prefinalizer.h File Reference

#include "cppgc/internal/compiler-specific.h"
#include "cppgc/liveness-broker.h"

Include dependency graph for prefinalizer.h:

Go to the source code of this file.

Classes
class	cppgc::internal::PrefinalizerRegistration

Namespaces
namespace	cppgc
namespace	cppgc::internal

Macros
#define	CPPGC_USING_PRE_FINALIZER(Class, PreFinalizer)

Macro Definition Documentation

CPPGC_USING_PRE_FINALIZER

#define CPPGC_USING_PRE_FINALIZER	(		Class,
			PreFinalizer
	)

Value:

 public:                                                                       \
  static bool InvokePreFinalizer(const cppgc::LivenessBroker& liveness_broker, \
                                 void* object) {                               \
    static_assert(cppgc::IsGarbageCollectedOrMixinTypeV<Class>,                \
                  "Only garbage collected objects can have prefinalizers");    \
    Class* self = static_cast<Class*>(object);                                 \
    if (liveness_broker.IsHeapObjectAlive(self)) return false;                 \
    self->PreFinalizer();                                                      \
    return true;                                                               \
  }                                                                            \
                                                                               \
 private:                                                                      \
  CPPGC_NO_UNIQUE_ADDRESS cppgc::internal::PrefinalizerRegistration            \
      prefinalizer_dummy_{this, Class::InvokePreFinalizer};                    \
  static_assert(true, "Force semicolon.")

Macro must be used in the private section of Class and registers a prefinalization callback void Class::PreFinalizer(). The callback is invoked on garbage collection after the collector has found an object to be dead.

Callback properties:

• The callback is invoked before a possible destructor for the corresponding object.
• The callback may access the whole object graph, irrespective of whether objects are considered dead or alive.
• The callback is invoked on the same thread as the object was created on.

Example:

class WithPrefinalizer : public GarbageCollected<WithPrefinalizer> {
  CPPGC_USING_PRE_FINALIZER(WithPrefinalizer, Dispose);
 
 public:
  void Trace(Visitor*) const {}
  void Dispose() { prefinalizer_called = true; }
  ~WithPrefinalizer() {
    // prefinalizer_called == true
  }
 private:
  bool prefinalizer_called = false;
};