将variadic模板传递给pthread_create

Question

我知道pthread_create接受void*(*)(void*)参数和void*，所以我已经尝试了2次（失败）来包装函数和args...:

a.创建一个C样式的void*run(Void*)函数，该函数将调用传递给它的std::function对象：

class thread
{
public:
    typedef std::function<void()> functor_t;

    static void* run(void* f) 
    {
        functor_t* functor = (functor_t*)f;
        (*functor)();
        delete functor;
        return nullptr;
    }

    template<typename Callable, typename... Args>
    explicit thread(size_t stack_size, Callable && callable, Args&&... args) {
        auto task_ptr = std::make_shared<std::packaged_task<decltype(callable(args...))()>>(
            std::bind(std::forward<Callable>(callable), std::placeholders::_1, std::forward<Args>(args)...)
            );
        functor_t* functor = new functor_t([task_ptr]() {
            (*task_ptr)();
        });

        pthread_attr_t attr = { 0};
        if (pthread_attr_init(&attr) == 0)
        {
            m_joinable = pthread_attr_setstacksize(&attr, stack_size) == 0 &&
                         pthread_create(&m_id, &attr, &run, functor);
            pthread_attr_destroy(&attr);
        }
    }
private:
    pthread_t   m_id        = -1    ;
    bool        m_joinable  = false ;
};

这会在GCC 4.8.5中导致以下错误：

/usr/include/c++/4.8.2/functional：在'struct std::_bind_simple(std::_placeholder<1>,int))(int*)>>()>'的实例化中：/usr/include/c++/4.8.2/future:1284:55:required from'void std::__future_base::_task_state<_fn,_alloc,_res(_args...)>::_m_run(_args...)[with_args={}]'thread.cpp:17:1:此处必需/usr/include/c++/4.8.2/function:1697:61:错误：在'class std::result_of(std::_placeholder<1>,int))(int*)>>()>'typedef typename result_of<_callable(_args...)>::type result_type；^/usr/include/c++/4.8.2:function:1727:9:错误：在'class_index_tuple<_indexes...>)^

b.以下为http://coliru.stacked-crooked.com/a6c607514601b013

class thread
{
public:
    template< typename Callable, typename... Args >
    explicit thread(size_t stack_size, Callable&& callable, Args&&... args )
    {
        auto l = new auto([=]{ callable(args...); });
        auto te = [](void* rp) -> void*
        {
            auto p = reinterpret_cast<decltype(l)>(rp);
            (*p)();
            delete p;
            return nullptr;
        };
        pthread_attr_t attr = { 0};
        if (pthread_attr_init(&attr) == 0)
        {
            m_joinable = pthread_attr_setstacksize(&attr, stack_size) == 0 &&
                         pthread_create(&m_id, &attr, te, l);
            pthread_attr_destroy(&attr);
        }
    }
private:
    pthread_t   m_id        = -1    ;
    bool        m_joinable  = false ;
};

这应该在clang中工作，但在GCC 4.8.5中失败了，原因是：

infile from thread.cpp:2:0:thread.h:In lambda function:thread.h:82:37:error：参数包未用“...”展开：auto l=new auto([=]{callable（args...）；}）；^thread.h:82:37:注意:
“args”thread.h:82:41:错误：扩展模式“args”不包含参数包auto l=new auto([=]{callable（args...）；}）；^thread.h:在'struct thread::thread(size_t,Callable&&,Args&&...)[with Callable=void()(int)；Args={int*}；size_t=long unsigned int]::__lambda4':thread.h:82:48:
required from'thread::thread(thread_t,Callable&&,Args&&...)[with Callable=void（）(int)；Args={int*}；size_t=long unsigned&&...)::__lambda4::__Args的auto l=新的auto([=]{Callable（Args...）；}）；^thread.h:83:被以前的错误搞糊涂，退出

两人都跑了follwing Main：

int g=5;

void run(int *i)
{
    printf("t\n");
}

int main()
{

    gs_thread t(256*1024, &run, &g);
    printf("m\n");
    t.join();
}

Answer 1

如果从第一个版本中删除std::placeholders::_1，则将使用GCC编译。