CE's Blog

Just working with the new Visual Studio 2010, integrating Win32 console based code into a window app. The old code used fprintf(…) for debug output.
Since stdout/stderr is not available in a windows app, the fprintf based debug output had to be changed to print to the visual studio output window.

This can be accomplished via the universal OutputDebugString() API. The only shortcoming is, that it does not support variable arguments in a sprintf(…) form.

Here is a workaround:

#include <strsafe.h>
// ...
void MyOutputDebugString( LPCTSTR sFormat, ... )
{
    va_list argptr;      
    va_start( argptr, sFormat ); 
    TCHAR buffer[ 2000 ];
    HRESULT hr = StringCbVPrintf( buffer, sizeof( buffer ), sFormat, argptr );
    if ( STRSAFE_E_INSUFFICIENT_BUFFER == hr || S_OK == hr )
        OutputDebugString( buffer );
    else
        OutputDebugString( _T("StringCbVPrintf error.") );
}

I am using strsafe.h in this case to offer protection against buffer overruns. In case the internal buffer is not big enough to handle the output string, it will be safely truncated with an ending \0. In case you cannot make use of strsafe.h, here is an old style solution:

void MyOutputDebugString( LPCTSTR sFormat, ... )
{
    va_list argptr;      
    va_start( argptr, sFormat ); 
    TCHAR buffer[ 2000 ];
    wvsprintf( buffer, sizeof( buffer ), sFormat, argptr );
    buffer[ ( sizeof( buffer ) / sizeof( *buffer ) ) - 1 ] = '\0';
    OutputDebugString( buffer );
}