How to calculate a fibonacci number not in runtime but in compiler time?

See more:

C++

time

compiler

I am to prog some code on C++ which should calculate a fibonacci number in compiler time.
So it should look like this:

int main()
{
  int v=???6???;
}

The six is the number of the fibonacci number 8.
And the question marks are some symbols which should be added to calculate the fibonacci number (in this case 6) in compiler time. So I need to see in object file already an answer (that 8 is written in variable v) (as the compiler alreay worked)
So we should see the instruction in object file, where 8 is put in v

What I have tried:

int main()
{
  int v=???6???;
}

I
I really have no ideas, could you please help?