दृश्य सी ++ 10.0 बग std :: context_wrapper में?

Question

कोड: MinGW जी के साथ ++ 4.6.1

#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); 
} 

परिणाम:

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

[d:\dev\test] 
> _ 

विजुअल C++ 10.0 के साथ परिणाम:

 
[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] 
> _ 

मैं तरीका है कि दृश्य की तरह सी ++ कंपाइलर उपयोगकर्ता को 11 बार बताता है कि अमूर्त वर्ग को तत्काल नहीं किया जा सकता है, केवल वें हथियाने के लिए ई बिंदु घर, जैसे, अगर उपयोगकर्ता को इसके बारे में पता नहीं था। लेकिन std::reference_wrapper वास्तव में वर्ग को तुरंत चालू करना चाहिए? पर तत्कालता की आवश्यकता नहीं है (पास से) संदर्भ का अधिकांश बिंदु नहीं है?

आईई, क्या यह दृढ़ता से संदेह है, दृश्य सी ++ मानक पुस्तकालय कार्यान्वयन में एक बग?

Answer 1

प्रश्न लेखक द्वारा हल किया गया। यह वीसी के अगले प्रमुख संस्करण में अनुमानित दृश्य सी ++ 10.0 में bug है।