Arguably, a better place would be in the comment (especially if you use say Doxygen).
A comment would actually tell you what it did, and what to expect.
Being "compiled", they're subject to all sorts of namespace issues. Being awfully generic names, you could have problems if you have to integrate with some other package which really uses those symbols for something completely different.
* Pop - removes an element from the near end of the queue
* [in] Queue - the queue
* [out] Node - the result
STATUS Pop(INPUT QUEUE* Queue, OUTPUT NODE* Node);
Of the people who use this technique, there's no standard naming convention which might prove useful.