exception backtrace for ruby/tk programs

[Ferenc Engard]

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? 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)

 

[Ara.T.Howard]

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)

====================================
| Ara Howard
| NOAA Forecast Systems Laboratory
| Information and Technology Services
| Data Systems Group
| R/FST 325 Broadway
| Boulder, CO 80305-3328
| Email: (e-mail address removed)
| Phone: 303-497-7238
| Fax: 303-497-7259
| The difference between art and science is that science is what we understand
| well enough to explain to a computer. Art is everything else.
| -- Donald Knuth, "Discover"
| ~ > /bin/sh -c 'for lang in ruby perl; do $lang -e "print \"\x3a\x2d\x29\x0a\""; done'
====================================

 

[Hidetoshi NAGAI]

Hi,

From: Ferenc Engard <[email protected]>
Subject: exception backtrace for ruby/tk programs
Date: Thu, 9 Oct 2003 08:50:56 +0900

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? If
not, then here is the simple patch, maybe it can be put into the
mainstream code.

I think the information is too verbose. So, I truncate the backtrace
based on the difference of the backtrace between pre- and post-calling
callback-body. However, if no exception, it is waste of resources to
get and keep the backtrace. On the CVS, I implement that the particulars
are displayed only if $DEBUG == true.