From: Laurent Julliard <Laurent.Julliard@...>
Date: 2002-02-01T19:02:18+09:00
Subject: Frame glitches in Ruby debugger?

There is something I do not understand in the way the ruby debugger 
navigate through the frames (stack level) and display the frame counter. 
Here is my problem:

Take this simple factorial computation program:

def fact(n)
     if n <= 0
       1
     else
       n * fact(n-1)
     end
   end

p fact(5)

Now run the debugger, step (s) 6 times and ask how the frame looks like 
(w or f):

(rdb:1) w
--> #1  /tmp/fact.rb:2:in `fact'
     #2  /tmp/fact.rb:5:in `fact'
     #3  /tmp/fact.rb:5:in `fact'
     #4  /tmp/fact.rb:9

So far, so good. Now ask the debugger to change context and point to the 
frame two levels up

(rdb:1) up 2
#2 /tmp/fact.rb:5
(rdb:1) w
     #1  /tmp/fact.rb:2:in `fact'
     #2  /tmp/fact.rb:5:in `fact'
--> #3  /tmp/fact.rb:5:in `fact'
     #4  /tmp/fact.rb:9


The where command rightly report that we are now in the context of frame 
#3 (#1 + 2 up = #3) but why does the output of the "up 2" command just 
above said "#2 /tmp/fact.rb:5" ?? Why doesn't it say "#3 /tmp/fact.rb:5" ?

Is this a (small) bug or am I missing something here?

Laurent