Offer SPI to notify clients that GC has happened
https://bugs.webkit.org/show_bug.cgi?id=171980
Reviewed by Geoffrey Garen.
Sometimes when you're programming with weak references, it's most convenient if the GC tells
you when it finishes. This adds exactly such an API. This API is called at the *flip*: the
moment when the GC knows for sure which objects are dead and has definitely not allocated any
new objects or executed any JS code. The finalization part of the flip, which is where this
callback gets called, runs on the "main" thread - i.e. some thread that is attempting to
execute JS code and holds the JS lock. This will usually run as a side-effect of some
allocation or from the runloop.
This means, for example, that if you implemented a vector of weak references and registered a
callback to prune the vector of null weak references, then aside from the callback, nobody
would ever see a null weak reference in the vector.
- API/JSHeapFinalizerPrivate.cpp: Added.
(JSContextGroupAddHeapFinalizer):
(JSContextGroupRemoveHeapFinalizer):
- API/JSHeapFinalizerPrivate.h: Added.
- API/tests/testapi.c:
(heapFinalizer):
(testMarkingConstraintsAndHeapFinalizers):
(main):
(testMarkingConstraints): Deleted.
- CMakeLists.txt:
- JavaScriptCore.xcodeproj/project.pbxproj:
- heap/Heap.cpp:
(JSC::Heap::finalize):
(JSC::Heap::addHeapFinalizerCallback):
(JSC::Heap::removeHeapFinalizerCallback):
- heap/Heap.h:
- heap/HeapFinalizerCallback.cpp: Added.
(JSC::HeapFinalizerCallback::dump):
- heap/HeapFinalizerCallback.h: Added.
(JSC::HeapFinalizerCallback::HeapFinalizerCallback):
(JSC::HeapFinalizerCallback::operator==):
(JSC::HeapFinalizerCallback::operator!=):
(JSC::HeapFinalizerCallback::operator bool):
(JSC::HeapFinalizerCallback::run):
