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

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 WORKAROUNDstd::ostream& operator<<(std::ostream& os, __int64 i ){    char buf[20];    sprintf(buf,"%I64d", i );    os << buf;    return os;}#endifint main(){__int64  i64;cout << i64 ;return 0;}				
Properties

Article ID: 168440 - Last Review: 06/22/2014 18:21:00 - Revision: 5.0

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