Hi Paul
As far as I know, cf_open can still fail after calling the init-functions. In that case you would get the filename, but the capture is already closed.
My question is, why do you need the filename in the first place?
Also, you could set the filename at a later point. If you implement a tap-interface, you could set the filename in the first tap-print callback. Makes sense, 'cause you normally only have data at this point anyway.
You can raise this as an improvement (do not think it is a bug) if you want to, not really sure though, if it should be changed
cheers