A memory leak is unnecessary memory consumption by a computer program. The most common manifestion is the failure to release unused memory that has been allocated. A memory leak occurs when the program either loses the ability to free the memory or simply neglects to free memory it no longer needs. (source: Wikipedia, The Free Encyclopedia.)
Doxygen 1.5.7, released Sep 28, 2008, implements a new useful feature of particular interest for people doing object-oriented programming in C or other languages that don't have native representation of such concept.
Object-oriented programming in C is not uncommon. It is usually done by promoting struct constructs to classes, and specific functions to methods. There are many different (but similar) ways to achieve this. Google provides plenty of links about object-oriented programming in C.