fix bad scoping bug

lib/arm/instruction.rb

@@ -15,25 +15,34 @@ module Arm
     def opcode
       @attributes[:opcode]
     end
-  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
-
-  # TODDO: review (don't remember what the "set_" stuff was for)
-  def method_missing name , *args , &block 
-    return super unless (args.length <= 1) or block_given?
-    set , attribute = name.to_s.split("set_")
-    if set == ""
-      @attributes[attribute.to_sym] = args[0] || 1
-      return self 
-    else
-      return super
+    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
-    return @attributes[name.to_sym]
-  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
+
+    # TODDO: review (don't remember what the "set_" stuff was for)
+    def method_missing name , *args , &block 
+      return super unless (args.length <= 1) or block_given?
+      set , attribute = name.to_s.split("set_")
+      if set == ""
+        @attributes[attribute.to_sym] = args[0] || 1
+        return self 
+      else
+        return super
+      end
+      return @attributes[name.to_sym]
+    end
+  end
 end
 
 require_relative "constants"