c ++ value_type不适用于std :: map中的std :: tr1：tuple [英] c++ value_type not work for std::tr1:tuple in a std::map
问题描述
以下代码段在Visual Studio 2008中使用，但在Visual Studio 2010中不能使用。
The following code snippet work with Visual Studio 2008 but not with Visual Studio 2010.
template <typename TKey>
struct MyStruct
{
typedef std::map<TKey, int> Keys;
MyStruct()
{
}
void set(TKey& key)
{
#if 1
// This works with VS 2008 but not with 2010
keys_.insert(typename Keys::value_type(key, 1));
#else
// This works with VS 2008 and VS 2010
keys_.insert(std::pair<TKey, int>(key, 1));
#endif
};
private:
Keys keys_;
};
使用
typedef std::tr1::tuple<int, int> MyValueType;
MyStruct<MyValueType> a;
MyValueType x;
a.set(x);
我收到以下错误：
1> C：\Program Files \Microsoft Visual Studio 10.0 \VC\include\tuple（127）：
错误C2440：'initializing'：无法从'const MyValueType '
to'int'1>没有用户定义的转换运算符
可以执行此转换，或者操作符不能被调用1>
C：\Program Files \Microsoft Visual Studio 10.0 \VC\include\xxtuple0（9）：
参见函数模板实例化的参考
'std :: tr1 :: _ Cons_node< _Car，_Cdr> :: _ Cons_node< _Ty，std :: tr1 :: _ Nil&，std :: tr1 :: _ Nil&，std :: tr1 :: _Nil&，std :: tr1 :: _Nil&，std :: tr1 :: _Nil&，std :: tr1 :: _Nil&，std :: tr1 :: _ Nil&，std :: tr1 :: _ Nil&，std :: tr1 :: _Nil&>（_ Farg0
&&，_Farg1，_Farg2，_Farg3，_Farg4，_Farg5 ，_Farg6，_Farg7，_Farg8，_Farg9）'
正在编译1> with 1> [1>
_Car = int，1> _Cdr = std :: tr1 :: _ Cons_node :: _ Type> ，
1> _Ty = MyValueType，1> _Farg0 = MyValueType，
1> _Farg1 = std :: tr1 :: _ Nil& 1>
_Farg2 = std :: tr1 :: _ Nil& 1> _Farg3 = std :: tr1 :: _Nil& 1> _Farg4 = std :: tr1 :: _Nil& 1> _Farg5 = std :: tr1 :: _ _Farg6 = std :: tr1 :: _Nil& 1> _Farg7 = std :: tr1 :: _Nil& 1> _Farg8 = std :: tr1 :: _Nil& 1> _Farg9 = std :: tr1 :: _Nil& 1>] 1> C：\Program Files \Microsoft Visual Studio
10.0 \VC\include\utility（145）：参见函数模板实例化'std :: tr1 :: tuple< _Arg0 ，_Arg1> :: tuple>（_ Farg0&&;）1>
with 1> [1> _Arg0 = int，1>
_Arg1 = int，1 > _Farg0 = const std :: tr1 :: tuple 1>] 1> C：\Program Files \Microsoft Visual Studio
10.0 \VC\include\utility（142）：编译类模板成员函数'std :: _ Pair_base< _Ty1，_Ty2> :: _ Pair_base（const
std :: tr1 :: tuple <_Arg0，_Arg1>&&，int& br>
[1> _Ty1 = const MyValueType，1> _Ty2 = int，1>
_Arg0 = int，1> _Arg1 = int 1>] 1> C：\Program Files\Microsoft Visual Studio 10.0 \VC\include\utility（174）
：参考类模板实例化
'std :: _ Pair_base< _Ty1，_Ty2>'1> with 1>
[1> _Ty1 = const MyValueType，1> _Ty2 = int 1>
] 1>
D：\Projekte\demo\Demo.cpp b $ b：参见类模板实例化'std :: pair< _Ty1，_Ty2>'
正在被编译1> with 1> [1>
_Ty1 = const MyValueType，1> _Ty2 = int 1>] 1> D：\Projekte\demo\Demo.cpp（39）
：编译类模板成员函数'void
MyStruct :: set（TKey& 1>与1> [1>
TKey = MyValueType 1>] 1>
D：\Projekte\demo\Demo.cpp（92）
：参见类模板实例化'MyStruct'为
编译1> with 1> [1>
TKey = MyValueType 1>] 1> C：\Program Files \Microsoft Visual
Studio 10.0\VC\include\tuple（127）：error C2439：
'std :: tr1 :: _ Cons_node< _Car，_Cdr> :: _ Value'：member不能是
初始化1>与1> [1> _Car = int，
1>
_Cdr = std :: tr1 :: _ Cons_node :: _ Type>
1>] 1> C ：\Program Files \Microsoft Visual Studio
10.0 \VC\include\tuple（170）：请参见声明std :: tr1 :: _ Cons_node< _Car，_Cdr> :: _ Value'1>与1>
[1> _Car = int，1>
_Cdr = std :: tr1 :: _ Cons_node :: _ Type>
1>]
========== Build：0成功，1失败，0最新，0已跳过==========
1>C:\Program Files\Microsoft Visual Studio 10.0\VC\include\tuple(127): error C2440: 'initializing' : cannot convert from 'const MyValueType' to 'int' 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called 1> C:\Program Files\Microsoft Visual Studio 10.0\VC\include\xxtuple0(9) : see reference to function template instantiation 'std::tr1::_Cons_node<_Car,_Cdr>::_Cons_node<_Ty,std::tr1::_Nil&,std::tr1::_Nil&,std::tr1::_Nil&,std::tr1::_Nil&,std::tr1::_Nil&,std::tr1::_Nil&,std::tr1::_Nil&,std::tr1::_Nil&,std::tr1::_Nil&>(_Farg0 &&,_Farg1,_Farg2,_Farg3,_Farg4,_Farg5,_Farg6,_Farg7,_Farg8,_Farg9)' being compiled 1> with 1> [ 1>
_Car=int, 1> _Cdr=std::tr1::_Cons_node::_Type>, 1> _Ty=MyValueType, 1> _Farg0=MyValueType, 1> _Farg1=std::tr1::_Nil &, 1>
_Farg2=std::tr1::_Nil &, 1> _Farg3=std::tr1::_Nil &, 1> _Farg4=std::tr1::_Nil &, 1> _Farg5=std::tr1::_Nil &, 1> _Farg6=std::tr1::_Nil &, 1> _Farg7=std::tr1::_Nil &, 1> _Farg8=std::tr1::_Nil &, 1> _Farg9=std::tr1::_Nil & 1> ] 1> C:\Program Files\Microsoft Visual Studio 10.0\VC\include\utility(145) : see reference to function template instantiation 'std::tr1::tuple<_Arg0,_Arg1>::tuple>(_Farg0 &&)' being compiled 1>
with 1> [ 1> _Arg0=int, 1>
_Arg1=int, 1> _Farg0=const std::tr1::tuple 1> ] 1> C:\Program Files\Microsoft Visual Studio 10.0\VC\include\utility(142) : while compiling class template member function 'std::_Pair_base<_Ty1,_Ty2>::_Pair_base(const std::tr1::tuple<_Arg0,_Arg1> &&,int &&)' 1> with 1>
[ 1> _Ty1=const MyValueType, 1> _Ty2=int, 1> _Arg0=int, 1> _Arg1=int 1> ] 1> C:\Program Files\Microsoft Visual Studio 10.0\VC\include\utility(174) : see reference to class template instantiation 'std::_Pair_base<_Ty1,_Ty2>' being compiled 1> with 1>
[ 1> _Ty1=const MyValueType, 1> _Ty2=int 1> ] 1>
D:\Projekte\demo\Demo.cpp(40) : see reference to class template instantiation 'std::pair<_Ty1,_Ty2>' being compiled 1> with 1> [ 1>
_Ty1=const MyValueType, 1> _Ty2=int 1> ] 1> D:\Projekte\demo\Demo.cpp(39) : while compiling class template member function 'void MyStruct::set(TKey &)' 1> with 1> [ 1>
TKey=MyValueType 1> ] 1>
D:\Projekte\demo\Demo.cpp(92) : see reference to class template instantiation 'MyStruct' being compiled 1> with 1> [ 1>
TKey=MyValueType 1> ] 1>C:\Program Files\Microsoft Visual Studio 10.0\VC\include\tuple(127): error C2439: 'std::tr1::_Cons_node<_Car,_Cdr>::_Value' : member could not be initialized 1> with 1> [ 1> _Car=int, 1>
_Cdr=std::tr1::_Cons_node::_Type> 1> ] 1> C:\Program Files\Microsoft Visual Studio 10.0\VC\include\tuple(170) : see declaration of 'std::tr1::_Cons_node<_Car,_Cdr>::_Value' 1> with 1>
[ 1> _Car=int, 1>
_Cdr=std::tr1::_Cons_node::_Type> 1> ] ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
如果替换typedef std :: tr1 :: tuple MyValueType with typedef int MyValueType it works。
If a replace typedef std::tr1::tuple MyValueType with typedef int MyValueType it works.
提前感谢。 / p>
Thank you in advance.
推荐答案
我认为这是一个错误，与MSVC 2010中移动语义的错误实现，因为你可以成功地编译这个代码： / p>
I think this is an error that related to bad implementation of move semantic in MSVC 2010 since you can successfully compile this code:
typename Keys::value_type v( key, 1 );
keys_.insert(v);
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