strcat

    inline std::wostream& StrCatImp(int& i, std::wostream& out) {
        return out;
    }

    template <class First, class... Rest>
    inline std::wostream& StrCatImp(std::wostream& out, First&& f,
        Rest&&... rest) {
            out << std::forward<First>(f);
        return StrCatImp(out, std::forward<Rest>(rest)...);
    }

    template <class... Args>
    inline void LOG(Args&&... args) {
        std::wostringstream ss;
        StrCatImp(ss, std::forward<Args>(args)...);
        trace(ss.str());  //转接到自己的输出
    }