--- /dev/null
+/*
+ * Manipulation of thread stacks (valstack, callstack, catchstack).
+ *
+ * Ideally unwinding of stacks should have no side effects, which would
+ * then favor separate unwinding and shrink check primitives for each
+ * stack type. A shrink check may realloc and thus have side effects.
+ *
+ * However, currently callstack unwinding itself has side effects, as it
+ * needs to DECREF multiple objects, close environment records, etc.
+ * Stacks must thus be unwound in the correct order by the caller.
+ *
+ * (XXX: This should be probably reworked so that there is a shared
+ * unwind primitive which handles all stacks as requested, and knows
+ * the proper order for unwinding.)
+ *
+ * Valstack entries above 'top' are always kept initialized to
+ * "undefined unused". Callstack and catchstack entries above 'top'
+ * are not zeroed and are left as garbage.
+ *
+ * Value stack handling is mostly a part of the API implementation.
+ */
+
+#include "duk_internal.h"
+
+/* check that there is space for at least one new entry */
+DUK_INTERNAL void duk_hthread_callstack_grow(duk_hthread *thr) {
+ duk_activation *new_ptr;
+ duk_size_t old_size;
+ duk_size_t new_size;
+
+ DUK_ASSERT(thr != NULL);
+ DUK_ASSERT_DISABLE(thr->callstack_top >= 0); /* avoid warning (unsigned) */
+ DUK_ASSERT(thr->callstack_size >= thr->callstack_top);
+
+ if (thr->callstack_top < thr->callstack_size) {
+ return;
+ }
+
+ old_size = thr->callstack_size;
+ new_size = old_size + DUK_CALLSTACK_GROW_STEP;
+
+ /* this is a bit approximate (errors out before max is reached); this is OK */
+ if (new_size >= thr->callstack_max) {
+ DUK_ERROR_RANGE(thr, DUK_STR_CALLSTACK_LIMIT);
+ }
+
+ DUK_DD(DUK_DDPRINT("growing callstack %ld -> %ld", (long) old_size, (long) new_size));
+
+ /*
+ * Note: must use indirect variant of DUK_REALLOC() because underlying
+ * pointer may be changed by mark-and-sweep.
+ */
+
+ DUK_ASSERT(new_size > 0);
+ new_ptr = (duk_activation *) DUK_REALLOC_INDIRECT(thr->heap, duk_hthread_get_callstack_ptr, (void *) thr, sizeof(duk_activation) * new_size);
+ if (!new_ptr) {
+ /* No need for a NULL/zero-size check because new_size > 0) */
+ DUK_ERROR_ALLOC_DEFMSG(thr);
+ }
+ thr->callstack = new_ptr;
+ thr->callstack_size = new_size;
+
+ /* note: any entries above the callstack top are garbage and not zeroed */
+}
+
+DUK_INTERNAL void duk_hthread_callstack_shrink_check(duk_hthread *thr) {
+ duk_size_t new_size;
+ duk_activation *p;
+
+ DUK_ASSERT(thr != NULL);
+ DUK_ASSERT_DISABLE(thr->callstack_top >= 0); /* avoid warning (unsigned) */
+ DUK_ASSERT(thr->callstack_size >= thr->callstack_top);
+
+ if (thr->callstack_size - thr->callstack_top < DUK_CALLSTACK_SHRINK_THRESHOLD) {
+ return;
+ }
+
+ new_size = thr->callstack_top + DUK_CALLSTACK_SHRINK_SPARE;
+ DUK_ASSERT(new_size >= thr->callstack_top);
+
+ DUK_DD(DUK_DDPRINT("shrinking callstack %ld -> %ld", (long) thr->callstack_size, (long) new_size));
+
+ /*
+ * Note: must use indirect variant of DUK_REALLOC() because underlying
+ * pointer may be changed by mark-and-sweep.
+ */
+
+ /* shrink failure is not fatal */
+ p = (duk_activation *) DUK_REALLOC_INDIRECT(thr->heap, duk_hthread_get_callstack_ptr, (void *) thr, sizeof(duk_activation) * new_size);
+ if (p) {
+ thr->callstack = p;
+ thr->callstack_size = new_size;
+ } else {
+ /* Because new_size != 0, if condition doesn't need to be
+ * (p != NULL || new_size == 0).
+ */
+ DUK_ASSERT(new_size != 0);
+ DUK_D(DUK_DPRINT("callstack shrink failed, ignoring"));
+ }
+
+ /* note: any entries above the callstack top are garbage and not zeroed */
+}
+
+DUK_INTERNAL void duk_hthread_callstack_unwind(duk_hthread *thr, duk_size_t new_top) {
+ duk_size_t idx;
+
+ DUK_DDD(DUK_DDDPRINT("unwind callstack top of thread %p from %ld to %ld",
+ (void *) thr,
+ (thr != NULL ? (long) thr->callstack_top : (long) -1),
+ (long) new_top));
+
+ DUK_ASSERT(thr);
+ DUK_ASSERT(thr->heap);
+ DUK_ASSERT_DISABLE(new_top >= 0); /* unsigned */
+ DUK_ASSERT((duk_size_t) new_top <= thr->callstack_top); /* cannot grow */
+
+ /*
+ * The loop below must avoid issues with potential callstack
+ * reallocations. A resize (and other side effects) may happen
+ * e.g. due to finalizer/errhandler calls caused by a refzero or
+ * mark-and-sweep. Arbitrary finalizers may run, because when
+ * an environment record is refzero'd, it may refer to arbitrary
+ * values which also become refzero'd.
+ *
+ * So, the pointer 'p' is re-looked-up below whenever a side effect
+ * might have changed it.
+ */
+
+ idx = thr->callstack_top;
+ while (idx > new_top) {
+ duk_activation *act;
+ duk_hobject *func;
+#ifdef DUK_USE_REFERENCE_COUNTING
+ duk_hobject *tmp;
+#endif
+#ifdef DUK_USE_DEBUGGER_SUPPORT
+ duk_heap *heap;
+#endif
+
+ idx--;
+ DUK_ASSERT_DISABLE(idx >= 0); /* unsigned */
+ DUK_ASSERT((duk_size_t) idx < thr->callstack_size); /* true, despite side effect resizes */
+
+ act = thr->callstack + idx;
+ /* With lightfuncs, act 'func' may be NULL */
+
+#ifdef DUK_USE_NONSTD_FUNC_CALLER_PROPERTY
+ /*
+ * Restore 'caller' property for non-strict callee functions.
+ */
+
+ func = DUK_ACT_GET_FUNC(act);
+ if (func != NULL && !DUK_HOBJECT_HAS_STRICT(func)) {
+ duk_tval *tv_caller;
+ duk_tval tv_tmp;
+ duk_hobject *h_tmp;
+
+ tv_caller = duk_hobject_find_existing_entry_tval_ptr(thr->heap, func, DUK_HTHREAD_STRING_CALLER(thr));
+
+ /* The act->prev_caller should only be set if the entry for 'caller'
+ * exists (as it is only set in that case, and the property is not
+ * configurable), but handle all the cases anyway.
+ */
+
+ if (tv_caller) {
+ DUK_TVAL_SET_TVAL(&tv_tmp, tv_caller);
+ if (act->prev_caller) {
+ /* Just transfer the refcount from act->prev_caller to tv_caller,
+ * so no need for a refcount update. This is the expected case.
+ */
+ DUK_TVAL_SET_OBJECT(tv_caller, act->prev_caller);
+ act->prev_caller = NULL;
+ } else {
+ DUK_TVAL_SET_NULL(tv_caller); /* no incref needed */
+ DUK_ASSERT(act->prev_caller == NULL);
+ }
+ DUK_TVAL_DECREF(thr, &tv_tmp); /* side effects */
+ } else {
+ h_tmp = act->prev_caller;
+ if (h_tmp) {
+ act->prev_caller = NULL;
+ DUK_HOBJECT_DECREF(thr, h_tmp); /* side effects */
+ }
+ }
+ act = thr->callstack + idx; /* avoid side effects */
+ DUK_ASSERT(act->prev_caller == NULL);
+ }
+#endif
+
+ /*
+ * Unwind debugger state. If we unwind while stepping
+ * (either step over or step into), pause execution.
+ */
+
+#if defined(DUK_USE_DEBUGGER_SUPPORT)
+ heap = thr->heap;
+ if (heap->dbg_step_thread == thr &&
+ heap->dbg_step_csindex == idx) {
+ /* Pause for all step types: step into, step over, step out.
+ * This is the only place explicitly handling a step out.
+ */
+ DUK_HEAP_SET_PAUSED(heap);
+ DUK_ASSERT(heap->dbg_step_thread == NULL);
+ }
+#endif
+
+ /*
+ * Close environment record(s) if they exist.
+ *
+ * Only variable environments are closed. If lex_env != var_env, it
+ * cannot currently contain any register bound declarations.
+ *
+ * Only environments created for a NEWENV function are closed. If an
+ * environment is created for e.g. an eval call, it must not be closed.
+ */
+
+ func = DUK_ACT_GET_FUNC(act);
+ if (func != NULL && !DUK_HOBJECT_HAS_NEWENV(func)) {
+ DUK_DDD(DUK_DDDPRINT("skip closing environments, envs not owned by this activation"));
+ goto skip_env_close;
+ }
+ /* func is NULL for lightfunc */
+
+ DUK_ASSERT(act->lex_env == act->var_env);
+ if (act->var_env != NULL) {
+ DUK_DDD(DUK_DDDPRINT("closing var_env record %p -> %!O",
+ (void *) act->var_env, (duk_heaphdr *) act->var_env));
+ duk_js_close_environment_record(thr, act->var_env, func, act->idx_bottom);
+ act = thr->callstack + idx; /* avoid side effect issues */
+ }
+
+#if 0
+ if (act->lex_env != NULL) {
+ if (act->lex_env == act->var_env) {
+ /* common case, already closed, so skip */
+ DUK_DD(DUK_DDPRINT("lex_env and var_env are the same and lex_env "
+ "already closed -> skip closing lex_env"));
+ ;
+ } else {
+ DUK_DD(DUK_DDPRINT("closing lex_env record %p -> %!O",
+ (void *) act->lex_env, (duk_heaphdr *) act->lex_env));
+ duk_js_close_environment_record(thr, act->lex_env, DUK_ACT_GET_FUNC(act), act->idx_bottom);
+ act = thr->callstack + idx; /* avoid side effect issues */
+ }
+ }
+#endif
+
+ DUK_ASSERT((act->lex_env == NULL) ||
+ ((duk_hobject_find_existing_entry_tval_ptr(thr->heap, act->lex_env, DUK_HTHREAD_STRING_INT_CALLEE(thr)) == NULL) &&
+ (duk_hobject_find_existing_entry_tval_ptr(thr->heap, act->lex_env, DUK_HTHREAD_STRING_INT_VARMAP(thr)) == NULL) &&
+ (duk_hobject_find_existing_entry_tval_ptr(thr->heap, act->lex_env, DUK_HTHREAD_STRING_INT_THREAD(thr)) == NULL) &&
+ (duk_hobject_find_existing_entry_tval_ptr(thr->heap, act->lex_env, DUK_HTHREAD_STRING_INT_REGBASE(thr)) == NULL)));
+
+ DUK_ASSERT((act->var_env == NULL) ||
+ ((duk_hobject_find_existing_entry_tval_ptr(thr->heap, act->var_env, DUK_HTHREAD_STRING_INT_CALLEE(thr)) == NULL) &&
+ (duk_hobject_find_existing_entry_tval_ptr(thr->heap, act->var_env, DUK_HTHREAD_STRING_INT_VARMAP(thr)) == NULL) &&
+ (duk_hobject_find_existing_entry_tval_ptr(thr->heap, act->var_env, DUK_HTHREAD_STRING_INT_THREAD(thr)) == NULL) &&
+ (duk_hobject_find_existing_entry_tval_ptr(thr->heap, act->var_env, DUK_HTHREAD_STRING_INT_REGBASE(thr)) == NULL)));
+
+ skip_env_close:
+
+ /*
+ * Update preventcount
+ */
+
+ if (act->flags & DUK_ACT_FLAG_PREVENT_YIELD) {
+ DUK_ASSERT(thr->callstack_preventcount >= 1);
+ thr->callstack_preventcount--;
+ }
+
+ /*
+ * Reference count updates
+ *
+ * Note: careful manipulation of refcounts. The top is
+ * not updated yet, so all the activations are reachable
+ * for mark-and-sweep (which may be triggered by decref).
+ * However, the pointers are NULL so this is not an issue.
+ */
+
+#ifdef DUK_USE_REFERENCE_COUNTING
+ tmp = act->var_env;
+#endif
+ act->var_env = NULL;
+#ifdef DUK_USE_REFERENCE_COUNTING
+ DUK_HOBJECT_DECREF_ALLOWNULL(thr, tmp);
+ act = thr->callstack + idx; /* avoid side effect issues */
+#endif
+
+#ifdef DUK_USE_REFERENCE_COUNTING
+ tmp = act->lex_env;
+#endif
+ act->lex_env = NULL;
+#ifdef DUK_USE_REFERENCE_COUNTING
+ DUK_HOBJECT_DECREF_ALLOWNULL(thr, tmp);
+ act = thr->callstack + idx; /* avoid side effect issues */
+#endif
+
+ /* Note: this may cause a corner case situation where a finalizer
+ * may see a currently reachable activation whose 'func' is NULL.
+ */
+#ifdef DUK_USE_REFERENCE_COUNTING
+ tmp = DUK_ACT_GET_FUNC(act);
+#endif
+ act->func = NULL;
+#ifdef DUK_USE_REFERENCE_COUNTING
+ DUK_HOBJECT_DECREF_ALLOWNULL(thr, tmp);
+ act = thr->callstack + idx; /* avoid side effect issues */
+ DUK_UNREF(act);
+#endif
+ }
+
+ thr->callstack_top = new_top;
+
+ /*
+ * We could clear the book-keeping variables for the topmost activation,
+ * but don't do so now.
+ */
+#if 0
+ if (thr->callstack_top > 0) {
+ duk_activation *act = thr->callstack + thr->callstack_top - 1;
+ act->idx_retval = 0;
+ }
+#endif
+
+ /* Note: any entries above the callstack top are garbage and not zeroed.
+ * Also topmost activation idx_retval is garbage (not zeroed), and must
+ * be ignored.
+ */
+}
+
+DUK_INTERNAL void duk_hthread_catchstack_grow(duk_hthread *thr) {
+ duk_catcher *new_ptr;
+ duk_size_t old_size;
+ duk_size_t new_size;
+
+ DUK_ASSERT(thr != NULL);
+ DUK_ASSERT_DISABLE(thr->catchstack_top); /* avoid warning (unsigned) */
+ DUK_ASSERT(thr->catchstack_size >= thr->catchstack_top);
+
+ if (thr->catchstack_top < thr->catchstack_size) {
+ return;
+ }
+
+ old_size = thr->catchstack_size;
+ new_size = old_size + DUK_CATCHSTACK_GROW_STEP;
+
+ /* this is a bit approximate (errors out before max is reached); this is OK */
+ if (new_size >= thr->catchstack_max) {
+ DUK_ERROR_RANGE(thr, DUK_STR_CATCHSTACK_LIMIT);
+ }
+
+ DUK_DD(DUK_DDPRINT("growing catchstack %ld -> %ld", (long) old_size, (long) new_size));
+
+ /*
+ * Note: must use indirect variant of DUK_REALLOC() because underlying
+ * pointer may be changed by mark-and-sweep.
+ */
+
+ DUK_ASSERT(new_size > 0);
+ new_ptr = (duk_catcher *) DUK_REALLOC_INDIRECT(thr->heap, duk_hthread_get_catchstack_ptr, (void *) thr, sizeof(duk_catcher) * new_size);
+ if (!new_ptr) {
+ /* No need for a NULL/zero-size check because new_size > 0) */
+ DUK_ERROR_ALLOC_DEFMSG(thr);
+ }
+ thr->catchstack = new_ptr;
+ thr->catchstack_size = new_size;
+
+ /* note: any entries above the catchstack top are garbage and not zeroed */
+}
+
+DUK_INTERNAL void duk_hthread_catchstack_shrink_check(duk_hthread *thr) {
+ duk_size_t new_size;
+ duk_catcher *p;
+
+ DUK_ASSERT(thr != NULL);
+ DUK_ASSERT_DISABLE(thr->catchstack_top >= 0); /* avoid warning (unsigned) */
+ DUK_ASSERT(thr->catchstack_size >= thr->catchstack_top);
+
+ if (thr->catchstack_size - thr->catchstack_top < DUK_CATCHSTACK_SHRINK_THRESHOLD) {
+ return;
+ }
+
+ new_size = thr->catchstack_top + DUK_CATCHSTACK_SHRINK_SPARE;
+ DUK_ASSERT(new_size >= thr->catchstack_top);
+
+ DUK_DD(DUK_DDPRINT("shrinking catchstack %ld -> %ld", (long) thr->catchstack_size, (long) new_size));
+
+ /*
+ * Note: must use indirect variant of DUK_REALLOC() because underlying
+ * pointer may be changed by mark-and-sweep.
+ */
+
+ /* shrink failure is not fatal */
+ p = (duk_catcher *) DUK_REALLOC_INDIRECT(thr->heap, duk_hthread_get_catchstack_ptr, (void *) thr, sizeof(duk_catcher) * new_size);
+ if (p) {
+ thr->catchstack = p;
+ thr->catchstack_size = new_size;
+ } else {
+ /* Because new_size != 0, if condition doesn't need to be
+ * (p != NULL || new_size == 0).
+ */
+ DUK_ASSERT(new_size != 0);
+ DUK_D(DUK_DPRINT("catchstack shrink failed, ignoring"));
+ }
+
+ /* note: any entries above the catchstack top are garbage and not zeroed */
+}
+
+DUK_INTERNAL void duk_hthread_catchstack_unwind(duk_hthread *thr, duk_size_t new_top) {
+ duk_size_t idx;
+
+ DUK_DDD(DUK_DDDPRINT("unwind catchstack top of thread %p from %ld to %ld",
+ (void *) thr,
+ (thr != NULL ? (long) thr->catchstack_top : (long) -1),
+ (long) new_top));
+
+ DUK_ASSERT(thr);
+ DUK_ASSERT(thr->heap);
+ DUK_ASSERT_DISABLE(new_top >= 0); /* unsigned */
+ DUK_ASSERT((duk_size_t) new_top <= thr->catchstack_top); /* cannot grow */
+
+ /*
+ * Since there are no references in the catcher structure,
+ * unwinding is quite simple. The only thing we need to
+ * look out for is popping a possible lexical environment
+ * established for an active catch clause.
+ */
+
+ idx = thr->catchstack_top;
+ while (idx > new_top) {
+ duk_catcher *p;
+ duk_activation *act;
+ duk_hobject *env;
+
+ idx--;
+ DUK_ASSERT_DISABLE(idx >= 0); /* unsigned */
+ DUK_ASSERT((duk_size_t) idx < thr->catchstack_size);
+
+ p = thr->catchstack + idx;
+
+ if (DUK_CAT_HAS_LEXENV_ACTIVE(p)) {
+ DUK_DDD(DUK_DDDPRINT("unwinding catchstack idx %ld, callstack idx %ld, callstack top %ld: lexical environment active",
+ (long) idx, (long) p->callstack_index, (long) thr->callstack_top));
+
+ /* XXX: Here we have a nasty dependency: the need to manipulate
+ * the callstack means that catchstack must always be unwound by
+ * the caller before unwinding the callstack. This should be fixed
+ * later.
+ */
+
+ /* Note that multiple catchstack entries may refer to the same
+ * callstack entry.
+ */
+ act = thr->callstack + p->callstack_index;
+ DUK_ASSERT(act >= thr->callstack);
+ DUK_ASSERT(act < thr->callstack + thr->callstack_top);
+
+ DUK_DDD(DUK_DDDPRINT("catchstack_index=%ld, callstack_index=%ld, lex_env=%!iO",
+ (long) idx, (long) p->callstack_index,
+ (duk_heaphdr *) act->lex_env));
+
+ env = act->lex_env; /* current lex_env of the activation (created for catcher) */
+ DUK_ASSERT(env != NULL); /* must be, since env was created when catcher was created */
+ act->lex_env = DUK_HOBJECT_GET_PROTOTYPE(thr->heap, env); /* prototype is lex_env before catcher created */
+ DUK_HOBJECT_DECREF(thr, env);
+
+ /* There is no need to decref anything else than 'env': if 'env'
+ * becomes unreachable, refzero will handle decref'ing its prototype.
+ */
+ }
+ }
+
+ thr->catchstack_top = new_top;
+
+ /* note: any entries above the catchstack top are garbage and not zeroed */
+}
projects / ceph.git / blobdiff