[Richard van der Hoff <richardv@xxxxxxxxxxxxx>]

Luis EG Ontanon wrote:
> putting some printfs is possible (there are some issues on why you
> might want to avoid it during protocol registration) but the Access
> Violation is probably due to a NULL or ivalid pointer passed to
> printf.

[Dissector bug...] implies a wireshark-internal exception, does it not? 
(As opposed to a segfault.)

Most likely thing is that it's not the printf at all, but a tvb_* 
function you are also calling, with bad arguments.