cppgc::subtle Namespace Reference

Classes
class	DisallowGarbageCollectionScope
class	HeapConsistency
class	HeapState
class	NoGarbageCollectionScope
struct	ObjectSizeTrait
struct	ObjectSizeTrait< T, false >
struct	ObjectSizeTrait< T, true >

Typedefs
template<typename T >
using	CrossThreadPersistent = internal::BasicCrossThreadPersistent< T, internal::StrongCrossThreadPersistentPolicy >
template<typename T >
using	WeakCrossThreadPersistent = internal::BasicCrossThreadPersistent< T, internal::WeakCrossThreadPersistentPolicy >
template<typename T >
using	UncompressedMember = internal::BasicMember< T, internal::StrongMemberTag, internal::DijkstraWriteBarrierPolicy, internal::DefaultMemberCheckingPolicy, internal::RawPointer >

Functions
template<typename T >
void	FreeUnreferencedObject (HeapHandle &heap_handle, T &object)
template<typename T >
bool	Resize (T &object, AdditionalBytes additional_bytes)

Typedef Documentation

CrossThreadPersistent

template<typename T >

using cppgc::subtle::CrossThreadPersistent = typedef internal::BasicCrossThreadPersistent< T, internal::StrongCrossThreadPersistentPolicy>

DO NOT USE: Has known caveats, see below.

CrossThreadPersistent allows retaining objects from threads other than the thread the owning heap is operating on.

Known caveats:

• Does not protect the heap owning an object from terminating.
• Reaching transitively through the graph is unsupported as objects may be moved concurrently on the thread owning the object.

UncompressedMember

template<typename T >

using cppgc::subtle::UncompressedMember = typedef internal::BasicMember< T, internal::StrongMemberTag, internal::DijkstraWriteBarrierPolicy, internal::DefaultMemberCheckingPolicy, internal::RawPointer>

UncompressedMember. Use with care in hot paths that would otherwise cause many decompression cycles.

WeakCrossThreadPersistent

template<typename T >

using cppgc::subtle::WeakCrossThreadPersistent = typedef internal::BasicCrossThreadPersistent< T, internal::WeakCrossThreadPersistentPolicy>

DO NOT USE: Has known caveats, see below.

CrossThreadPersistent allows weakly retaining objects from threads other than the thread the owning heap is operating on.

Known caveats:

• Does not protect the heap owning an object from terminating.
• Reaching transitively through the graph is unsupported as objects may be moved concurrently on the thread owning the object.

Function Documentation

FreeUnreferencedObject()

template<typename T >

void cppgc::subtle::FreeUnreferencedObject	(	HeapHandle &	heap_handle,
		T &	object
	)

Informs the garbage collector that object can be immediately reclaimed. The destructor may not be invoked immediately but only on next garbage collection.

It is up to the embedder to guarantee that no other object holds a reference to object after calling FreeUnreferencedObject(). In case such a reference exists, it's use results in a use-after-free.

To aid in using the API, FreeUnreferencedObject() may be called from destructors on objects that would be reclaimed in the same garbage collection cycle.

Parameters

heap_handle	The corresponding heap.
object	Reference to an object that is of type GarbageCollected and should be immediately reclaimed.

Resize()

template<typename T >

bool cppgc::subtle::Resize	(	T &	object,
		AdditionalBytes	additional_bytes
	)

Tries to resize object of type T with additional bytes on top of sizeof(T). Resizing is only useful with trailing inlined storage, see e.g. MakeGarbageCollected(AllocationHandle&, AdditionalBytes).

Resize() performs growing or shrinking as needed and may skip the operation for internal reasons, see return value.

It is up to the embedder to guarantee that in case of shrinking a larger object down, the reclaimed area is not used anymore. Any subsequent use results in a use-after-free.

The object must be live when calling Resize().

Parameters

object	Reference to an object that is of type GarbageCollected and should be resized.
additional_bytes	Bytes in addition to sizeof(T) that the object should provide.

Returns

true when the operation was successful and the result can be relied on, and false otherwise.