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
}
DUK_LOCAL void duk__assert_valid_refcounts(duk_heap *heap) {
duk_heaphdr *hdr = heap->heap_allocated;
while (hdr) {
if (DUK_HEAPHDR_GET_REFCOUNT(hdr) == 0 &&
DUK_HEAPHDR_HAS_FINALIZED(hdr)) {
/* An object may be in heap_allocated list with a zero
* refcount if it has just been finalized and is waiting
* to be collected by the next cycle.
*/
} else if (DUK_HEAPHDR_GET_REFCOUNT(hdr) == 0) {
/* An object may be in heap_allocated list with a zero
* refcount also if it is a temporary object created by
* a finalizer; because finalization now runs inside
* mark-and-sweep, such objects will not be queued to
* refzero_list and will thus appear here with refcount
* zero.
*/
#if 0 /* this case can no longer occur because refcount is unsigned */
} else if (DUK_HEAPHDR_GET_REFCOUNT(hdr) < 0) {
DUK_D(DUK_DPRINT("invalid refcount: %ld, %p -> %!O",
(hdr != NULL ? (long) DUK_HEAPHDR_GET_REFCOUNT(hdr) : (long) 0),
(void *) hdr, (duk_heaphdr *) hdr));
DUK_ASSERT(DUK_HEAPHDR_GET_REFCOUNT(hdr) > 0);
#endif
}
hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr);
}
}
DUK_LOCAL void duk__mark_finalizable(duk_heap *heap) {
duk_hthread *thr;
duk_heaphdr *hdr;
duk_size_t count_finalizable = 0;
DUK_DD(DUK_DDPRINT("duk__mark_finalizable: %p", (void *) heap));
thr = duk__get_temp_hthread(heap);
DUK_ASSERT(thr != NULL);
hdr = heap->heap_allocated;
while (hdr) {
/* A finalizer is looked up from the object and up its prototype chain
* (which allows inherited finalizers). A prototype loop must not cause
* an error to be thrown here; duk_hobject_hasprop_raw() will ignore a
* prototype loop silently and indicate that the property doesn't exist.
*/
if (!DUK_HEAPHDR_HAS_REACHABLE(hdr) &&
DUK_HEAPHDR_GET_TYPE(hdr) == DUK_HTYPE_OBJECT &&
!DUK_HEAPHDR_HAS_FINALIZED(hdr) &&
duk_hobject_hasprop_raw(thr, (duk_hobject *) hdr, DUK_HTHREAD_STRING_INT_FINALIZER(thr))) {
/* heaphdr:
* - is not reachable
* - is an object
* - is not a finalized object
* - has a finalizer
*/
DUK_DD(DUK_DDPRINT("unreachable heap object will be "
"finalized -> mark as finalizable "
"and treat as a reachability root: %p",
(void *) hdr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_READONLY(hdr));
DUK_HEAPHDR_SET_FINALIZABLE(hdr);
count_finalizable ++;
}
hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr);
}
if (count_finalizable == 0) {
return;
}
DUK_DD(DUK_DDPRINT("marked %ld heap objects as finalizable, now mark them reachable",
(long) count_finalizable));
hdr = heap->heap_allocated;
while (hdr) {
if (DUK_HEAPHDR_HAS_FINALIZABLE(hdr)) {
duk__mark_heaphdr(heap, hdr);
}
hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr);
}
/* Caller will finish the marking process if we hit a recursion limit. */
}
DUK_LOCAL void duk__print_shared_heaphdr(duk__dprint_state *st, duk_heaphdr *h) {
duk_fixedbuffer *fb = st->fb;
if (st->heavy) {
duk_fb_sprintf(fb, "(%p)", (void *) h);
}
if (!h) {
return;
}
if (st->binary) {
duk_size_t i;
duk_fb_put_byte(fb, (duk_uint8_t) DUK_ASC_LBRACKET);
for (i = 0; i < (duk_size_t) sizeof(*h); i++) {
duk_fb_sprintf(fb, "%02lx", (unsigned long) ((duk_uint8_t *)h)[i]);
}
duk_fb_put_byte(fb, (duk_uint8_t) DUK_ASC_RBRACKET);
}
#if defined(DUK_USE_REFERENCE_COUNTING) /* currently implicitly also DUK_USE_DOUBLE_LINKED_HEAP */
if (st->heavy) {
duk_fb_sprintf(fb, "[h_next=%p,h_prev=%p,h_refcount=%lu,h_flags=%08lx,type=%ld,"
"reachable=%ld,temproot=%ld,finalizable=%ld,finalized=%ld]",
(void *) DUK_HEAPHDR_GET_NEXT(NULL, h),
(void *) DUK_HEAPHDR_GET_PREV(NULL, h),
(unsigned long) DUK_HEAPHDR_GET_REFCOUNT(h),
(unsigned long) DUK_HEAPHDR_GET_FLAGS(h),
(long) DUK_HEAPHDR_GET_TYPE(h),
(long) (DUK_HEAPHDR_HAS_REACHABLE(h) ? 1 : 0),
(long) (DUK_HEAPHDR_HAS_TEMPROOT(h) ? 1 : 0),
(long) (DUK_HEAPHDR_HAS_FINALIZABLE(h) ? 1 : 0),
(long) (DUK_HEAPHDR_HAS_FINALIZED(h) ? 1 : 0));
}
#else
if (st->heavy) {
duk_fb_sprintf(fb, "[h_next=%p,h_flags=%08lx,type=%ld,reachable=%ld,temproot=%ld,finalizable=%ld,finalized=%ld]",
(void *) DUK_HEAPHDR_GET_NEXT(NULL, h),
(unsigned long) DUK_HEAPHDR_GET_FLAGS(h),
(long) DUK_HEAPHDR_GET_TYPE(h),
(long) (DUK_HEAPHDR_HAS_REACHABLE(h) ? 1 : 0),
(long) (DUK_HEAPHDR_HAS_TEMPROOT(h) ? 1 : 0),
(long) (DUK_HEAPHDR_HAS_FINALIZABLE(h) ? 1 : 0),
(long) (DUK_HEAPHDR_HAS_FINALIZED(h) ? 1 : 0));
}
#endif
}
DUK_INTERNAL void duk_hobject_run_finalizer(duk_hthread *thr, duk_hobject *obj) {
duk_context *ctx = (duk_context *) thr;
duk_ret_t rc;
#if defined(DUK_USE_ASSERTIONS)
duk_idx_t entry_top;
#endif
DUK_DDD(DUK_DDDPRINT("running object finalizer for object: %p", (void *) obj));
DUK_ASSERT(thr != NULL);
DUK_ASSERT(ctx != NULL);
DUK_ASSERT(obj != NULL);
DUK_ASSERT_VALSTACK_SPACE(thr, 1);
#if defined(DUK_USE_ASSERTIONS)
entry_top = duk_get_top(ctx);
#endif
/*
* Get and call the finalizer. All of this must be wrapped
* in a protected call, because even getting the finalizer
* may trigger an error (getter may throw one, for instance).
*/
DUK_ASSERT(!DUK_HEAPHDR_HAS_READONLY((duk_heaphdr *) obj));
if (DUK_HEAPHDR_HAS_FINALIZED((duk_heaphdr *) obj)) {
DUK_D(DUK_DPRINT("object already finalized, avoid running finalizer twice: %!O", obj));
return;
}
DUK_HEAPHDR_SET_FINALIZED((duk_heaphdr *) obj); /* ensure never re-entered until rescue cycle complete */
if (DUK_HOBJECT_HAS_EXOTIC_PROXYOBJ(obj)) {
/* This shouldn't happen; call sites should avoid looking up
* _Finalizer "through" a Proxy, but ignore if we come here
* with a Proxy to avoid finalizer re-entry.
*/
DUK_D(DUK_DPRINT("object is a proxy, skip finalizer call"));
return;
}
/* XXX: use a NULL error handler for the finalizer call? */
DUK_DDD(DUK_DDDPRINT("-> finalizer found, calling wrapped finalize helper"));
duk_push_hobject(ctx, obj); /* this also increases refcount by one */
rc = duk_safe_call(ctx, duk__finalize_helper, NULL /*udata*/, 0 /*nargs*/, 1 /*nrets*/); /* -> [... obj retval/error] */
DUK_ASSERT_TOP(ctx, entry_top + 2); /* duk_safe_call discipline */
if (rc != DUK_EXEC_SUCCESS) {
/* Note: we ask for one return value from duk_safe_call to get this
* error debugging here.
*/
DUK_D(DUK_DPRINT("wrapped finalizer call failed for object %p (ignored); error: %!T",
(void *) obj, (duk_tval *) duk_get_tval(ctx, -1)));
}
duk_pop_2(ctx); /* -> [...] */
DUK_ASSERT_TOP(ctx, entry_top);
}
static void duk__mark_finalizable(duk_heap *heap) {
duk_hthread *thr;
duk_heaphdr *hdr;
int count_finalizable = 0;
DUK_DD(DUK_DDPRINT("duk__mark_finalizable: %p", (void *) heap));
thr = duk__get_temp_hthread(heap);
DUK_ASSERT(thr != NULL);
hdr = heap->heap_allocated;
while (hdr) {
/* A finalizer is looked up from the object and up its prototype chain
* (which allows inherited finalizers).
*/
if (!DUK_HEAPHDR_HAS_REACHABLE(hdr) &&
DUK_HEAPHDR_GET_TYPE(hdr) == DUK_HTYPE_OBJECT &&
!DUK_HEAPHDR_HAS_FINALIZED(hdr) &&
duk_hobject_hasprop_raw(thr, (duk_hobject *) hdr, DUK_HTHREAD_STRING_INT_FINALIZER(thr))) {
/* heaphdr:
* - is not reachable
* - is an object
* - is not a finalized object
* - has a finalizer
*/
DUK_DD(DUK_DDPRINT("unreachable heap object will be finalized -> mark as finalizable and treat as a reachability root: %p", hdr));
DUK_HEAPHDR_SET_FINALIZABLE(hdr);
count_finalizable ++;
}
hdr = DUK_HEAPHDR_GET_NEXT(hdr);
}
if (count_finalizable == 0) {
return;
}
DUK_DD(DUK_DDPRINT("marked %d heap objects as finalizable, now mark them reachable", count_finalizable));
hdr = heap->heap_allocated;
while (hdr) {
if (DUK_HEAPHDR_HAS_FINALIZABLE(hdr)) {
duk__mark_heaphdr(heap, hdr);
}
hdr = DUK_HEAPHDR_GET_NEXT(hdr);
}
/* Caller will finish the marking process if we hit a recursion limit. */
}
DUK_LOCAL void duk__clear_finalize_list_flags(duk_heap *heap) {
duk_heaphdr *hdr;
DUK_DD(DUK_DDPRINT("duk__clear_finalize_list_flags: %p", (void *) heap));
hdr = heap->finalize_list;
while (hdr) {
DUK_HEAPHDR_CLEAR_REACHABLE(hdr);
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZABLE(hdr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZED(hdr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_TEMPROOT(hdr));
hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr);
}
}
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
}
static void duk__assert_heaphdr_flags(duk_heap *heap) {
duk_heaphdr *hdr;
hdr = heap->heap_allocated;
while (hdr) {
DUK_ASSERT(!DUK_HEAPHDR_HAS_REACHABLE(hdr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_TEMPROOT(hdr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZABLE(hdr));
/* may have FINALIZED */
hdr = DUK_HEAPHDR_GET_NEXT(hdr);
}
#ifdef DUK_USE_REFERENCE_COUNTING
hdr = heap->refzero_list;
while (hdr) {
DUK_ASSERT(!DUK_HEAPHDR_HAS_REACHABLE(hdr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_TEMPROOT(hdr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZABLE(hdr));
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZED(hdr));
hdr = DUK_HEAPHDR_GET_NEXT(hdr);
}
#endif /* DUK_USE_REFERENCE_COUNTING */
}
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__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;
}
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);
}
DUK_LOCAL 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(heap, h1) == NULL);
DUK_ASSERT(DUK_HEAPHDR_GET_TYPE(h1) == DUK_HTYPE_OBJECT); /* currently, always the case */
#if defined(DUK_USE_REFZERO_FINALIZER_TORTURE)
/* Torture option to shake out finalizer side effect issues:
* make a bogus function call for every finalizable object,
* essentially simulating the case where everything has a
* finalizer.
*/
DUK_DD(DUK_DDPRINT("refzero torture enabled, fake finalizer"));
DUK_ASSERT(DUK_HEAPHDR_GET_REFCOUNT(h1) == 0);
DUK_HEAPHDR_PREINC_REFCOUNT(h1); /* bump refcount to prevent refzero during finalizer processing */
duk__refcount_run_torture_finalizer(thr, obj); /* must never longjmp */
DUK_HEAPHDR_PREDEC_REFCOUNT(h1); /* remove artificial bump */
DUK_ASSERT_DISABLE(h1->h_refcount >= 0); /* refcount is unsigned, so always true */
#endif
/*
* 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).
*/
/* An object may have FINALIZED here if it was finalized by mark-and-sweep
* on a previous run and refcount then decreased to zero. We won't run the
* finalizer again 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(DUK_HEAPHDR_GET_REFCOUNT(h1) == 0);
DUK_HEAPHDR_PREINC_REFCOUNT(h1); /* bump refcount to prevent refzero during finalizer processing */
duk_hobject_run_finalizer(thr, obj); /* must never longjmp */
DUK_ASSERT(DUK_HEAPHDR_HAS_FINALIZED(h1)); /* duk_hobject_run_finalizer() sets */
DUK_HEAPHDR_PREDEC_REFCOUNT(h1); /* remove artificial bump */
DUK_ASSERT_DISABLE(h1->h_refcount >= 0); /* refcount is unsigned, so always true */
if (DUK_HEAPHDR_GET_REFCOUNT(h1) != 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(heap, h1);
if (h2) {
DUK_HEAPHDR_SET_PREV(heap, 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_ASSERT(!DUK_HEAPHDR_HAS_FINALIZABLE(h1));
DUK_ASSERT(DUK_HEAPHDR_HAS_FINALIZED(h1));
DUK_HEAPHDR_CLEAR_FINALIZED(h1);
h2 = heap->heap_allocated;
DUK_HEAPHDR_SET_PREV(heap, h1, NULL);
if (h2) {
DUK_HEAPHDR_SET_PREV(heap, h2, h1);
}
DUK_HEAPHDR_SET_NEXT(heap, h1, h2);
DUK_ASSERT_HEAPHDR_LINKS(heap, h1);
DUK_ASSERT_HEAPHDR_LINKS(heap, h2);
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 */
}