fix bad scoping bug

lib/arm/instruction.rb

@@ -15,8 +15,17 @@ module Arm
     def opcode
       @attributes[:opcode]
     end
+    def position
+      raise "position accessed but not set at #{length} for #{self.inspect}" if @position == nil
+      @position
+    end
+    def set_position pos
+      # resetting of position used to be error, but since relink and dynamic instruction size it is ok. in measures
+      if @position != nil and ((@position - pos).abs > 32)
+        raise "position set again #{pos}!=#{@position} for #{self}" 
+      end
+      @position = pos
     end
-
 
     # this is giving read access to the attributes hash via .attibute syntax
     # so for an instruction pop you can write pop.opcode to get the :opcode attribute
@@ -33,7 +42,7 @@ module Arm
       end
       return @attributes[name.to_sym]
     end
-
+  end
 end
 
 require_relative "constants"