vtkGarbageCollector Class Reference

Detect and break reference loops. More...

#include <vtkGarbageCollector.h>

Inheritance diagram for vtkGarbageCollector:

Collaboration diagram for vtkGarbageCollector:

Public Types
typedef vtkObject	Superclass

Public Member Functions
virtual vtkTypeBool	IsA (const char *type)
	Return 1 if this class is the same type of (or a subclass of) the named class.
vtkGarbageCollector *	NewInstance () const
void	PrintSelf (ostream &os, vtkIndent indent) override
	Methods invoked by print to print information about the object including superclasses.
Public Member Functions inherited from vtkObject
	vtkBaseTypeMacro (vtkObject, vtkObjectBase)
virtual void	DebugOn ()
	Turn debugging output on.
virtual void	DebugOff ()
	Turn debugging output off.
bool	GetDebug ()
	Get the value of the debug flag.
void	SetDebug (bool debugFlag)
	Set the value of the debug flag.
virtual void	Modified ()
	Update the modification time for this object.
virtual vtkMTimeType	GetMTime ()
	Return this object's modified time.
void	PrintSelf (ostream &os, vtkIndent indent) override
	Methods invoked by print to print information about the object including superclasses.
void	RemoveObserver (unsigned long tag)
void	RemoveObservers (unsigned long event)
void	RemoveObservers (const char *event)
void	RemoveAllObservers ()
vtkTypeBool	HasObserver (unsigned long event)
vtkTypeBool	HasObserver (const char *event)
vtkTypeBool	InvokeEvent (unsigned long event)
vtkTypeBool	InvokeEvent (const char *event)
std::string	GetObjectDescription () const override
	The object description printed in messages and PrintSelf output.
unsigned long	AddObserver (unsigned long event, vtkCommand *, float priority=0.0f)
	Allow people to add/remove/invoke observers (callbacks) to any VTK object.
unsigned long	AddObserver (const char *event, vtkCommand *, float priority=0.0f)
	Allow people to add/remove/invoke observers (callbacks) to any VTK object.
vtkCommand *	GetCommand (unsigned long tag)
	Allow people to add/remove/invoke observers (callbacks) to any VTK object.
void	RemoveObserver (vtkCommand *)
	Allow people to add/remove/invoke observers (callbacks) to any VTK object.
void	RemoveObservers (unsigned long event, vtkCommand *)
	Allow people to add/remove/invoke observers (callbacks) to any VTK object.
void	RemoveObservers (const char *event, vtkCommand *)
	Allow people to add/remove/invoke observers (callbacks) to any VTK object.
vtkTypeBool	HasObserver (unsigned long event, vtkCommand *)
	Allow people to add/remove/invoke observers (callbacks) to any VTK object.
vtkTypeBool	HasObserver (const char *event, vtkCommand *)
	Allow people to add/remove/invoke observers (callbacks) to any VTK object.
template<class U , class T >
unsigned long	AddObserver (unsigned long event, U observer, void(T::*callback)(), float priority=0.0f)
	Overloads to AddObserver that allow developers to add class member functions as callbacks for events.
template<class U , class T >
unsigned long	AddObserver (unsigned long event, U observer, void(T::*callback)(vtkObject *, unsigned long, void *), float priority=0.0f)
	Overloads to AddObserver that allow developers to add class member functions as callbacks for events.
template<class U , class T >
unsigned long	AddObserver (unsigned long event, U observer, bool(T::*callback)(vtkObject *, unsigned long, void *), float priority=0.0f)
	Allow user to set the AbortFlagOn() with the return value of the callback method.
vtkTypeBool	InvokeEvent (unsigned long event, void *callData)
	This method invokes an event and return whether the event was aborted or not.
vtkTypeBool	InvokeEvent (const char *event, void *callData)
	This method invokes an event and return whether the event was aborted or not.
virtual void	SetObjectName (const std::string &objectName)
	Set/get the name of this object for reporting purposes.
virtual std::string	GetObjectName () const
	Set/get the name of this object for reporting purposes.
Public Member Functions inherited from vtkObjectBase
const char *	GetClassName () const
	Return the class name as a string.
virtual std::string	GetObjectDescription () const
	The object description printed in messages and PrintSelf output.
virtual vtkTypeBool	IsA (const char *name)
	Return 1 if this class is the same type of (or a subclass of) the named class.
virtual vtkIdType	GetNumberOfGenerationsFromBase (const char *name)
	Given the name of a base class of this class type, return the distance of inheritance between this class type and the named class (how many generations of inheritance are there between this class and the named class).
virtual void	Delete ()
	Delete a VTK object.
virtual void	FastDelete ()
	Delete a reference to this object.
void	InitializeObjectBase ()
void	Print (ostream &os)
	Print an object to an ostream.
void	Register (vtkObjectBase *o)
	Increase the reference count (mark as used by another object).
virtual void	UnRegister (vtkObjectBase *o)
	Decrease the reference count (release by another object).
int	GetReferenceCount ()
	Return the current reference count of this object.
void	SetReferenceCount (int)
	Sets the reference count.
bool	GetIsInMemkind () const
	A local state flag that remembers whether this object lives in the normal or extended memory space.
virtual void	PrintHeader (ostream &os, vtkIndent indent)
	Methods invoked by print to print information about the object including superclasses.
virtual void	PrintTrailer (ostream &os, vtkIndent indent)
	Methods invoked by print to print information about the object including superclasses.
virtual bool	UsesGarbageCollector () const
	Indicate whether the class uses vtkGarbageCollector or not.

Static Public Member Functions
static vtkTypeBool	IsTypeOf (const char *type)
static vtkGarbageCollector *	SafeDownCast (vtkObjectBase *o)
static vtkGarbageCollector *	New ()
static void	Collect ()
	Collect immediately using any objects whose collection was previously deferred as a root for the reference graph walk.
static void	Collect (vtkObjectBase *root)
	Collect immediately using the given object as the root for a reference graph walk.
static void	DeferredCollectionPush ()
	Push/Pop whether to do deferred collection.
static void	DeferredCollectionPop ()
	Push/Pop whether to do deferred collection.
static void	SetGlobalDebugFlag (bool flag)
	Set/Get global garbage collection debugging flag.
static bool	GetGlobalDebugFlag ()
	Set/Get global garbage collection debugging flag.
Static Public Member Functions inherited from vtkObject
static vtkObject *	New ()
	Create an object with Debug turned off, modified time initialized to zero, and reference counting on.
static void	BreakOnError ()
	This method is called when vtkErrorMacro executes.
static void	SetGlobalWarningDisplay (vtkTypeBool val)
	This is a global flag that controls whether any debug, warning or error messages are displayed.
static void	GlobalWarningDisplayOn ()
	This is a global flag that controls whether any debug, warning or error messages are displayed.
static void	GlobalWarningDisplayOff ()
	This is a global flag that controls whether any debug, warning or error messages are displayed.
static vtkTypeBool	GetGlobalWarningDisplay ()
	This is a global flag that controls whether any debug, warning or error messages are displayed.
Static Public Member Functions inherited from vtkObjectBase
static vtkTypeBool	IsTypeOf (const char *name)
	Return 1 if this class type is the same type of (or a subclass of) the named class.
static vtkIdType	GetNumberOfGenerationsFromBaseType (const char *name)
	Given a the name of a base class of this class type, return the distance of inheritance between this class type and the named class (how many generations of inheritance are there between this class and the named class).
static vtkObjectBase *	New ()
	Create an object with Debug turned off, modified time initialized to zero, and reference counting on.
static void	SetMemkindDirectory (const char *directoryname)
	The name of a directory, ideally mounted -o dax, to memory map an extended memory space within.
static bool	GetUsingMemkind ()
	A global state flag that controls whether vtkObjects are constructed in the usual way (the default) or within the extended memory space.

Protected Member Functions
virtual vtkObjectBase *	NewInstanceInternal () const
	vtkGarbageCollector ()
	~vtkGarbageCollector () override
Protected Member Functions inherited from vtkObject
	vtkObject ()
	~vtkObject () override
void	RegisterInternal (vtkObjectBase *, vtkTypeBool check) override
void	UnRegisterInternal (vtkObjectBase *, vtkTypeBool check) override
void	InternalGrabFocus (vtkCommand *mouseEvents, vtkCommand *keypressEvents=nullptr)
	These methods allow a command to exclusively grab all events.
void	InternalReleaseFocus ()
	These methods allow a command to exclusively grab all events.
Protected Member Functions inherited from vtkObjectBase
	vtkObjectBase ()
virtual	~vtkObjectBase ()
virtual void	RegisterInternal (vtkObjectBase *, vtkTypeBool check)
virtual void	UnRegisterInternal (vtkObjectBase *, vtkTypeBool check)
virtual void	ReportReferences (vtkGarbageCollector *)
virtual void	ObjectFinalize ()
	vtkObjectBase (const vtkObjectBase &)
void	operator= (const vtkObjectBase &)

Friends
class	vtkGarbageCollectorManager
class	vtkObjectBaseToGarbageCollectorFriendship
void VTKCOMMONCORE_EXPORT	vtkGarbageCollectorReportInternal (vtkGarbageCollector *, vtkObjectBase *, void *, const char *)

Additional Inherited Members
Static Protected Member Functions inherited from vtkObjectBase
static vtkMallocingFunction	GetCurrentMallocFunction ()
static vtkReallocingFunction	GetCurrentReallocFunction ()
static vtkFreeingFunction	GetCurrentFreeFunction ()
static vtkFreeingFunction	GetAlternateFreeFunction ()
Protected Attributes inherited from vtkObject
bool	Debug
vtkTimeStamp	MTime
vtkSubjectHelper *	SubjectHelper
std::string	ObjectName
Protected Attributes inherited from vtkObjectBase
std::atomic< int32_t >	ReferenceCount
vtkWeakPointerBase **	WeakPointers

Detailed Description

Detect and break reference loops.

vtkGarbageCollector is used by VTK classes that may be involved in reference counting loops (such as Algorithm <-> Executive). It detects strongly connected components of the reference graph that have been leaked deletes them. The garbage collector uses the ReportReferences method to search the reference graph and construct a net reference count for each connected component. If the net reference count is zero the entire set of objects is deleted. Deleting each component may leak other components, which are then collected recursively.

To enable garbage collection for a class, add these members:

public:
 bool UsesGarbageCollector() const override { return true; }
 
protected:
 
 void ReportReferences(vtkGarbageCollector* collector) override
 {
   // Report references held by this object that may be in a loop.
   this->Superclass::ReportReferences(collector);
   vtkGarbageCollectorReport(collector, this->OtherObject, "Other Object");
 }

The implementations should be in the .cxx file in practice. It is important that the reference be reported using the real pointer or smart pointer instance that holds the reference. When collecting the garbage collector will actually set this pointer to nullptr. The destructor of the class should be written to deal with this. It is also expected that an invariant is maintained for any reference that is reported. The variable holding the reference must always either be nullptr or refer to a fully constructed valid object. Therefore code like "this->Object->UnRegister(this)" must be avoided if "this->Object" is a reported reference because it is possible that the object is deleted before UnRegister returns but then "this->Object" will be left as a dangling pointer. Instead use code like

vtkObjectBase* obj = this->Object;
this->Object = 0;
obj->UnRegister(this);

so that the reported reference maintains the invariant.

If subclassing from a class that already supports garbage collection, one need only provide the ReportReferences method.

Tests:

vtkGarbageCollector (Tests)

Definition at line 83 of file vtkGarbageCollector.h.

Member Typedef Documentation

Superclass

typedef vtkObject vtkGarbageCollector::Superclass

Definition at line 86 of file vtkGarbageCollector.h.

Constructor & Destructor Documentation

vtkGarbageCollector()

vtkGarbageCollector::vtkGarbageCollector ( )

protected

~vtkGarbageCollector()

vtkGarbageCollector::~vtkGarbageCollector ( )

overrideprotected

Member Function Documentation

IsTypeOf()

static vtkTypeBool vtkGarbageCollector::IsTypeOf ( const char *  type )

static

IsA()

virtual vtkTypeBool vtkGarbageCollector::IsA ( const char *  name )

virtual

Return 1 if this class is the same type of (or a subclass of) the named class.

Returns 0 otherwise. This method works in combination with vtkTypeMacro found in vtkSetGet.h.

Reimplemented from vtkObjectBase.

SafeDownCast()

static vtkGarbageCollector * vtkGarbageCollector::SafeDownCast ( vtkObjectBase *  o )

static

NewInstanceInternal()

virtual vtkObjectBase * vtkGarbageCollector::NewInstanceInternal ( ) const

protectedvirtual

NewInstance()

vtkGarbageCollector * vtkGarbageCollector::NewInstance

(

)

const

PrintSelf()

void vtkGarbageCollector::PrintSelf ( ostream &  os, vtkIndent  indent  )

overridevirtual

Methods invoked by print to print information about the object including superclasses.

Typically not called by the user (use Print() instead) but used in the hierarchical print process to combine the output of several classes.

Reimplemented from vtkObjectBase.

New()

static vtkGarbageCollector * vtkGarbageCollector::New ( )

static

Collect() [1/2]

static void vtkGarbageCollector::Collect ( )

static

Collect immediately using any objects whose collection was previously deferred as a root for the reference graph walk.

Strongly connected components in the reference graph are identified. Those with a net reference count of zero are deleted. When a component is deleted it may remove references to other components that are not part of the same reference loop but are held by objects in the original component. These removed references are handled as any other and their corresponding checks may be deferred. This method keeps collecting until no deferred collection checks remain.

Collect() [2/2]

static void vtkGarbageCollector::Collect ( vtkObjectBase *  root )

static

Collect immediately using the given object as the root for a reference graph walk.

Strongly connected components in the reference graph are identified. Those with a net reference count of zero are deleted. When a component is deleted it may remove references to other components that are not part of the same reference loop but are held by objects in the original component. These removed references are handled as any other and their corresponding checks may be deferred. This method does continue collecting in this case.

DeferredCollectionPush()

static void vtkGarbageCollector::DeferredCollectionPush ( )

static

Push/Pop whether to do deferred collection.

Whenever the total number of pushes exceeds the total number of pops collection will be deferred. Code can call the Collect method directly to force collection.

DeferredCollectionPop()

static void vtkGarbageCollector::DeferredCollectionPop ( )

static

Push/Pop whether to do deferred collection.

Whenever the total number of pushes exceeds the total number of pops collection will be deferred. Code can call the Collect method directly to force collection.

SetGlobalDebugFlag()

static void vtkGarbageCollector::SetGlobalDebugFlag ( bool  flag )

static

Set/Get global garbage collection debugging flag.

When set to true, all garbage collection checks will produce debugging information.

GetGlobalDebugFlag()

static bool vtkGarbageCollector::GetGlobalDebugFlag ( )

static

Set/Get global garbage collection debugging flag.

When set to true, all garbage collection checks will produce debugging information.

Friends And Related Symbol Documentation

vtkGarbageCollectorManager

friend class vtkGarbageCollectorManager

friend

Definition at line 168 of file vtkGarbageCollector.h.

vtkObjectBaseToGarbageCollectorFriendship

friend class vtkObjectBaseToGarbageCollectorFriendship

friend

Definition at line 169 of file vtkGarbageCollector.h.

vtkGarbageCollectorReportInternal

void VTKCOMMONCORE_EXPORT vtkGarbageCollectorReportInternal ( vtkGarbageCollector *  , vtkObjectBase *  , void *  , const char *    )

friend

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The documentation for this class was generated from the following file:

• Common/Core/vtkGarbageCollector.h