From: Jan Svitok <jan.svitok@...>
Date: 2006-10-26T19:56:01+09:00
Subject: Re: ruby-prof vs. Object#clone

On 10/26/06, Victor 'Zverok' Shepelev <vshepelev@imho.com.ua> wrote:
> For some reasons I extensively use this technique:
>
> obj = MyClass.new(...)
> obj.instance_eval{
>   def my_cool_method
>   end
> }
>
> #create 1000 clones of the obj, call #my_cool_method
> (1..1000).collect{
>   clon = obj.clone
>   clon.my_cool_method
> }
>
> The problem is ruby-prof shows each clone's #my_cool_method as separate one in the report, so I see 1000 lines with 1 calls of #my_cool_method instead of 1 line with 1000 calls. Is it bug or by design? May this problem be result of the fact I use latest Ruby 1.9 version?

This is what I've found in the sources:
My_cool_method is a singleton instance method (not an ordinary
instance method). singleton methods are cloned by creating proxy
method, so they are not identical.

object.c: rb_obj_clone()
class.c : rb_singleton_class_clone() and clone_method()

try:

o1 = Object.new
# this creates singleton method
o1.instance_eval { def m ; end }

o2 = o1.clone

p o1.method(:m)   #=> #<Method: #<Object:0x393c328>.m>
p o2.method(:m)   #=> #<Method: #<Object:0x393c198>(#<Object:0x393c328>).m>

o3 = o1.clone
p o3.method(:m)   #=> #<Method: #<Object:0x393bcd4>(#<Object:0x393c328>).m>

# now this creates normal method:
o1.class.module_eval { def c ; end }
p o1.method(:c)   #=> #<Method: Object#c>
p o2.method(:c)   #=> #<Method: Object#c>
p o3.method(:c)   #=> #<Method: Object#c>

However it should be possible to patch ruby-prof to take account for this.

IMHO the most simple way is to define normal instance methods via

obj.class.module_eval, i.e. MyClass.module_eval.

(Please note that I might be wrong, I'm no expert on ruby internals,
this is what I learned in a few minutes looking into sources...)