Question

I was asked in an interview that what is the usage of virtual keyword with a class declaration in C++ and I answered that virtual keyword cannot be used with a class declaration in C++. The interviewer said that it is possible and asked me to test it later.

Now that I have checked it myself I have come to know that this is possible and this is not a compiler error. In fact, when I do something like this with a Visual C++ compiler:

virtual class Test
{
   int i;
};

I get a compiler warning “warning C4091: ‘virtual ‘ : ignored on left of ‘Test’ when no variable is declared”. I haven’t been able to find out yet that what this warning means and further what is the usage of virtual keyword. If there is no helpful usage, then why is this allowed in the first place and why is this not a compiler error.

Answer 1

That’s a bug in VC++. Comeau and gcc both reject the code.