The Programmatic Interface

The programmatic interface to the garbage collector involves two base classes, GC  and GCObject . The base class GC  provides an uniform interface to all types of collectors and memory managers while class GCObject provides the interface to all collectable classes. Table 1 contains a listing of the classes in our hierarchy.

 

Class	Purpose
GCObject	Collectable object base class
GC	Garbage collector base class
CGC	Conservative garbage collector base class
BGC	Bartlett style mostly copying collector
MarkSweepGC	A mark-sweep collector
UserHeap	A heap for pointerless object
GCVerifier	A heap walker that verifies the integrity of a structure

Table 1:   Garbage Collection Classes.

Class GCObject  is extremely simple: it redefines the operators new and delete to allocate memory from the default collector, and declares a virtual method ``trace'' to be defined by subclasses (more on this later.)

Memory for a GCObject  is allocated and freed using the usually new and delete operators. Of course, freeing memory explicitly using delete is optional for many subclasses of GC .

   class GCObject {
   public:
      inline void * operator new(size_t n, GC& gc = *GC::default_gc)
         { return gc.m_alloc(n); }
      inline void * operator new(size_t n, size_t N, GC& gc = *GC::default_gc)
         { return gc.m_alloc(n > N ? n : N); }
      inline void   operator delete(void *);
      virtual void trace(GC *) = 0;
   };