DUK_LOCAL void duk__run_object_finalizers(duk_heap *heap, duk_small_uint_t flags) {
duk_heaphdr *curr;
duk_heaphdr *next;
#if defined(DUK_USE_DEBUG)
duk_size_t count = 0;
#endif
duk_hthread *thr;
DUK_DD(DUK_DDPRINT("duk__run_object_finalizers: %p", (void *) heap));
thr = duk__get_temp_hthread(heap);
DUK_ASSERT(thr != NULL);
curr = heap->finalize_list;
while (curr) {
DUK_DDD(DUK_DDDPRINT("mark-and-sweep finalize: %p", (void *) curr));
DUK_ASSERT(DUK_HEAPHDR_GET_TYPE(curr) == DUK_HTYPE_OBJECT); /* only objects have finalizers */
DUK_ASSERT(!DUK_HEAPHDR_HAS_REACHABLE(curr)); /* flags have been already cleared */
DUK_ASSERT(!DUK_HEAPHDR_HAS_TEMPROOT(curr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZABLE(curr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZED(curr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_READONLY(curr)); /* No finalizers for ROM objects */
if (DUK_LIKELY((flags & DUK_MS_FLAG_SKIP_FINALIZERS) == 0)) {
/* Run the finalizer, duk_hobject_run_finalizer() sets FINALIZED.
* Next mark-and-sweep will collect the object unless it has
* become reachable (i.e. rescued). FINALIZED prevents the
* finalizer from being executed again before that.
*/
duk_hobject_run_finalizer(thr, (duk_hobject *) curr); /* must never longjmp */
DUK_ASSERT(DUK_HEAPHDR_HAS_FINALIZED(curr));
} else {
/* Used during heap destruction: don't actually run finalizers
* because we're heading into forced finalization. Instead,
* queue finalizable objects back to the heap_allocated list.
*/
DUK_D(DUK_DPRINT("skip finalizers flag set, queue object to heap_allocated without finalizing"));
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZED(curr));
}
/* queue back to heap_allocated */
next = DUK_HEAPHDR_GET_NEXT(heap, curr);
DUK_HEAP_INSERT_INTO_HEAP_ALLOCATED(heap, curr);
curr = next;
#if defined(DUK_USE_DEBUG)
count++;
#endif
}
/* finalize_list will always be processed completely */
heap->finalize_list = NULL;
#if defined(DUK_USE_DEBUG)
DUK_D(DUK_DPRINT("mark-and-sweep finalize objects: %ld finalizers called", (long) count));
#endif
}
static void duk__run_object_finalizers(duk_heap *heap) {
duk_heaphdr *curr;
duk_heaphdr *next;
#ifdef DUK_USE_DEBUG
int count = 0;
#endif
duk_hthread *thr;
DUK_DD(DUK_DDPRINT("duk__run_object_finalizers: %p", (void *) heap));
thr = duk__get_temp_hthread(heap);
DUK_ASSERT(thr != NULL);
curr = heap->finalize_list;
while (curr) {
DUK_DDD(DUK_DDDPRINT("mark-and-sweep finalize: %p", (void *) curr));
DUK_ASSERT(DUK_HEAPHDR_GET_TYPE(curr) == DUK_HTYPE_OBJECT); /* only objects have finalizers */
DUK_ASSERT(!DUK_HEAPHDR_HAS_REACHABLE(curr)); /* flags have been already cleared */
DUK_ASSERT(!DUK_HEAPHDR_HAS_TEMPROOT(curr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZABLE(curr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZED(curr));
/* run the finalizer */
duk_hobject_run_finalizer(thr, (duk_hobject *) curr); /* must never longjmp */
/* mark FINALIZED, for next mark-and-sweep (will collect unless has become reachable;
* prevent running finalizer again if reachable)
*/
DUK_HEAPHDR_SET_FINALIZED(curr);
/* queue back to heap_allocated */
next = DUK_HEAPHDR_GET_NEXT(curr);
DUK_HEAP_INSERT_INTO_HEAP_ALLOCATED(heap, curr);
curr = next;
#ifdef DUK_USE_DEBUG
count++;
#endif
}
/* finalize_list will always be processed completely */
heap->finalize_list = NULL;
#ifdef DUK_USE_DEBUG
DUK_D(DUK_DPRINT("mark-and-sweep finalize objects: %d finalizers called", count));
#endif
}
DUK_LOCAL void duk__free_run_finalizers(duk_heap *heap) {
duk_hthread *thr;
duk_heaphdr *curr;
#ifdef DUK_USE_DEBUG
duk_size_t count_obj = 0;
#endif
DUK_ASSERT(heap != NULL);
DUK_ASSERT(heap->heap_thread != NULL);
#ifdef DUK_USE_REFERENCE_COUNTING
DUK_ASSERT(heap->refzero_list == NULL); /* refzero not running -> must be empty */
#endif
#ifdef DUK_USE_MARK_AND_SWEEP
DUK_ASSERT(heap->finalize_list == NULL); /* mark-and-sweep not running -> must be empty */
#endif
/* XXX: here again finalizer thread is the heap_thread which needs
* to be coordinated with finalizer thread fixes.
*/
thr = heap->heap_thread;
DUK_ASSERT(thr != NULL);
curr = heap->heap_allocated;
while (curr) {
if (DUK_HEAPHDR_GET_TYPE(curr) == DUK_HTYPE_OBJECT) {
/* Only objects in heap_allocated may have finalizers. Check that
* the object itself has a _Finalizer property so that we don't
* execute finalizers for e.g. Proxy objects.
*/
DUK_ASSERT(thr != NULL);
DUK_ASSERT(curr != NULL);
if (duk_hobject_hasprop_raw(thr, (duk_hobject *) curr, DUK_HTHREAD_STRING_INT_FINALIZER(thr))) {
duk_hobject_run_finalizer(thr, (duk_hobject *) curr);
}
#ifdef DUK_USE_DEBUG
count_obj++;
#endif
}
curr = DUK_HEAPHDR_GET_NEXT(curr);
}
/* Note: count includes all objects, not only those with an actual finalizer. */
#ifdef DUK_USE_DEBUG
DUK_D(DUK_DPRINT("checked %ld objects for finalizers before freeing heap", (long) count_obj));
#endif
}
static void duk__free_run_finalizers(duk_heap *heap) {
duk_heaphdr *curr;
#ifdef DUK_USE_DEBUG
duk_size_t count_obj = 0;
#endif
DUK_ASSERT(heap != NULL);
DUK_ASSERT(heap->heap_thread != NULL);
#ifdef DUK_USE_REFERENCE_COUNTING
DUK_ASSERT(heap->refzero_list == NULL); /* refzero not running -> must be empty */
#endif
#ifdef DUK_USE_MARK_AND_SWEEP
DUK_ASSERT(heap->finalize_list == NULL); /* mark-and-sweep not running -> must be empty */
#endif
/* FIXME: here again finalizer thread is the heap_thread which needs
* to be coordinated with finalizer thread fixes.
*/
curr = heap->heap_allocated;
while (curr) {
if (DUK_HEAPHDR_GET_TYPE(curr) == DUK_HTYPE_OBJECT) {
/* Only objects in heap_allocated may have finalizers. */
DUK_ASSERT(heap->heap_thread != NULL);
DUK_ASSERT(curr != NULL);
duk_hobject_run_finalizer(heap->heap_thread, (duk_hobject *) curr);
#ifdef DUK_USE_DEBUG
count_obj++;
#endif
}
curr = DUK_HEAPHDR_GET_NEXT(curr);
}
/* Note: count includes all objects, not only those with an actual finalizer. */
#ifdef DUK_USE_DEBUG
DUK_D(DUK_DPRINT("checked %d objects for finalizers before freeing heap", (int) count_obj));
#endif
}
static void duk__refzero_free_pending(duk_hthread *thr) {
duk_heaphdr *h1, *h2;
duk_heap *heap;
duk_int_t count = 0;
DUK_ASSERT(thr != NULL);
DUK_ASSERT(thr->heap != NULL);
heap = thr->heap;
DUK_ASSERT(heap != NULL);
/*
* Detect recursive invocation
*/
if (DUK_HEAP_HAS_REFZERO_FREE_RUNNING(heap)) {
DUK_DDD(DUK_DDDPRINT("refzero free running, skip run"));
return;
}
/*
* Churn refzero_list until empty
*/
DUK_HEAP_SET_REFZERO_FREE_RUNNING(heap);
while (heap->refzero_list) {
duk_hobject *obj;
duk_bool_t rescued = 0;
/*
* Pick an object from the head (don't remove yet).
*/
h1 = heap->refzero_list;
obj = (duk_hobject *) h1;
DUK_DD(DUK_DDPRINT("refzero processing %p: %!O", (void *) h1, (duk_heaphdr *) h1));
DUK_ASSERT(DUK_HEAPHDR_GET_PREV(h1) == NULL);
DUK_ASSERT(DUK_HEAPHDR_GET_TYPE(h1) == DUK_HTYPE_OBJECT); /* currently, always the case */
/*
* Finalizer check.
*
* Note: running a finalizer may have arbitrary side effects, e.g.
* queue more objects on refzero_list (tail), or even trigger a
* mark-and-sweep.
*
* Note: quick reject check should match vast majority of
* objects and must be safe (not throw any errors, ever).
*/
/* XXX: If object has FINALIZED, it was finalized by mark-and-sweep on
* its previous run. Any point in running finalizer again here? If
* finalization semantics is changed so that finalizer is only run once,
* checking for FINALIZED would happen here.
*/
/* A finalizer is looked up from the object and up its prototype chain
* (which allows inherited finalizers).
*/
if (duk_hobject_hasprop_raw(thr, obj, DUK_HTHREAD_STRING_INT_FINALIZER(thr))) {
DUK_DDD(DUK_DDDPRINT("object has a finalizer, run it"));
DUK_ASSERT(h1->h_refcount == 0);
h1->h_refcount++; /* bump refcount to prevent refzero during finalizer processing */
duk_hobject_run_finalizer(thr, obj); /* must never longjmp */
h1->h_refcount--; /* remove artificial bump */
DUK_ASSERT_DISABLE(h1->h_refcount >= 0); /* refcount is unsigned, so always true */
if (h1->h_refcount != 0) {
DUK_DDD(DUK_DDDPRINT("-> object refcount after finalization non-zero, object will be rescued"));
rescued = 1;
} else {
DUK_DDD(DUK_DDDPRINT("-> object refcount still zero after finalization, object will be freed"));
}
}
/* Refzero head is still the same. This is the case even if finalizer
* inserted more refzero objects; they are inserted to the tail.
*/
DUK_ASSERT(h1 == heap->refzero_list);
/*
* Remove the object from the refzero list. This cannot be done
* before a possible finalizer has been executed; the finalizer
* may trigger a mark-and-sweep, and mark-and-sweep must be able
* to traverse a complete refzero_list.
*/
h2 = DUK_HEAPHDR_GET_NEXT(h1);
if (h2) {
DUK_HEAPHDR_SET_PREV(h2, NULL); /* not strictly necessary */
heap->refzero_list = h2;
} else {
heap->refzero_list = NULL;
heap->refzero_list_tail = NULL;
}
/*
* Rescue or free.
*/
if (rescued) {
/* yes -> move back to heap allocated */
DUK_DD(DUK_DDPRINT("object rescued during refcount finalization: %p", (void *) h1));
DUK_HEAPHDR_SET_PREV(h1, NULL);
DUK_HEAPHDR_SET_NEXT(h1, heap->heap_allocated);
heap->heap_allocated = h1;
} else {
/* no -> decref members, then free */
duk__refcount_finalize_hobject(thr, obj);
duk_heap_free_heaphdr_raw(heap, h1);
}
count++;
}
DUK_HEAP_CLEAR_REFZERO_FREE_RUNNING(heap);
DUK_DDD(DUK_DDDPRINT("refzero processed %ld objects", (long) count));
/*
* Once the whole refzero cascade has been freed, check for
* a voluntary mark-and-sweep.
*/
#if defined(DUK_USE_MARK_AND_SWEEP) && defined(DUK_USE_VOLUNTARY_GC)
/* 'count' is more or less comparable to normal trigger counter update
* which happens in memory block (re)allocation.
*/
heap->mark_and_sweep_trigger_counter -= count;
if (heap->mark_and_sweep_trigger_counter <= 0) {
duk_bool_t rc;
duk_small_uint_t flags = 0; /* not emergency */
DUK_D(DUK_DPRINT("refcount triggering mark-and-sweep"));
rc = duk_heap_mark_and_sweep(heap, flags);
DUK_UNREF(rc);
DUK_D(DUK_DPRINT("refcount triggered mark-and-sweep => rc %ld", (long) rc));
}
#endif /* DUK_USE_MARK_AND_SWEEP && DUK_USE_VOLUNTARY_GC */
}
DUK_LOCAL void duk__free_stringtable(duk_heap *heap) {
duk_uint_fast32_t i;
/* strings are only tracked by stringtable */
#if defined(DUK_USE_HEAPPTR16)
if (heap->strtable16) {
#else
if (heap->strtable) {
#endif
for (i = 0; i < (duk_uint_fast32_t) heap->st_size; i++) {
duk_hstring *e;
#if defined(DUK_USE_HEAPPTR16)
e = (duk_hstring *) DUK_USE_HEAPPTR_DEC16(heap->strtable16[i]);
#else
e = heap->strtable[i];
#endif
if (e == NULL || e == DUK_STRTAB_DELETED_MARKER(heap)) {
continue;
}
DUK_ASSERT(e != NULL);
/* strings may have inner refs (extdata) in some cases */
duk_free_hstring_inner(heap, (duk_hstring *) e);
DUK_DDD(DUK_DDDPRINT("FINALFREE (string): %!iO",
(duk_heaphdr *) e));
DUK_FREE(heap, e);
#if 0 /* not strictly necessary */
heap->strtable[i] = NULL;
#endif
}
#if defined(DUK_USE_HEAPPTR16)
DUK_FREE(heap, heap->strtable16);
#else
DUK_FREE(heap, heap->strtable);
#endif
#if 0 /* not strictly necessary */
heap->strtable = NULL;
#endif
}
}
DUK_LOCAL void duk__free_run_finalizers(duk_heap *heap) {
duk_hthread *thr;
duk_heaphdr *curr;
#ifdef DUK_USE_DEBUG
duk_size_t count_obj = 0;
#endif
DUK_ASSERT(heap != NULL);
DUK_ASSERT(heap->heap_thread != NULL);
#ifdef DUK_USE_REFERENCE_COUNTING
DUK_ASSERT(heap->refzero_list == NULL); /* refzero not running -> must be empty */
#endif
#ifdef DUK_USE_MARK_AND_SWEEP
DUK_ASSERT(heap->finalize_list == NULL); /* mark-and-sweep not running -> must be empty */
#endif
/* XXX: here again finalizer thread is the heap_thread which needs
* to be coordinated with finalizer thread fixes.
*/
thr = heap->heap_thread;
DUK_ASSERT(thr != NULL);
curr = heap->heap_allocated;
while (curr) {
if (DUK_HEAPHDR_GET_TYPE(curr) == DUK_HTYPE_OBJECT) {
/* Only objects in heap_allocated may have finalizers. Check that
* the object itself has a _Finalizer property so that we don't
* execute finalizers for e.g. Proxy objects.
*/
DUK_ASSERT(thr != NULL);
DUK_ASSERT(curr != NULL);
if (duk_hobject_hasprop_raw(thr, (duk_hobject *) curr, DUK_HTHREAD_STRING_INT_FINALIZER(thr))) {
duk_hobject_run_finalizer(thr, (duk_hobject *) curr);
}
#ifdef DUK_USE_DEBUG
count_obj++;
#endif
}
curr = DUK_HEAPHDR_GET_NEXT(curr);
}
/* Note: count includes all objects, not only those with an actual finalizer. */
#ifdef DUK_USE_DEBUG
DUK_D(DUK_DPRINT("checked %ld objects for finalizers before freeing heap", (long) count_obj));
#endif
}
DUK_LOCAL void duk__free_run_finalizers(duk_heap *heap) {
duk_hthread *thr;
duk_heaphdr *curr;
duk_uint_t round_no;
duk_size_t count_all;
duk_size_t count_finalized;
duk_size_t curr_limit;
DUK_ASSERT(heap != NULL);
DUK_ASSERT(heap->heap_thread != NULL);
#if defined(DUK_USE_REFERENCE_COUNTING)
DUK_ASSERT(heap->refzero_list == NULL); /* refzero not running -> must be empty */
#endif
#if defined(DUK_USE_MARK_AND_SWEEP)
DUK_ASSERT(heap->finalize_list == NULL); /* mark-and-sweep not running -> must be empty */
#endif
/* XXX: here again finalizer thread is the heap_thread which needs
* to be coordinated with finalizer thread fixes.
*/
thr = heap->heap_thread;
DUK_ASSERT(thr != NULL);
/* Prevent mark-and-sweep for the pending finalizers, also prevents
* refzero handling from moving objects away from the heap_allocated
* list. (The flag meaning is slightly abused here.)
*/
DUK_ASSERT(!DUK_HEAP_HAS_MARKANDSWEEP_RUNNING(heap));
DUK_HEAP_SET_MARKANDSWEEP_RUNNING(heap);
curr_limit = 0; /* suppress warning, not used */
for (round_no = 0; ; round_no++) {
curr = heap->heap_allocated;
count_all = 0;
count_finalized = 0;
while (curr) {
count_all++;
if (DUK_HEAPHDR_GET_TYPE(curr) == DUK_HTYPE_OBJECT) {
/* Only objects in heap_allocated may have finalizers. Check that
* the object itself has a _Finalizer property (own or inherited)
* so that we don't execute finalizers for e.g. Proxy objects.
*/
DUK_ASSERT(thr != NULL);
DUK_ASSERT(curr != NULL);
if (duk_hobject_hasprop_raw(thr, (duk_hobject *) curr, DUK_HTHREAD_STRING_INT_FINALIZER(thr))) {
if (!DUK_HEAPHDR_HAS_FINALIZED((duk_heaphdr *) curr)) {
DUK_ASSERT(DUK_HEAP_HAS_FINALIZER_NORESCUE(heap)); /* maps to finalizer 2nd argument */
duk_hobject_run_finalizer(thr, (duk_hobject *) curr);
count_finalized++;
}
}
}
curr = DUK_HEAPHDR_GET_NEXT(heap, curr);
}
/* Each round of finalizer execution may spawn new finalizable objects
* which is normal behavior for some applications. Allow multiple
* rounds of finalization, but use a shrinking limit based on the
* first round to detect the case where a runaway finalizer creates
* an unbounded amount of new finalizable objects. Finalizer rescue
* is not supported: the semantics are unclear because most of the
* objects being finalized here are already reachable. The finalizer
* is given a boolean to indicate that rescue is not possible.
*
* See discussion in: https://github.com/svaarala/duktape/pull/473
*/
if (round_no == 0) {
/* Cannot wrap: each object is at least 8 bytes so count is
* at most 1/8 of that.
*/
curr_limit = count_all * 2;
} else {
curr_limit = (curr_limit * 3) / 4; /* Decrease by 25% every round */
}
DUK_D(DUK_DPRINT("finalizer round %ld complete, %ld objects, tried to execute %ld finalizers, current limit is %ld",
(long) round_no, (long) count_all, (long) count_finalized, (long) curr_limit));
if (count_finalized == 0) {
DUK_D(DUK_DPRINT("no more finalizable objects, forced finalization finished"));
break;
}
if (count_finalized >= curr_limit) {
DUK_D(DUK_DPRINT("finalizer count above limit, potentially runaway finalizer; skip remaining finalizers"));
break;
}
}
DUK_ASSERT(DUK_HEAP_HAS_MARKANDSWEEP_RUNNING(heap));
DUK_HEAP_CLEAR_MARKANDSWEEP_RUNNING(heap);
}
