcise_frames.rb:43: [BUG] Bus Error
ruby 1.8.6 (2008-03-03) [universal-darwin9.0]

Abort trap

The code for the event handling method is as follows, where
gdc_browse_tree is the GenericDirCtrl instance:

def on_browse_tree_sel_changed(tree_event)
  item_id = tree_event.get_item
  raise 'item_id was zero' if item_id == 0
  tc = gdc_browse_tree.get_tree_ctrl
  item_data = tc.get_item_data(item_id)
  raise 'item_data was nil' if item_data == nil
end

The line number referenced in the crash bus error (43) is the
"item_data == nil" comparison. The exception doesn't get raised - the
application just crashes. I tried to reproduce it by catching the same
event by modifying the treectrl.rb sample, so I could send you code
you were already very familiar with, but the error didn't appear then.
It seems to require a GenericDirCtrl.

I'm running:
OSX 10.5
ruby 1.8.6 (2008-03-03 patchlevel 114) [universal-darwin9.0]
wx_sugar (0.1.20)
wxruby (1.9.9)

Any help is greatly appreciated! If I have omitted any important
information from this mail, tell me and I will do my best to provide
it. I have used wxruby with great results on linux, and I hope to be
doing the same on OSX in the future.

Best regards,
Mathias
Alex F. (Guest)
on 2008-11-11 02:38
(Received via mailing list)
Mathias Bruce wrote:
> The code for the event handling method is as follows, where
> gdc_browse_tree is the GenericDirCtrl instance:
>
> def on_browse_tree_sel_changed(tree_event)
>   item_id = tree_event.get_item
>   raise 'item_id was zero' if item_id == 0
>   tc = gdc_browse_tree.get_tree_ctrl
>   item_data = tc.get_item_data(item_id)
>   raise 'item_data was nil' if item_data == nil
> end
>

Thanks for reporting this. I think it's a bug. In a normal Wx::TreeCtrl
get_item_data works fine, but the item data held by a TreeCtrl
associated with a GenericDirCtrl isn't a valid ruby object. We can fix
this, and it would be helpful to understand what you were trying to do
here.

Could you say what you expected to get from calling get_item_data here
please? The GenericDirCtrl  already has methods (eg get_path,
get_file_path) that will return the value of the currently selected
directory.

BTW, it's very much appreciated if you can demonstrate a problem in a
minimal, self-contained, runnable sample, rather than just a isolated
snippet. That saves those looking into it having to guess how to
reproduce the context of the problem.

thanks
alex
Mathias Bruce (Guest)
on 2008-11-11 03:07
(Received via mailing list)
On Tue, Nov 11, 2008 at 1:36 AM, Alex F. <removed_email_address@domain.invalid> 
wrote:
>> Abort trap
>> end
>
> http://rubyforge.org/mailman/listinfo/wxruby-users
>

Thanks for the quick reply! I apparently misread the docs gravely, and
got the impression that I had to pick the selected path from the item
itself. GenericDirCtrl.get_path does exactly what I needed... Sorry
for wasting your time =o)

I read on the website about you preferring self-contained error
reproduction code, and I completely understand that. The only reason I
didn't do that was because I'm using XRC and xrcise, so (I think) it
would have been 2-3 separate files, in which case it would be easier
to file a bug in the tracker and put them there. I just thought I'd
find out if the problem was wxruby-related or not, first.

If you still want a little package of code reproducing the error, then
I'll absolutely cook it up, but you don't need to extend the bindings
for my sake anymore, since as you correctly suspected I didn't really
need the item data - and maybe no one else will either... =o)

Thanks again,
Mathias
Alex F. (Guest)
on 2008-11-11 04:44
(Received via mailing list)
Mathias Bruce wrote:
> for wasting your time =o)
>

NP, you haven't wasted my time at all. It helps the dev team understand
where the docs could be clearer. As I said, thanks for reporting the
issue; we can look into making wxRuby give more helpful error messages
than crashing with a "bus error".

> I read on the website about you preferring self-contained error
> reproduction code, and I completely understand that. The only reason I
> didn't do that was because I'm using XRC and xrcise, so (I think) it
> would have been 2-3 separate files, in which case it would be easier
> to file a bug in the tracker and put them there. I just thought I'd
> find out if the problem was wxruby-related or not, first.
>

Simply from experience, taking a problem down to a minimal example is
often a good way to figure out where the error is coming from.

cheers
alex
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