Don't try to undef object_id.

lib/rbench/report.rb

@@ -1,22 +1,22 @@
 module RBench
   class Report
     self.instance_methods.each do |m|
-      send(:undef_method, m) unless m =~ /^(__|is_a?|kind_of?|respond_to?|hash|inspect|instance_eval|eql?)/
+      send(:undef_method, m) unless m =~ /^(__|is_a?|kind_of?|respond_to?|hash|inspect|instance_eval|object_id|eql?)/
     end
-    
+
     attr_reader :name, :cells
-    
+
     def initialize(runner, group, name, times=nil,&block)
       @runner = runner
       @group  = group
       @name   = name
       @times  = (times || runner.times).ceil
       @cells  = {}
-      @block  = block 
-      
+      @block  = block
+
       # Setting the default for all cells
       runner.columns.each {|c| @cells[c.name] = c.name == :times ? "x#{@times}" : c.default }
-      
+
       new_self = (class << self; self end)
       @runner.columns.each do |column|
         new_self.class_eval <<-CLASS
@@ -26,7 +26,7 @@ def #{column.name}(val=nil,&block)
         CLASS
       end
     end
-    
+
     def run
       # runs the actual benchmarks. If there is only one column, just evaluate the block itself.
       if @runner.columns.length == 1
@@ -37,17 +37,17 @@ def run
       # puts its row now that it is complete
       puts to_s
     end
-    
+
     def to_s
       out = "%-#{@runner.desc_width}s" % name
       @runner.columns.each do |column|
         value = @cells[column.name]
         value = @cells.values_at(*value) if value.is_a?(Array)
         value = nil if value.is_a?(Array) && value.compact.length != 2
-        
+
         out << column.to_s(value)
       end
       out << @runner.newline
     end
   end
-end
+end