Question

我遇到了在调试模式下编译一些使用std :: lower_bound（）函数和比较运算符的代码的麻烦。

我已在以下附加的小代码段中隔离了错误：

#include <vector>
#include <string>
#include <algorithm>

using namespace std;

struct SPippo
{
  SPippo(string rsName, int rnValue);

  static const bool compareId(const SPippo& lhs, const int& rId){return lhs.iValue < rId;}

  string sName;
  int iValue;
};


SPippo::SPippo(string rsName, int riValue):
  sName(rsName)
,iValue(riValue)
{ 
}

struct sOrd
{
  const bool operator() (const SPippo& lhs, const int& rId) const {return SPippo::compareId(lhs, rId);}
  const bool operator() (const int& rId, const SPippo& lhs) const {return SPippo::compareId(lhs, rId);}
};

int main()
{

  vector<SPippo> vecPippo;
  vecPippo.push_back(SPippo("Minnie", 1));
  vecPippo.push_back(SPippo("Paperino", 2));
  vecPippo.push_back(SPippo("Pippo", 3));
  vecPippo.push_back(SPippo("Topolino", 4));

  vector<SPippo>::const_iterator cItLowerBound = std::lower_bound(vecPippo.begin(), vecPippo.end(), 2, sOrd());

  return 0;
}

我正在使用VS2008进行编译：使用发布配置时一切正常。相反，在调试模式下，我收到以下错误：

1>c:\program files (x86)\microsoft visual studio 9.0\vc\include\xutility(346) : error C2664: 'const bool sOrd::operator ()(const int &,const SPippo &) const' : cannot convert parameter 1 from 'SPippo' to 'const int &'
1>        Reason: cannot convert from 'SPippo' to 'const int'
1>        No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
1>        c:\program files (x86)\microsoft visual studio 9.0\vc\include\xutility(1699) : see reference to function template instantiation 'bool std::_Debug_lt_pred<_Pr,SPippo,SPippo>(_Pr,_Ty1 &,_Ty2 &,const wchar_t *,unsigned int)' being compiled
1>        with
1>        [
1>            _Pr=sOrd,
1>            _Ty1=SPippo,
1>            _Ty2=SPippo
1>        ]
1>        c:\program files (x86)\microsoft visual studio 9.0\vc\include\xutility(1709) : see reference to function template instantiation 'void std::_Debug_order_single2<_InIt,_Pr>(_FwdIt,_FwdIt,_Pr,bool,const wchar_t *,unsigned int,std::forward_iterator_tag)' being compiled
1>        with
1>        [
1>            _InIt=std::_Vector_iterator<SPippo,std::allocator<SPippo>>,
1>            _Pr=sOrd,
1>            _FwdIt=std::_Vector_iterator<SPippo,std::allocator<SPippo>>
1>        ]
1>        c:\program files (x86)\microsoft visual studio 9.0\vc\include\algorithm(2290) : see reference to function template instantiation 'void std::_Debug_order_single<_FwdIt,_Pr>(_InIt,_InIt,_Pr,bool,const wchar_t *,unsigned int)' being compiled
1>        with
1>        [
1>            _FwdIt=std::_Vector_iterator<SPippo,std::allocator<SPippo>>,
1>            _Pr=sOrd,
1>            _InIt=std::_Vector_iterator<SPippo,std::allocator<SPippo>>
1>        ]
1>        c:\program files (x86)\microsoft visual studio 9.0\vc\include\algorithm(2314) : see reference to function template instantiation '_FwdIt std::_Lower_bound<std::_Vector_iterator<_Ty,_Alloc>,int,__w64 int,_Pr>(_FwdIt,_FwdIt,const int &,_Pr,_Diff *)' being compiled
1>        with
1>        [
1>            _FwdIt=std::_Vector_iterator<SPippo,std::allocator<SPippo>>,
1>            _Ty=SPippo,
1>            _Alloc=std::allocator<SPippo>,
1>            _Pr=sOrd,
1>            _Diff=__w64 int
1>        ]
1>        c:\users\cgab\documents\visual studio 2008\projects\sweettest\sweettest\main.cpp(42) : see reference to function template instantiation '_FwdIt std::lower_bound<std::_Vector_iterator<_Ty,_Alloc>,int,sOrd>(_FwdIt,_FwdIt,const int &,_Pr)' being compiled
1>        with
1>        [
1>            _FwdIt=std::_Vector_iterator<SPippo,std::allocator<SPippo>>,
1>            _Ty=SPippo,
1>            _Alloc=std::allocator<SPippo>,
1>            _Pr=sOrd
1>        ]
1>c:\program files (x86)\microsoft visual studio 9.0\vc\include\xutility(348) : error C2664: 'const bool sOrd::operator ()(const int &,const  SPippo &) const' : cannot convert parameter 1 from 'SPippo' to 'const int &'
1>        Reason: cannot convert from 'SPippo' to 'const int'
1>        No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
1>Build log was saved at "file://c:\Users\cgab\Documents\Visual Studio 2008\Projects\SweetTest\SweetTest\Debug\BuildLog.htm"
1>SweetTest - 2 error(s), 0 warning(s)

使用VS2015或更高版本时，代码在调试模式下编译也很好。鉴于我被迫使用VS2008作为我的项目，你认为有没有办法解决这个问题而不放弃使用lower_bound（）？

提前感谢您的协助！

我认为问题在于VS2008在xutility中使用的代码。实际上，错误指向以下摘录：

template<class _Pr, class _Ty1, class _Ty2> inline
bool __CLRCALL_OR_CDECL _Debug_lt_pred(_Pr _Pred, const _Ty1& _Left,     const _Ty2& _Right,
const wchar_t *_Where, unsigned int _Line)
{   // test if _Pred(_Left, _Right) and _Pred is strict weak ordering
if (!_Pred(_Left, _Right))
    return (false);
else if (_Pred(_Right, _Left))
    _DEBUG_ERROR2("invalid operator<", _Where, _Line);
return (true);

因此，测试了一个 Pred 函数，反转了参数的顺序。但是，如果谓词接受相同类型的参数，则此方法有效，否则不行！

由于_ITERATOR_DEBUG_LEVEL的默认设置，在 C：\ Program Files（x86）\ Microsoft Visual Studio 10.0 \ VC \ include \ yvals.h <中定义，因此VS2010中源代码xutility的这一特定部分未执行。 / em>的。这可能解释了为什么代码在VS2008以外的其他版本的VS中编译。

Answer 1

如果其他人偶然发现这种情况，解决此问题的“黑客”是禁用相应编译单元的迭代器调试。如果放在#include指令之前，下面的代码会剪切：

#if defined(_MSC_VER) && defined(_DEBUG) && _MSC_VER <= 1500
#define _HAS_ITERATOR_DEBUGGING 0
#endif

lower_bound（）函数无法在调试模式下编译

1 个答案: