static bool
  extract_big_integer (emacs_env *env, emacs_value arg, mpz_t result)
  {
    int sign;
    unsigned long u;
    ptrdiff_t count = env->extract_big_integer (env, arg, &sign, 1, &u);
    if (count <= 1)
      mpz_set_ui (result, u);
    else
      {
	emacs_limb_t *magnitude
	  = _Generic (*mpz_limbs_write (result, count),
		      emacs_limb_t: mpz_limbs_write (result, count),
		      default: checked_malloc (count * sizeof *magnitude));
	env->extract_big_integer (env, arg, &sign, count, magnitude);
	if (_Generic (*mpz_limbs_write (result, count),
		      emacs_limb_t:
		        (mpz_limbs_finish (result, sign < 0 ? -count : count),
		         true),
		      default: false))
	  return true;
	mpz_import (result, count, -1, sizeof *magnitude, 0, 0, magnitude);
	free (magnitude);
      }

    if (sign < 0)
      mpz_neg (result, result);
    return true;
  }