class Gem::Ext::ExtConfBuilder

# File rubygems/ext/ext_conf_builder.rb, line 16
def self.build(extension, dest_path, results, args=[], lib_dir=nil)
  tmp_dest = Dir.mktmpdir(".gem.", ".")

  # Some versions of `mktmpdir` return absolute paths, which will break make
  # if the paths contain spaces. However, on Ruby 1.9.x on Windows, relative
  # paths cause all C extension builds to fail.
  #
  # As such, we convert to a relative path unless we are using Ruby 1.9.x on
  # Windows. This means that when using Ruby 1.9.x on Windows, paths with
  # spaces do not work.
  #
  # Details: https://github.com/rubygems/rubygems/issues/977#issuecomment-171544940
  tmp_dest = get_relative_path(tmp_dest)

  Tempfile.open %w"siteconf .rb", "." do |siteconf|
    siteconf.puts "require 'rbconfig'"
    siteconf.puts "dest_path = #{tmp_dest.dump}"
    %w[sitearchdir sitelibdir].each do |dir|
      siteconf.puts "RbConfig::MAKEFILE_CONFIG['#{dir}'] = dest_path"
      siteconf.puts "RbConfig::CONFIG['#{dir}'] = dest_path"
    end

    siteconf.close

    destdir = ENV["DESTDIR"]

    begin
      cmd = Gem.ruby.shellsplit << "-I" << File.expand_path("../../..", __FILE__) <<
            "-r" << get_relative_path(siteconf.path) << File.basename(extension)
      cmd.push(*args)

      begin
        run(cmd, results) do |s, r|
          if File.exist? 'mkmf.log'
            unless s.success?
              r << "To see why this extension failed to compile, please check" \
                " the mkmf.log which can be found here:\n"
              r << "  " + File.join(dest_path, 'mkmf.log') + "\n"
            end
            FileUtils.mv 'mkmf.log', dest_path
          end
        end
        siteconf.unlink
      end

      ENV["DESTDIR"] = nil

      make dest_path, results

      if tmp_dest
        # TODO remove in RubyGems 3
        if Gem.install_extension_in_lib and lib_dir
          FileUtils.mkdir_p lib_dir
          entries = Dir.entries(tmp_dest) - %w[. ..]
          entries = entries.map { |entry| File.join tmp_dest, entry }
          FileUtils.cp_r entries, lib_dir, :remove_destination => true
        end

        FileEntry.new(tmp_dest).traverse do |ent|
          destent = ent.class.new(dest_path, ent.rel)
          destent.exist? or FileUtils.mv(ent.path, destent.path)
        end
      end
    ensure
      ENV["DESTDIR"] = destdir
      siteconf.close!
    end
  end

  results
ensure
  FileUtils.rm_rf tmp_dest if tmp_dest
end

# File rubygems/ext/ext_conf_builder.rb, line 92
def self.get_relative_path(path)
  path[0..Dir.pwd.length - 1] = '.' if path.start_with?(Dir.pwd)
  path
end