install_location

# File lib/rubygems/package.rb, line 448
  def install_location(filename, destination_dir) # :nodoc:
    raise Gem::Package::PathError.new(filename, destination_dir) if
      filename.start_with? '/'

    destination_dir = File.expand_path(File.realpath(destination_dir))
    destination = File.expand_path(File.join(destination_dir, filename))

    raise Gem::Package::PathError.new(destination, destination_dir) unless
      destination.start_with? destination_dir + '/'

    begin
      real_destination = File.expand_path(File.realpath(destination))
    rescue
      # it's fine if the destination doesn't exist, because rm -rf'ing it can't cause any damage
      nil
    else
      raise Gem::Package::PathError.new(real_destination, destination_dir) unless
        real_destination.start_with? destination_dir + '/'
    end

    destination.untaint
    destination
  end