Memory Allocation

The base class GC  is slightly more complex, as it has to provide a few different functionalities. The first service that class GC  must provide is of course memory allocation and deallocation. As a time saving device we can specify what the default collector is using the methods get_default_gc and set_default_gc. Method GCObject::new will use this collector by default, unless placement syntax is used. Method GCObject::delete, on the other hand, can correctly infer the proper collector to use by the address of the object.

The low level methods to allocate and deallocate memory are m_alloc and free respectively. The programmers usually do not have to use these methods directly.

The method to invoke a garbage collection of a specific level is collect(int level). This forces an explicit collection. Method grow_heap(size_t) can also be used to explicitly increase the heap size of a collector. Depending of the actual behavior of the subclasses, these methods may have different effects.

   class GC {
   protected:
      static GC * default_gc;
   public:
      static GC&  get_default_gc()       { return *default_gc; }
      static void set_default_gc(GC& gc) { default_gc = &gc; }
      virtual void * m_alloc   (size_t) = 0;
      virtual void   free      (void *);
      virtual void   collect   (int level = 0) = 0;
      virtual void   grow_heap (size_t) = 0;
      static  void garbage_collect() { default_gc->collect(); }
      virtual void set_gc_ratio(int);
      virtual void set_initial_heap_size (size_t);
      virtual void set_min_heap_growth   (size_t);
   };