在模板函数包装器中处理void返回

您可以使用RAII来使用一个独特的功能:

template <typename F>
struct Finally {
    Finally(F f) : f(f) {}
    ~Finally() { f(); }

    Finally(const Finally&) = delete;
    Finally& operator=(const Finally&) = delete;

    F f;
};

// pre C++17
template <typename F>
Finally<F> make_finally(F f) {
    return {f};
}


template <typename R, typename ...Args>
std::function<R(Args...)> logged(string name, std::function<R(Args...)> f)
{
    return [f, name](Args... args) -> R {
        LOG << name << " start" << NL;
        auto start = std::chrono::high_resolution_clock::now();
        Finally finally([&](){ // C++17
        // auto&& finally = make_finally([&](){ // Pre-C++17
            auto end = std::chrono::high_resolution_clock::now();
            auto total = std::chrono::duration_cast<std::chrono::microseconds>(end - start).count();
            LOG << "Elapsed: " << total << "us" << NL;
        });
        return f(std::forward<Args>(args)...);
    };
}