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Sfink/Draft - GC Pointer Handling: Difference between revisions
→Persistent (heap-allocated) Pointers
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* The structure containing the pointer is sometimes allocated on the stack, sometimes on the heap | * The structure containing the pointer is sometimes allocated on the stack, sometimes on the heap | ||
Also, persistent pointer updates may be subject to write barriers for incremental and/or generational GC, where any modification must be monitored to maintain various invariants. Basically, you can't add, remove, or change a heap-stored gcthing pointer without informing the GC about it. | Also, persistent pointer updates may be subject to write barriers for incremental and/or generational GC, where any modification must be monitored to maintain various invariants. Basically, you can't add, remove, or change a heap-stored gcthing pointer without informing the GC about it. See [[SpiderMonkey/Internals/Garbage_collection]] for details. | ||
The simplest approach is to use HeapPtr<T> as the type of gcthing pointer fields. Any writes through a HeapPtr will trigger the needed barriers. There's also EncapsulatedPtr<T>, which is the same but different. Or RelocatablePtr<T>, which is different but the same. | The simplest approach is to use HeapPtr<T> as the type of gcthing pointer fields. Any writes through a HeapPtr will trigger the needed barriers. There's also EncapsulatedPtr<T>, which is the same but different. Or RelocatablePtr<T>, which is different but the same. | ||