Method dealloc

thread/stack-allocator.cpp:115–127

        return __alloc(slots[idx].slotsize);
    }
    int dealloc(void* ptr, size_t size) {
        auto idx = get_slot(size);
        if (unlikely(idx >= N_SLOTS ||
                     (in_pool_size + slots[idx].slotsize >= trim_threshold))) {
            // big block or in-pool buffers reaches to threshold
            __dealloc(ptr, idx >= N_SLOTS ? size : slots[idx].slotsize);
            return 0;
        }
        // Collect into pool
        in_pool_size += slots[idx].slotsize;
        slots[idx].put(ptr);
        return 0;
    }
    size_t trim(size_t keep_size) {
        size_t count = 0;
        for (int i = 0; in_pool_size > keep_size; i = (i + 1) % N_SLOTS) {