DUK_LOCAL duk_ret_t duk__finalize_helper(duk_context *ctx, void *udata) {
duk_hthread *thr;
DUK_ASSERT(ctx != NULL);
thr = (duk_hthread *) ctx;
DUK_UNREF(udata);
DUK_DDD(DUK_DDDPRINT("protected finalization helper running"));
/* [... obj] */
/* XXX: Finalizer lookup should traverse the prototype chain (to allow
* inherited finalizers) but should not invoke accessors or proxy object
* behavior. At the moment this lookup will invoke proxy behavior, so
* caller must ensure that this function is not called if the target is
* a Proxy.
*/
duk_get_prop_stridx_short(ctx, -1, DUK_STRIDX_INT_FINALIZER); /* -> [... obj finalizer] */
if (!duk_is_callable(ctx, -1)) {
DUK_DDD(DUK_DDDPRINT("-> no finalizer or finalizer not callable"));
return 0;
}
duk_dup_m2(ctx);
duk_push_boolean(ctx, DUK_HEAP_HAS_FINALIZER_NORESCUE(thr->heap));
DUK_DDD(DUK_DDDPRINT("-> finalizer found, calling finalizer"));
duk_call(ctx, 2); /* [ ... obj finalizer obj heapDestruct ] -> [ ... obj retval ] */
DUK_DDD(DUK_DDDPRINT("finalizer finished successfully"));
return 0;
/* Note: we rely on duk_safe_call() to fix up the stack for the caller,
* so we don't need to pop stuff here. There is no return value;
* caller determines rescued status based on object refcount.
*/
}
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);
}
