From: "Ara.T.Howard" <ahoward@...>
Date: 2003-10-09T12:11:40+09:00
Subject: Re: exception backtrace for ruby/tk programs

On Wed, 8 Oct 2003, Ferenc Engard wrote:

> Hello,
>
> I suffered with really hard debugging sessions when an unexpected
> exception was thrown from a ruby callback in a ruby/tk application, as
> the tk error dialog box showed only the error message itself and no
> backtrace. I have had to modify TkCore.callback() to reveal the
> backtrace.
>
> Don't you miss this information?

> Can this be done in another way?

how about something simple like this?

~/eg/ruby > cat exception.rb
class Exception
  alias __to_s to_s
  def to_s; __to_s << "\n" << backtrace.map{|t| "\t#{t}\n"}.join; end
end

def method
  raise 'foo'
end

method

~/eg/ruby > ruby exception.rb
exception.rb:8:in `method': foo (RuntimeError)
        exception.rb:8:in `method'
        exception.rb:11

        from exception.rb:11

of course perhpas one should use inspect, but you get the idea...

-a


> If not, then here is the simple patch, maybe it can be put into the
> mainstream code.
>
> ------------------------------------------------------------------
> root@domesticus:/usr/lib/ruby/1.8# diff -u tk.rb.old tk.rb
> --- tk.rb.old   2003-10-09 01:18:38.000000000 +0200
> +++ tk.rb       2003-10-09 01:40:47.000000000 +0200
> @@ -772,7 +772,13 @@
>
> #_get_eval_string(TkUtil.eval_cmd(TkCore::INTERP.tk_cmd_tbl[arg.shift],
>      #                               *arg))
>      cb_obj = TkCore::INTERP.tk_cmd_tbl[arg.shift]
> -    cb_obj.call(*arg)
> +    begin
> +      cb_obj.call(*arg)
> +    rescue
> +      # Append the backtrace to the message, so it can be displayed in
> the
> +      # Tk error dialog window.
> +      raise $!, "#{$!} - backtrace: \n#{$!.backtrace.join("\n")}"
> +    end
>    end
>
>    def load_cmd_on_ip(tk_cmd)
> ------------------------------------------------------------------
>
> Bye:
> Ferenc
>

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  | Ara Howard
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