Rubinius then/else goto tagged as part of else

find_main_script.asm

========== :find_main_script ===========
Arguments:   1 required, 1 total
Locals:      2: i, loc
Stack size:  7
Lines to IP: 19: 0..3, 20: 4..14, 21: 15..28, 22: 29..39, 23: 40..72, 24: 73..87, 26: 88..94, 28: 95..107, 22: 108..109

0000:  cast_for_single_block_arg  
0001:  set_local                  0
0003:  pop                        
0004:  push_local_depth           1, 0
0007:  push_local                 0
0009:  send_stack                 :[], 1
0012:  set_local                  1
0014:  pop                        
0015:  push_literal               "Object#"
0017:  string_dup                 
0018:  push_local                 1
0020:  send_stack                 :describe_receiver, 0
0023:  meta_send_op_equal         :==
0025:  dup_top                    
0026:  goto_if_false              38
0028:  pop                        
0029:  push_literal               :__script__
0031:  push_local                 1
0033:  send_stack                 :name, 0
0036:  meta_send_op_equal         :==
0038:  goto_if_false              108
0040:  push_local                 1
0042:  send_stack                 :method, 0
0045:  send_stack                 :active_path, 0
0048:  push_literal               nil
0050:  dup_top                    
0051:  is_nil                     
0052:  goto_if_false              66
0054:  pop                        
0055:  push_cpath_top             
0056:  find_const                 9
0058:  push_literal               "\\/trepanx$"
0060:  meta_push_0                
0061:  send_stack                 :new, 2
0064:  set_literal                nil
0066:  send_stack                 :=~, 1
0069:  dup_top                    
0070:  goto_if_true               86
0072:  pop                        
0073:  push_local                 1
0075:  send_stack                 :method, 0
0078:  send_stack                 :active_path, 0
0081:  push_literal               "kernel/loader.rb"
0083:  string_dup                 
0084:  meta_send_op_equal         :==
0086:  goto_if_false              95
0088:  push_local                 0
0090:  set_local_depth            1, 1
0093:  goto                       106
0095:  push_local_depth           1, 0
0098:  send_stack                 :size, 0
0101:  push_local                 0
0103:  meta_send_op_minus         :-
0105:  raise_return               
0106:  goto                       109
0108:  push_nil                   
0109:  ret                        
----------------------------------------

trepanx-util.rb

# Copyright (C) 2010, 2011 Rocky Bernstein <rockyb@rubyforge.net>

class Trepan
  module Util

    module_function 
    def safe_repr(str, max, elipsis='... ')
      if str.is_a?(String) && max > 0 && str.size > max && !str.index("\n")
        "%s%s%s" % [ str[0...max/2], elipsis,  str[str.size-max/2..str.size]]
      else
        str
      end
    end

    # Find user portion of script skipping over Rubinius code loading.
    # Unless hidestack is off, we don't show parts of the frame below this.
    def find_main_script(locs)
      candidate = nil
      (locs.size-1).downto(0) do |i|
        loc = locs[i]
        if 'Object#' == loc.describe_receiver &&
            :__script__ == loc.name
          if loc.method.active_path =~ /\/trepanx$/ ||
            loc.method.active_path == 'kernel/loader.rb'
            # Might have been run from standalone trepanx.
            candidate = i
          else
            return locs.size - i
          end
        end
      end
      candidate ? locs.size - candidate - 1 : nil
    end
    module_function :find_main_script
  end
end

if __FILE__ == $0
  include Trepan::Util
  string = 'The time has come to talk of many things.'
  puts safe_repr(string, 50)
  puts safe_repr(string, 17)
  puts safe_repr(string.inspect, 17)
  puts safe_repr(string.inspect, 17, '')
  locs = Rubinius::VM.backtrace(0)
  locs.each_with_index do |l, i| 
    puts "#{i}: #{l.describe}"
  end
  puts "main script in above is #{locs.size() - 1 - find_main_script(locs)}"
end

In find_main_script.asm, note that at offset 93 there is a goto 106 which is the instruction goto 109. 106 however is tagged as being in part of the "else" part of an if/then/else. So we have another instance of misleading location information