diff options
Diffstat (limited to 'src/civetweb/src/third_party/duktape-1.8.0/src-separate/duk_heap_markandsweep.c')
| -rw-r--r-- | src/civetweb/src/third_party/duktape-1.8.0/src-separate/duk_heap_markandsweep.c | 1440 |
1 files changed, 1440 insertions, 0 deletions
diff --git a/src/civetweb/src/third_party/duktape-1.8.0/src-separate/duk_heap_markandsweep.c b/src/civetweb/src/third_party/duktape-1.8.0/src-separate/duk_heap_markandsweep.c new file mode 100644 index 000000000..348c93e8f --- /dev/null +++ b/src/civetweb/src/third_party/duktape-1.8.0/src-separate/duk_heap_markandsweep.c @@ -0,0 +1,1440 @@ +/* + * Mark-and-sweep garbage collection. + */ + +#include "duk_internal.h" + +#ifdef DUK_USE_MARK_AND_SWEEP + +DUK_LOCAL_DECL void duk__mark_heaphdr(duk_heap *heap, duk_heaphdr *h); +DUK_LOCAL_DECL void duk__mark_tval(duk_heap *heap, duk_tval *tv); + +/* + * Misc + */ + +/* Select a thread for mark-and-sweep use. + * + * XXX: This needs to change later. + */ +DUK_LOCAL duk_hthread *duk__get_temp_hthread(duk_heap *heap) { + if (heap->curr_thread) { + return heap->curr_thread; + } + return heap->heap_thread; /* may be NULL, too */ +} + +/* + * 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); + + /* 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); + + /* 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) { + continue; + } + duk__mark_heaphdr(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)); + + if (DUK_HOBJECT_IS_COMPILEDFUNCTION(h)) { + duk_hcompiledfunction *f = (duk_hcompiledfunction *) h; + duk_tval *tv, *tv_end; + duk_hobject **fn, **fn_end; + + /* 'data' is reachable through every compiled function which + * contains a reference. + */ + + duk__mark_heaphdr(heap, (duk_heaphdr *) DUK_HCOMPILEDFUNCTION_GET_DATA(heap, f)); + + if (DUK_HCOMPILEDFUNCTION_GET_DATA(heap, f) != NULL) { + tv = DUK_HCOMPILEDFUNCTION_GET_CONSTS_BASE(heap, f); + tv_end = DUK_HCOMPILEDFUNCTION_GET_CONSTS_END(heap, f); + while (tv < tv_end) { + duk__mark_tval(heap, tv); + tv++; + } + + fn = DUK_HCOMPILEDFUNCTION_GET_FUNCS_BASE(heap, f); + fn_end = DUK_HCOMPILEDFUNCTION_GET_FUNCS_END(heap, f); + while (fn < fn_end) { + duk__mark_heaphdr(heap, (duk_heaphdr *) *fn); + fn++; + } + } else { + /* May happen in some out-of-memory corner cases. */ + DUK_D(DUK_DPRINT("duk_hcompiledfunction 'data' is NULL, skipping marking")); + } + } else if (DUK_HOBJECT_IS_NATIVEFUNCTION(h)) { + duk_hnativefunction *f = (duk_hnativefunction *) h; + DUK_UNREF(f); + /* nothing to mark */ + } else if (DUK_HOBJECT_IS_BUFFEROBJECT(h)) { + duk_hbufferobject *b = (duk_hbufferobject *) h; + duk__mark_heaphdr(heap, (duk_heaphdr *) b->buf); + } else if (DUK_HOBJECT_IS_THREAD(h)) { + duk_hthread *t = (duk_hthread *) h; + duk_tval *tv; + + tv = t->valstack; + while (tv < t->valstack_top) { + duk__mark_tval(heap, tv); + tv++; + } + + for (i = 0; i < (duk_uint_fast32_t) t->callstack_top; i++) { + duk_activation *act = t->callstack + i; + 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); +#ifdef DUK_USE_NONSTD_FUNC_CALLER_PROPERTY + duk__mark_heaphdr(heap, (duk_heaphdr *) act->prev_caller); +#endif + } + +#if 0 /* nothing now */ + for (i = 0; i < (duk_uint_fast32_t) t->catchstack_top; i++) { + duk_catcher *cat = t->catchstack + i; + } +#endif + + duk__mark_heaphdr(heap, (duk_heaphdr *) t->resumer); + + /* XXX: duk_small_uint_t would be enough for this loop */ + for (i = 0; i < DUK_NUM_BUILTINS; i++) { + duk__mark_heaphdr(heap, (duk_heaphdr *) t->builtins[i]); + } + } +} + +/* recursion tracking happens here only */ +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))); + if (!h) { + return; + } +#if defined(DUK_USE_ROM_OBJECTS) + if (DUK_HEAPHDR_HAS_READONLY(h)) { + DUK_DDD(DUK_DDDPRINT("readonly object %p, skip", (void *) h)); + return; + } +#endif + if (DUK_HEAPHDR_HAS_REACHABLE(h)) { + DUK_DDD(DUK_DDDPRINT("already marked reachable, skip")); + return; + } + DUK_HEAPHDR_SET_REACHABLE(h); + + if (heap->mark_and_sweep_recursion_depth >= DUK_USE_MARK_AND_SWEEP_RECLIMIT) { + /* log this with a normal debug level because this should be relatively rare */ + 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->mark_and_sweep_recursion_depth++; + + switch ((int) 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(); + } + + heap->mark_and_sweep_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) { + return; + } + if (DUK_TVAL_IS_HEAP_ALLOCATED(tv)) { + duk__mark_heaphdr(heap, DUK_TVAL_GET_HEAPHDR(tv)); + } +} + +/* + * 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 refzero_list objects. + * + * Objects on the refzero_list have no inbound references. They might have + * outbound references to objects that we might free, which would invalidate + * any references held by the refzero objects. A refzero object might also + * be rescued by refcount finalization. Refzero objects are treated as + * reachability roots to ensure they (or anything they point to) are not + * freed in mark-and-sweep. + */ + +#ifdef DUK_USE_REFERENCE_COUNTING +DUK_LOCAL void duk__mark_refzero_list(duk_heap *heap) { + duk_heaphdr *hdr; + + DUK_DD(DUK_DDPRINT("duk__mark_refzero_list: %p", (void *) heap)); + + hdr = heap->refzero_list; + while (hdr) { + duk__mark_heaphdr(heap, hdr); + hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr); + } +} +#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 (refzero_list is thus excluded). + * + * Objects are first marked FINALIZABLE and only then marked as reachability + * roots; otherwise circular references might be handled inconsistently. + */ + +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. */ +} + +/* + * Mark objects on finalize_list. + * + */ + +DUK_LOCAL void duk__mark_finalize_list(duk_heap *heap) { + duk_heaphdr *hdr; +#ifdef 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) { + duk__mark_heaphdr(heap, hdr); + hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr); +#ifdef DUK_USE_DEBUG + count_finalize_list++; +#endif + } + +#ifdef 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 +} + +/* + * Fallback marking handler if recursion limit is reached. + * + * Iterates 'temproots' until recursion limit is no longer hit. Note + * that temproots may reside either in heap allocated list or the + * refzero work list. 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. + */ + +#ifdef 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 + 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 */ + duk__mark_heaphdr(heap, hdr); + +#ifdef DUK_USE_DEBUG + (*count)++; +#endif +} + +DUK_LOCAL void duk__mark_temproots_by_heap_scan(duk_heap *heap) { + duk_heaphdr *hdr; +#ifdef 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")); + +#ifdef DUK_USE_DEBUG + count = 0; +#endif + DUK_HEAP_CLEAR_MARKANDSWEEP_RECLIMIT_REACHED(heap); + + hdr = heap->heap_allocated; + while (hdr) { +#ifdef DUK_USE_DEBUG + duk__handle_temproot(heap, hdr, &count); +#else + duk__handle_temproot(heap, hdr); +#endif + hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr); + } + + /* must also check refzero_list */ +#ifdef DUK_USE_REFERENCE_COUNTING + hdr = heap->refzero_list; + while (hdr) { +#ifdef DUK_USE_DEBUG + duk__handle_temproot(heap, hdr, &count); +#else + duk__handle_temproot(heap, hdr); +#endif + hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr); + } +#endif /* DUK_USE_REFERENCE_COUNTING */ + +#ifdef 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(). + */ + +#ifdef DUK_USE_REFERENCE_COUNTING +DUK_LOCAL void duk__finalize_refcounts(duk_heap *heap) { + duk_hthread *thr; + duk_heaphdr *hdr; + + thr = duk__get_temp_hthread(heap); + DUK_ASSERT(thr != NULL); + + DUK_DD(DUK_DDPRINT("duk__finalize_refcounts: heap=%p, hthread=%p", + (void *) heap, (void *) thr)); + + 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)); + duk_heaphdr_refcount_finalize(thr, hdr); + } + + hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr); + } +} +#endif /* DUK_USE_REFERENCE_COUNTING */ + +/* + * Clear (reachable) flags of refzero work list. + */ + +#ifdef DUK_USE_REFERENCE_COUNTING +DUK_LOCAL void duk__clear_refzero_list_flags(duk_heap *heap) { + duk_heaphdr *hdr; + + DUK_DD(DUK_DDPRINT("duk__clear_refzero_list_flags: %p", (void *) heap)); + + hdr = heap->refzero_list; + while (hdr) { + DUK_HEAPHDR_CLEAR_REACHABLE(hdr); + DUK_ASSERT(!DUK_HEAPHDR_HAS_FINALIZABLE(hdr)); + /* DUK_HEAPHDR_HAS_FINALIZED may or may not be set. */ + DUK_ASSERT(!DUK_HEAPHDR_HAS_TEMPROOT(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.) + */ + +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); + } +} + +/* + * Sweep stringtable + */ + +#if defined(DUK_USE_STRTAB_CHAIN) + +/* XXX: skip count_free w/o debug? */ +#if defined(DUK_USE_HEAPPTR16) +DUK_LOCAL void duk__sweep_string_chain16(duk_heap *heap, duk_uint16_t *slot, duk_size_t *count_keep, duk_size_t *count_free) { + duk_uint16_t h16 = *slot; + duk_hstring *h; + duk_uint16_t null16 = heap->heapptr_null16; + + if (h16 == null16) { + /* nop */ + return; + } + h = (duk_hstring *) DUK_USE_HEAPPTR_DEC16(heap->heap_udata, h16); + DUK_ASSERT(h != NULL); + + if (DUK_HEAPHDR_HAS_REACHABLE((duk_heaphdr *) h)) { + DUK_HEAPHDR_CLEAR_REACHABLE((duk_heaphdr *) h); + (*count_keep)++; + } else { +#if defined(DUK_USE_REFERENCE_COUNTING) + 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); + *slot = null16; + + /* free inner references (these exist e.g. when external + * strings are enabled) + */ + duk_free_hstring_inner(heap, h); + DUK_FREE(heap, h); + (*count_free)++; + } +} +#else /* DUK_USE_HEAPPTR16 */ +DUK_LOCAL void duk__sweep_string_chain(duk_heap *heap, duk_hstring **slot, duk_size_t *count_keep, duk_size_t *count_free) { + duk_hstring *h = *slot; + + if (h == NULL) { + /* nop */ + return; + } + + if (DUK_HEAPHDR_HAS_REACHABLE((duk_heaphdr *) h)) { + DUK_HEAPHDR_CLEAR_REACHABLE((duk_heaphdr *) h); + (*count_keep)++; + } else { +#if defined(DUK_USE_REFERENCE_COUNTING) + 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); + *slot = NULL; + + /* free inner references (these exist e.g. when external + * strings are enabled) + */ + duk_free_hstring_inner(heap, h); + DUK_FREE(heap, h); + (*count_free)++; + } +} +#endif /* DUK_USE_HEAPPTR16 */ + +DUK_LOCAL void duk__sweep_stringtable_chain(duk_heap *heap, duk_size_t *out_count_keep) { + duk_strtab_entry *e; + duk_uint_fast32_t i; + duk_size_t count_free = 0; + duk_size_t count_keep = 0; + duk_size_t j, n; +#if defined(DUK_USE_HEAPPTR16) + duk_uint16_t *lst; +#else + duk_hstring **lst; +#endif + + DUK_DD(DUK_DDPRINT("duk__sweep_stringtable: %p", (void *) heap)); + + /* 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). + */ + + for (i = 0; i < DUK_STRTAB_CHAIN_SIZE; i++) { + e = heap->strtable + i; + if (e->listlen == 0) { +#if defined(DUK_USE_HEAPPTR16) + duk__sweep_string_chain16(heap, &e->u.str16, &count_keep, &count_free); +#else + duk__sweep_string_chain(heap, &e->u.str, &count_keep, &count_free); +#endif + } else { +#if defined(DUK_USE_HEAPPTR16) + lst = (duk_uint16_t *) DUK_USE_HEAPPTR_DEC16(heap->heap_udata, e->u.strlist16); +#else + lst = e->u.strlist; +#endif + for (j = 0, n = e->listlen; j < n; j++) { +#if defined(DUK_USE_HEAPPTR16) + duk__sweep_string_chain16(heap, lst + j, &count_keep, &count_free); +#else + duk__sweep_string_chain(heap, lst + j, &count_keep, &count_free); +#endif + } + } + } + + DUK_D(DUK_DPRINT("mark-and-sweep sweep stringtable: %ld freed, %ld kept", + (long) count_free, (long) count_keep)); + *out_count_keep = count_keep; +} +#endif /* DUK_USE_STRTAB_CHAIN */ + +#if defined(DUK_USE_STRTAB_PROBE) +DUK_LOCAL void duk__sweep_stringtable_probe(duk_heap *heap, duk_size_t *out_count_keep) { + duk_hstring *h; + duk_uint_fast32_t i; +#ifdef 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)); + + for (i = 0; i < heap->st_size; i++) { +#if defined(DUK_USE_HEAPPTR16) + h = (duk_hstring *) DUK_USE_HEAPPTR_DEC16(heap->heap_udata, heap->strtable16[i]); +#else + h = heap->strtable[i]; +#endif + if (h == NULL || h == DUK_STRTAB_DELETED_MARKER(heap)) { + continue; + } else if (DUK_HEAPHDR_HAS_REACHABLE((duk_heaphdr *) h)) { + DUK_HEAPHDR_CLEAR_REACHABLE((duk_heaphdr *) h); + count_keep++; + continue; + } + +#ifdef 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 + + DUK_DDD(DUK_DDDPRINT("sweep string, not reachable: %p", (void *) h)); + + /* deal with weak references first */ + duk_heap_strcache_string_remove(heap, (duk_hstring *) h); + + /* remove the string (mark DELETED), could also call + * duk_heap_string_remove() but that would be slow and + * pointless because we already know the slot. + */ +#if defined(DUK_USE_HEAPPTR16) + heap->strtable16[i] = heap->heapptr_deleted16; +#else + heap->strtable[i] = DUK_STRTAB_DELETED_MARKER(heap); +#endif + + /* free inner references (these exist e.g. when external + * strings are enabled) + */ + duk_free_hstring_inner(heap, (duk_hstring *) h); + + /* finally free the struct itself */ + DUK_FREE(heap, h); + } + +#ifdef 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; +} +#endif /* DUK_USE_STRTAB_PROBE */ + +/* + * 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; +#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 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)); + +#ifdef 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; +#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. + */ + 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); + } +#ifdef 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. + */ + +#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(heap, prev, NULL); + } + DUK_ASSERT_HEAPHDR_LINKS(heap, prev); + +#ifdef 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; +} + +/* + * Run (object) finalizers in the "to be finalized" work list. + */ + +DUK_LOCAL void duk__run_object_finalizers(duk_heap *heap, duk_small_uint_t flags) { + duk_heaphdr *curr; + duk_heaphdr *next; +#ifdef 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 */ + + /* Keep heap->finalize_list up-to-date during the list walk. + * This has no functional impact, but does matter e.g. for + * duk_push_heapptr() asserts when assertions are enabled. + */ + heap->finalize_list = curr; + + 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)); + + /* XXX: could clear FINALIZED already here; now cleared in + * next mark-and-sweep. + */ + } 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; +#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: %ld finalizers called", (long) count)); +#endif +} + +/* + * Object compaction. + * + * Compaction is assumed to never throw an error. + */ + +DUK_LOCAL int duk__protected_compact_object(duk_context *ctx) { + /* XXX: for threads, compact value stack, call stack, catch stack? */ + + duk_hobject *obj = duk_get_hobject(ctx, -1); + DUK_ASSERT(obj != NULL); + duk_hobject_compact_props((duk_hthread *) ctx, obj); + return 0; +} + +#ifdef 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; +#ifdef 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; + +#ifdef 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((duk_context *) thr, obj); + /* XXX: disable error handlers for duration of compaction? */ + duk_safe_call((duk_context *) thr, duk__protected_compact_object, 1, 0); + +#ifdef 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 + +#ifdef 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); +#ifdef DUK_USE_DEBUG + (*p_count_check)++; +#endif + } +} + +DUK_LOCAL void duk__compact_objects(duk_heap *heap) { + /* XXX: which lists should participate? to be finalized? */ +#ifdef DUK_USE_DEBUG + duk_size_t count_check = 0; + duk_size_t count_compact = 0; + duk_size_t count_bytes_saved = 0; +#endif + duk_hthread *thr; + + DUK_DD(DUK_DDPRINT("duk__compact_objects: %p", (void *) heap)); + + thr = duk__get_temp_hthread(heap); + DUK_ASSERT(thr != NULL); + +#ifdef DUK_USE_DEBUG + duk__compact_object_list(heap, thr, heap->heap_allocated, &count_check, &count_compact, &count_bytes_saved); + duk__compact_object_list(heap, thr, heap->finalize_list, &count_check, &count_compact, &count_bytes_saved); +#ifdef DUK_USE_REFERENCE_COUNTING + duk__compact_object_list(heap, thr, heap->refzero_list, &count_check, &count_compact, &count_bytes_saved); +#endif +#else + duk__compact_object_list(heap, thr, heap->heap_allocated); + duk__compact_object_list(heap, thr, heap->finalize_list); +#ifdef DUK_USE_REFERENCE_COUNTING + duk__compact_object_list(heap, thr, heap->refzero_list); +#endif +#endif + +#ifdef 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. + */ + +#ifdef DUK_USE_ASSERTIONS +DUK_LOCAL 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(heap, 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_HEAPHDR_HAS_FINALIZED may be set if we're doing a + * refzero finalization and mark-and-sweep gets triggered + * during the finalizer. + */ + /* DUK_HEAPHDR_HAS_FINALIZED may or may not be set. */ + hdr = DUK_HEAPHDR_GET_NEXT(heap, hdr); + } +#endif /* DUK_USE_REFERENCE_COUNTING */ +} + +#ifdef DUK_USE_REFERENCE_COUNTING +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); + } +} +#endif /* DUK_USE_REFERENCE_COUNTING */ +#endif /* DUK_USE_ASSERTIONS */ + +/* + * Finalizer torture. Do one fake finalizer call which causes side effects + * similar to one or more finalizers on actual objects. + */ + +#if defined(DUK_USE_MARKANDSWEEP_FINALIZER_TORTURE) +DUK_LOCAL duk_ret_t duk__markandsweep_fake_finalizer(duk_context *ctx) { + DUK_D(DUK_DPRINT("fake mark-and-sweep torture finalizer executed")); + + /* Require a lot of stack to force a value stack grow/shrink. + * Recursive mark-and-sweep is prevented by allocation macros + * so this won't trigger another mark-and-sweep. + */ + duk_require_stack(ctx, 100000); + + /* XXX: do something to force a callstack grow/shrink, perhaps + * just a manual forced resize or a forced relocating realloc? + */ + + return 0; +} + +DUK_LOCAL void duk__markandsweep_torture_finalizer(duk_hthread *thr) { + duk_context *ctx; + duk_int_t rc; + + DUK_ASSERT(thr != NULL); + ctx = (duk_context *) thr; + + /* Avoid fake finalization when callstack limit has been reached. + * Otherwise a callstack limit error will be created, then refzero'ed. + */ + if (thr->heap->call_recursion_depth >= thr->heap->call_recursion_limit || + thr->callstack_size + 2 * DUK_CALLSTACK_GROW_STEP >= thr->callstack_max /*approximate*/) { + DUK_D(DUK_DPRINT("call recursion depth reached, avoid fake mark-and-sweep torture finalizer")); + return; + } + + /* Run fake finalizer. Avoid creating unnecessary garbage. */ + duk_push_c_function(ctx, duk__markandsweep_fake_finalizer, 0 /*nargs*/); + rc = duk_pcall(ctx, 0 /*nargs*/); + DUK_UNREF(rc); /* ignored */ + duk_pop(ctx); +} +#endif /* DUK_USE_MARKANDSWEEP_FINALIZER_TORTURE */ + +/* + * Main mark-and-sweep function. + * + * 'flags' represents the features requested by the caller. The current + * heap->mark_and_sweep_base_flags is ORed automatically into the flags; + * the base flags mask typically prevents certain mark-and-sweep operations + * to avoid trouble. + */ + +DUK_INTERNAL duk_bool_t duk_heap_mark_and_sweep(duk_heap *heap, duk_small_uint_t flags) { + duk_hthread *thr; + duk_size_t count_keep_obj; + duk_size_t count_keep_str; +#ifdef DUK_USE_VOLUNTARY_GC + duk_size_t tmp; +#endif + + if (DUK_HEAP_HAS_MARKANDSWEEP_RUNNING(heap)) { + DUK_D(DUK_DPRINT("refuse to do a recursive mark-and-sweep")); + return 0; + } + + /* XXX: thread selection for mark-and-sweep is currently a hack. + * If we don't have a thread, the entire mark-and-sweep is now + * skipped (although we could just skip finalizations). + */ + + /* If thr != NULL, the thr may still be in the middle of + * initialization. + * XXX: Improve the thread viability test. + */ + thr = duk__get_temp_hthread(heap); + if (thr == NULL) { + DUK_D(DUK_DPRINT("gc skipped because we don't have a temp thread")); + + /* reset voluntary gc trigger count */ +#ifdef DUK_USE_VOLUNTARY_GC + heap->mark_and_sweep_trigger_counter = DUK_HEAP_MARK_AND_SWEEP_TRIGGER_SKIP; +#endif + return 0; /* OK */ + } + + /* If debugger is paused, garbage collection is disabled by default. */ + /* XXX: will need a force flag if garbage collection is triggered + * explicitly during paused state. + */ +#if defined(DUK_USE_DEBUGGER_SUPPORT) + if (DUK_HEAP_IS_PAUSED(heap)) { + /* Checking this here rather that in memory alloc primitives + * reduces checking code there but means a failed allocation + * will go through a few retries before giving up. That's + * fine because this only happens during debugging. + */ + DUK_D(DUK_DPRINT("gc skipped because debugger is paused")); + return 0; + } +#endif + + 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->mark_and_sweep_base_flags))); + + flags |= heap->mark_and_sweep_base_flags; + + /* + * Assertions before + */ + +#ifdef DUK_USE_ASSERTIONS + DUK_ASSERT(!DUK_HEAP_HAS_MARKANDSWEEP_RUNNING(heap)); + DUK_ASSERT(!DUK_HEAP_HAS_MARKANDSWEEP_RECLIMIT_REACHED(heap)); + DUK_ASSERT(heap->mark_and_sweep_recursion_depth == 0); + duk__assert_heaphdr_flags(heap); +#ifdef DUK_USE_REFERENCE_COUNTING + /* Note: DUK_HEAP_HAS_REFZERO_FREE_RUNNING(heap) 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_HEAP_SET_MARKANDSWEEP_RUNNING(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. + */ + + duk__mark_roots_heap(heap); /* main reachability roots */ +#ifdef DUK_USE_REFERENCE_COUNTING + duk__mark_refzero_list(heap); /* refzero_list treated as reachability roots */ +#endif + duk__mark_temproots_by_heap_scan(heap); /* temproots */ + + duk__mark_finalizable(heap); /* mark finalizable as reachability roots */ + duk__mark_finalize_list(heap); /* mark finalizer work list as reachability roots */ + 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 */ + +#ifdef DUK_USE_REFERENCE_COUNTING + duk__finalize_refcounts(heap); +#endif + duk__sweep_heap(heap, flags, &count_keep_obj); +#if defined(DUK_USE_STRTAB_CHAIN) + duk__sweep_stringtable_chain(heap, &count_keep_str); +#elif defined(DUK_USE_STRTAB_PROBE) + duk__sweep_stringtable_probe(heap, &count_keep_str); +#else +#error internal error, invalid strtab options +#endif +#ifdef DUK_USE_REFERENCE_COUNTING + duk__clear_refzero_list_flags(heap); +#endif + duk__clear_finalize_list_flags(heap); + + /* + * 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). + */ + + if ((flags & DUK_MS_FLAG_EMERGENCY) && + !(flags & DUK_MS_FLAG_NO_OBJECT_COMPACTION)) { + duk__compact_objects(heap); + } + + /* + * String table resize check. + * + * Note: this may silently (and safely) fail if GC is caused by an + * allocation call in stringtable resize_hash(). Resize_hash() + * will prevent a recursive call to itself by setting the + * DUK_MS_FLAG_NO_STRINGTABLE_RESIZE in heap->mark_and_sweep_base_flags. + */ + + /* XXX: stringtable emergency compaction? */ + + /* XXX: remove this feature entirely? it would only matter for + * emergency GC. Disable for lowest memory builds. + */ +#if defined(DUK_USE_MS_STRINGTABLE_RESIZE) + if (!(flags & DUK_MS_FLAG_NO_STRINGTABLE_RESIZE)) { + DUK_DD(DUK_DDPRINT("resize stringtable: %p", (void *) heap)); + duk_heap_force_strtab_resize(heap); + } else { + DUK_D(DUK_DPRINT("stringtable resize skipped because DUK_MS_FLAG_NO_STRINGTABLE_RESIZE is set")); + } +#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 during string table and object property allocation + * resizing using the DUK_MS_FLAG_NO_FINALIZERS flag in + * heap->mark_and_sweep_base_flags. 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. + * + * Finalization currently happens inside "MARKANDSWEEP_RUNNING" + * protection (no mark-and-sweep may be triggered by the + * finalizers). As a side effect: + * + * 1) an out-of-memory error inside a finalizer will not + * cause a mark-and-sweep and may cause the finalizer + * to fail unnecessarily + * + * 2) any temporary objects whose refcount decreases to zero + * during finalization will not be put into refzero_list; + * they can only be collected by another mark-and-sweep + * + * This is not optimal, but since the sweep for this phase has + * already happened, this is probably good enough for now. + */ + +#if defined(DUK_USE_MARKANDSWEEP_FINALIZER_TORTURE) + /* Cannot simulate individual finalizers because finalize_list only + * contains objects with actual finalizers. But simulate side effects + * from finalization by doing a bogus function call and resizing the + * stacks. + */ + if (flags & DUK_MS_FLAG_NO_FINALIZERS) { + DUK_D(DUK_DPRINT("skip mark-and-sweep torture finalizer, DUK_MS_FLAG_NO_FINALIZERS is set")); + } else if (!(thr->valstack != NULL && thr->callstack != NULL && thr->catchstack != NULL)) { + DUK_D(DUK_DPRINT("skip mark-and-sweep torture finalizer, thread not yet viable")); + } else { + DUK_D(DUK_DPRINT("run mark-and-sweep torture finalizer")); + duk__markandsweep_torture_finalizer(thr); + } +#endif /* DUK_USE_MARKANDSWEEP_FINALIZER_TORTURE */ + + if (flags & DUK_MS_FLAG_NO_FINALIZERS) { + DUK_D(DUK_DPRINT("finalizer run skipped because DUK_MS_FLAG_NO_FINALIZERS is set")); + } else { + duk__run_object_finalizers(heap, flags); + } + + /* + * Finish + */ + + DUK_HEAP_CLEAR_MARKANDSWEEP_RUNNING(heap); + + /* + * Assertions after + */ + +#ifdef DUK_USE_ASSERTIONS + DUK_ASSERT(!DUK_HEAP_HAS_MARKANDSWEEP_RUNNING(heap)); + DUK_ASSERT(!DUK_HEAP_HAS_MARKANDSWEEP_RECLIMIT_REACHED(heap)); + DUK_ASSERT(heap->mark_and_sweep_recursion_depth == 0); + duk__assert_heaphdr_flags(heap); +#ifdef DUK_USE_REFERENCE_COUNTING + /* Note: DUK_HEAP_HAS_REFZERO_FREE_RUNNING(heap) 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 */ + + /* + * Reset trigger counter + */ + +#ifdef DUK_USE_VOLUNTARY_GC + tmp = (count_keep_obj + count_keep_str) / 256; + heap->mark_and_sweep_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->mark_and_sweep_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 + + return 0; /* OK */ +} + +#else /* DUK_USE_MARK_AND_SWEEP */ + +/* no mark-and-sweep gc */ + +#endif /* DUK_USE_MARK_AND_SWEEP */ |