You may receive an "error C2593: 'operator <<' is ambiguous" error message when you try to pass an __int64 variable to the ostream operator << (168440)

The information in this article applies to:

The Standard C++ Library, when used with:
- Microsoft Visual C++, 32-bit Enterprise Edition 5.0
- Microsoft Visual C++, 32-bit Enterprise Edition 6.0
- Microsoft Visual C++, 32-bit Professional Edition 5.0
- Microsoft Visual C++, 32-bit Professional Edition 6.0
- Microsoft Visual C++, 32-bit Learning Edition 6.0

This article was previously published under Q168440

SYMPTOMS

If you try to pass an __int64 variable to the ostream operator <<, you get the following error:

error C2593: 'operator <<' is ambiguous

CAUSE

There is no operator << for __int64 type defined for the ostream class.

RESOLUTION

Define your own version of operator <<. The following sample code section shows a simple solution for << operator that converts the __int64 variable to a char * type and passes it to the ostream << operator.

STATUS

Microsoft has confirmed that this is a bug in the Microsoft products that are listed in the "Applies to" section.

This problem was corrected in Microsoft Visual C++ .NET.

MORE INFORMATION

The following sample program demonstrates the problem and workaround:

//Sample.cpp
// Compiler Options : /GX

//#define WORKAROUND   //Uncomment this line to workaround

#include<iostream>
using namespace std;

#ifdef WORKAROUND
std::ostream& operator<<(std::ostream& os, __int64 i )
{
    char buf[20];
    sprintf(buf,"%I64d", i );
    os << buf;
    return os;
}

#endif

int main(){
__int64  i64;

cout << i64 ;

return 0;
}

Modification Type:	Major	Last Reviewed:	5/26/2005
Keywords:	kbBug kbCRT kberrmsg kbfix kbNoUpdate KB168440 kbAudDeveloper