std :: reference_wrapper中的Visual C++ 10.0错误？

Question

码:

#include <functional>

struct Foo
{
    virtual void mf() = 0;
};

struct Bar: Foo
{
    virtual void mf() {}
};

int main()
{
    Bar o;
    std::reference_wrapper<Foo const> wrapper( o );
}

MinGW g ++ 4.6.1的结果:

[d:\dev\test]
> g++ foo.cpp -std=c++0x

[d:\dev\test]
> _

Visual C++ 10.0的结果:

[d:\dev\test]
> cl foo.cpp
foo.cpp
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xxcallwrap(8) : error C2259: 'Foo' : cannot instantiate abstract class
        due to following members:
        'void Foo::mf(void)' : is abstract
        foo.cpp(5) : see declaration of 'Foo::mf'
        C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xrefwrap(371) : see reference to class template instantiation 'std::tr1::_Call_wrapper' being compiled
        with
        [
            _Callable=std::tr1::_Callable_obj
        ]
        C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xrefwrap(416) : see reference to class template instantiation 'std::tr1::_Refwrap_impl' being compiled
        with
        [
            _Ty=const Foo
        ]
        foo.cpp(16) : see reference to class template instantiation 'std::tr1::reference_wrapper' being compiled
        with
        [
            _Ty=const Foo
        ]
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xxcallwrap(8) : error C2027: use of undefined type 'std::
tr1::_Result_of'
        with
        [
            _Ty=const Foo (void)
        ]
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xxcallwrap(9) : error C2143: syntax error : missing ';' before '('
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xxcallwrap(9) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xxcallwrap(10) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xxcallwrap(8) : error C2259: 'Foo' : cannot instantiate abstract class
        due to following members:
        'void Foo::mf(void)' : is abstract
        foo.cpp(5) : see declaration of 'Foo::mf'
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xxcallwrap(8) : error C2259: 'Foo' : cannot instantiate abstract class
        due to following members:
        'void Foo::mf(void)' : is abstract
        foo.cpp(5) : see declaration of 'Foo::mf'
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xxcallwrap(8) : error C2259: 'Foo' : cannot instantiate abstract class
        due to following members:
        'void Foo::mf(void)' : is abstract
        foo.cpp(5) : see declaration of 'Foo::mf'
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xxcallwrap(8) : error C2259: 'Foo' : cannot instantiate abstract class
        due to following members:
        'void Foo::mf(void)' : is abstract
        foo.cpp(5) : see declaration of 'Foo::mf'
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xxcallwrap(8) : error C2259: 'Foo' : cannot instantiate abstract class
        due to following members:
        'void Foo::mf(void)' : is abstract
        foo.cpp(5) : see declaration of 'Foo::mf'
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xxcallwrap(8) : error C2259: 'Foo' : cannot instantiate abstract class
        due to following members:
        'void Foo::mf(void)' : is abstract
        foo.cpp(5) : see declaration of 'Foo::mf'
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xxcallwrap(8) : error C2259: 'Foo' : cannot instantiate abstract class
        due to following members:
        'void Foo::mf(void)' : is abstract
        foo.cpp(5) : see declaration of 'Foo::mf'
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xxcallwrap(8) : error C2259: 'Foo' : cannot instantiate abstract class
        due to following members:
        'void Foo::mf(void)' : is abstract
        foo.cpp(5) : see declaration of 'Foo::mf'
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xxcallwrap(8) : error C2259: 'Foo' : cannot instantiate abstract class
        due to following members:
        'void Foo::mf(void)' : is abstract
        foo.cpp(5) : see declaration of 'Foo::mf'
C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\INCLUDE\xxcallwrap(8) : error C2259: 'Foo' : cannot instantiate abstract class
        due to following members:
        'void Foo::mf(void)' : is abstract
        foo.cpp(5) : see declaration of 'Foo::mf'

[d:\dev\test]
> _

我喜欢Visual C++编译器11次告诉用户抽象类无法实例化的方式,只是为了点回家,就像用户不知道那样.但是应该std::reference_wrapper真正实例化这个类吗？是没有太大的(通过传递)参考点的不要求实例？

也就是说,正如我强烈怀疑的那样,这是Visual C++标准库实现中的一个错误吗？

Answer 1

由问题作者解决。这是Visual C++ 10.0 中的一个错误，据说在 VC 的下一个主要版本中已修复。