From: Paul Brannan <pbrannan@...>
Date: 2001-10-03T23:07:51+09:00
Subject: [ruby-talk:22002] Backtrace with eval

I've noticed that when I use eval, I get a backtrace that is very
un-useful.  Consider this program:

  def foo
    raise "foo!"
  end

  def bar
    foo
  end

  def do_test
    begin
      proc.call
    rescue Exception
      puts $!, $!.backtrace
    end
  end

  do_test do
    eval "bar"
  end

  do_test do
    __send__ "bar"
  end

The first do_test block (using eval) gives me:

  bt.rb:2:in `foo': foo!
  bt.rb:18
  bt.rb:18:in `eval'
  bt.rb:18
  bt.rb:18:in `call'
  bt.rb:11:in `do_test'
  bt.rb:18

And the second do_test block (using __send__) gives me:

  foo!
  bt.rb:2:in `foo'
  bt.rb:6:in `bar'
  bt.rb:24:in `__send__'
  bt.rb:24
  bt.rb:24:in `call'
  bt.rb:11:in `do_test'
  bt.rb:24

Questions:

1) Why does eval not give me a proper backtrace?  (I would much prefer to
use eval over __send__, since security/speed are not issues for what I'm
writing, and eval doesn't allow me to do evil things like call private
methods in objects that I don't have access to).

2) Why does using eval give me "bt.rb:2:in `foo': foo!" while using
__send__ gives me "foo!\nbt.rb:2:in `foo'"?  This seems a little
inconsistent.

3) What's with the blank lines "bt.rb:18" and "bt.rb:24"?

Thanks,

Paul