Código:Error de Visual C++ 10.0 en std :: reference_wrapper?
#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);
}
resultado con MinGW g ++ 4.6.1:
[d:\dev\test] >g++ foo.cpp -std=c++0x [d:\dev\test] > _
Resultado con Visual C++ 10.0:
[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] > _
me gusta la forma en que el Visual El compilador de C++ le dice al usuario 11 veces que la clase abstracta no puede ser instanciada, solo para martillar e punto de inicio, como, en caso de que el usuario no lo supiera. ¿Pero debería std::reference_wrapper
realmente instanciar la clase? No es gran cosa el punto de (pasar) referencia a no requiere instanciación?
Es decir, ¿es esto, como sospecho firmemente, un error en la implementación de la biblioteca estándar de Visual C++?
Envié un [informe de error] (https://connect.microsoft.com/VisualStudio/feedback/details/727368/std-reference-wrapper-fails-to-wrap-reference-to-object-of-abstract -clase) a Microsoft. –
¿No debería estar creando la referencia_capería con la función ref helper? –
@jamesj: no. eso es solo una función auxiliar, para evitar especificar el tipo explícitamente. para investigar un error, es mejor tener cosas explícitas que implícitas. –