C++ 将函数和参数传递给线程

问题陈述-tl；dr
将数字添加到向量，然后输出它们

详细信息

我的意图是创建一个类

Foo

，它包含一个

std:：vector

，我可以用线程安全的方式填充它。我创建了一个

AddValue

方法，允许向该向量添加值，同时牢记线程安全性

std::mutex mt;
class Foo
{
public:
    void AddValue(int i)
    {
        std::lock_guard<std::mutex> lg{ mt };
        values.push_back(i);
    }

    void PrintValues() const
    {
        for (int i : values)
        {
            std::cout << i << " ";
        }
    }

private:
    std::vector<int> values;
};

我的意图是将以下值添加到向量中（由于线程计时，它们以任何顺序结束）

下面是一个快速测试，看看这是否有效

int main()
{
    Foo foo;
    std::vector<std::thread> threads;
    for (int i = 1; i < 5; ++i)
    {
        threads.emplace_back(Func, foo, i);
    }

    std::for_each(begin(threads), end(threads), [](std::thread& t){ t.join(); });

    foo.PrintValues();
}

intmain（）
{
富富,；
向量线程；
对于（int i=1；i<5；++i）
{
线程。向后放置（Func、foo、i）；
}
std:：for_each（开始（线程）、结束（线程），[]（std:：thread&t）{t.join（）；}）；
foo.PrintValues（）；
}

问题
上述代码

这是错误消息

In file included from /usr/include/c++/4.9/mutex:42:0,
                 from 3:
/usr/include/c++/4.9/functional: In instantiation of 'struct std::_Bind_simple<void (*(Foo, int))(Foo&, int)>':
/usr/include/c++/4.9/thread:140:47:   required from 'std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = void (&)(Foo&, int); _Args = {Foo&, int&}]'
/usr/include/c++/4.9/ext/new_allocator.h:120:4:   required from 'void __gnu_cxx::new_allocator< <template-parameter-1-1> >::construct(_Up*, _Args&& ...) [with _Up = std::thread; _Args = {void (&)(Foo&, int), Foo&, int&}; _Tp = std::thread]'
/usr/include/c++/4.9/bits/alloc_traits.h:253:4:   required from 'static std::_Require<typename std::allocator_traits<_Alloc>::__construct_helper<_Tp, _Args>::type> std::allocator_traits<_Alloc>::_S_construct(_Alloc&, _Tp*, _Args&& ...) [with _Tp = std::thread; _Args = {void (&)(Foo&, int), Foo&, int&}; _Alloc = std::allocator<std::thread>; std::_Require<typename std::allocator_traits<_Alloc>::__construct_helper<_Tp, _Args>::type> = void]'
/usr/include/c++/4.9/bits/alloc_traits.h:399:57:   required from 'static decltype (_S_construct(__a, __p, (forward<_Args>)(std::allocator_traits::construct::__args)...)) std::allocator_traits<_Alloc>::construct(_Alloc&, _Tp*, _Args&& ...) [with _Tp = std::thread; _Args = {void (&)(Foo&, int), Foo&, int&}; _Alloc = std::allocator<std::thread>; decltype (_S_construct(__a, __p, (forward<_Args>)(std::allocator_traits::construct::__args)...)) = <type error>]'
/usr/include/c++/4.9/bits/vector.tcc:97:40:   required from 'void std::vector<_Tp, _Alloc>::emplace_back(_Args&& ...) [with _Args = {void (&)(Foo&, int), Foo&, int&}; _Tp = std::thread; _Alloc = std::allocator<std::thread>]'
44:42:   required from here
/usr/include/c++/4.9/functional:1665:61: error: no type named 'type' in 'class std::result_of<void (*(Foo, int))(Foo&, int)>'
       typedef typename result_of<_Callable(_Args...)>::type result_type;
                                                             ^
/usr/include/c++/4.9/functional:1695:9: error: no type named 'type' in 'class std::result_of<void (*(Foo, int))(Foo&, int)>'
         _M_invoke(_Index_tuple<_Indices...>)
         ^

在/usr/include/c++/4.9/mutex:42:0中包含的文件中，
从3开始：
/usr/include/c++/4.9/functional:在“struct std:：_Bind_simple”的实例化中：
/usr/include/c++/4.9/thread:140:47:从'std:：thread:：thread（_Callable&&，_Args&&&…[with _Callable=void（&）（Foo&，int）；_Args={Foo&，int&}]中需要
/usr/include/c++/4.9/ext/new_allocator.h:120:4:void\u gnu\u cxx:：new_allocator中的必填项：：construct（_Up*，_Args&&…[with _Up=std:：thread；_Args={void（&）（Foo&，int），Foo&，int&}；_Tp=std:：thread]'
/usr/include/c++/4.9/bits/alloc_traits.h:253:4:static std:：_requirestd:：allocator_traits:：_S_构造（_alloc&，_Tp*，_Args&…[带_Tp=std:：thread；_Args={void（&）（Foo&，int），Foo&，int&}；_alloc=std:：alloc:：allocator；std:_Require=void]）
/usr/include/c++/4.9/bits/alloc_traits.h:399:57:static decltype（__a，__p，（forward）（std:：allocator_traits:：construct:：__args））std:：allocator_traits:：construct（_-alloc，_-Tp*，_-args&…[带_-Tp=std:：thread；_-args={-void（&）（Foo&，int），Foo&，int&），int&，int&；)allocator&；)std:：allocator&；)构造（)decu:：allocator&（_a，_p，（forward）（std:：allocator_traits:：construct:：_args））=]'
/usr/include/c++/4.9/bits/vector.tcc:97:40:void std：：vector：：emplace_back（_Args&&…）[with _Args={void（&）（Foo&，int），Foo&，int&}；_Tp=std:：thread；_Alloc=std:：Alloc:：allocator]中的必需项
44:42：从这里开始需要
/usr/include/c++/4.9/functional:1665:61:错误：在'class std:：result_of'中没有名为'type'的类型
typedef typename result_of:：type result_type；
^
/usr/include/c++/4.9/functional:1695:9:错误：在“class std:：result_of”中没有名为“type”的类型
_M_invoke（_Index_tuple）
^

---

我不太理解这个错误消息。我没有正确地将线程添加到向量

threads

中吗？

您必须将

foo

包装在

std:：ref

中。没有该包装器，线程不允许通过引用传递内容。

您可能必须将

foo

包装在

std:：ref

中ds不允许在没有包装器的情况下通过引用传递内容。这是一条非常模糊的错误消息。@Carcigenicate你完全正确，解决了它！很好。我喜欢在黑暗中拍摄。我的经验法则是，如果正在线程化的函数有一个带有

&

的参数，那么我应该有一个相应的

std:：ref（）

int main()
{
    Foo foo;
    std::vector<std::thread> threads;
    for (int i = 1; i < 5; ++i)
    {
        threads.emplace_back(Func, foo, i);
    }

    std::for_each(begin(threads), end(threads), [](std::thread& t){ t.join(); });

    foo.PrintValues();
}

In file included from /usr/include/c++/4.9/mutex:42:0,
                 from 3:
/usr/include/c++/4.9/functional: In instantiation of 'struct std::_Bind_simple<void (*(Foo, int))(Foo&, int)>':
/usr/include/c++/4.9/thread:140:47:   required from 'std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = void (&)(Foo&, int); _Args = {Foo&, int&}]'
/usr/include/c++/4.9/ext/new_allocator.h:120:4:   required from 'void __gnu_cxx::new_allocator< <template-parameter-1-1> >::construct(_Up*, _Args&& ...) [with _Up = std::thread; _Args = {void (&)(Foo&, int), Foo&, int&}; _Tp = std::thread]'
/usr/include/c++/4.9/bits/alloc_traits.h:253:4:   required from 'static std::_Require<typename std::allocator_traits<_Alloc>::__construct_helper<_Tp, _Args>::type> std::allocator_traits<_Alloc>::_S_construct(_Alloc&, _Tp*, _Args&& ...) [with _Tp = std::thread; _Args = {void (&)(Foo&, int), Foo&, int&}; _Alloc = std::allocator<std::thread>; std::_Require<typename std::allocator_traits<_Alloc>::__construct_helper<_Tp, _Args>::type> = void]'
/usr/include/c++/4.9/bits/alloc_traits.h:399:57:   required from 'static decltype (_S_construct(__a, __p, (forward<_Args>)(std::allocator_traits::construct::__args)...)) std::allocator_traits<_Alloc>::construct(_Alloc&, _Tp*, _Args&& ...) [with _Tp = std::thread; _Args = {void (&)(Foo&, int), Foo&, int&}; _Alloc = std::allocator<std::thread>; decltype (_S_construct(__a, __p, (forward<_Args>)(std::allocator_traits::construct::__args)...)) = <type error>]'
/usr/include/c++/4.9/bits/vector.tcc:97:40:   required from 'void std::vector<_Tp, _Alloc>::emplace_back(_Args&& ...) [with _Args = {void (&)(Foo&, int), Foo&, int&}; _Tp = std::thread; _Alloc = std::allocator<std::thread>]'
44:42:   required from here
/usr/include/c++/4.9/functional:1665:61: error: no type named 'type' in 'class std::result_of<void (*(Foo, int))(Foo&, int)>'
       typedef typename result_of<_Callable(_Args...)>::type result_type;
                                                             ^
/usr/include/c++/4.9/functional:1695:9: error: no type named 'type' in 'class std::result_of<void (*(Foo, int))(Foo&, int)>'
         _M_invoke(_Index_tuple<_Indices...>)
         ^