From: Han Holl <han@...>
Date: 2002-06-19T04:34:31+09:00
Subject: Re: Debug.rb and exceptions

Ned Konz wrote:

>On Tuesday 18 June 2002 11:00 am, Han Holl wrote:
>  
>
>>Ned Konz wrote:
>>    
>>
>>>Easy: catch the Errno::EXDEV and instead do a copy followed by a
>>>delete of the original.
>>>      
>>>
>>That is not what I meant at all. What you propose is exactly what
>>ftools.rb does. My question: is it impossible to use the debugger
>>with software that uses begin - rescue  in Python style ?
>>    
>>
>
>Sorry, I misunderstood.
>
>From my reading of debug.rb, it should be possible. If you look at the 
>trace_func, you'll see that 'raise' conditions are handled by 
>excn_handle(), which does nothing (other than printing a trace to 
>stdout) if you don't have a catchpoint set.
>
>Of course, you have to get rid of the default catchpoint on 
>StandardError if you want to ignore any of these.
>
>So if you start up the debugger with (say)
>
>cat SystemExit
>
>then it won't break for any exception other than one that's derived 
>from SystemExit. You could define your own exception if you wanted to 
>really make sure that you didn't catch anything.
>
>Here's an example program (which I called xx.rb):
>
>
>begin
>  puts "before"
>  raise StandardError
>  puts "after"
>rescue StandardError
>  puts "caught"
>end
>
>
>And here's my debug session:
>
>$ ruby -rdebug xx.rb
>Debug.rb
>Emacs support available.
>
>xx.rb:8:end
>(rdb:1) cat SystemExit
>Set catchpoint SystemExit.
>(rdb:1) c
>before
>xx.rb:4: `StandardError' (StandardError)
>caught
>  
>

Yes, this works. You  get a lot of disconcerting error messages, but
it does indeed work.
I guess I didn't quite get what a catchpoint is.
Documentation on debug.rb is scarce indeed.

Thanks for your help,

Han