diff --git a/lib/asm/arm/arm_assembler.rb b/lib/asm/arm/arm_assembler.rb
index 8346df63..d71b7255 100644
--- a/lib/asm/arm/arm_assembler.rb
+++ b/lib/asm/arm/arm_assembler.rb
@@ -25,6 +25,9 @@ module Asm
       case type
       when R_ARM_PC24
         diff = addr - io.tell - 8
+        if (diff.abs > (1 << 25))
+          raise Asm::AssemblyError.new('offset too large for R_ARM_PC24 relocation', nil)
+        end
         packed = [diff >> 2].pack('l')
         io << packed[0,3]
       when R_ARM_ABS32
@@ -33,8 +36,7 @@ module Asm
       when R_ARM_PC12
         diff = addr - io.tell - 8
         if (diff.abs > 2047)
-          raise Asm::AssemblyError.new('offset too large for R_ARM_PC12 relocation',
-                                      nil)
+          raise Asm::AssemblyError.new('offset too large for R_ARM_PC12 relocation', nil)
         end
       
         val = diff.abs
diff --git a/lib/asm/arm/code_generator.rb b/lib/asm/arm/code_generator.rb
index 449bc71a..792d0d0f 100644
--- a/lib/asm/arm/code_generator.rb
+++ b/lib/asm/arm/code_generator.rb
@@ -4,7 +4,7 @@ require_relative 'generator_label'
 require 'asm/nodes'
 require 'stream_reader'
 require 'stringio'
-
+require "asm/data_object"
     
 class Asm::Arm::CodeGenerator
   def initialize
@@ -82,7 +82,7 @@ class Asm::Arm::CodeGenerator
     if (lbl = @externs.find { |extern| extern.name == sym })
       lbl
     else
-      @externs << lbl = GeneratorExternLabel.new(sym)
+      @externs << lbl = Asm::Arm::GeneratorExternLabel.new(sym)
       @asm.add_object lbl
       lbl
     end
diff --git a/lib/asm/assembler.rb b/lib/asm/assembler.rb
index 2c949428..3a2a8d3f 100644
--- a/lib/asm/assembler.rb
+++ b/lib/asm/assembler.rb
@@ -8,7 +8,6 @@ module Asm
     def initialize
       @objects = []
       @label_objects = []
-      @label_callbacks = []
       @relocations = []
     end
     attr_reader :relocations, :objects
@@ -21,10 +20,6 @@ module Asm
       @relocations << Asm::Relocation.new(*args)
     end
 
-    def register_label_callback(label, io_pos, &block)
-      @label_callbacks << [label, io_pos, block]
-    end
-
     def assemble(io)
       @objects.each do |obj|
         obj.assemble io, self