[zeromq-dev] Why has the zeromq soname changed in 3.x and 4.x?

[Dylan Cali]

Hello,

I wanted to confirm that the ABI across zeromq 3 and 4 is compatible
(i.e. new functions were only added, existing function
signatures/semantics have not changed).

If so, I'm curious why the soname major version has been updated,
first from 3 -> 4, and now from 4 -> 5?  I thought soname major
version changes should only be done to signify a new incompatible ABI,
that is either existing signatures have changed, or existing semantics
have changed.

Thanks,
Dylan