BUG: Stream Operator << Cannot Handle __int64 Type

• The Standard C++ Library, used with:
  • Microsoft Visual C++, 32-bit Editions, versions 5.0, 6.0

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 this to be a bug in the Microsoft products listed at the beginning of this article.

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;
} 

Additional query words:

Keywords          : kberrmsg kbCRT kbVC kbVC500bug kbVC600bug 
Version           : winnt:5.0,6.0
Platform          : winnt 
Issue type        : kbbug 

Last Reviewed: May 17, 1999