Boost可选Boost线程编译问题

Question

我的环境是Visual Stuido 2013，VC12，Boost 1.59。 下面的代码（真正的代码，最小的摄制）：

#include "boost/thread.hpp" 
#include "boost/optional.hpp" 

class MyClass 
{ 
public: 

    template <typename T> 
    operator const T&() const; 

}; 

boost::optional<MyClass> foo() 
{ 
    boost::optional<MyClass> res; 
    return res; 
} 

int main(int argc) 
{ 
    foo(); 
} 

无法编译，错误：

 
    1>------ Build started: Project: TestBoostOptional, Configuration: Debug x64 ------ 
    1> main.cpp 
    1>c:\workspace\third_party\boost_1_59_0\boost/optional/optional.hpp(297): error C2664: 'void boost::optional_detail::optional_base::construct(MyClass &&)' : cannot convert argument 1 from 'boost::detail::thread_move_t' to 'const MyClass &' 
    1>   with 
    1>   [ 
    1>    T=MyClass 
    1>   ] 
    1>   Reason: cannot convert from 'boost::detail::thread_move_t' to 'const MyClass' 
    1>   with 
    1>   [ 
    1>    T=MyClass 
    1>   ] 
    1>   No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called 
    1>   c:\workspace\third_party\boost_1_59_0\boost/optional/optional.hpp(292) : while compiling class template member function 'boost::optional_detail::optional_base::optional_base(boost::optional_detail::optional_base &&)' 
    1>   with 
    1>   [ 
    1>    T=MyClass 
    1>   ] 
    1>   c:\workspace\third_party\boost_1_59_0\boost/optional/optional.hpp(873) : see reference to function template instantiation 'boost::optional_detail::optional_base::optional_base(boost::optional_detail::optional_base &&)' being compiled 
    1>   with 
    1>   [ 
    1>    T=MyClass 
    1>   ] 
    1>   c:\workspace\third_party\boost_1_59_0\boost/optional/optional.hpp(766) : see reference to class template instantiation 'boost::optional_detail::optional_base' being compiled 
    1>   with 
    1>   [ 
    1>    T=MyClass 
    1>   ] 
    1>   main.cpp(14) : see reference to class template instantiation 'boost::optional' being compiled 

注意#include "boost/thread.hpp"。删除代码时包括代码编译。任何可以解决的办法？

Answer 1

在使用任何boost头之前，您必须定义BOOST_THREAD_USES_MOVE。

#define BOOST_THREAD_USES_MOVE 

更多信息位于here。这个定义模仿了Boost.Move这个在这里需要的移动。

In order to implement Movable classes, move parameters and return types Boost.Thread uses the rvalue reference when the compiler support it. On compilers not supporting it Boost.Thread uses either the emulation provided by Boost.Move or the emulation provided by the previous versions of Boost.Thread depending whether BOOST_THREAD_USES_MOVE is defined or not. This macros is unset by default when BOOST_THREAD_VERSION is 2. Since BOOST_THREAD_VERSION 3, BOOST_THREAD_USES_MOVE is defined.

另见Boost.Move：

Boost.Thread uses by default an internal move semantic implementation. Since version 3.0.0 you can use the move emulation emulation provided by Boost.Move.

When BOOST_THREAD_VERSION==2 define BOOST_THREAD_USES_MOVE if you want to use Boost.Move interface. When BOOST_THREAD_VERSION==3 define BOOST_THREAD_DONT_USE_MOVE if you don't want to use Boost.Move interface.