Exceptions inside of blocks

[JosephAustin]

In many cases it appears that exceptions getting thrown within a do block will cause the program to hang, instead of reporting the backtrace. It then continuously increases in memory use. The problem can also be triggered by using a rescue and trying to print out the exception's message, which leads me to think its message is either very large or generates recursively somehow.

ex:

      button "Purge", parent:packer do
        blah = not_existing_variable
        Dir.glob(File.join($window.trashFolder, "*.*")).each do |file|
          if(!File.directory? file)
            File.delete file
          end
        end
      end

The above code crashes like you would expect on that second line, but at that point the code totally freezes. If I print out its backtrace I get:

../lib/fidgit/event.rb:128:in `call'

../lib/fidgit/event.rb:128:in `block in publish'

../lib/fidgit/event.rb:127:in `reverse_each'

../lib/fidgit/event.rb:127:in `publish'

../lib/fidgit/states/gui_state.rb:284:in `redirect_released_mouse_button'

etc...

Seems to me that something goes totally batty in the event handling. I'm on x86-64 Linux using Ruby 2.1.2p95

EDIT

The issue appears to be caused by the destruction order of widgets in any sort of list. An empty list finishes faster, but the problem is exponential. Manually catching issues inside of event blocks and clearing the list widgets with @widget.parent.clear and then setting the widget itself to nil immediately works, and the error can then be thrown. This provides a troublesome but functional work-around.

[bil-bas]

Does the exception handling work with 1.9.3 or not? (That is the last version I tested it on). I do some funky stuff to make those blocks work, which may possibly be fubar in newer versions.

[JosephAustin]

Hmm, not sure. I will make an attempt. I'm guessing it will and that'll turn out to be what happened. I'll have to roll back somehow or other.

[bil-bas]

I really don't know myself. It is still reasonably likely to be a fault in fidgit, rather than something that went "wrong" with Ruby since I wrote it.

[JosephAustin]

Building it now. Well, you know how it goes, something could have gone 'right' in Ruby since you wrote it that turned what you did wrong :P These things happen.

[bil-bas]

Aye! That is probably the case 😊

[bil-bas]

As an aside, the Ruby idiom is:

File.delete file unless File.directory? file

[JosephAustin]

Yes, I'm still learning ;) Ive been doing that more often now.

I just fired up 1.9.3's irb and got my app to load up, and it handles the exceptions. so there we go.

[bil-bas]

Well, that is "good" news, though I have no idea why it shouldn't work on 2.1 (I haven't used 2.0+ very much at all).

p.s. Drop IRB and start using Pry instead ;)

[bil-bas]

I'm presuming that https://github.com/Spooner/fidgit/blob/master/lib/fidgit/redirector.rb is what is faulty, which is what is used to create those "clever" blocks (in a really dumb way). Might be obvious what is wrong if I knew anything about the newer Ruby versions.

[JosephAustin]

Okay then, I'll have a look at it and if I fix it I'll send you a patch :) There's a workaround by doing exception handling inside every block manually

[bil-bas]

Another workaround would be to not use the blocks (they just make things easier) 😛

[JosephAustin]

And i was wrong, i corrected myself and it -does- lock up in the older ruby. It says

"NameError:"

and freezes.

[JosephAustin]

And then the memory use goes up, up , up.... ctrl-c gives me the proper dump. So some recursive or infinite loop happens.

[bil-bas]

Hmm - do you have a full chunk of code that fails in this way that you could show me? Not sure I'd have any luck, but I can take a look.

[JosephAustin]

Hrm. It's something I did because i just tried to recreate the issue from scratch and couldn't. I would guess it has to do with all the threading stuff i have going on. This simple snippet:

require 'fidgit'

class TestState < Fidgit::GuiState
def initialize
super

horizontal do
  vertical do |packer|
    button "Test", parent:packer do
      hdkjshfk = djxhf
    end
  end
end

end
end

class Window < Chingu::Window
def initialize
super 800, 600, false
push_game_state TestState
end
end

$Window = Window.new
$Window.show

works fine