Question

这在GCC 3和4中编译得很好.MSVC ++无法弄清楚noFunction的类型并引发一些可怕的错误。注意如果你将noFunction强制转换为BFunction，它在VS2010中工作得很好。

我的问题：这是VS2010中的缺陷，还是GCC违反规则？

#include <map>

using namespace std;

typedef bool (*AFunction)(int arg1, int arg2);
typedef bool (*BFunction)(long arg1, bool arg2);

bool noFunction(long, bool) { return true; }

void test(AFunction a)
{

    make_pair(a, noFunction); //fails in VS2010

}

N.B。将noFunction转换为BFunction修复了VS2010中的问题。

make_pair(a, (BFunction)noFunction);  //works everywhere

以下是参考错误：

    1>  makepairtest.cpp
1>c:\program files (x86)\microsoft visual studio 10.0\vc\include\type_traits(197): error C2752: 'std::tr1::_Remove_reference<_Ty>' : more than one partial specialization matches the template argument list
1>          with
1>          [
1>              _Ty=bool (__cdecl &)(long,bool)
1>          ]
1>          c:\program files (x86)\microsoft visual studio 10.0\vc\include\xtr1common(356): could be 'std::tr1::_Remove_reference<_Ty&&>'
1>          c:\program files (x86)\microsoft visual studio 10.0\vc\include\xtr1common(350): or       'std::tr1::_Remove_reference<_Ty&>'
1>          c:\program files (x86)\microsoft visual studio 10.0\vc\include\type_traits(962) : see reference to class template instantiation 'std::tr1::remove_reference<_Ty>' being compiled
1>          with
1>          [
1>              _Ty=bool (__cdecl &)(long,bool)
1>          ]
1>          c:\program files (x86)\microsoft visual studio 10.0\vc\include\utility(26) : see reference to class template instantiation 'std::tr1::decay<_Ty>' being compiled
1>          with
1>          [
1>              _Ty=bool (__cdecl &)(long,bool)
1>          ]
1>          c:\xxx\makepairtest.cpp(14) : see reference to class template instantiation 'std::tr1::_Unrefwrap<_Type>' being compiled
1>          with
1>          [
1>              _Type=bool (__cdecl &)(long,bool)
1>          ]
1>c:\program files (x86)\microsoft visual studio 10.0\vc\include\type_traits(965): error C2528: 'abstract declarator' : pointer to reference is illegal
1>c:\program files (x86)\microsoft visual studio 10.0\vc\include\type_traits(349): error C2528: 'type' : pointer to reference is illegal
1>          c:\program files (x86)\microsoft visual studio 10.0\vc\include\type_traits(967) : see reference to class template instantiation 'std::tr1::add_pointer<_Ty>' being compiled
1>          with
1>          [
1>              _Ty=bool (__cdecl &)(long,bool)
1>          ]
1>c:\program files (x86)\microsoft visual studio 10.0\vc\include\utility(148): error C2535: 'std::_Pair_base<_Ty1,_Ty2>::_Pair_base(const _Ty1 &,const _Ty2)' : member function already defined or declared
1>          with
1>          [
1>              _Ty1=bool (__cdecl *)(int,int),
1>              _Ty2=bool (__cdecl &)(long,bool)
1>          ]
1>          c:\program files (x86)\microsoft visual studio 10.0\vc\include\utility(134) : see declaration of 'std::_Pair_base<_Ty1,_Ty2>::_Pair_base'
1>          with
1>          [
1>              _Ty1=bool (__cdecl *)(int,int),
1>              _Ty2=bool (__cdecl &)(long,bool)
1>          ]
1>          c:\program files (x86)\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=bool (__cdecl *)(int,int),
1>              _Ty2=bool (__cdecl &)(long,bool)
1>          ]
1>          c:\xxx\makepairtest.cpp(14) : see reference to class template instantiation 'std::pair<_Ty1,_Ty2>' being compiled
1>          with
1>          [
1>              _Ty1=bool (__cdecl *)(int,int),
1>              _Ty2=bool (__cdecl &)(long,bool)
1>          ]

Answer 1

将noFunction的地址与VC10和gcc 4.5.2一起使用，即：

make_pair(a, &noFunction);

根据您发布的错误消息，我猜它与VC如何处理与rvalues的绑定有关。

Answer 2

“我的问题：这是VS2010中的缺陷，还是GCC弯曲规则？”

当怀疑责怪Visual C ++和/或比尔盖茨。请注意，在代码中使用noFunction的值与BFunction定义的类型之间存在差异。 noFunction将是函数的引用，而BFunction将指针定义为函数。这有点难以解释，但可能有助于考虑以下计划。

#include <iostream>
#include <typeinfo>


bool noFunction(long, bool) { return true; }

typedef bool (function_ref)(long, bool);
typedef bool (*function_ptr)(long, bool);

int
main()
{
    std::cout << typeid(noFunction).name() << '\n';
    std::cout << typeid(&noFunction).name() << '\n';
    std::cout << typeid(function_ref).name() << '\n';
    std::cout << typeid(function_ptr).name() << '\n';

    return 0;
}

似乎Visual C ++在函数引用上窒息。我不确定是否有合理的理由拒绝它，但我希望你能够构建一个具有可复制构造模型的类型。例如，您应该能够构建但不能分配std::pair<int, int const&>。

这种std :: make_pair的使用在GCC 3和4中运行良好。它在Visual Studio C ++ 2010中失败。为什么？

2 个答案: