Question

我试图解决c ++ 11 lambda-capture限制问题。

以下代码与visual studio 2013一起运行，但不与g ++（无效字段错误）一起运行。代码有什么问题？我该如何解决呢？

template <typename T>
struct move_on_copy
{
    using T_t = typename std::remove_reference<T>::type;
    mutable T_t _val;

    move_on_copy(){}

    move_on_copy(T_t&& v):_val(std::move(v)){}
    move_on_copy(move_on_copy const& v):_val(std::move(v._val)){}
    move_on_copy& operator=(move_on_copy const& v)
    { _val =std::move(v._val); return *this; }
};

//...
auto tt = move_on_copy<Packaged_Task<R2()>>(std::move(task));
auto work = [tt](){tt._val();}; //compiler error here

完整错误消息：

/home/christofmatthaei/Desktop/untitled folder/trunk/Concurrency/inc/Concurrency/ThreadPool/Future.h: In instantiation of ‘struct it::crc::Future<R>::then(F) [with F = it::crc::when_all(InputIterator, InputIterator) [with InputIterator = std::_List_iterator<it::crc::Future<int> >; decltype (begin->.get()) = int]::<lambda(it::crc::Future<int>&&)>; R = int; typename it::crc::callable_traits<F>::return_type = std::vector<it::crc::Future<int>, std::allocator<it::crc::Future<int> > >]::<lambda()>’:
/home/christofmatthaei/Desktop/untitled folder/trunk/Concurrency/inc/Concurrency/ThreadPool/Future.h:303:33:   required from ‘it::crc::Future<typename it::crc::callable_traits<F>::return_type> it::crc::Future<R>::then(F) [with F = it::crc::when_all(InputIterator, InputIterator) [with InputIterator = std::_List_iterator<it::crc::Future<int> >; decltype (begin->.get()) = int]::<lambda(it::crc::Future<int>&&)>; R = int; typename it::crc::callable_traits<F>::return_type = std::vector<it::crc::Future<int>, std::allocator<it::crc::Future<int> > >]’
/home/christofmatthaei/Desktop/untitled folder/trunk/Concurrency/inc/Concurrency/ThreadPool/When.h:29:21:   required from ‘it::crc::Future<std::vector<it::crc::Future<decltype (begin->.get())> > > it::crc::when_all(InputIterator, InputIterator) [with InputIterator = std::_List_iterator<it::crc::Future<int> >; decltype (begin->.get()) = int]’
/home/christofmatthaei/Desktop/untitled folder/trunk/Concurrency/test/Future.cpp:253:62:   required from here
/home/christofmatthaei/Desktop/untitled folder/trunk/Concurrency/inc/Concurrency/ThreadPool/Future.h:303:17: **error: using invalid field** ‘it::crc::Future<R>::then(F)::<lambda()>::<tt capture>’
    auto work = [tt](){tt._val();};

修改我在5.3.1版上使用g ++

进入c ++ 11中的lambda表达式

0 个答案: