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cosmopolitan/third_party/duktape/duk_heap_markandsweep.c

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/*
* Mark-and-sweep garbage collection.
*/
#include "third_party/duktape/duk_internal.h"
DUK_LOCAL_DECL void duk__mark_heaphdr(duk_heap *heap, duk_heaphdr *h);
DUK_LOCAL_DECL void duk__mark_heaphdr_nonnull(duk_heap *heap, duk_heaphdr *h);
DUK_LOCAL_DECL void duk__mark_tval(duk_heap *heap, duk_tval *tv);
DUK_LOCAL_DECL void duk__mark_tvals(duk_heap *heap, duk_tval *tv, duk_idx_t count);
/*
* Marking functions for heap types: mark children recursively.
*/
DUK_LOCAL void duk__mark_hstring(duk_heap *heap, duk_hstring *h) {
DUK_UNREF(heap);
DUK_UNREF(h);
DUK_DDD(DUK_DDDPRINT("duk__mark_hstring: %p", (void *) h));
DUK_ASSERT(h);
DUK_HSTRING_ASSERT_VALID(h);
/* nothing to process */
}
DUK_LOCAL void duk__mark_hobject(duk_heap *heap, duk_hobject *h) {
duk_uint_fast32_t i;
DUK_DDD(DUK_DDDPRINT("duk__mark_hobject: %p", (void *) h));
DUK_ASSERT(h);
DUK_HOBJECT_ASSERT_VALID(h);
/* XXX: use advancing pointers instead of index macros -> faster and smaller? */
for (i = 0; i < (duk_uint_fast32_t) DUK_HOBJECT_GET_ENEXT(h); i++) {
duk_hstring *key = DUK_HOBJECT_E_GET_KEY(heap, h, i);
if (key == NULL) {
continue;
}
duk__mark_heaphdr_nonnull(heap, (duk_heaphdr *) key);
if (DUK_HOBJECT_E_SLOT_IS_ACCESSOR(heap, h, i)) {
duk__mark_heaphdr(heap, (duk_heaphdr *) DUK_HOBJECT_E_GET_VALUE_PTR(heap, h, i)->a.get);
duk__mark_heaphdr(heap, (duk_heaphdr *) DUK_HOBJECT_E_GET_VALUE_PTR(heap, h, i)->a.set);
} else {
duk__mark_tval(heap, &DUK_HOBJECT_E_GET_VALUE_PTR(heap, h, i)->v);
}
}
for (i = 0; i < (duk_uint_fast32_t) DUK_HOBJECT_GET_ASIZE(h); i++) {
duk__mark_tval(heap, DUK_HOBJECT_A_GET_VALUE_PTR(heap, h, i));
}
/* Hash part is a 'weak reference' and does not contribute. */
duk__mark_heaphdr(heap, (duk_heaphdr *) DUK_HOBJECT_GET_PROTOTYPE(heap, h));
/* Fast path for objects which don't have a subclass struct, or have a
* subclass struct but nothing that needs marking in the subclass struct.
*/
if (DUK_HOBJECT_HAS_FASTREFS(h)) {
DUK_ASSERT(DUK_HOBJECT_ALLOWS_FASTREFS(h));
return;
}
DUK_ASSERT(DUK_HOBJECT_PROHIBITS_FASTREFS(h));
/* XXX: reorg, more common first */
if (DUK_HOBJECT_IS_COMPFUNC(h)) {
duk_hcompfunc *f = (duk_hcompfunc *) h;
duk_tval *tv, *tv_end;
duk_hobject **fn, **fn_end;
DUK_HCOMPFUNC_ASSERT_VALID(f);
/* 'data' is reachable through every compiled function which
* contains a reference.
*/
duk__mark_heaphdr(heap, (duk_heaphdr *) DUK_HCOMPFUNC_GET_DATA(heap, f));
duk__mark_heaphdr(heap, (duk_heaphdr *) DUK_HCOMPFUNC_GET_LEXENV(heap, f));
duk__mark_heaphdr(heap, (duk_heaphdr *) DUK_HCOMPFUNC_GET_VARENV(heap, f));
if (DUK_HCOMPFUNC_GET_DATA(heap, f) != NULL) {
tv = DUK_HCOMPFUNC_GET_CONSTS_BASE(heap, f);
tv_end = DUK_HCOMPFUNC_GET_CONSTS_END(heap, f);
while (tv < tv_end) {
duk__mark_tval(heap, tv);
tv++;
}
fn = DUK_HCOMPFUNC_GET_FUNCS_BASE(heap, f);
fn_end = DUK_HCOMPFUNC_GET_FUNCS_END(heap, f);
while (fn < fn_end) {
duk__mark_heaphdr_nonnull(heap, (duk_heaphdr *) *fn);
fn++;
}
} else {
/* May happen in some out-of-memory corner cases. */
DUK_D(DUK_DPRINT("duk_hcompfunc 'data' is NULL, skipping marking"));
}
} else if (DUK_HOBJECT_IS_DECENV(h)) {
duk_hdecenv *e = (duk_hdecenv *) h;
DUK_HDECENV_ASSERT_VALID(e);
duk__mark_heaphdr(heap, (duk_heaphdr *) e->thread);
duk__mark_heaphdr(heap, (duk_heaphdr *) e->varmap);
} else if (DUK_HOBJECT_IS_OBJENV(h)) {
duk_hobjenv *e = (duk_hobjenv *) h;
DUK_HOBJENV_ASSERT_VALID(e);
duk__mark_heaphdr_nonnull(heap, (duk_heaphdr *) e->target);
#if defined(DUK_USE_BUFFEROBJECT_SUPPORT)
} else if (DUK_HOBJECT_IS_BUFOBJ(h)) {
duk_hbufobj *b = (duk_hbufobj *) h;
DUK_HBUFOBJ_ASSERT_VALID(b);
duk__mark_heaphdr(heap, (duk_heaphdr *) b->buf);
duk__mark_heaphdr(heap, (duk_heaphdr *) b->buf_prop);
#endif /* DUK_USE_BUFFEROBJECT_SUPPORT */
} else if (DUK_HOBJECT_IS_BOUNDFUNC(h)) {
duk_hboundfunc *f = (duk_hboundfunc *) (void *) h;
DUK_HBOUNDFUNC_ASSERT_VALID(f);
duk__mark_tval(heap, &f->target);
duk__mark_tval(heap, &f->this_binding);
duk__mark_tvals(heap, f->args, f->nargs);
#if defined(DUK_USE_ES6_PROXY)
} else if (DUK_HOBJECT_IS_PROXY(h)) {
duk_hproxy *p = (duk_hproxy *) h;
DUK_HPROXY_ASSERT_VALID(p);
duk__mark_heaphdr_nonnull(heap, (duk_heaphdr *) p->target);
duk__mark_heaphdr_nonnull(heap, (duk_heaphdr *) p->handler);
#endif /* DUK_USE_ES6_PROXY */
} else if (DUK_HOBJECT_IS_THREAD(h)) {
duk_hthread *t = (duk_hthread *) h;
duk_activation *act;
duk_tval *tv;
DUK_HTHREAD_ASSERT_VALID(t);
tv = t->valstack;
while (tv < t->valstack_top) {
duk__mark_tval(heap, tv);
tv++;
}
for (act = t->callstack_curr; act != NULL; act = act->parent) {
duk__mark_heaphdr(heap, (duk_heaphdr *) DUK_ACT_GET_FUNC(act));
duk__mark_heaphdr(heap, (duk_heaphdr *) act->var_env);
duk__mark_heaphdr(heap, (duk_heaphdr *) act->lex_env);
#if defined(DUK_USE_NONSTD_FUNC_CALLER_PROPERTY)
duk__mark_heaphdr(heap, (duk_heaphdr *) act->prev_caller);
#endif
#if 0 /* nothing now */
for (cat = act->cat; cat != NULL; cat = cat->parent) {
}
#endif
}
duk__mark_heaphdr(heap, (duk_heaphdr *) t->resumer);
for (i = 0; i < DUK_NUM_BUILTINS; i++) {
duk__mark_heaphdr(heap, (duk_heaphdr *) t->builtins[i]);
}
} else {
/* We may come here if the object should have a FASTREFS flag
* but it's missing for some reason. Assert for never getting
* here; however, other than performance, this is harmless.
*/
DUK_D(DUK_DPRINT("missing FASTREFS flag for: %!iO", h));
DUK_ASSERT(0);
}
}
/* Mark any duk_heaphdr type. Recursion tracking happens only here. */
DUK_LOCAL void duk__mark_heaphdr(duk_heap *heap, duk_heaphdr *h) {
DUK_DDD(DUK_DDDPRINT("duk__mark_heaphdr %p, type %ld",
(void *) h,
(h != NULL ? (long) DUK_HEAPHDR_GET_TYPE(h) : (long) -1)));
/* XXX: add non-null variant? */
if (h == NULL) {
return;
}
DUK_HEAPHDR_ASSERT_VALID(h);
DUK_ASSERT(!DUK_HEAPHDR_HAS_READONLY(h) || DUK_HEAPHDR_HAS_REACHABLE(h));
#if defined(DUK_USE_ASSERTIONS) && defined(DUK_USE_REFERENCE_COUNTING)
if (!DUK_HEAPHDR_HAS_READONLY(h)) {
h->h_assert_refcount++; /* Comparison refcount: bump even if already reachable. */
}
#endif
if (DUK_HEAPHDR_HAS_REACHABLE(h)) {
DUK_DDD(DUK_DDDPRINT("already marked reachable, skip"));
return;
}
#if defined(DUK_USE_ROM_OBJECTS)
/* READONLY objects always have REACHABLE set, so the check above
* will prevent READONLY objects from being marked here.
*/
DUK_ASSERT(!DUK_HEAPHDR_HAS_READONLY(h));
#endif
DUK_HEAPHDR_SET_REACHABLE(h);
if (heap->ms_recursion_depth >= DUK_USE_MARK_AND_SWEEP_RECLIMIT) {
DUK_D(DUK_DPRINT("mark-and-sweep recursion limit reached, marking as temproot: %p", (void *) h));
DUK_HEAP_SET_MARKANDSWEEP_RECLIMIT_REACHED(heap);
DUK_HEAPHDR_SET_TEMPROOT(h);
return;
}
heap->ms_recursion_depth++;
DUK_ASSERT(heap->ms_recursion_depth != 0); /* Wrap. */
switch (DUK_HEAPHDR_GET_TYPE(h)) {
case DUK_HTYPE_STRING:
duk__mark_hstring(heap, (duk_hstring *) h);
break;
case DUK_HTYPE_OBJECT:
duk__mark_hobject(heap, (duk_hobject *) h);
break;
case DUK_HTYPE_BUFFER:
/* nothing to mark */
break;
default:
DUK_D(DUK_DPRINT("attempt to mark heaphdr %p with invalid htype %ld", (void *) h, (long) DUK_HEAPHDR_GET_TYPE(h)));
DUK_UNREACHABLE();
}
DUK_ASSERT(heap->ms_recursion_depth > 0);
heap->ms_recursion_depth--;
}
DUK_LOCAL void duk__mark_tval(duk_heap *heap, duk_tval *tv) {
DUK_DDD(DUK_DDDPRINT("duk__mark_tval %p", (void *) tv));
if (tv == NULL) {
return;
}
DUK_TVAL_ASSERT_VALID(tv);
if (DUK_TVAL_IS_HEAP_ALLOCATED(tv)) {
duk_heaphdr *h;
h = DUK_TVAL_GET_HEAPHDR(tv);
DUK_ASSERT(h != NULL);
duk__mark_heaphdr_nonnull(heap, h);
}
}
DUK_LOCAL void duk__mark_tvals(duk_heap *heap, duk_tval *tv, duk_idx_t count) {
DUK_ASSERT(count == 0 || tv != NULL);
while (count-- > 0) {
DUK_TVAL_ASSERT_VALID(tv);
if (DUK_TVAL_IS_HEAP_ALLOCATED(tv)) {
duk_heaphdr *h;
h = DUK_TVAL_GET_HEAPHDR(tv);
DUK_ASSERT(h != NULL);
duk__mark_heaphdr_nonnull(heap, h);
}
tv++;
}
}
/* Mark any duk_heaphdr type, caller guarantees a non-NULL pointer. */
DUK_LOCAL void duk__mark_heaphdr_nonnull(duk_heap *heap, duk_heaphdr *h) {
/* For now, just call the generic handler. Change when call sites
* are changed too.
*/
duk__mark_heaphdr(heap, h);
}
/*
* Mark the heap.
*/
DUK_LOCAL void duk__mark_roots_heap(duk_heap *heap) {
duk_small_uint_t i;
DUK_DD(DUK_DDPRINT("duk__mark_roots_heap: %p", (void *) heap));
duk__mark_heaphdr(heap, (duk_heaphdr *) heap->heap_thread);
duk__mark_heaphdr(heap, (duk_heaphdr *) heap->heap_object);
for (i = 0; i < DUK_HEAP_NUM_STRINGS; i++) {
duk_hstring *h = DUK_HEAP_GET_STRING(heap, i);
duk__mark_heaphdr(heap, (duk_heaphdr *) h);
}
duk__mark_tval(heap, &heap->lj.value1);
duk__mark_tval(heap, &heap->lj.value2);
#if defined(DUK_USE_DEBUGGER_SUPPORT)
for (i = 0; i < heap->dbg_breakpoint_count; i++) {
duk__mark_heaphdr(heap, (duk_heaphdr *) heap->dbg_breakpoints[i].filename);
}
#endif
}
/*
* Mark unreachable, finalizable objects.
*
* Such objects will be moved aside and their finalizers run later. They
* have to be treated as reachability roots for their properties etc to
* remain allocated. This marking is only done for unreachable values which
* would be swept later.
*
* Objects are first marked FINALIZABLE and only then marked as reachability
* roots; otherwise circular references might be handled inconsistently.
*/
#if defined(DUK_USE_FINALIZER_SUPPORT)
DUK_LOCAL void duk__mark_finalizable(duk_heap *heap) {
duk_heaphdr *hdr;
duk_size_t count_finalizable = 0;
DUK_DD(DUK_DDPRINT("duk__mark_finalizable: %p", (void *) heap));
DUK_ASSERT(heap->heap_thread != NULL);
hdr = heap->heap_allocated;
while (hdr != NULL) {
/* A finalizer is looked up from the object and up its
* prototype chain (which allows inherited finalizers).
* The finalizer is checked for using a duk_hobject flag
* which is kept in sync with the presence and callability
* of a _Finalizer hidden symbol.
*/
if (!DUK_HEAPHDR_HAS_REACHABLE(hdr) &&
DUK_HEAPHDR_IS_OBJECT(hdr) &&
!DUK_HEAPHDR_HAS_FINALIZED(hdr) &&
DUK_HOBJECT_HAS_FINALIZER_FAST(heap, (duk_hobject *) hdr)) {
/* heaphdr:
* - is not reachable
* - is an object
* - is not a finalized object waiting for rescue/keep decision
* - 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 != NULL) {
if (DUK_HEAPHDR_HAS_FINALIZABLE(hdr)) {
duk__mark_heaphdr_nonnull(heap, hdr);
}
hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr);
}
/* Caller will finish the marking process if we hit a recursion limit. */
}
#endif /* DUK_USE_FINALIZER_SUPPORT */
/*
* Mark objects on finalize_list.
*/
#if defined(DUK_USE_FINALIZER_SUPPORT)
DUK_LOCAL void duk__mark_finalize_list(duk_heap *heap) {
duk_heaphdr *hdr;
#if defined(DUK_USE_DEBUG)
duk_size_t count_finalize_list = 0;
#endif
DUK_DD(DUK_DDPRINT("duk__mark_finalize_list: %p", (void *) heap));
hdr = heap->finalize_list;
while (hdr != NULL) {
duk__mark_heaphdr_nonnull(heap, hdr);
hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr);
#if defined(DUK_USE_DEBUG)
count_finalize_list++;
#endif
}
#if defined(DUK_USE_DEBUG)
if (count_finalize_list > 0) {
DUK_D(DUK_DPRINT("marked %ld objects on the finalize_list as reachable (previous finalizer run skipped)",
(long) count_finalize_list));
}
#endif
}
#endif /* DUK_USE_FINALIZER_SUPPORT */
/*
* Fallback marking handler if recursion limit is reached.
*
* Iterates 'temproots' until recursion limit is no longer hit. Temproots
* can be in heap_allocated or finalize_list; refzero_list is now always
* empty for mark-and-sweep. A temproot may occur in finalize_list now if
* there are objects on the finalize_list and user code creates a reference
* from an object in heap_allocated to the object in finalize_list (which is
* now allowed), and it happened to coincide with the recursion depth limit.
*
* This is a slow scan, but guarantees that we finish with a bounded C stack.
*
* Note that nodes may have been marked as temproots before this scan begun,
* OR they may have been marked during the scan (as we process nodes
* recursively also during the scan). This is intended behavior.
*/
#if defined(DUK_USE_DEBUG)
DUK_LOCAL void duk__handle_temproot(duk_heap *heap, duk_heaphdr *hdr, duk_size_t *count) {
#else
DUK_LOCAL void duk__handle_temproot(duk_heap *heap, duk_heaphdr *hdr) {
#endif
DUK_ASSERT(hdr != NULL);
if (!DUK_HEAPHDR_HAS_TEMPROOT(hdr)) {
DUK_DDD(DUK_DDDPRINT("not a temp root: %p", (void *) hdr));
return;
}
DUK_DDD(DUK_DDDPRINT("found a temp root: %p", (void *) hdr));
DUK_HEAPHDR_CLEAR_TEMPROOT(hdr);
DUK_HEAPHDR_CLEAR_REACHABLE(hdr); /* Done so that duk__mark_heaphdr() works correctly. */
#if defined(DUK_USE_ASSERTIONS) && defined(DUK_USE_REFERENCE_COUNTING)
hdr->h_assert_refcount--; /* Same node visited twice. */
#endif
duk__mark_heaphdr_nonnull(heap, hdr);
#if defined(DUK_USE_DEBUG)
(*count)++;
#endif
}
DUK_LOCAL void duk__mark_temproots_by_heap_scan(duk_heap *heap) {
duk_heaphdr *hdr;
#if defined(DUK_USE_DEBUG)
duk_size_t count;
#endif
DUK_DD(DUK_DDPRINT("duk__mark_temproots_by_heap_scan: %p", (void *) heap));
while (DUK_HEAP_HAS_MARKANDSWEEP_RECLIMIT_REACHED(heap)) {
DUK_DD(DUK_DDPRINT("recursion limit reached, doing heap scan to continue from temproots"));
#if defined(DUK_USE_DEBUG)
count = 0;
#endif
DUK_HEAP_CLEAR_MARKANDSWEEP_RECLIMIT_REACHED(heap);
hdr = heap->heap_allocated;
while (hdr) {
#if defined(DUK_USE_DEBUG)
duk__handle_temproot(heap, hdr, &count);
#else
duk__handle_temproot(heap, hdr);
#endif
hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr);
}
#if defined(DUK_USE_FINALIZER_SUPPORT)
hdr = heap->finalize_list;
while (hdr) {
#if defined(DUK_USE_DEBUG)
duk__handle_temproot(heap, hdr, &count);
#else
duk__handle_temproot(heap, hdr);
#endif
hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr);
}
#endif
#if defined(DUK_USE_DEBUG)
DUK_DD(DUK_DDPRINT("temproot mark heap scan processed %ld temp roots", (long) count));
#endif
}
}
/*
* Finalize refcounts for heap elements just about to be freed.
* This must be done for all objects before freeing to avoid any
* stale pointer dereferences.
*
* Note that this must deduce the set of objects to be freed
* identically to duk__sweep_heap().
*/
#if defined(DUK_USE_REFERENCE_COUNTING)
DUK_LOCAL void duk__finalize_refcounts(duk_heap *heap) {
duk_heaphdr *hdr;
DUK_ASSERT(heap->heap_thread != NULL);
DUK_DD(DUK_DDPRINT("duk__finalize_refcounts: heap=%p", (void *) heap));
hdr = heap->heap_allocated;
while (hdr) {
if (!DUK_HEAPHDR_HAS_REACHABLE(hdr)) {
/*
* Unreachable object about to be swept. Finalize target refcounts
* (objects which the unreachable object points to) without doing
* refzero processing. Recursive decrefs are also prevented when
* refzero processing is disabled.
*
* Value cannot be a finalizable object, as they have been made
* temporarily reachable for this round.
*/
DUK_DDD(DUK_DDDPRINT("unreachable object, refcount finalize before sweeping: %p", (void *) hdr));
/* Finalize using heap->heap_thread; DECREF has a
* suppress check for mark-and-sweep which is based
* on heap->ms_running.
*/
duk_heaphdr_refcount_finalize_norz(heap, hdr);
}
hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr);
}
}
#endif /* DUK_USE_REFERENCE_COUNTING */
/*
* Clear (reachable) flags of finalize_list.
*
* We could mostly do in the sweep phase when we move objects from the
* heap into the finalize_list. However, if a finalizer run is skipped
* during a mark-and-sweep, the objects on the finalize_list will be marked
* reachable during the next mark-and-sweep. Since they're already on the
* finalize_list, no-one will be clearing their REACHABLE flag so we do it
* here. (This now overlaps with the sweep handling in a harmless way.)
*/
#if defined(DUK_USE_FINALIZER_SUPPORT)
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);
#if defined(DUK_USE_ASSERTIONS)
DUK_ASSERT(DUK_HEAPHDR_HAS_FINALIZABLE(hdr) || \
(heap->currently_finalizing == hdr));
#endif
/* DUK_HEAPHDR_FLAG_FINALIZED may be set. */
DUK_ASSERT(!DUK_HEAPHDR_HAS_TEMPROOT(hdr));
hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr);
}
}
#endif /* DUK_USE_FINALIZER_SUPPORT */
/*
* Sweep stringtable.
*/
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
/* For pinned strings the refcount has been
* bumped. We could unbump it here before
* freeing, but that's actually not necessary
* except for assertions.
*/
#if 0
if (DUK_HSTRING_HAS_PINNED_LITERAL(h)) {
DUK_ASSERT(DUK_HEAPHDR_GET_REFCOUNT((duk_heaphdr *) h) > 0U);
DUK_HSTRING_DECREF_NORZ(heap->heap_thread, h);
DUK_HSTRING_CLEAR_PINNED_LITERAL(h);
}
#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). However, pinned strings have a +1 bump.
*/
DUK_ASSERT(DUK_HEAPHDR_GET_REFCOUNT((duk_heaphdr *) h) ==
DUK_HSTRING_HAS_PINNED_LITERAL(h) ? 1U : 0U);
#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_small_uint_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_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:
* - If FINALIZABLE -> actually unreachable (but marked
* artificially reachable), queue to finalize_list.
* - If !FINALIZABLE but FINALIZED -> rescued after
* finalizer execution.
* - Otherwise just a normal, reachable object.
*
* Objects which are kept are queued to heap_allocated
* tail (we're essentially filtering heap_allocated in
* practice).
*/
#if defined(DUK_USE_FINALIZER_SUPPORT)
if (DUK_UNLIKELY(DUK_HEAPHDR_HAS_FINALIZABLE(curr))) {
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZED(curr));
DUK_ASSERT(DUK_HEAPHDR_GET_TYPE(curr) == DUK_HTYPE_OBJECT);
DUK_DD(DUK_DDPRINT("sweep; reachable, finalizable --> move to finalize_list: %p", (void *) curr));
#if defined(DUK_USE_REFERENCE_COUNTING)
DUK_HEAPHDR_PREINC_REFCOUNT(curr); /* Bump refcount so that refzero never occurs when pending a finalizer call. */
#endif
DUK_HEAP_INSERT_INTO_FINALIZE_LIST(heap, curr);
#if defined(DUK_USE_DEBUG)
count_finalize++;
#endif
}
else
#endif /* DUK_USE_FINALIZER_SUPPORT */
{
if (DUK_UNLIKELY(DUK_HEAPHDR_HAS_FINALIZED(curr))) {
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZABLE(curr));
DUK_ASSERT(DUK_HEAPHDR_GET_TYPE(curr) == DUK_HTYPE_OBJECT);
if (flags & DUK_MS_FLAG_POSTPONE_RESCUE) {
DUK_DD(DUK_DDPRINT("sweep; reachable, finalized, but postponing rescue decisions --> keep object (with FINALIZED set): %!iO", curr));
count_keep++;
} else {
DUK_DD(DUK_DDPRINT("sweep; reachable, finalized --> rescued after finalization: %p", (void *) curr));
#if defined(DUK_USE_FINALIZER_SUPPORT)
DUK_HEAPHDR_CLEAR_FINALIZED(curr);
#endif
#if defined(DUK_USE_DEBUG)
count_rescue++;
#endif
}
} else {
DUK_DD(DUK_DDPRINT("sweep; reachable --> keep: %!iO", curr));
count_keep++;
}
if (prev != NULL) {
DUK_ASSERT(heap->heap_allocated != NULL);
DUK_HEAPHDR_SET_NEXT(heap, prev, curr);
} else {
DUK_ASSERT(heap->heap_allocated == NULL);
heap->heap_allocated = curr;
}
#if defined(DUK_USE_DOUBLE_LINKED_HEAP)
DUK_HEAPHDR_SET_PREV(heap, curr, prev);
#endif
DUK_HEAPHDR_ASSERT_LINKS(heap, prev);
DUK_HEAPHDR_ASSERT_LINKS(heap, curr);
prev = curr;
}
/*
* Shrink check for value stacks here. We're inside
* ms_prevent_count protection which prevents recursive
* mark-and-sweep and refzero finalizers, so there are
* no side effects that would affect the heap lists.
*/
if (DUK_HEAPHDR_IS_OBJECT(curr) && DUK_HOBJECT_IS_THREAD((duk_hobject *) curr)) {
duk_hthread *thr_curr = (duk_hthread *) curr;
DUK_DD(DUK_DDPRINT("value stack shrink check for thread: %!O", curr));
duk_valstack_shrink_check_nothrow(thr_curr, flags & DUK_MS_FLAG_EMERGENCY /*snug*/);
}
DUK_HEAPHDR_CLEAR_REACHABLE(curr);
/* Keep FINALIZED if set, used if rescue decisions are postponed. */
/* Keep FINALIZABLE for objects on finalize_list. */
DUK_ASSERT(!DUK_HEAPHDR_HAS_REACHABLE(curr));
} else {
/*
* Unreachable object:
* - If FINALIZED, object was finalized but not
* rescued. This doesn't affect freeing.
* - Otherwise normal unreachable object.
*
* There's no guard preventing a FINALIZED object
* from being freed while finalizers execute: the
* artificial finalize_list reachability roots can't
* cause an incorrect free decision (but can cause
* an incorrect rescue decision).
*/
#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 defined(DUK_USE_DEBUG)
if (DUK_HEAPHDR_HAS_FINALIZED(curr)) {
DUK_DD(DUK_DDPRINT("sweep; unreachable, finalized --> finalized object not rescued: %p", (void *) curr));
} else {
DUK_DD(DUK_DDPRINT("sweep; not reachable --> free: %p", (void *) curr));
}
#endif
/* 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 != NULL) {
DUK_HEAPHDR_SET_NEXT(heap, prev, NULL);
}
DUK_HEAPHDR_ASSERT_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;
}
/*
* Litcache helpers.
*/
#if defined(DUK_USE_LITCACHE_SIZE)
DUK_LOCAL void duk__wipe_litcache(duk_heap *heap) {
duk_uint_t i;
duk_litcache_entry *e;
e = heap->litcache;
for (i = 0; i < DUK_USE_LITCACHE_SIZE; i++) {
e->addr = NULL;
/* e->h does not need to be invalidated: when e->addr is
* NULL, e->h is considered garbage.
*/
e++;
}
}
#endif /* DUK_USE_LITCACHE_SIZE */
/*
* Object compaction.
*
* Compaction is assumed to never throw an error.
*/
DUK_LOCAL int duk__protected_compact_object(duk_hthread *thr, void *udata) {
duk_hobject *obj;
/* XXX: for threads, compact stacks? */
DUK_UNREF(udata);
obj = duk_known_hobject(thr, -1);
duk_hobject_compact_props(thr, obj);
return 0;
}
#if defined(DUK_USE_DEBUG)
DUK_LOCAL void duk__compact_object_list(duk_heap *heap, duk_hthread *thr, duk_heaphdr *start, duk_size_t *p_count_check, duk_size_t *p_count_compact, duk_size_t *p_count_bytes_saved) {
#else
DUK_LOCAL void duk__compact_object_list(duk_heap *heap, duk_hthread *thr, duk_heaphdr *start) {
#endif
duk_heaphdr *curr;
#if defined(DUK_USE_DEBUG)
duk_size_t old_size, new_size;
#endif
duk_hobject *obj;
DUK_UNREF(heap);
curr = start;
while (curr) {
DUK_DDD(DUK_DDDPRINT("mark-and-sweep compact: %p", (void *) curr));
if (DUK_HEAPHDR_GET_TYPE(curr) != DUK_HTYPE_OBJECT) {
goto next;
}
obj = (duk_hobject *) curr;
#if defined(DUK_USE_DEBUG)
old_size = DUK_HOBJECT_P_COMPUTE_SIZE(DUK_HOBJECT_GET_ESIZE(obj),
DUK_HOBJECT_GET_ASIZE(obj),
DUK_HOBJECT_GET_HSIZE(obj));
#endif
DUK_DD(DUK_DDPRINT("compact object: %p", (void *) obj));
duk_push_hobject(thr, obj);
/* XXX: disable error handlers for duration of compaction? */
duk_safe_call(thr, duk__protected_compact_object, NULL, 1, 0);
#if defined(DUK_USE_DEBUG)
new_size = DUK_HOBJECT_P_COMPUTE_SIZE(DUK_HOBJECT_GET_ESIZE(obj),
DUK_HOBJECT_GET_ASIZE(obj),
DUK_HOBJECT_GET_HSIZE(obj));
#endif
#if defined(DUK_USE_DEBUG)
(*p_count_compact)++;
(*p_count_bytes_saved) += (duk_size_t) (old_size - new_size);
#endif
next:
curr = DUK_HEAPHDR_GET_NEXT(heap, curr);
#if defined(DUK_USE_DEBUG)
(*p_count_check)++;
#endif
}
}
DUK_LOCAL void duk__compact_objects(duk_heap *heap) {
/* XXX: which lists should participate? to be finalized? */
#if defined(DUK_USE_DEBUG)
duk_size_t count_check = 0;
duk_size_t count_compact = 0;
duk_size_t count_bytes_saved = 0;
#endif
DUK_DD(DUK_DDPRINT("duk__compact_objects: %p", (void *) heap));
DUK_ASSERT(heap->heap_thread != NULL);
#if defined(DUK_USE_DEBUG)
duk__compact_object_list(heap, heap->heap_thread, heap->heap_allocated, &count_check, &count_compact, &count_bytes_saved);
#if defined(DUK_USE_FINALIZER_SUPPORT)
duk__compact_object_list(heap, heap->heap_thread, heap->finalize_list, &count_check, &count_compact, &count_bytes_saved);
#endif
#else
duk__compact_object_list(heap, heap->heap_thread, heap->heap_allocated);
#if defined(DUK_USE_FINALIZER_SUPPORT)
duk__compact_object_list(heap, heap->heap_thread, heap->finalize_list);
#endif
#endif
#if defined(DUK_USE_REFERENCE_COUNTING)
DUK_ASSERT(heap->refzero_list == NULL); /* Always handled to completion inline in DECREF. */
#endif
#if defined(DUK_USE_DEBUG)
DUK_D(DUK_DPRINT("mark-and-sweep compact objects: %ld checked, %ld compaction attempts, %ld bytes saved by compaction",
(long) count_check, (long) count_compact, (long) count_bytes_saved));
#endif
}
/*
* Assertion helpers.
*/
#if defined(DUK_USE_ASSERTIONS)
typedef void (*duk__gc_heaphdr_assert)(duk_heap *heap, duk_heaphdr *h);
typedef void (*duk__gc_hstring_assert)(duk_heap *heap, duk_hstring *h);
DUK_LOCAL void duk__assert_walk_list(duk_heap *heap, duk_heaphdr *start, duk__gc_heaphdr_assert func) {
duk_heaphdr *curr;
for (curr = start; curr != NULL; curr = DUK_HEAPHDR_GET_NEXT(heap, curr)) {
func(heap, curr);
}
}
DUK_LOCAL void duk__assert_walk_strtable(duk_heap *heap, duk__gc_hstring_assert func) {
duk_uint32_t i;
for (i = 0; i < heap->st_size; i++) {
duk_hstring *h;
#if defined(DUK_USE_STRTAB_PTRCOMP)
h = DUK_USE_HEAPPTR_DEC16(heap->heap_udata, heap->strtable16[i]);
#else
h = heap->strtable[i];
#endif
while (h != NULL) {
func(heap, h);
h = h->hdr.h_next;
}
}
}
DUK_LOCAL void duk__assert_heaphdr_flags_cb(duk_heap *heap, duk_heaphdr *h) {
DUK_UNREF(heap);
DUK_ASSERT(!DUK_HEAPHDR_HAS_REACHABLE(h));
DUK_ASSERT(!DUK_HEAPHDR_HAS_TEMPROOT(h));
DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZABLE(h));
/* may have FINALIZED */
}
DUK_LOCAL void duk__assert_heaphdr_flags(duk_heap *heap) {
duk__assert_walk_list(heap, heap->heap_allocated, duk__assert_heaphdr_flags_cb);
#if defined(DUK_USE_REFERENCE_COUNTING)
DUK_ASSERT(heap->refzero_list == NULL); /* Always handled to completion inline in DECREF. */
#endif
/* XXX: Assertions for finalize_list? */
}
DUK_LOCAL void duk__assert_validity_cb1(duk_heap *heap, duk_heaphdr *h) {
DUK_UNREF(heap);
DUK_ASSERT(DUK_HEAPHDR_IS_OBJECT(h) || DUK_HEAPHDR_IS_BUFFER(h));
duk_heaphdr_assert_valid_subclassed(h);
}
DUK_LOCAL void duk__assert_validity_cb2(duk_heap *heap, duk_hstring *h) {
DUK_UNREF(heap);
DUK_ASSERT(DUK_HEAPHDR_IS_STRING((duk_heaphdr *) h));
duk_heaphdr_assert_valid_subclassed((duk_heaphdr *) h);
}
DUK_LOCAL void duk__assert_validity(duk_heap *heap) {
duk__assert_walk_list(heap, heap->heap_allocated, duk__assert_validity_cb1);
#if defined(DUK_USE_FINALIZER_SUPPORT)
duk__assert_walk_list(heap, heap->finalize_list, duk__assert_validity_cb1);
#endif
#if defined(DUK_USE_REFERENCE_COUNTING)
duk__assert_walk_list(heap, heap->refzero_list, duk__assert_validity_cb1);
#endif
duk__assert_walk_strtable(heap, duk__assert_validity_cb2);
}
#if defined(DUK_USE_REFERENCE_COUNTING)
DUK_LOCAL void duk__assert_valid_refcounts_cb(duk_heap *heap, duk_heaphdr *h) {
/* Cannot really assert much w.r.t. refcounts now. */
DUK_UNREF(heap);
if (DUK_HEAPHDR_GET_REFCOUNT(h) == 0 &&
DUK_HEAPHDR_HAS_FINALIZED(h)) {
/* 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.
* (This doesn't currently happen however.)
*/
} else if (DUK_HEAPHDR_GET_REFCOUNT(h) == 0) {
/* An object may be in heap_allocated list with a zero
* refcount also if it is a temporary object created
* during debugger paused state. It will get collected
* by mark-and-sweep based on its reachability status
* (presumably not reachable because refcount is 0).
*/
}
DUK_ASSERT_DISABLE(DUK_HEAPHDR_GET_REFCOUNT(h) >= 0); /* Unsigned. */
}
DUK_LOCAL void duk__assert_valid_refcounts(duk_heap *heap) {
duk__assert_walk_list(heap, heap->heap_allocated, duk__assert_valid_refcounts_cb);
}
DUK_LOCAL void duk__clear_assert_refcounts_cb1(duk_heap *heap, duk_heaphdr *h) {
DUK_UNREF(heap);
h->h_assert_refcount = 0;
}
DUK_LOCAL void duk__clear_assert_refcounts_cb2(duk_heap *heap, duk_hstring *h) {
DUK_UNREF(heap);
((duk_heaphdr *) h)->h_assert_refcount = 0;
}
DUK_LOCAL void duk__clear_assert_refcounts(duk_heap *heap) {
duk__assert_walk_list(heap, heap->heap_allocated, duk__clear_assert_refcounts_cb1);
#if defined(DUK_USE_FINALIZER_SUPPORT)
duk__assert_walk_list(heap, heap->finalize_list, duk__clear_assert_refcounts_cb1);
#endif
#if defined(DUK_USE_REFERENCE_COUNTING)
duk__assert_walk_list(heap, heap->refzero_list, duk__clear_assert_refcounts_cb1);
#endif
duk__assert_walk_strtable(heap, duk__clear_assert_refcounts_cb2);
}
DUK_LOCAL void duk__check_refcount_heaphdr(duk_heaphdr *hdr) {
duk_bool_t count_ok;
duk_size_t expect_refc;
/* The refcount check only makes sense for reachable objects on
* heap_allocated or string table, after the sweep phase. Prior to
* sweep phase refcounts will include references that are not visible
* via reachability roots.
*
* Because we're called after the sweep phase, all heap objects on
* heap_allocated are reachable. REACHABLE flags have already been
* cleared so we can't check them.
*/
/* ROM objects have intentionally incorrect refcount (1), but we won't
* check them.
*/
DUK_ASSERT(!DUK_HEAPHDR_HAS_READONLY(hdr));
expect_refc = hdr->h_assert_refcount;
if (DUK_HEAPHDR_IS_STRING(hdr) && DUK_HSTRING_HAS_PINNED_LITERAL((duk_hstring *) hdr)) {
expect_refc++;
}
count_ok = ((duk_size_t) DUK_HEAPHDR_GET_REFCOUNT(hdr) == expect_refc);
if (!count_ok) {
DUK_D(DUK_DPRINT("refcount mismatch for: %p: header=%ld counted=%ld --> %!iO",
(void *) hdr, (long) DUK_HEAPHDR_GET_REFCOUNT(hdr),
(long) hdr->h_assert_refcount, hdr));
DUK_ASSERT(0);
}
}
DUK_LOCAL void duk__check_assert_refcounts_cb1(duk_heap *heap, duk_heaphdr *h) {
DUK_UNREF(heap);
duk__check_refcount_heaphdr(h);
}
DUK_LOCAL void duk__check_assert_refcounts_cb2(duk_heap *heap, duk_hstring *h) {
DUK_UNREF(heap);
duk__check_refcount_heaphdr((duk_heaphdr *) h);
}
DUK_LOCAL void duk__check_assert_refcounts(duk_heap *heap) {
duk__assert_walk_list(heap, heap->heap_allocated, duk__check_assert_refcounts_cb1);
#if defined(DUK_USE_FINALIZER_SUPPORT)
duk__assert_walk_list(heap, heap->finalize_list, duk__check_assert_refcounts_cb1);
#endif
/* XXX: Assert anything for refzero_list? */
duk__assert_walk_strtable(heap, duk__check_assert_refcounts_cb2);
}
#endif /* DUK_USE_REFERENCE_COUNTING */
#if defined(DUK_USE_LITCACHE_SIZE)
DUK_LOCAL void duk__assert_litcache_nulls(duk_heap *heap) {
duk_uint_t i;
duk_litcache_entry *e;
e = heap->litcache;
for (i = 0; i < DUK_USE_LITCACHE_SIZE; i++) {
/* Entry addresses were NULLed before mark-and-sweep, check
* that they're still NULL afterwards to ensure no pointers
* were recorded through any side effects.
*/
DUK_ASSERT(e->addr == NULL);
}
}
#endif /* DUK_USE_LITCACHE_SIZE */
#endif /* DUK_USE_ASSERTIONS */
/*
* Stats dump.
*/
#if defined(DUK_USE_DEBUG)
DUK_LOCAL void duk__dump_stats(duk_heap *heap) {
DUK_D(DUK_DPRINT("stats executor: opcodes=%ld, interrupt=%ld, throw=%ld",
(long) heap->stats_exec_opcodes, (long) heap->stats_exec_interrupt,
(long) heap->stats_exec_throw));
DUK_D(DUK_DPRINT("stats call: all=%ld, tailcall=%ld, ecmatoecma=%ld",
(long) heap->stats_call_all, (long) heap->stats_call_tailcall,
(long) heap->stats_call_ecmatoecma));
DUK_D(DUK_DPRINT("stats safecall: all=%ld, nothrow=%ld, throw=%ld",
(long) heap->stats_safecall_all, (long) heap->stats_safecall_nothrow,
(long) heap->stats_safecall_throw));
DUK_D(DUK_DPRINT("stats mark-and-sweep: try_count=%ld, skip_count=%ld, emergency_count=%ld",
(long) heap->stats_ms_try_count, (long) heap->stats_ms_skip_count,
(long) heap->stats_ms_emergency_count));
DUK_D(DUK_DPRINT("stats stringtable: intern_hit=%ld, intern_miss=%ld, "
"resize_check=%ld, resize_grow=%ld, resize_shrink=%ld, "
"litcache_hit=%ld, litcache_miss=%ld, litcache_pin=%ld",
(long) heap->stats_strtab_intern_hit, (long) heap->stats_strtab_intern_miss,
(long) heap->stats_strtab_resize_check, (long) heap->stats_strtab_resize_grow,
(long) heap->stats_strtab_resize_shrink, (long) heap->stats_strtab_litcache_hit,
(long) heap->stats_strtab_litcache_miss, (long) heap->stats_strtab_litcache_pin));
DUK_D(DUK_DPRINT("stats object: realloc_props=%ld, abandon_array=%ld",
(long) heap->stats_object_realloc_props, (long) heap->stats_object_abandon_array));
DUK_D(DUK_DPRINT("stats getownpropdesc: count=%ld, hit=%ld, miss=%ld",
(long) heap->stats_getownpropdesc_count, (long) heap->stats_getownpropdesc_hit,
(long) heap->stats_getownpropdesc_miss));
DUK_D(DUK_DPRINT("stats getpropdesc: count=%ld, hit=%ld, miss=%ld",
(long) heap->stats_getpropdesc_count, (long) heap->stats_getpropdesc_hit,
(long) heap->stats_getpropdesc_miss));
DUK_D(DUK_DPRINT("stats getprop: all=%ld, arrayidx=%ld, bufobjidx=%ld, "
"bufferidx=%ld, bufferlen=%ld, stringidx=%ld, stringlen=%ld, "
"proxy=%ld, arguments=%ld",
(long) heap->stats_getprop_all, (long) heap->stats_getprop_arrayidx,
(long) heap->stats_getprop_bufobjidx, (long) heap->stats_getprop_bufferidx,
(long) heap->stats_getprop_bufferlen, (long) heap->stats_getprop_stringidx,
(long) heap->stats_getprop_stringlen, (long) heap->stats_getprop_proxy,
(long) heap->stats_getprop_arguments));
DUK_D(DUK_DPRINT("stats putprop: all=%ld, arrayidx=%ld, bufobjidx=%ld, "
"bufferidx=%ld, proxy=%ld",
(long) heap->stats_putprop_all, (long) heap->stats_putprop_arrayidx,
(long) heap->stats_putprop_bufobjidx, (long) heap->stats_putprop_bufferidx,
(long) heap->stats_putprop_proxy));
DUK_D(DUK_DPRINT("stats getvar: all=%ld",
(long) heap->stats_getvar_all));
DUK_D(DUK_DPRINT("stats putvar: all=%ld",
(long) heap->stats_putvar_all));
DUK_D(DUK_DPRINT("stats envrec: delayedcreate=%ld, create=%ld, newenv=%ld, oldenv=%ld, pushclosure=%ld",
(long) heap->stats_envrec_delayedcreate,
(long) heap->stats_envrec_create,
(long) heap->stats_envrec_newenv,
(long) heap->stats_envrec_oldenv,
(long) heap->stats_envrec_pushclosure));
}
#endif /* DUK_USE_DEBUG */
/*
* Main mark-and-sweep function.
*
* 'flags' represents the features requested by the caller. The current
* heap->ms_base_flags is ORed automatically into the flags; the base flags
* mask typically prevents certain mark-and-sweep operation to avoid trouble.
*/
DUK_INTERNAL void duk_heap_mark_and_sweep(duk_heap *heap, duk_small_uint_t flags) {
duk_size_t count_keep_obj;
duk_size_t count_keep_str;
#if defined(DUK_USE_VOLUNTARY_GC)
duk_size_t tmp;
#endif
DUK_STATS_INC(heap, stats_ms_try_count);
#if defined(DUK_USE_DEBUG)
if (flags & DUK_MS_FLAG_EMERGENCY) {
DUK_STATS_INC(heap, stats_ms_emergency_count);
}
#endif
/* If debugger is paused, garbage collection is disabled by default.
* This is achieved by bumping ms_prevent_count when becoming paused.
*/
DUK_ASSERT(!DUK_HEAP_HAS_DEBUGGER_PAUSED(heap) || heap->ms_prevent_count > 0);
/* Prevention/recursion check as soon as possible because we may
* be called a number of times when voluntary mark-and-sweep is
* pending.
*/
if (heap->ms_prevent_count != 0) {
DUK_DD(DUK_DDPRINT("reject recursive mark-and-sweep"));
DUK_STATS_INC(heap, stats_ms_skip_count);
return;
}
DUK_ASSERT(heap->ms_running == 0); /* ms_prevent_count is bumped when ms_running is set */
/* Heap_thread is used during mark-and-sweep for refcount finalization
* (it's also used for finalizer execution once mark-and-sweep is
* complete). Heap allocation code ensures heap_thread is set and
* properly initialized before setting ms_prevent_count to 0.
*/
DUK_ASSERT(heap->heap_thread != NULL);
DUK_ASSERT(heap->heap_thread->valstack != NULL);
DUK_D(DUK_DPRINT("garbage collect (mark-and-sweep) starting, requested flags: 0x%08lx, effective flags: 0x%08lx",
(unsigned long) flags, (unsigned long) (flags | heap->ms_base_flags)));
flags |= heap->ms_base_flags;
#if defined(DUK_USE_FINALIZER_SUPPORT)
if (heap->finalize_list != NULL) {
flags |= DUK_MS_FLAG_POSTPONE_RESCUE;
}
#endif
/*
* Assertions before
*/
#if defined(DUK_USE_ASSERTIONS)
DUK_ASSERT(heap->ms_prevent_count == 0);
DUK_ASSERT(heap->ms_running == 0);
DUK_ASSERT(!DUK_HEAP_HAS_DEBUGGER_PAUSED(heap));
DUK_ASSERT(!DUK_HEAP_HAS_MARKANDSWEEP_RECLIMIT_REACHED(heap));
DUK_ASSERT(heap->ms_recursion_depth == 0);
duk__assert_heaphdr_flags(heap);
duk__assert_validity(heap);
#if defined(DUK_USE_REFERENCE_COUNTING)
/* Note: heap->refzero_free_running may be true; a refcount
* finalizer may trigger a mark-and-sweep.
*/
duk__assert_valid_refcounts(heap);
#endif /* DUK_USE_REFERENCE_COUNTING */
#endif /* DUK_USE_ASSERTIONS */
/*
* Begin
*/
DUK_ASSERT(heap->ms_prevent_count == 0);
DUK_ASSERT(heap->ms_running == 0);
heap->ms_prevent_count = 1;
heap->ms_running = 1;
/*
* Free activation/catcher freelists on every mark-and-sweep for now.
* This is an initial rough draft; ideally we'd keep count of the
* freelist size and free only excess entries.
*/
DUK_D(DUK_DPRINT("freeing temporary freelists"));
duk_heap_free_freelists(heap);
/*
* Mark roots, hoping that recursion limit is not normally hit.
* If recursion limit is hit, run additional reachability rounds
* starting from "temproots" until marking is complete.
*
* Marking happens in two phases: first we mark actual reachability
* roots (and run "temproots" to complete the process). Then we
* check which objects are unreachable and are finalizable; such
* objects are marked as FINALIZABLE and marked as reachability
* (and "temproots" is run again to complete the process).
*
* The heap finalize_list must also be marked as a reachability root.
* There may be objects on the list from a previous round if the
* previous run had finalizer skip flag.
*/
#if defined(DUK_USE_ASSERTIONS) && defined(DUK_USE_REFERENCE_COUNTING)
duk__clear_assert_refcounts(heap);
#endif
#if defined(DUK_USE_LITCACHE_SIZE)
duk__wipe_litcache(heap);
#endif
duk__mark_roots_heap(heap); /* Mark main reachability roots. */
#if defined(DUK_USE_REFERENCE_COUNTING)
DUK_ASSERT(heap->refzero_list == NULL); /* Always handled to completion inline in DECREF. */
#endif
duk__mark_temproots_by_heap_scan(heap); /* Temproots. */
#if defined(DUK_USE_FINALIZER_SUPPORT)
duk__mark_finalizable(heap); /* Mark finalizable as reachability roots. */
duk__mark_finalize_list(heap); /* Mark finalizer work list as reachability roots. */
#endif
duk__mark_temproots_by_heap_scan(heap); /* Temproots. */
/*
* Sweep garbage and remove marking flags, and move objects with
* finalizers to the finalizer work list.
*
* Objects to be swept need to get their refcounts finalized before
* they are swept. In other words, their target object refcounts
* need to be decreased. This has to be done before freeing any
* objects to avoid decref'ing dangling pointers (which may happen
* even without bugs, e.g. with reference loops)
*
* Because strings don't point to other heap objects, similar
* finalization is not necessary for strings.
*/
/* XXX: more emergency behavior, e.g. find smaller hash sizes etc */
#if defined(DUK_USE_REFERENCE_COUNTING)
duk__finalize_refcounts(heap);
#endif
duk__sweep_heap(heap, flags, &count_keep_obj);
duk__sweep_stringtable(heap, &count_keep_str);
#if defined(DUK_USE_ASSERTIONS) && defined(DUK_USE_REFERENCE_COUNTING)
duk__check_assert_refcounts(heap);
#endif
#if defined(DUK_USE_REFERENCE_COUNTING)
DUK_ASSERT(heap->refzero_list == NULL); /* Always handled to completion inline in DECREF. */
#endif
#if defined(DUK_USE_FINALIZER_SUPPORT)
duk__clear_finalize_list_flags(heap);
#endif
/*
* Object compaction (emergency only).
*
* Object compaction is a separate step after sweeping, as there is
* more free memory for it to work with. Also, currently compaction
* may insert new objects into the heap allocated list and the string
* table which we don't want to do during a sweep (the reachability
* flags of such objects would be incorrect). The objects inserted
* are currently:
*
* - a temporary duk_hbuffer for a new properties allocation
* - if array part is abandoned, string keys are interned
*
* The object insertions go to the front of the list, so they do not
* cause an infinite loop (they are not compacted).
*
* At present compaction is not allowed when mark-and-sweep runs
* during error handling because it involves a duk_safe_call()
* interfering with error state.
*/
if ((flags & DUK_MS_FLAG_EMERGENCY) &&
!(flags & DUK_MS_FLAG_NO_OBJECT_COMPACTION)) {
if (heap->lj.type != DUK_LJ_TYPE_UNKNOWN) {
DUK_D(DUK_DPRINT("lj.type (%ld) not DUK_LJ_TYPE_UNKNOWN, skip object compaction", (long) heap->lj.type));
} else {
DUK_D(DUK_DPRINT("object compaction"));
duk__compact_objects(heap);
}
}
/*
* String table resize check.
*
* This is mainly useful in emergency GC: if the string table load
* factor is really low for some reason, we can shrink the string
* table to a smaller size and free some memory in the process.
* Only execute in emergency GC. String table has internal flags
* to protect against recursive resizing if this mark-and-sweep pass
* was triggered by a string table resize.
*/
if (flags & DUK_MS_FLAG_EMERGENCY) {
DUK_D(DUK_DPRINT("stringtable resize check in emergency gc"));
duk_heap_strtable_force_resize(heap);
}
/*
* Finish
*/
DUK_ASSERT(heap->ms_prevent_count == 1);
DUK_ASSERT(heap->ms_running == 1);
heap->ms_prevent_count = 0;
heap->ms_running = 0;
/*
* Assertions after
*/
#if defined(DUK_USE_ASSERTIONS)
DUK_ASSERT(heap->ms_prevent_count == 0);
DUK_ASSERT(!DUK_HEAP_HAS_MARKANDSWEEP_RECLIMIT_REACHED(heap));
DUK_ASSERT(heap->ms_recursion_depth == 0);
duk__assert_heaphdr_flags(heap);
duk__assert_validity(heap);
#if defined(DUK_USE_REFERENCE_COUNTING)
/* Note: heap->refzero_free_running may be true; a refcount
* finalizer may trigger a mark-and-sweep.
*/
duk__assert_valid_refcounts(heap);
#endif /* DUK_USE_REFERENCE_COUNTING */
#if defined(DUK_USE_LITCACHE_SIZE)
duk__assert_litcache_nulls(heap);
#endif /* DUK_USE_LITCACHE_SIZE */
#endif /* DUK_USE_ASSERTIONS */
/*
* Reset trigger counter
*/
#if defined(DUK_USE_VOLUNTARY_GC)
tmp = (count_keep_obj + count_keep_str) / 256;
heap->ms_trigger_counter = (duk_int_t) (
(tmp * DUK_HEAP_MARK_AND_SWEEP_TRIGGER_MULT) +
DUK_HEAP_MARK_AND_SWEEP_TRIGGER_ADD);
DUK_D(DUK_DPRINT("garbage collect (mark-and-sweep) finished: %ld objects kept, %ld strings kept, trigger reset to %ld",
(long) count_keep_obj, (long) count_keep_str, (long) heap->ms_trigger_counter));
#else
DUK_D(DUK_DPRINT("garbage collect (mark-and-sweep) finished: %ld objects kept, %ld strings kept, no voluntary trigger",
(long) count_keep_obj, (long) count_keep_str));
#endif
/*
* Stats dump
*/
#if defined(DUK_USE_DEBUG)
duk__dump_stats(heap);
#endif
/*
* Finalize objects in the finalization work list. Finalized
* objects are queued back to heap_allocated with FINALIZED set.
*
* Since finalizers may cause arbitrary side effects, they are
* prevented e.g. during string table and object property allocation
* resizing using heap->pf_prevent_count. In this case the objects
* remain in the finalization work list after mark-and-sweep exits
* and they may be finalized on the next pass or any DECREF checking
* for finalize_list.
*
* As of Duktape 2.1 finalization happens outside mark-and-sweep
* protection. Mark-and-sweep is allowed while the finalize_list
* is being processed, but no rescue decisions are done while the
* process is on-going. This avoids incorrect rescue decisions
* if an object is considered reachable (and thus rescued) because
* of a reference via finalize_list (which is considered a reachability
* root). When finalize_list is being processed, reachable objects
* with FINALIZED set will just keep their FINALIZED flag for later
* mark-and-sweep processing.
*
* This could also be handled (a bit better) by having a more refined
* notion of reachability for rescue/free decisions.
*
* XXX: avoid finalizer execution when doing emergency GC?
*/
#if defined(DUK_USE_FINALIZER_SUPPORT)
/* Attempt to process finalize_list, pf_prevent_count check
* is inside the target.
*/
duk_heap_process_finalize_list(heap);
#endif /* DUK_USE_FINALIZER_SUPPORT */
}
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