DUK_LOCAL void duk__queue_refzero(duk_heap *heap, duk_heaphdr *hdr) {
/* tail insert: don't disturb head in case refzero is running */
if (heap->refzero_list != NULL) {
duk_heaphdr *hdr_prev;
hdr_prev = heap->refzero_list_tail;
DUK_ASSERT(hdr_prev != NULL);
DUK_ASSERT(DUK_HEAPHDR_GET_NEXT(heap, hdr_prev) == NULL);
DUK_HEAPHDR_SET_NEXT(heap, hdr, NULL);
DUK_HEAPHDR_SET_PREV(heap, hdr, hdr_prev);
DUK_HEAPHDR_SET_NEXT(heap, hdr_prev, hdr);
DUK_ASSERT_HEAPHDR_LINKS(heap, hdr);
DUK_ASSERT_HEAPHDR_LINKS(heap, hdr_prev);
heap->refzero_list_tail = hdr;
} else {
DUK_ASSERT(heap->refzero_list_tail == NULL);
DUK_HEAPHDR_SET_NEXT(heap, hdr, NULL);
DUK_HEAPHDR_SET_PREV(heap, hdr, NULL);
DUK_ASSERT_HEAPHDR_LINKS(heap, hdr);
heap->refzero_list = hdr;
heap->refzero_list_tail = hdr;
}
}
DUK_LOCAL void duk__init_object_parts(duk_heap *heap, duk_hobject *obj, duk_uint_t hobject_flags) {
#if defined(DUK_USE_EXPLICIT_NULL_INIT)
DUK_HOBJECT_SET_PROPS(heap, obj, NULL);
#endif
/* XXX: macro? sets both heaphdr and object flags */
obj->hdr.h_flags = hobject_flags;
DUK_HEAPHDR_SET_TYPE(&obj->hdr, DUK_HTYPE_OBJECT); /* also goes into flags */
#if defined(DUK_USE_HEAPPTR16)
/* Zero encoded pointer is required to match NULL */
DUK_HEAPHDR_SET_NEXT(heap, &obj->hdr, NULL);
#if defined(DUK_USE_DOUBLE_LINKED_HEAP)
DUK_HEAPHDR_SET_PREV(heap, &obj->hdr, NULL);
#endif
#endif
DUK_ASSERT_HEAPHDR_LINKS(heap, &obj->hdr);
DUK_HEAP_INSERT_INTO_HEAP_ALLOCATED(heap, &obj->hdr);
/*
* obj->props is intentionally left as NULL, and duk_hobject_props.c must deal
* with this properly. This is intentional: empty objects consume a minimum
* amount of memory. Further, an initial allocation might fail and cause
* 'obj' to "leak" (require a mark-and-sweep) since it is not reachable yet.
*/
}
DUK_INTERNAL void duk_heap_insert_into_heap_allocated(duk_heap *heap, duk_heaphdr *hdr) {
DUK_ASSERT(DUK_HEAPHDR_GET_TYPE(hdr) != DUK_HTYPE_STRING);
#ifdef DUK_USE_DOUBLE_LINKED_HEAP
if (heap->heap_allocated) {
DUK_ASSERT(DUK_HEAPHDR_GET_PREV(heap, heap->heap_allocated) == NULL);
DUK_HEAPHDR_SET_PREV(heap, heap->heap_allocated, hdr);
}
DUK_HEAPHDR_SET_PREV(heap, hdr, NULL);
#endif
DUK_HEAPHDR_SET_NEXT(heap, hdr, heap->heap_allocated);
heap->heap_allocated = hdr;
}
/* arbitrary remove only works with double linked heap, and is only required by
* reference counting so far.
*/
DUK_INTERNAL void duk_heap_remove_any_from_heap_allocated(duk_heap *heap, duk_heaphdr *hdr) {
DUK_ASSERT(DUK_HEAPHDR_GET_TYPE(hdr) != DUK_HTYPE_STRING);
if (DUK_HEAPHDR_GET_PREV(heap, hdr)) {
DUK_HEAPHDR_SET_NEXT(heap, DUK_HEAPHDR_GET_PREV(heap, hdr), DUK_HEAPHDR_GET_NEXT(heap, hdr));
} else {
heap->heap_allocated = DUK_HEAPHDR_GET_NEXT(heap, hdr);
}
if (DUK_HEAPHDR_GET_NEXT(heap, hdr)) {
DUK_HEAPHDR_SET_PREV(heap, DUK_HEAPHDR_GET_NEXT(heap, hdr), DUK_HEAPHDR_GET_PREV(heap, hdr));
} else {
;
}
}
DUK_LOCAL void duk__sweep_stringtable(duk_heap *heap, duk_size_t *out_count_keep) {
duk_hstring *h;
duk_hstring *prev;
duk_uint32_t i;
#if defined(DUK_USE_DEBUG)
duk_size_t count_free = 0;
#endif
duk_size_t count_keep = 0;
DUK_DD(DUK_DDPRINT("duk__sweep_stringtable: %p", (void *) heap));
#if defined(DUK_USE_STRTAB_PTRCOMP)
if (heap->strtable16 == NULL) {
#else
if (heap->strtable == NULL) {
#endif
goto done;
}
for (i = 0; i < heap->st_size; i++) {
#if defined(DUK_USE_STRTAB_PTRCOMP)
h = DUK_USE_HEAPPTR_DEC16(heap->heap_udata, heap->strtable16[i]);
#else
h = heap->strtable[i];
#endif
prev = NULL;
while (h != NULL) {
duk_hstring *next;
next = h->hdr.h_next;
if (DUK_HEAPHDR_HAS_REACHABLE((duk_heaphdr *) h)) {
DUK_HEAPHDR_CLEAR_REACHABLE((duk_heaphdr *) h);
count_keep++;
prev = h;
} else {
#if defined(DUK_USE_DEBUG)
count_free++;
#endif
#if defined(DUK_USE_REFERENCE_COUNTING)
/* Non-zero refcounts should not happen for unreachable strings,
* because we refcount finalize all unreachable objects which
* should have decreased unreachable string refcounts to zero
* (even for cycles).
*/
DUK_ASSERT(DUK_HEAPHDR_GET_REFCOUNT((duk_heaphdr *) h) == 0);
#endif
/* deal with weak references first */
duk_heap_strcache_string_remove(heap, (duk_hstring *) h);
/* remove the string from the string table */
duk_heap_strtable_unlink_prev(heap, (duk_hstring *) h, (duk_hstring *) prev);
/* free inner references (these exist e.g. when external
* strings are enabled) and the struct itself.
*/
duk_free_hstring(heap, (duk_hstring *) h);
/* don't update 'prev'; it should be last string kept */
}
h = next;
}
}
done:
#if defined(DUK_USE_DEBUG)
DUK_D(DUK_DPRINT("mark-and-sweep sweep stringtable: %ld freed, %ld kept",
(long) count_free, (long) count_keep));
#endif
*out_count_keep = count_keep;
}
/*
* Sweep heap
*/
DUK_LOCAL void duk__sweep_heap(duk_heap *heap, duk_int_t flags, duk_size_t *out_count_keep) {
duk_heaphdr *prev; /* last element that was left in the heap */
duk_heaphdr *curr;
duk_heaphdr *next;
#if defined(DUK_USE_DEBUG)
duk_size_t count_free = 0;
duk_size_t count_finalize = 0;
duk_size_t count_rescue = 0;
#endif
duk_size_t count_keep = 0;
DUK_UNREF(flags);
DUK_DD(DUK_DDPRINT("duk__sweep_heap: %p", (void *) heap));
prev = NULL;
curr = heap->heap_allocated;
heap->heap_allocated = NULL;
while (curr) {
/* Strings and ROM objects are never placed on the heap allocated list. */
DUK_ASSERT(DUK_HEAPHDR_GET_TYPE(curr) != DUK_HTYPE_STRING);
DUK_ASSERT(!DUK_HEAPHDR_HAS_READONLY(curr));
next = DUK_HEAPHDR_GET_NEXT(heap, curr);
if (DUK_HEAPHDR_HAS_REACHABLE(curr)) {
/*
* Reachable object, keep
*/
DUK_DDD(DUK_DDDPRINT("sweep, reachable: %p", (void *) curr));
if (DUK_HEAPHDR_HAS_FINALIZABLE(curr)) {
/*
* If object has been marked finalizable, move it to the
* "to be finalized" work list. It will be collected on
* the next mark-and-sweep if it is still unreachable
* after running the finalizer.
*/
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZED(curr));
DUK_ASSERT(DUK_HEAPHDR_GET_TYPE(curr) == DUK_HTYPE_OBJECT);
DUK_DDD(DUK_DDDPRINT("object has finalizer, move to finalization work list: %p", (void *) curr));
#if defined(DUK_USE_DOUBLE_LINKED_HEAP)
if (heap->finalize_list) {
DUK_HEAPHDR_SET_PREV(heap, heap->finalize_list, curr);
}
DUK_HEAPHDR_SET_PREV(heap, curr, NULL);
#endif
DUK_HEAPHDR_SET_NEXT(heap, curr, heap->finalize_list);
DUK_ASSERT_HEAPHDR_LINKS(heap, curr);
heap->finalize_list = curr;
#if defined(DUK_USE_DEBUG)
count_finalize++;
#endif
} else {
/*
* Object will be kept; queue object back to heap_allocated (to tail)
*/
if (DUK_HEAPHDR_HAS_FINALIZED(curr)) {
/*
* Object's finalizer was executed on last round, and
* object has been happily rescued.
*/
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZABLE(curr));
DUK_ASSERT(DUK_HEAPHDR_GET_TYPE(curr) == DUK_HTYPE_OBJECT);
DUK_DD(DUK_DDPRINT("object rescued during mark-and-sweep finalization: %p", (void *) curr));
#if defined(DUK_USE_DEBUG)
count_rescue++;
#endif
} else {
/*
* Plain, boring reachable object.
*/
DUK_DD(DUK_DDPRINT("keep object: %!iO", curr));
count_keep++;
}
if (!heap->heap_allocated) {
heap->heap_allocated = curr;
}
if (prev) {
DUK_HEAPHDR_SET_NEXT(heap, prev, curr);
}
#if defined(DUK_USE_DOUBLE_LINKED_HEAP)
DUK_HEAPHDR_SET_PREV(heap, curr, prev);
#endif
DUK_ASSERT_HEAPHDR_LINKS(heap, prev);
DUK_ASSERT_HEAPHDR_LINKS(heap, curr);
prev = curr;
}
DUK_HEAPHDR_CLEAR_REACHABLE(curr);
DUK_HEAPHDR_CLEAR_FINALIZED(curr);
DUK_HEAPHDR_CLEAR_FINALIZABLE(curr);
DUK_ASSERT(!DUK_HEAPHDR_HAS_REACHABLE(curr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZED(curr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZABLE(curr));
curr = next;
} else {
/*
* Unreachable object, free
*/
DUK_DDD(DUK_DDDPRINT("sweep, not reachable: %p", (void *) curr));
#if defined(DUK_USE_REFERENCE_COUNTING)
/* Non-zero refcounts should not happen because we refcount
* finalize all unreachable objects which should cancel out
* refcounts (even for cycles).
*/
DUK_ASSERT(DUK_HEAPHDR_GET_REFCOUNT(curr) == 0);
#endif
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZABLE(curr));
if (DUK_HEAPHDR_HAS_FINALIZED(curr)) {
DUK_DDD(DUK_DDDPRINT("finalized object not rescued: %p", (void *) curr));
}
/* Note: object cannot be a finalizable unreachable object, as
* they have been marked temporarily reachable for this round,
* and are handled above.
*/
#if defined(DUK_USE_DEBUG)
count_free++;
#endif
/* weak refs should be handled here, but no weak refs for
* any non-string objects exist right now.
*/
/* free object and all auxiliary (non-heap) allocs */
duk_heap_free_heaphdr_raw(heap, curr);
curr = next;
}
}
if (prev) {
DUK_HEAPHDR_SET_NEXT(heap, prev, NULL);
}
DUK_ASSERT_HEAPHDR_LINKS(heap, prev);
#if defined(DUK_USE_DEBUG)
DUK_D(DUK_DPRINT("mark-and-sweep sweep objects (non-string): %ld freed, %ld kept, %ld rescued, %ld queued for finalization",
(long) count_free, (long) count_keep, (long) count_rescue, (long) count_finalize));
#endif
*out_count_keep = count_keep;
}
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 */
}
static void duk__sweep_heap(duk_heap *heap, duk_int_t flags, duk_size_t *out_count_keep) {
duk_heaphdr *prev; /* last element that was left in the heap */
duk_heaphdr *curr;
duk_heaphdr *next;
#ifdef DUK_USE_DEBUG
duk_size_t count_free = 0;
duk_size_t count_finalize = 0;
duk_size_t count_rescue = 0;
#endif
duk_size_t count_keep = 0;
DUK_UNREF(flags);
DUK_DD(DUK_DDPRINT("duk__sweep_heap: %p", (void *) heap));
prev = NULL;
curr = heap->heap_allocated;
heap->heap_allocated = NULL;
while (curr) {
/* strings are never placed on the heap allocated list */
DUK_ASSERT(DUK_HEAPHDR_GET_TYPE(curr) != DUK_HTYPE_STRING);
next = DUK_HEAPHDR_GET_NEXT(curr);
if (DUK_HEAPHDR_HAS_REACHABLE(curr)) {
/*
* Reachable object, keep
*/
DUK_DDD(DUK_DDDPRINT("sweep, reachable: %p", (void *) curr));
if (DUK_HEAPHDR_HAS_FINALIZABLE(curr)) {
/*
* If object has been marked finalizable, move it to the
* "to be finalized" work list. It will be collected on
* the next mark-and-sweep if it is still unreachable
* after running the finalizer.
*/
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZED(curr));
DUK_ASSERT(DUK_HEAPHDR_GET_TYPE(curr) == DUK_HTYPE_OBJECT);
DUK_DDD(DUK_DDDPRINT("object has finalizer, move to finalization work list: %p", (void *) curr));
#ifdef DUK_USE_DOUBLE_LINKED_HEAP
if (heap->finalize_list) {
DUK_HEAPHDR_SET_PREV(heap->finalize_list, curr);
}
DUK_HEAPHDR_SET_PREV(curr, NULL);
#endif
DUK_HEAPHDR_SET_NEXT(curr, heap->finalize_list);
heap->finalize_list = curr;
#ifdef DUK_USE_DEBUG
count_finalize++;
#endif
} else {
/*
* Object will be kept; queue object back to heap_allocated (to tail)
*/
if (DUK_HEAPHDR_HAS_FINALIZED(curr)) {
/*
* Object's finalizer was executed on last round, and
* object has been happily rescued.
*/
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZABLE(curr));
DUK_ASSERT(DUK_HEAPHDR_GET_TYPE(curr) == DUK_HTYPE_OBJECT);
DUK_DD(DUK_DDPRINT("object rescued during mark-and-sweep finalization: %p", (void *) curr));
#ifdef DUK_USE_DEBUG
count_rescue++;
#endif
} else {
/*
* Plain, boring reachable object.
*/
count_keep++;
}
if (!heap->heap_allocated) {
heap->heap_allocated = curr;
}
if (prev) {
DUK_HEAPHDR_SET_NEXT(prev, curr);
}
#ifdef DUK_USE_DOUBLE_LINKED_HEAP
DUK_HEAPHDR_SET_PREV(curr, prev);
#endif
prev = curr;
}
DUK_HEAPHDR_CLEAR_REACHABLE(curr);
DUK_HEAPHDR_CLEAR_FINALIZED(curr);
DUK_HEAPHDR_CLEAR_FINALIZABLE(curr);
DUK_ASSERT(!DUK_HEAPHDR_HAS_REACHABLE(curr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZED(curr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZABLE(curr));
curr = next;
} else {
/*
* Unreachable object, free
*/
DUK_DDD(DUK_DDDPRINT("sweep, not reachable: %p", (void *) curr));
#if defined(DUK_USE_REFERENCE_COUNTING)
/* Non-zero refcounts should not happen because we refcount
* finalize all unreachable objects which should cancel out
* refcounts (even for cycles).
*/
DUK_ASSERT(DUK_HEAPHDR_GET_REFCOUNT(curr) == 0);
#endif
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZABLE(curr));
if (DUK_HEAPHDR_HAS_FINALIZED(curr)) {
DUK_DDD(DUK_DDDPRINT("finalized object not rescued: %p", (void *) curr));
}
/* Note: object cannot be a finalizable unreachable object, as
* they have been marked temporarily reachable for this round,
* and are handled above.
*/
#ifdef DUK_USE_DEBUG
count_free++;
#endif
/* weak refs should be handled here, but no weak refs for
* any non-string objects exist right now.
*/
/* free object and all auxiliary (non-heap) allocs */
duk_heap_free_heaphdr_raw(heap, curr);
curr = next;
}
}
if (prev) {
DUK_HEAPHDR_SET_NEXT(prev, NULL);
}
#ifdef DUK_USE_DEBUG
DUK_D(DUK_DPRINT("mark-and-sweep sweep objects (non-string): %d freed, %d kept, %d rescued, %d queued for finalization",
(int) count_free, (int) count_keep, (int) count_rescue, (int) count_finalize));
#endif
*out_count_keep = count_keep;
}
