SEGFAULT through nullptr access in object_cache::priv_make_room_for_new_blocks

[liss-h]

In object_cache::priv_make_room_for_new_blocks there is an assertion that the oldest block must not be nullptr

metall/include/metall/kernel/object_cache.hpp

Line 742 in 1f6c027

assert(oldest_block);

.

However, this assertion is not always true which causes a segfault on one of the following lines when oldest_block is accessed.

I have not yet figured out what exactly causes this but maybe you have an idea. I will try to narrow the bug down further and comment on this issue if I find something new.

Stack trace:

[KIwabuchi]

@liss-h Hmm, I'll look into that and get back to you.

[KIwabuchi]

Could you modify Metall's code as follows and run the program again for me?

Insert #define METALL_DISABLE_OBJECT_CACHE to

metall/include/metall/kernel/segment_allocator.hpp

Line 35 in 1f6c027

Insert the code below to

metall/include/metall/kernel/chunk_directory.hpp

Line 212 in 1f6c027

    if (!m_table[chunk_no].slot_occupancy.get(num_slots, slot_no)) {
      logger::out(logger::level::error, __FILE__, __LINE__,
                  "Duplicate deallocation.");
      return;
    }