Article: Q168078
Product(s): Microsoft C Compiler
Version(s): winnt:5.0
Operating System(s):
Keyword(s): kbtool kbVC500bug kbVC600fixkbbuglist
Last Modified: 07-MAY-2001
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The information in this article applies to:
- Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0
- Microsoft Visual C++, 32-bit Professional Edition, version 5.0
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SYMPTOMS
========
When you attempt to instantiate an STL component for a class, a C2784 error
occurs, complaining that a relational operator (such as operator!= or
operator>) is not defined. This in spite of including "using namespace
std::rel_ops;", and defining operator< and operator== for the class.
CAUSE
=====
The problem is caused by the nested namespace std::rel_ops. The compiler is
unable to do a proper name lookup for the generic relational operators '!=',
'<=', '>', '>=', which are defined in the namespace std::rel_ops and
are referenced by several STL components.
RESOLUTION
==========
The easiest workaround is to add a using declaration for the specific operator
the compiler is complaining about. See the sections compiled conditionally upon
WORKAROUND in the sample code below.
STATUS
======
Microsoft has confirmed this to be a problem in the Microsoft products that are
listed at the beginning of this article.This problem was corrected in Microsoft
Visual C++ version 6.0.
MORE INFORMATION
================
The following sample demonstrates the problem.
Sample Code
-----------
/*
Compile options: /GX
*/
#include <list>
using namespace std ;
using namespace std::rel_ops ;
#ifdef WORKAROUND // define WORKAROUND to get around the error
using std::rel_ops::operator!=;
using std::rel_ops::operator>;
#endif
class X {
int N;
public:
X(int n) : N(n) {}
bool operator==(const X& b) const
{ return N == b.N; }
bool operator<(const X& b) const
{ return N < b.N; }
};
list <X> xList;
int main()
{
return 0;
}
Additional query words:
======================================================================
Keywords : kbtool kbVC500bug kbVC600fix kbbuglist
Technology : kbVCsearch kbAudDeveloper kbVC500 kbVC32bitSearch kbVC500Search
Version : winnt:5.0
Issue type : kbbug
Solution Type : kbfix
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