A Generational, Compacting Garbage Collector for C++

One of the most striking differences between any Lisp dialect and C++ is not the obvious syntax differences, but rather their opposing views on management of objects with indefinite extent. While Lisp systems automatically recover storage used by objects that are no longer needed by the program, C++ requires that the user explicitly delete the object in order to reclaim storage. Automatically maintaining reference counts by operator overloading is one method that has been suggested for hiding storage management operations inside a class. An alternative is to use a garbage collector. Using the "mostly-copying" garbage collection algorithm described in this paper, a garbage collector has been constructed for C++. Its use requires no modifications to the C++ compiler or runtime environment. In addition, it is far simpler to define a garbage collected class than to define methods to reference count the class. Experience to date shows that the performance of this garbage collector is better than other methods of automatic storage management and comparable to explicit allocation and deletion.