C++ 如何卸载openssl引擎C++；

我将gost.dll引擎文件复制到一个临时文件夹中，然后像这样加载它

    if (ENGINE_ctrl_cmd_string(engine_gost, "SO_PATH", szPathToGostDLL.mbc_str(), 0))
    {
        if (ENGINE_ctrl_cmd_string(engine_gost, "ID", szEngineName.mbc_str(), 0))
        {
            if (ENGINE_ctrl_cmd_string(engine_gost, "LOAD", NULL, 0))
                goto ok;
        }
    }

ENGINE_finish(engine_gost);
ENGINE_free(engine_gost);

ERR_remove_state(0);
ERR_free_strings();

ENGINE_cleanup();
EVP_cleanup();

CONF_modules_finish();
CONF_modules_free();
CONF_modules_unload(true);

CRYPTO_cleanup_all_ex_data();

然后我做一些工作，像这样卸载它

    if (ENGINE_ctrl_cmd_string(engine_gost, "SO_PATH", szPathToGostDLL.mbc_str(), 0))
    {
        if (ENGINE_ctrl_cmd_string(engine_gost, "ID", szEngineName.mbc_str(), 0))
        {
            if (ENGINE_ctrl_cmd_string(engine_gost, "LOAD", NULL, 0))
                goto ok;
        }
    }

ENGINE_finish(engine_gost);
ENGINE_free(engine_gost);

ERR_remove_state(0);
ERR_free_strings();

ENGINE_cleanup();
EVP_cleanup();

CONF_modules_finish();
CONF_modules_free();
CONF_modules_unload(true);

CRYPTO_cleanup_all_ex_data();

问题是我无法删除文件gost.dll 如何正确卸载发动机