On Thu, Nov 7, 2024 at 1:46 PM Lauri Vasama wrote:
>
> What if the types remain the same but their meaning changes?
>
> Let's say you have a hash table where the capacity is stored in size_t.
> Later the implementation is changed such that that same size_t stores
> capacity - 1, i.e. a bitmask used for fast modulo when the capacity is
> always a power of two. In this case the hash would not change, but ABI
> compatibility is still broken.


Yeah you're right it wouldn't be 100% reliable, but I think it would
be a great help in debugging modular programs that load in foreign
libraries.

What you've describe in the above though is a conscious ABI break.
Something like "std::layout_of" would be more for unintentional ABI
breaks.