MVMObject * references_str(MVMThreadContext *tc, MVMHeapSnapshot *s) {
    /* Produces ; separated sequences of:
     *   kind,idx,to
     * All of which are integers.
     */
    MVMObject *result;
    size_t buffer_size = 10 * s->num_references;
    size_t buffer_pos  = 0;
    char *buffer       = MVM_malloc(buffer_size);

    MVMuint64 i;
    for (i = 0; i < s->num_references; i++) {
        char tmp[128];
        int item_chars = snprintf(tmp, 128, "%"PRIu64",%"PRIu64",%"PRIu64";",
            s->references[i].description & ((1 << MVM_SNAPSHOT_REF_KIND_BITS) - 1),
            s->references[i].description >> MVM_SNAPSHOT_REF_KIND_BITS,
            s->references[i].collectable_index);
        if (item_chars < 0)
            MVM_panic(1, "Failed to save reference in heap snapshot");
        if (buffer_pos + item_chars >= buffer_size) {
            buffer_size += 4096;
            buffer = MVM_realloc(buffer, buffer_size);
        }
        memcpy(buffer + buffer_pos, tmp, item_chars);
        buffer_pos += item_chars;
    }
    if (buffer_pos > 1)
        buffer[buffer_pos - 1] = 0; /* Cut off the trailing ; for ease of parsing */
    buffer[buffer_pos] = 0;

    result = box_s(tc, vmstr(tc, buffer));
    MVM_free(buffer);
    return result;
}

MVMObject * types_str(MVMThreadContext *tc, MVMHeapSnapshotCollection *col) {
    /* Produces ; separated sequences of:
     *   repr_string_index,type_name_string_index
     * Both of which are integers.
     */
     MVMObject *result;
     size_t buffer_size = 10 * col->num_types;
     size_t buffer_pos  = 0;
     char *buffer       = MVM_malloc(buffer_size);

     MVMuint64 i;
     for (i = 0; i < col->num_types; i++) {
         char tmp[256];
         int item_chars = snprintf(tmp, 256,
            "%"PRIu64",%"PRIu64";",
            col->types[i].repr_name,
            col->types[i].type_name);
         if (item_chars < 0)
             MVM_panic(1, "Failed to save type in heap snapshot");
         if (buffer_pos + item_chars >= buffer_size) {
             buffer_size += 4096;
             buffer = MVM_realloc(buffer, buffer_size);
         }
         memcpy(buffer + buffer_pos, tmp, item_chars);
         buffer_pos += item_chars;
     }
    if (buffer_pos > 1)
        buffer[buffer_pos - 1] = 0; /* Cut off the trailing ; for ease of parsing */
     buffer[buffer_pos] = 0;

     result = box_s(tc, vmstr(tc, buffer));
     MVM_free(buffer);
     return result;
}

/* Adds a chunk of work to another thread's in-tray. */
static void push_work_to_thread_in_tray(MVMThreadContext *tc, MVMuint32 target, MVMGCPassedWork *work) {
    MVMint32 j;
    MVMGCPassedWork * volatile *target_tray;

    /* Locate the thread to pass the work to. */
    MVMThreadContext *target_tc = NULL;
    if (target == 1) {
        /* It's going to the main thread. */
        target_tc = tc->instance->main_thread;
    }
    else {
        MVMThread *t = (MVMThread *)MVM_load(&tc->instance->threads);
        do {
            if (t->body.tc && t->body.tc->thread_id == target) {
                target_tc = t->body.tc;
                break;
            }
        } while ((t = t->body.next));
        if (!target_tc)
            MVM_panic(MVM_exitcode_gcnursery, "Internal error: invalid thread ID in GC work pass");
    }

    /* Pass the work, chaining any other in-tray entries for the thread
     * after us. */
    target_tray = &target_tc->gc_in_tray;
    while (1) {
        MVMGCPassedWork *orig = *target_tray;
        work->next = orig;
        if (MVM_casptr(target_tray, orig, work) == orig)
            return;
    }
}

void *MVM_platform_alloc_pages(size_t size, int page_mode)
{
    int prot_mode = page_mode_to_prot_mode(page_mode);
    void * allocd = VirtualAlloc(NULL, size, MEM_COMMIT | MEM_RESERVE, prot_mode);
    if (!allocd)
        MVM_panic(1, "MVM_platform_alloc_pages failed: %d", GetLastError());
    return allocd;
}

/* Sets the current reference "from" collectable. */
static void set_ref_from(MVMThreadContext *tc, MVMHeapSnapshotState *ss, MVMuint64 col_idx) {
    /* The references should be contiguous, so if this collectable already
     * has any, something's wrong. */
    if (ss->hs->collectables[col_idx].num_refs)
        MVM_panic(1, "Heap snapshot corruption: can not add non-contiguous refs");

    ss->ref_from = col_idx;
    ss->hs->collectables[col_idx].refs_start = ss->hs->num_references;
}

static void run_handler(MVMThreadContext *tc, LocatedHandler lh, MVMObject *ex_obj) {
    switch (lh.handler->action) {
        case MVM_EX_ACTION_GOTO:
            unwind_to_frame(tc, lh.frame);
            *tc->interp_cur_op = *tc->interp_bytecode_start + lh.handler->goto_offset;
            break;
        case MVM_EX_ACTION_INVOKE: {
            /* Create active handler record. */
            MVMActiveHandler *ah = malloc(sizeof(MVMActiveHandler));
            
            /* Find frame to invoke. */
            MVMObject *handler_code = MVM_frame_find_invokee(tc,
                lh.frame->work[lh.handler->block_reg].o);
            
            /* Ensure we have an exception object. */
            /* TODO: Can make one up. */
            if (ex_obj == NULL)
                MVM_panic(1, "Exception object creation NYI");
            
            /* Install active handler record. */
            ah->frame = lh.frame;
            ah->handler = lh.handler;
            ah->ex_obj = ex_obj;
            ah->next_handler = tc->active_handlers;
            tc->active_handlers = ah;
            
            /* Set up special return to unwinding after running the
             * handler. */
            tc->cur_frame->return_value        = NULL;
            tc->cur_frame->return_type         = MVM_RETURN_VOID;
            tc->cur_frame->special_return      = unwind_after_handler;
            tc->cur_frame->special_return_data = ah;
            
            /* Inovke the handler frame and return to runloop. */
            STABLE(handler_code)->invoke(tc, handler_code, &no_arg_callsite,
                tc->cur_frame->args);
            break;
        }
        default:
            MVM_panic(1, "Unimplemented handler action");
    }
}

/* Cleans up an active handler record if we unwind over it. */
static void cleanup_active_handler(MVMThreadContext *tc, void *sr_data) {
    /* Get active handler; sanity check (though it's possible other cases
     * should be supported). */
    MVMActiveHandler *ah = (MVMActiveHandler *)sr_data;
    if (tc->active_handlers != ah)
        MVM_panic(1, "Trying to unwind over wrong handler");

    /* Clean up. */
    tc->active_handlers = ah->next_handler;
    MVM_frame_dec_ref(tc, ah->frame);
    free(ah);
}

static void run_handler(MVMThreadContext *tc, LocatedHandler lh, MVMObject *ex_obj, MVMuint32 category) {
    switch (lh.handler->action) {
    case MVM_EX_ACTION_GOTO:
        if (lh.jit_handler) {
            void **labels = lh.frame->spesh_cand->jitcode->labels;
            MVMuint8  *pc = lh.frame->spesh_cand->jitcode->bytecode;
            lh.frame->jit_entry_label = labels[lh.jit_handler->goto_label];
            MVM_frame_unwind_to(tc, lh.frame, pc, 0, NULL);
        } else {
            MVM_frame_unwind_to(tc, lh.frame, NULL, lh.handler->goto_offset, NULL);
        }
        break;

    case MVM_EX_ACTION_INVOKE: {
        /* Create active handler record. */
        MVMActiveHandler *ah = MVM_malloc(sizeof(MVMActiveHandler));
        MVMFrame *cur_frame = tc->cur_frame;
        MVMObject *handler_code;

        /* Ensure we have an exception object. */
        if (ex_obj == NULL) {
            ex_obj = MVM_repr_alloc_init(tc, tc->instance->boot_types.BOOTException);
            ((MVMException *)ex_obj)->body.category = category;
        }

        /* Find frame to invoke. */
        handler_code = MVM_frame_find_invokee(tc, lh.frame->work[lh.handler->block_reg].o, NULL);

        /* Install active handler record. */
        ah->frame           = MVM_frame_inc_ref(tc, lh.frame);
        ah->handler         = lh.handler;
        ah->jit_handler     = lh.jit_handler;
        ah->ex_obj          = ex_obj;
        ah->next_handler    = tc->active_handlers;
        tc->active_handlers = ah;

        /* Set up special return to unwinding after running the
         * handler. */
        cur_frame->return_value        = (MVMRegister *)&tc->last_handler_result;
        cur_frame->return_type         = MVM_RETURN_OBJ;
        cur_frame->special_return      = unwind_after_handler;
        cur_frame->special_unwind      = cleanup_active_handler;
        cur_frame->special_return_data = ah;

        /* Invoke the handler frame and return to runloop. */
        STABLE(handler_code)->invoke(tc, handler_code, MVM_callsite_get_common(tc, MVM_CALLSITE_ID_NULL_ARGS),
                                     cur_frame->args);
        break;
    }
    default:
        MVM_panic(1, "Unimplemented handler action");
    }
}

/* Takes a pointer to a guard set. Replaces it with a guard set that also
 * includes a guard for the specified type tuple (passed with callsite to
 * know how many types are involved), and resolving to the specified spesh
 * candidate index. Any previous guard set will be scheduled for freeing at
 * the next safepoint. */
void MVM_spesh_arg_guard_add(MVMThreadContext *tc, MVMSpeshArgGuard **orig,
                             MVMCallsite *cs, MVMSpeshStatsType *types,
                             MVMuint32 candidate) {
    MVMSpeshArgGuard *new_guard = copy_and_extend(tc, *orig, max_new_nodes(cs, types));
    if (!try_add_guard(tc, new_guard, cs, types, candidate))
        MVM_panic(1, "Spesh arg guard: trying to add duplicate result for same guard");
    if (*orig) {
        MVMSpeshArgGuard *prev = *orig;
        *orig = new_guard;
        MVM_spesh_arg_guard_destroy(tc, prev, 1);
    }
    else {
        *orig = new_guard;
    }
}

/* Unwinds after a handler. */
void unwind_after_handler(MVMThreadContext *tc, void *sr_data) {
    /* Get active handler; sanity check (though it's possible other cases
     * should be supported). */
    MVMActiveHandler *ah = (MVMActiveHandler *)sr_data;
    if (tc->active_handlers != ah)
        MVM_panic(1, "Trying to unwind from wrong handler");
    tc->active_handlers = ah->next_handler;

    /* Do the unwinding as needed. */
    unwind_to_frame(tc, ah->frame);
    *tc->interp_cur_op = *tc->interp_bytecode_start + ah->handler->goto_offset;

    /* Clean up. */
    free(ah);
}

void MVM_frame_unwind_to(MVMThreadContext *tc, MVMFrame *frame, MVMuint8 *abs_addr,
                         MVMuint32 rel_addr, MVMObject *return_value) {
    while (tc->cur_frame != frame) {
        if (tc->cur_frame->static_info->body.has_exit_handler &&
                !(tc->cur_frame->flags & MVM_FRAME_FLAG_EXIT_HAND_RUN)) {
            /* We're unwinding a frame with an exit handler. Thus we need to
             * pause the unwind, run the exit handler, and keep enough info
             * around in order to finish up the unwind afterwards. */
            MVMFrame     *caller = tc->cur_frame->caller;
            MVMHLLConfig *hll    = MVM_hll_current(tc);
            MVMObject    *handler;

            if (!caller)
                MVM_exception_throw_adhoc(tc, "Entry point frame cannot have an exit handler");
            if (tc->cur_frame == tc->thread_entry_frame)
                MVM_exception_throw_adhoc(tc, "Thread entry point frame cannot have an exit handler");

            MVM_args_setup_thunk(tc, NULL, MVM_RETURN_VOID, &exit_arg_callsite);
            tc->cur_frame->args[0].o = tc->cur_frame->code_ref;
            tc->cur_frame->args[1].o = NULL;
            tc->cur_frame->special_return = continue_unwind;
            {
                MVMUnwindData *ud = malloc(sizeof(MVMUnwindData));
                ud->frame = frame;
                ud->abs_addr = abs_addr;
                ud->rel_addr = rel_addr;
                if (return_value)
                    MVM_exception_throw_adhoc(tc, "return_value + exit_handler case NYI");
                tc->cur_frame->special_return_data = ud;
            }
            tc->cur_frame->flags |= MVM_FRAME_FLAG_EXIT_HAND_RUN;
            handler = MVM_frame_find_invokee(tc, hll->exit_handler, NULL);
            STABLE(handler)->invoke(tc, handler, &exit_arg_callsite, tc->cur_frame->args);
            return;
        }
        else {
            /* No exit handler, so just remove the frame. */
            if (!remove_one_frame(tc, 1))
                MVM_panic(1, "Internal error: Unwound entire stack and missed handler");
        }
    }
    if (abs_addr)
        *tc->interp_cur_op = abs_addr;
    else if (rel_addr)
        *tc->interp_cur_op = *tc->interp_bytecode_start + rel_addr;
    if (return_value)
        MVM_args_set_result_obj(tc, return_value, 1);
}

/* Resolves or inserts a node for testing the curernt type loaded into the
 * test buffer. If it needs to insert a new node, it chains it on to the
 * end of the existing set of type tests. */
static MVMuint32 get_type_check_node(MVMThreadContext *tc, MVMSpeshArgGuard *ag,
                                     MVMuint32 base_node, MVMObject *type, MVMuint8 concrete) {
    MVMuint32 current_node = ag->nodes[base_node].yes;
    MVMuint32 have_fixup_node = 0;
    MVMuint32 fixup_node;
    while (current_node != 0) {
        MVMSpeshArgGuardNode *agn = &(ag->nodes[current_node]);
        if (agn->op == MVM_SPESH_GUARD_OP_STABLE_CONC) {
            /* If it matches, we've found it. */
            if (concrete && agn->st == type->st)
                return current_node;

             /* Otherwise, treat this as the working fixup node, and take
             * the no branch. */
            fixup_node = current_node;
            have_fixup_node = 1;
            current_node = agn->no;
        }
        else if (agn->op == MVM_SPESH_GUARD_OP_STABLE_TYPE) {
            /* If it matches, we've found it. */
            if (!concrete && agn->st == type->st)
                return current_node;

             /* Otherwise, treat this as the working fixup node, and take
             * the no branch. */
            fixup_node = current_node;
            have_fixup_node = 1;
            current_node = agn->no;
        }
        else {
            /* We only expect type matching nodes at the top level. */
            MVM_panic(1, "Spesh arg guard: unexpected type structure in tree");
        }
    }

    /* If we get here, we need to add a node for this callsite. */
    ag->nodes[ag->used_nodes].op = concrete
        ? MVM_SPESH_GUARD_OP_STABLE_CONC
        : MVM_SPESH_GUARD_OP_STABLE_TYPE;
    ag->nodes[ag->used_nodes].st = type->st;
    ag->nodes[ag->used_nodes].yes = 0;
    ag->nodes[ag->used_nodes].no = 0;
    if (have_fixup_node)
        ag->nodes[fixup_node].no = ag->used_nodes;
    else
        ag->nodes[base_node].yes = ag->used_nodes;
    return ag->used_nodes++;
}

/* Called by a thread to indicate it is about to enter a blocking operation.
 * This tells any thread that is coordinating a GC run that this thread will
 * be unable to participate. */
void MVM_gc_mark_thread_blocked(MVMThreadContext *tc) {
    /* This may need more than one attempt. */
    while (1) {
        /* Try to set it from running to unable - the common case. */
        if (MVM_cas(&tc->gc_status, MVMGCStatus_NONE,
                MVMGCStatus_UNABLE) == MVMGCStatus_NONE)
            return;

        /* The only way this can fail is if another thread just decided we're to
         * participate in a GC run. */
        if (MVM_load(&tc->gc_status) == MVMGCStatus_INTERRUPT)
            MVM_gc_enter_from_interrupt(tc);
        else
            MVM_panic(MVM_exitcode_gcorch, "Invalid GC status observed; aborting");
    }
}

/* Searches for a handler of the specified category, relative to the given
 * starting frame, searching according to the chosen mode. */
static LocatedHandler search_for_handler_from(MVMThreadContext *tc, MVMFrame *f,
        MVMuint8 mode, MVMuint32 cat, MVMObject *payload) {
    LocatedHandler lh;
    lh.frame = NULL;
    lh.handler = NULL;
    lh.jit_handler = NULL;
    lh.handler_out_of_dynamic_scope = 0;
    switch (mode) {
        case MVM_EX_THROW_LEX_CALLER:
            f = f->caller;
            while (f && f->static_info->body.is_thunk)
                f = f->caller;
            /* And now we've gone down a caller, it's just lexical... */
        case MVM_EX_THROW_LEX:
            while (f != NULL) {
                if (search_frame_handlers(tc, f, MVM_EX_THROW_LEX, cat, payload, &lh)) {
                    if (in_caller_chain(tc, f))
                        lh.frame = f;
                    else
                        lh.handler_out_of_dynamic_scope = 1;
                    return lh;
                }
                f = f->outer;
            }
            return lh;
        case MVM_EX_THROW_DYN:
            while (f != NULL) {
                if (search_frame_handlers(tc, f, mode, cat, payload, &lh)) {
                    lh.frame = f;
                    return lh;
                }
                f = f->caller;
            }
            return lh;
        case MVM_EX_THROW_LEXOTIC:
            while (f != NULL) {
                lh = search_for_handler_from(tc, f, MVM_EX_THROW_LEX, cat, payload);
                if (lh.frame != NULL)
                    return lh;
                f = f->caller;
            }
            return lh;
        default:
            MVM_panic(1, "Unhandled exception throw mode %d", (int)mode);
    }
}

static void run_gc(MVMThreadContext *tc, MVMuint8 what_to_do) {
    MVMuint8   gen;
    MVMuint32  i, n;

#if MVM_GC_DEBUG
    if (tc->in_spesh)
        MVM_panic(1, "Must not GC when in the specializer/JIT\n");
#endif

    /* Decide nursery or full collection. */
    gen = tc->instance->gc_full_collect ? MVMGCGenerations_Both : MVMGCGenerations_Nursery;

    /* Do GC work for ourselves and any work threads. */
    for (i = 0, n = tc->gc_work_count ; i < n; i++) {
        MVMThreadContext *other = tc->gc_work[i].tc;
        tc->gc_work[i].limit = other->nursery_alloc;
        GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : starting collection for thread %d\n",
            other->thread_id);
        other->gc_promoted_bytes = 0;
        MVM_gc_collect(other, (other == tc ? what_to_do : MVMGCWhatToDo_NoInstance), gen);
    }

    /* Wait for everybody to agree we're done. */
    finish_gc(tc, gen, what_to_do == MVMGCWhatToDo_All);

    /* Now we're all done, it's safe to finalize any objects that need it. */
    /* XXX TODO explore the feasability of doing this in a background
     * finalizer/destructor thread and letting the main thread(s) continue
     * on their merry way(s). */
    for (i = 0, n = tc->gc_work_count ; i < n; i++) {
        MVMThreadContext *other = tc->gc_work[i].tc;

        /* The thread might've been destroyed */
        if (!other)
            continue;

        /* Contribute this thread's promoted bytes. */
        MVM_add(&tc->instance->gc_promoted_bytes_since_last_full, other->gc_promoted_bytes);

        /* Collect nursery. */
        GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
            "Thread %d run %d : collecting nursery uncopied of thread %d\n",
            other->thread_id);
        MVM_gc_collect_free_nursery_uncopied(other, tc->gc_work[i].limit);
    }
}

/* Frame exit handler, used for unwind and normal exit. */
static void log_exit(MVMThreadContext *tc, MVMuint32 unwind) {
    MVMProfileThreadData *ptd = get_thread_data(tc);

    /* Ensure we've a current frame; panic if not. */
    /* XXX in future, don't panic, try to cope. This is for debugging
     * profiler issues. */
    MVMProfileCallNode *pcn = ptd->current_call;
    if (!pcn /*|| !unwind && pcn->sf != tc->cur_frame->static_info*/) {
        MVM_dump_backtrace(tc);
        MVM_panic(1, "Profiler lost sequence");
    }

    /* Add to total time. */
    pcn->total_time += (uv_hrtime() - pcn->cur_entry_time) - pcn->cur_skip_time;

    /* Move back to predecessor in call graph. */
    ptd->current_call = pcn->pred;
}

/* Adds a chunk of work to another thread's in-tray. */
static void push_work_to_thread_in_tray(MVMThreadContext *tc, MVMuint32 target, MVMGCPassedWork *work) {
    MVMint32 j;
    MVMGCPassedWork * volatile *target_tray;

    /* Locate the thread to pass the work to. */
    MVMThreadContext *target_tc = NULL;
    if (target == 0) {
        /* It's going to the main thread. */
        target_tc = tc->instance->main_thread;
    }
    else {
        MVMThread *t = (MVMThread *)MVM_load(&tc->instance->threads);
        do {
            if (t->body.tc->thread_id == target) {
                target_tc = t->body.tc;
                break;
            }
        } while ((t = t->body.next));
        if (!target_tc)
            MVM_panic(MVM_exitcode_gcnursery, "Internal error: invalid thread ID in GC work pass");
    }

    /* push to sent_items list */
    if (tc->gc_sent_items) {
        tc->gc_sent_items->next_by_sender = work;
        work->last_by_sender = tc->gc_sent_items;
    }
    /* queue it up to check if the check list isn't clear */
    if (!MVM_load(&tc->gc_next_to_check)) {
        MVM_store(&tc->gc_next_to_check, work);
    }
    tc->gc_sent_items = work;

    /* Pass the work, chaining any other in-tray entries for the thread
     * after us. */
    target_tray = &target_tc->gc_in_tray;
    while (1) {
        MVMGCPassedWork *orig = *target_tray;
        work->next = orig;
        if (MVM_casptr(target_tray, orig, work) == orig)
            return;
    }
}

/* Adds work to list of items to pass over to another thread, and if we
 * reach the pass threshold then does the passing. */
static void pass_work_item(MVMThreadContext *tc, WorkToPass *wtp, MVMCollectable **item_ptr) {
    ThreadWork *target_info = NULL;
    MVMuint32   target      = (*item_ptr)->owner;
    MVMuint32   j;
    MVMInstance *i          = tc->instance;

    /* Find any existing thread work passing list for the target. */
    if (target == 0)
        MVM_panic(MVM_exitcode_gcnursery, "Internal error: zeroed target thread ID in work pass");
    for (j = 0; j < wtp->num_target_threads; j++) {
        if (wtp->target_work[j].target == target) {
            target_info = &wtp->target_work[j];
            break;
        }
    }

    /* If there's no entry for this target, create one. */
    if (target_info == NULL) {
        wtp->num_target_threads++;
        wtp->target_work = MVM_realloc(wtp->target_work,
            wtp->num_target_threads * sizeof(ThreadWork));
        target_info = &wtp->target_work[wtp->num_target_threads - 1];
        target_info->target = target;
        target_info->work   = NULL;
    }

    /* See if there's a currently active list; create it if not. */
    if (!target_info->work) {
        target_info->work = calloc(sizeof(MVMGCPassedWork), 1);
    }

    /* Add this item to the work list. */
    target_info->work->items[target_info->work->num_items] = item_ptr;
    target_info->work->num_items++;

    /* If we've hit the limit, pass this work to the target thread. */
    if (target_info->work->num_items == MVM_GC_PASS_WORK_SIZE) {
        push_work_to_thread_in_tray(tc, target, target_info->work);
        target_info->work = NULL;
    }
}

static MVMuint32 signal_all_but(MVMThreadContext *tc, MVMThread *t, MVMThread *tail) {
    MVMInstance *ins = tc->instance;
    MVMuint32 i;
    MVMuint32 count = 0;
    MVMThread *next;
    if (!t) {
        return 0;
    }
    do {
        next = t->body.next;
        switch (t->body.stage) {
            case MVM_thread_stage_starting:
            case MVM_thread_stage_waiting:
            case MVM_thread_stage_started:
                if (t->body.tc != tc) {
                    count += signal_one_thread(tc, t->body.tc);
                }
                break;
            case MVM_thread_stage_exited:
                GCORCH_LOG(tc, "Thread %d run %d : queueing to clear nursery of thread %d\n", t->body.tc->thread_id);
                add_work(tc, t->body.tc);
                break;
            case MVM_thread_stage_clearing_nursery:
                GCORCH_LOG(tc, "Thread %d run %d : queueing to destroy thread %d\n", t->body.tc->thread_id);
                /* last GC run for this thread */
                add_work(tc, t->body.tc);
                break;
            case MVM_thread_stage_destroyed:
                GCORCH_LOG(tc, "Thread %d run %d : found a destroyed thread\n");
                /* will be cleaned up (removed from the lists) shortly */
                break;
            default:
                MVM_panic(MVM_exitcode_gcorch, "Corrupted MVMThread or running threads list: invalid thread stage %d", t->body.stage);
        }
    } while (next && (t = next));
    if (tail)
        MVM_WB(tc, t, tail);
    t->body.next = tail;
    return count;
}

/* Called when we take a continuation. Leaves the static frames from the point
 * of view of the profiler, and saves each of them. */
MVMProfileContinuationData * MVM_profile_log_continuation_control(MVMThreadContext *tc, MVMFrame *root_frame) {
    MVMProfileThreadData        *ptd       = get_thread_data(tc);
    MVMProfileContinuationData  *cd        = MVM_malloc(sizeof(MVMProfileContinuationData));
    MVMStaticFrame             **sfs       = NULL;
    MVMuint64                   *modes     = NULL;
    MVMFrame                    *cur_frame = tc->cur_frame;
    MVMuint64                    alloc_sfs = 0;
    MVMuint64                    num_sfs   = 0;
    MVMFrame                   *last_frame;

    do {
        MVMProfileCallNode   *lpcn;
        do {
            MVMProfileCallNode *pcn = ptd->current_call;
            if (!pcn)
                MVM_panic(1, "Profiler lost sequence in continuation control");

            if (num_sfs == alloc_sfs) {
                alloc_sfs += 16;
                sfs        = MVM_realloc(sfs, alloc_sfs * sizeof(MVMStaticFrame *));
                modes      = MVM_realloc(modes, alloc_sfs * sizeof(MVMuint64));
            }
            sfs[num_sfs]   = pcn->sf;
            modes[num_sfs] = pcn->entry_mode;
            num_sfs++;

            lpcn = pcn;
            log_exit(tc, 1);
        } while (lpcn->sf != cur_frame->static_info);

        last_frame = cur_frame;
        cur_frame = cur_frame->caller;
    } while (last_frame != root_frame);

    cd->sfs     = sfs;
    cd->num_sfs = num_sfs;
    cd->modes   = modes;
    return cd;
}