Question

What is wrong in this code and how to fix it?

int _tmain(int argc, _TCHAR* argv[])
{
std::ostream * o = &std::cout;
char text[4096];
char *file = "D://test.txt";

if ( file != NULL ) 
{
  strcpy ( text, file );
  strcat ( text, ".log" );
  o = & std::ofstream ( text );
}
*o << "test"; //Exception
return 0;
}

Answer 1

o = & std::ofstream ( text ); this creates a temporary ofstream object whose address is assigned to o but the object is instantly destroyed, so o points to a deleted object. This should work (using static):

int _tmain(int argc, _TCHAR* argv[])
{
    std::ostream * o = &std::cout;
    char text[4096];
    char *file = "D://test.txt";

    if ( file != NULL ) 
    {
        strcpy ( text, file );
        strcat ( text, ".log" );
        static std::ofstream myofstream( text );
        o = &myofstream;
    }
    *o << "test"; //Exception
    return 0;
}