# File lib/mkmf.rb, line 1459
def init_mkmf(config = CONFIG)
  $makefile_created = false
  $arg_config = []
  $enable_shared = config['ENABLE_SHARED'] == 'yes'
  $defs = []
  $extconf_h = nil
  $CFLAGS = with_config("cflags", arg_config("CFLAGS", config["CFLAGS"])).dup
  $ARCH_FLAG = with_config("arch_flag", arg_config("ARCH_FLAG", config["ARCH_FLAG"])).dup
  $CPPFLAGS = with_config("cppflags", arg_config("CPPFLAGS", config["CPPFLAGS"])).dup
  $LDFLAGS = with_config("ldflags", arg_config("LDFLAGS", config["LDFLAGS"])).dup
  $INCFLAGS = "-I$(topdir) -I$(hdrdir) -I$(srcdir)"
  $DLDFLAGS = with_config("dldflags", arg_config("DLDFLAGS", config["DLDFLAGS"])).dup
  $LIBEXT = config['LIBEXT'].dup
  $OBJEXT = config["OBJEXT"].dup
  $LIBS = "#{config['LIBS']} #{config['DLDLIBS']}"
  $LIBRUBYARG = ""
  $LIBRUBYARG_STATIC = config['LIBRUBYARG_STATIC']
  $LIBRUBYARG_SHARED = config['LIBRUBYARG_SHARED']
  $DEFLIBPATH = $extmk ? ["$(topdir)"] : CROSS_COMPILING ? [] : ["$(libdir)"]
  $DEFLIBPATH.unshift(".")
  $LIBPATH = []
  $INSTALLFILES = nil

  $objs = nil
  $srcs = nil
  $libs = ""
  if $enable_shared or Config.expand(config["LIBRUBY"].dup) != Config.expand(config["LIBRUBY_A"].dup)
    $LIBRUBYARG = config['LIBRUBYARG']
  end

  $LOCAL_LIBS = ""

  $cleanfiles = config_string('CLEANFILES') {|s| Shellwords.shellwords(s)} || []
  $cleanfiles << "mkmf.log"
  $distcleanfiles = config_string('DISTCLEANFILES') {|s| Shellwords.shellwords(s)} || []

  $extout ||= nil
  $extout_prefix ||= nil

  $arg_config.clear
  dir_config("opt")
end