void printLuaStack(lua_State* lua) {

    pln("========= content of stack from top to bottom: ===========");

    int stackSize = lua_gettop(lua);                    // 获得栈中元素个数
    for (int i=stackSize; i>0; --i) {
        pv("%d [%d]\t", i, -1 - (stackSize - i));
        int t = lua_type(lua, i);                       // 判断当前元素类型
        switch (t) {
            case LUA_TNUMBER:
                pv("%s: \t%.2f\n", lua_typename(lua, t), lua_tonumber(lua, i));     // 打印类型名称和值
                break;
            case LUA_TBOOLEAN:
                pv("%s: \t%d\n", lua_typename(lua, t), lua_toboolean(lua, i));
                break;
            case LUA_TSTRING:
                pv("%s: \t%s\n", lua_typename(lua, t), lua_tostring(lua, i));
                break;
            default:
                // LUA_TTABLE
                // LUA_TTHREAD
                // LUA_TFUNCTION
                // LUA_TLIGHTUSERDATA
                // LUA_TUSERDATA
                // LUA_TNIL
                pv("%s\n", lua_typename(lua, t));                                   // 不好打印的类型，暂时仅打印类型名称
                break;
        }
    }
    psln(stackSize);
}