Shipped: Dynace OO extension to C

Dynace is a portable, open-source extension to the C language that adds the following capabilities to standard C:
full object-oriented capabilities including
classes, instances, methods, & generic functions
encapsulation
polymorphism
inheritance (multiple)
fully meta-class based (like Smalltalk)
dynamic binding and dispatching through generic functions (like CLOS)
garbage collection
threads (supports cooperative and native threads)
full class library