A Modern Objective-C Runtime

In light of the recent modifications to the de facto standard implementation ObjectiveC language by Apple Inc., the GNU Objective-C runtime lacks a number of features that are desirable for a modern implementation. This paper presents a metaobject protocol flexible enough to implement Objective-C and other languages of interest. It also presents an implementation of this model in the form of a new Objective-C runtime library which supports all of the new features of Objective-C 2.0 as well as safe inline caching, mixins, prototype-based object orientation, transparent support for other languages—including those with a prototype-based object model—and a small, maintainable code base.