# File lib/mkmf.rb, line 970
def dir_config(target, idefault=nil, ldefault=nil)
  if dir = with_config(target + "-dir", (idefault unless ldefault))
    defaults = Array === dir ? dir : dir.split(File::PATH_SEPARATOR)
    idefault = ldefault = nil
  end

  idir = with_config(target + "-include", idefault)
  $arg_config.last[1] ||= "${#{target}-dir}/include"
  ldir = with_config(target + "-lib", ldefault)
  $arg_config.last[1] ||= "${#{target}-dir}/lib"

  idirs = idir ? Array === idir ? idir : idir.split(File::PATH_SEPARATOR) : []
  if defaults
    idirs.concat(defaults.collect {|dir| dir + "/include"})
    idir = ([idir] + idirs).compact.join(File::PATH_SEPARATOR)
  end
  unless idirs.empty?
    idirs.collect! {|dir| "-I" + dir}
    idirs -= Shellwords.shellwords($CPPFLAGS)
    unless idirs.empty?
      $CPPFLAGS = (idirs.quote << $CPPFLAGS).join(" ")
    end
  end

  ldirs = ldir ? Array === ldir ? ldir : ldir.split(File::PATH_SEPARATOR) : []
  if defaults
    ldirs.concat(defaults.collect {|dir| dir + "/lib"})
    ldir = ([ldir] + ldirs).compact.join(File::PATH_SEPARATOR)
  end
  $LIBPATH = ldirs | $LIBPATH

  [idir, ldir]
end