UML is not there to be strictly adhered to it. You should pick out the bits and pieces that you need and apply those in a sensible way.
The most important thing is that you make it clear to people what you're doing. Each of the function prototypes you looked at there clarify what the function expects as argument structure (the first one being a bit more clear in 'perl terms').
Keep in mind that methodologies are there to help you in design and documentation. You won't get frowned upon when bending the rules a bit to fit your own project. Clarity before all !!